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Training brush generator
Training brush generator
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Training brush generator

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This book is for alternator

This book is for alternator

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  • 1. Brush Electrical Machines Ltd. PO Box 18, Loughborough, Leicestershire, LE11 1HJ, England Telephone: +44 (1509) 611511 Telefax: +44 (1509) 610440 E-Mail: sales@bem.fki-et.com Web Site: http://www.fki-et.com/bem TTTrrraaaiiinnniiinnnggg MMMaaannnuuuaaalll SONAHESS PRISMIC PMS SYSTEM 237 (English Version) Manual No: TP00001242 Issue: A Date: January 2008
  • 2. SONAHESS PRISMIC PMS TRAINING MANUAL (English Version) Manual No: TP00001242 Issue: A Date: January 2008 Page: 2 of 5 © Brush Electrical Machines Ltd. 2008 TRAINING MANUAL CONTENTS 1 INTRODUCTION........................................................................................................................................ 3 2 GUIDE TO TRAINING MANUAL ............................................................................................................... 3 3 PROJECT DOCUMENTATION ................................................................................................................. 3 4 TRAINING MODULES ............................................................................................................................... 4
  • 3. SONAHESS PRISMIC PMS TRAINING MANUAL (English Version) Manual No: TP00001242 Issue: A Date: January 2008 Page: 3 of 5 © Brush Electrical Machines Ltd. 2008 1 INTRODUCTION This Training Manual is intended to provide Operators with a understanding of the concepts and procedures used in the design and manufacture of generators and ancillary equipment. In addition to general background information, the Training Manual incorporates details of basic design concepts and project specific information as appropriate. A schedule of the training modules provided, and a summary of their content is given in Section 4. 2 GUIDE TO TRAINING MANUAL Electronic copies of the Training Manual are provided in Adobe Acrobat format (PDF files), which includes bookmarks or links to enable the user to navigate between the various Sections within the manual. To move to the required Section, 'click' on the bookmark in the left hand portion of the screen. 3 PROJECT DOCUMENTATION The Training Manual is designed to supplement the information given in other project documentation i.e.  Operating & Maintenance Manual comprising Installation & Commissioning procedures, Operation & Maintenance procedures, Drawings, Control & Monitoring Equipment and Suppliers Data.  Instruction Manuals/Handbooks for Brush ancillary equipment  Quality Dossier incorporating as shipped equipment settings and, where Brush has an involvement, as commissioned settings.
  • 4. SONAHESS PRISMIC PMS TRAINING MANUAL (English Version) Manual No: TP00001242 Issue: A Date: January 2008 Page: 4 of 5 © Brush Electrical Machines Ltd. 2008 4 TRAINING MODULES 01 GENERAL 01.01.01 Introduction To Brush Electrical Machines Ltd. FKI plc; Brush Electrical Machines History; Brush Electrical Machines 01.02.01 Safety Warning Symbols; Health & Safety At Work Act (1974); Control Of Substances Hazardous To Health (COSHH Regulations 1999); Operation & Maintenance; Protection & Monitoring Devices 01.03.01 Maintenance Philosophies Maintenance; Machine Deterioration; Maintenance Philosophies; Sensory Perception 01.04.01 Principles Of AC Generation Faraday's Law Of Electromagnetic Induction; Three Phase Generation; Generator Excitation Control Systems 04 GENERATOR SYSTEMS 04.01.01 Power Generation Systems Prime Mover/Generator; Generator Operation; Automatic Voltage Control; Parallel Operation; Governor Droop; Generator Output 04.02.01 Generator Synchronising Introduction; DC Generators; AC Generators; Synchronising AC Generators; Lamp Synchronising; Synchroscope; Synchronising At The Switchboard/Control Panel; Automatic Synchronising; Check Synchronising; Closing Onto Dead Busbar 04.03.01 Capability Diagrams Introduction; Stator Current; Power Output; Rotor Current; Stability Of The Rotor; Temporary Limitation; Use Of Capability Diagram; Capability Diagram For Synchronous Motor; Capability Diagram For Synchronous Condenser 04.07.01 Electrical Device Numbers & Functions Introduction; Device Numbers 04.08.01 Equipment & Switchgear Labelling (BS3939) Introduction; General; Prefix Letter; Wire Numbers; Suffix Letters; Numbering Table 04.09.01 High Voltage Phasing Checks Introduction; Phasing Out Of HV Systems; Phasing Sticks 04.10.01 Electrical Power Resistance, Inductance & Capacitance; Current & Voltage; Active Power; Reactive Power; Power Factor & Apparent Power; Three Phase Power, Tariffs & Power Factor Correction. 07.01.03 PRISMIC Power Management System (PMS) Introduction; Applications; Features 07.05.01 Stability Settings Using Keyboard Entry (PRISMIC 'A') Introduction; Active Power Sharing (MW) Commissioning; Reactive Power Sharing (MVAr) Commissioning; Connecting To The Grid Network; After Commissioning 07.06.02 Calibration Procedures (PRISMIC 'B') Introduction; Analogue Cards; Voltage Sensing Unit; Power Measurement System; PRISMIC Calibration On Site; Typical Calibration Problems 07.06.03 Calibration Procedures (PRISMIC PMS) 07.07.01 Set Management Introduction; Starting; Stopping Of Sets; Duty Selection And Hours Run; Fail To Synchronise Alarm; Incorrect Duty Alarm; Minimum Sets To Run; Critical Sets; Large Motor Starting; Split Bus Operation; Grid Tariffs 07.08.02 Load Shedding (HMI Systems) Introduction; Modes Of Operation 07.09.01 Spinning Reserve Introduction; Solid Bus System; Detached System 07.10.01 Data Communications Introduction; Communications - What Is It?; What Is Data Communications; Historical Background; Information Transfer Systems; Telecommunications Systems; Data, Audio & video Communications; Communications Interface; Interface Standards Overview; Smart Instrumentation; Modern Systems
  • 5. SONAHESS PRISMIC PMS TRAINING MANUAL (English Version) Manual No: TP00001242 Issue: A Date: January 2008 Page: 5 of 5 © Brush Electrical Machines Ltd. 2008 07.11.03 Fault Finding - PRISMIC PMS Introduction; Rack And External Input Faults; External Faults; PRISMIC Generated Alarms; Fault Scenarios 07.12.03 System Maintenance - PRISMIC PMS Introduction; General Maintenance; Routine Checks; Calibration Of Generators/Grid Feeders; Calibration Of Load Feeders; Load Inhibits; Spinning Reserve Alarms; Set Management Maintenance, Load Shedding Maintenance; Printers And HMI Systems; Records
  • 6. INTRODUCTION TO BRUSH ELECTRICAL MACHINES LTD. Training Module: 01.01.01 Issue: A Date: September 2002 Page: 1 of 12 01.01.01 (A) Introduction To BEM.doc © Brush Electrical Machines Ltd. 2002 INTRODUCTION TO BRUSH ELECTRICAL MACHINES LTD.
  • 7. INTRODUCTION TO BRUSH ELECTRICAL MACHINES LTD. Training Module: 01.01.01 Issue: A Date: September 2002 Page: 2 of 12 01.01.01 (A) Introduction To BEM.doc © Brush Electrical Machines Ltd. 2002 CONTENTS 1 FKI PLC...................................................................................................................................................... 3 1.1 Introduction.......................................................................................................................................... 3 1.2 FKI Energy Technology....................................................................................................................... 3 1.3 Companies In The FKI Energy Technology Group............................................................................. 4 2 BRUSH ELECTRICAL MACHINES LTD. - HISTORY .............................................................................. 6 2.1 Charles Francis Brush......................................................................................................................... 6 2.2 Development ....................................................................................................................................... 6 2.3 Other Brush Products.......................................................................................................................... 7 2.4 Generators .......................................................................................................................................... 7 2.5 Diversification...................................................................................................................................... 8 2.6 Development ....................................................................................................................................... 8 2.7 Brush Loughborough Site ................................................................................................................... 9 3 BRUSH ELECTRICAL MACHINES LTD................................................................................................. 10 3.1 Introduction........................................................................................................................................ 10 3.2 Products ............................................................................................................................................ 10 3.3 Industries Served .............................................................................................................................. 11 3.4 Quality ............................................................................................................................................... 11 3.5 After-Sales Service & Training.......................................................................................................... 11
  • 8. INTRODUCTION TO BRUSH ELECTRICAL MACHINES LTD. Training Module: 01.01.01 Issue: A Date: September 2002 Page: 3 of 12 01.01.01 (A) Introduction To BEM.doc © Brush Electrical Machines Ltd. 2002 1 FKI PLC 1.1 Introduction FKI plc is a major international engineering group. FKI has world leading positions in its specialised business areas of automated logistic solutions, lifting products and services, hardware and energy technology products. FKI was incorporated on 6 March 1920 in England under the companies Acts 1908 to 1917 and was re-registered on 3 June 1982 as a public limited company under the Companies Acts 1948 to 1980. The Group has operations in more than 30 countries and in the year ended 31 March 2002, its turnover amounted to £1.6 billion, and employs just under 16,000 people. ► 1.2 FKI Energy Technology FKI Electrical Engineering Group was established in 1996 following the acquisition of the Hawker Siddeley Electric Power Group and Marelli Motori. These acquisitions, added to the existing presence of Whipp & Bourne, Laurence Scott & Electromotors and Froude Consine within FKI, made up a Group of world class stature with synergies of technology, manufacturing, purchasing and sales. FKI Electrical Engineering, along with the Measurement and Controls Division, formed FKI plc’s Engineering Group. In July 2001, this became FKI Energy Technology.
  • 9. INTRODUCTION TO BRUSH ELECTRICAL MACHINES LTD. Training Module: 01.01.01 Issue: A Date: September 2002 Page: 4 of 12 01.01.01 (A) Introduction To BEM.doc © Brush Electrical Machines Ltd. 2002 FKI Energy Technology is a leading independent supplier of rotating machines, particularly turbogenerators, switchgear and transformers; measurement and control products and is a significant supplier of other electrical products. Products and systems are sold to manufacturers of turbines, pumps, compressors, fans and other machines and to a wide variety of Customers in industry, power generation, oil and gas supply, air separation, petrochemical and contracting. Main businesses in the FKI Energy Technology group are: Rotating Machines: High, medium and low voltage electric motors; turbo, medium and low voltage generators; industrial drives, control equipment, frequency changers, engine and vehicle test systems. Switchgear: Indoor switchgear, outdoor circuit breakers, ring main units, pole mounted reclosers and DC switchgear. Transformers: Power, system and distribution transformers, pole mounted transformers and on load tap changers. Traction: Rail locomotive manufacture and refurbishment. Measurement and Control : Measurement and control devices and systems. ► 1.3 Companies In The FKI Energy Technology Group Many of the individual companies have histories going back over 100 years. These companies include: Brush Electrical Machines Ltd.: Located at Loughborough in the UK and is designated as FKI's Centre of Excellence for the design and manufacture of power management systems and air cooled 2-pole turbogenerators up to 150MVA. Brush HMA bv: The company, formerly known as 'HMA Power Systems' and before that 'Holec Machines and Apparaten', has been established for over 115 years and became part of FKI Energy Technology at the beginning of 2000. Brush HMA is FKI’s Centre of Excellence for the design and manufacture of 4-pole generators with ratings between 10MVA and 65MVA. Brush SEM sro: Located at Plzen in the Czech Republic and designated as FKI's Centre of Excellence for the design and manufacture of air cooled 2-pole turbogenerators above 150MVA, hydrogen cooled generators and hydrogen/water cooled generators up to 1100MVA and the refurbishment of hydro generators up to 355MVA. Brush Transformers: Based in Loughborough, UK, Brush Transformers is a major international manufacturer of transformers. With over a century of experience, Brush Transformers manufacture a wide range of distribution, power, dry type, cast resin and traction transformers, along with flameproof transformers and switchgear. FKI Industrial Drives: Formed by the merger of Heenan Drives and Brush Industrial Controls, and now provide state of the art variable speed drive products from a new centrally located facility in Loughborough. Products also include AC sensorless flux vector inverters, synchronous motor drives and DC thyristor drives covering a power range from 0.37kW to 20MW. Fully engineered drive systems designed to customer specifications are available.. Hawker Siddeley Power Transformers: Based in Walthamstow, London, Hawker Siddeley Power Transformers is a major international manufacturer of power transformers including generator transformers for steam, hydro, nuclear and gas turbine power stations. Hawker Siddeley Switchgear: Based in Blackwood in South Wales, Hawker Siddeley Switchgear are an international producer of Switchgear. The Blackwood site is a centre of excellence for switchgear manufacture, producing a range of indoor and outdoor distribution switchgear.
  • 10. INTRODUCTION TO BRUSH ELECTRICAL MACHINES LTD. Training Module: 01.01.01 Issue: A Date: September 2002 Page: 5 of 12 01.01.01 (A) Introduction To BEM.doc © Brush Electrical Machines Ltd. 2002 Laurence Scott And Electromotors: Are the UK's premier manufacturer of electric motors (high and low voltage, ac and dc) and electro-mechanical power transmission products (gearboxes, geared motors, eddy current variable speed drives, electro-pneumatic clutch/brakes). Brand names include LSE, NECO, EPG, TASC, NORAC, HEENAN, PSS, GLENPHASE, EDC, SLENDAUR, CENTAUR. Marelli Motori: Produce a range of low and medium voltage asynchronous motors, DC motors and synchronous generators in a large variety of designs and power ranges up to 3,000 kW. The factory is situated in Vicenza in the north of Italy, and has more than one hundred years of experience in the production of rotating electrical machines. South Wales Transformers: Based in Blackwood, South Wales, South Wales Transformers is a major international manufacturer of distribution transformers and substations. The Blackwood site is a centre of excellence for distribution transformer manufacture, producing a wide range of liquid-filled distribution transformers, both pole- and ground-mounted, and packaged substations. Whipp & Bourne: Established in 1903, and based in Rochdale, Lancashire, Whipp and Bourne has long been a leader in heavy duty electrical switchgear. Products include a range of DC Circuit Breakers, Switchgear and Auto Reclosers. ►
  • 11. INTRODUCTION TO BRUSH ELECTRICAL MACHINES LTD. Training Module: 01.01.01 Issue: A Date: September 2002 Page: 6 of 12 01.01.01 (A) Introduction To BEM.doc © Brush Electrical Machines Ltd. 2002 2 BRUSH ELECTRICAL MACHINES LTD. - HISTORY 2.1 Charles Francis Brush Figure 1: Charles Francis Brush The original company was the Anglo-American Brush Electric Light Corporation which was established in 1879 in Lambeth, London, to exploit the inventions of Charles Francis Brush (1849-1929). Brush, born in Cleveland, Ohio, had developed his first dynamo in 1876 and founded the American Brush Company in 1881. This American company lasted until about 1891. ► 2.2 Development Lighting equipment (both arc lamps and incandescent lights) was the main product at first, expanding with the formation of lighting supply companies throughout the country. After an early boom in the promotion of lighting companies, the Electric Lighting Act of 1882 laid down new and onerous conditions of operating so that a general period of stagnation followed in the newly-born electrical industry. However, there were some developments prior to the repeal of the Act in 1888, mainly in the field of industrial electrification. Thus the company was able to thrive on the manufacture of dynamos, motors, switchgear and small transformers. Trade again increased after 1888 and the works in Lambeth were no longer adequate for the vast increase in orders. New premises were required and, in the following year, the Falcon Engine and Car Works in Loughborough was purchased. Figure 2: Brush Works (Early)
  • 12. INTRODUCTION TO BRUSH ELECTRICAL MACHINES LTD. Training Module: 01.01.01 Issue: A Date: September 2002 Page: 7 of 12 01.01.01 (A) Introduction To BEM.doc © Brush Electrical Machines Ltd. 2002 The title of the company was changed soon after the movement to Loughborough. At first, only the heavier manufacturing was transferred from Lambeth, but by 1895 most of the production was concentrated in the Falcon Works which by now incorporated large extensions. ► 2.3 Other Brush Products Figure 3: Brush 'Products' Prior to the First World War, tramcars and electrical engineering were the mainstays of production. The works employed about 2,000 men around 1910. Wartime production was mainly concerned with munitions although vehicle bodies and even aircraft were constructed. ► 2.4 Generators Figure 4: 5000kW Brush-Ljungstrom Turbogenerator
  • 13. INTRODUCTION TO BRUSH ELECTRICAL MACHINES LTD. Training Module: 01.01.01 Issue: A Date: September 2002 Page: 8 of 12 01.01.01 (A) Introduction To BEM.doc © Brush Electrical Machines Ltd. 2002 Electrical equipment sales remained steady during the period after World War 1. Turbine production experienced a great boom after 1918 when some 20 complete turbines with the attendant equipment were delivered each year. The size of these machines was in the 1,500 kW, 3,000 kW and 5,000 kW ranges, and they were well suited to the small municipal and company electricity works then in vogue. ► 2.5 Diversification Employment in the works fell from a peak in 1925 when about 2,500 were employed to 1,500 some ten years later. The area of the works altered little, from 33 acres in 1924 to 35 acres in 1935 when the workshops covered about five acres. The first heavy oil engine made its appearance in 1935 and three years later in an attempt to diversify the range of products and to cater for an increasingly important line of business, the firm of Petters Ltd was taken over. Petters had been established in Yeovil, Somerset since the mid-19th century and had developed their first internal combustion engine in 1895. All the production was transferred to Falcon Works and remained there until 1948 when the former Lagonda Works at Staines, Middlesex were bought. After World War II the demand for heavy electrical equipment, dormant for many years, returned to the company making good the damage of wartime losses, and also encouraging renewal of large-scale capital investment in power generation. The new companies in the Brush Group were now more competitive in modern conditions and the two branches, ABOE (Associated British Oil Engines) and Brush, were complimentary in engine building and electrical equipment. Four-wheeled battery electric vehicles first appeared in 1947 and in the same year the Company returned to railway work after a lapse of many years, when diesel and diesel-electric locomotives were built in conjunction with W.G Bagnall Ltd of Stafford. Further companies joined the Group in 1950 when the National Gas & Oil Engine Company Ltd, Hopkinson Electric Company Ltd and the Vivian Diesels & Munitions Company Ltd of Canada were taken over. The title was changed to the "Brush - ABOE Group of Companies". This was a period of great expansion with a large export drive and increasing capital investment in the industry. The £40 million of orders in 1951 were more than twice those of 1950. ► 2.6 Development In April 1957 an offer of £22 million from the Hawker Siddeley Group was adopted and amalgamation took place. The Brush Group of companies was incorporated into the Hawker Siddeley Group under the name of Brush Electrical Engineering Co., Ltd. and had offices in Dukes Court, Duke Street, St James's, London S.W.1. In November 1991, the Hawker Siddeley Group was taken over by BTR plc in a £1.5 billion bid. In the subsequent re-organisation Brush Electrical Machines Ltd became a major company within the BTR Electric Power Group, and the company's Traction Division became a separate company, Brush Traction Ltd. In November 1996, the FKI Group of Companies acquired the Hawker Siddeley Electric Power Group from BTR, Brush Electrical Machines and the other Brush companies joining the Group's Engineering Division. Following this, Brush Traction Ltd reverted to being a division of Brush Electrical Machines Ltd, and the Company's Industrial Controls Division became part of FKI's LSE Division. Brush Electrical Machines Ltd. is now one of FKI Energy Technology's Rotating Machines companies and is designated as the Centre of Excellence for the design and manufacture manufacture of power management systems and air cooled 2-pole turbogenerators up to 150MVA. Brush BEM joined with sister companies Brush HMA and Brush SEM to found the Brush Turbogenerators organisation. ►
  • 14. INTRODUCTION TO BRUSH ELECTRICAL MACHINES LTD. Training Module: 01.01.01 Issue: A Date: September 2002 Page: 9 of 12 01.01.01 (A) Introduction To BEM.doc © Brush Electrical Machines Ltd. 2002 2.7 Brush Loughborough Site Figure 5: Brush Works, Loughborough In October 1960 the Falcon Works employed about 4,300 workers in the 40 acres of workshops in a total site area of 59 acres. A majority of workers, 3,700, were employed on heavy electrical work whilst 500 were in the Traction Division and 100 on electric vehicle construction. The main production of the works still centred on electrical engineering with heavy transformers, generators, motors, switchgear etc. In 1970 Hawker Siddeley Power Engineering, a project engineering group, was formed as a separate company with an office at a nearby site in Burton-on-the-Wolds and another at Chelmsford in Essex. Twelve months or so later, in 1971, the product divisions of the Brush Electrical Engineering Company Ltd were formed into separate manufacturing companies. Initially these comprised Brush Electrical Machines Limited, Brush Switchgear Ltd and Brush Transformers Limited, with Brush Switchgear taking on the responsibility of the Fusegear Division until January 1973 when Brush Fusegear Ltd was formally constituted. By this time there were approximately 5,000 workers on the Loughborough site. ►
  • 15. INTRODUCTION TO BRUSH ELECTRICAL MACHINES LTD. Training Module: 01.01.01 Issue: A Date: September 2002 Page: 10 of 12 01.01.01 (A) Introduction To BEM.doc © Brush Electrical Machines Ltd. 2002 3 BRUSH ELECTRICAL MACHINES LTD. 3.1 Introduction Figure 6: Brush Electrical Machines Ltd. Logo Brush Electrical Machines Ltd. is now one of FKI Energy Technology's Rotating Machines companies and is designated as the Centre of Excellence for the design and manufacture manufacture of power management systems and air cooled 2-pole turbogenerators up to 150MVA. Brush BEM joined with sister companies Brush HMA and Brush SEM to found the Brush Turbogenerators organisation. Company turnover for the financial year 2001/2002 was approximately £90 million. Over 90% of production was exported. The company employs approximately 770 people, of whom 500 are in production. ► 3.2 Products Our product portfolio, including relevant FKI Energy Technology products, includes: Ø CONTROLS PRISMIC PMS power management systems for marine power and propulsion, offshore and onshore oil and gas applications, industrial and dockland installations. A range of automatic voltage regulators and excitation control equipment for generators and synchronous motors. Ø GENERATORS Air cooled 2-pole turbogenerators for gas and steam turbine drive up to 200MVA, 15kV. Hydrogen and combined cooled 2-pole turbogenerators up to 1100MVA, 25kV. Air cooled 4-pole turbogenerators up to 65MVA, 15kV. Multi-pole synchronous types for diesel engine drive up to 30MVA, 15kV. Ø MOTORS Multi-pole synchronous single, multiple and variable speed types up to 20MW, 15kV. 20-pole induction types up to 20MW, 15kV. LV cage induction types up to 1.5MW. DC types up to 120kW. Traction types up to 1000kW. Flameproof types. Ø SWITCHGEAR Withdrawable/fixed vacuum circuit breakers, rated up to 15kV, 3150A, 40kA. Withdrawable fused vacuum contactors, rated up to 7.2kV, 400A, 40kA. Ø TRANSFORMERS Distribution transformers 315kVA to 2500kVA. Power Transformers 2.5MA to 60MVA up to 145kV. System transformers up to 180MVA, 150kV. Ø VARIABLE SPEED DRIVES AC inverters up to 7MW, 1800V. AC synchroconverters up to 20MW. DC drive systems up to 3.5MW ►
  • 16. INTRODUCTION TO BRUSH ELECTRICAL MACHINES LTD. Training Module: 01.01.01 Issue: A Date: September 2002 Page: 11 of 12 01.01.01 (A) Introduction To BEM.doc © Brush Electrical Machines Ltd. 2002 3.3 Industries Served Brush provides a complete electrical service to all sectors of the power industry. From a product portfolio encompassing generators, including control systems, for base load or intermittent duty, synchronous motors, power management systems and fully co-ordinated packages of electrical equipment. Brush can provide equipment and services to meet the most demanding specifications. Brush is renowned for the kind of robust yet versatile designs of generators and motors well suited to the harsh operating environments encountered at oil and gas installations both onshore and offshore. This has led to Brush gaining an excellent reputation as a world class supplier to this demanding market. Brush also provides a complete electrical service to the marine industry. From generators and control systems, to complete electrical propulsion and auxiliary power system packages for naval, merchant and special purpose vessels. In addition, Brush can select and configure systems built from components sourced from throughout FKI Energy Technology group and elsewhere, including generators, motors, control systems, variable speed drives, switchgear and transformers, etc. ► 3.4 Quality Figure 7: QA Registration Since 1991, the Company has been registered to ISO 9001 standard, which governs the quality of design, manufacture and service. Maintaining this registration has become a cornerstone of management policy. All equipment complies with relevant European, American and International standard specifications. ► 3.5 After-Sales Service & Training A comprehensive service is offered by the Service Department, located at Loughborough, dealing with the commissioning, service, repair and maintenance requirements on a world- wide basis. In addition, service centres in the USA, Malaysia, The Netherlands and Canada, along with local service partners in many other countries, can offer on-the-spot assistance. Comprehensive operator training courses for all products and systems are available either at the factory or at site. ►
  • 17. INTRODUCTION TO BRUSH ELECTRICAL MACHINES LTD. Training Module: 01.01.01 Issue: A Date: September 2002 Page: 12 of 12 01.01.01 (A) Introduction To BEM.doc © Brush Electrical Machines Ltd. 2002 BLANK PAGE
  • 18. SAFETY Training Module: 01.02.01 Issue: A Date: September 2002 Page: 1 of 6 01.02.01 (A) Safety.doc © Brush Electrical Machines Ltd. 2002 SAFETY
  • 19. SAFETY Training Module: 01.02.01 Issue: A Date: September 2002 Page: 2 of 6 01.02.01 (A) Safety.doc © Brush Electrical Machines Ltd. 2002 CONTENTS 1 WARNING SYMBOLS ............................................................................................................................... 3 2 HEALTH & SAFETY AT WORK ACT (1974)............................................................................................ 3 3 CONTROL OF SUBSTANCES HAZARDOUS TO HEALTH (COSHH REGULATIONS 1999)............... 4 3.1 Introduction.......................................................................................................................................... 4 3.2 COSHH Data For Standard Components ........................................................................................... 5 4 OPERATION & MAINTENANCE............................................................................................................... 6 5 PROTECTION AND MONITORING DEVICES.......................................................................................... 6
  • 20. SAFETY Training Module: 01.02.01 Issue: A Date: September 2002 Page: 3 of 6 01.02.01 (A) Safety.doc © Brush Electrical Machines Ltd. 2002 1 WARNING SYMBOLS Warning symbols used in manuals are as follows: Mandatory Notice - Instruction to be followed. Danger, General - Caution to be exercised. Appropriate safety measures to be taken. Danger, Electricity - Caution to be exercised. Appropriate safety measures to be taken. Danger, Harmful or Irritating Substance - Caution to be exercised. Appropriate safety measures to be taken. ► 2 HEALTH & SAFETY AT WORK ACT (1974) The information hereunder is supplied in accordance with Section 6 of the Health and Safety at Work Act 1974 with respect to the duties of manufacturers, designers and installers in providing health and safety information to Customers. The information advises of reasonably foreseeable risks involved with the safe installation, commissioning, operation, maintenance, dismantling, cleaning or repair of products supplied by Brush Electrical Machines Ltd. Every precaution should be taken to minimise risk. When acted upon, the following precautions should considerably minimise the possibility of hazardous incidents. Delivery Checks: Check for damage sustained during transport. Damage to packing cases must be investigated in the presence of an Insurance Surveyor. Handling: Sling packing cases where indicated. Equipment not in a packing case, or removed from a packing case must only be lifted by the lifting points provided. Do not lift complete machines by lugs on heat exchangers or air silencers etc. Storage: Unless the equipment has been designed for outside use or specifically packed for outside storage, store inside in a dry building, in line with the manufacturer's recommendations. Installation: Where installation is made by engineers other than Brush Electrical Machines Ltd. personnel, the equipment should be erected by suitably qualified personnel in accordance with relevant legislation, regulations and accepted rules of the industry. In particular, the recommendations contained in the regulations with regard to the earthing must be rigorously followed. Electrical Installation: IMPROPER USE OF ELECTRICAL EQUIPMENT IS HAZARDOUS. It is important to be aware that control unit terminals and components may be live to line and supply voltages. Before working on a unit, switch off and isolate it and all other equipment within the confines of the same control cubicle. Check that all earth connections are sound. WARNING: Suitable signs should be prominently displayed, particularly on switches and isolators, and the necessary precautions taken to ensure that power is not inadvertently switched on to the equipment whist work is in progress, or is not yet completed.
  • 21. SAFETY Training Module: 01.02.01 Issue: A Date: September 2002 Page: 4 of 6 01.02.01 (A) Safety.doc © Brush Electrical Machines Ltd. 2002 Adjustment and fault finding on live equipment must be by qualified and authorised personnel only, and should be in accordance with the following rules: Ø Read the Instruction Manual. Ø Use insulated meter probes. Ø Use an insulated screwdriver for potentiometer adjustment where a knob is not provided. Ø Wear non-conducting footwear. Ø Do not attempt to modify wiring. Ø Replace all protective covers, guards, etc. on completion. Operation & Maintenance: Engineers responsible for operation and maintenance of equipment should familiarise themselves with the information contained in the Operation & Maintenance Manual and with the recommendations given by manufacturers of associated equipment. They should be familiar also with the relevant regulations in force. Ø It is essential that all covers are in place and that all guards and/or safety fences to protect any exposed surfaces and/or pits are fitted before the machine is started. Ø All adjustments to the machine must be carried out whilst the machine is stationary and isolated from all electrical supplies. Replace all covers and/or safety fences before restarting the machine. Ø When maintenance is being carried out, suitable WARNING signs should be prominently displayed and the necessary precautions taken to ensure power is not inadvertently switched on to the equipment whilst work is in progress, or is not yet complete. Ø When power is restored to the equipment, personnel should not be allowed to work on auxiliary circuits, eg. Heaters, temperature detectors, current transformers etc. Lifting Procedures: Ensure that the recommendations given in the manual are adhered to at all times. ► 3 CONTROL OF SUBSTANCES HAZARDOUS TO HEALTH (COSHH REGULATIONS 1999) 3.1 Introduction The data provided hereafter satisfies the responsibilities detailed in the COSHH Regulations 1999, and includes details of substances commonly used on standard components supplied by Brush Electrical Machines Ltd. This data is not contract specific, and therefore may include substances not used Contract specific information can be obtained from our Service Department. ALWAYS USE SUBSTANCES IN ACCORDANCE WITH MANUFACTURERS' INSTRUCTIONS. IF AFTER APPLYING THE SUGGESTED FIRST AID PROCEDURES, SYMPTOMS PERSIST, SEEK IMMEDIATE ADVICE FROM QUALIFIED MEDICAL STAFF. NEVER INDUCE VOMITTING, OR GIVE ANYTHING BY MOUTH TO AN UNCONSCIOUS PERSON. ►
  • 22. SAFETY Training Module: 01.02.01 Issue: A Date: September 2002 Page: 5 of 6 01.02.01 (A) Safety.doc © Brush Electrical Machines Ltd. 2002 3.2 COSHH Data For Standard Components COSHH data for substances used in standard components supplied by Brush Electrical Machines Ltd. are summarised: PERSONAL PROTECTION/FIRST AIDSUBSTANCE TYPE SUBSTANCE USAGE HEALTH HAZARD DATA EYE CONTACT SKIN CONTACT INHILATION INGESTION DEGREASANT/ CLEANER (Oil Based) Low toxane (highly refined paraffin) or Orange Oil Degreasant/ Cleaner removal of preservative Flash Point > 55 o C. Use good ventilation General care. RINSE WITH FRESH WATER Wear PVC gloves/ barrier creams. RINSE WITH FRESH WATER General care. REMOVE TO FRESH AIR Avoid. DRINK MILK/ WATER. DO NOT VOMIT. CALL DOCTOR DEGREASANT/ CLEANER (Spirit Based) Industrial Meths AEROSOL FORM ONLY Brake disc cleaning only. USE SMALL QUANTITIES EXTREMELY FLAMMABLE Use good ventilation General care. RINSE WITH FRESH WATER Wear PVC gloves/ barrier creams. RINSE WITH FRESH WATER General care. REMOVE TO FRESH AIR Avoid. DRINK MILK/ WATER. DO NOT VOMIT. CALL DOCTOR DO NOT USE: PETROL/GASOLINE, 111 TRICHLORETHANE (GENKLENE) OR CARBON TETRACHLORIDE ADHESIVE/ SEALANT Loctite 542 Loctite 572 Fine thread sealant Pipe sealant (Maintenance Do not inhale vapours. Use adequate ventilation General care. FLUSH WITH WATER FOR 15 MINUTES - CALL DOCTOR General care. WASH WITH SOAP AND WATER General care. REMOVE TO FRESH AIR Avoid. DRINK MILK/ WATER. DO NOT VOMIT DO NOT USE LOCTITE PRODUCTS WITH EXPOSED BROKEN SKIN JOINTING COMPOUND Hylomar PL32 (Medium) Sealant for bearings and other joints Avoid bad ventilation Wear goggles. FLUSH WITH WATER FOR 15 MINUTES Wear PVC gloves. WASH WITH SOAP AND WATER General care. REMOVE TO FRESH AIR - DO NOT EXERCISE Avoid. DRINK MILK/ WATER. DO NOT VOMIT JOINTING COMPOUND Biccon X13 PT Diode mounting paste None Wear goggles. FLUSH WITH WATER Wear PVC gloves. WASH WITH SOAP AND WATER None None JOINTING COMPOUND Unial Electrical joints Avoid open cuts or sores. Wipe with white spirit soaked rag. Rinse with soap and water Wear goggles if contact likely. FLUSH WITH WATER Wear PVC gloves/ barrier creams. RINSE WITH SOAP AND WATER General care. REMOVE TO FRESH AIR Avoid. DRINK WATER. DO NOT VOMIT GREASES Lithium based Mobilplex 48 Castrol Helv.O Silicone based Molybdenum disulphide Diode fixing Use adequate ventilation Wear goggles if contact likely. FLUSH WITH WATER Good hygiene. WASH WITH SOAP AND WATER General care. REMOVE TO FRESH AIR Avoid. DRINK WATER. DO NOT VOMIT MINERAL OILS Mobil DTE oils (All grades - ISO VG Class) Bearing lubrication oil Exposure limit 5.0 mg/m 3 for oil mist None. FLUSH WITH WATER Good hygiene. WASH WITH SOAP AND WATER None with good ventilation. NONE Avoid. IF IN DISCOMFORT CALL DOCTOR INSULATION MATERIALS Epoxy Novolac Corona Paint Glass Cord Synthetic Resin Shellac/Nomex Micanite Insulation materials may be exposed during maintenance/ repair All materials are inert. Physical sanding/ abrasion MAY CREATE HARMFUL DUST Wear goggles. FLUSH WITH WATER Good hygiene. WASH WITH SOAP AND WATER Wear disposable dust respirators 3M type 8709. REMOVE TO FRESH AIR General care. DRINK WATER. DO NOT VOMIT FILLER Epoxy resin putty Armature coil gap fill repair only Dry sanding of epoxy paints and fillers containing chromates. WILL CREATE HARMFUL DUST Wear goggles. FLUSH WITH WATER Wear vinyl gloves/ barrier creams - good hygiene. WASH WITH SOAP AND WATER No risks with good ventilation. Is sanding wear Racal Breathe Easy unit with toxic dist cartridge REMOVE TO FRESH AIR Avoid. DRINK WATER DO NOT VOMIT PAINT MATERIALS Dry paint finishes Surface finish/ protection may be exposed during repair Dry sanding of epoxy paints and fillers containing chromates. WILL CREATE HARMFUL DUST Wear goggles. FLUSH WITH WATER Good hygiene. WASH WITH SOAP AND WATER Wear Racal Breathe Easy unit with toxic dist cartridge REMOVE TO FRESH AIR General care. DRINK WATER. DO NOT VOMIT AIR CONTAMINANT Airborne dust particles Cooling air circuit filters (Maintenance) During maintenance a dust hazard may exist Wear goggles. FLUSH WITH WATER Good hygiene. WASH WITH SOAP AND WATER Wear disposable dust respirators 3M type 8709. REMOVE TO FRESH AIR General care. DRINK WATER. DO NOT VOMIT ►
  • 23. SAFETY Training Module: 01.02.01 Issue: A Date: September 2002 Page: 6 of 6 01.02.01 (A) Safety.doc © Brush Electrical Machines Ltd. 2002 4 OPERATION & MAINTENANCE When working on this equipment it is important that a safe environment is achieved i.e. Ø Isolate all electrical supplies including heaters. Ø Ensure adequate ventilation and lighting. Ø Use proper support for heavy items. Ø Maintain access ways. Ø Wear suitable protective clothing. Safety guards and covers must be fitted, unless the equipment has been made safe behind the guard or cover. On-site safety procedures are to be followed as appropriate, in particular 'Permit To Work' type systems are be followed rigorously. Attention should be given to the advice given in Clause 2 (Health & Safety At Work Act (1974)) and Clause 3 (Control Of Substances Hazardous to Health (COSHH Regulations 1999)) Details of substances used on equipment that are potentially hazardous to health are detailed in Clause 3.2 and the Suppliers Data that forms part of the Operation & Maintenance Manual. IMPROPER USE OF ELECTRICAL EQUIPMENT IS HAZARDOUS. ► 5 PROTECTION AND MONITORING DEVICES WARNING: It is essential that any protection or monitoring device for use with generators or ancillary equipment should be connected and operational at all times unless specifically stated otherwise. It should not be assumed that all necessary protection and monitoring devices are supplied as part of Brush Electrical Machines Ltd. scope of supply. Unless otherwise agreed, it is the responsibility of others to verify the correct operation of all protection and monitoring equipment, whether supplied by Brush Electrical Machines Ltd. or not. It is necessary to provide a secure environment that ensures operator safety and limits potential damage to the generator and ancillary equipment. If requested, Brush Electrical Machines Ltd. would be pleased to provide advice on any specific protection application issues or concerns. ►
  • 24. SAFETY Training Module: 01.02.01 Issue: A Date: September 2002 Page: 1 of 6 01.02.01 (A) Safety.doc © Brush Electrical Machines Ltd. 2002 SAFETY
  • 25. SAFETY Training Module: 01.02.01 Issue: A Date: September 2002 Page: 2 of 6 01.02.01 (A) Safety.doc © Brush Electrical Machines Ltd. 2002 CONTENTS 1 WARNING SYMBOLS ............................................................................................................................... 3 2 HEALTH & SAFETY AT WORK ACT (1974)............................................................................................ 3 3 CONTROL OF SUBSTANCES HAZARDOUS TO HEALTH (COSHH REGULATIONS 1999)............... 4 3.1 Introduction.......................................................................................................................................... 4 3.2 COSHH Data For Standard Components ........................................................................................... 5 4 OPERATION & MAINTENANCE............................................................................................................... 6 5 PROTECTION AND MONITORING DEVICES.......................................................................................... 6
  • 26. SAFETY Training Module: 01.02.01 Issue: A Date: September 2002 Page: 3 of 6 01.02.01 (A) Safety.doc © Brush Electrical Machines Ltd. 2002 1 WARNING SYMBOLS Warning symbols used in manuals are as follows: Mandatory Notice - Instruction to be followed. Danger, General - Caution to be exercised. Appropriate safety measures to be taken. Danger, Electricity - Caution to be exercised. Appropriate safety measures to be taken. Danger, Harmful or Irritating Substance - Caution to be exercised. Appropriate safety measures to be taken. ► 2 HEALTH & SAFETY AT WORK ACT (1974) The information hereunder is supplied in accordance with Section 6 of the Health and Safety at Work Act 1974 with respect to the duties of manufacturers, designers and installers in providing health and safety information to Customers. The information advises of reasonably foreseeable risks involved with the safe installation, commissioning, operation, maintenance, dismantling, cleaning or repair of products supplied by Brush Electrical Machines Ltd. Every precaution should be taken to minimise risk. When acted upon, the following precautions should considerably minimise the possibility of hazardous incidents. Delivery Checks: Check for damage sustained during transport. Damage to packing cases must be investigated in the presence of an Insurance Surveyor. Handling: Sling packing cases where indicated. Equipment not in a packing case, or removed from a packing case must only be lifted by the lifting points provided. Do not lift complete machines by lugs on heat exchangers or air silencers etc. Storage: Unless the equipment has been designed for outside use or specifically packed for outside storage, store inside in a dry building, in line with the manufacturer's recommendations. Installation: Where installation is made by engineers other than Brush Electrical Machines Ltd. personnel, the equipment should be erected by suitably qualified personnel in accordance with relevant legislation, regulations and accepted rules of the industry. In particular, the recommendations contained in the regulations with regard to the earthing must be rigorously followed. Electrical Installation: IMPROPER USE OF ELECTRICAL EQUIPMENT IS HAZARDOUS. It is important to be aware that control unit terminals and components may be live to line and supply voltages. Before working on a unit, switch off and isolate it and all other equipment within the confines of the same control cubicle. Check that all earth connections are sound. WARNING: Suitable signs should be prominently displayed, particularly on switches and isolators, and the necessary precautions taken to ensure that power is not inadvertently switched on to the equipment whist work is in progress, or is not yet completed.
