A transformer transfers power between two circuits through electromagnetic induction. It operates on the principle of mutual induction between two coils linked by a magnetic core. The induced EMF in the secondary winding is proportional to the flux density in the core, the core's cross-sectional area, frequency, and number of turns in the winding. A transformer consists of two coils wound around a laminated iron core, which allows alternating current in the primary winding to induce a varying magnetic field and thereby an alternating voltage in the secondary winding. Heat generated in the transformer is dissipated to the surrounding air through the insulating oil that circulates through the transformer and radiator fins.
Disadvantages of corona, radio interference, inductive interference between p...vishalgohel12195
Disadvantages of corona, radio interference, inductive interference between power and communication lines
Introduction
Disadvantages of corona.
Radio interference.
Inductive interference between power and communication lines
This document provides an overview of the EE2402 Protection & Switchgear course presented by C.Gokul. It includes the course syllabus, units covered, textbook references and introductory content on power system basics, components, faults, protection elements, relay terminology and essential qualities of protection systems. The key topics discussed are types of faults in power systems, importance of protective schemes, elements of a protection system including current transformers, voltage transformers, relays and circuit breakers. Neutral earthing methods with a focus on Peterson coil are also introduced.
Functions and Performance Requirements
Elements of an Excitation System
Types of Excitation Systems
Control and Protection Functions
Modeling of Excitation Systems
The functions of an excitation system are
to provide direct current to the synchronous generator field winding, and
to perform control and protective functions essential to the satisfactory operation of the power system
The performance requirements of the excitation system are determined by
Generator considerations:
supply and adjust field current as the generator output varies within its continuous capability
respond to transient disturbances with field forcing consistent with the generator short term capabilities:
rotor insulation failure due to high field voltage
rotor heating due to high field current
stator heating due to high VAR loading
heating due to excess flux (volts/Hz)
Power system considerations:
contribute to effective control of system voltage and improvement of system stability
The document discusses protection schemes for transformers. It describes faults that can occur in transformers such as open circuits, overheating, and winding short circuits. It then discusses different protection systems for transformers including Buchholz relays, earth fault relays, overcurrent relays, and differential protection systems. Differential protection systems operate by comparing currents from current transformers on both sides of the transformer and tripping the circuit breaker if a difference is detected, indicating an internal fault. The combination of protection schemes provides comprehensive protection for transformers.
Infinite bus bar is one which keeps constant voltage and frequency although the load varies. Thus it may behave like a voltage source with zero internal impedance and infinite rotational inertia.
This document summarizes different types of excitation systems for alternators. It discusses the function of excitation systems to supply direct current to the field winding and control the voltage and reactive power of alternators. The three main types covered are DC excitation systems, AC excitation systems, and static excitation systems. DC excitation systems use two small DC generators as exciters but are not commonly used for large alternators now. AC excitation systems include brushless and rotating thyristor types and have advantages like eliminating brushes. Static excitation systems have no rotating parts, are suitable for medium and high capacity alternators, and have benefits like smaller size and no windage losses. The document concludes that the selection of an excitation system depends on factors like the altern
Disadvantages of corona, radio interference, inductive interference between p...vishalgohel12195
Disadvantages of corona, radio interference, inductive interference between power and communication lines
Introduction
Disadvantages of corona.
Radio interference.
Inductive interference between power and communication lines
This document provides an overview of the EE2402 Protection & Switchgear course presented by C.Gokul. It includes the course syllabus, units covered, textbook references and introductory content on power system basics, components, faults, protection elements, relay terminology and essential qualities of protection systems. The key topics discussed are types of faults in power systems, importance of protective schemes, elements of a protection system including current transformers, voltage transformers, relays and circuit breakers. Neutral earthing methods with a focus on Peterson coil are also introduced.
Functions and Performance Requirements
Elements of an Excitation System
Types of Excitation Systems
Control and Protection Functions
Modeling of Excitation Systems
The functions of an excitation system are
to provide direct current to the synchronous generator field winding, and
to perform control and protective functions essential to the satisfactory operation of the power system
The performance requirements of the excitation system are determined by
Generator considerations:
supply and adjust field current as the generator output varies within its continuous capability
respond to transient disturbances with field forcing consistent with the generator short term capabilities:
rotor insulation failure due to high field voltage
rotor heating due to high field current
stator heating due to high VAR loading
heating due to excess flux (volts/Hz)
Power system considerations:
contribute to effective control of system voltage and improvement of system stability
The document discusses protection schemes for transformers. It describes faults that can occur in transformers such as open circuits, overheating, and winding short circuits. It then discusses different protection systems for transformers including Buchholz relays, earth fault relays, overcurrent relays, and differential protection systems. Differential protection systems operate by comparing currents from current transformers on both sides of the transformer and tripping the circuit breaker if a difference is detected, indicating an internal fault. The combination of protection schemes provides comprehensive protection for transformers.
Infinite bus bar is one which keeps constant voltage and frequency although the load varies. Thus it may behave like a voltage source with zero internal impedance and infinite rotational inertia.
This document summarizes different types of excitation systems for alternators. It discusses the function of excitation systems to supply direct current to the field winding and control the voltage and reactive power of alternators. The three main types covered are DC excitation systems, AC excitation systems, and static excitation systems. DC excitation systems use two small DC generators as exciters but are not commonly used for large alternators now. AC excitation systems include brushless and rotating thyristor types and have advantages like eliminating brushes. Static excitation systems have no rotating parts, are suitable for medium and high capacity alternators, and have benefits like smaller size and no windage losses. The document concludes that the selection of an excitation system depends on factors like the altern
Unit I: Introduction to Protection System:
Introduction to protection system and its elements, functions of protective relaying, protective zones, primary and backup protection, desirable qualities of protective relaying, basic terminology.
Relays:
Electromagnetic, attracted and induction type relays, thermal relay, gas actuated relay, design considerations of electromagnetic relay.
Unit-II: Relay Application and Characteristics:
Amplitude and phase comparators, over current relays, directional relays, distance relays, differential relay.
Static Relays: Comparison with electromagnetic relay, classification and their description, over current relays, directional relay, distance relays, differential relay.
Unit-III Protection of Transmission Line:
Over current protection, distance protection, pilot wire protection, carrier current protection, protection of bus, auto re-closing,
Unit-IV: Circuit Breaking:
Properties of arc, arc extinction theories, re-striking voltage transient, current chopping, resistance switching, capacitive current interruption, short line interruption, circuit breaker ratings.
Testing Of Circuit Breaker: Classification, testing station and equipments, testing procedure, direct and indirect testing.
Unit-V Apparatus Protection:
Protection of Transformer, generator and motor.
Circuit Breaker: Operating modes, selection of circuit breakers, constructional features and operation of Bulk Oil, Minimum Oil, Air Blast, SF6, Vacuum and d. c. circuit breakers.
Transmission lines require protective schemes due to their long lengths and exposure to the open atmosphere, making faults more common. The key methods for protecting transmission lines are:
1. Unit and non-unit type protections, with the main types being differential, overcurrent, distance, and carrier current protections.
2. Distance relays operate based on the impedance seen from the relay location, tripping if the impedance indicates a fault within the reach of the relay. Directional distance relays can discriminate between faults in different directions.
3. A three-step distance protection scheme uses underreach, definite reach, and overreach zones to isolate faults along the transmission line while coordinating protection across multiple line sections
This document discusses different types of distance relays used for transmission line protection. It describes impedance, reactance, and admittance relays. An impedance relay operates based on the ratio of voltage to current, with a torque proportional to current and restraining torque proportional to voltage. During a fault, the impedance ratio decreases and trips the circuit breaker if it falls below a predetermined value.
The 220kV power substation in Muradnagar has a capacity of 2*160MVA and 1*100MVA. It receives power from three 220kV transmission lines and two 400kV lines, which it steps down to lower voltages of 132kV, 66kV, 33kV and 11kV. The substation contains various equipment like circuit breakers, isolators, transformers, lightning arrestors, current and potential transformers, and wave traps to distribute, monitor and protect the flow of electricity. It utilizes equipment like oil and air-blast circuit breakers, vacuum and SF6 gas circuit breakers, and oil and air-cooled power transformers in its operations.
