Bhel haridwar vocational training report block 1

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BHEL HARDWAR training report

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Bhel haridwar vocational training report block 1

  1. 1. BHEL HARIDWAR VOCATIONAL TRAINING REPORT “BHARAT HEAVY ELECTRICAL S LIMITED” RANIPUR ,HARIDWAR (UTTARAKHAND ) Submitted By : Khemraj Bairwa 2010UEE232 MNIT ,JAIPUR (RAJ.)
  2. 2. ACKNOWLEDGEMENT “An engineer with only theoretical knowledge is not a complete engineer. Practical knowledge is very important to develop and to apply engineering skills”. It gives me a great pleasure to have an opportunity to acknowledge and to express gratitude to those who were associated with me during my training at BHEL. Special thanks to Mr. Tariq Husan for providing me with an opportunity to undergo training under his able guidance. I express my sincere thanks and gratitude to BHEL authorities for allowing me to undergo the training in this prestigious organization. I will always remain indebted to them for their constant interest and excellent guidance in my training work, moreover for providing me with an opportunity to work and gain experience.
  3. 3. INDEX 1. INTRODUCTION 2.BHEL’S CONTRIBUTION IN DIFFERENT SECTORS 3. BHEL HARIDWAR – AN OVERVIEW 4. TURBO GENERATORS a) STATOR i) STATOR FRAME ii) STATOR CORE iii) STATOR WINDING iv) END COVERS b) ROTOR i) ROTOR SHAFT ii) ROTOR WINDING iii) ROTOR RETAINING RINGS iv) ROTOR FANS c) BEARINGS d) VENTILATION AND COOLING e) EXCITATION SYSTEM f) TESTING g) MOTOR WINDING 5. CONCLUSION
  4. 4. BHEL - AN OVERVIEW INTRODUCTION In 1956 India took a major step towards the establishment of its heavy engineering industry when Bharat Heavy Electricals Limited, the first heavy electrical manufacturing unit of the country was set up at Bhopal. It progressed rapidly and three more factories went into production in 1956 .The aim of establishment BHEL was to meet the growing power requirement of the country. BHEL has supplied 97% of the power generating equipment that was commissioned in India during 1979-80. BHEL has supplied generating equipment to various utilities capable of generating over 18000MW power. BHEL is one of the largest power plant equipment manufacturing firms in India and it ranks among the top ten manufacturers globally. BHEL has covered up many power stations over 40 countries worldwide. BHEL has its head quarters at New Delhi. Its operations are spread over 11 manufacturing plants and number of engineering and service divisions located across the country. The service division includes a network of regional offices throughout India. BHEL’S UNIT IN INDIA S.No. PLACE UNITS (PLANTS) 1. HARDWAR 2 2. BHOPAL 1 3. JHANSI 1 4. JAGDISHPUR 1 5. HYDERABAD 1 6. BANGALORE 3 7. RANIPET 1 8. RUDRAPUR 1
  5. 5. A BRIEF HISTORY The first plant of what is today known as BHEL was established nearly 40 years ago at BHOPAL and was genesis of Heavy Electrical Equipment industry in India. BHEL is today the largest engineering enterprise of its kind in India, with a well recognized track record of performance making profits continuously since 1971-72. It achieved a sales turnover of Rs.1022 core in 1997-98. BHEL caters to core sectors of the Indian Economy via, Power, Industry, Transportation, Defense, etc. The wide network of BHEL’s 14 manufacturing divisions, 9 service centers & 4 power Sector Regional centers & about 150 project sites enables the service at competitive prices. Having attained ISO 9000 certification, BHEL is now embarking upon the Total Quality Management. The company’s inherent potential coupled with its strong performance over the years, has resulted in it being chosen as one of the ― Maharatna PSUs(on 1 February 2013 ), which are to be supported by the Government in their endeavor to become future global players. It is the 7th largest power equipment manufacturer in the world. In the year 2011, it was ranked ninth most innovative company in the world by US business magazine Forbes. BHEL is the only Indian Engineering company on the list, which contains online retail firm Amazon at the second position with Apple and Google at fifth and seventh positions, respectively. It is also placed at 4th place in Forbes Asia's Fabulous 50 List of 2010
