From 1 June to 30 August 2014

Submitted to :- Submitted by:-Mr.Nikhil Nigam Name:-Sheikh Shakir Zahoor(H O D of EEE Deptt) Branch:-Electrical and Electronics Engineering Semster:- 5th sem

DELHI TECHNICAL CAMPUS

4th km stone,Main Bahadurgarh Badli Gurgaon Road,Phone:+919541234040E-mail:info@delhitechnicalcampus.com

TO WHOMSOEVER IT MAY CONCERN

This is to certify that Mr. Sheikh Shakir Zahoor student of Delhi Technical Campus NayaGaon, Bahadurgarh has undergone his Project training from 26/06/2014 to 14/08/2014 at 132/33 kv substation,Wanpoh Anantnag.

We wish him all the success in his future endeavours.

For JKPDD

Er.Anees ul Islam.JE Incharge at substation Wanpoh.

ACKNOWLEDGEMENT

I would like to express my gratitude and appreciation to all those who gave me the possibility to complete this report.

And to Er.Anees ul Islam ,who was my tutor in doing the project and helped me to complete my training under his supervision.

And also those persons, who work in this Department by giving their useful time to me and shearing their knowledge with us.

And mostly thanks to our ,H.O.D Er. Nikhil Nigam, who gave me permission to enhance my skills in Industry.

And also I want to thank Delhi Technical Campus to give me a chance to get knowledge of industry by permitting thus training during my academic session.

Signature of Head of Department: Signature of Student:Er Nikhil Nigam

Introduction

Any sub-station which handles power at over 132KV is termed as extra High Voltage sub-station by the rules implemented by Indian government. The design process of an EHV sub-station begins with very elemental work of selection of site and estimation of requirements which includes capital and material. It is also needed to keep in mind, the civil aspects of a sub- station design. In India about 75% of electric power used is generated in thermal and nuclear plants, 23% from mostly hydro station and 2% comes from renewable and other resources. The distribution system supplies power to the end consumer, while the transmission system connects between the generating stations and distribution system through transmission line. The entire network forms a power grid and each power grid across the country is interconnected which facilitates uninterrupted supply. While designing a power grid the following aspects must be taken into consideration: 1: Low capital cost. 2: Reliability of the supply power. 3: Low operating cost 4: High efficiency 5: Low cost of energy generation.6: Simplicity of design. 7: Reserve capacity to meet future requirements Starting from the generating stations to the end users, voltage is needed to be stepped up and down several times in various substations. This ensures efficient transmission of power, minimizing the power losses. Our project was a training of six weeks at 132KV/33KV EHV sub-station where the incoming power is received at 132 KV from a generating station. The power factor is corrected here and the voltage is stepped down to 33KV and power is then transferred to distribution system of the grid to meet the requirements of the end consumers at their suitable voltage.

ELECTRICAL SUBSTATION

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. 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.

Image of a Substation

Elements of a Substation The various elements of a substation are:-

1. Lightening Arrester2. Wave Trap3. Instrument Transformer

Current Transformer and Potential Transformer4. Bus Bar5. Circuit Breaker6. Main Transformer7. Isolator8. Control and Relay Panel9. Protective Relaying10. DC Power Supply11. Capacitor Bank12. Switch Gear

Lightening ArresterLightening arrestors are the instrument that are used in the incoming feeders so that to prevent the high voltage entering the main station. This high voltage is very dangerous to the instruments used in the substation. Even the instruments are very costly, so to prevent any damage lightening arrestors are used. The lightening arrestors do not let the lightening to fall on the station. If some lightening occurs the arrestors pull the lightening and ground it to the earth. In any substation the main important is of protection which is firstly done by these lightening arrestors. The lightening arrestors are grounded to the earth so that it can pull the lightening to the ground. The lightening arrestor works with an angle of 30° to 45° making a cone. 

Image of Lightening Arrestor

Wave TrapWave trap is an instrument using for tripping of the wave. The function of this trap is that it traps the unwanted waves. Its function is of trapping wave. Its shape is like a drum. It is connected to the main incoming feeder so that it can trap the waves which may be dangerous to the instruments here in the substation.

Image of Wave trap

 

Instrument TransformerInstrument transformers are used to step-down the current or voltage to measurable values. They provide standardized, useable levels of current or voltage in a variety of power monitoring and measurement applications. Both current and voltage instrument transformers are designed to have predictable characteristics on overloads. Proper operation of over-current protection relays requires that current transformers provide a predictable transformation ratio even during a short circuit.