Training report-in-a-132-k-v-substationankesh kumar
This document provides a training report for a summer internship at the Uttar Pradesh Power Corporation Limited 132/33 kV substation in Chandauli, Barabanki, India.
The report includes an introduction to the Uttar Pradesh Power Corporation and the purpose of the internship. It also provides a preface describing the learning experience and thanks to those involved.
The report then gives an acknowledgement and thanks to those who guided the internship. It provides a rough description of the Chandauli, Barabanki substation including incoming and outgoing voltages and feeders. It also includes definitions and descriptions of substations and the equipment within them.
The document discusses DC machines and motors. It provides explanations of Maxwell's corkscrew rule and Fleming's left-hand and right-hand rules for determining the direction of magnetic fields. It also describes the construction and working principles of DC generators and motors, including their components like the armature, commutator, and field windings. Various types of DC machines are classified based on their excitation and winding configurations. The document also covers topics like armature reaction, speed control methods, and applications of different DC motor types.
This document discusses voltage and reactive power control methods in power systems. It covers the need for reactive power to maintain voltage levels and deliver active power through transmission lines. Various reactive power compensation devices are described such as series and shunt capacitors/reactors, synchronous condensers, static VAR compensators, and static synchronous compensators. Common voltage and reactive power control methods include excitation control at generating stations, using tap changing transformers, and switching shunt reactors/capacitors depending on load levels.
This document provides information about the construction, components, testing, operation, protection and maintenance of a 132kV switchyard. It includes details about the bus bars, circuit breakers, current transformers, potential transformers, wave traps, isolators, control and protection schemes. The key components of the switchyard are described along with their ratings and testing procedures. The operational modes and protection philosophy are also summarized.
HIGH VOL TAGE TESTING OF TRANSFORMER BY HARI SHANKAR SINGHShankar Singh
1. The document discusses high voltage testing of electrical transformers, including various types of tests like partial discharge testing, impulse testing, turns ratio testing, and insulation resistance testing.
2. These tests help check the insulation quality, detect defects, verify voltage ratios, and ensure transformers can withstand high voltage surges to prevent failures.
3. High voltage testing provides advantages like improved safety, energy efficiency, lower costs, and failure detection; but can also have disadvantages like not removing the root causes of failures.
This document provides information about textbooks and reference books related to switchgear and protection. It also outlines the syllabus which covers topics like circuit breakers, relays, and protection of generators, transformers, feeders and busbars. The document discusses that switchgear are used to control, regulate and switch electrical circuits and includes devices like circuit breakers, isolators, switches, relays and fuses. It explains that circuit breakers are used instead of fuses and switches for high voltage applications to avoid disadvantages like inability to perform frequent operations and ensure continuity of service.
The document is a seminar report on switchyard equipment and protection systems at NTPC-SAIL Power Company Private Limited in Rourkela, India. It provides an overview of the captive power plant, including its major equipment like generators, transformers, and switchyard components. The switchyard contains 20 operating bays including generators, grid feeders, smelter feeders, and transformers. Important switchyard components discussed include busbars, bus couplers, insulators, circuit breakers, isolators, current and voltage transformers, and lightning arresters.
Static relays use electronic components like semiconductors instead of mechanical parts to detect faults and operate. They have components like rectifiers to convert AC to DC, level detectors to compare values to thresholds, and amplifiers and output devices to trigger trips. The document discusses the components, types, and applications of various static relays like overcurrent, directional, differential, distance and instantaneous relays used in power system protection.
APEPDCL is the electricity distribution company that serves five districts in Andhra Pradesh, with its headquarters in Visakhapatnam. It distributes power at 33kV and 11kV levels. The document discusses the types of substations based on their nature, service, operating voltage, and design. It specifically describes the 33/11kV substation in Jaggampeta, which receives power at 33kV from two sources and distributes it at 11kV to industrial, agricultural and domestic customers in the area. Key equipment in the substation include lightning arresters, capacitive voltage transformers, and current transformers.
The document discusses one-line diagrams, which are simplified diagrams used in power systems to represent the essential components in a simplified graphical format. A one-line diagram shows the main components of a power system like generators, transmission lines, transformers, and loads using standardized symbols. It represents the paths of power flow through the system from generation to transmission to distribution. The diagram is structured to match the physical layout. Impedance and reactance diagrams are similar but represent electrical elements like generators and lines as impedance/reactance values instead of physical components. An example calculation of voltage drop in a transmission line is provided.
This document provides a training report on a 33/11 KV substation in Lucknow, India. It discusses various components of the substation including transformers, bus bars, insulators, circuit breakers, metering equipment, protection systems, and earthing methodology. The report provides specifications for components, describes the types and functions of substation equipment, and outlines the trainee's experiences during their training at the facility.
This document discusses out-of-step (OOS) protection fundamentals. It explains that power swings can cause undesired relay operation and lead to cascading outages. It discusses relay elements prone to operate during power swings like distance and overcurrent relays. It describes stable and unstable power swings and the need for OOS protection to separate asynchronous areas. The document outlines various OOS protection functions like power swing blocking and out-of-step tripping and discusses their benefits. It analyzes relay and generator performance during OOS conditions using system examples. Finally, it recommends protection system and other grid improvements to preserve stability.
This document is a final year project presentation on Static VAR Compensator (SVC). It discusses Flexible AC Transmission Systems (FACTS) which use power electronics to control power flow and increase transmission capacity. SVCs in particular provide fast reactive power support to control voltage and improve stability. Different types of SVC are described including series and shunt compensators using thyristor controlled capacitors and reactors. Mechanically Switched Capacitors are also discussed as a type of shunt compensator. The project layout and applications of SVC systems for transmission systems are outlined.
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This document provides an overview and layout of the 220kV switchyard for the 750MW Ca Mau 1 combined cycle power plant in Vietnam. It includes details on the double busbar system configuration with circuit breakers, disconnecting switches, transformers, surge arresters, control building, DC power system, switchboards, and computerized control and protection panels.
This document provides an overview of power transformers, including:
1. It describes different types of transformers such as power, distribution, auto, step-up, step-down transformers and discusses their various components and specifications.
2. It explains transformers used in power plants along with their ratings, cooling methods, impedance and other details.
3. It covers transformer components, testing procedures, loading capacity, condition monitoring techniques and diagnostic tests to evaluate transformer performance and health.
This document provides a guide for designing a simple transformer with step-by-step calculations. It outlines determining the load power and primary/secondary currents based on the voltage. Wire gauges are selected based on current capacities. The core size is calculated based on the power. Finally, the number of turns for the primary and secondary windings are calculated based on the core size and voltages. Key materials include copper wire, silicon-iron sheets, and insulation to prevent short circuits between windings.
Unit I: Introduction to Protection System:
Introduction to protection system and its elements, functions of protective relaying, protective zones, primary and backup protection, desirable qualities of protective relaying, basic terminology.
Relays:
Electromagnetic, attracted and induction type relays, thermal relay, gas actuated relay, design considerations of electromagnetic relay.
Unit-II: Relay Application and Characteristics:
Amplitude and phase comparators, over current relays, directional relays, distance relays, differential relay.
Static Relays: Comparison with electromagnetic relay, classification and their description, over current relays, directional relay, distance relays, differential relay.
Unit-III Protection of Transmission Line:
Over current protection, distance protection, pilot wire protection, carrier current protection, protection of bus, auto re-closing,
Unit-IV: Circuit Breaking:
Properties of arc, arc extinction theories, re-striking voltage transient, current chopping, resistance switching, capacitive current interruption, short line interruption, circuit breaker ratings.
Testing Of Circuit Breaker: Classification, testing station and equipments, testing procedure, direct and indirect testing.
Unit-V Apparatus Protection:
Protection of Transformer, generator and motor.
Circuit Breaker: Operating modes, selection of circuit breakers, constructional features and operation of Bulk Oil, Minimum Oil, Air Blast, SF6, Vacuum and d. c. circuit breakers.