  6. 6. BHEL’S CONTRIBUTION IN DIFFERENT SECTORS  POWER SECTOR Power sector comprises thermal, nuclear, gas & hydro power plant business. Today, BHEL supplied sets account for nearly 56,318 MW or 65% of the total installed capacity of 86,636 MW in as against nit till 1969-1970. BHEL has proven turnkey capabilities for executing power projects from concept to commissioning. It posses the technology and capability to produce thermal power plant equipments up to 1000MW rating and gas turbine generator sets up to a unit rating of 240 MW. Cogeneration and combined cycle plants have been introduced to achieve higher plant efficiencies. To make efficient use of the high ash content coal available in India, BHEL supplies circulating fluidized bed boilers to thermal and combined cycle power plants. BHEL manufacturers 235 MW nuclear turbine generator sets and has commenced production of 500 MW nuclear turbine generator sets. Custom-made hydro sets of Francis, Pelt on and Kaplan types for different head-discharge combinations are also engineered and manufactured by BHEL is based upon contemporary technology comparable to the best in the world & is also internationally competitive.  Transmission BHEL also supplies a wide range of transmission products and systems up to 400 KV Class. These include high voltage power and distribution transformers, instrument transformers, dry type transformers, SF6 switchgear, capacitors, and insulators etc. For economic transmission bulk power over long distances, High Voltage Direct Current (HVDC) systems are supplied. Series and Shunt Compensation Systems have also been developed and introduced to minimize transmission losses.
  7. 7. A strong engineering base enables the Company to undertake turnkey delivery of electric substances up to 400 kV level series compensation systems (for increasing power transfer capacity of transmission lines and improving system stability and voltage regulation), shunt compensation systems (for power factor and voltage improvement) and HVDC systems (for economic transfer of bulk power). BHEL has indigenously developed the state-of-the-art controlled shunt reactor (for reactive power management on long transmission lines). Presently a 400 kV Facts (Flexible AC Transmission System) project under execution.  Transportation A high percentage of trains operated by Indian Railways are equipped with BHEL’s traction and traction control equipment including the metro at Calcutta. The company supplies broad gauge electrical locomotives to Indian Railways and diesel shunting locomotives to various industries.5000/6000 hp AC/DC locomotives developed and manufactured by BHEL have been leased to Indian Railways. Battery powered road vehicles are also manufactured by the company.  International Operations BHEL’s products, services and projects have been exported to over 50 countries ranging from United States in the west to New Zealand in far East. The cumulative capacity of power generating equipment supplied by BHEL outside India is over 3000MW. The company’s overseas presence includes projects in various countries. A few notable ones are : 150 MW (ISOI) gas turbine to Germany, utility boilers and open cycle gas turbine plants to Malaysia, Tripoli-west, power station in Libya executed on turnkey basis, thermal power plant equipment to Malta and Cyprus, Hydro generators to new Zealand and hydro power plant equipment to Thailand. BHEL has recently executed major gas-based power projects in Saudi Arabia and Oman, a Boiler contract in Egypt and several Transformer contracts in Malaysia and Greece  RENEWABLE ENERGY:- Technologies offered by BHEL for non-conventional and renewable sources of energy include: wind electric generators, solar photovoltaic system, stand alone and grid-interactive
  8. 8. solar power plants, solar heating systems, solar lanterns and battery-powered road vehicles. The company has taken up R&D efforts for development of multi-junction amorphous solar cells and fuel cells based systems.  INDUSTRIES BHEL is a major contributor of equipment and systems to industries: cement, sugar, fertilizer, refineries, petrochemicals, paper, oil and gas, metallurgical and process industries. The company is a major producer of large-size thyristor devices. It also supplies digital distributed control system for process industries and control & instrumentation systems for power plant and industrial application. The range of system & equipment supplied includes: captive power plants, co- generation plants DG power plants, industrial steam turbines, industrial boilers and auxiliaries. Water heat recovery boilers, gas turbines, heat exchangers and pressure vessels, centrifugal compressors, electrical machines, pumps, valves, seamless steel tubes, electrostatic precipitators, fabric filters, reactors, fluidized bed combustion boilers, chemical recovery boilers and process controls. The Company is a major producer of large-size thruster devices. It also supplies digital distributed control systems for process industries, and control & instrumentation systems for power plant and industrial applications. BHEL is the only company in India with the capability to make simulators for power plants, defense and other applications