  • 27. SAFETY Training Module: 01.02.01 Issue: A Date: September 2002 Page: 4 of 6 01.02.01 (A) Safety.doc © Brush Electrical Machines Ltd. 2002 Adjustment and fault finding on live equipment must be by qualified and authorised personnel only, and should be in accordance with the following rules: Ø Read the Instruction Manual. Ø Use insulated meter probes. Ø Use an insulated screwdriver for potentiometer adjustment where a knob is not provided. Ø Wear non-conducting footwear. Ø Do not attempt to modify wiring. Ø Replace all protective covers, guards, etc. on completion. Operation & Maintenance: Engineers responsible for operation and maintenance of equipment should familiarise themselves with the information contained in the Operation & Maintenance Manual and with the recommendations given by manufacturers of associated equipment. They should be familiar also with the relevant regulations in force. Ø It is essential that all covers are in place and that all guards and/or safety fences to protect any exposed surfaces and/or pits are fitted before the machine is started. Ø All adjustments to the machine must be carried out whilst the machine is stationary and isolated from all electrical supplies. Replace all covers and/or safety fences before restarting the machine. Ø When maintenance is being carried out, suitable WARNING signs should be prominently displayed and the necessary precautions taken to ensure power is not inadvertently switched on to the equipment whilst work is in progress, or is not yet complete. Ø When power is restored to the equipment, personnel should not be allowed to work on auxiliary circuits, eg. Heaters, temperature detectors, current transformers etc. Lifting Procedures: Ensure that the recommendations given in the manual are adhered to at all times. ► 3 CONTROL OF SUBSTANCES HAZARDOUS TO HEALTH (COSHH REGULATIONS 1999) 3.1 Introduction The data provided hereafter satisfies the responsibilities detailed in the COSHH Regulations 1999, and includes details of substances commonly used on standard components supplied by Brush Electrical Machines Ltd. This data is not contract specific, and therefore may include substances not used Contract specific information can be obtained from our Service Department. ALWAYS USE SUBSTANCES IN ACCORDANCE WITH MANUFACTURERS' INSTRUCTIONS. IF AFTER APPLYING THE SUGGESTED FIRST AID PROCEDURES, SYMPTOMS PERSIST, SEEK IMMEDIATE ADVICE FROM QUALIFIED MEDICAL STAFF. NEVER INDUCE VOMITTING, OR GIVE ANYTHING BY MOUTH TO AN UNCONSCIOUS PERSON. ►
  • 28. SAFETY Training Module: 01.02.01 Issue: A Date: September 2002 Page: 5 of 6 01.02.01 (A) Safety.doc © Brush Electrical Machines Ltd. 2002 3.2 COSHH Data For Standard Components COSHH data for substances used in standard components supplied by Brush Electrical Machines Ltd. are summarised: PERSONAL PROTECTION/FIRST AIDSUBSTANCE TYPE SUBSTANCE USAGE HEALTH HAZARD DATA EYE CONTACT SKIN CONTACT INHILATION INGESTION DEGREASANT/ CLEANER (Oil Based) Low toxane (highly refined paraffin) or Orange Oil Degreasant/ Cleaner removal of preservative Flash Point > 55 o C. Use good ventilation General care. RINSE WITH FRESH WATER Wear PVC gloves/ barrier creams. RINSE WITH FRESH WATER General care. REMOVE TO FRESH AIR Avoid. DRINK MILK/ WATER. DO NOT VOMIT. CALL DOCTOR DEGREASANT/ CLEANER (Spirit Based) Industrial Meths AEROSOL FORM ONLY Brake disc cleaning only. USE SMALL QUANTITIES EXTREMELY FLAMMABLE Use good ventilation General care. RINSE WITH FRESH WATER Wear PVC gloves/ barrier creams. RINSE WITH FRESH WATER General care. REMOVE TO FRESH AIR Avoid. DRINK MILK/ WATER. DO NOT VOMIT. CALL DOCTOR DO NOT USE: PETROL/GASOLINE, 111 TRICHLORETHANE (GENKLENE) OR CARBON TETRACHLORIDE ADHESIVE/ SEALANT Loctite 542 Loctite 572 Fine thread sealant Pipe sealant (Maintenance Do not inhale vapours. Use adequate ventilation General care. FLUSH WITH WATER FOR 15 MINUTES - CALL DOCTOR General care. WASH WITH SOAP AND WATER General care. REMOVE TO FRESH AIR Avoid. DRINK MILK/ WATER. DO NOT VOMIT DO NOT USE LOCTITE PRODUCTS WITH EXPOSED BROKEN SKIN JOINTING COMPOUND Hylomar PL32 (Medium) Sealant for bearings and other joints Avoid bad ventilation Wear goggles. FLUSH WITH WATER FOR 15 MINUTES Wear PVC gloves. WASH WITH SOAP AND WATER General care. REMOVE TO FRESH AIR - DO NOT EXERCISE Avoid. DRINK MILK/ WATER. DO NOT VOMIT JOINTING COMPOUND Biccon X13 PT Diode mounting paste None Wear goggles. FLUSH WITH WATER Wear PVC gloves. WASH WITH SOAP AND WATER None None JOINTING COMPOUND Unial Electrical joints Avoid open cuts or sores. Wipe with white spirit soaked rag. Rinse with soap and water Wear goggles if contact likely. FLUSH WITH WATER Wear PVC gloves/ barrier creams. RINSE WITH SOAP AND WATER General care. REMOVE TO FRESH AIR Avoid. DRINK WATER. DO NOT VOMIT GREASES Lithium based Mobilplex 48 Castrol Helv.O Silicone based Molybdenum disulphide Diode fixing Use adequate ventilation Wear goggles if contact likely. FLUSH WITH WATER Good hygiene. WASH WITH SOAP AND WATER General care. REMOVE TO FRESH AIR Avoid. DRINK WATER. DO NOT VOMIT MINERAL OILS Mobil DTE oils (All grades - ISO VG Class) Bearing lubrication oil Exposure limit 5.0 mg/m 3 for oil mist None. FLUSH WITH WATER Good hygiene. WASH WITH SOAP AND WATER None with good ventilation. NONE Avoid. IF IN DISCOMFORT CALL DOCTOR INSULATION MATERIALS Epoxy Novolac Corona Paint Glass Cord Synthetic Resin Shellac/Nomex Micanite Insulation materials may be exposed during maintenance/ repair All materials are inert. Physical sanding/ abrasion MAY CREATE HARMFUL DUST Wear goggles. FLUSH WITH WATER Good hygiene. WASH WITH SOAP AND WATER Wear disposable dust respirators 3M type 8709. REMOVE TO FRESH AIR General care. DRINK WATER. DO NOT VOMIT FILLER Epoxy resin putty Armature coil gap fill repair only Dry sanding of epoxy paints and fillers containing chromates. WILL CREATE HARMFUL DUST Wear goggles. FLUSH WITH WATER Wear vinyl gloves/ barrier creams - good hygiene. WASH WITH SOAP AND WATER No risks with good ventilation. Is sanding wear Racal Breathe Easy unit with toxic dist cartridge REMOVE TO FRESH AIR Avoid. DRINK WATER DO NOT VOMIT PAINT MATERIALS Dry paint finishes Surface finish/ protection may be exposed during repair Dry sanding of epoxy paints and fillers containing chromates. WILL CREATE HARMFUL DUST Wear goggles. FLUSH WITH WATER Good hygiene. WASH WITH SOAP AND WATER Wear Racal Breathe Easy unit with toxic dist cartridge REMOVE TO FRESH AIR General care. DRINK WATER. DO NOT VOMIT AIR CONTAMINANT Airborne dust particles Cooling air circuit filters (Maintenance) During maintenance a dust hazard may exist Wear goggles. FLUSH WITH WATER Good hygiene. WASH WITH SOAP AND WATER Wear disposable dust respirators 3M type 8709. REMOVE TO FRESH AIR General care. DRINK WATER. DO NOT VOMIT ►
  • 29. SAFETY Training Module: 01.02.01 Issue: A Date: September 2002 Page: 6 of 6 01.02.01 (A) Safety.doc © Brush Electrical Machines Ltd. 2002 4 OPERATION & MAINTENANCE When working on this equipment it is important that a safe environment is achieved i.e. Ø Isolate all electrical supplies including heaters. Ø Ensure adequate ventilation and lighting. Ø Use proper support for heavy items. Ø Maintain access ways. Ø Wear suitable protective clothing. Safety guards and covers must be fitted, unless the equipment has been made safe behind the guard or cover. On-site safety procedures are to be followed as appropriate, in particular 'Permit To Work' type systems are be followed rigorously. Attention should be given to the advice given in Clause 2 (Health & Safety At Work Act (1974)) and Clause 3 (Control Of Substances Hazardous to Health (COSHH Regulations 1999)) Details of substances used on equipment that are potentially hazardous to health are detailed in Clause 3.2 and the Suppliers Data that forms part of the Operation & Maintenance Manual. IMPROPER USE OF ELECTRICAL EQUIPMENT IS HAZARDOUS. ► 5 PROTECTION AND MONITORING DEVICES WARNING: It is essential that any protection or monitoring device for use with generators or ancillary equipment should be connected and operational at all times unless specifically stated otherwise. It should not be assumed that all necessary protection and monitoring devices are supplied as part of Brush Electrical Machines Ltd. scope of supply. Unless otherwise agreed, it is the responsibility of others to verify the correct operation of all protection and monitoring equipment, whether supplied by Brush Electrical Machines Ltd. or not. It is necessary to provide a secure environment that ensures operator safety and limits potential damage to the generator and ancillary equipment. If requested, Brush Electrical Machines Ltd. would be pleased to provide advice on any specific protection application issues or concerns. ►
  • 30. GENERATOR MAINTENANCE PHILOSOPHIES Training Module: 01.03.01 Issue: A Date: September 2002 Page: 1 of 4 01.03.01 (A) Generator Maintenance Philosophies.doc © Brush Electrical Machines Ltd. 2002 GENERATOR MAINTENANCE PHILOSOPHIES
  • 31. GENERATOR MAINTENANCE PHILOSOPHIES Training Module: 01.03.01 Issue: A Date: September 2002 Page: 2 of 4 01.03.01 (A) Generator Maintenance Philosophies.doc © Brush Electrical Machines Ltd. 2002 CONTENTS 1 MAINTENANCE......................................................................................................................................... 3 2 MACHINE DETERIORATION.................................................................................................................... 3 3 MAINTENANCE PHILOSOPHIES............................................................................................................. 3 3.1 Curative Maintenance ......................................................................................................................... 3 3.2 Preventive Maintenance...................................................................................................................... 4 3.2.1 Time-Based Maintenance............................................................................................................ 4 3.2.2 Condition-Based Maintenance..................................................................................................... 4 4 SENSORY PERCEPTION ......................................................................................................................... 4
  • 32. GENERATOR MAINTENANCE PHILOSOPHIES Training Module: 01.03.01 Issue: A Date: September 2002 Page: 3 of 4 01.03.01 (A) Generator Maintenance Philosophies.doc © Brush Electrical Machines Ltd. 2002 1 MAINTENANCE The term maintenance can be applied to a broad range of activities. In general, maintenance includes all activities necessary to enable the safe and efficient functioning of a machine or system, throughout its working life. Maintenance can be said to encompass the following activities: 1) Maintain Proper Condition Prevent the malfunction of the machine or system. 2) Judge The Current Condition Obtain information of the actual condition of the machine or system. 3) Recondition To The Original Condition Maintenance must be performed to repair a fault. Recommendations for the implementation of these activities are detailed in the Operating & Maintenance Manual, but the actual maintenance programme should be determined by the end user (or his representative) in order to reflect local site conditions e.g. operating regime, site location, operation & maintenance staff skills and availability, etc. ► 2 MACHINE DETERIORATION The factors that cause machine deterioration include: Ø When Running Ø Outgoing Load Ø Thermal Load Ø Internal Magnetic Load Ø Internal Mechanical Load, including imbalance or misalignment. Ø External Mechanical Factors, including forces exerted by the prime mover, and external vibrations. Ø Ambient Conditions, including dust, water, corrosive atmospheres Ø At Standstill Ø External Mechanical Factors, including external vibrations. Ø Ambient Conditions, including dust, water, corrosive atmospheres From the above it can be concluded that the machine is 'subject to wear and tear' during its entire life, irrespective of the number of hours run. Any machine will therefore need to undergo a maintenance inspection or check from time to time. The purpose of this inspection is to detect possible abnormalities that, sooner or later, may disrupt its operation, or in the case of a breakdown, determine the extent of the damage. ► 3 MAINTENANCE PHILOSOPHIES The availability of a machine has a direct influence on the wellbeing of a company. An unexpected breakdown can cause considerable inconvenience and financial loss. To keep a machine functioning efficiently throughout its working life can often cost more than the original cost of the machine itself, consequently the way in which maintenance is carried out is important. The objective is high reliability with minimum interruption of machine operation, with minimum outlay. There are two basic maintenance philosophies that can be adopted: ► 3.1 Curative Maintenance With curative maintenance (or run-to-breakdown maintenance) a major overhaul is only performed after a breakdown. Overhauls cannot be planned and interruptions in operation occur unexpectedly. This policy is thus only appropriate when the machine’s condition is likely to deteriorate abruptly, which is not usually the case with electrical machines. Certain components can, of course, always breakdown suddenly. ►
  • 33. GENERATOR MAINTENANCE PHILOSOPHIES Training Module: 01.03.01 Issue: A Date: September 2002 Page: 4 of 4 01.03.01 (A) Generator Maintenance Philosophies.doc © Brush Electrical Machines Ltd. 2002 3.2 Preventive Maintenance With preventive maintenance, overhauls are planned ahead and take place in time to prevent a breakdown. This means that the machine’s condition should only be expected to deteriorate in a steady and predictable manner. For instance, the longer the machine is in operation the more likely the chance of a breakdown. In practice, particularly for electrical machines, preventive maintenance is preferred because it is more likely to ensure dependable plant operation. Preventive maintenance can be divided into two sub-categories, but in practice a combination of the two philosophies is used: 3.2.1 Time-Based Maintenance With time-based maintenance the machine is overhauled on the basis of calendar time and/or hours of operation e.g. once a month, year, etc. or every so many hours. In most cases this is acceptable, however there is the disadvantage that some components will be replaced before the are completely worn out. For example, the bearing would still be functioning correctly. 3.2.2 Condition-Based Maintenance With condition-based maintenance, the time when preventive action must be undertaken is determined by the machine’s condition. The assessment of the machine’s condition must be carried out by means of monitoring equipment and skilled engineers who know how to interpret the measurements. ► 4 SENSORY PERCEPTION Sensory perception means: Ø Looking Ø Touching Ø Smelling Ø Listening Sensory perception plays an important part in maintenance, since it is often possible to detect abnormal behaviour or an abnormal situation at an early stage, without the use of any measuring equipment. ►
  • 34. PRINCIPLES OF AC GENERATION Training Module: 01.04.01 Issue: A Date: September 2002 Page: 1 of 10 01.04.01 (A) Principles Of AC Generation.doc © Brush Electrical Machines Ltd. 2002 PRINCIPLES OF AC GENERATION
  • 35. PRINCIPLES OF AC GENERATION Training Module: 01.04.01 Issue: A Date: September 2002 Page: 2 of 10 01.04.01 (A) Principles Of AC Generation.doc © Brush Electrical Machines Ltd. 2002 CONTENTS 1 FARADAY'S LAW OF ELECTROMAGNETIC INDUCTION..................................................................... 3 2 THREE PHASE GENERATION................................................................................................................. 7 3 GENERATOR EXCITATION CONTROL SYSTEMS ................................................................................ 8 3.1 Conventional Excitation System (DC Generator Commutator Exciter)............................................... 8 3.2 Static Excitation System...................................................................................................................... 8 3.3 Brushless Excitation System............................................................................................................... 9
  • 36. PRINCIPLES OF AC GENERATION Training Module: 01.04.01 Issue: A Date: September 2002 Page: 3 of 10 01.04.01 (A) Principles Of AC Generation.doc © Brush Electrical Machines Ltd. 2002 1 FARADAY'S LAW OF ELECTROMAGNETIC INDUCTION Figure 1: Electromagnetic Induction Faraday's Law Of Electromagnetic Induction, illustrated in Figure 1, states that, if a conductor is moved in a magnetic field, then an electromotive force (emf) - or simply, a voltage - is induced in that conductor. It follows that, if the ends of the conductor are connected to an external load, then an electric current, driven by that voltage, will flow from the conductor, through the load and back again. Faraday showed that if a wire moves in a magnetic field, an artificial charge, or voltage, will be created in that wire. Faraday also showed that the magnitude of the voltage induced in the moving conductor depends on the strength of the magnetic field and the speed of movement, and on nothing else. These two laws form the whole basis of electrical power generation, both AC and DC. ► Fleming's Right Hand Rule for generators determines how this is achieved. Figure 2 illustrates the relationship between the magnetic field (North to South), direction of motion and direction of emf (voltage) induced in the conductor. Figure 2: Fleming's Right Hand Rule ►
  • 37. PRINCIPLES OF AC GENERATION Training Module: 01.04.01 Issue: A Date: September 2002 Page: 4 of 10 01.04.01 (A) Principles Of AC Generation.doc © Brush Electrical Machines Ltd. 2002 Figure 3 shows a loop of stiff wire on a shaft which can be turned. Suppose each end of the wire is connected to a slipring, insulated from the shaft, upon which there are brushes that are connected to a load. Figure 3: AC Generation - Fixed Field As the shaft is turned, one bar passes the N-pole as the other passes the S-pole. Voltage is induced one way in one bar and the opposite way in the other. ► Figure 4 illustrates how an alternating current waveform (sine wave) is induced in the rotating coil as it passes the fixed magnetic field. Figure 4: Alternating Current ►
  • 38. PRINCIPLES OF AC GENERATION Training Module: 01.04.01 Issue: A Date: September 2002 Page: 5 of 10 01.04.01 (A) Principles Of AC Generation.doc © Brush Electrical Machines Ltd. 2002 Faraday's theory required only that the conductor should be moving through a magnetic field i.e. that there should be relative motion between conductor and field. It would work just as well if the magnetic field moved past the conductor. In the arrangement shown in Figure 5 this is just what's happening. Figure 5: Rotating Field (Permanent Magnet) In the above diagram, the stiff wire loop is fixed, and the permanent magnet is rotated past it and inside it. As a pole passes a fixed conductor a maximum voltage is induced in it, opposite voltages on opposite sides, and they add up to give double voltage at the terminals or at the voltmeter.. In this arrangement no sliprings or brushes are needed which would be advantageous for a number of reasons, not least the reduced maintenance requirement. ►
  • 39. PRINCIPLES OF AC GENERATION Training Module: 01.04.01 Issue: A Date: September 2002 Page: 6 of 10 01.04.01 (A) Principles Of AC Generation.doc © Brush Electrical Machines Ltd. 2002 So far only permanent magnets have been considered for producing the magnetic field. Far better results can be achieved by using an electromagnet, which can produce much stronger fields and therefore much higher induced voltages (See Figure 6). Figure 6: Rotating Field (Electromagnet) In this case however DC power must be provided to the coil which magnetises it. This can come from a battery or other DC source, but a pair of sliprings and brushes must be used to bring the battery current to the moving magnetising coil - called the 'field coil'. This coil is said to 'excite' the field and the whole process is called 'excitation'. Because the field magnet is not permanent but is an electromagnet, it is possible to vary the coil current by a resistance and so vary the strength of the magnetic field itself. This in turn will vary the amount of the induced voltage. ► Using this principle, it is possible for an Operator to control the machine's voltage (remotely) by varying the excitation. This is illustrated in the following diagram. Figure 7: Voltage Control ►
  • 40. PRINCIPLES OF AC GENERATION Training Module: 01.04.01 Issue: A Date: September 2002 Page: 7 of 10 01.04.01 (A) Principles Of AC Generation.doc © Brush Electrical Machines Ltd. 2002 2 THREE PHASE GENERATION Figure 8: Three Phase Generation - Windings ► The above diagram illustrates how the basic AC generator principles are applied to produce the three phase generation waveforms shown in Figure 9. Figure 9: Three Phase Generation - Waveforms ►
  • 41. PRINCIPLES OF AC GENERATION Training Module: 01.04.01 Issue: A Date: September 2002 Page: 8 of 10 01.04.01 (A) Principles Of AC Generation.doc © Brush Electrical Machines Ltd. 2002 3 GENERATOR EXCITATION CONTROL SYSTEMS Figure 7 showed how it would be possible (for an Operator) to control the main machine's voltage by adjustment of the resistance which in turn varies the excitation i.e. If the Operator knows the voltage he wants to see on a voltmeter connected to the generator output, he can adjust the resistance until the required value is achieved. This is called 'excitation control'. To make the process automatic, an electronic device called an Automatic Voltage Regulator (AVR) or Excitation Controller is used to sense the output voltage and compare it with a datum which has previously been set by hand. The AVR decides whether the output voltage is correct, too high or too low. There commonly used types of excitation control systems for ac generators output control are: 3.1 Conventional Excitation System (DC Generator Commutator Exciter) GENERATOR DC Exciter AVR Sensing Only Figure 10: Excitation System - Conventional In this system, a dc control signal is fed from the excitation control to the stationary field of the dc exciter. The rotating element of the exciter then supplies a direct current to the field winding of the main ac generator. The rotating armature of the dc exciter is either driven from the same shaft as the rotating main field of the generator, or can be on a separate motor driven shaft. In both cases, a dc commutator is required on the exciter, and brushes and sliprings (collector rings) are required on the rotating generator field to carry the main generator field current. This system is sometimes used on smaller or older machines. ► 3.2 Static Excitation System GENERATOR AVR Sensing And Power Static Exciter Figure 11: Static Excitation System
  • 42. PRINCIPLES OF AC GENERATION Training Module: 01.04.01 Issue: A Date: September 2002 Page: 9 of 10 01.04.01 (A) Principles Of AC Generation.doc © Brush Electrical Machines Ltd. 2002 Static excitation systems obtain power from the electrical output of the generator or from the connected system to feed rectifiers in the regulating system, which in turn supply direct current to the main field winding of the generator through brushes and sliprings. ► 3.3 Brushless Excitation System Brush generators are now almost exclusively fitted with 'brushless' excitation systems in which the exciter shares a common shaft thus doing away with the need for sliprings and brushes. Since a DC generator used as an exciter would require the brushgear to rotate, the main exciter is another, but smaller, AC generator with stationary field and rotating armature. The AC output from this armature is taken converted to DC through 'rectifiers' rotating with the shaft, and then fed to the rotating field winding of the main generator. AVR Main AC Exciter Rotating Rectifier Generator Sensing And Power Figure 12: Brushless Excitation System In this system the ac armature of the exciter, the rotating three phase diode bridge rectifier, and the main field of the ac generator are all mounted on the same rotating shaft system. All electrical connections are made along or through the centre of the shaft. ► It is common to add a small second, or 'pilot' exciter (or permanent magnet generator - PMG) to excite the main exciter. AVR Main AC Exciter Rotating Rectifier Generator Voltage Sensing OnlyPilot Exciter Power Figure 13: Brushless Excitation System With Pilot Exciter ►
  • 43. PRINCIPLES OF AC GENERATION Training Module: 01.04.01 Issue: A Date: September 2002 Page: 10 of 10 01.04.01 (A) Principles Of AC Generation.doc © Brush Electrical Machines Ltd. 2002 AVR Main AC Exciter Rotating Rectifier Generator Power And Voltage Sensing Short-Circuit Current Transformers Figure 14: Brushless Excitation System (Without Pilot Exciter) Some Customers prefer a brushless excitation system that does not use a pilot exciter. This arrangement is illustrated in the above diagram. ►
  • 44. POWER GENERATION SYSTEMS Training Module: 04.01.01 Issue: B Date: April 2003 Page: 1 of 14 04.01.01 (B) Power Generation Systems.doc © Brush Electrical Machines Ltd. 2003 POWER GENERATION SYSTEMS DCAC AVR SENSING VT CT ROTOR STATOR PMG EXCITER ROTATING RECTIFIER LOAD PRIME MOVER
  • 45. POWER GENERATION SYSTEMS Training Module: 04.01.01 Issue: B Date: April 2003 Page: 2 of 14 04.01.01 (B) Power Generation Systems.doc © Brush Electrical Machines Ltd. 2003 CONTENTS 1 PRIME MOVER/GENERATOR.................................................................................................................. 3 1.1 Arrangement........................................................................................................................................ 3 1.2 Prime Mover & Governor .................................................................................................................... 3 1.3 Generator & AVR ................................................................................................................................ 4 2 GENERATOR OPERATION ...................................................................................................................... 5 2.1 General................................................................................................................................................ 5 2.2 Island Operation.................................................................................................................................. 5 2.3 Parallel Operation................................................................................................................................ 6 3 AUTOMATIC VOLTAGE CONTROL......................................................................................................... 7 4 PARALLEL OPERATION.......................................................................................................................... 8 4.1 Quadrature Current Compensation..................................................................................................... 8 4.2 Machines In Parallel.......................................................................................................................... 10 5 GOVERNOR DROOP .............................................................................................................................. 11 5.1 Introduction........................................................................................................................................ 11 5.2 Case 1 - Zero Droop (Isochronous) .................................................................................................. 12 5.3 Case 2 - With Droop.......................................................................................................................... 12 6 GENERATOR OUTPUT........................................................................................................................... 13
  • 46. POWER GENERATION SYSTEMS Training Module: 04.01.01 Issue: B Date: April 2003 Page: 3 of 14 04.01.01 (B) Power Generation Systems.doc © Brush Electrical Machines Ltd. 2003 1 PRIME MOVER/GENERATOR 1.1 Arrangement Figure 1: Main Components Of A Generating Package 1.2 Prime Mover & Governor The prime mover is mechanically linked, or coupled, to the generator either directly or by a gearbox. It would typically be a turbine (gas, steam, water or wind) or a diesel engine. Its function is to rotate the generator. As the generator is usually a synchronous machine, the rotational speed is required to be kept fairly constant and this is the function of the governor. Modern governors are normally electronic, providing a fast, closed loop control but the output may take many forms to suit the prime mover being controlled. The governor output can be a fuel, water or gas valve; being opened to increase speed or closed to reduce it. Some form of speed signal is fed to the governor and compared with an adjustable reference. The difference, the error, is used to control the output. The speed to which the governor controls, the speed datum, is adjustable over a small range; the adjustment usually being made by means of a ‘speeder motor’ in the case of mechanical governors or by an up/down counter in electronic units. The raise/lower signals might come from a control switch, an automatic synchroniser or an automatic control system. ►
  • 47. POWER GENERATION SYSTEMS Training Module: 04.01.01 Issue: B Date: April 2003 Page: 4 of 14 04.01.01 (B) Power Generation Systems.doc © Brush Electrical Machines Ltd. 2003 1.3 Generator & AVR The Generator converts rotational mechanical energy produced by the prime mover into electrical energy. Figure 2 illustrates how the various elements are connected to a brushless generator AVR system. DCAC AVR SENSING VT CT ROTOR STATOR PMG EXCITER ROTATING RECTIFIER LOAD PRIME MOVER Figure 2: Generator/AVR Block Diagram The purpose of the pilot exciter is to provide a source of excitation power whenever the machine is running. The pilot exciter is a single phase permanent magnet generator (PMG), with the magnets mounted on the shaft, and the AC output being generated in the stator. The main exciter is of the brushless type and comprises a fixed part called the main exciter stator, and a rotating part called the main exciter armature. The main exciter stator is comprises laminated steel field poles around which are the field coils. ► The three phase AC output from the main exciter armature is connected to the rotating rectifier assembly, which converts the AC output to the DC input required in the generator rotor winding (See Figure 3) . The rotating rectifier assembly is a three phase full wave bridge configuration, with fuses in series with each rectifier diode. On larger machines more than one fuse/rectifier diode may be fitted to each arm of the bridge. Electrical connections between the rectified output and the generator rotor winding are carried in the central bore through the machine shaft.