Transmission lines require protective schemes due to their long lengths and exposure to the open atmosphere, making faults more common. The key methods for protecting transmission lines are:
1. Unit and non-unit type protections, with the main types being differential, overcurrent, distance, and carrier current protections.
2. Distance relays operate based on the impedance seen from the relay location, tripping if the impedance indicates a fault within the reach of the relay. Directional distance relays can discriminate between faults in different directions.
3. A three-step distance protection scheme uses underreach, definite reach, and overreach zones to isolate faults along the transmission line while coordinating protection across multiple line sections
This document discusses different types of distance relays used for transmission line protection. It describes impedance, reactance, and admittance relays. An impedance relay operates based on the ratio of voltage to current, with a torque proportional to current and restraining torque proportional to voltage. During a fault, the impedance ratio decreases and trips the circuit breaker if it falls below a predetermined value.
The 220kV power substation in Muradnagar has a capacity of 2*160MVA and 1*100MVA. It receives power from three 220kV transmission lines and two 400kV lines, which it steps down to lower voltages of 132kV, 66kV, 33kV and 11kV. The substation contains various equipment like circuit breakers, isolators, transformers, lightning arrestors, current and potential transformers, and wave traps to distribute, monitor and protect the flow of electricity. It utilizes equipment like oil and air-blast circuit breakers, vacuum and SF6 gas circuit breakers, and oil and air-cooled power transformers in its operations.
Training report-in-a-132-k-v-substationankesh kumar
This document provides a training report for a summer internship at the Uttar Pradesh Power Corporation Limited 132/33 kV substation in Chandauli, Barabanki, India.
The report includes an introduction to the Uttar Pradesh Power Corporation and the purpose of the internship. It also provides a preface describing the learning experience and thanks to those involved.
The report then gives an acknowledgement and thanks to those who guided the internship. It provides a rough description of the Chandauli, Barabanki substation including incoming and outgoing voltages and feeders. It also includes definitions and descriptions of substations and the equipment within them.
The document discusses DC machines and motors. It provides explanations of Maxwell's corkscrew rule and Fleming's left-hand and right-hand rules for determining the direction of magnetic fields. It also describes the construction and working principles of DC generators and motors, including their components like the armature, commutator, and field windings. Various types of DC machines are classified based on their excitation and winding configurations. The document also covers topics like armature reaction, speed control methods, and applications of different DC motor types.
This document discusses voltage and reactive power control methods in power systems. It covers the need for reactive power to maintain voltage levels and deliver active power through transmission lines. Various reactive power compensation devices are described such as series and shunt capacitors/reactors, synchronous condensers, static VAR compensators, and static synchronous compensators. Common voltage and reactive power control methods include excitation control at generating stations, using tap changing transformers, and switching shunt reactors/capacitors depending on load levels.
This document provides information about the construction, components, testing, operation, protection and maintenance of a 132kV switchyard. It includes details about the bus bars, circuit breakers, current transformers, potential transformers, wave traps, isolators, control and protection schemes. The key components of the switchyard are described along with their ratings and testing procedures. The operational modes and protection philosophy are also summarized.
HIGH VOL TAGE TESTING OF TRANSFORMER BY HARI SHANKAR SINGHShankar Singh
1. The document discusses high voltage testing of electrical transformers, including various types of tests like partial discharge testing, impulse testing, turns ratio testing, and insulation resistance testing.
2. These tests help check the insulation quality, detect defects, verify voltage ratios, and ensure transformers can withstand high voltage surges to prevent failures.
3. High voltage testing provides advantages like improved safety, energy efficiency, lower costs, and failure detection; but can also have disadvantages like not removing the root causes of failures.
This document provides information about textbooks and reference books related to switchgear and protection. It also outlines the syllabus which covers topics like circuit breakers, relays, and protection of generators, transformers, feeders and busbars. The document discusses that switchgear are used to control, regulate and switch electrical circuits and includes devices like circuit breakers, isolators, switches, relays and fuses. It explains that circuit breakers are used instead of fuses and switches for high voltage applications to avoid disadvantages like inability to perform frequent operations and ensure continuity of service.
The document is a seminar report on switchyard equipment and protection systems at NTPC-SAIL Power Company Private Limited in Rourkela, India. It provides an overview of the captive power plant, including its major equipment like generators, transformers, and switchyard components. The switchyard contains 20 operating bays including generators, grid feeders, smelter feeders, and transformers. Important switchyard components discussed include busbars, bus couplers, insulators, circuit breakers, isolators, current and voltage transformers, and lightning arresters.
Static relays use electronic components like semiconductors instead of mechanical parts to detect faults and operate. They have components like rectifiers to convert AC to DC, level detectors to compare values to thresholds, and amplifiers and output devices to trigger trips. The document discusses the components, types, and applications of various static relays like overcurrent, directional, differential, distance and instantaneous relays used in power system protection.
APEPDCL is the electricity distribution company that serves five districts in Andhra Pradesh, with its headquarters in Visakhapatnam. It distributes power at 33kV and 11kV levels. The document discusses the types of substations based on their nature, service, operating voltage, and design. It specifically describes the 33/11kV substation in Jaggampeta, which receives power at 33kV from two sources and distributes it at 11kV to industrial, agricultural and domestic customers in the area. Key equipment in the substation include lightning arresters, capacitive voltage transformers, and current transformers.
The document discusses one-line diagrams, which are simplified diagrams used in power systems to represent the essential components in a simplified graphical format. A one-line diagram shows the main components of a power system like generators, transmission lines, transformers, and loads using standardized symbols. It represents the paths of power flow through the system from generation to transmission to distribution. The diagram is structured to match the physical layout. Impedance and reactance diagrams are similar but represent electrical elements like generators and lines as impedance/reactance values instead of physical components. An example calculation of voltage drop in a transmission line is provided.
This document provides a training report on a 33/11 KV substation in Lucknow, India. It discusses various components of the substation including transformers, bus bars, insulators, circuit breakers, metering equipment, protection systems, and earthing methodology. The report provides specifications for components, describes the types and functions of substation equipment, and outlines the trainee's experiences during their training at the facility.
This document discusses out-of-step (OOS) protection fundamentals. It explains that power swings can cause undesired relay operation and lead to cascading outages. It discusses relay elements prone to operate during power swings like distance and overcurrent relays. It describes stable and unstable power swings and the need for OOS protection to separate asynchronous areas. The document outlines various OOS protection functions like power swing blocking and out-of-step tripping and discusses their benefits. It analyzes relay and generator performance during OOS conditions using system examples. Finally, it recommends protection system and other grid improvements to preserve stability.
This document is a final year project presentation on Static VAR Compensator (SVC). It discusses Flexible AC Transmission Systems (FACTS) which use power electronics to control power flow and increase transmission capacity. SVCs in particular provide fast reactive power support to control voltage and improve stability. Different types of SVC are described including series and shunt compensators using thyristor controlled capacitors and reactors. Mechanically Switched Capacitors are also discussed as a type of shunt compensator. The project layout and applications of SVC systems for transmission systems are outlined.
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This document provides an overview and layout of the 220kV switchyard for the 750MW Ca Mau 1 combined cycle power plant in Vietnam. It includes details on the double busbar system configuration with circuit breakers, disconnecting switches, transformers, surge arresters, control building, DC power system, switchboards, and computerized control and protection panels.
This document provides an overview of power transformers, including:
1. It describes different types of transformers such as power, distribution, auto, step-up, step-down transformers and discusses their various components and specifications.
2. It explains transformers used in power plants along with their ratings, cooling methods, impedance and other details.
3. It covers transformer components, testing procedures, loading capacity, condition monitoring techniques and diagnostic tests to evaluate transformer performance and health.
This document provides a guide for designing a simple transformer with step-by-step calculations. It outlines determining the load power and primary/secondary currents based on the voltage. Wire gauges are selected based on current capacities. The core size is calculated based on the power. Finally, the number of turns for the primary and secondary windings are calculated based on the core size and voltages. Key materials include copper wire, silicon-iron sheets, and insulation to prevent short circuits between windings.
