Electrical substations: 132 KV1. 1. 2014 Electrical Substations Project Report, 132 KV Substation, Purukul, Dehradun Power Transmission Corporation of Uttarakhand Limited Submitted By: Girish Gupta Id no. 42206, 4th Year, Electrical Engineering, College of Technology, Govind Ballabh Pant University of Agriculture & Technology, Pantnagar 2. 2. Project Report 3 Sl. No. INDEX Topic Page No. 1. Training Order 2 2. Certificate 4 3. Acknowledgement 5 4. Power Transmission Corporation of Uttarakhand Limited 6 5. 132 KV S/s Purukul, Dehradun 8 6. Substation 10 7. Transformer 16 8. Power Line Carrier Communication 19 9. Bus Bars 22 10. Circuit Breakers 23 11. Isolators 27 12. Insulators 28 13. Relays 30 14. Capacitor Bank 33 15. Protection of Substation 34 16. Conclusion 38 17. Bibliography 39 3. 3. Project Report 4 CERTIFICATE This is to certify that Mr. Girish Gupta, student of 4th year, Electrical Engineering, Bachelor of Technology, College of Technology, Govind Ballabh University of Agriculture & Technology, Pantnagar has undergone summer training at 132KV Substation, Purukul, Dehradun under Power Transmission Corporation of Uttarakhand Limited (PTCUL) from 7th July, 2014 to 7th August, 2014 under the overall guidance of Mr. Prabhash Dabral, S.D.O., Purukul, Dehradun. Mr. Girish Gupta has successfully completed his training and submitted the training project report. During the period of training he was found sincere, punctual and regular. His conduct and behavior was very good. Mr. Prabhash Dabral Sub Division Officer 132 KV Substation PTCUL Purukul, Dehradun 4. 4. Project Report 5 ACKNOWLEDGEMENT I am very thankful to Mr. Ravindra Kumar, Executive Engineer, Power Transmission Corporation of Uttarakhand Limited who gave me an opportunity to undergo training at 132KV Substation, Purukul, Dehradun under Power Transmission Corporation of Uttarakhand Limited (PTCUL). I am also thankful to Mr. Prabhash Dabral, Sub Division Officer, 132 KV Substation, PTCUL who organized the training in a systematic manner and guided me through the whole training programme. I would also like to thank all officer/officials who guided and helped me at each and every step in the training programme. Girish Gupta Id no. 42206 4th year, Electrical Engineering 5. 5. 4. POWER TRANSMISSION CORPORATION OF UTTRAKHAND Project Report 6 LIMITED (PTCUL) Power Transmission Corporation of Uttarakhand Ltd. is the power transmission utility of the state of Uttarakhand formerly known as Open Access. Majra. At present the authorized capital of the company is rupees one hundred crores. formed two separate companies in power sector Uttaranchal Jal Vidyut Nigam Ltd. 132 KV SUBSTATION. The day to day management of the Company is looked after by the Managing Director and other full time Directors of the Company along with other senior officers. 7. 10 crores divided into one lac equity shares of Rs. 2004. etc. 100% shares of the Company is held by the Government of Uttarakhand either directly or through its nominees. Following given is the power line map of Uttarakhand which shows various installed substations of different capacities and transmission lines in Uttarakhand. 2000. a distinct watershed in the Indian power sector. DEHRADUN The 132 KV substation was commissioned in the year 27th March. for control . Authorized capital of the Company at the time of incorporation was Rs. 132 KV Purukul-Majra Line Now the transmission line first parallel connected with lightning arrester to diverge surge. 2003.Uttaranchal. this 27th state of the Republic of India was carved out of the Himalayan and adjoining northwestern districts of Uttar Pradesh per the Uttar Pradesh State Re-organization Act. 2004. On 9 November 2000. 5. 2003. 132 KV Purukul-Dhalipur Line 2. 1956 on 27th May. 2000. A new company by the name & style of Power Transmission Corporation of Uttaranchal Ltd. Dehradun. Appellate Tribunal. CVT measures voltage and steeps down from 132KV to 63. 1983. as it introduced innovative concepts like power trading. 6. Near ISBT Crossing. There are two main 132 KV bus incoming for the substation. The State of Uttaranchal in exercise of the power granted to it under Section 63(4) of the State Reorganization Act. followed by CVT connected parallel. for generation of hydro-electricity in the state and Uttaranchal Power Corporation Ltd. made it mandatory for all the States to restructure their SEBs. It started functioning w. the state government separated power transmission business from UPCL which was left only with distribution of electricity.5 Volts A. The Corporate and Registered Office of the company is at Vidyut Bhawan. was created to handle power transmission business and registered as a Government Company under Section 617 of Companies Act.e.. PURUKUL. The Company is managed by the Board of Directors who meet frequently at least once in every quarter. and special provisions for the rural areas.1. Enactment of the Electricity Act.C. As per the provisions of Electricity Act. for transmission & distribution of electricity in the state. 1000 each. 6.f. These buses are:. It also indicates the position of the new upcoming substations in the different regions. Power and Transmission Line Map of Uttarakhand Project Report 7 7. 