  • 48. POWER GENERATION SYSTEMS Training Module: 04.01.01 Issue: B Date: April 2003 Page: 5 of 14 04.01.01 (B) Power Generation Systems.doc © Brush Electrical Machines Ltd. 2003 Exciter Field Winding Exciter Armature Winding Generator Stator Winding Negative Heat Sink Positive Heat Sink Silicon Diode Fuse GeneratorFieldWinding Rectifier Assembly Rotor Figure 3: Brushless Generator Schematic The voltage regulator allows the Operator to control the generator's voltage by variation of excitation. This is called 'excitation control'. To make the process automatic, an electronic device called an Automatic Voltage Regulator (AVR) or Excitation Controller is used to sense the output voltage and compare it with a preset datum. The AVR decides whether the output voltage is correct, too high or too low. The power output of the machine is produced in the generator stator windings. ► 2 GENERATOR OPERATION 2.1 General The power (MW, kW, W or Watts) supplied at the generator terminals is provided by the fuel supplied to the prime mover (turbine or engine), which is determined by the prime mover governor. When a generator is used to supply power, it can be operated isolated, sometimes referred to as island mode, or in parallel with a system or other machines. 2.2 Island Operation In island operation, the machine speed is determined by the load and fuel supply, and the generator voltage is determined by the excitation. Because the unit operates in isolation, the generator power factor is equal to the load power factor.
  • 49. POWER GENERATION SYSTEMS Training Module: 04.01.01 Issue: B Date: April 2003 Page: 6 of 14 04.01.01 (B) Power Generation Systems.doc © Brush Electrical Machines Ltd. 2003 FUEL REGULATOR PRIME MOVER MECHANICAL POWER FUEL GENERATOR ELECTRICAL POWER GOVERNOR SPEED SIGNAL FIELD VOLTAGE SIGNAL LOAD VOLTAGE REGULATOR Figure 4: Island Mode Operation When operating in isolation, an increase in load will have two effects: 1) Speed will initially fall because the energy being supplied by the fuel is less than that required by the load. The speed reduction is detected by the governor, which opens the prime mover fuel valve by the required amount to maintain the required speed. 2) Voltage will initially fall because the generator excitation is too low to maintain nominal voltage at the increased load. The voltage reduction is detected by the automatic voltage regulator (AVR) which increases the excitation by an amount required to maintain output voltage. ► 2.3 Parallel Operation FUEL REGULATOR PRIME MOVER MECHANICAL POWER FUEL GENERATOR ELECTRICAL POWER GOVERNOR SPEED SIGNAL FIELD LARGE POWER SYSTEM VOLTAGE REGULATOR V I SENSING SIGNALS Figure 5: Parallel Operation When a machine operates in parallel with a power system, the voltage and frequency will be fixed mainly by the system. The fuel supply to the prime mover determines the power which is supplied by the generator and this is controlled by the governor. The generator excitation determines the internal emf of the machine and therefore affects the power factor when the terminal voltage is fixed by the power system. The governor and AVR are arranged to have characteristics which allow them to be stable when the generator is operating in parallel with a power system. (See Section 4 - Parallel Operation).
  • 50. POWER GENERATION SYSTEMS Training Module: 04.01.01 Issue: B Date: April 2003 Page: 7 of 14 04.01.01 (B) Power Generation Systems.doc © Brush Electrical Machines Ltd. 2003 In single and parallel operation it is important to realise that power is determined by the fuel supply to the prime mover, and that excitation determines voltage when single running, and power factor when parallel running. ► 3 AUTOMATIC VOLTAGE CONTROL PILOT EXCITER BRUSHLESS GENERATOR VOLTAGE & CURRENT SENSING TRANSFORMERS EXCITER FIELD CONTROLLED RECTIFIER CONTROL SIGNAL AMPLIFIER ERROR SIGNAL ADJUSTABLE REFERENCE VOLTAGE SENSING SIGNAL STABILISING NETWORK Figure 6: Principal Components Of A Generator And AVR The above diagram shows the principal components of the generator and its AVR. The voltage transformer (VT) provides a signal proportional to line voltage to the AVR where it is compared to a stable reference voltage. The difference (error) signal is amplified and then used to control the output of a thyristor rectifier which supplies a portion of the PMG output to the exciter field. If the load on the generator suddenly increases the reduction in output voltage produces an error signal which, when amplified, causes an increase in exciter field current resulting in a corresponding increase in rotor current and generator output voltage. Conversely, load reduction will cause the generator voltage to suddenly increase, and in this case the amplified error signal will cause a reduction in exciter field current resulting in a corresponding reduction in rotor current and generator output voltage. Because of the high inductance of the generator field windings, it is difficult to make rapid changes in field current. This introduces a considerable 'lag' in the control system which makes it necessary to include a stabilising circuit in the AVR to prevent instability and optimise the generator voltage response to load changes. Without a stabilising circuit, the regulator would keep increasing and reducing excitation and the line voltage would continuously fluctuate above and below the required value. Modern voltage regulators are designed to maintain the generator line voltage within better than ±1% of nominal for wide variations of machine load. ►
  • 51. POWER GENERATION SYSTEMS Training Module: 04.01.01 Issue: B Date: April 2003 Page: 8 of 14 04.01.01 (B) Power Generation Systems.doc © Brush Electrical Machines Ltd. 2003 4 PARALLEL OPERATION 4.1 Quadrature Current Compensation As mentioned earlier when a generator is connected in parallel with another power system it may be incapable of significantly influencing the system line voltage, with the level of excitation now determining the reactive power developed by the generator. If line voltage were less than that called for by the voltage regulator, it would supply maximum available excitation in an attempt to increase line voltage and excessive lagging reactive line current would flow. Similarly, if line voltage were high, excitation would be reduced to zero in an attempt to reduce line voltage, and excessive leading line current would flow. Under such circumstances the generator could pole slip (run asynchronously) if any significant power were flowing. A standard method of overcoming the above problem is to modify the voltage control system so that as lagging reactive load on the generator increases, the line voltage that the regulator demands is reduced as shown in Figure 7 in which it will be seen that as the system voltage falls from level A to level B the lagging reactive current increases. For a fixed line voltage,, generator reactive current may be varied by adjustment of the voltage setting potentiometer which adjusts the position of the AVR characteristic. AVR CHARACTERISTIC GENERATOR LINE VOLTAGE A & B REPRESENT TWO SYSTEM VOLTAGES A B LEADING LAGGING REACTIVE CURRENT 0 Figure 7: Voltage Control Characteristic For Parallel Operation A method of achieving the above AVR characteristic is known as Quadrature Current Compensation (QCC). A voltage proportional to one line current is added to the voltage across the other two lines and the amplitude of the vector sum is regulated by the AVR as illustrated in the following diagram. ►
  • 52. POWER GENERATION SYSTEMS Training Module: 04.01.01 Issue: B Date: April 2003 Page: 9 of 14 04.01.01 (B) Power Generation Systems.doc © Brush Electrical Machines Ltd. 2003 AVR V I SCHEMATIC DIAGRAM V A B C 1 C VECTOR DIAGRAMS φ φ I I I A C B A C B V V VAB C 1 Figure 8: Quadrature Current Compensation It will be seen that the sensing voltage, V1, is the vector sum of line voltage and a voltage proportional to the line current signal, VC. If line voltage is much greater than VC, the following approximation way be made. V1 = VBA + VC sin φ where φ is the phase angle. Thus as lagging reactive load increases, so does the last term of the above expression which is proportional to reactive current, and therefore line voltage is reduced as the AVR acts to maintain V1 constant. For leading reactive currents, line voltage is increased. The reduction in line voltage for rated current at zero power factor lagging is typically 5%. Provided line voltage does not vary, reactive current will be controlled to a level determined by the voltage setting potentiometer of the AVR. If, however, line voltage varied appreciably, an Operator would have to continually adjust the potentiometer to prevent excessive lagging or leading currents. Under such circumstances it may be desirable to use an automatic reactive current or power factor control system. ►
  • 53. POWER GENERATION SYSTEMS Training Module: 04.01.01 Issue: B Date: April 2003 Page: 10 of 14 04.01.01 (B) Power Generation Systems.doc © Brush Electrical Machines Ltd. 2003 4.2 Machines In Parallel Where a number of machines are operated in parallel, it is usual to adjust the regulators to give a similar amount of droop. This will ensure that the total VAR loading on the system remains reasonably balanced between generators. If droop settings are not equal, the machine with the least droop will tend to take more than its share of the load VARs. This means that the set with least droop will run at a lower lagging power factor than the others. LOAD A B C TOTAL VARS (SET BY LOAD) A & B HAVE EQUAL DROOP C HAS LESS DROOP THAN A& B VOLTAGE LEAD 0 LAG VARsVARs On A & B VARs On C A & B C SYSTEM VOLTAGE Figure 9: Three Machines In Parallel On Independent Load In the above diagram, machines A and B have identical droop and at a particular line voltage will supply equal VARs. Machine C has less droop and will therefore supply more VARs than A or B, at the same line voltage. When a machine operates in parallel with an infinite busbar as shown in the following diagram, the busbar behaves like a machine with zero droop, therefore if the busbar voltage remains constant, the generator will produce constant VARs. ►
  • 54. POWER GENERATION SYSTEMS Training Module: 04.01.01 Issue: B Date: April 2003 Page: 11 of 14 04.01.01 (B) Power Generation Systems.doc © Brush Electrical Machines Ltd. 2003 A INFINITE BUSBAR GENERATOR VOLTAGE LEAD 0 LAG VARs Y SYSTEM VOLTAGE X X' Y' CHARACTERISTIC OF MACHINE A INCREASING AVR SET POINT Figure 10: Machine In Parallel With Infinite Busbar To adjust the VARs on the machine it is necessary to raise or lower the position of line X-Y by adjusting the AVR datum. This is the usual method of manually adjusting VARs or Power Factor. ► 5 GOVERNOR DROOP 5.1 Introduction When operating in parallel the prime mover fuel control system is also changed from a constant frequency control system to one which can operate when the frequency is determined by the grid system. A simple arrangement often used is known as governor droop where the governor speed datum is reduced as the load increases. SPEED (FREQUENCY) POWER Y SYSTEM FREQUENCY Y Y' Y' INCREASING GOVERNOR SET POINT 0 100% Figure 11: Governor Droop Characteristic In this simple arrangement the system frequency determines the point on the characteristic, and adjustment of the governor datum will raise or lower the line Y-Y and allow the load to be adjusted. As in generator controls, wide variations of system frequency would give rise to large power variation and in such cases it would be normal to include an automatic load control system in the governor. ►
  • 55. POWER GENERATION SYSTEMS Training Module: 04.01.01 Issue: B Date: April 2003 Page: 12 of 14 04.01.01 (B) Power Generation Systems.doc © Brush Electrical Machines Ltd. 2003 5.2 Case 1 - Zero Droop (Isochronous) To explain the need for speed droop consider firstly the case of two generating packages without droop. These are required to run in parallel on an ‘Island’ system such as an isolated oil rig. Consider Package A, set to 50Hz, already on the bars and loaded to about half full load - no problem here. If the load should vary, the governor will adjust the fuel to bring the speed back to 50Hz. Now if Package B was needed, it would be synchronised to the bars usually by setting it a little faster, say 50.1Hz. Once the breaker is closed, the two sets are locked together and the troubles begin. The common speed of the two packages is likely to be somewhere between 50 and 50.1Hz. The governor on Package B will see this speed as too slow and increase the fuel supply. At the same time Package A’s governor will see the speed as too fast and reduce fuel. Neither of these actions change the situation and the governors continue to fight, Package B will take all the available load and Package A will trip on reverse power. ► 5.3 Case 2 - With Droop Now consider what happens when this is repeated but with the governor of Package B having droop. As before, Package B’s governor sees the speed as too low and increases fuel and again Package A’s fuel is reduced, but, as the power provided by B increases so its speed setting is reduced automatically by the droop mechanism and soon falls to 50Hz at which point both governors are happy. The governor of Package A with zero droop is said to be ‘isochronous’. Figure 12 shows the characteristics of two such packages, one with droop and one isochronous. Figure 12: Isochronous/Droop Characteristics If further sets are needed on the bars then they too must have speed droop. Just one set may be left in the isochronous mode and this set then effectively controls the frequency of the whole power system. Such an arrangement may seem ideal but, apart from the difficulty of ensuring that one, and only one of the sets is isochronous, there is another problem: any load change is thrown solely onto the isochronous set. It is more common to give all sets equal droop and in this way any load changes are shared equally between the running sets. The slight reduction in frequency as load is applied is a small penalty to pay for an inherently stable arrangement. In any case, a power management system such as PRISMIC will off-set this and keep the system frequency constant in the long term. ►
  • 56. POWER GENERATION SYSTEMS Training Module: 04.01.01 Issue: B Date: April 2003 Page: 13 of 14 04.01.01 (B) Power Generation Systems.doc © Brush Electrical Machines Ltd. 2003 6 GENERATOR OUTPUT The generator is usually the only load driven by the prime mover and this produces a three phase output at a voltage to suit the distribution arrangement of the power system. Typical nominal voltages are 600V, 3300V, 6600V, 11,000V or 13,800V. The design of the generator determines the voltage it can produce, but merely spinning the machine will only generate about 5% nominal volts (produced by the residual magnetism of the rotor). To produce full voltage the generator has to be excited. In the case of a brushless generator this is done by applying a DC voltage to the exciter field. The control of the generator output voltage by this means is the job of the automatic voltage regulator (AVR). The task of any AVR is to maintain the generator voltage at a set level. A dip in voltage caused by an increased load on the machine will be compensated by increasing the voltage applied to the field. Modern AVRs employ semi-conductor devices to provide excitation and offer a fast response to maintain line voltage in the face of varying loads. Like the governor, the AVR has a droop characteristic but, in this case, it is the voltage that falls and with increasing reactive rather than real power (See Training Module 04.10.01). The voltage droop is can be set between 0 and 10%, a value of 4% being common. The droop allows the generator to share reactive power stably with other paralleled machines. The generator is selected to match the speed and power of the prime mover; the output frequency is given by the following formula: f= N x p where: f is the generator frequency N is generator speed in revs per second p is the number of pairs of poles on the generator Thus a four-pole generator running at 1500 rpm (25 revs/second) will give a frequency of 50Hz. ►
  • 57. POWER GENERATION SYSTEMS Training Module: 04.01.01 Issue: B Date: April 2003 Page: 14 of 14 04.01.01 (B) Power Generation Systems.doc © Brush Electrical Machines Ltd. 2003 BLANK PAGE
  • 58. SYNCHRONISING Training Module: 04.02.01 Issue: A Date: April 2003 Page: 1 of 10 04.02.01 (A) Synchronising.doc © Brush Electrical Machines Ltd. 2003 SYNCHRONISING
  • 59. SYNCHRONISING Training Module: 04.02.01 Issue: A Date: April 2003 Page: 2 of 10 04.02.01 (A) Synchronising.doc © Brush Electrical Machines Ltd. 2003 CONTENTS 1 INTRODUCTION........................................................................................................................................ 3 2 DC GENERATORS.................................................................................................................................... 3 3 AC GENERATORS.................................................................................................................................... 4 4 SYNCHRONISING AC GENERATORS .................................................................................................... 5 5 LAMP SYNCHRONISING.......................................................................................................................... 6 5.1 The 2-Lamp Method............................................................................................................................ 6 5.2 The 3-Lamp Method............................................................................................................................ 7 6 SYNCHROSCOPE..................................................................................................................................... 8 7 SYNCHRONISING AT THE SWITCHBOARD/CONTROL PANEL .......................................................... 8 8 AUTOMATIC SYNCHRONISING .............................................................................................................. 9 9 CHECK SYNCHRONISING ....................................................................................................................... 9 10 CLOSING ONTO DEAD BUSBAR ...................................................................................................... 10
  • 60. SYNCHRONISING Training Module: 04.02.01 Issue: A Date: April 2003 Page: 3 of 10 04.02.01 (A) Synchronising.doc © Brush Electrical Machines Ltd. 2003 1 INTRODUCTION The idea of synchronising is not new. Every time you change gear in a car you synchronise the engine to the road speed so that, when the clutch is let in, both shafts are running at the same speed and there is no jerk. Conversely, if you synchronise badly there is a jerk, stress on the engine and possibly a lot of noise. In electrical engineering, synchronising is to either electrically 'join' the output of an AC generator to a live busbar, or join live bus sections together. Generator synchronising is applicable to installations that have more than one generator and/or are connected to another (external) network or grid. When synchronising two electrical systems, the moment the circuit breaker closes the systems are mechanically locked through the busbars. Any synchronising displacement will cause the smaller of the systems to lock very quickly resulting in mechanical stresses in the both the prime mover and generator rotors and foundations. In turbines blades can be damaged. In generators windings and rotating diodes can be damaged due to the high transient currents that can occur during this 'fault' condition. ► 2 DC GENERATORS The simplest case of synchronising occurs with dc generators. Figure 1: DC Generators Figure 1 represents two dc generators, both on open circuit but about to be paralleled by a switch. Each is separately excited such that machine 'A' has an open-circuit voltage VA and machine 'B' VB. Machine 'A' is assumed to be the 'running' generator, and machine 'B' , is the 'incoming' generator which is to be paralleled to 'A'. Before closing the switch which puts the two generators in parallel it is necessary only to ensure that their voltages are the same -that is, that VB = VA ; then the switch may be closed, and no sudden current will flow - there will be no electrical 'jerks'. If the voltages were different, suppose that VA is greater than VB. On closing the switch there will be a closed loop with the emf's VA and VB opposing one another. Since VA is greater than VB there is a net clockwise emf in the loop, which will cause a clockwise current IC to flow round it (shown in red), limited only by the resistances of the two armatures. This current appears suddenly as the switch is closed, putting a sudden load onto generator 'A' so causing it to slow with a jerk, and causing generator 'B' to motor, making it accelerate with a jerk. This circulating current, which occurs on closing the switch whenever VA and VB are not equal, is also called the 'synchronising current'. To avoid it and its consequent jerking effect on the system, the incoming machine voltage must first be matched to the voltage of the running machine - normally done by trimming the field of the incoming generator. ►
  • 61. SYNCHRONISING Training Module: 04.02.01 Issue: A Date: April 2003 Page: 4 of 10 04.02.01 (A) Synchronising.doc © Brush Electrical Machines Ltd. 2003 3 AC GENERATORS With ac generators the problem is more complicated. It can be seen in the dc case how a circulating current is caused by differing opposing voltages. In dc this is straightforward, but in ac a voltage difference can be caused either by differing voltage amplitudes or, for the same voltage amplitudes, by differing phase. Figure 2: Voltage And Phase Difference In Figure 2(a) the two voltages VA and VB are in phase with one another, but their amplitudes are different. At any instant such as time T, the instantaneous voltage of machine 'A' is TA and that of machine 'B' is TB. Therefore there is, at that instant, a voltage difference AB which will cause a circulating current to flow between the generators when the paralleling switch is closed. This is true at any instant other than a common voltage zero. In Figure 2(b) the two voltages have equal amplitudes but are displaced in phase, VB lagging on VA .At any instant such as time T the instantaneous voltage of machine 'A' is TA and that of machine 'B' is TB. Although the two voltages are equal in amplitude, there is still an instantaneous difference of voltage AB which will cause a circulating current to flow between the generators when the paralleling switch is closed. Therefore, even though the voltage levels (as read by voltmeters) are the same, a difference of phase will still cause a circulating, or 'synchronising', current to flow between the machines, causing one to accelerate and the other to decelerate and to jerk them into phase with each other as the switch is closed. Therefore, to prevent sudden circulating currents occurring and to achieve smooth paralleling, the voltages of both machines must first be equalised and the machines then brought into phase. This is described in the following section.
  • 62. SYNCHRONISING Training Module: 04.02.01 Issue: A Date: April 2003 Page: 5 of 10 04.02.01 (A) Synchronising.doc © Brush Electrical Machines Ltd. 2003 There is one further requirement. As when changing gear in a car, the two generator speeds must also be equalised before paralleling. If this is not done, the faster machine will be jerked back and the slower jerked forward, which could cause serious mechanical problems in large machines, as well as to the couplings, gear trains and prime movers. If the two machines are running at different speeds before paralleling, this will show as different frequencies on the frequency meters. Therefore a preliminary to synchronising is to equalise as nearly as possible not only the machine voltages but also their frequencies, using the switchboard voltmeters and frequency meters. The following conditions must be equal before closing the circuit breaker: Ø Voltage Ø Frequency Ø Phase Ø Phase Rotation In some situations it may be preferable to have the generator being synchronised running sllghtly fast (super-synchronous) at the moment of circuit breaker closure so that power flows from the prime mover into the busbars. Conversely, it may be preferable to have the generator being synchronised running sllghtly slow (sub- synchronous) at the moment of circuit breaker closure so that power flows from the busbars into the prime mover. This may however cause the generator 'reverse power' protection system to operate. ► 4 SYNCHRONISING AC GENERATORS It is assumed that one machine' A ' (the 'running' generator) is already in service on the busbars and is on load, and that a second machine 'B' (the 'incoming' generator) has been started and run up and is ready to be put in parallel with 'A' in order to share its load. Before this can be done the incoming generator 'B' must be synchronised with the running machine 'A'. As already described, the first step is to match the incoming to the running voltage by reference to the voltmeters on the two generator control boards, and by using the incoming voltage regulator to trim it. Similarly the incoming frequency is matched to the running frequency by reference to the two frequency meters and by trimming the incoming speed regulator. Note that the running machine controls should not be touched - the incoming machine is always matched to the running, not vice versa. It now remains to bring the generators into phase. Even after matching the frequencies by meter, the speeds will still not be exactly equal, and one machine will be slowly overtaking the other. As this occurs, their phase relationship will be steadily, but slowly, changing. The idea is to make this take place as slowly as possible and, as they momentarily pass through the 'in-phase' state, to catch them at that point, to close the paralleling switch and to lock them there. There are two ways in which the correct phase may be detected - the first is by lamps, and the other is by an instrument called a synchroscope. ►
  • 63. SYNCHRONISING Training Module: 04.02.01 Issue: A Date: April 2003 Page: 6 of 10 04.02.01 (A) Synchronising.doc © Brush Electrical Machines Ltd. 2003 5 LAMP SYNCHRONISING 5.1 The 2-Lamp Method Figure 3: Lamp Synchronising (2-Lamp Method) Synchronising by lamps makes use of the circuit shown in Figure 3; two lamps in series are connected across the same phase of each generator. Only when the two systems are in phase is the voltage across the lamps continuously zero, and both lamps are out. At all other times there is a voltage difference, and the lamps glow. This is known as the 'lamps dark' method of synchronising. The voltage phase vectors of both generators are shown. Machine No 1 is the 'running' and its vectors are in full line. Machine No 2 is the 'incoming' and its vectors are dotted. It is approaching synchronism with No 1. When the machine frequencies are nearly equal, the lamps are switched on and alternately glow and go out, giving a slow flashing appearance. The nearer the frequencies are to being equal, the slower the lamp flashing period. Therefore to achieve phase matching, the incoming machine's speed is slowly trimmed until the lamps are flashing very slowly; then, as they are changing from bright to dark, the operator places his hand over the breaker control button or handle and, at the moment when the lamps go completely out, operates it to close the breaker. The lamps then stay out, but they should be switched off after completing the synchronising.
  • 64. SYNCHRONISING Training Module: 04.02.01 Issue: A Date: April 2003 Page: 7 of 10 04.02.01 (A) Synchronising.doc © Brush Electrical Machines Ltd. 2003 Note: The lamps could be connected to burn at their brightest, instead of being dark, when the systems are in phase, but this 'lamps bright' method is seldom used today. It is easier to detect the exact point of 'no light' in a lamp than to estimate when it is at its brightest. The 'lamps dark' method is almost universally found. It is necessary to use two lamps in series because, when the systems are fully out of phase (lamps at brightest), the voltage difference is then double the system phase voltage. ► 5.2 The 3-Lamp Method Figure 4: Lamp Synchronising (3-Lamp Method) An alternative method, known as '3-lamp synchronising' can also be used. It is shown in Figure 4. The three lamps are connected as shown: No.1 (yellow-to-yellow)I No.2 (blue-to-red) and No.3 (red-to-blue). In the centre diagram the full lines refer to generator 'A' (R1, Y1 and B1), and the dotted lines to generator 'B' (R2, Y2 and B2). Machine 'B' is shown approaching synchronism with machine' A '. With the lamps so connected, the voltage across No.1 lamp (Y1 - Y2) is small, and the lamp glows dimly. The voltages across No.2 and No.3 lamps (B1 - R2 and R1 - B2) are large, and both lamps are bright. As synchronism is reached (left-hand of the three lowest diagrams) No.1 lamp goes out and the other two have equal brightness. When the two generators are 120 o out of synchronism (centre of the three diagrams) it can be seen that it is No.2 lamp (B1 - R2) which has no voltage and goes out. 120 o later (right hand diagram) No.3 lamp (R1 - B2) goes out.
  • 65. SYNCHRONISING Training Module: 04.02.01 Issue: A Date: April 2003 Page: 8 of 10 04.02.01 (A) Synchronising.doc © Brush Electrical Machines Ltd. 2003 Thus, as generator 'B' catches up with generator 'A', each lamp goes out in turn, and at a decreasing rate, as synchronism is approached. Finally, at synchronism, No.1 lamp remains extinguished long enough for the generator breaker to be closed. The lamps are arranged either in a triangle with No.1 at the top, or in a line with No.1 in the centre. They may be lettered 'A', 'B' and 'C' instead of being numbered. Depending on whether the order of going out is clockwise or anti-clockwise with the triangular arrangement, or left-to-right or right-to-left with the inline arrangement, the operator can deter-mine whether the incoming generator ,is fast or slow - which cannot be done with the 2-lamp method. ► 6 SYNCHROSCOPE Figure 5: Synchroscope A typical synchroscope is shown in Figure 5. It is an instrument with a movement similar to that of a power factor meter, but with the two windings fed from the running and incoming voltages. Whereas in a power factor meter the current/voltage phase relationship is fixed and the pointer is stationary, in a synchroscope the phase relationship between the two voltages is constantly changing and the pointer rotates continuously, the direction of movement depending on whether the incoming machine is rotating faster or slower than the running. The face is marked with arrows denoting FAST or SLOW; these terms always refer to the incoming generator. When the pointer passes through the 12 o'clock position, the machines are momentarily in phase. {Some synchroscopes are marked '+' and '-'. The plus sign corresponds to FAST and the minus to SLOW). Standard specifications often require lamp back-up to the synchroscope. Many early synchroscopes are short time rated, and it is necessary to switch off these units when the synchronising operation has been completed. 7 SYNCHRONISING AT THE SWITCHBOARD/CONTROL PANEL Most switchboards/control panels control two or more generators, and some systems have section breakers or interconnectors to other generator systems, anyone of which may have to be synchronised with running machines. It would not be economic to have a separate synchroscope for each one, as it is used only infrequently. Common practice is therefore to have one synchroscope (sometimes with back-up lamps) in a central or conspicuous position on or near the switchboard/control panel together with selector switches whereby any chosen machine may be made the 'Incomer'. Selection may be by manual switch, key or plug. The running side is usually taken from the busbar. Where the switchboard handles high voltage the incoming and running voltage signals are taken through voltage transformers. The synchroscope is normally provided with fuses and an isolating switch, as it is not good practice to leave it in circuit when it is not in use.
  • 66. SYNCHRONISING Training Module: 04.02.01 Issue: A Date: April 2003 Page: 9 of 10 04.02.01 (A) Synchronising.doc © Brush Electrical Machines Ltd. 2003 To use the synchroscope, having selected which is to be the incoming generator, the voltages and frequencies are first matched as already described in Section 4. The synchroscope is then switched on; its pointer will be rotating. The incoming speed regulator is trimmed until the pointer is moving very slowly in the FAST direction. As it next approaches the 12 o'clock position, the hand is placed over the breaker control button or handle and, just before the pointer reaches 12 o'clock, it is operated to close the breaker. The synchroscope will then stop and remain locked in the 12 o'clock position as the generators remain in synchronism. Finally, the synchroscope should be switched off. The reason why the incoming generator should be running the faster is that, when the breaker is closed, it will immediately take up a small part of the load. If it were running slower, that load would be negative - that is, the machine would 'motor' - and a reverse power situation would exist. The generator's reverse power protection might then cause the breaker to trip. ► 8 AUTOMATIC SYNCHRONISING It is common for switchboards/control panels to be provided with an automatic synchronising feature. The automatic synchroniser compare the incoming and running voltages and frequencies as well as their phase relation. Should any of these be outside limits, the incoming voltage regulator or speed regulator is automatically trimmed. Only when all three are within predetermined limits is a signal given automatically to the circuit breaker to close. Here again there is usually only one auto-synchronising unit to each switchboard; it is connected automatically to whichever machine is being started so long as the synchronising selector switch is set to AUTO. Auto-synchronising is usually reserved for generators only. All other synchronising - for example across section breakers or interconnectors or on L V switchboards - is normally by hand. 9 CHECK SYNCHRONISING In many instances, particularly with smaller generators and in the cases just mentioned, automatic synchronising is not used, and the exercise must be carried out manually by lamp or synchroscope. In such cases there is a danger that, if the manual synchronising is carried out unskilfully, the switch could be closed at the wrong instant and severe damage could result to expensive machinery. This can be prevented by 'check synchronising'. The equipment is similar to that used for auto- synchronising, but it does not automatically trim the incoming voltage, frequency and phase - it only monitors them. Nor does it carry out the final act of closing the circuit breaker automatically; these all have to be done manually by the operator. However it does inhibit the breaker's manual closing circuit so that, unless all three synchronising conditions are satisfied together, the operator cannot close the breaker even though he presses the CLOSE button. If the breaker then fails to close, the whole synchronising process must be repeated. Some check synchronising units sense only phase angle difference and do not monitor voltage or frequency differences. They rely on manual adjustment of voltage and frequency and only inhibit the closing of the breaker when the phase angle difference is excessive. It should be noted that voltage difference will cause circulating reactive current only. Although this is not desirable, it does not cause any mechanical shock and consequent damage to the transmission or the turbine since no active power is involved. When, and only when, the check synchroniser is satisfied that the voltages, frequencies and phase difference are within acceptable limits (or, in the case of the 'phase only' type, that the phase difference is within limits), it closes a contact which 'arms' the circuit-breaker closing circuit, so permitting closure when the operator presses the CLOSE switch. The same contact on the check synchroniser can also momentarily light an IN SYNCHRONISM or READY TO SYNCHRONISE lamp, indicating to the operator that the breaker is ready for closing. Once this lamp has gone out again, he cannot close the breaker until it illuminates a second time.
  • 67. SYNCHRONISING Training Module: 04.02.01 Issue: A Date: April 2003 Page: 10 of 10 04.02.01 (A) Synchronising.doc © Brush Electrical Machines Ltd. 2003 Where check synchronising is fitted, it is brought automatically into circuit whenever a second or subsequent generator has been started and selected for switching on-line; it so serves as a protection against incorrect operation. Check synchronisers may also be fitted across section breakers, interconnectors and L V incomers from transformers - in fact at any point in the network where it might be possible to close across two unsynchronised systems accidentally. They are also fitted across main generator incomer breakers even when auto-synchronising is provided. They are usually arranged to come into action automatically if manual synchronising is selected. Sometimes operators form the bad habit of holding the breaker control switch closed before synchronism is reached, and relying on the arming contact of the check synchroniser to complete the closing circuit. This is bad practice and must be avoided. 10 CLOSING ONTO DEAD BUSBAR If it is required to connect an incoming generator, or L V transformer incomer, onto a dead busbar, the check synchroniser will not allow it to happen because, one side being dead, the two sides can never be in synchronism. In that case the check synchroniser must be temporarily 'cheated' while the connection is made. On most switchboards/control panels a special switch is provided for this purpose. It is spring-Ioaded to return to the OFF position so that the check synchroniser cannot be left permanently out of operation. This cheating switch may be tagged CLOSE ONTO DEAD BUSBAR or CHECK SYNC. OVERRIDE or other similar wording. ►
  • 68. CAPABILITY DIAGRAMS Training Module: 04.03.01 Issue: A Date: April 2003 Page: 1 of 10 04.03.01 (A) Capability Diagrams.doc © Brush Electrical Machines Ltd. 2003 CAPABILITY DIAGRAMS
  • 69. CAPABILITY DIAGRAMS Training Module: 04.03.01 Issue: A Date: April 2003 Page: 2 of 10 04.03.01 (A) Capability Diagrams.doc © Brush Electrical Machines Ltd. 2003 CONTENTS 1 INTRODUCTION........................................................................................................................................ 3 2 STATOR CURRENT .................................................................................................................................. 3 3 POWER OUTPUT ...................................................................................................................................... 3 4 ROTOR CURRENT.................................................................................................................................... 4 5 STABILITY OF THE ROTOR..................................................................................................................... 4 6 TEMPORARY LIMITATION....................................................................................................................... 5 7 USE OF THE CAPABILITY DIAGRAM..................................................................................................... 6 8 CAPABILITY DIAGRAM FOR SYNCHRONOUS MOTOR....................................................................... 8 9 CAPABILITY DIAGRAM FOR SYNCHRONOUS CONDENSER ............................................................. 9
  • 70. CAPABILITY DIAGRAMS Training Module: 04.03.01 Issue: A Date: April 2003 Page: 3 of 10 04.03.01 (A) Capability Diagrams.doc © Brush Electrical Machines Ltd. 2003 1 INTRODUCTION The principal limitations on the output of a generator are as follows: Ø Current heating of the stator (armature). Ø Power Output of the prime mover. Ø Current heating of the rotor (field). Ø Stability of the rotor angle. There are other limitations such as the heating due to iron losses, harmonic currents, negative and zero sequence currents, etc., but the four listed above have the most decisive limiting effect. ► 2 STATOR CURRENT Consider first the stator. The I 2 R, or 'copper', losses due to the load current are, together with the iron losses, the main sources of stator heating. With a given cooling system there is clearly an upper limit to such continuous stator currents no matter what their power factor may be. Stated another way, there is a limit of MVA beyond which the generator must not be allowed to go continuously, and this limit applies at all power factors. Figure 1 In Figure 1, if the reactive (MVAr lagging) loading is taken as the x-axis and the active (MW) loading as the y-axis, then for any given loading P (PN being the active component and PM the reactive), the line OP represents the MVA of that load (= √PN 2 + PM 2 ), and the angle POM is the phase angle of the load. If a semi-circle is drawn about the origin O and with radius equal to the maximum permitted MVA, then only those loads (such as P) within that semi-circle are within the capacity of the generator. This is the first limitation. 3 POWER OUTPUT The electrical MW rating of an engine driven generating set is limited by the mechanical output of the prime mover. Therefore, if a horizontal line is drawn across the MW axis at a level equal to the maximum output of the prime mover (OA), the top part of the semi-circle is cut off, since it represents MW power which is not attainable from the engine. Therefore the loading of the generator must be confined to points within the remainder of the semi-circle. This is the second limitation and is shown in Figure 1 as a dotted line. ►
  • 71. CAPABILITY DIAGRAMS Training Module: 04.03.01 Issue: A Date: April 2003 Page: 4 of 10 04.03.01 (A) Capability Diagrams.doc © Brush Electrical Machines Ltd. 2003 4 ROTOR CURRENT To achieve the rated MVA loading or, a certain level of excitation is required. This calls for a certain rotor current, with its consequent I 2 R losses which cause rotor heating. The cooling system takes this, together with the stator heater heating, into account. Any increase in excitation beyond this level - and hence in rotor current - will cause rotor overheating; so at first sight the load point P should remain to the left of the line RB. Figure 2 However, there is a point E* on the other side of the origin such that the line ER represents the emf of the generator when operating at its rated load and power factor. ER then represents not only the emf but also the excitation - and so the rotor current - needed to produce it. Constant excitation at various maximum loads and power factors is therefore represented by an arc of a circle through R, centre E, shown by the arc RQ in Figure 2. This arc this represents the maximum allowable rotor current at different maximum loads and power factors. To avoid overheating the rotor, therefore, the load point must lie to the left of the arc RQ (not to the left of line RB as first suggested above) This is the third limitation. Note: *Though not strictly necessary to know for the purpose of this explanation, the position of point E is determined from the generators synchronous reactance. If this is n per unit (= percent/100), then the length OE is 1/n times the radius of the semicircle. Thus if n = 200% (fairly typical), E is halfway between O and the circumference. ► 5 STABILITY OF THE ROTOR When the machine is generating, the rotor is driven ahead of the stators rotating magnetic field at an angle depending on the actual active load - it is called the 'Power Angle', symbol λ. The opposing torque developed by the generator on the engine is due to the magnetic back-pull on the rotors poles by the stators magnetic field. The greater the power angle, the greater the back torque. The driving torque delivered by the engine is just balanced by this back torque from the rotor, and the rotor is stable. When the loading is lagging reactive, armature reaction in the stator causes the field poles to become partly demagnetised. The consequent loss of air-gap flux reduces the net emf and so the terminal voltage; this is detected by the AVR, which causes increased excitation to restore the air gap flux and so the emf. With leading reactive loading the opposite effect occurs. The leading stator current causes the field poles to become more magnetised at first. The gain of air-gap flux increases the net emf and so the terminal voltage; this is detected by the AVR, which then decrease excitation to restore the air-gap flux.