Summer traning on Power Transformer ConstructionStudent
The document summarizes an industrial training seminar on transformer construction held at BHEL Bhopal from May 29th to June 25th, 2014. It was presented by Mandeep Singh, an electrical engineering final year student from B.I.E.T Jhansi, under the guidance of Shri Shailendra Kumar Somi from BHEL Bhopal. The seminar covered topics such as transformer core building, winding, coil assembly, power assembly, case fitting, insulation, testing, and dispatch. It provided details on the manufacturing process and testing standards for power transformers.
This document summarizes a student project on assessing the life of transformers. It describes the objectives of understanding transformers in detail and studying tests to assess transformer health. It then provides details on different transformer types and components like bushings and accessories. The document outlines transformer design considerations and tests conducted at different stages like preliminary, commissioning and special tests. It discusses techniques like dissolved gas analysis and furan analysis used to monitor transformer condition and residual life.
Transformer oil which is obtained by fractional distillation of crude oil serves many purposes in a transformer insulation.This report includes the classifications of transformer oil under composition and additives and it also includes the different types contamination that can occur in a transformer.These contamination issues can be tracked by an analysis of transformer oil.This report is consist of different transformer oil testing and also my personal experience in observing few tests at the laboratory of Asset Management Hydro Electrical - CEB.
This document contains design calculations for a single-phase distribution transformer. It specifies design parameters such as a rated output of 50 kVA, primary voltage of 13800V, secondary voltage of 460/230V, and an efficiency of at least 0.96 at full load. The document then shows calculations for transformer components like winding dimensions and currents, core size, flux density, losses, and temperature rise. Design goals are to have losses lower than specified guarantees and a temperature rise under 55°C at full load.
The document provides information on transformer design specifications and considerations. It discusses technical specifications for a 500KVA, 3 phase transformer including input/output voltages and power ratings. It also covers initial calculations, losses in transformers, core materials and construction, winding design, insulation, cooling methods, and connection configurations. The goal is to design a transformer that efficiently transfers power while meeting specifications for voltage, current, temperature rise and other factors.
The document is a seminar report on gas insulated transformers presented by Chandan Kumar Sinha at the National Institute of Technology. It discusses how gas insulated transformers use SF6 gas instead of oil as both an insulating and cooling agent. It provides an overview of SF6 gas properties, the applications and features of gas insulated transformers, and compares them to oil insulated transformers. The report concludes that ongoing research and developments have made larger capacity gas insulated transformers possible and SF6 is an eco-friendly insulating gas that can increase transformer efficiency and reliability.
A transformer transfers electrical energy from one circuit to another through electromagnetic induction. It works by using two coils - a primary winding that receives energy from an alternating current source, and a secondary winding that delivers energy to a load. As the magnetic field in the primary coil fluctuates, it induces an alternating voltage in the secondary coil. This allows the transformer to increase or decrease voltage levels while keeping frequency constant. Common transformer types include power transformers used in electrical equipment and autotransformers with a single winding and movable tap to select different output voltages.
This document summarizes the summer training report submitted by four students from Amritsar College of Engineering & Technology at the Punjab State Power Corporation Limited Transformer Repair Workshop in Amritsar. The workshop repairs damaged transformers to save costs compared to the private sector. It has two main circles and aims to repair 120 units per month. The report describes the workshop organization and sections for washing, repairing, drying, assembling, testing and storing transformers. It also explains transformer components, types, workings, efficiency tests and applications.
The document provides an overview of transformers, including their operating principle, classifications, construction, parts, losses, efficiency, parallel operation, maintenance, testing, protection, 3-phase connections, and frequently asked questions. Transformers operate on the principle of mutual induction to convert AC electric energy at one voltage level to another voltage level at the same frequency. They consist of coils wrapped around a common ferromagnetic core to provide a path for the magnetic field.
This document provides an overview of transformers, including:
- The basic components and construction of transformers, including windings, cores, insulation, cooling systems, and accessories.
- The main types of transformers such as power transformers and distribution transformers.
- How transformers work using electromagnetic induction to transform voltages.
- How transformers are classified based on factors like power level, frequency, voltage class, cooling type, and purpose.
- Key components like cores, insulation, bushings, Buchholz relays, and tap changers.
A transformer is a static device that changes alternating current (AC) electrical power at one voltage level to another voltage level through magnetic induction. It does this without changing the frequency, and can either step up or step down the voltage. Transformers work based on mutual inductance between two inductively coupled coils. Transformers can be classified based on their core type, cooling system, number of phases, and whether they are ideal or practical. The main types are core type, shell type, air cooled, oil cooled, single phase, and three phase transformers.
The document discusses distribution transformers, including their testing, maintenance, and protection. It provides details on routine tests, type tests, and special tests performed on transformers according to standards. These tests check various parameters like winding resistance, insulation levels, voltage ratios, losses, and short circuit withstand ability. The document also outlines maintenance procedures like regular oil testing, insulation resistance checks, bushing cleaning, and temperature monitoring. Proper preventive maintenance is emphasized to prevent failures caused by issues like low oil levels, water ingress, overloading, and poor design/workmanship.
Presentation Design of Computer aided design of power transformerSMDDTech
The document summarizes the design of a 100 KVA power transformer. It includes the design calculations for the high voltage and low voltage windings, core, tank, and other components. Key specifications calculated include 11,000/433V voltage ratings, 3344 turns for the high voltage winding, 76 turns for the low voltage winding, and a core size of 115mm diameter. Performance metrics like 98.15% efficiency at full load, 3.94% voltage regulation, and total losses of 1561.617W are provided. Dimensions for the transformer tank and cooling system are also listed.
The document provides information about the components and functions of a substation, including transformers, circuit breakers, and relays. It describes three types of circuit breakers used in the Sealdah Power House substation: air circuit breakers, which use high-pressure air to extinguish arcs; vacuum circuit breakers, which take advantage of arc non-sustainability in a vacuum; and oil circuit breakers, which use insulating oil to generate hydrogen gas to extinguish arcs. Specifications are provided for samples of equipment from the Sealdah Power House, including transformers, air circuit breakers, and vacuum circuit breakers.
Power transformers are static devices used to transmit electrical power between circuits without changing frequency. They operate using electromagnetic induction and are used to step up or down transmission voltages. Power transformers have ratings between 33-400 kV and above 200 MVA. They are essential for minimizing energy losses during long distance power transmission by increasing voltage for transmission then decreasing it for distribution. Power transformers work by inducing an emf in the secondary winding through a fluctuating magnetic field produced in the primary winding according to Faraday's law of induction. The number of turns in each winding determines whether the transformer steps up or down the voltage. Key components include the core, windings, insulating materials, tap changers, bushings, tank, conservator, breather
Operation and maintenance of distribution transformers is important to prevent failures and repairs. Key aspects include:
- Regularly check oil levels, insulation resistance, and test oil samples for breakdown voltage and acidity.
- Maintain clean bushings, tight connections, and functional protection devices like fuses and lightning arrestors.
- Common defects include oil leaks, overheating, and ineffective breathers. Causes may be corrosion, worn gaskets, overpressure, or inadequate ventilation/circulation.
- Proper maintenance following schedules can maximize transformer life and minimize failures in the distribution system.
This document summarizes information from a brochure about Synergy Transformers, a manufacturer of distribution, power, and furnace transformers in India. It discusses the company's focus on safety, efficiency, reliability and product performance. It also provides details on their product lines, applications, specifications, and contact information.
Relays sense abnormal voltage and current conditions and send signals to circuit breakers to isolate faulty parts of a power system. Electromagnetic induction relays use eddy currents produced in a disc to generate torque. There are different types of overcurrent and directional relays. Distance relays use impedance, reactance, or mho principles. Transformer and feeder protection uses overcurrent, distance, or pilot wire schemes. Circuit breakers use oil, air, sulfur hexafluoride, or vacuum to extinguish arcs and open faulty circuits. Instrument transformers reduce high voltages and currents to safer, measurable levels for meters and relays.
A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer's core, which induces a varying electromotive force (EMF) across any other coils wound around the same core.