1st June. Saharanpur Road. Substations transform voltage from high to low. The main bus is then again provided with switchgear equipment & a current transformer. The main bus is connected to jack bus or transfer bus through a bus coupler & 33KV is provided with switchgear equipment. depending upon the purposed served transformer substations may be Underground substation Outdoor substation Indoor substation Switching Substation 2. This gives way to feeders transmitting power to Project Report 8 1. At present. lightning arresters. Transfer Bus is also provided in the substation in case any maintenance work is to be carried out on the main bus or there is a glitch in the main bus. isolators and circuit breakers before the transformers are provided. at the location a wave trap is connected to carrier communication at higher frequencies. current transformers. Park 7. Capacitor Bank comprises of two units of 5 MVAR making total capacity of 10 MVAR. Opto Electronics 2. Anarwala II 4. This gives way to six feeders transmitting power to various places.panel. A current transformer is connected in series with line which measure current and step down current at ratio 800:400:200:1 for control panel. Then Transformer step downs voltage from 132KV to 33KV. Between the .T. In addition to the Main bus. I. 8. It is provided to improve power factor & voltage profile. After the Main bus. Mussoorie I 5. 8. Mussoorie II 6. 9. According to the constructional features: Convertor Substation Collector Substation Industrial substation Converting substation Frequency change substation Power factor correction substation Switch substation Transformer substation Project Report 10 6. GEMES A step down transformer of 33KV/440V is connected to control panel to provide supply to the equipments of the substation. Two transformers are connected to main bus. which is subdivided into two transformer capacity of 60 MVA (40MVA + 20MVA) parallel connected for 132KV. Pole mounted substation TRANSFORMER SUBSTATION They are known as transformer substations as because transformer is the main component employed to change the voltage level. which is the combination of a circuit breaker having an isolator at each end. The main bus has total capability of 60 MVA for 132 KV. SUBSTATIONS A substation is a part of an electrical generation. Capacitor bank is connected to main bus of 33KV. or the reverse. Switchgear equipment is provided. Current Transformers steps down current at ratio 400:200:1 for control panel. Anarwala I 3. Also an additional 132 KV Purukul-Bindal Line is now being connected to the substation. an extra 20 MVA transformer is being currently installed at the substation. or perform any of several other important functions. Project Report 9 9. transmission and distribution system. Substations may be owned and operated by an electrical utility. Project Report 12 STEPS IN DESIGNING SUBSTATION The First Step in designing a Substation is to design an Earthing Earthing Materials Substation Earthing Calculation Methodology Calculations for earth impedances. 3phase. SUBSTATION CHARACTERISTICS 1. electric power may flow through several substations at different voltage levels. In practice. 11. A fault on the feeder or transformer circuit breaker causes loss of the transformer and feeder circuit. Maintenance of a feeder or transformer circuit breaker involves loss of the circuit. 4. c) SECONDARY SUBSTATIONS At a secondary substation. it is necessary to ensure a sufficient . 4-wire for supplying to the consumers. the voltage is further steeped down to 11KV. A substation may include transformers to change voltage levels between high transmission voltages and lower distribution voltages. or may be owned by a large industrial or commercial customer. Generally substations are unattended. Each circuit is protected by its own circuit breaker and hence plant outage does not necessarily result in loss of supply. These are generally located in the power houses and are of outdoor type. b) PRIMARY GRID SUBSTATION Here. one of which may be restored after isolating the faulty circuit breaker. from which the earthing voltage is calculated. or at the interconnection of two different transmission voltages. electric power is received by primary substation which reduces the voltage level to 33KV for secondary transmission. All circuits may be restored after isolating the faulty circuit breaker. The secondary substations are also of outdoor type. 5. Additionally. touch and step potentials are based on site measurements of ground resistivity and system fault levels. A fault on the bus section circuit breaker causes complete shutdown of the substation. The primary grid substation is generally of outdoor type. 3. Substations are classified by two broad categories:. The 11KV lines runs along the important road of the city.1. it is normal to take the highest fault level for substation earth grid calculation purposes. Project Report 11 classified into: a) STEP UP SUBSTATION The generation voltage is steeped up to high voltage to affect economy in transmission of electric power. relying on SCADA for remote supervision and control. According to the service requirement: 10. A grid layout with particular conductors is then analyzed to determine the effective substation earthing resistance. The voltage between any two phases is 400V & between any phase and neutral it is 230V. d) DISTRIBUTION SUBSTATION These substations are located near the consumer’s localities and step down to 400V.generating station and consumer. 2. 10. Introduction of bypass isolators between bus bar and circuit isolator allows circuit breaker maintenance facilities without loss of that circuit. 