  • 72. CAPABILITY DIAGRAMS Training Module: 04.03.01 Issue: A Date: April 2003 Page: 5 of 10 04.03.01 (A) Capability Diagrams.doc © Brush Electrical Machines Ltd. 2003 If this process were allowed to continue and the leading load to increase further, the point would be reached where the excitation of the rotor poles would be reduced to nothing, and all the air-gap flux would be provided by the stator alone. There would then be no rotor poles upon which the stator could pull back. The prime mover would drive the rotor ahead out of synchronism, and the generator would go unstable, pulling out of step. This situation would occur if the reactive loading reached a value equal to OE (leading), since at E the excitation is reduced to zero. Therefore the load point P must never be allowed to go to the left of the vertical line through E - that is, the leading MVAr must never be allowed to exceed the value OE. This is the fourth limitation and is shown in Figure 3. Figure 3 Clearly such a limitation must never be allowed to occur or even to be approached, as the generator would become difficult to control. There is therefore a limit to the amount of leading current (or MVA) which a generator may be allowed to produce. The theoretical limit set in the previous paragraph is therefore in practise too high. The practical limit will be appreciably less and is represented by the dotted curve ST in Figure 3; the calculation of this curve is complicated, and it is merely indicated here. Its shape will depend on whether the rotor is cylindrical or has salient poles. In practise, however, leading loads on platforms should never arise. So in Figure 3 the theoretical semicircle inside which the loading of the generator must lie is limited at the top and now at both sides, and the only 'usable' part is the coloured area if the generator is to run within its rating and remain stable. The coloured part of Figure 3 is called the 'Capability Diagram' of that generator set. It provides a constant guide not only on the loaded state of the generator but also on its maximum allowable further loading. It shows whether any intended additional loading will still remain within, or go outside of, the rating of the generator set, and it therefore indicates whether or not s further machine should be started up. All that is required to determine the existing load point on the capability diagram are the generator MW and MVAr instrument readings. ► 6 TEMPORARY LIMITATION A special case arises when large motors are to be started. They impose a large, but temporary, reactive loading while starting, which fails to a much smaller value when run up to speed. The extra excitation needed for this can if necessary be found from the AVR's field forcing circuits, which provide extra field current above the normal maximum. This, although above the steady current limit of the rotor windings (arc RQ), may be tolerated for a short time without damaging the rotor.
  • 73. CAPABILITY DIAGRAMS Training Module: 04.03.01 Issue: A Date: April 2003 Page: 6 of 10 04.03.01 (A) Capability Diagrams.doc © Brush Electrical Machines Ltd. 2003 For this reason capability diagrams are sometimes furnished with one or more additional rotor current limitation arcs with a specified time limit of, for example, 30 seconds, as shown in Figure 4. This means that, within this time, the reactive loading may be increased to the indicated higher limit to allow the motor to start, provided that it falls back to within normal limits within the specified time when the motor has run up to its steady speed. On some systems, if the rotor current goes beyond the higher limit, or if it fails to return to within normal limits within the specified time, the generator is tripped. Figure 4 If the total reactive load on starting falls outside even this higher temporary limit and automatic tripping is not fitted, it goes beyond the field forcing limit of the AVR, and a prolonged dip of the system voltage will result, besides risking damage to the rotor. ► 7 USE OF THE CAPABILITY DIAGRAM To use the capability diagram, the Operator looks at the wattmeter and varmeter of the generator which is to be further loaded and he plots the point P on the diagram corresponding to the MVAr and MW standing load readings see Figure 5. He notes, or calculates, the additional load in the MVAr and MW which he intends to put on top the generator ; these he adds to the MVAr and MW values of the point P. If the resulting point P1 lies within the coloured area, the generator can accept the additional lad. If not, he must be prepared to start an additional load. If not, he must be prepared to start an additional generator to share the total load. If the excess is marginal, he must use his discretion. Figure 5
  • 74. CAPABILITY DIAGRAMS Training Module: 04.03.01 Issue: A Date: April 2003 Page: 7 of 10 04.03.01 (A) Capability Diagrams.doc © Brush Electrical Machines Ltd. 2003 Particular care is needed if a large motor is to be started. Although the additional MVAr and MW at full load may be acceptable to the generator, the MVAr due to the large starting current may not. For example, a certain gas export compressor motor has an input of 5MW at 0.85 PF, giving a full load demand of 2.6 MVAr and 5.0MW, which might be acceptable on top of the standing load. But the starting current is approximately 1500A at 0.25 PF, giving a starting demand of about 25MVAr and 7MW. While even the 7MW might be acceptable to the generator, the capability diagram would show that the additional 25 MVAr on the starting almost certainly would not be, even taking into account any temporary margin allowed. The operator would need to put on line extra generators to accommodate this start, even if he took them off again once the motor had run up. The following illustrates this point with a different motor. When a second generator is put on line, it is assumed that both share the load equally; therefore the MW and MVAr loadings on each are half what they were with one generator only. This means that the 'working point' P has half the previous values and is therefore much nearer the centre. This leaves more room for additional loading, remembering also that the additional load itself on each generator is also halved. ► Example A 6.6kV generator is rated 15MW at 0.85PF. At a certain moment it is carrying a standing load of 8MW and 6 MVAr (represented by point P in Figure 5) as given by its switchboard instruments. It is desired to start and run a 3600kWm, 0.8PF water injection motor (efficiency 96%) on this generator. The motors starting current is four times full load current at 0.25PF. The capability diagram, including the temporary limitation curve is given in Figure 5. Can this generator carry the extra load, and can the motor be started on it? If not, what action should be taken? (In the following calculations all results have generally been rounded off to the nearest 10 units. Operations at a generated voltage of 6.8kV has been assumed). Generator Generator rating 15MW at 0.85pF and 6.6kV (6.8kV operation) (15MW) Full-load current (l) = 15000 = 1500 √3 x 6.8 x 0.85 cos Φ = 0.85, ∴sin Φ= 0.53 Full-load reactive power = √3 x kV x l x sin Φ = √3 x 6.8 x 1500 x 0.53 = 9360 (say 9.4 MVAr) Motor (Running) Motors output is 3600kWm at 0.9 efficiency; Motor input is 3600 = 4000kWe at 0.8pF (4.0MWe) 0.9 cos Φ = 0.8, ∴sin Φ = 0.6 Full-load current (lFL) = 4000 = 425A √3 x 6.8 x 0.8 Full-load reactive power = √3 x kV x lFL x sin Φ = √3 x 6.8 x 425 x 0.6 = 3000KVAr (3.0MVAr) Motor (Starting) Starting current (lST) = 4 x full-load running current (lFL) = 4 x 425 = 1700A at 0.25pF cos Φ = 0.25, ∴sin Φ= 0.968
  • 75. CAPABILITY DIAGRAMS Training Module: 04.03.01 Issue: A Date: April 2003 Page: 8 of 10 04.03.01 (A) Capability Diagrams.doc © Brush Electrical Machines Ltd. 2003 Starting active power = √3 x kV x lST x cos Φ = √3 x 6.8 x 1700 x 0.25 = 5010KWe (say 5.0MWe) and starting reactive power = √3 x kV x lST x sin Φ = √3 x 6.8 x 1700 x 0.968 = 19380KVAr (say 19.4MVAr) Combination When running: standing load is 8.0MW & 6.0MVAr motor load is 4.0MW & 3.0MVAr Total: 12.0MW & 9.0MVAr Plotted on the capability diagram, this gives point P1 which is well within the coloured diagram limits and is therefore acceptable. When starting: standing load is 8.0MW & 6.0MVAr motor load is 5.0MW & 19.4MVAr Total: 13.0MW & 25.4MVAr Plotted on the capability diagram, this gives point P2, which lies outside the diagram and even beyond the temporary limit. The starting of this motor is therefore not acceptable, even though the current could be carried continuously once running. Before starting, therefore, either the standing load must be sufficiently reduced or another generator set must be started and put on-line. ► 8 CAPABILITY DIAGRAM FOR SYNCHRONOUS MOTOR Although the capability diagram so far described takes the form of a semi-circle, it can be continued below the horizontal axis to become a complete circle. In that case the y-axis, representing active power (or MW), is negative and so indicates negative active power supplied by the machine. This is equivalent to active power being received by the machine; that is to say, the machine is absorbing true power and is therefore motoring. The x-axis, representing lagging or leading machine power supplied, is not affected. Figure 6
  • 76. CAPABILITY DIAGRAMS Training Module: 04.03.01 Issue: A Date: April 2003 Page: 9 of 10 04.03.01 (A) Capability Diagrams.doc © Brush Electrical Machines Ltd. 2003 The two lower quadrants shown in Figure 6 thus represent the machine operating as a motor - that is, as a synchronous motor. The left-hand lower quadrant indicates such a motor running under excited and therefore supplying some leading VAr's to the system, equivalent to drawing lagging VAr's from it. The right hand lower quadrant indicates a motor well excited and supplying lagging VAr's to the system - equivalent to drawing leading VAr's from it. It should be noted that the excitation can be adjusted so that the machine is drawing neither leading nor lagging VAr's (point Q) - that is, it is taking no reactive power at all, only active power. Such a motor is then running at unity power factor - a useful feature of the synchronous motor. It is possible to go even further. The machine can be deliberately run as a motor overexcited i.e, in the fourth quadrant - where it will draw active power from the system as it motors, but it will at the same time supply lagging VAr's, and it will therefore run at a leading power factor. If a mixed load of induction motors and a large synchronous motor is installed, the synchronous motor run in this manner can help compensate for the poorer power factors of the induction motors. Below the horizontal the prime mover output limitation clearly no longer applies, but the rotor and stability limitations apply as before. The 'working point' P must therefore fall within the coloured area of Figure 6 if the motor is to work within its design limits. When determing the working point P, all losses (including friction and windage losses) must be added to the known mechanical power of the motor drive, since all go into the total power absorbed. The losses can be calculated from the efficiency of the motor at that particular loading. There are no synchronous motor drives in offshore or onshore installations, but they are used elsewhere onshore in larger plants where exact constant speed operation is required. ► 9 CAPABILITY DIAGRAM FOR SYNCHRONOUS CONDENSER A synchronous motor, whenever excited, can be used as if it were a bank of static capacitors. Figure 7 Figure 7 represents the capability diagram of such a synchronous machine. The full semi-circle above the line depicts its generation mode, as discussed previously. The y-axis represents generated active power (MW). If extended downwards it represents negative active power - that is, motoring instead of generated power. The x-axis to the right represents lagging reactive power (MVAr) given out by the machine whether generating or motoring and is associated with the degree of excitation.
  • 77. CAPABILITY DIAGRAMS Training Module: 04.03.01 Issue: A Date: April 2003 Page: 10 of 10 04.03.01 (A) Capability Diagrams.doc © Brush Electrical Machines Ltd. 2003 Imagine such a machine used as a generator and driven up to speed by its prime mover and synchronised onto the system, where it takes up its share of the active and reactive loads. The working point of the capability diagram of Figure 7 would be, say, P. Suppose then that the prime mover is unclutched, or that its fuel is cut off, but that the machine is well excited and its excitation remains unchanged. Mechanical drive to the machine then ceases, but it continues to rotate in synchronism with the system. It draws from the system only enough active power to keep itself going without driving any external load - it behaves as an unloaded motor, drawing just enough active power to make good its losses - a 'reverse power' situation. Plotted on the capability diagram of Figure 7, the working point would now be Q, with slightly negative MW but delivering rather more lagging MVAr as before due to its unaltered excitation. Such a machine would then be supplying reactive lagging power (megaVAr's) but no active power (megawatts). Supplying lagging VAr's is the same thing as receiving leading VAr's, since one is the negative of the other. Therefore a machine operating as described above can be regarded as drawing leading reactive power - that is to say, it behaves as a static capacitor. The machine is then called a 'synchronous capacitor', although the old name 'synchronous condenser' remains in common use. Moreover, the amount of leading reactive power drawn will be determined by the degree of over- excitation. Therefore the 'capacitance' is infinitely variable as required by the changing system load conditions, unlike that of a bank of static capacitors which can only be switched. If a synchronous condenser is not available to correct the power factor of a system, a corresponding effect can be obtained by running any synchronous motors in the system in an over excited state. In this condition they will draw leading reactive current in addition to their active current. This will compensate for the large lagging currents drawn by many induction motors by providing a useful contribution to the lagging VAr's needed by those motors instead of calling on the generators to do so. ►
  • 78. ELECTRICAL DEVICE NUMBERS & FUNCTIONS Training Module: 04.07.01 Issue: A Date: April 2003 Page: 1 of 8 04.07.01 (A) Device Numbers.doc © Brush Electrical Machines Ltd. 2003 ELECTRICAL DEVICE NUMBERS & FUNCTIONS
  • 79. ELECTRICAL DEVICE NUMBERS & FUNCTIONS Training Module: 04.07.01 Issue: A Date: April 2003 Page: 2 of 8 04.07.01 (A) Device Numbers.doc © Brush Electrical Machines Ltd. 2003 CONTENTS 1 INTRODUCTION........................................................................................................................................ 3 2 DEVICE NUMBERS................................................................................................................................... 3
  • 80. ELECTRICAL DEVICE NUMBERS & FUNCTIONS Training Module: 04.07.01 Issue: A Date: April 2003 Page: 3 of 8 04.07.01 (A) Device Numbers.doc © Brush Electrical Machines Ltd. 2003 1 INTRODUCTION Devices in switching equipment are referred to by numbers, with appropriate suffix letters when necessary, according to the function they perform. These numbers are based on a system adopted as standard for automatic switchgear by IEEE, and incorporated in American Standard C37.2-1970. This system is used in connection diagrams, in instruction books, and in specifications. ► 2 DEVICE NUMBERS Device No. Device Definition and Function 1 Master Element This is the initiating device, such as a control switch, voltage relay, float switch etc., which serves either directly, or through such permissive devices as protective and time-delay relays to place an equipment in or out of operation. 2 Time-Delay Starting or Closing Relay This is a device which functions to give a desired amount of time delay before or after any point of operation in a switching sequence or protective relay system, except as specifically provided by device functions 48, 62, and 79 described later. 3 Checking or Interlocking Relay This operates in response to the position of a number of other devices, (or to a number of predetermined conditions), in an equipment, to allow an operating sequence to proceed, to stop, or to provide a check of the position of these devices or of these conditions for any purpose. 4 Master Contactor This device, generally controlled by Device No.1 or equivalent, and the required permissive and protective devices, that serves to make and break the necessary control circuits to place an equipment into operation under the desired conditions and to take it out of operation under other or abnormal conditions. 5 Stopping Device This control device is used primarily to shut down an equipment and hold it out of operation. [This device may be manually or electrically actuated, but excludes the function of electrical lockout (see device function 86) on abnormal conditions] 6 Starting Circuit Breaker The principle function of this device is to connect a machine to its source of starting voltage. 7 Anode Circuit Breaker Is used in the anode circuits of a power rectifier for the primary purpose of interrupting the rectifier circuit if an arc back should occur. 8 Control Power Disconnecting Device This is a disconnecting device - such as a knife switch, circuit breaker or pullout fuse block, used for the purpose of connecting and disconnecting the source of control power to and from the control bus or equipment. Note: Control power is considered to include auxiliary power which supplies such apparatus as small motors and heaters 9 Reversing Device This is used for the purpose of reversing a machine field or for performing any other reversing functions. 10 Unit Sequence Switch Used to change the sequence in which units may be placed in and out of service in multiple-unit equipments. 11 Reserved for future application 12 Over-Speed Device This is usually a direct connected speed switch which functions on machine over-speed. 13 Synchronous-Speed Device For example centrifugal-speed switch, a slip-frequency relay, a voltage relay, an undercurrent relay or any type of device, operates at approximately synchronous speed of a machine. 14 Under-Speed Device Functions when the speed of a machine falls below a predetermined value.
  • 81. ELECTRICAL DEVICE NUMBERS & FUNCTIONS Training Module: 04.07.01 Issue: A Date: April 2003 Page: 4 of 8 04.07.01 (A) Device Numbers.doc © Brush Electrical Machines Ltd. 2003 Device No. Device Definition and Function 15 Speed or Frequency, Matching Device Functions to match and hold the speed or the frequency of a machine or of a system equal to, or approximately equal to, that of another machine, source or system. 16 Reserved for future application 17 Shutting or Discharge Switch This switch serves to open or to close a shutting circuit around any piece of apparatus (except a resistor), such as a machine field, a machine armature, a capacitor or a reactor. Note: This excludes devices which perform such shutting operations as may be necessary in the process of starting a machine by devices 6 or 42, or their equivalent, and also excludes device 73 function which serves for the switching of resistors. 18 Accelerating or Decelerating Device This is used to close or to cause the closing of circuits which are used to increase or to decrease the speed of the machine. 19 Starting-to-Running Transition Contactor This device initiates or causes the automatic transfer of a machine from the starting to the running power connection. 20 Electrically Operated Valve This is an electrically operated, controlled or monitored valve in a fluid line. Note: The function of the valve may be indicated by the use of the suffixes 21 Distance Relay This device functions when the circuit admittance, impedance or reactance increases or decreases beyond predetermined limits. 22 Equalizer Circuit Breaker This breaker serves to control or to make and break the equalizer or the current-balancing connections for a machine field, or for regulating equipment, in a multiple-unit installation. 23 Temperature Control Device Its function is to raise or lower the temperature of a machine or other apparatus, or of any medium, when its temperature falls below, or rises above, a predetermined value. Note: An example is a thermostat which switches on a space heater in a switchgear assembly when the temperature falls to a desired value as distinguished from a device which is used to provide automatic temperature regulation between close limits and would be designated as 90T. 24 Reserved for future application 25 Synchronising or Synchronism-Check Device This device operates when two ac circuits are within the desired limits of frequency, phase angle or voltage, to permit or to cause the paralleling of these two circuits. 26 Apparatus Thermal Device This device functions when the temperature of the shunt field or the armortisseur winding of a machine. or that of a load limiting or load shifting resistor or of a liquid or other medium exceeds a predetermined value; or if the temperature of the protected apparatus, such as a power rectifier, or of any medium decreases below a predetermined value. 27 Undervoltage Relay This device functions on a given value of undervoltage 28 Flame Detector Monitors the presence of the pilot or main flame in such apparatus as a gas turbine or a steam boiler. 29 Isolating Contactor Expressly used for disconnecting one circuit from another for the purposes of emergency operation, maintenance, or test. 30 Annunciator Relay This non-automatic reset device gives a number of separate visual indications upon the functioning of protective devices, and which may also be arranged to perform a lockout function. 31 Separate Excitation Device Connects a circuit such as the shunt field of a synchronous converter, to a source of separate excitation during the starting sequence; or one which energizes the excitation and ignition circuits of a power rectifier.
  • 82. ELECTRICAL DEVICE NUMBERS & FUNCTIONS Training Module: 04.07.01 Issue: A Date: April 2003 Page: 5 of 8 04.07.01 (A) Device Numbers.doc © Brush Electrical Machines Ltd. 2003 Device No. Device Definition and Function 32 Directional Power Relay This functions on a desired value of power flow in a given direction or upon reverse power resulting from arc back in the anode or cathode circuits of a power rectifier. 33 Position Switch Makes or breaks contact when the main device or piece of apparatus, which has no device function number, reaches a given position. 34 Master Sequence Device This device such as a motor operated multi-contact switch, or the equivalent, or a programming device, such as a computer, that establishes or determines the operating sequences of the major devices in an equipment during stopping or during other sequential switching operations. 35 Brush-Operating, or Slipring Short Circuiting Device This is used for raising, lowering, or shifting the brushes of a machine, or for short circuiting its sliprings, or for engaging or disengaging the contracts of a mechanical rectifier. 36 Polarity or Polarising Voltage Device Operates or permits the operation of another device on a predetermined polarity only or verifies the presence of a polarising voltage in an equipment. 37 Undercurrent or Underpower Relay Functions when the current or power flow decreases below a predetermined value. 38 Bearing Protective Device Functions on excessive bearing temperature, or on other abnormal mechanical conditions, such as undue wear, which may eventually result in excessive bearing temperature. 39 Mechanical Condition Monitor This device functions upon the occurrence of an abnormal mechanical condition (except that associated with bearings as covered under device function 38), such as excessive vibration, eccentricity, expansion, shock, tilting, or seal failure. 40 Field Relay Functions on a given or abnormally low value or failure of machine field current, or on an excessive value of the reactive component of armature current in an ac machine indicating abnormally low field excitation. 41 Field Circuit Breaker Is a device which functions to apply, or to remove, the field excitation of a machine. 42 Running Circuit Breaker The principle function of this device is to connect a machine to its source of running or operating voltage. This function may also be used for a device, such as a contactor, that is used in series with a circuit breaker or other fault protecting means, primarily for frequent opening and closing of the circuit. 43 Manual Transfer or Selector Device This transfers the control circuits so as to modify the plan of operation of the switching equipment or of some of the devices. 44 Unit Sequence Starting Relay Is a device which functions to start the next available unit in a multiple-unit equipment on the failure or on the non-availability of the normally preceding unit. 45 Atmospheric Condition Monitor This functions upon the occurrence of an abnormal atmosphere condition, such as damaging fumes, explosive mixtures, smoke, or fire. 46 Reverse-Phase, or Phase Balance, Current Relay This relay functions when the polyphase currents are of reverse- phase sequence, or when the polyphase currents are unbalanced or contain negative phase sequence components above a given amount. 47 Phase Sequence Voltage Relay Functions on a predetermined value of polyphase voltage in the desired phase sequence. 48 Incomplete Sequence Relay This relay generally returns the equipment to the normal, or off, position and locks it out if the normal starting , operating or stopping sequence is not properly completed within a predetermined time. If the device is used for alarm purposes only, it should preferably be designated as 48A (alarm).
  • 83. ELECTRICAL DEVICE NUMBERS & FUNCTIONS Training Module: 04.07.01 Issue: A Date: April 2003 Page: 6 of 8 04.07.01 (A) Device Numbers.doc © Brush Electrical Machines Ltd. 2003 Device No. Device Definition and Function 49 Machine or Transformer, Thermal Relay This relay functions when the temperature of a machine armature, or other load carrying winding or element of a machine, or the temperature of a power rectifier or power transformer (including a power rectifier transformer) exceeds a predetermined value. 50 Instantaneous Overcurrent, or Rate-of- Rise Relay This functions instantaneously on an excessive value of current, or on a excessive rate of current rise, thus indicating a fault in the apparatus or circuit being protected. 51 AC time overcurrent Relay Is a relay with either a definite or inverse time characteristic that functions when the current in an ac circuit exceeds a predetermined value. 52 AC Circuit Breaker This is used to close and interrupt an ac power circuit under normal conditions or to interrupt this circuit under fault or emergency conditions. 53 Exciter or dc generator relay This forces the dc machine field excitation to build up during starting or which functions when the machine voltage has built up to a given value. 54 Reserved for future application 55 Power Factor Relay This operates when the power factor in an ac circuit rises above or below a predetermined value. 56 Field Application Relay Is a relay that automatically controls the application of the field excitation to an ac motor some predetermined point in the slip cycle 57 Short Circuiting or Grounding Device This primary circuit switching device functions to short circuit or to ground a circuit in response to automatic or manual means. 58 Rectification Failure Relay Functions if one or more anodes of a power rectifier fail to fire, or to detect an arc-back or on failure of a diode to conduct or block properly. 59 Overvoltage Relay Functions on a given value of overvoltage. 60 Voltage or Current Balance Relay Operates on a given difference in voltage, or current input or output of two circuits. 61 Reserved for future application 62 Time Delay Stopping or Opening Relay Serves in conjunction with the device that initiates the shutdown, stopping, or opening operation in an automatic sequence. 63 Pressure Switch Operates on given values or on a given rate of change of pressure. 64 Ground Protective Relay Functions on failure of the insulation of a machine, transformer or of other apparatus to ground, or on flashover of a dc machine to ground. Note: This function is assigned only to a relay which detects the flow of current from the frame of a machine or enclosing case or structure of a piece of apparatus to ground, or detects a ground on a normally ungrounded winding or circuit. It is not applied to a device connected in the secondary circuit or secondary neutral of current transformer, connected in the power circuit of a normally grounded system. 65 Governor Is the assembly of fluid, electrical or mechanical control equipment used for regulating the flow of water, steam, or other medium to the prime mover for such purposes as starting, holding speed or load, or stopping. 66 Notching or Jogging Device Functions to allow only a specified number of operations of a given device, or equipment, or a specified number of successive operations within a given time of each other. It also functions to energize a circuit periodically or for fractions of specified time intervals, or that is used to permit intermittent acceleration or jogging of a machine at low speeds for mechanical positioning. 67 AC Directional Overcurrent Relay Functions on a desired value of ac overcurrent flowing in a predetermined direction.
  • 84. ELECTRICAL DEVICE NUMBERS & FUNCTIONS Training Module: 04.07.01 Issue: A Date: April 2003 Page: 7 of 8 04.07.01 (A) Device Numbers.doc © Brush Electrical Machines Ltd. 2003 Device No. Device Definition and Function 68 Blocking Relay Initiates a pilot signal for blocking of tripping on external faults in a transmission line or in other apparatus under predetermined conditions, or cooperates with other devices to block tripping or to block reclosing on an out-of-step condition or on power swings. 69 Permissive Control Device Generally a two position, manually operated switch that in one position permits the closing of a circuit breaker, or the placing of an equipment into operation, and in the other position prevents the circuit breaker or the equipment from being operated. 70 Rheostat This variable resistance device used in an electric circuit, which is electrically operated or has other electrical accessories, such as auxiliary, position, or limit switches. 71 Level Switch Operates on given values, or a given rate of change, of level. 72 DC Circuit Breaker Used to close and interrupt a dc power circuit under normal conditions or to interrupt this circuit under fault or emergency conditions. 73 Load Resistor Contactor Used to shunt or insert a step of load limiting, shifting, or indicating resistance in a power circuit, or to switch a space heater in circuit, or to switch a light, or regenerative load resistor of a power rectifier or other machine in and out circuit. 74 Alarm Relay Is a device other than an annunciator as covered under Device No.30, which is used to operate in connection with, a visual or audible alarm. 75 Position Changing Mechanism Used for moving a main device from one position to another in an equipment; as for example, shifting a removable circuit breaker unit to and from the connected, disconnected, and test positions. 76 DC Overcurrent Relay Functions when the current in a dc circuit exceeds a given value. 77 Pulse Transmitter Used to generate and transmit pulses over a telemetering or pilot-wire circuit to the remote indicating or receiving device. 78 Phase Angle Measuring, or Out-of-Step Protective Relay Functions at a predetermined phase angle between two voltages or between two currents or between voltage and current. 79 AC Reclosing Relay Controls the automatic reclosing and locking out of an ac circuit interrupter. 80 Flow Switch Operates on given values, or on a given rate of change, of flow. 81 Frequency Relay Functions on a predetermined value of frequency - either under or over or on normal system frequency - or rate of change of frequency. 82 DC Reclosing Relay Controls the automatic closing and reclosing of a dc circuit interrupter, generally in response to load circuit conditions. 83 Automatic Selective Control or Transfer Relay Operates to select automatically between certain sources or conditions in an equipment, or performs a transfer operation automatically. 84 Operating Mechanism This is the complete electrical mechanism or servo-mechanism, including the operating motor, solenoids, position switches, etc., for a tap changer, induction regulator or any similar piece of apparatus which has no device function number. 85 Carrier or Pilot Wire Receiver Relay Operated or restrained by a signal used in conjunction with carrier current or dc pilot-wire fault directional relaying. 86 Locking Out Relay Operated hand or electrically reset, relay that functions to shut down and hold an equipment out of service on the occurrence of abnormal conditions. 87 Differential Protective Relay Functions on a percentage or phase angle or other quantitative difference of two currents or of some other electrical quantities. 88 Auxiliary Motor or Motor Generator Used for operating auxiliary equipment such as pumps, blowers, exciters, rotating magnetic amplifiers etc. 89 Line Switch Used as a disconnecting load interrupter, or isolating switch in an ac or dc power circuit, when this device is electrically operated or has electrical accessories, such as an auxiliary switch, magnetic lock etc.
  • 85. ELECTRICAL DEVICE NUMBERS & FUNCTIONS Training Module: 04.07.01 Issue: A Date: April 2003 Page: 8 of 8 04.07.01 (A) Device Numbers.doc © Brush Electrical Machines Ltd. 2003 Device No. Device Definition and Function 90 Regulating device Regulates a quantity, or quantities, such as voltage, current, power, speed, frequency, temperature, and load, at a certain value or between certain (generally close) limits for machine, tie lines or other apparatus. 91 Voltage Directional Relay Operates when the voltage across an open circuit breaker or contactor exceeds a given value in a given direction. 92 Voltage and Power Directional Relay Permits or causes the connection of two circuits when the voltage difference between them exceeds a given value in a predetermined direction and causes these two circuits to be disconnected from each other when the power flowing between them exceeds a given value in the opposite direction. 93 Field Changing Contactor Functions to increase or decrease in one step value of field excitation on a machine. 94 Tripping or Trip-free relay Functions to trip a circuit breaker, contactor, or equipment, or to permit immediate tripping by other devices; or to prevent immediate reclosure of a circuit interrupter, in case it should open automatically even though its closing circuit is maintained closed. 95 Used only for specific applications on individual installations where none of the assigned numbered functions from 1 to 94 is suitable. 96 Used for `trip circuit supervision' monitoring tripping supplies and (sometimes) circuit continuity 97 Used only for specific applications on individual installations where none of the assigned numbered functions from 1 to 94 is suitable. ►
  • 86. EQUIPMENT & SWITCHGEAR LABELLING Training Module: 04.08.01 Issue: A Date: April 2003 Page: 1 of 6 04.08.01 (A) Switchgear Labelling.doc © Brush Electrical Machines Ltd. 2003 EQUIPMENT & SWITCHGEAR LABELLING
  • 87. EQUIPMENT & SWITCHGEAR LABELLING Training Module: 04.08.01 Issue: A Date: April 2003 Page: 2 of 6 04.08.01 (A) Switchgear Labelling.doc © Brush Electrical Machines Ltd. 2003 CONTENTS 1 INTRODUCTION........................................................................................................................................ 3 2 GENERAL .................................................................................................................................................. 3 3 PREFIX LETTER........................................................................................................................................ 3 4 WIRE NUMBERS....................................................................................................................................... 4 5 SUFFIX LETTERS ..................................................................................................................................... 4 6 NUMBERING TABLE ................................................................................................................................ 4
  • 88. EQUIPMENT & SWITCHGEAR LABELLING Training Module: 04.08.01 Issue: A Date: April 2003 Page: 3 of 6 04.08.01 (A) Switchgear Labelling.doc © Brush Electrical Machines Ltd. 2003 1 INTRODUCTION BS3939 is the Specification for Standard Numbering of Small Wiring for Switchgear and Transformers together with their Associated Relay and Control Panels. 2 GENERAL a) Each wire shall have a letter to denote its function, eg control of circuit breaker, current transformer for primary protection, voltage for instruments, metering and protection. The function letter shall be followed by a number identifying the individual wire. Every branch of any connection shall bear the same identification mark. Where it is necessary to identify branches which are commoned (e.g. current transformer leads), different identification marks for the branches may be employed only if they are commoned through links, or are connected to separate terminals which are then commended by removable connections. Suffix letters shall be used as indicated in Section 5. b) Numbering shall read from the terminals outwards on all wires. ► 3 PREFIX LETTER a) Where part of a circuit is common to more than one function, the first in alphabetical order of the appropriate function letters in the table shall be used for the common part. Where the circuits split as a separate contact (eg fuse, link, switch or relay contact) the function letter shall change if necessary from the splitting point onwards. b) Circuits having functions not included in the function letter table shall not have prefix letters. For example, circuits of devices which provide a continuous indication, such as remote winding temperature indicators or resistance thermometers, shall not have a prefix letter unless the circuit of the particular indication already has a function letter. Where, however, an indication or alarm is initiated by the opening or closing of an auxiliary contact prefix 'L' or 'X' should be used as appropriate. c) Where the manufacturer has been unable to ascertain from the purchaser the function letters and numbering to be assigned to equipment wiring by the time that wiring is required, the manufacturer shall himself provide wire numbers preceded by the letter 'O'. Where the appropriate function letter only can be determined, it shall be preceded by an 'O' and followed by the manufacturers own number. The same procedure my be applied to equipment or parts of equipment not assigned to specific contracts at the time of manufacture, subject to the purchasers approval and to the use of ferruling in accordance with approved standard diagrams as far as these are applicable. d) Where relays are employed, the coil and the contact circuits do not necessarily bear the same function letter; this should be determined by the function of the individual circuit eg the coil circuit of a series flag relay may be 'K' but the contact circuits may bear letters such as 'X', 'L' or 'N' as appropriate. e) The following rules shall apply to current and voltage transformer function letters: i) Current Transformers for Protection Prefix 'C' shall be used for all types of over-current protection (whether used as primary or back-up protection), standby earth fault, generator negative phase sequence, transformer winding temperature protection, and instruments fed from separate current transformer. Where duplicate primary protection is applied prefix 'A' shall be used for both, the second line being distinguished by adding 300 to the number. ii) Interposing and Auxiliary Transformers The function letters shall follow through any interposing and auxiliary current and voltage transformers, including such transformers when used for light current circuits, provided that these are not used as isolating transformers to couple circuits which have differing functions. When an ac supply, reflecting the primary quantities and derived from a current or voltage transformer, is rectified for the operation of instruments or relays, the dc circuit shall carry the same function letter as the ac circuit. iii) Current Transformer Connections for Line Drop Compensation or Compounding Prefix 'D' shall be used for these circuits, including the current side of the isolating transformer. The connections to the voltage circuit from this transformer shall have prefix 'F'.