  9. 9. BHEL HARIDWAR An Overview At the foothills of the majestic Himalayas & on the banks of a holy Ganges in Ranipur near HARIDWAR is located Heavy Electricals Equipment Plant of Bharat Heavy electrical Ltd. BHEL, wholly owned by the government of India is an integrated engineering complex consisting of several plants in India, where about 70,000 workers are busy in design & manufacturing of a wide range of heavy electrical equipment. At present 70% of the Country’s electrical energy is generated by the sets manufacturing by BHEL, Haridwar BHEL HARDWAR is broadly divided in to two parts: A) - CFFP: – Central Foundry Forge Plant B) - HEEP: – Heavy Electrical Equipment Plant A) - CFFP is divided in to following shops:  Forge Shop  Machine Shop  Steel Melting Shop (SMS)  Steel Foundry  Pattern Shop  Cast Iron (CI) Foundry B) - HEEP is divided into following blocks:  BLOCK-1 Turbo Generators, AC Machines  BLOCK-2 Fabrication (Steam, Hydro & gas Turbine)  BLOCK-3 Gas & Steam Turbine  BLOCK-4 CIM (Coil & Insulation Manufacturing) & ACG (Apparatus control Gear)  BLOCK-5 Heat exchangers, Forging and Fabrication  BLOCK-6 Stamping  BLOCK-7 Wooden Packing works  BLOCK-8 Fabrication, seamless tubes and heat exchanger
  10. 10. TURBO GENERATOR The AC generator or alternator is based on the principle of electromagnetic induction and consist generally of a stationery part called Stator and a rotating part called Rotor. Stator houses the armature winding. The rotor houses the field winding. DC voltage is applied to field winding through the slip rings. When the rotor rotates, the lines of magnetic flux cut through the winding. This induces an electromagnetic EMF in the stator winding. The magnitude of emf is given by following formula E = 4.44* ø *ƒ*N volt Where ø = strength of magnetic field ƒ = frequency in hertz N = number of turn in stator winding ƒ = frequency = P*n / 120 where, P = number of poles n = number of revolution per second of rotor
  11. 11. SYNOPSIS OF THE FUNCTION OF TURBO GENERATOR :  The generator rotor is driven by prime mover and on driver side gas/ diesel/ steam hydro depending on the equipment to which it is meant for.  The non-drive side of rotor is equipped with a rotating side of armature which produces AC voltage. This is rectified to DC by using a DC commutator / rotating diode wheel depending upon the type of exciter.  The rear end of above exciter armature is mounted with a permanent magnet generator rotor.  As the above rotating system put into operation, the PMC produces AC voltage.  The voltage is rectified by thyristor circuit to DC.  This supply is given to exciter field. This field is also controlled by taking feedback from main generator terminal voltage, to control exciter field variation by automatic voltage regulator. The rectified DC supply out of exciter is supplied to turbo generator rotor winding either through brushes or central which will be directly connected to turbo generator. This depends on the type of exciter viz. DC commutator machines or brushes exciter.  The main AC voltage of generator is finally available to turbo generator stator.
  12. 12. LARGE SIZE TURBO GENERATOR (LSTG) These types of generators are those which has taken steam turbine. Their prime mover and current is supplied by exciter system. Main types are:- 1. THRI 2. TARI 3. THDI 4. THDD 5. THDF 6. THFF Basic terms are:- T = turbo generator A = air cooled H = hydrogen cooled R = radial cooling with gas D = direct axial cooling with gas F = direct axial cooling with water I = indirect cooling
  13. 13. COMPONENTS OF T.G. :- STATOR –  Stator frame  Stator core  Stator winding  End covers ROTOR –  Rotor shaft  Rotor winding  Rotor retaining rings. BEARINGS COOLING SYSTEM EXCITATION SYSTEM. STATOR - The generator stator is a tight construction supporting and enclosing stator winding, core and hydrogen cooling medium. Hydrogen is contained within frame and circulated by fans mounted at either end of rotor. The generator is driven by direct coupled steam turbine at the speed of 3000 rpm.The generator is designed for continuous rated output. Temperature detector and other device installed or connected within machine, permit the windings core and hydrogen temperature, pressure, and purity in machine.