11. In designing the substation. In addition to the buried potential earth grid. This earthing rod system is not coupled to the main substation earthing grid. These forces comprise self-weight. These are: a) Extend the substation earth grid 0. Switchyard Fence Earthing The switchyard fence earthing practices are possible and are used by different utilities. d) Should have the minimum number of joints. Earthing and Bonding The function of an earthing and bonding system is to provide an earthing system connection to which transformer neutrals or earthing impedances may be connected in order to pass the maximum fault current. and Bonding System. to which all metallic substation plant is bonded. three voltages have to be considered these are: 1. 2.margin such that expansion of the system is catered for. To determine the earth resistivity.5m-1. c) Should be corona free at rated voltage. and weight of other conductors and equipment. These tests are best performed in dry weather such that conservative resistivity readings are obtained. short circuit forces and atmospheric forces such as wind and ice loading. The earthing system also guarantees equipotent bonding such that there are no dangerous potential gradients developed in the substation. Conductors Bare copper conductor is usually used for the substation earthing grid. and they are laid at a shallow depth of 0. b) Place the fence beyond the perimeter of the switchyard earthing grid and bond the fence to its own earthing rod system. CONDUCTORS USED IN SUBSTATION DESIGN An ideal conductor should fulfill the following requirements: a) Should be capable of carrying the specified load currents and short time currents. Step Voltage This is the potential difference developed when a man bridges a distance of 1m with his feet while not touching any other earthed equipment. a separate above ground earthing ring is usually provided. 2. Touch Voltage This is the difference in potential between the surface potential and the potential at earthed equipment whilst a man is standing and touching the earthed structure.25-0. thereby resulting in safety to operation and maintenance personnel. Connections Connections to the grid and other earthing joints should not be soldered because the heat generated during . The earthing system also ensures that no thermal or mechanical damage occurs on the equipment within the substation. in 3-7m squares. 3. The copper bars themselves usually have a cross-sectional area of 95 square millimeters. 12. The fence is then bonded to the grid at regular intervals. probe tests are carried out on the site.5m. 12. b) Should be able to withstand forces on it due to its situation. Mesh Voltage This is the maximum touch voltage that is developed in the mesh of the earthing grid. e) Should need the minimum number of supporting insulators.Project Report 13 1.5m beyond the fence perimeter. For 440 KV Lines Twin 'Moose' ACSR having 7-Strands of steel of dia 3.20kV 6. and Tubular Conductors . 14. which transforms the potential of alternating current at same frequency. 13.0m Clearance in accordance with voltage value 14.Project Report 15 1. For 220 KV Lines 'Zebra' ACSR having 7-strand of steel of dia 3. it used in generating station and Transmission substation at high insulation level.00 mm. Stranded Conductors.1m 11kV . TRANSFORMERS Transformer is a static machine. 2. In an effort to make the conductor ideal. It also having a big in size as compare to distribution transformer. It means the transformer transforms the low voltage into high voltage & high voltage to low voltage at same frequency.4m 20kV .30kV 6. Instrument Transformers These transformers are used for the . high voltage greater than 33 KV & 100% efficiency. Joints are usually bolted. STANDARD SIZES OF CONDUCTOR FOR LINES OF VARIOUS VOLTAGES The following sizes have now been standardized by CEA for transmission lines of different voltages:. 13. When the energy is transformed into a higher voltage.53 mm and 54-Strands of Aluminum of dia 3. the transformer is called step up transformer but in case of other is known as step down transformer.18 mm and 54-Strands of Aluminum of dia 3. 2. Project Report 14 f) Should be economical. They can be of two types: Single Phase Transformers and Multi Phase Transformers. For 132 KV Lines 'Panther' ACSR having 7-strands of steel of dia 3.fault conditions could cause a soldered joint to fail. 15. TYPES OF TRANSFORMERS 1. Power Transformer It is used for the transmission purpose at heavy load.7m greater than 30kV 7. three different types have been utilized. It works on the principle of static induction principle. The following clearances should be observed: VOLTAGE LEVEL MINIMUM GROUND CLEARANCE less than 11kV 6. OVERHEAD LINE TERMINATIONS Two methods are used to terminate overhead lines at a substation. Steel may be used but has limitations of poor conductivity and high susceptibility to corrosion. These rods are usually made of solid copper. The choice is influenced by the height of towers and the proximity to the substation. or copper clad steel.18 mm. a) Tensioning conductors to substation structures or buildings b) Tensioning conductors to ground winches. and these include: Flat surfaced Conductors.53 mm. Project Report 16 7. Earthing Rods The earthing grid must be supplemented by earthing rods to assist in the dissipation of earth fault currents and further reduce the overall substation earthing resistance. 