These are further classified into two types which are discussed below.a. Current Transformersb. Potential Transformers

Current TransformerCurrent transformers are basically used to take the readings of the currents entering the substation. This transformer steps down the current from 800 amps to 1 amp. This is done because we have no instrument for measuring of such a large current. The main use of this transformer isa. Distance Protectionb. Backup Protectionc. MeasurementA current transformer is defined as an instrument transformer in which the secondary current

is substantially proportional to the primary current (under normal conditions of operation) and differs in phase from it by an angle which is approximately zero for an appropriate

direction of the connections. This highlights the accuracy requirement of the current

transformer but also important is the isolating function, which means no matter what the system voltage the secondary circuit need to be insulated only for a low voltage.

Current Transformer

Potential TransformerThere are two potential transformers used in the bus connected both side of the bus. The potential transformer uses a bus isolator to protect itself. The main use of this transformer is to measure the voltage through the bus. This is done so as to get the detail information of the voltage passing through the bus to the instrument. There are two main parts in ita. Measurementb. Protection

The standards define a voltage transformer as one in which the secondary voltage is substantially proportional to the primary voltage and differs in phase from it by an angle which is approximately equal to zero for an appropriate direction of the connections. This in essence means that the voltage transformer has to be as close as possible to the ideal transformer

.

Bus BarThe bus is a line in which the incoming feeders come into and get into the instruments for further step up or step down. The first bus is used for putting the incoming feeders in la single line. There may be double line in the bus so that if any fault occurs in the one the other can still have the current and the supply will not stop. The two lines in the bus are separated by a little distance by a conductor having a connector between them. This is so that one can work at a time and the other works only if the first is having any fault. A bus bar in electrical power distribution refers to thick strips of copper or aluminium that conduct electricity within a switchboard, distribution board, substation, or other electrical apparatus. The size of the bus bar is important in determining the maximum amount of current that can be safely carried. Bus bars are typically either flat strips or hollow tubes as these shapes allow heat to dissipate more efficiently due to their high surface area to cross sectional area ratio. The skin effect makes 50-60 Hz AC bus bars more than about 8 mm (1/3 in) thick inefficient, so hollow or flat shapes are prevalent in higher current applications. A hollow section has higher stiffness than a solid rod of equivalent current carrying capacity, which allows a greater span between bus bar supports in outdoor switchyards. A bus bar may either be supported on insulators or else insulation may completely surround it. Bus bars are protected from accidental contact either by a metal enclosure or by elevation out of normal reach.

Neutral bus bars may also be insulated. Earth bus bars are typically bolted directly onto any metal chassis of their enclosure. Bus bars may be enclosed in a metal housing, in the

form of bus duct or bus way, segregated-phase bus, or isolated-phase bus.

Image of Bus Bar

Circuit BreakerThe circuit breakers are used to break the circuit if any fault occurs in any of the instrument. These circuit breaker breaks for a fault which can damage other instrument in the station. For any unwanted fault over the station we need to break the line current. This is only done automatically by the circuit breaker. There are mainly two types of circuit breakers used for any substations. They area. SF6 circuit breakersb. Spring circuit breakers.

The use of SF6 circuit breaker is mainly in the substations which are having high input kv input, say above 220kv and more. The gas is put inside the circuit breaker by force i.e. under high pressure. When if the gas gets decreases there is a motor connected to the circuit breaker. The motor starts operating if the gas went lower than 20.8 bar. There is a meter connected to the breaker so that it can be manually seen if the gas goes low. The circuit breaker uses the SF6 gas to reduce the torque produce in it due to any fault in the line. The circuit breaker has a direct link with the instruments in the station, when any fault occur alarm bell rings.

The spring type of circuit breakers is used for small kv stations. The spring here reduces the torque produced so that the breaker can function again. The spring type is used for step down side of 132kv to 33kv also in 33kv to 11kv and so on. They are only used in low distribution side.

Sketch of Circuit Breaker

Power TransformerIn substation, transformers are applied to step-up the voltage or step-down the voltage. power plant substation steps up the voltage on the other hand distribution substation step-down the voltage using power transformer. There are three transformers in the incoming feeders so that the three lines are step down at the same time. In case of a 220KV or more KV line station auto transformers are used. While in case of lower KV line such as less than 132KV line double winding transformers are used.