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This document provides an overview of EWT Transformer Sdn Bhd, a Malaysian manufacturer of transformers and compact substations. It discusses the company's history, products, and services offered for transformer life management. EWT was established in 1993 as a joint venture and has grown to over 150 employees. Their product line includes distribution transformers, compact substation units, and earthing/auxiliary transformers. The document outlines common transformer failures and recommends annual maintenance checks and testing to determine condition. EWT provides dedicated maintenance and repair services to help customers manage transformer life.
This document provides an overview of a presentation on a summer training at a 132/33 kV sub-station in Allahabad, India. It discusses key equipment used in sub-stations including transformers, protection devices like Buchholz relays and silica gel breathers, cooling equipment, and other critical infrastructure like circuit breakers, capacitor banks, potential and current transformers, isolators, and insulators. It also describes the functions of this equipment and why they are important components of the power distribution system.
The document discusses transformer insulating oil, which serves as both an electrical insulator and coolant in power transformers. There are two main types of transformer oil - paraffin-based and naphtha-based. The key parameters used to evaluate transformer oil quality include electrical parameters like dielectric strength and resistivity, chemical parameters like water content and acidity, and physical parameters like viscosity and pour point. Maintaining high standards for these parameters helps ensure the oil can safely and effectively insulate and cool the transformer over time.
A transformer consists of two coils, a primary and secondary winding, that are magnetically linked through an iron core. Alternating current passing through the primary winding induces an alternating voltage in the secondary winding through electromagnetic induction. Transformers can step voltage up or down and are classified based on their construction, cooling type, purpose, supply type, and application. Key design considerations for a transformer include its power rating, voltage ratio, vector group, impedance, losses, cooling type, insulation level, and temperature rise. Transformers undergo various tests at the factory and after installation to ensure proper operation.
This document discusses testing of transformers. It provides an overview of transformers and their functions in transmission and distribution of electrical energy. It then describes various routine, type, and special tests performed on transformers, including winding resistance measurement, voltage ratio measurement, no-load loss measurement, load loss measurement, insulation resistance measurement, and dielectric tests. It also discusses short-circuit testing procedures and criteria. Temperature rise testing and its limits are also summarized.
The document discusses substations and their components. It defines a substation as an assembly of apparatus that transforms electrical energy from one form to another, such as changing voltage levels. Substations contain step-up transformers to increase voltage for transmission and step-down transformers to decrease voltage for distribution to consumers. The document describes various types of substations and explains their functions. It also provides details about components within substations such as circuit breakers, transformers, buses, isolators and instrument transformers.
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1. TRANSFORMER
Transformer is a static device used for transferring of
power from one circuit to another without change in
frequency.
Operates on the principle of mutual induction between
two circuits linked by a common magnetic field.
EMF induced in a winding is proportional to the flux
density in the core, cross section of the core, frequency
and no. of turns in the winding.
2. WORKING PRINCIPLE OF A POWER
TRANSFORMER
A Transformer consists of two mutually
inductive coils that are electrically separated but
magnetically linked through a low reluctance
path .
When one coil is connected to a source of
alternating voltage ,an alternating flux is set up
in the laminatrd core ,most of which links with
the second coil wound on the same core ,in which
it induces EMF according to Faraday ‘s laws of
electro magnetic induction
If the second coil is connected to a load , a
current flows through it and thus the electric
energy is transfered completely magnetically
from 1st
coil to 2nd
coil at voltage depending upon
the no.of turns in these coils.
3. TRANSFORMER BASICALLY
CONSISTS OF:
Magnetic Circuit comprising Limbs, yokes, clamping
structures
Electrical circuit comprising primary, secondary
windings
Insulation comprising of transformer oil and solid
insulation viz. paper, pressboard, wood etc. and bracing
devices
Main tank housing all the equipment
Radiators, Conservator tank
On or Off load tap changer
Vent pipe, Buchholz relay, Thermometers
Fans, Cooling pumps connected piping
Terminals i.e. connecting leads from windings to bushing
with supporting arrangements
4.
5. FEATURES OF POWER
TRANSFORMERS
Single Phase
Three phase
Star or Delta connected Primary
Star or Delta connected Secondary
With or without Tertiary winding
Provided with Off-circuit tap switch or
On-load Tap Changer for voltage regulation
7. EMF EQUATION OF A POWER
TRANSFORMER
Induced EMF Primary (rms) =
E1 =4.44 f N1 Bm A
Induced EMF Secondary (rms) =
E2 = 4.44 f N2 Bm A
E1/ N1 =E2 /N2 = 4.44 f Bm A
E2 / E1 = N2 /N1 =K ,Transformation ratio.
if K is more than 1 , it is stepup transformer
if K is less than 1 ,it is step down transformer.
for an ideal tr. Input VA = output VA
V1 I1 = V2 I2.
8. Codes and Standards
• Codes or Regulations are mandatory requirements stipulated to
ensure the safety of the product during testing and service.
• Standards are the basis of agreement and can be used for
limited scope or even restricted. Standards also promote
interchangeability. Standards exist for material, product,
process, testing, calibration etc.
• Specifications are based on mandatory requirements of the
purchaser and agreed requirements of the standard.
9. DESIGN PARAMETERS – FROM USER
POINT
Voltage Ratio No. of phases
Flux density Rated capacity
Current density Insulation& cooling
medium
Insulation levels Tap changer
Vector group Cooling arrangement
Percentage Impedance Oil preservation system
Short circuit withstanding Operating conditions
capacity
10. NORMALLY FLUX DENSITY IS CHOSEN NEAR KNEE POINT OF
MAGNETIZATION CURVE LEAVING SUFFICIENT MARGIN TO TAKE
CARE OF VOLTAGE AND FREQUENCY VARIATIONS. CRGO STEEL
WITH SILICON CONTENT OF APPROX. 3% IS USED FOR
MAGNETIC CIRCUIT.
CHARACTERISTICS OF GOOD CORE ARE
I. MAX. MAGNETIC INDUCTION TO OBTAIN A HIGH INDUCTION
AMPLITUDE IN AN ALTERNATING FIELD.
II. MINIMUM SPECIFIC CORE LOSS AND LOW EXCITATION
CURRENT.
III. LOW MAGNETOSTRICTION FOR LOW NOISE LEVEL.
IV. GOOD MECHANICAL PROCESSING PROPERTIES.
MAGNETOSTRICTION IS CHANGE IN CONFIGURATION OF A
MAGNETIZABLE BODY IN A MAGNETIC FIELD WHICH LEADS TO
PERIODICAL CHANGES IN THE LENGTH OF THE BODY IN AN
ALTERNATING MAGNETIC FIELD. DUE TO MAGNETOSTRICTION
OF LAMINATIONS IN AN ALTERNATING FIELD CORE VIBRATES
GENERATING NOISE IN THE CORE.
11. CURRENT DENSITY IS AN IMPORTANT PARAMETER TO
DESIGN THE SECTION OF
THE CONDUCTOR FOR A SPECIFIED TEMPERATURE
RISE, RATED CAPACITY AND SHORT CIRCUIT
WITHSTAND CAPACITY OF THE TRANSFORMER.
DIFFERENT TYPES OF WINDINGS :
DISTRIBUTED CROSSOVER WINDING
SPIRAL WINDING
HELICAL WINDING
CONTINUOUS DISC WINDING
INTERLEAVED DISC WINDING
SHIELDED LAYER WINDING
12. Transformer oil serves as an electrical insulation and also as a
coolant to dissipate heat developed in the transformer.
CHARACTERISTICS OF TRANSFORMER OIL:
PHYSICAL
Appearance
The oil shall be clear, transparent and free from suspended
matter.
If color of oil is
a) Light - indicates degree of refining
b) Cloudy or foggy - Presence of moisture
c) Greenish tinge - Presence of copper salts
d) Acid smell - Presence of volatile acid. Can cause
corrosion
13. Density
At 27deg. c is 0.89gm/cu.cm. This ensures that water in the
form of ice present in oil remains at the bottom and does not
float up to a temp. of about – 10 deg. c.
Viscosity
Is a measure of oil resistance to continuous flow without the
effect of external forces. Oil must be mobile in transformers to
take away heat. Viscosity shall be as low as possible at low
temperatures.