3. 15. 3.00 mm and 30-Strands of Aluminum of dia 3. The most suitable material for the conductor system is copper or aluminums. for use in different metering or protection circuits. to coordinate the operation of various generating unit communication network is indispensable for state electricity board. stepping down voltage to the level used by customers. a current transformer produces a reduced current accurately proportional to the current in the circuit. Autotransformers have the 17. but the disadvantage of not providing electrical isolation. In an autotransformer. In state electricity boards.measurement purposes at that points where standard voltmeters and ammeters cannot be used. When current in a circuit is too high to apply directly to measuring instruments. portions of the same winding act as both the primary and secondary sides of the transformer. Project Report 18 4. 17. The "auto" prefix refers to the single coil acting on itself and not to any kind of automatic mechanism. and cheaper than typical dualwinding transformers. measuring instruments from what may be very high voltage in the monitored circuit. the generating & distribution stations are generally located at a far distance from cities where P & T communication provided through long overhead lines in neither reliable nor quick. 18. 5. 18. lighter. used for metering and protection in high-voltage circuits or phasor phase shift isolation. A current transformer isolates the 16. The winding has at least three taps where electrical connections are made. They are of two types:. Auto Transformers An autotransformer is an electrical transformer with only one winding. 16. POWER LINE CARRIER COMMUNICATION (PLCC) Reliable & fast communication is necessary for safe efficient & economic power supply. transformers are of two types: Step up Transformer and Step down Transformer. 8. Distribution Transformers A distribution transformer is a transformer that provides the final voltage transmission in the electrical power distribution system. Power-line communication (PLC) carries data on a conductor that is also used . A potential transformer may have several secondary windings on the same core as a primary winding. To reduce the power failure in extent & time. On the basis of working On the above basis. to maintain the interconnected grid system in optimum working condition. 3. which can be conveniently connected to measuring and recording instruments. Project Report 17 b) POTENTIAL OR VOLTAGE TRANSFORMER Voltage transformers (VT) (also called potential transformers (PT)) are a parallel connected type of instrument transformer. advantages of often being smaller. They are designed to present negligible load to the supply being measured and to have an accurate voltage ratio to enable accurate metering.a) CURRENT TRANSFORMER A current transformer (CT) is used for measurement of alternating electric currents. This technology has been in wide use since 1950 and was mainly used by the grid stations to transmit information at high speed. 19. anticipated wind load. By using the existing AC power lines as a medium to transfer the information. Suitably designed coupling equipments have therefore to be employed which will permit the injection of high frequency carrier signal without undue loss and with absolute protection of communication equipments or operating personal from high voltage hazard. On the basis of blocking frequency bank. they cannot be directly connected to high voltage lines. The coupling capacitor are designed for outdoor use and hence to withstand normal atmospheric phenomenon such as temperature & humidity changes. Wave Trap or Line Trap Wave trap is connected in series with power line between the point of connection of coupling capacitor and S/S. Wave trap stands electromechanically and thermally for short circuit current in the event of fault on the line.simultaneously for AC electric power transmission or electric power distribution to consumers. The coupling capacitor used in UPSEB is 2200pf capacitance. one end is connected to the bottom of the . 3. The upper end of the coupling capacitor is connected directly to the line and the lower end is connected to the ground through a carrier frequency chock coil or drain coil. All type of information is modulated on carried wave at frequency 50Hz to 500 KHz. the wave trap can be following type: a) All wave 19. Wave trap offers negligible impedance to HF carrier. nominal wire tension etc. PRINCIPLE OF PLCC Power-line communications systems operate by adding a modulated carrier signal to the wiring system. rain. Coupling Capacitor The modulated carrier is let into power line through coupling capacitor specially designed to with stand line voltage under all-weather condition. it becomes easy to connect the houses with a high speed network access point without installing new wirings. In some case capacitive voltage transformers (CVT) used as a source of line voltage for metering and protection as also used coupling capacitor for PLCC. Protective Device of Coarse Voltage Arrestor This is connected across the primary of the coupling filter i.e. Project Report 19 Therefore. snow. Project Report 20 b) Single Frequency c) Double Frequency’ d) Broad Band 2. Thus coupling capacitor forms the link between the PLCC equipment and power line. Long earlier system double side band amplitude modulation was more common but the present amplitude modulated system. Since high voltage power lines are designed to carry large quantities of energy on the high voltage and the communication system at low voltage. The modulated HF carrier fed into the power line conductor at the sending end and filtered out again at the respective stations. at full rated voltage. the coupling equipment essentially comprises the following: 1. 