The transformer is transported on trailers to substation site and as far as possible directly unloaded on the plinth. Transformer tanks up to 25 MVA capacity are generally oil filled, and those of higher capacity are transported with N2 gas filled in them. Positive pressure of N2 is maintained in transformer tank to avoid the ingress of moisture. Radiators should be stored with ends duly blanked with gaskets and end plates to avoid in gross of moisture, dust, and any foreign materials inside. The care should be taken to protect the fins of radiators while unloading and storage to avoid further oil leakages. The radiators should be stored on raised ground keeping the fins intact. 

Image of Power Transformer

Isolator

The use of this isolator is to protect the transformer and the other instrument in the line. The isolator isolates the extra voltage to the ground and thus any extra voltage cannot enter the line. Thus an isolator is used after the bus also for protection.

Image of Isolator

Control and Relay PanelThe control and relay panel is of cubical construction suitable for floor mounting. All

protective, indicating and control elements are mounted on the front panel for ease of operation and control. The hinged rear door will provide access to all the internal components to facilitate easy inspection and maintenance. Provision is made for terminating incoming cables at the bottom of the panels by providing separate line-up terminal blocks. For cable entry provision is made both from top and bottom. The control and relay panel accepts CT,

PT aux 230 AC and 220V/10V DC connections at respective designated terminal points. 220V/10V DC supply is used for control supply of all internal relays and timers and also for energizing closing and tripping coils of the breakers. 230V AC station auxiliary supply is used for internal illumination lamp of the panel and the space heater. Protective HRC fuse are provided within the panel for P.T secondary, Aux AC and battery supplies. Each Capacitor Bank is controlled by breaker and provided with a line ammeter with selector switch for 3 phase system & over current relay (2 phases and 1 Earth fault for 3 ph system). Under voltage and over voltage relays. Neutral Current Unbalance Relays are for both Alarm and Trip facilities breaker control switch with local/remote selector switch, master trip relay and trip alarms acknowledge and reset facilities.

Control and Relay Panel

Protective RelayingProtective relays are used to detect defective lines or apparatus and to initiate the operation of circuit interrupting devices to isolate the defective equipment. Relays are also used to detect abnormal or undesirable operating conditions other than those caused by defective equipment and either operate an alarm or initiate operation of circuit interrupting devices. Protective relays protect the electrical system by causing the defective apparatus or lines to be disconnected to minimize damage and maintain service continuity to the rest of the system. There are different types of relays.i. Over current relayii. Distance relayiii. Differential relayiv. Directional over current relay

DC Power Supply DC Battery and Charger

All but the smallest substations include auxiliary power supplies. AC power is required for substation building small power, lighting, heating and ventilation, some communications

equipment, switchgear operating mechanisms, anti-condensation heaters and motors. DC power is used to feed essential services such as circuit breaker trip coils and associated relays, supervisory control and data acquisition (SCADA) and communications equipment. This describes how these auxiliary supplies are derived and explains how to specify such equipment. It has Single 100% battery and 100% charger, Low capital cost, No standby DC System outage for maintenance. Need to isolate battery/charger combination from load under boost charge conditions in order to prevent high boost voltages.

Capacitor bankIn substation shunt capacitors are used for improving the power factor of the system. Shunt capacitors provide reactive power to improve the power factor. During low load condition the shunt capacitance predominates to compensate the shunt capacitance shunt reactance are employed in substation and will be switched on during low load conditions.

Capacitor Bank

SWITCHGEAR The term switchgear, used in association with the electric power system, or grid, refers to the combination of electrical disconnects, fuses and/or circuit breakers used to isolate electrical equipment. Switchgear is used both to de-energize equipment to allow work to be done and to clear faults downstream. Switchgear is already a plural, much like the software term code/codes, and is never used as switchgears.The very earliest central power stations used simple open knife switches, mounted on insulating panels of marble or asbestos. Power levels and voltages rapidly escalated, making open manually-operated switches too dangerous to use for anything other than isolation of a de-energized circuit. Oil-filled equipment allowed arc energy to be contained and safely controlled. By the early 20th century, a switchgear line-up would be a metal- enclosed structure with electrically-operated switching elements, using oil circuit breakers. Today, oil-filled equipment has largely been replaced by air-blast, vacuum, or SF6 equipment, allowing large currents and power levels to be safely controlled by automatic equipment incorporating digital controls, protection, metering and communications.

Switchgear