  14. 14. STATOR FRAME – Stator body is a totally enclosed gas tight fabricated structure made up of high quality mild steel and austenitic steel. It is suitably ribbed with annular rings in inner walls to ensure high rigidity and strength and it also help to reduce vibration and to withstand the gas thermal pressure .The arrangement, location and shape of inner walls is determined by the cooling circuit for the flow of the gas and required mechanical strength and stiffness. The natural frequency of the stator body is well away from any of exiting frequencies. Inner and sidewalls are suitably blanked to house for longitudinal hydrogen gas coolers inside the stator body. It supports the laminated core and winding the stator comprises an inner frame and outer frame. The inner cage is usually fixed in the yoke by an arrangement of spring to damper the double frequency vibrations inherent in two pole generator. The fabricated inner cage is inserted in the outer frame after the stator core has been constructed and the winding completed. Footings are provided the stator foundation shields enclose the ends of heavy end frame and form mounting of generator bear and radial shaft. R is subdividing the frame and axial members to form ducts from which the cooling given to end from radial duct in the core and is recirculated. The horizontally mounted water cooled gas coolens being so arranged the it may be cleaned on the water side without opening the machine to atmosphere. All welded joints exposed to hydrogen are specially made to prevent leakage. The complete frame is subjected to hydraulic test at a pressure of 7 atm.
  15. 15. STATOR CORE – It consists of thin laminations. Each lamination made of number of individual segments. Segments are stamped out with accurately finished die from the sheets of cold rolled high quality silicon steel.Before insulation on with varnish each segment is carefully debarred. Core is stacked with lamination segments. Segments are assembled in an interleaved manner from layer to layer for uniform permeability. Stampings are held in a position by 20 core bars having dovetail section. Insulating paper pressboards are also put between the layer of stamping to provide additional insulation and to localize short circuit. Stampings are hydraulically compressed during the stacking procedure at different stages. Between two packets one layer of ventilating segments is provided. Steel spacers arespot welded on stamping. These spacers from ventilating ducts where the cold hydrogen from gas coolers enter the core radialy inwards there by taking away the heat generated due toeddy current losses. The pressed core is held in pressed condition by means of two massive non- magnetic steel castings of press ring. The press ring is bolted to the ends of core bars. The pressure of the pressure ring is transmitted to stator core stamping through press fringes of non-magnetic steel and duralumin placed adjacent to press ring. To avoid-heating of press ring due to end leakage flow two rings made of copper sheet are used on flux shield. The ring screens the flux by short-circuiting. To monitor the formation of hot spots resistance transducer are placed along the bottom of slots. To ensure that core losses are within limits and there are no hot spots present in the core. The core losstest is done after completion of core assembly. The main features of core are – 1. To provide mechanical support 2. To carry efficiently electric, magnetic flux. 3. To ensure the perfect link between core and rotor.
  16. 16. STATOR WINDING – The stator has a three phase, double layer, short pitched and bar type of windings having two parallel paths. Each slots accommodated two bars. The slot lower bars and slot upper are displaced from each other by one winding pitch and connected together by bus bars inside the stator frame in conformity with the connection diagram. Each bar consists of solid as well as hollow conductor with cooling water passing through the latter. Alternate arrangement hollow and solid conductors ensure an optimum solution for increasing current and to reduce losses. The conductors of small rectangular cross section are provided with glass lapped strand insulation. A separator insulates the individual layers from each other. The transposition provides for mutual neutralization of voltage induced in the individual strands due to the slots cross field and end winding field. The current flowing through the conductor is uniformly distributed over the entire bar cross section reduced. To ensure that strands are firmly bonded together and give dimensionally stability in slot portion, a layer of glass tape is wrapped over the complete stack. Bar insulation is done with epoxy mica thermosetting insulation. This insulation is void free and posses better mechanical properties. This type of insulation is more reliable for high voltage. This insulation shows only a small increase in dielectric dissipation factor with increasing test voltage. The bar insulation is cured in an electrically heated process and thus epoxy resin fill all voids and eliminate air inclusions.