21.F. c. where voltage of the order of 1. f. which consist of the circuit breaker and isolator. Transmission & Distribution Network: PLCC was first adopted in the electrical transmission and distribution system to transmit information at a fast rate. it is often desired to disconnect a part of the system for general maintenance and repairs. F.coupling capacitor and other end is earthed.8 to 2KV as observed across due to lighting etc. e. Project Report 21 APPLICATION OF PLCC PLCC technology can be deployed into different types of applications in order to provide economic networking solutions. This technology can reduce the resources as well as efforts for activities like power management. video communication can be made with the use of PLCC technology. This unit mainly performs two functions. Cable H. Such a system consists of two bus bars. b. PLCC technology is far useful. d. Wave Trap 21. These are few key areas where PLC communications are utilized: a. 20. An isolating switch or isolator accomplishes this. audio.F. In substations.F. The impedance of this H. It . Coupling of Filter The coupling filter is inserted between the low voltage terminal of the coupling capacitor and the carrier frequency connection of the carrier terminal. 4. Home control and Automation: PLCC technology is used in home control and automation. cable to connection equipments. The cable is insulated to withstand the test voltage of 4KV. Duplicate bus bar system In large stations it is important that break downs and maintenance should interfere as little as possible with continuity of supply to achieve this. Hence merging with other technologies it proves useful in different areas. 20. Telecommunication: Data transmission for different types of communications like telephonic communication. etc. Entertainment: PLCC is used to distribute the multimedia content throughout the home. Sometime an earth switch is also provided with this unit. cable normally used to connect the coupling filter to another coupling terminal. An air gap is provided. This is provided to protect the coupling filter against line surges. Isolator operates under no load condition. duplicate bus bar system is used. H. firstly it isolates the connection of equipment from the power line. Secondly it serves to match characteristic impedance of the power line to that of the H. a main bus bar and a spare bus bar with the help of bus coupler. cable is so as to match with the output of the PLCC terminal and secondary impedance of coupling filter. Automatic Meter Reading – Automatic Meter reading applications use the PLCC technology to send the data from home meters to Host Central Station. on line. energy conservation. Security Systems: In monitoring houses or businesses through surveillance cameras. 5. The thermal portion of the circuit breaker provides an "inverse time" response feature. then circuit breakers. in order to ensure isolation of the circuit breaker from live parts for the purpose of maintenance. Isolators are neces sary on supply side of circuit breakers. This breaker has a 2A . Thermal magnetic circuit breakers Thermal magnetic circuit breakers. The following are the important bus bars arrangements used at substations: 22. Low-voltage circuit breakers Low-voltage (less than 1. Project Report 23 10. Bus Bars Single bus bar system with section alisation. bus bar is used as the common electrical component. which are the type found in most distribution boards.1. Certain designs utilize electromagnetic forces in addition to those of the solenoid. Common trip breakers Three-pole common trip breaker for supplying a three-phase device. the circuit breaker is opened first then isolator while closing a circuit the isolator is closed first. BUSBARS When numbers of generators or feeders operating at the same voltage have to be directly connected electrically. In some cases isolators are used to breaking charging currents or transmission lines. There are different types of circuit breakers which are:. incorporate both techniques with the electromagnet responding instantaneously to large surges in current (short circuits) and the bimetallic strip responding to less extreme but longer-term over-current conditions. 22. and include Miniature Circuit Breaker (MCB) and Molded Case Circuit Breaker (MCCB). 4. Circuit breakers are made in varying sizes. Single bus bar system Project Report 22 9. which operates once and then must be replaced. 23. 23. commercial and industrial application.000 VAC) types are common in domestic. Magnetic circuit breakers Magnetic circuit breakers use a solenoid (electromagnet) whose pulling force increases with the current. 