Flash point
is the temperature at which oil gives so much vapor, which
when mixed with air forms an ignitable mixture and gives a
momentary flash on application of a flame. Minimum flash point
of a good oil shall be 140 deg. C.
14. Pour point
is the temperature at which oil will just flow under prescribed
conditions. If oil becomes too viscous or solidifies it will
hinder the formation of convection currents, thus cooling of
equipment will be affected.
Maximum pour point shall be -9 deg. C
Interfacial Tension
Is the measure of resultant molecular attractive force between
unlike molecules like water and oil at the interface. Presence of
soluble impurities decrease molecular attractive force between
oil and water. This gives an indication of degree of sludging of
oil.
Minimum value 40 dynes/M or 0.04 N/M
.
15. CHEMICAL
Neutralization Number
Is a measure of organic and inorganic acids present
in the oil. Expressed as mg. of KOH required to
neutralize the total acids in one gm. Of oil.
Limits for fresh oil - 0.03 mg KOH/gm - maximum
Limits for used oil - 0.05 mg KOH/gm - maximum
It leads to formation of sludge, metal surface
corrosion and lowering of di-electric strength.
Corrosive Sulphur
It indicates the presence of sulphur, sulphur
compounds, which are corrosive in nature and
corrode the copper surface.
16. Oxidation Stability
This is measured by ageing the oil by simulating actual service
condition of a transformer. Covers the evaluation of acid and
sludge forming tendency of new mineral oils. For used oil,
should be minimum to minimize electrical conduction and
corrosion
Water Content
By moisture entry into oil.
a) By accidental leakage
b) Breathing action
c) During oil filling or topping up
d) By chemical reaction
In unused oil - Maximum 30 ppm
Oil in transformer 145 KV & above - Maximum 15 ppm
Oil in transformer below 145 KV - Maximum 25 ppm
It reduces electrical strength and promotes degradation of oil as
well as paper.
17. ELECTRICAL
Electric Strength
Is the voltage at which arc discharge occurs between two electrodes
when oil is subjected to an electric field under prescribed conditions.
New oil unfiltered - 30 KV minimum (rms)
New oil filtered - 60 KV minimum (rms)
Resistivity
It is numerically equal to the resistance between opposite faces of a
centimeter cube of oil. Insulation resistance of the windings of
transformer is dependant on the resistivity of oil. A low value
indicates the presence of moisture and conducting contaminants.
Values for a new transformer are
(12)
At 27 deg. c 500x 10 ohm.cm
(12)
At 90 deg. c 30x 10 ohm.cm
18. Dielectric Dissipation Factor (Tan Delta & Loss Tangent)
Is measure of dielectric losses in oil & hence the amount of heat
energy dissipated.
It gives an indication as to the quality of insulation. A high
value indicates presence of contaminants or deterioration
products such as water, oxidation products, soluble
varnishes, and resins.
1) Tan delta at 90° for unused oil - maximum 0.2
2) Tan delta at 90° for oil before charging transformer -
maximum 0.005 (1/2%)
Low value of tan delta indicates low losses
19. TWO WINDINGS IS SAME. THIS IS CALLED
SUBTRACTIVE POLARITY. WHEN THE INDUCED EMFS
ARE IN OPPOSITE DIRECTION , THE POLARITY IS
CALLED ADDITIVE.
PRI. AND SEC. WINDINGS ON ANY ONE LIMB HAVE
INDUCED EMFS THAT ARE IN TIME PHASE. DIFFERENT
COMBINATIONS OF INTERNAL CONNECTIONS AND
CONNECTIONS TO TERMINALS PRODUCE DIFFERENT
PHASE DIVERGENCE OF SEC. VOLTAGE.
VECTOR GROUP OR CONNECTION SYMBOL OF A
TRANSFORMER DENOTES THE METHOD OF
CONNECTION OF PRI. AND SEC. WINDINGS AND THE
PHASE ANGLE DIVERGENCE OF SEC. WITH RESPECT TO
PRIMARY.
22. NECESSARY TO REDUCE THERMAL DEGRADATION OF
INSULATION TO ENSURE LONGER LIFE. HEAT
GENERATED IN THE TR. IS TRANSMITTED TO
ATMOSPHERE THROUGH OIL.
DIFFERENT TYPES OF COOLING:
ONAN TYPE – OIL NATURAL AND AIR NATURAL. HOT
OIL IS CIRCULATED BY NATURAL MEANS DISSIPATING
HEAT TO ATMOSPHERE BY NATURAL MEANS.
ONAF TYPE – OIL NATURAL, AIR FORCED. HERE AIR IS
BLOWN ON TO THE COOLING SURFACES. FORCED AIR
TAKES AWAY HEAT AT A FASTER RATE.
OFAF TYPE – OIL FORCED, AIR FORCED. IF THE OIL IS
FORCE CIRCULATED WITHIN THE TR.AND RADIATOR
BY MEANS OF AN OIL PUMP, IN ADDITION TO FORCED
AIR, STILL BETTER RATE OF HEAT DISSIPATION IS
ACHIEVED OVER ONAF
23. OFWF TYPE – OIL FORCED, WATER FORCED. HERE
WATER IS EMPLOYED FOR COOLING OIL INSTEAD OF
AIR. AMBIENT TEMP. OF WATER IS LESS THAN
ATMOSPHERIC AIR. HENCE BETTER RATE OF COOLING
IS OBTAINED. IN THIS TYPE OIL TO WATER HEAT
EXCHANGERS ARE EMPLOYED. DIFFERENTIAL
PRESSURE BETWEEN OIL AND WATER IS MAINTAINED.
OIL IS CIRCULATED AT A HIGHER PRESSURE.
ODAF/ODWF TYPE – OIL DIRECTED, AIR/WATER
FORCED. IF THE OIL IS DIRECTED TO FLOW PAST THE
WINDINGS, LARGE QUANTITIES OF HEAT CAN BE
TAKEN AWAY BY OIL. COOL OIL IS DIRECTED TO FLOW
THROUGH THE WINDINGS IN PREDETERMINED PATHS.
OIL IS CIRCULATED BY A FORCED OIL SYSTEM LIKE OIL
PUMPS. THIS ENSURES FASTER RATE OF HEAT
TRANSFER.
24. ABSORBS MOISTURE. PRESENCE OF MOISTURE
REDUCES DIELECTRIC STRENGTH OF OIL. DIFFERENT
METHODS ARE AVAILABLE TO REDUCE
CONTAMINATION OF OIL WITH MOISTURE.
1. SILICAGEL BREATHER: IT IS CONNECTED TO THE
CONSERVATOR TANK. IT CONSISTS OF A CARTRIDGE
PACKED WITH SILICAGEL DESSICANT AND A SMALL
CUP CONTAINING OIL. AIR IS DRAWN INTO THE
CONSERVATOR THRO. OIL CUP AND BREATHER WHERE
MOST OF THE MOISTURE IS ABSORBED.
2. BELLOWS AND DIAPHRAGM SEALED
CONSERVATORS: A BELLOW TYPE BARRIER OR A
DIAPHRAGM TYPE BARRIER IS FITTED IN THE
CONSERVATOR. AIR ENTERING THE CONSERVATOR
TANK PUSHES THE DIAPHRAGM DOWNWARDS. AS OIL
EXPANDS THE DIAPHRAGM IS PUSHED UPWARDS.
POSITION OF DIAPHRAGM IS INDICATED BY OIL LEVEL
INDICATOR. DIAPHRAGM ACTS AS A BARRIER.
25. 3. GAS SEALED CONSERVATORS: IN THIS METHOD A CUSHION
OF AN INERT GAS LIKE NITROGEN IS PROVIDED OVER OIL
SURFACE IN THE CONSERVATOR. GAS PRESSURE IS ALWAYS
MAINTAINED HIGHER THAN ATMOSPHERIC PRESSURE.
NITROGEN GAS PRESSURE INSIDE THE CONSERVATOR IS
REGULATED BY NITROGEN CYLINDER AND PRESSURE REDUCING
VALVE WHICH ADMIT NITROGEN TO THE CONSERVATOR WHEN
THE PRESSURE FALLS. EXCESSIVE PRESSURE DEVELOPED
INSIDE THE CONSERVATOR IS RELIEVED THROUGH A RELIEF
VALVE.
