Electrical substations: 132 KV

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1. 2014 Electrical Substations Project Report, 132 KV Substation, Purukul, Dehradun Power Transmission Corporation of Uttarakhand Limited Submitted By: Girish Gupta Id…
  • 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. 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. 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. 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. 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 Uttaranchal. On 9 November 2000, 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, 2000. The State of Uttaranchal in exercise of the power granted to it under Section 63(4) of the State Re-organization Act, 2000, formed two separate companies in power sector - Uttaranchal Jal Vidyut Nigam Ltd. for generation of hydro-electricity in the state and Uttaranchal Power Corporation Ltd. for transmission & distribution of electricity in the state. Enactment of the Electricity Act, 2003, a distinct watershed in the Indian power sector, as it introduced innovative concepts like power trading, Open Access, Appellate Tribunal, etc., and special provisions for the rural areas, made it mandatory for all the States to restructure their SEBs. As per the provisions of Electricity Act, 2003, the state government separated power transmission business from UPCL which was left only with distribution of electricity. A new company by the name & style of Power Transmission Corporation of Uttaranchal Ltd. was created to handle power transmission business and registered as a Government Company under Section 617 of Companies Act, 1956 on 27th May, 2004. It started functioning w.e.f. 1st June, 2004. 100% shares of the Company is held by the Government of Uttarakhand either directly or through its nominees. Authorized capital of the Company at the time of incorporation was Rs. 10 crores divided into one lac equity shares of Rs. 1000 each. At present the authorized capital of the company is rupees one hundred crores. The Company is managed by the Board of Directors who meet frequently at least once in every quarter. 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. The Corporate and Registered Office of the company is at Vidyut Bhawan, Near ISBT Crossing, Saharanpur Road, Majra, Dehradun. Following given is the power line map of Uttarakhand which shows various installed substations of different capacities and transmission lines in Uttarakhand. It also indicates the position of the new upcoming substations in the different regions.
  • 6. Power and Transmission Line Map of Uttarakhand Project Report 7
  • 7. 5. 132 KV SUBSTATION, PURUKUL, DEHRADUN The 132 KV substation was commissioned in the year 27th March, 1983. There are two main 132 KV bus incoming for the substation. These buses are:- 1. 132 KV Purukul-Dhalipur Line 2. 132 KV Purukul-Majra Line Now the transmission line first parallel connected with lightning arrester to diverge surge, followed by CVT connected parallel. CVT measures voltage and steeps down from 132KV to 63.5 Volts A.C. for control panel, at the location a wave trap is connected to carrier communication at higher frequencies. 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. Switchgear equipment is provided, which is the combination of a circuit breaker having an isolator at each end. Two transformers are connected to main bus. The main bus has total capability of 60 MVA for 132 KV, which is subdivided into two transformer capacity of 60 MVA (40MVA + 20MVA) parallel connected for 132KV. In addition to the Main bus, 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. After the Main bus, lightning arresters, current transformers, isolators and circuit breakers before the transformers are provided. Current Transformers steps down current at ratio 400:200:1 for control panel. Then Transformer step downs voltage from 132KV to 33KV. The main bus is then again provided with switchgear equipment & a current transformer. This gives way to six feeders transmitting power to various places. The main bus is connected to jack bus or transfer bus through a bus coupler & 33KV is provided with switchgear equipment. This gives way to feeders transmitting power to Project Report 8 1. Opto Electronics 2. Anarwala I 3. Anarwala II 4. Mussoorie I 5. Mussoorie II 6. I.T. Park 7. GEMES A step down transformer of 33KV/440V is connected to control panel to provide supply to the equipments of the substation. Capacitor bank is connected to main bus of 33KV. It is provided to improve power factor & voltage profile. Capacitor Bank comprises of two units of 5 MVAR making total capacity of 10 MVAR.