2. Project Report 24 3. CIRCUIT BREAKERS A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit.does not have any specified current breaking capacity or current making capacity. Bus bars are made up of copper rods operate at constant voltage. A transfer isolator is used to transfer main supply from main bus to transfer bus by using bus coupler (combination of a circuit breaker with two isolators). a circuit breaker can be reset (either manually or automatically) to resume normal operation. if repairing or maintenance of any section is required. from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city. which trips the circuit breaker sooner for larger over currents. Its basic function is to detect a fault condition and interrupt current flow. Unlike a fuse. While opening a circuit. but only for safety isolation. and higher for generator circuit breakers. Disconnector can be operated either manually or automatically (motorized disconnector). High-voltage isolation switches are used in electrical substations to allow isolation of apparatus such as circuit breakers. Often used for main power distribution in large industrial plant. 26.300 A and higher for generator circuit breakers.300 A. 24. Sulfur hexafluoride (Sf6) high-voltage circuit breakers A sulfur hexafluoride circuit breaker uses contacts surrounded by sulfur hexafluoride gas to quench the arc. though some models are microprocessor controlled via an integral electronic trip unit. ISOLATERS In electrical engineering. a "common trip" breaker must be used. 24. Project Report 26 8. The disconnector is usually not intended for normal control of the circuit. Oil circuit breakers A high-voltage circuit breaker in which the arc is drawn in oil to dissipate the heat and extinguish the arc. and transmission lines. 26. or for small breakers.rating. 7. each live conductor must be protected by a breaker pole. Such switches are often found in electrical distribution and industrial applications. They are most often used for transmissionlevel voltages and may be incorporated into compact gas-insulated switchgear. Unlike load break switches and circuit . To ensure that all live conductors are interrupted when any pole trips. They are further of two 25. 25. may externally tie the poles together via their operating handles. generating a gas whose high pressure produces a flow of fresh fluid through the arc that furnishes the necessary insulation to prevent a restrike of the arc. the intense heat of the arc decomposes the oil. Usually electronically controlled. Project Report 27 11. Project Report 25 5. These breakers interrupt the current by creating and extinguishing the arc in a vacuum container. The arc is then extinguished. 6. where machinery must have its source of driving power removed for adjustment or repair. Vacuum circuit breakers With rated current up to 6. When supplying a branch circuit with more than one live conductor. for maintenance. Air circuit breakers Rated current up to 6. both because of its elongation upon parting of contacts and because of intensive cooling by the gases and oil vapor. These may either contain two or three tripping mechanisms within one case. disconnect switch or isolator switch is used to ensure that an electrical circuit is completely de-energized for service or maintenance. types: Bulk Oil Circuit Breaker (BOCB) and Minimum Oil Circuit Breaker (MOCB). a disconnector. Trip characteristics are often fully adjustable including configurable trip thresholds and delays. transformers. where the breakers are arranged in draw-out enclosures for ease of maintenance. Disconnectors have provisions for a padlock so that inadvertent operation is not possible (lockout-tag out). they are frequently used for low voltage distribution lines. Suspension insulator For voltages greater than 33 kV. these padlocks may be part of a trapped-key interlock system to ensure proper sequence of operation. the shackle insulators were used as strain insulators. In some designs. Project Report 28 12. The most common used material for the manufacture of insulator is porcelain. suspension type. The insulator serves two purposes. The conductor passes through this groove and is tied to the insulator with annealed wire of the same material as the conductor. In highvoltage or complex systems.) and their use in substation will depend upon the service requirement. Thus. post insulator etc. 27. Pin type insulators are used for transmission and distribution of electric power at voltages up to 33 kV. intended to be opened only after current has been interrupted by some other control device. Pin type insulator As the name suggests. and therefore make it very hard to conduct an electric current under the influence of an electric field. But now a day. Beyond operating voltage of 33 kV. 27. Safety regulations of the utility must prevent any attempt to open the disconnector while it supplies a circuit.g. The conductor is suspended at the bottom end of this string while the other end of the string is secured to the cross -arm of the tower. Shackle insulator In early days. they are off-load devices. Different types of insulator are:28. They support the conductors (bus bar) and confine the current to the conductors.breakers. the pin type insulator is mounted on a pin on the cross -arm on the pole. Such an arrangement would apply to circuits which inter-connect power distribution systems where both ends of the circuit need to be isolated. Consist of a number of porcelain discs connected in series by metal links in the form of a string. There is a groove on the upper end of the insulator. the pin type insulators become too bulky and hence uneconomical. 