  17. 17. INSULATION OF BARS –  Vacuum pressed impregnated mica elastic high voltage insulation: The voltage insulation is provided according to the proven resin poor mice base of thermo setting epoxy system. Several half overlapped continuous layer of resin poor mica tape are applied over the bars. The number of layers or thickness of insulation depends on the machine voltage. To minimize the effect of radial forces windings hold and insulated rings are used to support the overhang.  Corona protection: To prevent the potential difference and possible corona discharges between the insulation and the slot wall, the section of bars are provided with outer corona protection. The protection consists of polyester fluce tape impregnated in epoxy resin with carbon and graphite as fillers. At the transition from the slot to the end winding portion of the stator winding portion of stator bars a semiconductor tape made up old polyester fluce is impregnated.  Resistance temperature detector : The stator slots are provided with platinum resistance thermometer to record and watch the temperature of stator core and tooth region and between the coil sides of machine in operation. All AC machines rated for more than 5 MVA or with armature core longer the machine is to be provided with at least 6 resistance thermometers of their couples which shall built inside the stator suitably distributed among the circumference at the likely hottest point. The thermometer should be fixed in the slot but outside the coil insulation. When the winding has more than one coil side per slot, the thermometer is to be placed between the insulated coil sides. The length of the resistance thermometer depends upon the length of armature. The leads from the detectors are brought out and connected to the terminal board for connection to temperature meter or relays operation of RTD is based on the prime that the “electric resistance of metallic conductor varies linearly with temperature.”
  18. 18. END COVERS – The end covers are made up of fabricated steel or aluminum castings. They are employed with guide vans on inner side for ensuring uniform distribution of air or gas. ROTOR Rotor revolves in most modern generator at speed of 3000 revolutions per minute. It is also as electromagnet and to give it necessary magnetic strength, the winding must carry a very high current. The passage of current through windings generates heat. But the temperature must not be allowed to become too high, otherwise difficulties will be experienced with insulation. To keep the temperature cross section of the conductors could not be increased but this would introduce another problems. In order to make
  19. 19. room for large conductor, body and this would cause mechanical weakness. With good design and great care this problem can be solved. ROTOR SHAFT –
  20. 20. Details of shaft are given here – Length = 9 meter (approx.) Diameter = 1 meter (approx.) Material – alloy steel Number of poles = 2 The rotor shaft is cold rolled forging 26N1 or MOV116 grade and it is imported from Japan and Italy. Rotor shaft is a single piece forming manufactured castings. It is forged from a vacuum cast steel slots for insulation of the field winding are made into the rotor body. The longitudinal slots are distributed over the circumference. To ensure that a high quality product is obtained, strength of material analysis and ultrasonic are performed during the manufacturing rotor. The high mechanical stress resulting from the centrifugal force and short circuit, torque called for a high specified mechanical and magnetic properties as well as homogenous forging. After completion, the rotor is balanced in the various planes and different speed and then subjected to an over speed test at 120% of rotor speed. The rotor consist of electrically active portion and two shaft end approximately 60 b% of rotor body circumference have longitudinal slots which holds the field winding. Slots pitch is selected so that the two solid poles are displaced by 180 degree the rotor wedges act as damper winding within the range of winding slots. The rotor teeth at the rotor body are provided in radial and axial poles enabling cooling air to be discharged. ROTOR WINDING –