  • 89. EQUIPMENT & SWITCHGEAR LABELLING Training Module: 04.08.01 Issue: A Date: April 2003 Page: 4 of 6 04.08.01 (A) Switchgear Labelling.doc © Brush Electrical Machines Ltd. 2003 iv) Voltage Transformer Connections for Automatic Voltage Control Prefix 'F' shall be used for these circuits. f) Light current equipment may require numbering schemes differing from the above for complete identification. In such cases, where connections from such equipment are associated with power equipment wired in accordance with this Recommendation, the numbering of such connections shall include the appropriate prefix letter (J, W, X or Y) to distinguish them. The letter 'W' is generally used for the light current side of interposing relays for control purposes. ► 4 WIRE NUMBERS The wire number may consist of one or more digits as required. For functions A-G, H, J and M, the numbers shall be given in the column under 'Wire Numbers'. DC supplies from a positive source shall bear odd numbers and dc supplies from a negative source shall bear even numbers. Where coils or resistors are connected in series the change from odd to even shall be made at the coil or resistor lead nearest to the negative supply. 5 SUFFIX LETTERS Where similarly numbered leads from separate primary equipments are taken to a common panel (eg bus zone protection, summation metering, banked transformers, etc), suffixes A, B and C, etc, should be used to distinguish them. Where similarly numbered leads from different parts of a unit of primary equipment are taken to a common panel (eg generator and unit transformers, HV and LV sides of a transformer, etc), the leads of the subsidiary or lower voltage equipment shall be distinguished by adding 500 to the wire numbers. When more than two sets of leads require to be distinguished, specific wire numbering schemes appropriate to the case shall be issued by means of a standard diagram showing the scheme to be adopted. The method of distinguishing between sets of leads shall be shown on the individual schematic (circuit) and wiring diagrams. The distinguishing suffixes or numbers apply only in the common panel or junction box, and at each end of the interconnecting cores. When specified, however, suffixes may be omitted from the ends of the interconnecting cores. ► 6 NUMBERING TABLE Letter Circuit Function Wire numbers A Current transformers for primary protection excluding overcurrent 10-29 Red Phase 30-49 Yellow Phase 50-69 Blue Phase 70-89 Residual circuits & neutral current transformers 90 Earth wires directly connected to earth bar 91-99 Test windings, normally inoperative B Current transformers for busbar protection C Current transformers for overcurrent protection (including combined earth fault protection) and instruments D Current transformers for metering and voltage control E Reference voltage for instruments, metering and protection F Reference voltage for voltage control G Reference voltage for synchronising H AC and AC/DC supplies 1-69 Switchgear & Generators 70-99 Transformers J DC Supplies 1-69 Switchgear & Generators 70-99 Transformers K Closing & tripping control circuits Any number from 1 upwards
  • 90. EQUIPMENT & SWITCHGEAR LABELLING Training Module: 04.08.01 Issue: A Date: April 2003 Page: 5 of 6 04.08.01 (A) Switchgear Labelling.doc © Brush Electrical Machines Ltd. 2003 Letter Circuit Function Wire numbers L Alarms and indications initiated by auxiliary switches and relay contacts, excluding those for remote selective control and for General Indication equipment Any number from 1 upwards M Auxiliary and control motor devices eg governor motor, rheostat motor, generator AVR control, spring charging motors, transformer cooler motor control, motors for isolator 1-19 Switchgear 20-69 Switchgear 70-99 Transformer N Tap change control, including AVC, tap position and progress indications O An indication that the ferruling is not on accordance with the general scheme and that if it is not altered double ferruling will be required for co- ordination with the remaining equipment in the station (see 1b (3)) Any number from 1 upwards P DC Tripping circuits used solely for busbar protection Any number from 1 upwards R Interlock circuits not covered above Any number from 1 upwards S DC instruments and relays, exciter and field circuits for generators Any number from 1 upwards T Pilot conductors (including directly associated connections) between panels, independent of the distance between them, for pilot-wire protection, for interrupting or for both Any number from 1 upwards U Spare cores and connections top spare contacts Spare cores shall be numbered from 1 upwards in each cable, and shall be so arranged that they can be readily identified on site with the cable containing them. This shall be achieved by suitable grouping, and unless the location of each group is clear from the diagram, the groups shall be labelled. Alternatively the core number shall be preceded by the cable number V Automatic switching circuits not integral with circuit breaker control schemes, ie separately supplied, or isolatable from, the circuit breaker control scheme Any number from 1 upwards W Light current control connections (see rule 1b (6)) Any number from 1 upwards X Alarms and indications to and from General Indication and remote selective control equipments Any number from 1 upwards Y Telephones Any number from 1 upwards ► Notes: If, for functions A-G and for functions H. J and M, more numbers are required, add multiples of one hundred (e.g. 10-29 may be extended to 110-129, 210-229, etc.) The term 'remote selective control' denotes 'control at a point distant from the switchgear by the transmission of electrical signals through common communication channels using selective means to operate one of a number of switching devices'. ►
  • 91. EQUIPMENT & SWITCHGEAR LABELLING Training Module: 04.08.01 Issue: A Date: April 2003 Page: 6 of 6 04.08.01 (A) Switchgear Labelling.doc © Brush Electrical Machines Ltd. 2003 BLANK PAGE
  • 92. HIGH VOLTAGE PHASING CHECKS Training Module: 04.09.01 Issue: A Date: April 2003 Page: 1 of 6 04.09.01 (A) HV Phasing.doc © Brush Electrical Machines Ltd. 2003 HIGH VOLTAGE PHASING CHECKS
  • 93. HIGH VOLTAGE PHASING CHECKS Training Module: 04.09.01 Issue: A Date: April 2003 Page: 2 of 6 04.09.01 (A) HV Phasing.doc © Brush Electrical Machines Ltd. 2003 CONTENTS 1 INTRODUCTION........................................................................................................................................ 3 2 PHASING OUT OF HV SYSTEMS ............................................................................................................ 3 3 PHASING STICKS..................................................................................................................................... 5
  • 94. HIGH VOLTAGE PHASING CHECKS Training Module: 04.09.01 Issue: A Date: April 2003 Page: 3 of 6 04.09.01 (A) HV Phasing.doc © Brush Electrical Machines Ltd. 2003 1 INTRODUCTION The fundamentals of phasing out of high voltage (HV) power systems are detailed hereafter. WARNING: Specialised HV training is required before entering any HV switchgear panels. When synchronising a generator to a busbar system it is imperative to check that the Voltage Transformers (VT's) to the synchronising gear reflect correctly the phase rotation and phase difference between the two systems. Some switchgear breakers have no VT's fitted, these are normally ring main units or auxiliary switchgear. In these situations the only way of checking these is Phasing Sticks (See Section 3). Phase displacements between the output lines of a three phase ac generator are 120 electrical degrees apart. This is to assure power is taken equally during the rotation of the prime mover. These lines can be referred as Red, Yellow, Blue phases, or L1, L2, L3, or R, S, T or U, V, W dependant on which international standard is used. It is important to ensure the order in which the line voltages rise. This defines the phase rotation of the system. With an ac generator the phase rotation is set by the direction of rotation of the prime mover. Nowadays phase rotation is U, V, W irrespective of mechanical rotation for an ac generator. During phasing checks we cannot rely on HV cable core identifications, as any joints in the cable would be carried out to suit the lay of the connectors and not the continuity of the core numbers by the cable jointer. Likewise with the secondary of the VT's the cabling may pass through several interconnecting terminal blocks before arriving to the synchronising instrumentation. ► 2 PHASING OUT OF HV SYSTEMS Before joining two systems the following criteria must be met: 1) Voltages on both systems must be equal. 2) The frequency of both systems should be identical. 3) The phase difference between supplies should be zero. 4) The phase rotation of both supplies should be the same. 5) Vector windings should be identical (Transformer in circuit only). In practice 1) to 3) are unobtainable due to fluctuating site load so there are acceptable limits that will allow the two systems to be joined. Any voltage mismatch will cause reactive currents to flow between the interconnected systems and with any phase difference this creates a mechanical shock to the generator rotor system and therefore the stator assembly. This should be minimised. Any phase displacement between the two systems caused by slip between a generator and a busbar frequency will cause the generator to electrically lock into synchronism the instant the generator breaker is closed. It is normal practice to synchronise with the Prime Mover slightly above synchronous speed, this assures that power is taken up by the set the instant the breaker is closed. This prevents the set tripping out on reverse power. ► Figure 1: Typical Generator To Be Synchronised
  • 95. HIGH VOLTAGE PHASING CHECKS Training Module: 04.09.01 Issue: A Date: April 2003 Page: 4 of 6 04.09.01 (A) HV Phasing.doc © Brush Electrical Machines Ltd. 2003 Figure 1 shows a typical situation where a generator is to be synchronised to a network. Where possible the following procedure should be performed to ensure that the following criteria are met: Ø Phase rotation of the set is correct. Ø The VTs are correctly reflecting the status of the HV system. Ø External wiring to control/synchronising panel is correct. Ø The correct phasing of the incoming machine is correct, ie Red phase to Red phase etc. WARNING: The use of Low Voltage Phase rotation meters on an unexcited HV set is a dangerous practice and should not be performed. The following is a typical exercise to synchronise a machine as shown in Figure 1: 1) Isolate bus coupler and Generator breaker as per current safety rules. Isolate any synchronising breaker signals ensuring that none of the breaker close signal cabling can 'short down' to earthed metalwork. 2) Confirm that three phase VTs are used. Check the earthing of the VT Winding (eg yellow earthed or neutral earthed). Providing VT earthing is identical the following procedure may be followed. 3) Earth bus section as per current safety rules. 4) Isolate and insulate the three machine output cables. If not insulated, remove the generator neutral 'star' connections. Note: Isolate at the machine terminals should it be suspected that due to the age of the machine the ends of the windings been swapped due to stator leakage currents. However not all machines were graded for line voltage to the star point. 5) Remove bus section earthing and return to normal operation with generator leads still isolated and insulated as per current safety rules. 6) Close bus coupler and energise up the RHS busbar. 7) Close Generator breaker. (This is referred to as back-energising the generator). 8) Check and record phase rotation of VT1 (generator). 9) Check and record phase rotation of VT2 (busbar). ► 10) Produce phasing chart as shown in Table 1. Verify the phasing by measuring the VT secondary ac voltages. Verify (if connected) that the synchroscope is reading twelve o'clock and that the check synchroniser unit contacts are closed (if fitted). Table 1: Phasing Chart RHS Voltage Transformer (VT2) VT1 Red Yellow Blue Red Zero 110V 110V Yellow 110V Zero 110V Blue 110V 110V Zero At this stage the phasing of the VT's across the breaker have been prove using the busbar supply. The phase rotation of the running supply has been verified. 11) Isolate bus coupler and generator breaker as per current safety rules. 12) Earth bus section as per current safety rules. 13) Reinstall generator HV cabling. 14) Remove bus section earthing and return to normal operation. 15) Ensure bus coupler is open and locked off 16) Start generator and deadbar. Close generator breaker onto RHS busbar. 17) Check and record phase rotation of VT1 and 2. Ensure that this is the same as in steps 8) and 9) (this proves that the phase rotation of both machine and busbars are the same). 18) Produce phasing chart as shown in Table 1. Verify the phasing by measuring the VT secondary ac voltages. Verify (if connected) that the synchroscope is reading twelve o'clock. At this stage the phasing of the VT's across the breaker have been proven, using the busbar supply. The phase rotation of both the running (busbars) and incoming (generator) supplies are correct. ►
  • 96. HIGH VOLTAGE PHASING CHECKS Training Module: 04.09.01 Issue: A Date: April 2003 Page: 5 of 6 04.09.01 (A) HV Phasing.doc © Brush Electrical Machines Ltd. 2003 3 PHASING STICKS The final check is to verify the HV cabling, this is done using a combination of live line tester with phasing sticks. Refer to the manufacturer's instructions before using this equipment. Figure 2: Phasing Stick Connections► Figure 2 outlines the connection for the equipment. Firstly, using the live line tester only, verify the voltages A1, B1, C1, A2, B2, C2, individually to earth and record in a chart similar to Table 2. Table 2: Voltage Verification Chart Line Voltage 11kV System 13.8kV System 33kV System A1 6.35 * 8 * 19 * B1 6.35 * 8 * 19 * C1 6.35 * 8 * 19 * A2 6.35 * 8 * 19 * B2 6.35 * 8 * 19 * C2 6.35 * 8 * 19 * A1 & A2 12.7 in phase ** 16 in phase ** 38 in phase ** A1 & B2 6.35 ** 8 ** 19 ** A1 & C2 6.35 ** 8 ** 19 ** B1 & A2 6.35 ** 8 ** 19 ** B1 & B2 12.7 in phase ** 16 in phase ** 38 in phase ** B1 & C2 6.35 ** 8 ** 19 ** C1 & A2 6.35 ** 8 ** 19 ** C1 & B2 6.35 ** 8 ** 19 ** C1 & C2 12.7 in phase ** 16 in phase ** 38 in phase ** * Phase to neutral volts = Line Volts √3 ** Volts on phasing sticks when in synchronism = 2 x Line Volts √3 Connect up the phasing sticks and now verify the remaining readings between incoming and running phases. Ensure that the reference synchroscope is reading 12 o'clock by trimming the incoming machines governor. When all readings are acceptable synchronising is permissible. ►
  • 97. HIGH VOLTAGE PHASING CHECKS Training Module: 04.09.01 Issue: A Date: April 2003 Page: 6 of 6 04.09.01 (A) HV Phasing.doc © Brush Electrical Machines Ltd. 2003 BLANK PAGE
  • 98. ELECTRICAL POWER Training Module: 04.10.01 Issue: A Date: April 2003 Page: 1 of 16 04.10.01 (A) Electrical Power.doc © Brush Electrical Machines Ltd. 2003 ELECTRICAL POWER
  • 99. ELECTRICAL POWER Training Module: 04.10.01 Issue: A Date: April 2003 Page: 2 of 16 04.10.01 (A) Electrical Power.doc © Brush Electrical Machines Ltd. 2003 CONTENTS 1 RESISTANCE, INDUCTANCE & CAPACITANCE ................................................................................... 3 1.1 Resistance........................................................................................................................................... 3 1.2 Inductance........................................................................................................................................... 3 1.3 Capacitance ........................................................................................................................................ 4 2 CURRENT & VOLTAGE............................................................................................................................ 5 3 ACTIVE POWER........................................................................................................................................ 8 4 REACTIVE POWER................................................................................................................................. 10 5 POWER FACTOR & APPARENT POWER............................................................................................. 10 6 THREE PHASE POWER ......................................................................................................................... 15 7 TARIFFS AND POWER FACTOR CORRECTION ................................................................................. 15
  • 100. ELECTRICAL POWER Training Module: 04.10.01 Issue: A Date: April 2003 Page: 3 of 16 04.10.01 (A) Electrical Power.doc © Brush Electrical Machines Ltd. 2003 1 RESISTANCE, INDUCTANCE & CAPACITANCE 1.1 Resistance Ohm's Law establishes that the relationship between voltage and current in a simple dc circuit is constant i.e. V/I = Constant. During Ohm's experiments he found that this constant varied from sample to sample. The ratio V/R is called 'resistance' or R, which in electrical terms can be considered as opposition to flow of electrons. In a mechanical analogy, electrical resistance is like friction. Resistance is present in all ac electrical circuits. The amount of resistance is usually relatively small, but can be high in devices such as heaters etc. and are referred to as 'resistive' loads. ► 1.2 Inductance Wherever a magnetic field is produced by an electric current passing through a circuit, that circuit displays the phenomenon of 'inductance'. A mechanical analogy would be a large grindstone with a turning handle. Because it is old its bearings are stiff and rusty, giving a lot of friction. When we try to turn the handle, we must overcome this friction, causing heat and loss of energy at the bearings and making ourselves hot with the effort expended. Figure 1: Grindstone Analogy Since the grindstone is heavy, in addition to friction we also need to overcome its inertia in order to provide the wheel with an accelerating force for it to gather speed. The greater the weight or inertia, the greater the force needed to accelerate. An electric circuit exhibits the same effects. It has resistance (friction in the mechanical analogy), and, in order for a current to flow, a pressure in the form of a voltage is needed to overcome it (our efforts in the mechanical analogy). An electrical circuit has inertia too. It opposes any attempt to speed up the current or to cause it to grow. This inertia in an electrical circuit is called 'inductance' and is due to the fact that any electric current causes magnetisation. This effect is greatly increased by the presence of iron for example (which magnetises easily). ►
  • 101. ELECTRICAL POWER Training Module: 04.10.01 Issue: A Date: April 2003 Page: 4 of 16 04.10.01 (A) Electrical Power.doc © Brush Electrical Machines Ltd. 2003 Figure 2: Electromagnetic Induction Faraday's Law of Electromagnetic Induction states that, if a conductor moves in a magnetic field, an emf (or electro-magnetic force or voltage) is induced in it. The opposite is also true i.e. an electric current in a wire gives rise to a magnetic field along its axis (Oersted's Principle). To explain how inductance arises in a circuit due to its magnetisation, which causes it to display electrical inertia or 'sluggishness', can be explained by the following example. Consider a coil of wire through which a current is flowing, there is a magnetic field concentrated along its axis. If the current increases, then the magnetic field also increases which, by Faraday's Law induces creates an emf (voltage) in each turn. The direction of the emf would be such as to oppose the change i.e. in this case to try to prevent the current increasing, and is therefore often referred to as the 'back-emf'. Circuits incorporating equipment that have coils, especially those with iron such as generators, motors and transformers, have both resistance and inductance. They are generally referred to as 'inductive' loads. ► 1.3 Capacitance Capacitance in electrical terms is the ability to store energy. This should not be confused with the word 'capacity'. Care is needed to distinguish between 'capacitance' and, 'capacitor' which is a device for storing energy. A mechanical analogy of an electric capacitor would be a large, closed tank filled with water, fitted with a flexible membrane down the middle, and fitted a pressurised water supply on one side and a suction outlet on the other side. Figure 3: Water Tank Analogy
  • 102. ELECTRICAL POWER Training Module: 04.10.01 Issue: A Date: April 2003 Page: 5 of 16 04.10.01 (A) Electrical Power.doc © Brush Electrical Machines Ltd. 2003 Initially, with the valve closed both sides of membrane are at equal pressure and the membrane is undistorted. When the valve is opened water under pressure flows into the right hand side of the tank and out through the left side. Water movement through the tank itself compared to the flow through the pipes is small compared to the large cross-section of the tank, hence the membrane will distort right to left as illustrated in Figure 3. Eventually when the distortion is such as to produce a pressure equal to the incoming water, water flow will cease, and the membrane will be in a state of elastic strain. Closing the valve at this point, the right hand side of the tank is under pressure with static energy stored in the stretched elastic membrane. Although water can move through the external piping, there is no transfer of water within the tank across the membrane. In an electric capacitor, the current entering one side and leaving the other side is the 'charging current', which is like the water flow in the pipes in the water tank analogy. In the water tank, reversing the process would cause the stretched membrane to relax or release the static energy. Similarly passing a current into a capacitor 'discharges' it and recovers the stored energy or capacitance. Examples of 'capacitive' loads are obviously capacitors, overheads lines and some long, straight cable runs. ► 2 CURRENT & VOLTAGE For a simple dc circuit that is purely resistive, Ohm's Law states that V/I = R (Voltage/Current = Resistance), i.e. the relationship between voltage and current is constant. In an ac circuit this constant relationship is illustrated in Figure 4. Figure 4: Resistive Load Waveforms When the circuit is switched on, the voltage and current waveforms coincide and are said to be 'in phase'. In an inductive dc circuit however the current rises slowly at first since the applied voltage is overcoming the 'back-emf', or inertia of the system to make the current grow. This characteristic has a significant effect on the voltage-current waveform relationship in a purely inductive ac circuit. ►
  • 103. ELECTRICAL POWER Training Module: 04.10.01 Issue: A Date: April 2003 Page: 6 of 16 04.10.01 (A) Electrical Power.doc © Brush Electrical Machines Ltd. 2003 Figure 5: Inductive Load Waveforms In Figure 5 the switch in a purely inductive ac circuit is closed when the voltage wave is at the positive peak. Because the load is inductive, the first application of voltage will cause the current to rise slowly, and it will continue to rise in this manner until 'A', by which time the voltage wave has fallen to zero. At this point there is no more voltage drive and the current ceases to rise i.e. maximum positive 'P'. After this point the voltage becomes increasingly negative, opposing the current flow and causing the current to reduce. During the times 'B' and 'C' the voltage is negative, so the current becomes increasingly negative. After 'C' the voltage passes through zero, and with no voltage drive the current ceases to decrease i.e. maximum negative 'Q'. During time 'D' the voltage becomes positive again, opposing the current's negative flow. The current becomes less negative and returns to zero at 'D' when the voltage is at its positive maximum. The condition at 'D' is the same as the start time 'O' and the whole cycle begins again. It can be seen from Figure 5 that the current wave is 'late' compared to the voltage wave by one quarter of a cycle. It is said to 'lag'. If one cycle is 360 o , the current waveform lags the voltage waveform by 90 o . In a capacitive dc circuit a charging current is set up as the voltage is applied, and the growing charge on the capacitor increasingly opposes the applied voltage until the charging current has decayed and ceased. The effect of this characteristic in a capacitive ac circuit on the voltage-current waveform relationship is illustrated as follows. ►
  • 104. ELECTRICAL POWER Training Module: 04.10.01 Issue: A Date: April 2003 Page: 7 of 16 04.10.01 (A) Electrical Power.doc © Brush Electrical Machines Ltd. 2003 Figure 6: Capacitive Load Waveforms In Figure 6(a) the ac charging current is considered to be square shaped instead of the classical sine- wave shape. Between 'A' to 'B' the charging current is constant and positive and the capacitor is charging at a constant rate. At the same time its charge voltage Ec , which is opposing the applied voltage V, is decreasing negatively to its negative maximum at 'P'. At this point the applied voltage V is at its maximum positive. Between 'B' and 'D' the charging current has reversed and is constant and negative and the capacitor is discharging at a constant rate. At the same time its charge voltage Ec , which is opposing the applied voltage V, is increasing positively to its positive maximum at 'Q'. At this point the applied voltage V is at its maximum negative. At 'C' the capacitor has no charge. From 'D' to 'E' the charging current is once again constant and positive, and its charge voltage Ec is decreasing negatively towards its negative maximum, passing through zero at 'E'. Beyond this point the conditions are the same as the start and the whole cycle begins again. For the purpose of explanation a square shaped charging current was assumed. This would not the case in practice where the charging current wave would normally be a sine-wave. In Figure 6(a) the square topped and angled lines are 'rounded off' implying a gradual rather than a sudden change, which approaches the sine-wave shapes shown in Figure 6(b). From Figure 6(b) it will be noted that the current I is ahead in time of the applied voltage V, and the current is said to 'lead' the applied voltage. If one cycle is 360 o , the current waveform leads the voltage waveform by 90 o . ►
  • 105. ELECTRICAL POWER Training Module: 04.10.01 Issue: A Date: April 2003 Page: 8 of 16 04.10.01 (A) Electrical Power.doc © Brush Electrical Machines Ltd. 2003 Figure 7: Inductive & Capacitive Currents Figure 7 illustrates on the same diagram how inductive circuit currents lag the applied voltage by 90 o and how capacitive circuit currents lead by 90 o . It will be noted that since each current is displaced 90 o either side of the voltage wave, there is 180 o between them, or in other words inductive and capacitive current waves are exactly opposite to each other in phase. Convention considers that capacitive loads 'supply' current , whilst inductive 'take' current, which is important to remember since most practical circuits are a combination of capacitive, inductive and resistive loads. ► 3 ACTIVE POWER The purpose of most electrical systems is to generate electrical power and to convey it to those consumer installations which will use it. When an electric generator is delivering this energy, or the rate of delivering 'real' power, it is at the same time usually delivering another type of 'false' energy which may also be required by certain consumer equipment. To distinguish between them, 'real' power, which represents real energy, is called 'active power' (sometimes also called 'wattful', 'actual', 'true', 'real' or 'working' power). The other kind, which is the rate of delivering 'false' energy, is termed 'reactive power' (sometimes also called 'wattless' or 'blind' power). 'Reactive' power is dealt with separately in Section 4. 'Active' power may be used to energise a mechanical drive, or to provide heating and lighting, or to energise control and communication systems such as instrumentation or radio and telephone installations. All of these things consume energy, and that energy is absorbed at a stated rate i.e. power consumption. 'Real' power consumption is measured in 'watt' (W), kilowatt (kW) - one thousand watts, or megawatt (MW) - one million watts. Electric power is usually obtained from a generator, which receives its power from a prime mover (engine - petrol, diesel or gas; turbine - gas, steam, water or wind). With the exception of water and wind driven sets, the energy delivered by the prime mover to the generator is derived from the fuel which they burn i.e. the energy source is ultimately a chemical one. Voltage is a pressure, and current is a flow. In mechanical engineering, power -the rate of doing work - is the product of pressure and volume flow. In electrical circuits, power is the product of voltage and current i.e. Power = V x I. If V is measured in volts and I in amps, their product is the power in watts (W). In dc this presents no problem. Both V and I are steady quantities and their product is a direct measure of the power in watts. With ac however the same rule applies, but these quantities are constantly changing as the voltage and current alternate. It is therefore necessary to look at this product instant by instant to see if it has an average value. ►
  • 106. ELECTRICAL POWER Training Module: 04.10.01 Issue: A Date: April 2003 Page: 9 of 16 04.10.01 (A) Electrical Power.doc © Brush Electrical Machines Ltd. 2003 Figure 8: AC Power - Resistive Load Consider an ac voltage feeding a purely resistive load. If the top wave of Figure 8 represents the voltage, the second wave represents the current is in phase with the voltage. The power at any instant is the product of the voltage and current at that instant. At t0, t4 and t8 both waves are at zero, so their product is also zero. At any time in the first half-cycle voltage and current are both positive, so their product is also positive, and is greatest at time t2, where both are at their maximum. At any time in the second half-cycle voltage and current are both negative, so their product is again positive and is greatest at t6, where both are at their negative peaks. The power wave is therefore the bottom waveform in Figure 8. It is of double frequency i.e. two peaks for every one voltage peak) and is wholly above the line (positive). It represents pulses of power, always positive, and the average value of that power is midway between the power peaks and troughs. In this case, for a purely resistive load the average, or mean (peak to peak) power P = V x I (watts) and is the 'active' or 'true' power, and is the same as in a similar dc circuit. 'Active' power is measured by a wattmeter, which automatically calculates the value of 'real' power in the ac (or dc) circuit. ►
  • 107. ELECTRICAL POWER Training Module: 04.10.01 Issue: A Date: April 2003 Page: 10 of 16 04.10.01 (A) Electrical Power.doc © Brush Electrical Machines Ltd. 2003 4 REACTIVE POWER Figure 9: AC Power - Pure Inductive Load Figure 9 shows waveforms for a purely inductive load, in which the current 'lags' the voltage by 90 o . Using the same principles as before to determine the instantaneous values of the product of current and voltage, results in the 'active power' waveform shown at the bottom of Figure 9. Because of the 'phase- shift' between current and voltage, the average, or mean (peak to peak) value of 'active power' is zero. Similarly, for a purely capacitive load, in which the current 'leads' the voltage by 90 o , the average, or mean (peak to peak) value of 'active power' will also be zero. If there is nett power in a purely resistive ac load only, there is a need to reconsider the rules for determining power for the more usual ac loads that include inductive, capacitive and resistive elements, since simple multiplication of current and voltage values do not represent the 'true' power in watts. ► In circuits incorporating inductive and/or capacitive elements i.e. non-pure systems, the product of voltage and current is known as 'Reactive' or 'Wattless' or 'False' or 'Blind' power is measured in VAr (volt-amp reactive), and is a measure of the energy stored (but not consumed) in a magnetised system. In installations that incorporate transformers and motors, which all need to be magnetised, the demand for VAr's can be considerable 'Reactive' power is measured by a varmeter, which automatically calculates the value of 'reactive' power in an ac circuit. ► 5 POWER FACTOR & APPARENT POWER Only power in purely resistive and purely reactive (inductive and capacitive) circuits has been considered so far. Figure 10 shows the general case for a more typical circuit incorporating both resistive and inductive elements.
  • 108. ELECTRICAL POWER Training Module: 04.10.01 Issue: A Date: April 2003 Page: 11 of 16 04.10.01 (A) Electrical Power.doc © Brush Electrical Machines Ltd. 2003 Figure 10: AC Power - General Case The resistive part of the load draws in-phase current, and the reactive part a current lagging 90 o . Between them they draw a single current somewhere between in-phase (0 o lag) and 90 o lag, as shown on the second curve. The actual phase angle between current and voltage is usually written φ (Greek 'phi' for 'phase'). If the same process is used, as before, of multiplying the voltage by the current at each instant of time, the power wave produced (bottom of the figure) would again be double-frequency but will now be partly asymmetrical, and its average value will be positive and will lie somewhere above the zero line. This means that, in the general case, the average active power (watts) will always be less than the maximum value which occurs in the purely resistive case, where the nett power is V x I watts. Because in the early days of electricity power was always the simple product of V and I, which is correct for dc circuits, a correcting factor was introduced for power in ac circuits. This correcting factor was given the name 'power factor' ('PF') and is the cosine (cos) of 'phase difference' angle between the current and voltage. Thus for an ac circuit nett power is V x I x cosφ. For ac circuits incorporating capacitive elements, where the current 'leads' the voltage i.e. opposite or 'negative' compared to inductive loads, the nett power formula above is still valid since for a particular angle, the cosine for a positive or negative angle is the same. ►
  • 109. ELECTRICAL POWER Training Module: 04.10.01 Issue: A Date: April 2003 Page: 12 of 16 04.10.01 (A) Electrical Power.doc © Brush Electrical Machines Ltd. 2003 Watts and VAr can be drawn as vectors. VAr is drawn at right angles to W and is the measure of 'Reactive' power. The vectorial summation of W and VAr is known as 'Apparent' or 'Total' power which is measured in volt-amperes (VA or kVA or MVA). The angle between Watts and VA, φ or Φ, is the power factor angle, which has the same value as the phase difference angle between the current and voltage (See Figure 11). Figure 11: Power Vectors (Lagging PF) The power factor (cosΦ) can be calculated by dividing the real power (W) by the apparent power (VA) i.e. cosΦ = Real Power/Apparent Power = W/VA. Figure 11 shows a lagging power factor and the VAr's are called lagging VAr's. It is also possible to have a load with a leading power factor as shown in Figure 12. Figure 12: Power Vectors (Leading PF) ► By convention, lagging VAR's are considered to be positive, whilst leading VAR's are considered to be negative. It is common to say that a generator is operating at a certain power factor, say 0.8 lagging, yet in all cases, it is the load determines the power factor. If for example you are operating an isolated system (like an isolated oil rig) with just one generator then the generator’s power factor must be the same as that of the load. If there were two generators, it would be possible to run each at a different power factor but the combined power factor would, as before, be the same as that of the load. Figure 13 shows how the diagrams for the two generators can be combined. ►
  • 110. ELECTRICAL POWER Training Module: 04.10.01 Issue: A Date: April 2003 Page: 13 of 16 04.10.01 (A) Electrical Power.doc © Brush Electrical Machines Ltd. 2003 Figure 13: Power Vectors (Two Generators) If one generator is being operated in parallel with the National Grid then the whole National Grid load still sets the power factor, but any individual generator can be operated at any power factor because it so relatively small. It is only the total system Watts and VAr's that is fixed. It can be seen from Figure 13 that it is permissible to add and subtract Watts, and to add and subtract VAr's. Adding and subtracting VA's however produce a non-meaningful result. ► Figure 14: Power Factor Meter Power factor meters as shown in Figure 14, are calibrated to read cos φ and always show a positive number but are arranged to indicate lagging or leading power factors. ► It is often convenient for operators to consider 'active' and 'reactive' power separately, though in practice both are present together, travel down the same cables and wires, and are produced by the same generator.
  • 111. ELECTRICAL POWER Training Module: 04.10.01 Issue: A Date: April 2003 Page: 14 of 16 04.10.01 (A) Electrical Power.doc © Brush Electrical Machines Ltd. 2003 Figure 15: Active & Reactive Motor Power Figure 15 shows how active and reactive power to a motor is generated, distributed and consumed. Active or 'true' power originates from the generator's prime mover as mechanical output from the turbine. On the other hand reactive power emanates from the generator's excitation system through its main field. Both powers come from the generator itself through a common cable. At the switchboard they give a common current indication on the generator ammeter, and both combine to give a common power factor indication. They separate to give independent wattmeter and varmeter indications. They recombine to feed the motor through a common cable. At the motor the reactive power is used to magnetise the machine, and the active power supplies the (variable) mechanical load and also the losses. ►
  • 112. ELECTRICAL POWER Training Module: 04.10.01 Issue: A Date: April 2003 Page: 15 of 16 04.10.01 (A) Electrical Power.doc © Brush Electrical Machines Ltd. 2003 6 THREE PHASE POWER Consider a three phase system incorporating a star-connected three phase generator connected to a three phase star connected load as shown in Figure 16. The load is 'balanced' consequently the neutral current is zero. Figure 16: Three Phase System Each of the three phases are considered separately, with each generator winding having a phase voltage e.g. VR, developed in it. Because the load is balanced, the line current in each phase is the same e.g. IL = IR an so on. The active power transmitted in each phase is: VR x IL x cos φ thus the total for all three phases is: 3 x VR x IL x cos φ The line-to-line voltage VL , is √3 x Phase voltage, e.g. √3 x VR, thus the total power three phase active power is: P = √3 x VR x IL x cos φ watts The above formula is correct for whether the source or load is star or delta connected. ► 7 TARIFFS AND POWER FACTOR CORRECTION Installations where some or all of the electrical power is imported will be subject to a charge or tariff for the provision of this power by the supply Authority or Utility. This tariff will in general be in two parts - one based solely on the energy consumed to meet the suppliers fuel and other running costs, the second part of the tariff is required to meet each consumer's contribution to the suppliers capital costs which relate to the provision and ongoing repair/replacement of generating and distribution plant. To meet suppliers fuel and running costs, the consumer is provided with a meter which records the total energy consumed in kWh (kilowatt-hours) or MWh (megawatt-hours) and is charged at the appropriate rate per 'unit' (kWh or MWh). This is usually the only charge for domestic installations, which are essentially resistive loads.