28. disconnectors lack a mechanism for suppression of electric arc. it is a usual practice to use suspension type insulators shown in Figure. which occurs when conductors carrying high currents are electrically interrupted. Such insulators can be used either in a horizontal position or in a vertical . Standards in some countries for safety may require either local motor isolators or lockable overloads (which can be padlocked). pin type. There are several types of insulators (e. The number of disc units used depends on the voltage. INSULATORS An electrical insulator is a material whose internal electric charges do not flow freely. the isolator switch has the additional ability to earth the isolated circuit thereby providing additional safety. In this way. Relay works on two main operating principles:30. two or more strings are used in parallel. Differential Relay A differential relay is one that operates when vector difference of the two or more electrical quantities exceeds a predetermined value. frequency. strain insulators are used. attached to the crossarm in a horizontal direction. If this differential quantity is equal or greater than the pickup value. such as at long river spans. Electromagnetic Induction RELAY USED IN CONTROLLING PANEL OF SUBSTATION Electromagnetic Attraction The electrical quantities which may change under fault condition are voltage. When main relay sense any fault in the system. Tripping Relay This type of relay is in the conjunction with main relay. When a failure occurs on any part of the system. If it is not equal to zero. However. Over Current Relay This . it must be quickly detected and disconnected from the system. shackle insulators are used as strain insulators. strings of cap-and-pin (disc) insulators are used. the relay will operate and open the circuit breaker to isolate the faulty section. it trips. Project Report 29 29. Rapid disconnection of faulted apparatus limits the amount of damage to it and prevents the effects of fault from spreading into the system. it immediately operates the trip relay to disconnect the faulty section from the section. This result in a heavy current flow through the relay coil. Strain insulator A dead end or anchor pole or tower is used where a straight section of line ends. In order to support this lateral load. current. For low voltage lines (less than 11 kV). 30. RELAYS In a power system it is inevitable that immediately or later some failure does occur somewhere in the system. Earth Fault Relay This type of relay sense the fault between the lines and the earth. Project Report 30 13.position. or angles off in another direction. They can be directly fixed to the pole with a bolt or to the cross arm. This in turn closes the trip circuit of the breaker making the circuit breaker open and isolating the faulty section from the rest of the system. For high voltage circuits relays are employed to serve the desired function of automatic protective gear. phase angle. for high voltage transmission lines. causing the relay to operate by closing its contacts. These poles must withstand the lateral (horizontal) tension of the long straight section of wire. It checks the vector sum of all the line currents. When the tension load in lines is exceedingly high. When a short circuit occurs at any point on the transmission line the current flowing in the line increases to the enormous value. The relays detect the fault and supply the information to the circuit breaker. the relay ensures the safety of the circuit equipment from the damage and normal working of the healthy portion of the system. 29. This flow of oil operates a switch attached to a vane located in the path of the moving oil. This switch normally will operate a circuit breaker to isolate the apparatus before the fault causes additional damage. and oil flows rapidly into the conservator. The low power factor is highly undesirable as it causes increases in current. Auxiliary Relay An auxiliary relay is used to indicate the fault by glowing bulb or showing various flags. These relay are used on A. equipped with an external overhead oil reservoir called a conservator. If an arc forms. This result in the decreased power factor. gas produced by decomposition of insulating oil accumulates in the top of the relay and forces the oil level down. On a slow accumulation of gas.C. Main functions of Capacitor Bank are:33. 32. 33. CAPACITOR BANK The load on the power system is varying being high during morning and evening which increases the magnetization current. Buchholz Relay Buchholz relay is a safety device mounted on some oil-filled power transformers and reactors. The actuating source is the current in the circuit supplied to the relay from a current transformer.type of relay works when current in the circuit exceeds the predetermined value. Depending on design. PROTECTION OF SUBSTATION LIGHTNING ARRESTORS A lightning arrestor is a device used in power systems and telecommunications systems to protect the insulation and conductors of the system from the damaging effects of . This relay operates when phase to phase fault occurs. the relay has multiple methods to detect a failing transformer. So in order to ensure most favorable conditions for a supply system from engineering and economic stand point it is important to have power factor as close to unity as possible.Project Report 34 15. The capacitors draw a leading current and partly or completely neutralize the lagging reactive component of load current. Project