  21. 21. The winding consist of several coils inserted into the slots and the series connected such that two coils group to form one pole. Each coil consist of several series connected turns each of which consist of two half turns connected by brazing in end section. The individual turn of coil are insulated against each other by interlayer insulation. L-shaped strip of laminated epoxy glass fiber with nomex filter are used for slot insulation. The slot wedges are made up of high electrical conductivity material and thus act as damper winding. At their ends, the slots wedges are short circuited through the rotor body. When rotor is rotating at high speed, the centrifugal forces tries to lift the winding out of slots, they are contained by wedges. CONSTRUCTION – The field winding consist several series connected coils into the longitudinal slots of body. The coil are wound that two poles are obtained. The solid conductors have a rectangular cross-section and are provided axial slots for radial or cooling air. All conductors have identical copper and cooling section. CONDUCTOR MATERIAL – The conductors are made up of copper with silver content of approx. 0.1% . As compared to electrolytic copper silver alloyed copper features high strength properties at high temperature so that coil deformations due to thermal stresses are eliminated. The conductors are made of hard drawn silver bearing copper. The rectangular cross section copper conductors have ventilating ducts on the two sides thus providing a channel for hydrogen flow. Two individual conductors placed-one over the other are bent to obtain half turns. Further these half turns are brazed in series to form coil on the rotor model
  22. 22. INSULATION – The insulation between the individual turns is made up of layer of glass fiber laminate the coils are insulated from the rotor body with L-shaped strip of glass fiber laminate with nomex interlines to obtain the required leakage path between the coil and rotor body thick top strips of glass fiber laminate are inserted below wedge. The top strip are provided with axial slots of same cross-section and spacing and used on the rotor winding. END WINDING BRACING – The spaces between the individual’s coils in the end working are with insulated members that prevent coil movement the insulation by H or L high glass lamination. ROTOR RETAINING RINGS – The centrifugal forces of the end windings are contained by piece rotor retaining rings. Retaining rings are made u of non-magnetic high strength steeling order to reduce the stray losses. Each retaining rings with its shrink fitted. Insert ring is shrunk on the rotor is an overhang position. The retaining ring is secured in the axial position by snap rings. The rotor retaining rings withstand the centrifugal forces due to end winding. One end of each ring is shrunk fitted on the rotor body while the other hand overhangs the end winding without contact on the rotor shaft. This ensures unobstructed shaft deflection at end windings. The shrunk on hub on the end of the retaining ring serves to reinforce the retaining ring and serves the end winding in the axial direction. At the same time, a snap ring is provided against axial displacement of retaining ring. The shrunk slot of current. To reduce the stray losses and have high strength, the rings are made up of non-magnetic cold worked material.
  23. 23. ROTOR FANS – The cooling air in generator is cold by two axial flow fans located at the rotor shaft one at each end augment the cooling of the winding. The pressure established by the works in conjunction with the expelled from the discharge path along the rotor. The blades of fan have threaded roots for screwed into the rotor shaft. Blades are drop forged from aluminum alloy. Threaded root fastenings permit angle to be changed. Each blade is screwed at its root with a threaded pin. BEARINGS The turbo generators are provided with pressure lubricated self-aligning type bearing to ensure higher mechanical stability and reduced vibration in operation. The bearings are provided with suitable temperature element due to monitor bearing metal temperature in operation. The temperature of each bearing monitored with two RTD’s (resistance thermo detector) embedded in the bearing sleeve such that the measuring point is located directly below Babbitt. These RTDs are monitored temperature scanner in the control panel and if the temperature exceeds the prescribe limit. Bearing have provision for vibration pickup to monitor shaft vibration. To prevent damage to the journal due to shaft current, bearings and coil piping on either side of the non-drive and bearings are insulated from the foundation frame. For fascinating and monitoring the healthiness of bearing insulation, shaft insulation is provided.
