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
Semster:- 5th sem
DELHI TECHNICAL CAMPUS
4th km stone,Main Bahadurgarh Badli Gurgaon Road,
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.
Er.Anees ul Islam.
JE Incharge at substation Wanpoh.
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
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.
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 Arrester
2. Wave Trap
3. Instrument Transformer
Current Transformer and Potential Transformer
4. Bus Bar
5. Circuit Breaker
6. Main Transformer
8. Control and Relay Panel
9. Protective Relaying
10. DC Power Supply
11. Capacitor Bank
12. Switch Gear
Lightening 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
Image of Lightening Arrestor
Wave 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 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 Transformers
b. Potential Transformers
Current 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
a. Distance Protection
b. Backup Protection
A 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.
There 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 it
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
The 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
The 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 are
a. SF6 circuit breakers
b. 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
In 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
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 Panel
The 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 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 relay
ii. Distance relay
iii. Differential relay
iv. 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.
In 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.
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.
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