  • 8. At present, an extra 20 MVA transformer is being currently installed at the substation. Also an additional 132 KV Purukul-Bindal Line is now being connected to the substation. Project Report 9
  • 9. Project Report 10 6. SUBSTATIONS A substation is a part of an electrical generation, transmission and distribution system. Substations transform voltage from high to low, or the reverse, or perform any of several other important functions. Between the generating station and consumer, electric power may flow through several substations at different voltage levels. Substations may be owned and operated by an electrical utility, or may be owned by a large industrial or commercial customer. Generally substations are unattended, relying on SCADA for remote supervision and control. A substation may include transformers to change voltage levels between high transmission voltages and lower distribution voltages, or at the interconnection of two different transmission voltages. Substations are classified by two broad categories:- 1. According to the service requirement:  Transformer substation  Switch substation  Power factor correction substation  Frequency change substation  Converting substation  Industrial substation  Collector Substation  Convertor Substation  Switching Substation 2. According to the constructional features:  Indoor substation  Outdoor substation  Underground substation  Pole mounted substation TRANSFORMER SUBSTATION They are known as transformer substations as because transformer is the main component employed to change the voltage level, depending upon the purposed served transformer substations may be
  • 10. 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. These are generally located in the power houses and are of outdoor type. b) PRIMARY GRID SUBSTATION Here, electric power is received by primary substation which reduces the voltage level to 33KV for secondary transmission. The primary grid substation is generally of outdoor type. c) SECONDARY SUBSTATIONS At a secondary substation, the voltage is further steeped down to 11KV. The 11KV lines runs along the important road of the city. The secondary substations are also of outdoor type. d) DISTRIBUTION SUBSTATION These substations are located near the consumer’s localities and step down to 400V, 3- phase, 4-wire for supplying to the consumers. The voltage between any two phases is 400V & between any phase and neutral it is 230V. SUBSTATION CHARACTERISTICS 1. Each circuit is protected by its own circuit breaker and hence plant outage does not necessarily result in loss of supply. 2. A fault on the feeder or transformer circuit breaker causes loss of the transformer and feeder circuit, one of which may be restored after isolating the faulty circuit breaker. 3. A fault on the bus section circuit breaker causes complete shutdown of the substation. All circuits may be restored after isolating the faulty circuit breaker. 4. Maintenance of a feeder or transformer circuit breaker involves loss of the circuit. 5. Introduction of bypass isolators between bus bar and circuit isolator allows circuit breaker maintenance facilities without loss of that circuit.
  • 11. Project Report 12 STEPS IN DESIGNING SUBSTATION The First Step in designing a Substation is to design an Earthing and Bonding System.  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. The earthing system also ensures that no thermal or mechanical damage occurs on the equipment within the substation, thereby resulting in safety to operation and maintenance personnel. The earthing system also guarantees equipotent bonding such that there are no dangerous potential gradients developed in the substation. In designing the substation, three voltages have to be considered these are: 1. 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. 2. 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. 3. Mesh Voltage This is the maximum touch voltage that is developed in the mesh of the earthing grid.  Substation Earthing Calculation Methodology Calculations for earth impedances, touch and step potentials are based on site measurements of ground resistivity and system fault levels. A grid layout with particular conductors is then analyzed to determine the effective substation earthing resistance, from which the earthing voltage is calculated. In practice, it is normal to take the highest fault level for substation earth grid calculation purposes. Additionally, it is necessary to ensure a sufficient margin such that expansion of the system is catered for. To determine the earth resistivity, probe tests are carried out on the site. These tests are best performed in dry weather such that conservative resistivity readings are obtained.  Earthing Materials
  • 12. Project Report 13 1. Conductors Bare copper conductor is usually used for the substation earthing grid. The copper bars themselves usually have a cross-sectional area of 95 square millimeters, and they are laid at a shallow depth of 0.25-0.5m, in 3-7m squares. In addition to the buried potential earth grid, a separate above ground earthing ring is usually provided, to which all metallic substation plant is bonded. 2. Connections Connections to the grid and other earthing joints should not be soldered because the heat generated during fault conditions could cause a soldered joint to fail. Joints are usually bolted. 3. 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. These rods are usually made of solid copper, or copper clad steel.  Switchyard Fence Earthing The switchyard fence earthing practices are possible and are used by different utilities. These are: a) Extend the substation earth grid 0.5m-1.5m beyond the fence perimeter. The fence is then bonded to the grid at regular intervals. b) Place the fence beyond the perimeter of the switchyard earthing grid and bond the fence to its own earthing rod system. This earthing rod system is not coupled to the main substation earthing grid. 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. b) Should be able to withstand forces on it due to its situation. These forces comprise self-weight, and weight of other conductors and equipment, short circuit forces and atmospheric forces such as wind and ice loading. c) Should be corona free at rated voltage. d) Should have the minimum number of joints. e) Should need the minimum number of supporting insulators.