4. REFRIGERATION BREATHERS: AN AIR DRYER IS FITTED TO
THE CONSERVATOR. AIR BREATHED THRO. THE UNIT IS DRIED IN
PASSING DOWN A DUCT COOLED BY A SERIES OF
THERMOELECTRIC MODULES BASED ON PELTIER EFFECT. TOP
AND BOTTOM ENDS OF THE DUCT ARE TERMINATED IN THE
EXPANSION SPACE ABOVE OIL LEVEL IN THE CONSERVATOR AND
AIR IS CONTINUOUSLY CIRCULATED THRO. THE DUCT BY
THERMOSYPHON FORCES.
26. SHORT CIRCUIT WITHSTAND CAPACITY:
EFFECTS OF SHORT CIRCUIT: ENERGY IN THE SYSTEM
GETS RELEASED IN THE FORM OF HEAVY FLOW OF
CURRENT WHEN FAULT OCCURS. EVERY FAULT FED
BY THE TRANSFORMER STRESSES THE WINDINGS.
THE STRESS DEVELOPED IN THE WINDING IS RELATED
TO THE INTENSITY OF FAULT. EACH FAULT CAUSES
SHARP RISE IN TEMPERATURE AND PRODUCES
MECHANICAL FORCES IN THE WINDING.
THESE FORCES ACT IN THE AXIAL AND RADIAL
DIRECTIONS OF THE WINDING, AND CAUSE
COMPRESSIVE OR TENSILE STRESSES ON THE
WINDING AND TEND TO DEFORM IT.
27. Radial forces: are due to flux in the space between coils. Tend to
burst coils and crush on the core.
Strengthening of winding
Axial forces: are due to radial component of flux which crosses
the winding at the ends and gives rise to axial compressive force
tending to squeeze the winding in middle.
Proper drying, compression and clamping
28. Thermal effect: rapid rise of temperature causes
I) mechanical weakening of insulation due to thermal ageing
– long term effect.
Ii) decomposition of insulation to produce gases – short term
effect.
Iii) conductor annealing – becomes brittle & cracks will be
formed.
Limit of max. Average temperature after short circuit is
2500
c for oil immersed transformer using copper winding.
29. TAP CHANGERS
ARE DEVICES FOR REGULATING THE VOLTAGE OF
TRANSFORMER.
OFF CIRCUIT TAP CHANGER : TAP CHANGING IS EFFECTED
WHEN TR. IS OFF. THESE ARE CHEAPER. THEY ARE USED
WHERE FREQUENCY OF TAP CHANGING IS VERY LESS.
ON LOAD TAP CHANGER : HERE TAP CHANGING IS EFFECTED
WITHOUT INTERRUPTING LOAD. ON LOAD TAP CHANGER
NORMALLY CONSISTS OF TRANSITION RESISTORS WHICH
BRIDGE THE CIRCUIT DURING TAP CHANGING OPERATION.
TWO TYPES OF OLTCS :
SINGLE COMPARTMENT TYPE – IN THIS TYPE SELECTION OF
TAPS AND SWITCHING ARE CARRIED OUT ON THE SAME
CONTACTS.
DOUBLE COMPARTMENT TYPE – IN THIS TAP SELECTION IS
DONE SEPARATELY AND SWITCHING IS DONE IN A SEPARATE
DIVERTER SWITCH.
30. TYPES OF TAP CHANGERS
Based on applicationBased on application
Off-Circuit tap changerOff-Circuit tap changer
On Load Tap Changer (OLTC)On Load Tap Changer (OLTC)
Based on mounting (for OLTC)
Internal
External
35. MAXIMUM THROUGH CURRENT
INSULATION LEVEL TO GROUND AND BETWEEN
VARIOUS CONTACTS NO OF STEPS AND BASIC
CONNECTIONS
TEMPORARY OVERLOADS AND SHORT CIRCUIT
STRENGTH
AUTOMATIC VOLTAGE REGULATING RELAYS ARE USED
FOR AUTOMATIC CONTROL OF BUS BAR VOLTAGE.
OUTPUT OF VOLTAGE TRANSFORMER CONNECTED TO
CONTROLLED VOLTAGE SIDE OF THE TR. IS USED TO
ENERGIZE AVR RELAY. WHEN VOLTAGE DEVIATION
EXCEEDS A PRESET LIMIT, A CONTROL SIGNAL TO
RAISE OR LOWER TAP OPERATION IS GIVEN. A TIME
DELAY UNIT IS CONNECTED IN THE CIRCUIT TO
PREVENT UNNECESSARY OPERATION OR HUNTING OF
TAP CHANGER DURING TRANSIENT VOLTAGE CHANGE.
36. BASIC CONDITIONS OF OPERATION
Load current must not be interrupted during tap change
operation.
Tap change must occur without short-circuiting the tap
winding directly.
Positive change of tap position.
It means ‘make-before-break’ mechanism to be used.
This calls for a transition impedance.
Also the mechanism should be fast acting type –
spring loaded.
37. GENERAL DESIGN CONSIDERATIONS
Capable to normal load/overloads on transformer.
Maximum system voltage
Step voltage & no. of steps
Test voltage to earth and across tapping range
Maximum surge voltage to earth and across range.
Maximum test voltages between phases (where
applicable)
Current rating – normal and overload
38. PARTS OF TAP CHANGER
Selector switch
Tap selection takes place in this switch
Diverter Switch
Make –before-break mechanism with transition
impedance. Arcing takes place and hence housed in a
separate compartment.
Surge relay
Conservator with oil level gauge.
40. REQUIREMENTS OF TRANSITION
IMPEDANCE
No voltage fluctuations during switching cycle
Circulating currents should not be excessive
Duration of arc should be minimum to minimize contact
erosion and reduce contamination of oil.
41. TAP CHANGER CONTROLS
Manual / Electrical
Local / Remote
Manual / Automatic
Independent Operation
Parallel Operation
Group Control
Master
Follower
44. FEATURES OF TAP CHANGER
Motor drive mechanism
Should rotate in both the directions
Step-by-step operation
Tap change in progress indication
Tap change complete indication
Sequence contact
Remote Tap position control & indication
45. TAP CHANGER OIL QUALITY
Use of tap changer Water content Dielectric strength
At neutral point of
windings
< 40 ppm > 30 KV
At positions other than
neutral end
< 30 ppm > 40 KV
Standard values for transformer oil testing according to
CIGRE 12 – 13 (1982) apply to tap changer oil at
service temperature.
46. OPERATING CONDITIONS
The environment in which a transformer works and the
quality in design and construction play a role on its
performance. A transformer working under normal operating
conditions, in all probability, gives satisfactory performance
throughout its life
.
NORMAL OPERATING CONDITIONS
1. Rated voltage and rated current with permissible margins.
2. Temperatures of oil and windings not exceeding the
prescribed values.
3. Availability of auxiliary and control supply and proper
functioning of accessories and protective devices.
4. Free from external faults such as line breakdowns and
equipment breakdowns.
47. USER SHOULD SPECIFY THE CONDITIONS UNDER WHICH
TRANSFORMER IS EXPECTED TO WORK VIZ. QUALITY
AND NATURE OF LOAD, TEMPERATURE LIMIT, VOLTAGE
CONDITIONS, SHORT CIRCUIT WITHSTAND CAPACITY
CONSIDERING PRESENT AND EXPECTED FAULT LEVELS.
PARAMETERS SPECIFIC TO LOCATIONS ARE TO BE
EVALUATED AND SPECIFIED TO ASSESS THE OPERATING
REQUIREMENT. MANUFACTURERS SHOULD ENSURE
THAT FACTORY TESTS AS REQUIRED UNDER
STANDARDS AND THE USER SPECIFICATIONS ARE DONE
TO VERIFY THE QUALITY AND ABILITY OF THE
TRANSFORMER TO WITHSTAND ALL SERVICE STRESSES
DURING LIFE TIME OF THE TRANSFORMER.
48. Design Basis
• Life-time cost of transformer
= Initial cost of transformer
+
Operational cost for its life period
This is called the
“Capitalized cost of transformer”.