  24. 24. VENTILATION AND COOLING SYSTEM VENTILATION SYSTEM- The machine is designed with ventilation system having rated pressure. The axial fans mounted on either side of rotor ensure circulation of hydrogen gas. The rotor is designed for radial ventilation by stem. The end stator is packets and core clamping and is intensively cooled by through special ventilation system. Design of special ventilation is to ensure almost uniform temperature of rotor windings stator core. Embedded resistance temperature detector do continuous monitoring of hydrogen temperature at part of generator COOLING SYSTEM – STATOR COOLING SYSTEM – The stator winding is cooled by distillate water which is fed from one end of the machine by Teflon tube and flows through the upper bar and returns back through the lower bar of a slot. Turbo generator requires water cooling arrangement over and above the usual hydrogen cooling arrangement. The stator is cooled in this system by circulating demineralized water trough hollow conductors. The cooling was used for cooling of stator winding and for the use of very high quality of cooling water. For this purpose DM water of proper specifying resistance is selected. Generator is to be loaded within a very short period. If the specific resistance of cooling DM water goes beyond preset value. The system is designed to maintain a constant rate cooing water flow through the stator winding at a nominal inlet with temperature of 40 degree centigrade. As it is look working, the cooling water is again cooled by water which is also demineralized to avoid contamination with any impure water in case of cooler tube leakage the secondary DM cooling water is in turn cooled by Clarified water taken from clarified water header.
  25. 25. ROTOR COOLING SYSTEM – The rotor is cooled by means of gap pickup cooling, where in the hydrogen gas in the air gap is sucked through the scoops on the rotor and is directed to flow along the ventilating canals milled on the sides of the rotor coil, to the bottom of slot where it takes a turn and comes out on the similar canal milled on the other side of the rotor coil to the hot zone of the rotor, Due to the rotation of the rotor, a positive section as well as discharge is created due to which a certain quantity of a gas flow and cools the rotor. The method of cooling gives uniform distribution of temperature. Also this method has an inherent of eliminating the deformation of copper due to varying temperature. HYDROGEN COOLING SYSTEM – Hydrogen is used as a cooling medium in large capacity generally in views of high heat carrying capacity and low density. But in views sits forming an explosive mixture with oxygen. Proper arrangement for puring, maintaining the purity in the generator have to be made. Also in order to prevent used hydrogen from generators, casing, sealing system is used to provide oil sealing. The system is capable of performing following system – 1. Filing in and purging of hydrogen safety without bringing in contact with air. 2. Maintaining the gas pressure inside the machine at the desired value at all the times. 3. Provide indication to the operator about the condition of the gas inside the machine i.e. the pressure, temperature and purity. 4. Continuous circulation of gas inside the machine through a drier in order to remove any water vapor that may be present in it 5. Indication of liquid level in the generator and alarm in case of high level.
  26. 26. 6. GENERATOR SEALING SYSTEM – Seals are employed to prevent the leakage pf hydrogen from the stator at the point of rotor exit. A continuous film between a rotor collar and the seal liner is maintained by measurement of the oil at pressure above the casing hydrogen gas pressure . EXCITATION SYSTEM EXCITER: The basic use of given exciter system is to produce necessary DC for turbo generator system. Principal behind this that PMG is mounted on the common shaft which generate electricity and that id fed too yoke of main exciter
  27. 27. This exciter generates electricity and this is of AC in nature. This AC is that converted into DC and is that fed to turbo generator via C/C volt for rectifying purpose. We have for RC bock and diode circuit. The most beautiful feature is of this type of exciter is that is automatically divides the magnitude of current to be circulated in rotor circuit. This happens with the help of AVR regulator which means automatic voltage regulator. A feedback path is given to this system which compares theoretical value to predetermine and then it sends the current to rotor as per requirement. The brushless exciter mainly consists of:- 1. rectifier wheels 2. three phase main exciter 3. three phase pilot exciter 4. Metering and supervisory equipment. The brushes exciter is an AC exciter with rotating armature and stationery field. The armature is connected to rotating rectifier brides for rectifying AC voltage induced to armature to DC voltage. The pilot exciter is a PMG (permanent magnet generator). The PMG is also an AC machine with stationery armature and rotating field. When the generator rotates at the rated speed, the PMG generates 220 V at 50 hertz to provide power supply to automatic voltage regulator. A common shaft carries the rectifier wheels the rotor of main exciter and the permanent magnet rotor of pilot exciter. The shaft is rigidly coupled to generator rotor and exciter rotors are than supported on these bearings.