Report 31 31. due perhaps to slight overload. Depending on the model. The low power factor is mainly due to the fact most of the power loads are inductive and therefore take lagging currents. A float switch in the relay is used to initiate an alarm signal. Improve Power Factor Improve Terminal Voltage Supply Reactive Power Project Report 33 14. a second float may also serve to detect slow oil leaks. One of such device can be capacitor bank.Project Report 32 32. The Buchholz Relay is used as a protective device sensitive to the effects of dielectric failure inside the equipment. circuit only and can operate for fault flow in the either direction. resulting in additional losses. In order to improve the power factor come device taking leading power should be connected in parallel with the load. gas accumulation is rapid. 31. Various protection methods used for transformers are:34. 35. in most cases to earth. the current from the surge is diverted through the arrestor.lightning. The heat produce in the cores and winding is passed to the oil becomes lighter and rises to the top and place is Marshalling box It has two meter which indicate the temperature of the oil and winding of main tank. A fan produces the blast. Therefore chances of fault occurring on them are very easy rare. the natural circulation of surrounding air is used for its cooling. 2. When a lightning surge (or switching surge. Project Report 37 taken by cool oil from the bottom of the cooling tank. 3. The typical lightning arrester has a high-voltage terminal and a ground terminal.Project Report 35 35. A conservator is used to maintain the oil level up to predetermined value in the transformer main tank by placing it above the level of the top of the tank. which is very similar) travels along the power line to the arrester. 36. forced air is directed over cooling elements of . Transformer cooling When the transformer is in operation heat is generated due to iron losses the removal of heat is called cooling. This provides adequate automatic protection for transformers against possible faults. Conservator and Breather When the oil expands or contacts by the change in the temperature. Oil natural cooling Medium and large rating transformers have their winding and core immersed in oil. This type of cooling is satisfactory for low voltage small transformers. the oil level goes either up or down in main tank. Air natural cooling In a dry type of selfcooled transformers. If temperature of oil or winding exceeds than specified value. During the contraction and expansion of oil air is drawn in or out through breather silica gel crystals impregnated with cobalt chloride. Project Report 36 36. which act both as a cooling medium and an insulating medium. 4. Silica gel is checked regularly and dried and replaced when necessary. Oil blast cooling In this type of cooling. Air blast cooling It is similar to that of dry type self-cooled transformers with to addition that continuous blast of filtered cool air is forced through the core and winding for better cooling. they are as follows: 1. relay operates to sound an alarm. If there is further increase in temperature then relay completes the trip circuit to open the circuit breaker controlling the transformer. Breather is connected to conservator tank for the purpose of extracting moisture as i t spoils the insulating properties of the oil. however the consequences of even a rare fault may be very serious unless the transformer is quickly disconnected from the system. There are several types of cooling methods. 34. TRANSFORMER PROTECTION Transformers are totally enclosed static devices and generally oil immersed. General aspect of energy management and energy audit. Govt.slideshare. Govt. Bureau of energy efficiency. of India.allaboutcircuits. I came to know about the various parts of substations and how they are operated. 6.com 7. Forced oil and forced air flow (OFB) cooling Oil is circulated from the top of the transformers tank to a cooling tank to a cooling plant. Ministry of Power. www. Ministry of Power. 2003.com 5. 37. www. The water is circulated in cooling tubes in the heat exchanger.transformers immersed in oil. www. 38. www. That’s why various protective measures are taken to protect the substations from various faults and its smooth functioning. As evident from the report. Project Report 39 17.wikepedia. www. Energy efficiency in electrical utilities. CONCLUSION Now from this report one can conclude that electricity plays an important role in our life.com . At the end of the training. Oil is then returned to the bottom of the tank.com 4. 2. www.electrical-installation. a substation plays a very important role in the transmission system. of India. Bureau of energy efficiency. BIBLIOGRAPHY 1. Power Transmission Corporation of Uttarakhand Limited takes such steps so that a uniform and stable supply of electricity can reach in every part of this state. 3. Project Report 38 16.org 6. Also I learnt about how transmission is done in various parts of Uttarakhand. 2003. 37. Guide book for National certification examination for energy managers and energy auditors.enspecpower. Forced oil and water (OWF) cooling In this type of cooling oil flow with water cooling of the oil in external water heat exchanger takes place.com 8. 38. 5.home-energy-metering. Guide book for National certification examination for energy managers and energy auditors.