49. DESIGN BASIS - CAPITALIZATION
Rationalized CBIP Capitalization Formula:
Capitalized Cost = Initial Cost (IC) + Capitalized { No-load
Loss (Wn) + Load Loss (Wl) + Auxiliary Losses (Wa) }
Capitalized cost = IC + Xn.Wn +Xl.Wl +
Xa.Wa
Factors affecting Xn; Xl and & Xa
Rate of Interest
Rate of Electrical Energy
Life of Transformer
50. DESIGN BASIS
The design of a transformer aims at achieving lowest
capitalized cost.
Low No-load Loss means higher magnetic material cost and
vice-versa
Low Load Loss means higher copper (material) cost and
vice-versa.
Several iterations are made to optimize the total cost before
freezing the design and drawings are made.
Extensive use of CAD programs is needed for finalizing
design.
53. Higher the number of steps in cross section, better is space
utilization and smaller is the core diameter.
90 to 95 % utilization factor is optimal.
Core area (A) is determined by the Flux Density (B) which
in turn depends on many factors - like loss capitalization and
overall design economics.
As the no load losses attract very high capitalization,
attempts are continuously made to reduce them.
Improved manufacturing techniques like core building with
2-lamination packets, step-lap joints, v-notched laminations,
bolt-less cores are used.
Hi-β core steels like M0H, ZDKH, etc are available in which
the specific core losses are lower than normal grades.
54. A A
V ie w A - A
C o n v e n tio n a l S te p la p
55. WINDINGS- L.V WINDING
L.V Windings in Transformers are either
Spiral OR layer wound for low current ratings
Helical Wound with radial cooling ducts
for higher ratings.
Disc type wound
Distributed Cross-over (Run-over) coils
The conductor used is paper insulated rectangular
copper (PICC)
For higher currents, transposed conductors are used, to
uniformly distribute the current across the cross section
of the wire of coil.
58. TRANSPOSED CONDUCTORS
Transposed conductors (CTC) are used to improve current
distribution in the cross section of the winding wire.
Individual cable can be coated with epoxy so that the cured and
finished conductor is mechanically stronger and withstand short
circuit forces better.
59. H.V WINDING/1
HV winding invariably uses PICC or CTC.
Type of winding used is
- Layer winding or
- Disc winding up to 132 kV and/or
- Interleaved winding or
- Rib shielded winding
60. T em porary O ver-voltage s S w itchin g O ver-voltage s O ver-vo ltages d ue to lightning .
P o w e r S yste m s O ve r vo lta g e s
POWER SYSTEM OVER VOLTAGES
62. SWITCHING OVER-VOLTAGES
Due to system switching operations
1.5 pu – 5 pu dépends on system voltage
mostly damped asymmetric sinusoids
front time of first peak – tens of µs to a few ms.
decides external insulation in EHV/UHV systems
63. OVER VOLTAGES DUE TO
LIGHTNING
Due to ‘direct’ or ‘indirect’ lightning strokes.
known to contribute to ≅ 50% of system outages in EHV
& UHV systems
few hundred kV to several tens of MV.
Few kA to 200 kA
very short duration : time to front : 1 to few tens of µs
time to tail : few tens to hundreds of µs.
Decides line insulation (BIL)
Severely influences Transformer insulation.
64. Cg
Cs
α = K √ Cg/Cs
IMPULSE VOLTAGE DISTRIBUTION
68. Impulse Voltage
Distribution
1. Plain Disc Winding
2. Rib Shield Winding
3. Inter-leaved Disc Winding
Number of discs from line end
V
O
L
T
A
G
E
G
R
A
D
I
E
N
T
P
u
69. TERTIARY WINDING/1
In Star-Star Connected Transformers and Auto
transformers, Tertiary Winding is used to stabilize
phase to phase voltages in case of unbalanced load
- Suppressing third harmonic currents in earthed
neutral
- reducing zero sequence reactance
- for supplying auxiliary load or for connecting
capacitors.
70. TERTIARY WINDING/2
Tertiary is required to be designed for a power rating equal to
one-third the rated power, it increases the cost of the transformer
by 10- 12 percent.
Tertiary winding is known to fail due to transferred surges and
Short circuits
Present practice is to do away with tertiary up to 100 MVA for 3
phase 3 limbed core transformers.
71. DESIGN PROCESS
Design should meet
Requirements of customer specification
Relevant National or International standards
Statutory and regulatory requirements
Manufacturer’s Plant Standards
Optimized design
72. OPTIMIZATION
Objective of Optimization
To arrive at a design that yields minimum capitalized cost.
It is a function of the following:
Core diameter
Core height
Flux Density
Current Density
73. COMPUTER AIDED DESIGN
Improve productivity of design personnel
Release of Engineering information may be 25
– 40% of delivery cycle.
Reduce delivery cycle
Better analysis and arriving at a most optimum
design
To solve electro-static, electro-magnetic problems
and to provide a robust structural and thermal
design.
74. WHY IT IN DESIGN
More precise calculations
Tailor made designs
No standard ratings specified above 1 MVA
Change of specification parameter
Relative change of material cost
Ongoing development of technology
76. WHAT IS QUALITY?
Conformance Quality
Performance Quality
Appearance Quality
Functional Quality
Esteem Quality
‘Ability’ Quality
QUALITY OF
DESIGN/GRADE
FITNESS FOR USE
77. POOR QUALITY RESULTS IN FAILURES.
TYPES OF FAILURES
Infant failures: Early life failures are the result of
latent defects.
- Latent defects are abnormalities that cause failure,
depending on degree of abnormality and amount of
applied stress.
- Delivered defects are those that escape test /
inspection within the factory
- They are directly proportional to total defects in
the entire processes.
78. Mid life failures: These are results of –
- Freak system disturbances
- Wrong specifications
- Poor maintenance
Old age failures: These are results of –
- Ageing of insulation system
- Wear & tear
80. Electrical
* Power frequency
* Over-voltages
(External & Internal)
* Part winding resonance
* Partial Discharge
contd..
82
MAIN FACTORS CAUSING STRESSES IN
THE WINDING
81. 83
Mechanical * Core Vibration
* Force due to Short Circuit
or Faults
* Inrush Current
* Over-fluxing
Thermal * Winding Temperature
* Core loss
* Core
Shorting
* Malfunctioning of Cooling System
* Hot Spot (Local overheat)
* Arcing
82. CHALLENGES IN TRANSFORMER
DESIGN & MANUFACTURING
Structures design (tank etc.)
To be designed for: Lifting & Jacking
Full or partial vacuum
Internal Pressure
Seismic Load
Tests conducted: Leakage test
Vacuum test
Radiography (if specified)
DPT on load bearing items
Contd..
84
83. Short-circuit withstand capability
Adequate radial supports
Use of pre-compressed press-board to minimize shrinkage in service
Proper stabilization of coils
Use of glued conductors
Springs or hydraulic dampers if required
Contd..
85
84. Stray losses control:
Stray losses due to linkage of high magnitude of flux with
magnetic materials
Stray losses form a large part, more than 20% of total load
losses
These may cause hot spots
Measures for stray loss control
Use of laminated material
By breaking the magnetic path
By providing non-magnetic shield
By providing parallel low reluctance
magnetic path contd..
86
85. High Voltage stresses
Design of Insulation system to ensure withstand capability for
Lightning Impulse and Switching Surges.
Long duration high voltage system disturbances
Internal Partial Discharges
This is done by -
Choosing proper type of windings
Calculation/plotting of impulse / switching surges and long duration voltage
stress distribution
Provision of adequate major and minor insulation by using angle rings,
moulded components etc.
Corona shielding where required
87
86. QUALITY DESIGN
PERFORMANCE
Following are prerequisites for a long trouble-free service of the
transformers:
A well designed insulation system.
Good mechanical strength to withstand the inevitable short-
circuit forces.
Proper design review by a team of engineers from Design,
Quality, Marketing, Production etc to ensure that the design is
meeting customer’s specification.
Good manufacturing practices to ensure conformation of the
final product to the design documents.
Proper erection & commissioning and subsequent
maintenance. 88