  • 13. Project Report 14 f) Should be economical. The most suitable material for the conductor system is copper or aluminums. Steel may be used but has limitations of poor conductivity and high susceptibility to corrosion. In an effort to make the conductor ideal, three different types have been utilized, and these include: Flat surfaced Conductors, Stranded Conductors, and Tubular Conductors . OVERHEAD LINE TERMINATIONS Two methods are used to terminate overhead lines at a substation. a) Tensioning conductors to substation structures or buildings b) Tensioning conductors to ground winches. The choice is influenced by the height of towers and the proximity to the substation. The following clearances should be observed: VOLTAGE LEVEL MINIMUM GROUND CLEARANCE less than 11kV 6.1m 11kV - 20kV 6.4m 20kV - 30kV 6.7m greater than 30kV 7.0m Clearance in accordance with voltage value
  • 14. STANDARD SIZES OF CONDUCTOR FOR LINES OF VARIOUS VOLTAGES The following sizes have now been standardized by CEA for transmission lines of different voltages:- Project Report 15 1. For 440 KV Lines Twin 'Moose' ACSR having 7-Strands of steel of dia 3.53 mm and 54-Strands of Aluminum of dia 3.53 mm. 2. For 220 KV Lines 'Zebra' ACSR having 7-strand of steel of dia 3.18 mm and 54-Strands of Aluminum of dia 3.18 mm. 3. For 132 KV Lines 'Panther' ACSR having 7-strands of steel of dia 3.00 mm and 30-Strands of Aluminum of dia 3.00 mm.
  • 15. Project Report 16 7. TRANSFORMERS Transformer is a static machine, which transforms the potential of alternating current at same frequency. It means the transformer transforms the low voltage into high voltage & high voltage to low voltage at same frequency. It works on the principle of static induction principle. When the energy is transformed into a higher voltage, the transformer is called step up transformer but in case of other is known as step down transformer. TYPES OF TRANSFORMERS 1. Power Transformer It is used for the transmission purpose at heavy load, high voltage greater than 33 KV & 100% efficiency. It also having a big in size as compare to distribution transformer, it used in generating station and Transmission substation at high insulation level. They can be of two types: Single Phase Transformers and Multi Phase Transformers. 2. Instrument Transformers These transformers are used for the measurement purposes at that points where standard voltmeters and ammeters cannot be used. They are of two types:- a) CURRENT TRANSFORMER A current transformer (CT) is used for measurement of alternating electric currents. When current in a circuit is too high to apply directly to measuring instruments, a current transformer produces a reduced current accurately proportional to the current in the circuit, which can be conveniently connected to measuring and recording instruments. A current transformer isolates the
  • 16. measuring instruments from what may be very high voltage in the monitored circuit. Project Report 17 b) POTENTIAL OR VOLTAGE TRANSFORMER Voltage transformers (VT) (also called potential transformers (PT)) are a parallel connected type of instrument transformer, used for metering and protection in high-voltage circuits or phasor phase shift isolation. They are designed to present negligible load to the supply being measured and to have an accurate voltage ratio to enable accurate metering. A potential transformer may have several secondary windings on the same core as a primary winding, for use in different metering or protection circuits. 3. Auto Transformers An autotransformer is an electrical transformer with only one winding. The "auto" prefix refers to the single coil acting on itself and not to any kind of automatic mechanism. In an autotransformer, portions of the same winding act as both the primary and secondary sides of the transformer. The winding has at least three taps where electrical connections are made. Autotransformers have the
  • 17. advantages of often being smaller, lighter, and cheaper than typical dual-winding transformers, but the disadvantage of not providing electrical isolation. Project Report 18 4. On the basis of working On the above basis, transformers are of two types: Step up Transformer and Step down Transformer. 5. Distribution Transformers A distribution transformer is a transformer that provides the final voltage transmission in the electrical power distribution system, stepping down voltage to the level used by customers.
  • 18. 8. POWER LINE CARRIER COMMUNICATION (PLCC) Reliable & fast communication is necessary for safe efficient & economic power supply. To reduce the power failure in extent & time, to maintain the interconnected grid system in optimum working condition; to coordinate the operation of various generating unit communication network is indispensable for state electricity board. In state electricity boards, 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. Power-line communication (PLC) carries data on a conductor that is also used simultaneously for AC electric power transmission or electric power distribution to consumers. By using the existing AC power lines as a medium to transfer the information, it becomes easy to connect the houses with a high speed network access point without installing new wirings. This technology has been in wide use since 1950 and was mainly used by the grid stations to transmit information at
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