  28. 28. TESTING TESTINGS – 1. This procedure is for high voltage test on stator winding of turbo generator. SCOPE – This procedure covers the high voltage test on stator winding. PURPOSE – This test is conducted to check whether the insulation is properly plced or not. The insulation placed over the winding should be such that they make half overlap with next wrapping of the tape. This test is exclusively conducted to test the health lines of insulation of winding 2. Test procedure for high voltage on rotor winding of TG. SCOPE – This produces the high voltage test on rotor winding PURPOSE – This test is conducted to check whether the insulation is properly placed or not. 3 This procedure for measurement of DC resistance of stator and rotor winding of TG. SCOPE – This procedure covers the measurement of DC resistance of stator winding.
  29. 29. PURPOSE – This test is connected to measure the resistance content present in the conducting material of stator and rotor. 3 Test procedure for measurement of impedance of rotor winding with 50 hertz supply SCOPE – This procedure covers the measurement of impedance of rotor winding 50 hertz source. TEST EQUIPMENTS – 1. 50 hertz power frequency AC source 2. AC voltmeter (0-30, 75, 150) 3. AC ammeter (0-5 ampere) 4. Multimeter 5. Current transformer (50/5 A) 6. Connecting leads CALCULATIONS – Z = V/I ohm Z = Impedance in ohm V = Voltage in volts I = Current in ampere
  30. 30. With 50 hertz, this test id done in following condition – 1. Rotor outside the stator at standstill. 2. Rotor inside the stator at standstill. 3. Rotor inside the stator at speed 1/3, 2/3, 3/3 of rated speed. ACCEPTANCE LIMIT- IMPEDENCE WITH 50 HERTZ - As the impedance of the rotor winding depends on physical geometry of the rotor, it is not possible to fix at particular value for acceptance, but a peculiar characteristics that impedance increases with increase of voltage can be assured value of increase is less in cylindrical rotor that in salient pole rotors 5 .Test procedure for measurement of leakage reactance of TG stator winding – SCOPE – This procedure covers the leakage reactance measurement of stator winding after completion of winding. PURPOSE –
  31. 31. 1. To determine total leakage reactance Xl. 2. To determine core leakage reactance Xc. 3. To compute potier reactance Xd. 6. Test procedure for capacitance measurement of stator winding. SCOPE – The procedure covers the measurement of capacitance per phase with respect to ground of the stator winding. PURPOSE – To generate reference value for comparison in future at site. PRINCIPLE – The stator winding have two values of capacitances. 1. Cg – capacitance with respect to ground called ground capacitance. 2. Cm – capacitance with respect to other winding called mutual capacitance.
  32. 32. HELIUM LEAK TEST – PURPOSE – To check any leakage of gas from stator and rotor as if there is any leakage of gas used for cooling such as hydrogen then it may cause an explosion. MOTOR WINDING Technical Requirements 1. Count the coil groups in the anti clock wise direction locking from the connection end. 2. Leads of the coils groups lying on the outer periphery of the overhang position shall be the finish and those lying on the inner periphery shall be the start to coil groups. 3. Leads shall be taken form the coil side lying at inner periphery of slot No.1. 4. The coil group No.1 shall Lie at top with its axes coinciding with the vertical axis of the frame. 5. Take out terminal leads 02 U2, V2, W2 for left hand side terminal box and 02 U1, V1, W1 for right hand side terminal box. When looking form the connection end.
  33. 33. Circuit diagram: WINDING DIAGRAM OF MOTOR Winding data : NO. OF PHASE 3 NO. OF POLES 6 PHASE CONNECTION Y
  34. 34. Connection of motor winding : NO. OF PARELLEL PATH 2 NO. OF COIL GROUP 18
  35. 35. CONCLUSION Training at B.H.E.L. has proved to be quite faithful. It proved an opportunity for encounter with such huge machine like turbo-generators. The architecture of B.H.E.L., the way various units are linked and the way working of whole plant is controlled make the students realize that Engineering is not just structural description but greater part is planning and management. It provides an opportunity to learn tech. Used at proper place and time can save a lot of labour. But there are few factors that require special mention. Training is not carried in true spirit. It is recommended that there should be projectors especially for trainees where presence of authorities is ensured. However, training has proved to be satisfactory. It has allowed us an opportunity to get an exposure of the practical implementation of theoretical fundamentals.

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