  • 113. ELECTRICAL POWER Training Module: 04.10.01 Issue: A Date: April 2003 Page: 16 of 16 04.10.01 (A) Electrical Power.doc © Brush Electrical Machines Ltd. 2003 To meet the suppliers capital costs, which is a reflection of the generation capacity that needs to be installed, the tariff is based on a comparison of the consumers expected maximum load (stated by the consumer prior to commencement of the supply contract) and the actual maximum load in kVA i.e. 'Maximum Demand kVA'. In practice maximum demand is not measured at any given instant, but is averaged over successive periods of (usually) 30 minutes. To limit this part of the payment it is in the consumers interest to limit the magnitude of kVA demand to the stated expected maximum load, or below. To achieve this it is good practice to operate plant as efficiently as possible, which in electrical terms means operating equipment at the best power factor to produce the lowest kVA demand as explained below. ► Figure 17: Power Factor Correction Figure 17 shows a typical power vector diagram for an inductive load e.g. an induction motor. It will be noted that for a given power rating W, the VAr reduces from VAr1 to VAr2 as the power factor improves from φ1 to φ2, and there is a resultant reduction in the VA value (VA2 compared to VA1). When W and VA are equal the VAr value is zero and the power factor angle φ is 1.0 or Unity. Power factor improvement is often achieved by the introduction of special power correction equipment into the system, which incorporates capacitors which have a leading VAr characteristic. Usually systems are operated slightly under-corrected i.e. the power factor is less than unity, since the extra maximum demand amount remaining is small compared to the cost of extra capacitance required to achieve full correction. It will be noted that it is also possible to over-correct the power factor such that a leading reactive power (VAr) element is present, but this is not usual since the reactive power element will increase the value of the apparent power or maximum demand VA. Generally, where practical and safe, electrical equipment should be operated at full load since most equipment is designed to operate at it's most efficient at full load. Operating at part load can be inefficient and may result in a poor power factor that may have an impact on the overall plant maximum demand kVA. ►
  • 114. PRISMIC POWER MANAGEMENT SYSTEM (PMS) Training Module: 07.01.03 Issue: A Date: July 2003 Page: 1 of 6 07.01.03 (A) PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2003 PRISMIC POWER MANAGEMENT SYSTEM (PMS)
  • 115. PRISMIC POWER MANAGEMENT SYSTEM (PMS) Training Module: 07.01.03 Issue: A Date: July 2003 Page: 2 of 6 07.01.03 (A) PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2003 CONTENTS 1 INTRODUCTION........................................................................................................................................ 3 2 APPLICATIONS......................................................................................................................................... 4 2.1 Industrial.............................................................................................................................................. 4 2.2 Offshore............................................................................................................................................... 4 2.3 Marine ................................................................................................................................................. 4 2.4 Dockyards ........................................................................................................................................... 4 3 FEATURES ................................................................................................................................................ 4 3.1 Governor And AVR Adjustment .......................................................................................................... 4 3.2 Generator Set Management................................................................................................................ 5 3.3 Load Shedding .................................................................................................................................... 5 3.4 Other Features .................................................................................................................................... 5
  • 116. PRISMIC POWER MANAGEMENT SYSTEM (PMS) Training Module: 07.01.03 Issue: A Date: July 2003 Page: 3 of 6 07.01.03 (A) PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2003 1 INTRODUCTION PRISMIC PMS is a rack mounted microprocessor system with interface modules specifically designed for power system control and load shedding applications. Figure 1: PRISMIC PMS System The racks and associated equipment are fitted into a panel incorporating a touch screen human machine interface (HMI). Figure 2: PRISMIC Touch Screen HMI PRISMIC PMS offers a number of benefits for the operator of any power generation system including: Ø Improved supply security Ø Reduced manning levels Ø Optimum usage of plant Ø Power system data gathering Since installation of the first system in 1980, PRISMIC PMS power management systems have been commissioned in diverse installations around the world. During this time continuous improvement and introduction of new technologies have been combined with generator applications experience to produce a mature and highly capable product. The user need have no specialist knowledge of PLC programming as PRISMIC PMS is supplied complete with software to suit the site power system configuration. The functionality of each system is verified using a power system simulation thus eliminating extensive on-site programming. ►
  • 117. PRISMIC POWER MANAGEMENT SYSTEM (PMS) Training Module: 07.01.03 Issue: A Date: July 2003 Page: 4 of 6 07.01.03 (A) PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2003 2 APPLICATIONS 2.1 Industrial Large industrial sites such as paper mills and petrochemical refineries, small to medium sized utility power stations, water utilities, banks, airports, universities, sports stadia and other large public buildings all require secure power generation systems. Different modes of operation are available, such as grid target power and power factor or generator base output 2.2 Offshore Figure 3: Offshore Installation Oil and gas installations, often in remote locations, demand a substantial and secure electrical power system. PRISMIC PMS provides fast acting load shedding to prevent cascade failure in the event of unscheduled loss of generating plant. Plant personnel levels can be reduced by enabling automatic start/stop facilities to operate, initiated by changes in load demand. 2.3 Marine Many vessels operate on the electric ship principle with propulsion and all other electric loads supplied from a common electrical power source. This gives flexibility of operation, distribution of plant weight and improved manoeuvrability. For marine systems the PRISMIC PMS control requirements are similar to offshore applications except that the load profiles can be erratic. Specialist applications include: electrical propulsion, thruster control, synchronous compensator control and interface to dynamic positioning systems. 2.4 Dockyards Where grid/utility supplies are 50Hz then frequency changer sets are used to provide 60Hz supplies for moored ships or submarines. PRISMIC PMS has been used to control these systems by making adjustments to AVR setpoints and stator racking gear to facilitate power sharing. ► 3 FEATURES The following features can be incorporated into the PRISMIC PMS system: 3.1 Governor And AVR Adjustment Governor and AVR setpoints of each on line generator are adjusted to provide the following control features: Ø Frequency and Voltage Control: of islanded power systems. (For systems not connected to another virtually infinite power system). Ø Generator MW and MVAr Load Control: PRISMIC PMS may be configured for power sharing where load is evenly distributed according to the capability of each generator. Other modes of control such as MW target, power factor target and temperature derating are also available. Ø Grid/Utility MW and MVAr Load Control: By generator load adjustment, the PRISMIC PMS controls the import or export of power from a grid or utility.
  • 118. PRISMIC POWER MANAGEMENT SYSTEM (PMS) Training Module: 07.01.03 Issue: A Date: July 2003 Page: 5 of 6 07.01.03 (A) PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2003 3.2 Generator Set Management Starting and or stopping of generator sets as follows: Ø Automatic initiation of generator starting and stopping as site load increases and decreases. Algorithms based upon load demand, tariff agreements or detection of failure of a grid/utility supply may be implemented as required. Ø Operator request via PRISMIC PMS HMI or DCSISCADA: may be used to initiate starting and stopping after appropriate checks have been made by PRISMIC PMS. Engine start and stop signals may be issued by the PRISMIC PMS. Generator synchronising equipment may be included with the PRISMIC PMS if needed. Governor and AVR adjustments are normally used to provide load take-up for starting generators and offloading before breaker open signals are issued and engines stopped. 3.3 Load Shedding Selected load feeder breakers are opened by the PRISMIC PMS during fault conditions to avert a cascade failure of the power system. This is typically initiated by the following conditions: Ø System Under Frequency: Causes shedding of site adjustable blocks of load feeders. Ø Sudden Loss of Generating Capability: If the remaining on-line generators are overloaded, fast acting shedding occurs. Ø Gradual Overload of Generators: If the on-line generators are overloaded for a period of time related to the magnitude of the overload, then gradual overload shedding occurs. Ø Other Fault Monitoring: may be used by PRISMIC PMS to initiate shedding as necessary. Priorities are site adjustable to suit operating conditions. Load shedding uses intelligent algorithm so that only sufficient load feeders are removed to avoid generator overload resulting in maximum continuous use of plant. ► 3.4 Other Features Ø Load Feeder Inhibition: Starting of certain load feeders may be inhibited when the on-line generators have insufficient capability. Ø Load Reconnection: When the on-line generators have sufficient capability, load feeders may be automatically re-closed in a controlled manner after load shedding. Ø Controlled Load Reduction: To avoid the need for load shedding, it is sometimes possible to reduce load by reduction of thruster pitch or phasing back variable speed drives whilst further generators are started. Ø Operator Control via HMI: Control modes and target levels may be changed and various circuit breakers opened and/or closed via the HMI. For critical actions the PRISMIC PMS makes appropriate checks before execution. Ø Data Transfer to DCS/SCADA Systems: PRISMIC PMS may be configured to communicate with many different systems providing overall plant monitoring. PRISMIC PMS control sequences and target value changes may be initiated from the DCS/SCADA system. Ø On Line Support: A modem may be fitted to the PRISMIC PMS HMI to facilitate remote fault diagnosis by engineers at Brush in Loughborough. ►
  • 119. PRISMIC POWER MANAGEMENT SYSTEM (PMS) Training Module: 07.01.03 Issue: A Date: July 2003 Page: 6 of 6 07.01.03 (A) PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2003 BLANK PAGE
  • 120. STABILITY CONTROLS USING KEYBOARD ENTRY (PRISMIC 'B') Training Module: 07.05.02 Issue: A Date: July 2003 Page: 1 of 6 07.05.02 (A) Stability Controls B.doc © Brush Electrical Machines Ltd. 2003 STABILITY CONTROLS USING KEYBOARD ENTRY (PRISMIC 'B')
  • 121. STABILITY CONTROLS USING KEYBOARD ENTRY (PRISMIC 'B') Training Module: 07.05.02 Issue: A Date: July 2003 Page: 2 of 6 07.05.02 (A) Stability Controls B.doc © Brush Electrical Machines Ltd. 2003 CONTENTS 1 INTRODUCTION........................................................................................................................................ 3 1.1 General................................................................................................................................................ 3 1.2 Keyboard Adjustable Presets.............................................................................................................. 3 1.3 Site Adjustable Controls...................................................................................................................... 3 2 ACTIVE POWER SHARING (MW) COMMISSIONING............................................................................. 3 3 REACTIVE POWER SHARING (MVAR) COMMISSIONING.................................................................... 4 4 CONNECTING TO THE GRID NETWORK ............................................................................................... 5 5 AFTER COMMISSIONING ........................................................................................................................ 5
  • 122. STABILITY CONTROLS USING KEYBOARD ENTRY (PRISMIC 'B') Training Module: 07.05.02 Issue: A Date: July 2003 Page: 3 of 6 07.05.02 (A) Stability Controls B.doc © Brush Electrical Machines Ltd. 2003 1 INTRODUCTION 1.1 General Stability controls are provided in the PRISMIC system to allow prime movers and generators of different sizes and governor and AVR characteristics to operate when connected in parallel on the same power system. For example consider two paralleled generators, the first being a large gas turbine and the other being a small standby diesel. In a situation arise where the two sets are required to share power, a long governor raise signal on the turbine could 'swamp' the power on the small set possibly causing it to trip out on the generator reverse power protection system. 1.2 Keyboard Adjustable Presets The presets are adjusted using the Man Machine Interface (MMI) keyboard. These are stored within battery back-up RAM or 'flash' ROM on the PRISMIC central processor card. Should this memory be corrupted, back-up 'safe' settings are substituted which are held in EPROM. 1.3 Site Adjustable Controls The PRISMIC 'B' system incorporates site adjustable controls which effectively set the governor/AVR pulse lengths 'ON' and 'OFF' times to maintain system stability whilst compensating for frequency and voltage fluctuations on the power system, and correcting active and reactive power sharing errors between interconnected generating packages. Voltage, frequency, power and reactive deadband controls are provided to prevent system instability and 'nuisance pulses' emanating from the AVR and governor control relays. The PRISMIC system uses proportional control to control both the AVR and governors on the generation packages. Figure 1 shows a typical train of control pulses. Figure 1: Typical Train Of Control Pulses The slug period is defined as the period between successive pulses. The slug duration (which is adjustable between zero and 25.5 seconds) is fixed during commissioning to obtain optimum stability within the control system. Since the AVR and governor response times are slow, the slug period allows a 'settling' time for the system to respond to the pulse before proceeding with the next control signal. 2 ACTIVE POWER SHARING (MW) COMMISSIONING On an islanded system (i.e. the machines are not connected to a grid network) the governor pulse has to compensate for any imbalance in the active power sharing (MW) between interconnected sets and any frequency fluctuations on the system. The greater the error of these two parameters the larger the control pulse. A Frequency Error is defined as the difference between the PRISMIC frequency set pointed and the actual bus frequency. The Power Sharing Error is the difference between the actual MW on the generating package and the target MW value based on the total load on the bus and the actual MW capacity of the prime mover and the number of sets on the bus.
  • 123. STABILITY CONTROLS USING KEYBOARD ENTRY (PRISMIC 'B') Training Module: 07.05.02 Issue: A Date: July 2003 Page: 4 of 6 07.05.02 (A) Stability Controls B.doc © Brush Electrical Machines Ltd. 2003 Where a set is connected to a grid system, then as the frequency remains constant, only the target MW error is accounted for. A governors signal duration is calculated by: Signal Duration = Frequency Error + MW Sharing Error Frequency Attenuation MW Attenuation The greater the attenuation (adjustable between 0 and 15) the smaller the pulse length. Stable frequency control is verified by either adjusting the PRISMIC frequency set point datum or placing load on the system. With stable frequency control, the power sharing commissioning may commence: 1) Reduce the power sharing deadband and adjust the power sharing attenuation preset for optimum stability. 2) Place a set in manual control and increase the governor datum on that set, return the set back to PRISMIC control. This should result in stable operation. As the interconnected sets are in droop control, power sharing due to load fluctuations is taken care of by the governors and the power sharing control only comes into play when a set is being introduced onto the busbars. Various permutations of sets should be tried to prove stability. 3 REACTIVE POWER SHARING (MVAR) COMMISSIONING After successful commissioning of the power/frequency control, the voltage and reactive (VAr) power sharing should commence. Ø Re-install the voltage control relays but isolate the governor control relays. Ø During AVR commissioning maintain system frequency and power sharing between on-line sets manually. On an islanded system (i.e. the machines are not connected to a grid network) the AVR pulse has to compensate for any imbalance in the reactive power sharing (MVAr) between interconnected sets and any voltage fluctuations on the system. The greater the error of these two parameters the larger the control pulse. A Voltage Error is defined as the difference between the PRISMIC voltage point and the actual bus voltage. The Reactive Power Sharing Error is the difference between the actual MVAr on the generating package and the target MVAr value based on the total load on the bus and the actual MVA capacity of the prime mover. Where a set is connected to a grid system then as the voltage remains constant, only the target MVAr error is accounted for. An AVR signal duration is calculated by: Signal Duration = Voltage Error + MVAr Sharing Error Voltage Attenuation MVAr Attenuation The greater the attenuation (adjustable between 0 and 15) the smaller the pulse length. Stable voltage control may be verified by either adjusting the PRISMIC voltage set point datum or placing load on the system. With stable voltage control the reactive power sharing commissioning may commence: 1) Reduce the reactive power sharing deadband and adjust the reactive power sharing attenuation preset for optimum stability. 2) Place a set in manual control and increase the AVR datum on that set, return the set back to PRISMIC control, This should result in stable operation.
  • 124. STABILITY CONTROLS USING KEYBOARD ENTRY (PRISMIC 'B') Training Module: 07.05.02 Issue: A Date: July 2003 Page: 5 of 6 07.05.02 (A) Stability Controls B.doc © Brush Electrical Machines Ltd. 2003 As the AVRs on the interconnected sets are in droop control, reactive power sharing due to load fluctuations are taken care of by the AVRs and the reactive power sharing control only comes into play when a set is being introduced onto the busbars. Various permutations of sets should be tried to prove stability. 4 CONNECTING TO THE GRID NETWORK If the system is used in conjunction with a grid network, it should now be commissioned. As the frequency and voltage is maintained by the local supply authority the prime movers governor controls only the power swings between the machine and the grid. Base load control is where PRISMIC maintains the MW's on the machine to optimise fuel efficiency, whilst peak lopping is where the import or export MW values on the grid feeder are maintained to optimise local supply authority tariffs. The AVR now controls reactive power between the machine and the grid. If power factor control is selected the PRISMIC will either control the power factor based on the machine, or grid MW's on the grid or the machine, depending upon the design of the system. If VAR control is selected the PRISMIC will control the VAr's on either the grid or the machine. Due to the grid network voltage and frequency remaining fairly constant, both governor and AVR controls become more active when the set is connected to a grid. 5 AFTER COMMISSIONING Having successfully commissioned both governor and AVR control, re-install all governor and AVR voltage control relays and record all preset settings.
  • 125. STABILITY CONTROLS USING KEYBOARD ENTRY (PRISMIC 'B') Training Module: 07.05.02 Issue: A Date: July 2003 Page: 6 of 6 07.05.02 (A) Stability Controls B.doc © Brush Electrical Machines Ltd. 2003 BLANK PAGE
  • 126. CALIBRATION PROCEDURES (PRISMIC 'B') Training Module: 07.06.02 Issue: A Date: July 2003 Page: 1 of 10 07.06.02 (A) Calibration Procedures B.doc © Brush Electrical Machines Ltd. 2003 CALIBRATION PROCEDURES (PRISMIC 'B')
  • 127. CALIBRATION PROCEDURES (PRISMIC 'B') Training Module: 07.06.02 Issue: A Date: July 2003 Page: 2 of 10 07.06.02 (A) Calibration Procedures B.doc © Brush Electrical Machines Ltd. 2003 CONTENTS 1 INTRODUCTION........................................................................................................................................ 3 2 ANALOGUE CARDS ................................................................................................................................. 3 3 VOLTAGE SENSING UNIT ....................................................................................................................... 4 4 POWER MEASUREMENT SYSTEM......................................................................................................... 5 5 PRISMIC CALIBRATION ON SITE ........................................................................................................... 5 6 TYPICAL CALIBRATION PROBLEMS..................................................................................................... 8
  • 128. CALIBRATION PROCEDURES (PRISMIC 'B') Training Module: 07.06.02 Issue: A Date: July 2003 Page: 3 of 10 07.06.02 (A) Calibration Procedures B.doc © Brush Electrical Machines Ltd. 2003 1 INTRODUCTION The general principles in calibrating the PRISMIC Power Management System are detailed hereafter, but care must be exercised since each system is tailored to individual Customers' specifications. For a more detailed explanation please refer to the Operating & Maintenance Manual. 2 ANALOGUE CARDS The PRISMIC system uses three types of analogue cards which require calibration: 1) Analogue Output Card (PB-AO) These cards provide analogue signals to external metering, or pass signals on to other systems. Each card has four eight-bit output channels and can be configured to provide standard voltage and current output ranges. Calibration is normally performed by using a PRISMIC Data Module which simulates the output data from the microprocessor. 2) Analogue Input Card (PB-AI) These cards accept a wide range of analogue input signals from the outside world. Each card has eight eight-bit input channels which may be configured to accept standard voltage and current output sources normally fed from transducers and external potentiometers. Typical inputs are MW load feeder information for load shedding, turbine capability signals and general data for displaying on an HMI system. The resolution is limited to eight-bit accuracy. As the inputs are fed from calibrated transducers, calibration is normally performed by disconnecting the output of the transducer and substituting the card input with a known voltage or current source to simulate the transducer output. By simulating the minimum output of the transducer, the appropriate analogue inputs 'offset' control can be set and then, by simulating full output of the transducer, the input channels appropriate 'gain' potentiometer may be adjusted to suit. Refer to the contract card function sheets for channel ranges etc. Repeat this procedure several times to achieve accurate calibration checking at half scale for linearity. 3) Power Transducer Card (PB-PT) This card has eight input channels, four are dedicated for power and VAr measurement using the voltage sensing unit in conjunction with interposing CT's whilst the four remaining channels are for analogue inputs. This is the only card to measure in twelve-bit accuracy. Full scale in hexadecimal is 0FFF hex. Before the advent of the PC based HMI systems these inputs were utilised for datum setting potentiometers. A 0V and +10V reference signal would be connected across an external potentiometer and the wiper signal would be fed into the input channel. This feature still exists on the cards although rarely used. Today these inputs are used to monitor busbar voltages in conjunction with the auxiliary card and also analogue inputs where input card numbers have been rationalised. These analogue inputs have no gain and offset controls associated with them. The card gives us twelve-bit accuracy (0.024%) of the analogue input signal. The input range is 0V to +10V and requires transducers tailored to suit. It is most important that during the calibration procedure all sets remain in manual control as adjusting the MW calibration levels adjusts the spinning reserve figure, possibly causing a load shed situation.
  • 129. CALIBRATION PROCEDURES (PRISMIC 'B') Training Module: 07.06.02 Issue: A Date: July 2003 Page: 4 of 10 07.06.02 (A) Calibration Procedures B.doc © Brush Electrical Machines Ltd. 2003 3 VOLTAGE SENSING UNIT The unit is to comprise two independent transformers fitted together to form a composite unit. Each transformer to be as follows: Primary: 110V 50/60Hz Secondary 1: 50V 5VA Class 3 Secondary 2: 29V 5VA Class 3 Earth screen between windings. The transformers to be wired to stud terminals and clearly marked A1, A2, A3, B1, B2 and N as shown in Figure 1, voltages also to be marked. Figure 1: Voltage Sensing Unit Line voltage is monitored via an analogue input channel on the Power Transducer Card. The auxiliary card is provided with a supply from each individual busbar VT. This is then stepped down via a transformer, rectified and attenuated before providing a nominal 5V dc signal into the input channel. A nominal 5V corresponds to half of the input scale on the channel which is 7FF hex in the RAM store. On an 11kV system the input range will be zero to 22kV. Although no offset and gain controls are provided for the analogue inputs on the Power Transducer Cards potentiometers are supplied on the auxiliary boards to 'trim' busbar voltage values. The PRISMIC voltage sensing unit (VSU) shown in Figure 1 is fed by a three phase nominal 110V ac supply from the busbar VT that the generator is coupled to. A single phase instrumentation class CT is derived from the generator busbar. The VSU unit secondary windings are wound in 'open delta' which produce a 50V signal in phase with the line current at unity power factor and another introducing a ninety degree phase shift.
  • 130. CALIBRATION PROCEDURES (PRISMIC 'B') Training Module: 07.06.02 Issue: A Date: July 2003 Page: 5 of 10 07.06.02 (A) Calibration Procedures B.doc © Brush Electrical Machines Ltd. 2003 4 POWER MEASUREMENT SYSTEM Figure 2: Power Measurement System Figure 2 shows the power measurement system used within the PRISMIC system. An interposing CT is fitted in the incoming line to provide isolation between the main Generator CT and the PRISMIC Power Transducer Card. It is often a case that the main CT secondary winding is earthed for safety reasons. Two 2.2Ω resistors form a burden on the 1A secondary winding of the interposing CT, this is to supply the current input to the card with a voltage whose amplitude and phase directly matches that of the generator or grid feeder being measured. The three phase supply is configured to suit the phase in which the measurement CT is fed from. Active Power (Watts) is equated in a three phase system as √3 VI cosΦ. Where V is line volts, I is line current and cosΦ is the cosine of the phase angle displacement between line volts and line current. The PRISMIC Power transducer card measures reactive power by multiplying the in phase voltage reference by the CT reference current. Reactive Power (VAr) is equated in a three phase system as √3 VI sinΦ. Where V is line volts, I is line current and sinΦ is the sine of the phase angle displacement between line volts and line current. The PRISMIC Power transducer card measures active power by multiplying the quaduature phase voltage reference by the CT reference current. On HV systems it is normally assumed that, as most of the loads are HV motors, load is distributed evenly between each of the three phases and therefore it is prudent to monitor only one phase of the generator's output. Power transducer cards within the PRISMIC system use the outputs from the VSU unit in conjunction with this CT signal to derive generator output MW and MVArs. On multi-set systems the number of VSU units is rationalised by fitting them on the busbar sections rather than on each individual generator VT. 5 PRISMIC CALIBRATION ON SITE A PRISMIC system supplied in a control panel is normally pre-calibrated at our works making calibration simply a case of verifying on site. In our works we will have injected line volts and current using a three phase supply using a series of Variacs and 'padder' resistors or a three phase protection relay injection set.
  • 131. CALIBRATION PROCEDURES (PRISMIC 'B') Training Module: 07.06.02 Issue: A Date: July 2003 Page: 6 of 10 07.06.02 (A) Calibration Procedures B.doc © Brush Electrical Machines Ltd. 2003 The system is secondary tested using the known Customer's CT and VT ratios. Figure 3 and Figure 4 outline how this is achieved. To simulate a MW input signal we inject a phase to neutral current signal. The phase selected is the one the CT is connected in. Reactive power may be provided by injecting a current sourced from the opposite two phases to the line current. Figure 3: Watts Injection Figure 4: VAr Injection On site however, it is often impracticable to do this so we can alternatively use the generator as a source of power. To verify the secondary power being fed into the PRISMIC panel we must monitor the input three phase VT supply and single phase coming from the machine. In most of the handbooks/manuals reference was made to the two Wattmeter method of power measurement. This meant in the early days carrying around two rather bulky, delicate analogue instruments which each had multiplying factors within them. Later instruments contained these two instruments in one case. The two wattmeter method of power measurement in a three phase system is the most commonly used. The advantages are that three phase power can be measured regardless of the state of balance, waveform phase sequence or load connection (star or delta). Figure 5 outlines the configuration of the system.
  • 132. CALIBRATION PROCEDURES (PRISMIC 'B') Training Module: 07.06.02 Issue: A Date: July 2003 Page: 7 of 10 07.06.02 (A) Calibration Procedures B.doc © Brush Electrical Machines Ltd. 2003 Figure 5: Two Wattmeter Measurement Method In this method the Wattmeter current coils are connected in any two lines, the voltage coils being connected between each of these two lines and the third line. The sum of the readings obtained is the total three phase load entering the PRISMIC panel from the generator. If we multiply this by the VT and CT ratios we can then calculate the actual MW value being generated by the set. The reactive component (VAr) may be calculated by the difference between the two Wattmeter readings multiplied by 1.732. With the advent of modern solid state devices new digital Wattmeters are becoming available. In the Training area we use a Nanovip handheld instrument which uses a single phase clamp CT to measure the current signal whilst monitoring the VT signal with voltage probes. With this instrument we are able to read MWs, VArs, line voltage and current, frequency and VA. As we are measuring on the secondary side of the CT's and VT's we need to include the CT and VT ratios into our calculations. On the training rig the VT ratio is 11,000: 415 and the CT ratio is 150:5. Therefore the actual MW and MVAr on the set is given as: Watts or VArs on set = (Actual W or VAr reading) x (11000/415) x (150/5) This assumes the instrument is measuring three phase power. Whilst the set is on-line by shorting out the incoming CT signal with the SAK terminal link the power measurement channel offset control potentiometer may be adjusted to indicate zero power on the channel. Opening the CT shorting link and placing load on the set will allow the gain of the channel to be adjusted via the appropriate potentiometer. The greater the load on the set the more accurate the calibration is likely to be. Re-check the offset for any drift as well as checking at different set loadings to verify calibration linearity. This will highlight any 'phasing problems'. Refer to the contract card function sheets for input channel scaling and calibration potentiometer references.
  • 133. CALIBRATION PROCEDURES (PRISMIC 'B') Training Module: 07.06.02 Issue: A Date: July 2003 Page: 8 of 10 07.06.02 (A) Calibration Procedures B.doc © Brush Electrical Machines Ltd. 2003 As reactive power on a generator can be both 'Lagging' and 'Leading' the offset control is normally set mid range i.e. 7FFh at zero VArs whereas with the MW scaling this is normally set at 100h at zero MW . This is used during an offloading sequence so that if the power on set (MW) goes into reverse power then PRISMIC will know that to offload the set it must issue a raise governor signal. On earlier systems zero MW equalled 000h, it was therefore important to ensure that whilst setting the offset controls on the MW channels that the display showing the hexadecimal value of that channel was indicating a slightly positive value. It is important at this stage to verify the customers metering at this stage to ensure both systems tally as this could possibly lead to doubt at a later date if the two readings do not correspond. 6 TYPICAL CALIBRATION PROBLEMS Typical problems associated with the initial calibration of the power transducer channels during commissioning are outlined hereafter. Should the calibration procedure be totally unobtainable verify all three phases are present on the VSU, verify phase rotation is correct and if this is correct verify CT is in the correct phase. Should the latter be the case, transpose the VSU input cables to suit. Should the MW channels not be reading set the offset controls slightly positive, increase MW loading on the set and if the reading decreases then the CT direction is incorrect. Should neither the MW or MVAr channels operate check whether the CT shorting link is in circuit. If the channel gain is not attainable remove one of the channels CT burden resistors on the auxiliary board. Should the channel gain be high even with the gain pot reduced to minimum then reduce the CT burden resistors on the auxiliary board. Note: Changing the values of these resistors affects the calibration of both the Watts and VAr channels. From past experience on site, Customers instrumentation is often limited and if a three phase power measuring device is not available then use must be made of this instrumentation. Figure 6 outlines various three phase formula's for calculating power within a system allowing for missing instrumentation. Figure 6: The Power Triangle Using trigonometry we can represent Watts, VA and VArs as a right angle triangle. Where we see notation cos -1 this is a simple way of reversing the cosine of the voltage and current phase displacement back to electrical degrees.
  • 134. CALIBRATION PROCEDURES (PRISMIC 'B') Training Module: 07.06.02 Issue: A Date: July 2003 Page: 9 of 10 07.06.02 (A) Calibration Procedures B.doc © Brush Electrical Machines Ltd. 2003 To calculate the MW loading on a generator or grid feeder where no power instrumentation is available sometimes a polyphase kWh meter is fitted in circuit. This instrument is similar to the meter found in our houses to monitor how many Kilowatt hours of electricity we have consumed. This device provides very accurate readings. The speed at which the instruments mechanism revolves is directly proportional to the power being delivered by the generator it is connected to. This method relies on fairly constant MW loading on the feeder or set to be successful. Figure 7 shows such a device. Figure 7: Polyphase kWh Meter These instruments are often calibrated for the primary input on the busbars so they will give a direct reading of the generator or feeder MW values. The instrument in Figure 7 has a conversion factor of 30 revs per kWh. This means for 1kW flowing for 1 hour, then the aluminum disk will revolve 30 times. Therefore 1 kW = (30/60) revs per minute = 0.5 rpm If the disk was timed over a 1 minute period which resulted in 200 revolutions of the disk then the power supplied by the power source would be: Power = (200 [Reading]/5 [rpm]) x 1kW [Base Scale] = 400kW
  • 135. CALIBRATION PROCEDURES (PRISMIC 'B') Training Module: 07.06.02 Issue: A Date: July 2003 Page: 10 of 10 07.06.02 (A) Calibration Procedures B.doc © Brush Electrical Machines Ltd. 2003 BLANK PAGE
  • 136. LOAD SHEDDING (USING HMI) Training Module: 07.08.02 Issue: A Date: April 2003 Page: 1 of 6 07.08.02 (A) Load Shedding (HMI Systems).doc © Brush Electrical Machines Ltd. 2003 LOAD SHEDDING (USING HMI)
  • 137. LOAD SHEDDING (USING HMI) Training Module: 07.08.02 Issue: A Date: April 2003 Page: 2 of 6 07.08.02 (A) Load Shedding (HMI Systems).doc © Brush Electrical Machines Ltd. 2003 CONTENTS 1 INTRODUCTION........................................................................................................................................ 3 2 MODES OF OPERATION.......................................................................................................................... 3 2.1 Gradual Overload................................................................................................................................ 3 2.2 Fast Acting Load Shedding................................................................................................................. 4 2.3 Under Frequency Load Shedding (Stage One) .................................................................................. 4 2.4 Under Frequency Load Shedding (Stage Two) .................................................................................. 5
  • 138. LOAD SHEDDING (USING HMI) Training Module: 07.08.02 Issue: A Date: April 2003 Page: 3 of 6 07.08.02 (A) Load Shedding (HMI Systems).doc © Brush Electrical Machines Ltd. 2003 1 INTRODUCTION The principles of the load shedding functions within the PRISMIC system are outlined hereafter. As the document outlines general principles care must be taken in the interpretation of this data sheet as each contract is tailored to individual customers specifications and various options may be omitted or modified. For a more detailed explanation please refer to the Operating & Maintenance Manual. PRISMIC load shedding is designed to trip various loads on the busbar(s) in a pre-defined sequence to elevate cascade tripping of generating packages. The tripping levels are all adjustable through a PC keypad. PRISMIC load shedding protection is normally graded so that loads will be tripped before any system protection relays operate. This keeps generating plant on-line thus preventing a complete site shutdown. The priority in which the loads tripped is referred to as the 'load shedding priority matrix' which can be set using a PC keypad. Each load is allocated a priority the least priority load being tripped first during a system overload. Loads are classed as either monitored or non-monitored, the monitored loads being large drives or motors which can operate over a wide load cycle. These load are normally fitted with MW transducers which monitor the exact power taken by the load so PRISMIC can trip loads more accurately during an overload situation. Non-monitored loads are normally pump motors which have a constant MW loading. These are all adjustable through a PC keypad. Should an overload occur on the system loads will be shed in the pre-defined shedding sequence with the exception of loads not being on or in split bus where PRISMIC only trip loads on an overloaded bus. Should a load fail to trip PRISMIC will ignore that load and proceed to trip loads further down the matrix. Where a load selection is missing or one load has multiple selections, software prevents incorrect selection of the priority being made. All the three modes of load shedding operate in both solid and split bus modes and all work in conjunction with each other. ► 2 MODES OF OPERATION The three modes of load shedding are as follows: 2.1 Gradual Overload As it's name suggests the gradual overload comes into operation when the system load 'creeps' above the system capacity. To prevent nuisance tripping an IDMT timer is used rather like in protection relays whereby the load is shed quicker with a large overload than with a small one. The overload timer is given in units of MW seconds per Generator and, as it is a function of the prime mover. This figure is supplied by the prime mover manufacturer. This counter may be viewed using the PRISMIC diagnostic unit. A typical scenario might be one set on the bars with an overload setting of 12MW Seconds per set, should a 1MW overload be superimposed on the busbar then the load shedding will operate in 12 Seconds. Should a 12MW overload be superimposed on the busbar then the load shedding will operate in 1 Second. Two sets on the bars the gradual overload counter will count up twice as slow i.e. 24MW Seconds. Should at any time the overload disappear during the timer integrating up then it automatically will be reset to zero. During an overload situation where the gradual overload counter has expired PRISMIC will calculate the load that needs 'ditching' as the spinning reserve at this time will be negative. PRISMIC will then calculate the load that requires shedding and by working down the priority matrix trips sufficient load to produce a small positive spinning reserve value using the monitored and non monitored load values. The instant all these load(s) are shed a 'load shed retrip timer' is started which prevents further load shedding until the power generation system re-stabilises. After this timer expires should there still be an overload imposed on the system further load shedding will commence, if not the gradual overload timer will be reset so that the next overload will again go through the inverse timer counter. ►
  • 139. LOAD SHEDDING (USING HMI) Training Module: 07.08.02 Issue: A Date: April 2003 Page: 4 of 6 07.08.02 (A) Load Shedding (HMI Systems).doc © Brush Electrical Machines Ltd. 2003 2.2 Fast Acting Load Shedding This mode of load shedding is used to prevent cascading failure of the generation system. It is invoked by either a protection relay operating or the generator breaker opening. In this situation the system spinning reserve is re-calculated instantly based on new number of sets on the busbar and should there be an overload then load(s) will be tripped instantly down the priority matrix to remove the overload on the remaining machines therefore by-passing the gradual overload timer. Normally the digital signals for all the generator auxiliary breaker contacts and protection relays pass through an I/O card which produces an interrupt signal to the processor to tell it that a set's breaker has changed state and to invoke the fast acting software routine. After the initial trip the load shed retrip timer is invoked as in the gradual overload situation. ► 2.3 Under Frequency Load Shedding (Stage One) This mode of load shedding is invoked due to either fuel blockages or very high prime mover loading where the prime mover is becoming stalled. Whilst the PRISMIC is attempting to control busbar frequency to the nominal setting during this situation it may be assisted by removing load. During a under frequency situation the line Voltage is likely to be depressed due to AVR flux limiters operating In this case we cannot rely on the MW loading figures on the sets so, we trip on under frequency. Figure 1 shows a typical arrangement of under frequency settings. Figure 1: Typical Arrangement Of Under Frequency Settings The set point is the level at which PRISMIC controls the nominal busbar frequency to by trimming the governor signals. Should the frequency fall below the trip level for the duration of the under frequency stage one level a single load will be shed (refer to contract handbook).At this instant the under frequency re-trip timer will be started and should the frequency not recover above the `under frequency recovery level' after this timer has expires then further tripping of single loads will continue. The time between tripping is the duration of the under frequency re-trip timer. After the busbar frequency rises above the `under frequency recovery level' for the duration of the `under frequency re-trip timer' then the `under frequency trip timer' is reprimed. It is important to ensure that PRISMIC frequency control is set to give a good frequency recovery response to minimise under frequency load shedding. ►
  • 140. LOAD SHEDDING (USING HMI) Training Module: 07.08.02 Issue: A Date: April 2003 Page: 5 of 6 07.08.02 (A) Load Shedding (HMI Systems).doc © Brush Electrical Machines Ltd. 2003 Figure 2 shows a typical under frequency scenario. Initially the frequency is being controlled to the set point. Suddenly due to a fault condition the frequency falls below the under frequency trip point. Whilst this is happening PRISMIC tries to return the system to nominal frequency by issuing raise signals to all available on-line sets. Having failed to return the system frequency above the under frequency trip level for the period of the under frequency trip timer (t1) a single load is shed. The retrip timer is started (t2) and, as the system has not risen above the recovery level further tripping of single loads proceeds in intervals of t2. Figure 2: Typical Under Frequency Scenario 2.4 Under Frequency Load Shedding (Stage Two) Should the under frequency situation become more serious then the second stage of load shedding will be invoked. Should the frequency fall below the under frequency stage trip level then instantly blocks of load are shed. The number of loads in the block are set up within the PRISMIC system. Second stage load shedding is not utilised very often and is not recommended for `split shafted' turbines where large loads can transiently cause the turbine speed to drop below the under frequency trip level. ►
  • 141. LOAD SHEDDING (USING HMI) Training Module: 07.08.02 Issue: A Date: April 2003 Page: 6 of 6 07.08.02 (A) Load Shedding (HMI Systems).doc © Brush Electrical Machines Ltd. 2003 BLANK PAGE
  • 142. SPINNING RESERVE Training Module: 07.09.01 Issue: A Date: April 2003 Page: 1 of 6 07.09.01 (A) Spinning Reserve.doc © Brush Electrical Machines Ltd. 2003 SPINNING RESERVE
  • 143. SPINNING RESERVE Training Module: 07.09.01 Issue: A Date: April 2003 Page: 2 of 6 07.09.01 (A) Spinning Reserve.doc © Brush Electrical Machines Ltd. 2003 CONTENTS 1 INTRODUCTION........................................................................................................................................ 3 2 SOLID BUS SYSTEM ................................................................................................................................ 3 3 DETACHED SYSTEM................................................................................................................................ 4
  • 144. SPINNING RESERVE Training Module: 07.09.01 Issue: A Date: April 2003 Page: 3 of 6 07.09.01 (A) Spinning Reserve.doc © Brush Electrical Machines Ltd. 2003 1 INTRODUCTION The general principals for calculation of spinning reserve values on which the starting and stopping of prime movers, load shedding, spinning reserve alarms, power sharing and load start inhibit signals are based are detailed hereafter. Note: Refer to Operating & Maintenance Manual for any deviations contract specific information. ► 2 SOLID BUS SYSTEM Assume a solid bus system where all on-line sets are electrically interconnected through a continuous busbar system. The prime mover, diesel or turbine, supplies the mechanical power referred to as Watts into the load and therefore all calculations are based on the 'real power' component of the supply. Figure 1 shows the system capacity and system load displayed in a similar fashion to an analogue meter scale. Under healthy conditions, the capacity line will have a higher reading than the load. Figure 1: System Capacity 1) Capacity The capacity is normally calculated by summating the individual prime movers capacity of the on-line sets selected for PRISMIC automatic operation plus the actual load on any on-line set selected for manual control. This is because PRISMIC cannot assume that the full output of a manually selected set can be attained. The nominal MW capacity of a prime mover can be set as follows: (a) Manually set within the PRISMIC system (b) Via an analogue input from the turbine control panel (often referred to as TMAX) (c) A combination of (a) and (b), where the nominal zero degree Celsius MW capacity of the turbine is manually set within the PRISMIC system either through preset switches or via a PC keyboard. PRISMIC then takes in an RTD ambient air temperature signal for the software to derate the turbine capacity, based on the turbine manufacturer's data. 2) System Load This is derived by summating the MW values of all on-line sets, whether selected for PRISMIC control or not.
  • 145. SPINNING RESERVE Training Module: 07.09.01 Issue: A Date: April 2003 Page: 4 of 6 07.09.01 (A) Spinning Reserve.doc © Brush Electrical Machines Ltd. 2003 3) Spinning Reserve This is the MW value of the system capacity minus the system load. Under normal conditions, this is a positive value and is the `spare capacity' remaining before the on-line prime movers become overloaded. A negative spinning reserve will normally invoke load shedding due to a system overload. ► 3 DETACHED SYSTEM Operational situations or system faults can cause the busbars to become detached through bus couplers. PRISMIC detects this situation in the following examples by examining the status of all bus-coupler and interconnector breakers, calculating the bus capacity, bus load and spinning reserve for each bus section. Note: Take care when switching sets from AUTO to MANUAL control, as the spinning reserve figure will be reduced. Figure 2 includes the `critical spinning reserve' and the 'excessive spinning reserve alarm'. Figure 2: Critical Spinning Reserve Should the spinning reserve level fall below the critical spinning reserve setting for the duration of the critical spinning reserve timer, then an alarm is issued by the PRISMIC system informing the Operator that, should the load rise further, load shedding will occur. Should the spinning reserve level increase above the excessive spinning reserve setting for the duration of the excessive spinning reserve timer, then an alarm is issued by the PRISMIC system informing the operator that there are too many machines running on the bus. The Operator is given the opportunity to shut a set down. Having too many sets on the bus increases the reliability of the system should a set fail, but tends to run the sets inefficiently. Most engines optimum efficiency is approximately 90% of their full load rating. ► Figure 3 shows the 'set stop' and 'set start' margins. These determine when sets are stopped or started.
  • 146. SPINNING RESERVE Training Module: 07.09.01 Issue: A Date: April 2003 Page: 5 of 6 07.09.01 (A) Spinning Reserve.doc © Brush Electrical Machines Ltd. 2003 Figure 3: Set Stop/Set Start Margins Timers are used to prevent transient stopping and starting of the engines. Normally, when set management is included in the PRISMIC system, sets are automatically started before the critical alarm is activated. Should the spinning reserve level increase above the set stop margin for the duration of the set stop timer, then a shutdown signal is issued to the highest duty running engine available for PRISMIC control. Should the spinning reserve level fall below the set start margin for the duration of the set stop timer, then a start signal is issued to the next available engine. ► Figure 4 includes 'load inhibit levels'. Where there is a possibility of causing an overload on the system by starting a large load, the PRISMIC system uses the following feature. Figure 4: Load Inhibit Levels If the spinning reserve falls below the `restart load MW' value and the load feeder is open, an inhibit signal is issued to that breaker preventing it from being closed manually. The `load restart MW' values are set either using preset switches or via a PC keyboard on the PRISMIC system. They are set higher than the nominal running MW value of the load to allow for starting currents.
  • 147. SPINNING RESERVE Training Module: 07.09.01 Issue: A Date: April 2003 Page: 6 of 6 07.09.01 (A) Spinning Reserve.doc © Brush Electrical Machines Ltd. 2003 As most of a motor starting current is reactive and loads the generator rather than the prime mover, the software logic can be configured to ensure that enough generators are on line to supply this reactive power, as well as spinning reserve. ►
  • 148. DATA COMMUNICATIONS Training Module: 07.10.01 Issue: A Date: April 2003 Page: 1 of 12 07.10.01 (A) Data Communications.doc © Brush Electrical Machines Ltd. 2003 DATA COMMUNICATIONS
  • 149. DATA COMMUNICATIONS Training Module: 07.10.01 Issue: A Date: April 2003 Page: 2 of 12 07.10.01 (A) Data Communications.doc © Brush Electrical Machines Ltd. 2003 CONTENTS 1 INTRODUCTION........................................................................................................................................ 3 2 COMMUNICATIONS - WHAT IS IT?......................................................................................................... 3 3 WHAT IS DATA COMMUNICATIONS ...................................................................................................... 3 4 HISTORICAL BACKGROUND TO DATA COMMUNICATIONS SYSTEMS............................................ 4 5 INFORMATION TRANSFER SYSTEMS ................................................................................................... 6 6 TELECOMMUNICATIONS SYSTEMS AND NETWORKS ....................................................................... 6 7 DATA AUDIO AND VIDEO COMMUNICATIONS..................................................................................... 7 8 THE COMMUNICATIONS INTERFACE.................................................................................................... 7 9 OVERVIEW OF THE EIA RS-232, 423, 422 & 485 INTERFACE STANDARDS ..................................... 8 10 'SMART' INSTRUMENTATION.............................................................................................................. 9 11 MODERN INSTRUMENTATION AND CONTROL SYSTEMS............................................................ 10
  • 150. DATA COMMUNICATIONS Training Module: 07.10.01 Issue: A Date: April 2003 Page: 3 of 12 07.10.01 (A) Data Communications.doc © Brush Electrical Machines Ltd. 2003 1 INTRODUCTION The following examines what Data Communications is, why it is needed and outlines where the subject fits in with other types of communication systems. It also provides an overview of the historical background of Data Communications and traces its development up to modern times. It introduces some of the basic concepts of data communication leading up to a brief review of the commonly used serial interface standards such as RS-232, RS-423, RS- 422 and RS-485. The concept of 'smart' instrumentation is introduced to emphasise the increased need for data communications in a modern control system. It then briefly outlines the application of data communications in a modern Industrial Control System. 2 COMMUNICATIONS - WHAT IS IT? The goal of a Communications System is to transfer a message from one place to another. The type of information to be transferred will often determine which communication method can be used. In modern times, we are accustomed to transferring the following types of information: Ø Data (Combination of Characters) Ø Audio (Voice and Music) Ø Video (Complex Picture Images) This information can be transported over great distances quickly and reliably via one of several mediums such as Air (Radio, Microwave, Satellite Link), Metal Conductors (Landlines, Underground Cables, Undersea Cables), Road/Rail/Air (Postal Service) and Optic Fibre Cables, using a wide range of energy frequencies and wavelengths. The main purposes are for business, news, entertainment and military needs. This has become such an integral part of our lives that it is sometimes difficult to imagine the difficulty that was experienced in earlier times with communications. To illustrate the concepts, a well known form of communication, still commonly used today, is the writing and mailing of letters. In centuries past, information was recorded in the form of Characters on stone tablets and later on sheets of paper. In modern times, information can be recorded electronically on Floppy Disks, Hard Disks, Magnetic Tapes and, more recently, on Compact Disks. Characters are still used as the basic component of any recorded data. In historical times, the recorded information was transported from one place to another by camels, horses and sailing ships; later by steam trains and ships and now by electric trains, road transport and jet aeroplanes. In all these cases, the following common factors exist: Ø Some Information needs to be Transferred from one location to another. Ø There is a Transmitter of the information. Ø There is a Receiver of the information. Ø A Communication Link, or series of links, is available to transport the information from the sender to the receiver. The subject of Communications has almost limitless scope. The material in this course is aimed at only one small part of the overall subject, being: Ø The subject of Data Communications. Ø In the context of Industrial Automation and Process Control. ► 3 WHAT IS DATA COMMUNICATIONS The subject of digital Data Communications is concerned with the electronic transfer of Data from one place to another, via any medium. Data (plural of datum, meaning an item of information), is the general term used to describe the components of a message or information. Messages are usually made up of characters or numbers, which may be recorded on a piece of paper or electronically. In data communications, the data are disassembled into bits, transferred bit by bit as electronic pulses, then reassembled at the receiving end.
  • 151. DATA COMMUNICATIONS Training Module: 07.10.01 Issue: A Date: April 2003 Page: 4 of 12 07.10.01 (A) Data Communications.doc © Brush Electrical Machines Ltd. 2003 A Character is the general term that is used to describe any alphabetic letter, punctuation mark, number or symbol commonly used for the recording, processing and transferring of information. When these characters are combined into words, equations, sentences, paragraphs and reports, the combination of characters becomes known broadly as a Message or more generally as Data. Data can be any combination of any characters, binary numbers, etc. We are very familiar with the 26 characters of the English alphabet and the specific rules for combining these characters into the language of English. There are also a number of other similar languages, however, using a slightly different alphabet (e.g. German, Swedish, Spanish, Dutch, etc) and some different languages using completely different alphabets (eg. Japanese, Chinese, Russian, etc). From the point of view of Data Communications, any of these characters or combinations of them, are treated the same. It makes no difference to the communications system what the characters are or how they are combined. Any message that can be reduced down to individual characters is suitable for transfer by data communications. The data is transferred in the form of a binary digital code. Each character is assigned an individual code made up of 'bits' (Binary digits). Provided every character has a unique code assigned to it, any message can be encoded, transferred, decoded and read at the other end. When gathered together for transfer over the communication link, these series of bits are usually referred to as data. In this course, the word data will be used when referring to these strings of bits, encoded for transfer. Data Communications describes the activity of transferring data from one location to another, without being precise about the methods of communication that are available. ► 4 HISTORICAL BACKGROUND TO DATA COMMUNICATIONS SYSTEMS As mentioned previously, the writing and mailing of a letter is a simple form of Data Communications. This method of communication was made possible a few thousand years ago by the development of various characters and alphabets by the Egyptians, Hebrews, Greeks, Romans, etc. This method of data communications, of inscribing characters on a letter and transporting it over a considerable distance, has been used successfully for a number of centuries and is still an important and cost effective component of modern data communications. The main problems with the writing and mailing of letters is the long time taken to prepare them and to transfer them from the sender to the receiver, even today with modern Airmail. There has always been a need to transfer information, motivated mainly by the need for personal communication between friends and families, for the transfer of business information and for government administration and military purposes. The successful development of world trade since the Industrial Revolution has rested firmly on the ability to communicate data from a sender to a receiver. This need to transfer data has increased rapidly over the years as the technical developments have made the ability to communicate easier and quicker. Modern electronic data communications can trace its background to the development of the Telegraph, a word derived from the Greek words graph and tele, meaning 'making marks from afar'. In the early 1800's, soon after the discovery of electricity, the first attempts at telegraph systems tried to transfer messages by using several voltages simultaneously across several wires in parallel, using some sort of code for each character. This seemed to be the logical way to do things at that time. It soon became clear that a system of parallel wires was bulky, difficult to handle and not a practical proposition for long distance communications. Consequently, attempts at parallel transfer were soon abandoned in favour of serial communication systems, where attempts were made to transfer the message sequentially along a 2-wire line. The first practical serial data communications system, which included both the hardware and a code (software), is usually attributed to an American, S F B Morse, although there has been considerable debate about this. Even if he was not the first, he certainly has become the best known for the code that he developed for serial communication, called the Morse Code.
  • 152. DATA COMMUNICATIONS Training Module: 07.10.01 Issue: A Date: April 2003 Page: 5 of 12 07.10.01 (A) Data Communications.doc © Brush Electrical Machines Ltd. 2003 In this code, the entire alphabet, numbers and some punctuation (approx. 40 characters) are represented by a series of 'dots' and 'dashes'. By today's standards, it is a complex code and not really suitable for electronic encoding. The length of the Morse code for each character varies from one pulse for a character such as E, to six pulses for a colon. There was no logical way of remembering the code for each letter, so it had to be learnt by the early telegraph operators . Morse's data communication system comprised a sounder, a key, a communication link, the Morse codes and an operator at each end. All of the activities associated with data transmission then still have their equivalent components in a modern serial data communications system i.e. Ø Message: An operator is given a message written in English. Ø Encode: The operator uses his brain and coding tables to convert each character to the Morse Code. Ø Transmit: The operator controls the key to send the coded signal across the communications link. Ø Receive: A second operator receives the message at the other end by listening to a sounder, which he may record. Ø Decode: The operator uses his brain and coding tables to convert each code back to a series of English characters. Ø Print: The operator then writes the message down in normal language for others to read. The difficult and time consuming task of manual transcription of the telegraph code was soon developed into the separate technology of Teleprinting ('printing from afar'). Initially, the electronic impulses were recorded at the receiving end by a stylus onto a rotating drum with a paper tape to provide a "hard copy" of the received code. The period when the stylus was in contact with the paper became known as Marking and the period when it was not became known as Spacing. These terms are still commonly used today in serial data communications, although they tend to be quite confusing, when used in the modern context. From that time, efforts were directed towards developing a machine that could directly encode characters for transmission and, at the other end, decode them and reproduce the actual characters, rather than just have marks and spaces. The success in this direction was governed by the rate of development in other fields of electrical engineering. Early versions of a teleprinting machine that actually printed characters consisted of an inked wheel with the typeface uniformly distributed around the circumference. The series of electrical impulses coming in across the pair of wires caused the wheel to ratchet up to the desired character at which point an arm came up behind a paper tape to make an imprint of the character on the paper tape. Unfortunately, every time there was interference on the line and an electronic pulse was gained or lost, the result was a spelling error. Later versions of the teleprinter used a complicated electromechanical system that included a rotating wheel, driven by a small synchronous AC motor, at both the sending and receiving ends. These wheels were held in synchronism by the fact that the AC power supply system at both ends stayed in synchronism through the interconnected power network. At the correct instant, a pulse was sent down the line which engaged a complicated mechanism which then printed the desired character. The major problem of the day was to keep the two ends in synchronism. Rotating head machines were used right up to the 1920s. The difficulty of maintaining synchronism between the sending and receiving end finally led to the downfall of this system and it was superseded by one of greater tolerance to frequency variation at the two ends. In addition to the mechanical and electrical problems of a teleprinting machine, the code was a severe limitation on the early efforts of electronic serial communications. The Morse Code was essentially a free-form code with a variable number of elements for each character and it is difficult to imagine designing a machine that could respond to this diversity.
  • 153. DATA COMMUNICATIONS Training Module: 07.10.01 Issue: A Date: April 2003 Page: 6 of 12 07.10.01 (A) Data Communications.doc © Brush Electrical Machines Ltd. 2003 A French Telegraphic Engineer, Maurice Emile Baudot, is usually credited with the invention of the first uniform-length 5-bit binary code in the late 1800s. A standard code, based on his coding method, was later adopted by the CCITT (Consultative Committee for International Telephone and Telegraph) for international data communications by teleprinter and is commonly called the Baudot Code. This code has been the basis of 'Telex' communications even to the present time. A 5-bit code can identify up to 32 Characters, which comfortably includes the 26 letters of the alphabet. When adopted by CCITT, a 'smart' feature of the code was the ability to 'shift', like a typewriter, into a supplementary set of 32 characters, mainly for numbers and figures. In the machine, complex electromechanical devices (relays and levers) were used at both ends to encode and decode the message. At the sending end, pressing a character on a keyboard would encode the character into a unique 5-bit code for transmission over a pair of wires. When a message was sent, a 'Start' pulse was first sent down the line to the receiving end to synchronise the two ends. From then on, synchronism depended on the power supply frequency and the synchronous motor driving each machine. A similar mechanism would decode the message and print it onto a paper tape. Understandably, the speed of this complex electromechanical system was fairly slow. The above historical review describes how serial data communication evolved over the last century and outlines some of the technical problems associated with its development. In recent years, telex has largely been superseded by modern forms of teleprinting, based on microprocessor technology. The most common examples are facsimile, computer data links and other PC based systems using modems. ► 5 INFORMATION TRANSFER SYSTEMS It should not be forgotten that the main purpose of data communications is to transfer data from one place to another rapidly and reliably for whatever purpose. As the volume of information has increased, the speed of transfer has had to increase and with it came the need to control the flow of data to prevent the receiver from becoming overwhelmed with unexpected data. The detection and correction of errors in the data, mainly due to interference, has always been a problem that has affected the reliability of the information. To cope with this increasing traffic and to automatically identify errors, protocols have been developed to regulate the transfer of data. Protocols are computer programs which embody all the rules governing the transfer of the data, such as who sends first, how many bits at a time, how to identify when there is an error, what to do with the error, etc. The various types of protocol will be discussed in greater detail later. The fundamental requirements of an Information Transfer System are: Ø Procedures to regulate the Flow of Data so that both ends can cope with the quantity of data. Ø Procedures to regulate the Accuracy of Data and to define what to do when an error has been detected. Ø Protocols to ensure that the Sender and the Receiver work co- operatively at both ends. 6 TELECOMMUNICATIONS SYSTEMS AND NETWORKS The subject of Telecommunications ('communication from afar') has primarily been concerned with voice communication over long distances. Modern telecom systems use a wide variety of electronic equipment to meet the increasing needs of telephone users. Communication takes place by wire, radio, microwave and fibre optic cables. Contact between two users may simultaneously include one or more of these media. Older telecommunications media are limited by the quantity and rate of information that can be transferred and an inherently higher level of interference from environmental factors such as the weather and lightning. These are rapidly being replaced by optical fibre connections which can cope with far greater data rates and are less susceptible to interference. The telecom system is part of a large network which spans not only the entire country but is also connected into the national networks of other countries. It provides users with a cost effective private 2-way voice and data communications to almost any part of the world. The system enables the user to dial and be connected by switching circuitry to the desired receiver. ►
  • 154. DATA COMMUNICATIONS Training Module: 07.10.01 Issue: A Date: April 2003 Page: 7 of 12 07.10.01 (A) Data Communications.doc © Brush Electrical Machines Ltd. 2003 7 DATA AUDIO AND VIDEO COMMUNICATIONS Data Communications is concerned with the transfer of information in the form of characters, each of which is in the form of a code. This type of communication is referred to as being 'digital' because the data to be transferred is first broken down into bits 'O's or '1's before being transmitted electronically as 'off' or 'on' voltages on the line. As outlined above, digital data communications is not a new invention but has been in use for over a century. Audio Communication is essentially concerned with the transmission of analogue sounds and speech that are in the audible frequency range of about 10Hz to 20kHz. An analogue signal is one that is continuously changing within certain limits of voltage and frequency. The telephone system is the most well known of the audio communication systems. Another example of audio communication is the radio. For radio transmission, modulation techniques such as AM (Amplitude Modulation) and FM (Frequency Modulation) are used to prepare the audible information for broadcast by radio signal. Radio receivers are used to decode the signal, amplify it and bring it back to the 10Hz-20kHz audible range. The signals used for digital data communications are not directly compatible with the telephone system, which is designed for analogue audio communication. These signals have to be converted to compatible signals by some interface equipment, called Modems. The Modem is a device that takes digital signals and converts them into a form suitable for the communication link. Video Communication is mainly oriented towards entertainment in the form of television. TV is an extremely complex system because it must convert a two-dimensional picture into electronic signals suitable for transfer across a communications link and, simultaneously, also transfer the audio signal. The technical problems of TV were overcome during the period between 1920 and 1950 and are still in a continuous state of development. TV has used analogue VHF and UHF carriers to transfer the video signals by air or coaxial cables. These high frequency signals contain a vast amount of information (video, audio and synchronising signal) and occupy a frequency bandwidth of 6 MHz. Digital video signals for television are not yet a viable alternative to analogue because of the very high rate of data transfer that would be required (approx 70 Mbps!). Facsimile or Fax, which uses some of the principles of television to convert two-dimensional images to an electronic signal, uses digital data signals suitable for transmission over a telephone network. This is a 'still' picture, however, with no sound and with only a few shades of grey and a much longer time is permitted for the data transfer. Data compression and error correction techniques have enabled facsimile to transfer a single page image in less than one minute. ► 8 THE COMMUNICATIONS INTERFACE The communications Interface is the point of contact between two different communications environments or between two different types of equipment. The meaning of the word Interface, in this context, may be illustrated by the example of an interface between the power supply company and our homes. Electric power is usually transported at high voltages (132kV, 11kV, etc) while power in the home is usually used at lower voltages. The power company needs the high voltages for economic transfer of power, while the home owner needs the low voltage to safely operate electrical appliances. To connect power to the home, the power company must reduce the voltage through a transformer and connect it to the home via a suitable meter box. The standards associated with this connection system are dictated by the power company and the wiring in the home must conform with these standards. This 'hook-up' is called an Interface and the standards that define the technical details are the Interface Standards, which are published documents and open for all to see and comply with. The Interface fulfils several criteria: Ø Prevents damage to power company's electrical system. Ø Prevents damage to the electrical system in the home. Ø Provides a usable and workable system.
  • 155. DATA COMMUNICATIONS Training Module: 07.10.01 Issue: A Date: April 2003 Page: 8 of 12 07.10.01 (A) Data Communications.doc © Brush Electrical Machines Ltd. 2003 The Interface between a computer and data communication system should fulfil similar objectives. The main objective is to provide a medium for transfer of data from one system's environment to another. Once such an interface has been established, the transfer of data from a terminal to a communications system and back is then possible. Obviously, there are many different ways that this could be achieved and every manufacturer could have a different idea about the most effective way of doing this. This potential diversity raises one of the biggest problems in data communications - compatibility with other equipment. When computers arrived on the scene they became very useful tools for the processing of data. The transmission of data to remote locations became the natural development. Short distances could easily be spanned by separate cables, but it soon became clear that access to distant locations could also be achieved by using a well established telephone network. Telephone networks, already in place, went almost everywhere and, best of all, they could be rented relatively cheaply. Telephone networks are usually owned by the state or very large corporations, so it is not surprising that these organisations insisted that strict interface standards should be adhered to before any equipment could be connected to the system. Digital equipment, commonly used for data communications, is not suitable for direct connection to the analogue type telephone network. In addition, the telephone system has a limited bandwidth, so any interface device would have to operate within those limitations. The result was the development of a translating device designed specifically for telephone networks, called a Modem (MODulator/DEModulator). Initially, many different types of modems were developed for this purpose. This stimulated the development of one of the best known standards in the field of Data Communications - the EIA-RS-232-C Interface Standard. ► 9 OVERVIEW OF THE EIA RS-232, 423, 422 & 485 INTERFACE STANDARDS The EIA-RS-232 Interface Standard was developed and issued in USA in 1969 to define the electrical and mechanical details of the interface between Data Terminal Equipment (DTE) and Data Communications Equipment (DCE) which employ serial binary data interchange. For serial Data Communications, the communications system comprises: Ø A data sending terminal (e.g. a Computer), called the Data Terminal Equipment (DTE), that is the source of the data, usually a series of characters, coded into a suitable digital form. Ø A suitable data transmitter (e.g. a Modem), called the Data Communications Equipment (DCE), that converts the signal into a form suitable for the communications link. Ø The communications link itself (e.g. Telephone system). Ø A suitable receiver (e.g. a Modem), also a DCE, that converts the signal back to a form suitable for the Receiving Terminal. Ø A data receiving terminal (e.g. a Printer), also a DTE, that is the receiver of the digital pulses for decoding back into a series of characters. The RS-232-C Interface Standard describes the interface between a Terminal (DTE - Data Terminal Equipment) and a Modem (DCE - Data Communications Equipment) specifically for the transfer of serial binary digits. RS-232-C leaves a lot of flexibility open to the designers of the hardware and software protocol. With the passage of time, this standard interface has been adapted for use with numerous other types of equipment, such as personal computers (PC's), printers, programmable controllers, PLC's, instruments etc. To recognise these additional applications, the latest version of the standard, RS-232-D, has changed the words associated with DCE to the more general "Data Circuit-Terminating Equipment". But RS-232 also has a number of inherent weaknesses that make it unsuitable for data communications for instrumentation and control in the industrial environment.
  • 156. DATA COMMUNICATIONS Training Module: 07.10.01 Issue: A Date: April 2003 Page: 9 of 12 07.10.01 (A) Data Communications.doc © Brush Electrical Machines Ltd. 2003 Consequently, several other EIA interface standards have been developed which overcome some of these limitations. Those that have become most commonly used for instrumentation and control systems are RS-423, RS-422 and RS-485. 1) RS-423 Interface Standard Unbalanced system similar to RS-232, with increased range and data transfer rates, with up to 10 line receivers per line driver. 2) RS-422 Interface Standard Balanced differential system, with same range as RS-423 but increased data rates, with up to 10 line receivers per line driver. 3) RS Interface Standard Balanced differential system, with same range as RS-423 but increased data rates, with up to 32 line transmitters/receivers per line. The RS-485 interface standard is very useful for instrumentation and control systems where several instruments or controllers may be connected together on the same multipoint network. ► 10 'SMART' INSTRUMENTATION In the 1960's, the 4...20mA (or 0...20mA) analogue interface became established as the standard for instrumentation technology. As a result, the manufacturers of instrumentation equipment had a standard communication interface on which to base their products and users had a choice of instruments and sensors from a wide range of suppliers which could be integrated into their control systems. In the 1980's, with the advent of microprocessors and the development of digital technology, the situation has changed. Most users appreciate the many advantages of the new digital instruments, such as more information, local and remote display, reliability, economy, self tuning, diagnostic capability, etc. And it is also fairly clear that there is a gradual changeover from the analogue to the digital technology. The one major difficulty that is standing in the way of a more rapid transition from analogue to digital sensors is the absence of a broadly accepted Standard for the Bus communications at the field level. Some of the leading manufacturers have already made proposals in this direction but it is likely to take a few more years before a universally acceptable standard emerges. In the meantime, manufacturers of instrumentation and control devices have developed and installed control systems where the communication between supervisory systems and the field controllers is digital, examples are DCS systems and PLC systems. But the field sensors and instrumentation are still largely incorporated via 4...20mA analogue signals. There are a number of intelligent digital sensors already available with digital communications capability for most of the traditional applications, such as for measuring temperature, pressure, levels, flow, mass (weight), density, power system parameters, etc. At this stage, these devices are usually connected along the lines of RS-485 on a 'Multipoint' bus network in an asynchronous Poll/Response mode. These new intelligent digital sensors are known as 'smart' instrumentation. The main features that define a 'smart' instrument are: Ø Intelligent, digital, measuring sensor Ø Includes digital data communications as standard Ø Allows connection to a field network (eg multipoint) There is also an emerging range of intelligent, communicating, digital devices that could be called 'smart' actuators. Examples of these are devices such as Variable Speed Drives, Soft Starters, Protection Relays, Switchgear control, etc with digital communication facilities. ►
  • 157. DATA COMMUNICATIONS Training Module: 07.10.01 Issue: A Date: April 2003 Page: 10 of 12 07.10.01 (A) Data Communications.doc © Brush Electrical Machines Ltd. 2003 11 MODERN INSTRUMENTATION AND CONTROL SYSTEMS In the Industrial environment, the main purpose of an Instrumentation and Control System is to take care of the following: 1) To Control The Process And Process Alarms Traditionally, this was provided by analogue controllers (temperature, flow, etc) operating on standard 4...20mA loops. The 4...20mA standard is "open" to equipment from a wide variety of suppliers and it is common for these to be mixed in the same control system. These stand-alone controllers and instruments have largely been replaced by integrated systems such as DCS (described below). 2) To Control The Sequencing, Interlocking And Alarms Traditionally, this was provided by relays, timers and other components hardwired in Control Panels and Motor Control Centres. The sequence control, interlocking and alarm requirements have largely been replaced by PLC's (described below). 3) To Provide An Operator Interface For Display And Control Traditionally, process and manufacturing plants were operated from local control panels by several operators, each responsible for a portion of the overall process. Modern plant-wide control systems tend to use a central control room, equipped with computer based graphic operator work-stations that gather data from the field instrumentation and use it for operator display, to control processes, to monitor alarms, to control sequencing and interlocking. 4) To Provide Management Information Management information was provided by taking readings from meters, chart recorders, counters and transducers and also from samples taken from the production process. This data is required to monitor the overall performance of a plant or process and to provide the data necessary to manage the process. Data acquisition is now integrated into the overall control system, which eliminates the tedium of gathering the information and reduces the time that it takes to correlate and use the information to remove bottlenecks. This is an area where substantial productivity gains can be achieved through good management of the process. There is no doubt that Productivity and Quality are the main objectives of any production activity, whether it be a process or a manufacturing environment. Ø Productivity and Quality are the result of good management. Ø Management can be substantially improved by the availability of accurate and timely data. The ability of control equipment to fulfil these requirements has depended on the major advances that have taken place in the fields of integrated electronics, microprocessors and data communications. The two devices that have made the most significant impact on how plants are controlled are: A) Distributed Control Systems (DCS) Have been developed by the traditional manufacturers of process control equipment, who were focused mainly on the requirements of the process industries, eg. Petrochemical, Food Processing and Paper. The requirements of DCS users are mainly associated with analogue loops to control parameters such as temperature, flow, levels, densities, etc. With DCS systems, communications at the field level are still largely based on the analogue 4...20mA standards and will probably remain that way for some time to come. However, DCS systems have for a long time been well integrated at the next higher level with a well developed ability to communicate to computers (VAX, PDP, DEC, etc) and between themselves via networks using proprietary protocol. Increasingly, DCS systems are supporting 'open' systems networks providing compatibility with other devices. To provide some facilities for sequence control and interlocking, many DCS systems now have PLC-type digital I/O to enable further integration of the control system. B) Programmable Logic Controllers (PLC) Were originally developed in the late 1960s to replace electro-magnetic relays and were primarily used for sequence control and interlocking, using racks of On/Off inputs and outputs now called 'digital I/O'.
  • 158. DATA COMMUNICATIONS Training Module: 07.10.01 Issue: A Date: April 2003 Page: 11 of 12 07.10.01 (A) Data Communications.doc © Brush Electrical Machines Ltd. 2003 PLCs have developed into one of the most effective tools for the automation of manufacturing or processes. They are designed and built for the industrial environment and are rugged, reliable, easy to program (ladder diagram) and, most of all, are cost effective. PLC technology has been developed and extended over the years and PLCs have been used in applications traditionally covered by DCS. They now are able to provide computing capability which enables them to process analogue inputs, do calculations, control analogue outputs. Although originally used as stand-alone units, PLCs now have sophisticated communications capability which enables them to communicate with other devices. Initially, PLCs became 'distributed', which means that some of their digital I/O was located some distance away from the CPU and data communication techniques were used to transfer the data. They are also capable of communicating 'upwards' to higher levels with interfaces to computers (VAX, PDP, DEC, etc) and networks such as Ethernet at a process management level. They can also communicate 'sideways' amongst themselves and other devices at a group management level, using well known PLC bus networks such as Modicon's Modbus, Allen-Bradley's Data Highway Plus, Square-D's SY/NET, GE's Genius Bus, Texas Instrument's Tiway, Honeywell's Data Hiway, etc. This allows several PLC's to be integrated on a data bus with computers or PC's. Using various data communication techniques (including 4...20mA standard), these devices collect data from all parts of a modern plant and deliver it to operator workstations to be used for the following purposes: Ø Display of equipment status and process parameters (trends) for operator information and control purposes Ø To receive and implement commands from the Operator Ø To automatically control the process 'loops' Ø Automatic sequencing to assist the operator Ø Interlocking to supervise operator commands Ø Monitor Alarms and Record Alarms Ø Event Recording for later analysis Ø Management information on all process parameters In practice, many control systems are well 'integrated' at some levels, while the availability of 'on-line' data at other levels is not often implemented. Direct data communication to the management level, or higher, is often not used. One of the main reasons is that the data communication at the Plant Control level is provided by the DCS or PLC vendors (e.g. Modbus, Data Highway Plus, SY/NET, TIWAY, etc). The users, who are usually responsible for the wider communications requirements, are often reluctant to implement this because it presents formidable technical problems both with the data communication and the computer programming requirements. A lot of these problems are associated with the lack of standardisation of data communications systems and protocols. At the field instrument level, users have held onto the relative simplicity of the 4...20mA instrument standard in spite of the development of digital "smart" instruments. Again, this would be a lot easier if there were established standards. From the point of view of many users, the extra hardware cost of providing a pair of wires and an analogue input/output from a DCS or PLC appears to be preferable to the perceived complexities of digital data communications. ►
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  • 160. FAULT FINDING (PRISMIC PMS) Training Module: 07.11.03 Issue: A Date: July 2003 Page: 1 of 8 07.11.03 (A) Fault Finding - PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2003 FAULT FINDING (PRISMIC PMS)
  • 161. FAULT FINDING (PRISMIC PMS) Training Module: 07.11.03 Issue: A Date: July 2003 Page: 2 of 8 07.11.03 (A) Fault Finding - PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2003 CONTENTS 1 INTRODUCTION........................................................................................................................................ 3 2 RACK AND EXTERNAL INPUT FAULTS................................................................................................. 3 3 EXTERNAL FAULTS................................................................................................................................. 5 4 PRISMIC GENERATED ALARMS ............................................................................................................ 5 4.1 Critical Alarm....................................................................................................................................... 5 4.2 Excessive Capacity Alarm................................................................................................................... 6 5 FAULT SCENARIOS ................................................................................................................................. 6 5.1 Power Sharing Faults.......................................................................................................................... 6 5.2 Load Shedding Faults ......................................................................................................................... 7 5.3 Set Management Faults ...................................................................................................................... 7
  • 162. FAULT FINDING (PRISMIC PMS) Training Module: 07.11.03 Issue: A Date: July 2003 Page: 3 of 8 07.11.03 (A) Fault Finding - PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2003 1 INTRODUCTION Surface mount technology, solid state electronics, reliable PCB connectors, screw retained input and output boards, and computer assisted 'pick and place' manufacture ensure that the latest generation of PRISMIC Power Management Systems (PMS) provide a high degree of reliability. PRISMIC PMS systems are designed and manufactured to the highest standards in order to be able to operate without problem in the most arduous of environments. Internal watchdog circuitry ensures that output signals from the PMS system are disabled and the system made 'fail safe' in the unlikely event of either an internal fault within the PRISMIC rack, or if the software detects invalid input configurations on the power system. Faults within a PRISMIC Power Management System fall within three main categories: Ø Internal failure within the PRISMIC rack assembly. Ø External input status failure resulting in PRISMIC receiving incorrect information from the field. Ø Failure of external devices controlled by the PRISMIC system e.g. governors AVR's breakers etc. 2 RACK AND EXTERNAL INPUT FAULTS Rack and external input status faults are recognised by the PRISMIC watchdog system provided on the PS-UW card. Figure 1: Watchdog Card In the event of a major fault occur within the control rack assembly, the watchdog circuit will normally 'drop out' thus disabling all digital output signals from the PRISMIC system. With the watchdog failed the system reverts to manual operation, since all outputs are normally energised to perform a function. Any load changes occurring on generation plant operating whilst the PRISMIC is switched off, or when the system has failed, will have to be corrected by an operator in manual control, since automatic load shedding control where provided, would be unavailable.
  • 163. FAULT FINDING (PRISMIC PMS) Training Module: 07.11.03 Issue: A Date: July 2003 Page: 4 of 8 07.11.03 (A) Fault Finding - PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2003 Indication of the watchdog being 'healthy' is given by a large red LED on the watchdog PS-UW card which is usually fitted to the bottom left hand side on the PRISMIC rack. This half size card has a series of eight diagnostic LED's above the red 'healthy' LED, and a 15 way D-connector below. The connector provides digital, potential free, signals to the external watchdog logic, as well as an analogue input to measure the integrity of the 24Volt dc supply feeding all of the digital input and output channels. Figure 2: Typical Watchdog Card Schematic Figure 2 shows a typical scheme of connections to the watchdog card (PS-UW). A DIN rail mounted module terminates panel wiring and a ribbon cable continues the connections to the PS- UW card within the PRISMIC rack. The 24Volt dc supply, derived from either a battery or power supply, is connected to cables W1 (positive) W2 (negative). A 'Control Supply Healthy' (CSH) relay, where fitted, provides remote indication to the availability of the 24Volt dc supply. This supply is then connected across terminals 1 and 3 on the PS-UW card where it is monitored. If the voltage drops below a predefined value, there is a possibility that the digital input cards will receive incorrect status information of the power system which may cause a PMS system malfunction. In this case the watchdog will drop out and inhibit further control until the problem is rectified. This situation will be indicated by an extinguished diagnostic LED on the PS-UW card. A normally open contact across terminals 5 and 9 closes when the PMS system is energised and healthy, which causes the 'Master Fault Relays' (MFR) to energise when first 'powered up'. A normally closed contact on timer (RT) will allow the MFR relays to be latched in through their own contacts. After a few seconds RT timer relay (delay on energise) will energise and open the latching path to the MFR relays. If the watchdog now 'drops out' the MFR relays are no longer able to energise, and the watchdog circuit will need to be reset by depressing the pushbutton on the PS-UW card, or alternatively powering down the PMS system. A 'wetting' supply for all the auxiliary digital inputs to the system is provided through wire W1, and wire W3 provides a supply to drive all outgoing interposing relays. It will be noted that the supply on W3 to the output channels is only present when the watchdog is healthy and, following a short delay, after 'powering up' on a system reset. This is to allow the PMS supplies to become established and to initiate system software.
  • 164. FAULT FINDING (PRISMIC PMS) Training Module: 07.11.03 Issue: A Date: July 2003 Page: 5 of 8 07.11.03 (A) Fault Finding - PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2003 The watchdog can fail for a number of reasons, which forces the PMS system into a 'fail safe' condition. Most of the faults other than an internal power supply failure will be shown up by one of the diagnostic LED's extinguishing, and the large red LED indicating that the watchdog relay has switched off. Standard functions of the diagnostic LED's are listed below: Ø Loss of 24 Volt control supply. Ø STE bus time out. Ø I/O card address failure. Ø Control software not cycling correctly. Ø Loss of VT voltage sensing. Ø Loss of VT frequency sensing. In addition, other contract specific functions may be detailed in the Operating & Maintenance Manual. 3 EXTERNAL FAULTS Assuming the watchdog is healthy, it is likely that the fault is a result of one of the following: Ø Field cabling. Ø Terminal connections. Ø Faulty PRISMIC interface cards. Ø Faulty external equipment. Ø Operator error. Each of the above possibilities should be checked systematically in order to identify and correct the fault. 4 PRISMIC GENERATED ALARMS A series of alarms are provided by the PRISMIC. The common alarms detailed may not be provided on all systems and reference should be made to the Operating & Maintenance Manual for contract specific features. Critical and Excessive Load Alarms are used to show high and low levels of spinning reserve which can be an indication the possibility of imminent load shedding, or an indication that too many machines running on the bars. In the event of these alarms check the following. 4.1 Critical Alarm 1) Verify that sufficient machines are on the switchboard to meet the current load requirement. 2) Where set management is employed verify that it is functioning correctly, checking that further machines are available for starting. 3) Verify correct operation of system capacity, system load, and spinning reserve metering as well as on the display system if fitted. Pay particular attention to breaker status signals and machine master fault relay inputs into the PRISMIC system. Check that sets are not selected for manual control since their capacity is deemed equal to their load when in manual thus lowering the spinning reserve. If inputs are found to be incorrect due to a hardware failure, check that a valid 24Volt dc signal is present back to the PRISMIC terminal block. If the supply is not present check field cabling, If the supply is present replace the faulty digital input card, remembering to check links and address selection switches before re-energising. 4) Check if load-shed test has been selected (If fitted). This will cause the spinning reserve to fall to zero. De-select when not in use. 5) Check if the following preset parameters set correctly, and rectify as necessary: Ø Critical Load Alarm Level Ø Critical Load Alarm Timer Ø Sets Nominal Capacity 6) If the system is in split bus, the critical alarm will work on a `per-bus' basis and the spinning reserve on any bus will `flag up' the critical alarm, even though the overall spinning reserve shown on the system metering indicates sufficient spinning reserve. 7) If an alarm fails to operate, verify output signal is being sent to the interposing output relays and if necessary check back to the alarm output to verify the integrity of the digital output cards, interposing relays and cabling.
  • 165. FAULT FINDING (PRISMIC PMS) Training Module: 07.11.03 Issue: A Date: July 2003 Page: 6 of 8 07.11.03 (A) Fault Finding - PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2003 4.2 Excessive Capacity Alarm 1) Verify that all the on-line machines that are needed to meet the current load requirement are on the switchboard. 2) Where set management is employed verify that it is functioning correctly since sets should be shut down unless a 'minimum sets to run' selection has been made. 3) Verify correct operation of system capacity, system load, and spinning reserve metering as well as on the display system if fitted. Pay particular attention to breaker status signals and machine master fault relay inputs into the PRISMIC system. Check that sets are not selected for manual control since their capacity is deemed equal to their load when in manual thus lowering the spinning reserve. If inputs are found to be incorrect due to a hardware failure, check that a valid 24Volt dc signal is present back to the PRISMIC terminal block. If the supply is not present check field cabling, If the supply is present replace the faulty digital input card, remembering to check links and address selection switches before re-energising. 4) Check that the following preset parameters set correctly, and rectify as necessary: Ø Excessive Capacity Alarm Level. Ø Excessive Capacity Alarm Timer. Ø Sets Nominal Capacity. 5) If the system is in split bus, the excessive alarm will work on a `per-bus' basis in which the excessive spinning reserve on any bus will `flag up' should any of the busses spinning reserve exceed the excessive alarm level for the period of the excessive capacity timer, activating the alarm. 6) If an alarm fails to operate, verify output signal is being sent to the interposing output relays and if necessary check back to the alarm output to verify the integrity of the digital output cards, interposing relays and cabling. 5 FAULT SCENARIOS The logical approach to fault finding is to check all relevant inputs. The most accurate way of checking inputs is not at the terminal boards, but is best achieved using the PRISMIC HMI system which will also check individual card functionality. If a problem persists following a period of planned maintenance, verify that all interlocks and connections to the PMS system are returned to normal operation. In some cases inputs and output signals to the PMS systems may be routed through serial interfaces, if these fail the PRISMIC may not perform as expected if these signals are lost. Detailed hereafter are fault scenarios which provide solutions to various common system malfunction faults. 5.1 Power Sharing Faults a) Power Or Reactive Power Sharing Faulty On One Set With this kind of fault particular attention must be paid to the auxiliary breaker contact inputs into the system and also the auto/manual selection input. PRISMIC will not control a set unless both of these signals are present. The auxiliary breaker signal can sometimes be routed through the generator switchgear master fault relay where any protection operating on that breaker will also remove the 'breaker closed' signal from PRISMIC. The auto/manual signal is sometimes routed through the excitation system, prime mover control system, switchgear and sometimes on offshore applications through the emergency shutdown system. The route of this signal can be determined by reference to contract documentation. If auto/manual is lost, the PRISMIC system will default to Manual control. 1) Check the MW and MVAr values for the faulty set is correct using HMI. Re-calibrate or replace power transducer card as necessary. 2) Verify the MW capability of the prime mover on the HMI. These may be supplied directly from the governor control panel as an analogue signal or may be set on the HMI and tied in with fuel selection and air temperature. This is contract specific information which is detailed in the Operation & Maintenance Manual.
  • 166. FAULT FINDING (PRISMIC PMS) Training Module: 07.11.03 Issue: A Date: July 2003 Page: 7 of 8 07.11.03 (A) Fault Finding - PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2003 3) Confirm that the set has not been selected for a special control mode e.g. Base-load, target load or power factor control mode. 4) Confirm correct operation of the governor, AVR, raise/lower relay logic. 5) Verify that the PRISMIC is issuing raise/lower signals. 6) Verify that the MW or MVAr sharing mismatch is not within the system deadbands. 7) Check for an invalid bus configuration. 8) Check for a switchgear HV fault. 9) Check that no shutdown/offload signals are being given to the PRISMIC from the system (these are contract specific parameters). 10) Verify the correct settings of PRISMIC preset controls. b) Power Or Reactive Power Sharing Common Faults On All Sets 1) Verify voltage and frequency datum's. 2) Verify correct operation of AVR and governor control from the PRISMIC panel. 3) Verify that all voltage/frequency MW and MVAr analogue inputs are reading correctly on HMI. Rectify as necessary. 4) Check all digital inputs to system, including breaker status/auto/manual selection etc. 5) Check preset settings associated with power sharing are correct, i.e. deadbands, pulse settings etc. 5.2 Load Shedding Faults The loads to be shed are divided into non-monitored, where their value is preset in software, and monitored, where transducers monitor their MW values. 1) Check load shed test is not selected (if fitted). 2) Check bus section breaker auxiliary inputs, load breaker auxiliaries and generator breaker auxiliary inputs are working. Correct as necessary or replace the digital input card. 3) Check generator breaker/master trip relay auxiliary inputs. Correct as necessary or replace the digital input card. 4) Check relay and contactor logic associated with load shedding. Correct or replace as necessary. 5) Check preset settings associated with load shedding. 6) Check that the load priority selections are as required and are valid. 7) Check for correct kW signal levels of the generators on the power transducer card. Correct CT, PT or wiring as required, or replace the power transducer card. 8) Check that the load shed guard relay is operating correctly. 5.3 Set Management Faults Set management includes the starting and stopping of sets on either load demand, faulty on-line set or after being manually instigated. Normally, faulty set management can be attributed to the failure of external plant e.g. a diesel engine failing to start. In general the 'set failed to synch' alarm or the 'incorrect duty selection' alarm will be present if such a problem exists. The set management functions detailed may not be provided on all systems and reference should be made to the Operating & Maintenance Manual for contract specific features. a) Checks For Set(s) Not Being Started 1) Verify the correct operation of system capacity, system load, and spinning reserve metering as well as on the display system if fitted. Pay particular attention to stopping and trip logic including the PRISMIC stop and start guard relay. 2) Verify that set(s) have been selected for automatic operation. Check field cabling external switches and interlocks including switchgear, governor AVR etc. Rectify as necessary. 3) Verify that the set(s) have been selected for a valid duty selection. Check field cabling, external switches and interlocks. Rectify as necessary. 4) Check whether any set(s) have failed to synchronise. Check external plant operation including cabling, external switches and interlocks. Check starting logic including the synchronising scheme. Re-prime the system by switching the erroneous set(s) back into manual control and then re-select auto operation. 5) If the system is in split bus, set management will control on a 'per-bus' basis, which often overrides the duty selection.
  • 167. FAULT FINDING (PRISMIC PMS) Training Module: 07.11.03 Issue: A Date: July 2003 Page: 8 of 8 07.11.03 (A) Fault Finding - PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2003 6) Check if an 'unable to start' signal is present with the erroneous set(s) i.e. set critical or emergency shutdown system. 7) Check if the following preset parameters are set correctly, and rectify as necessary: Ø Set Start Margin. Ø Start Timer. Ø Sets Nominal Capacity. Ø Fail to Synch Timer. 8) Check if load-shed test been selected (if fitted). De-select when not in use. b) Checks For Set(s) Not Being Stopped Or Offloaded Correctly The standard system when offloading a set is to lower the governor and AVR datum's to offload both active and reactive load from the set. After a predefined 'cool down period', a breaker trip signal is then issued followed by a prime mover stop signal. Often PRISMIC only issues a stop command to the prime mover control system. 1) Verify correct operation of system capacity, system load, and spinning reserve metering as well as on the display system (if fitted). Pay particular attention to stopping and trip logic including the PRISMIC stop and start guard relay. Rectify as necessary. 2) Verify set(s) been selected for automatic operation. Check field cabling, external switches and interlocks including switchgear, governor, AVR etc. Rectify as necessary. 3) Verify that set(s) have been selected for valid duty selection. Check field cabling, external switches and interlocks. Rectify as necessary. 4) Check if the set(s) have failed to synchronise. Check external plant operation including cabling, external switches and interlocks. Check starting logic including the synchronising scheme. Re-prime the system by switching the erroneous set(s) back into manual control and then re-select auto operation. 5) If the system in is in split bus, set management will control on a 'per-bus' basis, which often overrides the duty selection. Check that there is a valid reason within the system that the set is not stopped i.e. last set on the bars. 6) Check that there is no 'minimum sets to run' type signal present with the erroneous set(s). 7) Check that the following preset parameters set correctly, and rectify as necessary: Ø Set Stop Margin. Ø Stop Timer. Ø Sets Nominal Capacity 8) Where PRISMIC offloads the reactive and active power, check that the pulse lengths are sufficiently long to offload the set. Rectify as necessary. 9) Check if load-shed test been selected (if fitted). De-select when not in use.
  • 168. SYSTEM MAINTENANCE (PRISMIC PMS) Training Module: 07.12.03 Issue: A Date: March 2004 Page: 1 of 8 07.12.03 (A) System Maintenance - PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2004 SYSTEM MAINTENANCE (PRISMIC PMS)
  • 169. SYSTEM MAINTENANCE (PRISMIC PMS) Training Module: 07.12.03 Issue: A Date: March 2004 Page: 2 of 8 07.12.03 (A) System Maintenance - PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2004 CONTENTS 1 INTRODUCTION........................................................................................................................................ 3 2 GENERAL MAINTENANCE ...................................................................................................................... 3 3 ROUTINE CHECKS ................................................................................................................................... 3 4 CALIBRATION OF GENERATORS/GRID FEEDERS.............................................................................. 3 5 CALIBRATION OF LOAD FEEDERS ....................................................................................................... 4 6 LOAD INHIBITS......................................................................................................................................... 4 7 SPINNING RESERVE ALARMS ............................................................................................................... 5 8 SET MANAGEMENT MAINTENANCE...................................................................................................... 5 9 LOAD SHEDDING MAINTENANCE.......................................................................................................... 5 9.1 General................................................................................................................................................ 5 9.2 Gradual Overload Load Shedding....................................................................................................... 5 9.3 Fast Acting Load Shedding................................................................................................................. 6 9.4 Under-Frequency Load Shedding....................................................................................................... 6 10 PRINTERS AND HMI SYSTEMS............................................................................................................... 7 11 RECORDS.................................................................................................................................................. 7
  • 170. SYSTEM MAINTENANCE (PRISMIC PMS) Training Module: 07.12.03 Issue: A Date: March 2004 Page: 3 of 8 07.12.03 (A) System Maintenance - PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2004 1 INTRODUCTION Regular planned maintenance can detect early signs of failures or problems in the PRISMIC System. Most features, e.g. load shedding, might remain unused for extended periods and a general malfunction will not be detected until it has failed to operate. The PRISMIC Power Management System has a dependable record in the field although it relies on the external hardware performing correctly. Due to the diversity of equipment on the Customer site, the trend these days is to arrange service contracts with the supplier of the equipment. Brush offers a rapid response service on all Brush equipment, including machines, should a problem arise on site. 2 GENERAL MAINTENANCE Among the most common causes of failure within an electrical control room are: Ø Loose Connections. Ø Dirty or Oxidised Contacts. Ø Insufficient Contact Pressure. Ø Pitted Surfaces. Thus, equipment should be maintained in a clean condition, and panel doors should be kept closed whenever possible. Equipment should be checked for mechanical soundness to ensure that components are secure, particularly those with moving parts such as relays and switches etc. Caution must be observed whilst checking relays as certain relays can trip and close switchgear. Maintenance of auxiliary equipment such as synchronisers etc. fitted in the PRISMIC panel is important and guidance is given in the appropriate Instruction Manual/Handbook. Where the PRISMIC panel is in close proximity to a diesel engine, it is worthwhile checking the panel for ingress of carbon deposits. If the PRISMIC cards have become coated, switch off and carefully remove one card at a time and dust down with a soft brush. Avoid touching the card's edge connectors. Do not remove or replace cards while the rack is powered-up. Take care with Power Transducer cards, as 50V ac is present at all times sets are on line. 3 ROUTINE CHECKS Ø Verify correct operation of the lamp test facility, if provided (Panels fitted with LED indication do not require this facility). Ø Verify that the master fault relay is energised within the panel. Ø Verify all cards being cycled correctly by checking the card 'access' LED is illuminated on all I/O cards. Ø Check all cards are positively located in the I/O slots. Ø Check for charring and hot components, especially relays that are continually energised. Ø Generally check security of connection links etc. Ø Check tightness of all ribbon cables and panel terminals. 4 CALIBRATION OF GENERATORS/GRID FEEDERS Confirm the accurate calibration of inputs to the Power Transducer cards by checking the PRISMIC MW readings against a known accurate source. If a HMI system is present this information can be read off the screen. Note: Ensure when calibrating or trimming these cards to revert to MANUAL selection before proceeding with card tests. The offset controls can be verified by using the CT shorting links commonly found in PRISMIC panels. Verify calibration of the bus voltage measurements. These are normally fed into an analogue input on an analogue input card. Calibration is through potentiometers on the AI card front panel.
  • 171. SYSTEM MAINTENANCE (PRISMIC PMS) Training Module: 07.12.03 Issue: A Date: March 2004 Page: 4 of 8 07.12.03 (A) System Maintenance - PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2004 5 CALIBRATION OF LOAD FEEDERS When each load feeder is monitored for load shedding it is important that the calibration is correct, else too much or too little load will be shed during a load shedding situation. Normally, the Analogue Input card is used for this function. Verify the correct operation of each channel using an 'in-line' watt meter where possible. The analogue card will normally be fed from a 4-20mA transducer, either in the panel or externally in the switchgear. Offset and gains are available on each channel to trim any inaccuracies within the system. Where possible verify all digital input channels. This may be impossible on a 'on-line' system. Ensure that no sequences are initiated as the result of certain inputs being energised. Where the PRISMIC drives analogue meters, use the data module to check calibration by referring to the card function sheets found in the Operating & Maintenance Manual. Check system capacity, system load and spinning reserve values on meters (if fitted) and on the HMI system. The following tests involve placing voltage and frequency fluctuation on the system, as well as power and VAr swings between sets: Ø Ensure this will have no detrimental effect on on-line systems. Ø Ensure no electrical protection relays will operate as a result of the tests before commencing. Ø Where possible, run extra generators to improve system security. 1) AVR Control - Voltage Control, Islanded Control Place all sets under MANUAL control, manually reduce AVR datums on all sets. Switch back to AUTO and verify that the line volts on the bus-bar return to nominal setting. Verify that no instability is present. Adjust volts stabilising control if instability is found. Repeat, this time taking the datums above nominal volts. 2) AVR Control - VAr Sharing, Islanded Control By placing one set under MANUAL control, reduce the AVR datum on that machine. Switch back to AUTO and verify that the PRISMIC matches the machines VArs to the other machines. Repeat, this time increasing the AVR datum. Repeat on remaining sets. Reset stability settings if necessary. 3) Governor Control - Frequency, Islanded Control Place all sets under MANUAL control, manually reduce the governor datum so the bus frequency falls below nominal. Return all sets to AUTO operation and check all governor datums are raised to obtain the nominal system frequency. Repeat, increasing the governor datums above nominal. Reset stability setting if necessary. 4) Governor Control - Power Sharing, Islanded Control By placing one set under MANUAL control, reduce the governor datum on that machine. Switch back to AUTO and verify PRISMIC returns the machine's MW to match with other interconnected machines. Repeat, this time increasing the governor datum. Repeat in remaining sets. Reset stability settings if necessary. 5) Grid Controls (When Utilised) Perform a similar exercise as above on the AVR and governor settings, but check the MW and VArs are returned to their target valves. Reset stability settings if instability occurs. 6 LOAD INHIBITS To prove this mode of operation the spinning reserve has to be reduced sufficiently to initiate load inhibit signals. It is important to know that if this reduces below zero then load shedding can occur. By carefully reducing the nominal MW capacity of each of the sets, the load inhibit signals should be initiated when the spinning reserve falls below the preset restart MW value, assuming the breaker is open. Verify that this happens and check the preset settings when using this function.
  • 172. SYSTEM MAINTENANCE (PRISMIC PMS) Training Module: 07.12.03 Issue: A Date: March 2004 Page: 5 of 8 07.12.03 (A) System Maintenance - PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2004 Placing low loaded sets under MANUAL control can also reduce the spinning reserve, reducing MW on a manually selected set will also perform the same function. 7 SPINNING RESERVE ALARMS To verify correct operation of the critical spinning reserve alarm, the spinning reserve has to fall below the critical spinning reserve set level for the duration of the critical spinning reserve timer. This can be achieved in the same way as for the testing of the load inhibits above. To verify correct operation of the excessive spinning reserve alarm, the spinning reserve has to rise above the excessive spinning reserve set level for the duration of the excessive spinning reserve timer. This can be achieved by either bringing extra sets on-line or by temporarily increasing each of the on-line sets' capacity. Take particular care not to decrease the capacity such that load shedding operates. Record spinning reserve levels and timers. 8 SET MANAGEMENT MAINTENANCE Verify where possible the correct operation and sequence of the starting and stopping of sets feature. Check for correct operation of the incorrect duty selection alarm by selecting an invalid selection. The 'Fail to Synch' alarm may be checked by isolating the switchgear closing fuse associated with the set being started. Verify 'Minimum Sets to Run' feature if fitted. Record preset values associated with the set management feature including levels and timers. 9 LOAD SHEDDING MAINTENANCE 9.1 General To perform a test on a system will require running the system with the output trip relays isolated. It is recommended that extra generating plant is put on-line during this period if the system is being utilised for production. Isolating the 'load shed guard relay' will inhibit the trip relays. Care must be taken with removing individual trip relays, as often, the trip circuit is 'open to trip'. Tripping breakers on a HV scheme is of prime importance as often it is the 'last ditch' attempt to protect electrical plant under fault conditions other than the manual trip button on the switchgear mechanism. Tripping a breaker either locally, via protection schemes, or from a remote location, normally electrically energises a trip coil which releases the switchgear mechanism. Two schools of thought exist on the tripping philosophy, often based on voltage rating and reliability of the system: 1) Open To Trip Whilst this ensures that the breaker trips should any trip circuit cabling fail, it reduces the reliability of the system as well as reducing the integrity of the trip coil as it is permanently energised. 2) Close To Trip Systems using this method of tripping often use trip circuit supervision protection relays to verify any cable breaks, trip fuse failure, loss of dc tripping supply or trip coil failures within the switchgear panel. Should a fault be detected an alarm will 'flag up' rather than the breaker trip. Trip circuit cabling is often doubled up to improve the tripping circuit integrity. 9.2 Gradual Overload Load Shedding Ø It is recommended that extra generating plant is put on-line during this period if the system is being utilised for production. Ø By isolating the 'load shed guard relay' this will inhibit the trip relays, care must be taken with removing individual trip relays as often the trip circuit is 'open to trip'.
  • 173. SYSTEM MAINTENANCE (PRISMIC PMS) Training Module: 07.12.03 Issue: A Date: March 2004 Page: 6 of 8 07.12.03 (A) System Maintenance - PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2004 Ø With the load shedding output relays isolated reduce the spinning reserve below zero by placing several in manual and reducing the MW on the sets selected manual onto the auto selected sets verify that the gradual overload timer store on the diagnostic unit starts to integrate up until the first load `trips' (as indicated on the HMI or on an annunciator) and then as the load has not physically been tripped off the switchboard further trips will emanate from the PRISMIC system as there is still a simulated overload condition. Ø The duration of the distance between trip signals is referred to as the 'retrip timer'. Ø Verify correct operation of the gradual overload Load shedding feature and record the settings of the gradual overload timer, retrip timer, trip pulse length. Re-adjust if necessary. Ø Re-install any equipment that has been isolated or by-passed. Should this feature not operate correctly refer to the contract documentation for any contract specific variants and if not refer to PRISMIC PMS Fault Finding section. 9.3 Fast Acting Load Shedding Ø It is recommended that extra generating plant is put on-line during this period if the system is being utilised for production. Ø By isolating the 'load shed guard relay' this will inhibit the trip relays, care must be taken with removing individual trip relays as often the trip circuit is 'open to trip'. Ø With the load shedding output relays isolated simulate a generator having been tripped off the board either by removing the breaker auxiliary input or the master fault relay contacts into the PRISMIC system. Assuming this has caused the spinning reserve to go negative instant load shedding will be instigated (as indicated on the HMI or on an annunciator) and then as the load has not physically been tripped off the switchboard further trips will emanate from the PRISMIC system as there is still a simulated overload condition. Ø The duration of the distance between trip signals is referred to as the 'retrip timer'. Verify correct operation of the fast acting Load shedding feature and record the settings of the retrip timer, trip pulse length. Re-adjust if necessary. Ø Re-install any equipment that has been isolated or by-passed. Should this feature not operate correctly refer to the contract documentation for any contract specific variants and if not refer to the PRISMIC PMS Fault finding section. 9.4 Under-Frequency Load Shedding Ø It is recommended that extra generating plant is put on-line during this period if the system is being utilised for production. Ø To verify the correct operation of this PRISMIC feature it is required that the busbar frequency be lowered. Normally this will not cause the switchgear to trip out as the protection scheme is normally set lower than the PRISMIC under-frequency trip levels but can cause UPS systems to produce under-frequency alarms. Ø By isolating the 'load shed guard relay' this will inhibit the trip relays, care must be taken with removing individual trip relays as often the trip circuit is 'open to trip'. Ø With the load shedding output relays isolated place all sets into manual control and physically isolate all the PRISMIC raise governor relays. Ø Reduce all the governors manually so that the bus frequency falls below the under-frequency trip level and switch all sets back into PRISMIC control. Ø After the under-frequency timer has timed out load shedding will be instigated (as indicated on the HMI or on an annunciator although trips electrically isolated). One load will then be shed, further tripping of single loads will then proceed the time between these trips are the setting of the re-trip timer. Although in the real world PRISMIC would have corrected the governors to increase the bus frequency to nominal tripping would be halted when the bus frequency rose above the under-frequency recovery level. Ø Verify correct operation of the under-frequency load shedding feature and record the settings of the following: Ø Under-frequency trip level Ø Under-frequency recovery level Ø Under-frequency trip timer Ø Under-frequency recovery timer Ø Re-adjust if necessary. Ø Re-install any equipment that has been isolated or by-passed.
  • 174. SYSTEM MAINTENANCE (PRISMIC PMS) Training Module: 07.12.03 Issue: A Date: March 2004 Page: 7 of 8 07.12.03 (A) System Maintenance - PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2004 Should this feature not operate correctly refer to the contract documentation for any contract specific variants and if not refer to the PRISMIC PMS Fault Finding section. Various systems have a stage two under-frequency load shedding system where should the system receive a severe under frequency condition blocks of loads are shed. This can be proved out in the same way as the stage one under-frequency although the trip levels are normally set lower and could possibly clash with the switchgear under-frequency protection relays. In this case move the trip set point temporarily higher and verify at a different setting. 10 PRINTERS AND HMI SYSTEMS Although covered by suppliers manuals/handbooks, generally ensure the monitors and printers are clean. Ø The screen may be cleaned with a proprietary anti-static foam cleaner whilst the printer mechanism may be cleaned with a soft brush. Ø Check printer ribbons are serviceable and an adequate supply of paper is available. Most printers have test modes to check the mechanisms, refer to the suppliers manual/handbook for more details. Ø Verify condition of all cables and connectors where applicable to the Health and Safety at Work guidelines for mains portable and transportable equipment. 11 RECORDS Record all preset parameters including load shedding tables.
  • 175. SYSTEM MAINTENANCE (PRISMIC PMS) Training Module: 07.12.03 Issue: A Date: March 2004 Page: 8 of 8 07.12.03 (A) System Maintenance - PRISMIC PMS.doc © Brush Electrical Machines Ltd. 2004 BLANK PAGE

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