Report on industrial summer training on 220 kv substation

INDUSTRIAL SUMMER TRAINING
REPORT ON
UTTAR PRADESH POWER CORPORATION LIMITED
220/132 KV SUBSTATION BARAHUWA
GORAKHPUR
Submitted
In Partial Fulfillment of the Requirements
For the Award of Degree of
Bachelor of Technology
In
Electrical Engineering (EE)
Submitted By
Ashutosh Srivastava
(1375120016)
SUBMITTED TO:
Department of Electrical Engineering
KIPM-COLLEGE OF ENGGINEERING AND TECHNOLOGY
(PLOT No.-BL 1&2, Sector 9, GIDA, GORAKHPUR, U.P.-273209)
Dr. A P J ABDUL KALAM Technical University
(Lucknow, Uttar Pradesh-226021)

DECLARATION
I hereby declare that the industrial training report entitled “UPPCL 220/132 KV” is an authentic
record of my own work as requirement of industrial training during the period from 20-06-2016
to 04-08-2016 for the award of degree of Bachelor of Technology (Electrical Engineering),
KIPM-College of Engineering and Technology under the guidance of Mr. Sandeep Kumar
Ashutosh Srivastava
(1375120016)
Date:------------------
Certified that the above statement made by the student is correct to the best of our knowledge
and belief.
Signature
Examined by:
1.
2.
Head of Department
(signature)

CERTIFICATE
This is to certified that Mr. Ashutosh Srivastava has completed 6 week Industrial Training during
the period from 20-06-2016 to 04-08-2016 in our organization as a Partial Fulfillment of Degree
of Bachelor of Technology in Electrical Engineering. He was trained in the field of Power
System Equipment and Protection.
Head of Department
(signature)

ACKNOWLEDGEMENT
Summer training has an important role in exposing the real life situation in an industry.
It was great experience for me to work on the training at UTTAR PRADESH POWER
CORPORATION LIMITED through which I could learn how to work in a professional
environment.
Now, I would like to thank the people who guided me and have been a constant source
of inspiration throughout the tenure of my summer training.
I am sincerely grateful To MR. SANDEEP KUMAR (Sub divisional officer) at
220/132 KV substation, Barahuwa who rendered me his valuable assistance, constant
encouragement and able guidance which made this training actually possible.
I wish my deep sense of gratitude to MR. SANDEEP KUMAR (JUNIOR
ENGINEER) whose affection guidance has enabled me to complete this training successfully.
I also wish my deep sense of gratitude to MR. K. K. PANDEY (HOD: EE
Department) and training coordinator MR. HARI OM SRIVASTAV and MR. SANJAY
GUPTA and Other Faculty members whose guidance and encouragement made my training
successfully.
ASHUTOSH SRIVASTAVA

UTTAR PRADESH POWER CORPORATION LIMITED
Uttar Pradesh Power Corporation Limited (UPPCL) is the company responsible for
electricity transmission and distribution within the Indian state of Uttar Pradesh. Its chairman is
Mr. Sanjay Agarwal. Uttar Pradesh Power Corporation Limited (UPPCL) procures power
from; state government owned power generators, central government owned power generators
and Independent Power Producers through power purchase agreement for lowest per unit cost of
electricity.
The creation of Uttar Pradesh Power Corporation Ltd. (UPPCL) on January 14, 2000 is the
result of power sector reforms and restructuring in UP (India) which is the focal point of the
Power Sector, responsible for planning and managing the sector through its transmission,
distribution and supply of electricity.
UPPCL will be professionally managed utility supplying reliable and cost efficient electricity to
every citizen of the state through highly motivated employees and state of art technologies,
providing an economic return to our owners and maintaining leadership in the country.
The causes of such a poor financial conditions of UPPCL include:
 Higher line losses due to aging over stressed infrastructure
 Pilferage of power at large scale
 Inferior quality of transformers and other equipments
 Selling power much below its purchasing cost.
These can be overcome by forward looking, reliable, safe and trustworthy organization, sensitive
to our customers interests, profitable and sustainable in the long run, providing uninterrupted
supply of quality power, with transparency and integrity in operation.

ABSTRACT
The report gives an overview of 220kv power substation. It includes electricity transmission and
distribution processes at UPPCL, Barahuwa substation. Its substation, an assembly of apparatus
which is installed to control transmission and distribution of electric power, its two main
divisions are outdoor and indoor substation. Different equipments used in substations, Bus-bar,
surge arrestor, Isolator, Earth switches, Current Transformers etc. Transformer which is being
used here is core and shell type transformer for stepping up and down purposes. Different
Instruments transformers, voltage, Current and CV transformers are also being used. Finally the
CVT rating which gives a total output overview.

TABLE OF CONTENTS
CH.NO. TOPIC NAME
1. INTRODUCTION
2. ABOUT SUBSTATION
 Definition
 Sub-Station
 Types of Substation
 220/132KV sub-station
 About the substation
3. SELECTION OF SITE
4. EQUIPMENT IN A 220KV SUB-STATION
 Bus-bar
 Insulators
 Isolating Switches
 Circuit breaker
 Protective relay
 Instrument Transformer
 Current Transformer
 Voltage Transformer
 CapacitorVoltage Transformer
 Metering and Indicating Instrument
 Miscellaneous equipment
 Transformer
 Lightening arrestors
 Line isolator
 Wave trap
5. SINGLE LINE DIAGRAM
6. TRANSFORMER
7. INSULATOR
8. CIRCUIT BREAKER & ISOLATOR
9. CONTROL AND RELAY ROOM

CHAPTER-1
INTRODUCTION
The present day electrical power system is ac i.e. electric power is generated, transmitted and
distributed in the form of Alternating current. The electric power is produce at the power station,
which are located at favorable places, generally quite away from the consumers. It is delivered to
the consumer through a large network of transmission and distribution. At many place in the line
of power system, it may be desirable and necessary to change some characteristic (e.g. Voltage,
ac to dc, frequency power factor etc.) of electric supply. This is accomplished by suitable
apparatus called sub-station for example, generation voltage (11KV or 6.6KV) at the power
station is stepped up to high voltage (Say 220KV to 132KV) for transmission of electric power.
Similarly near the consumer’s localities, the voltage may have to be stepped down to utilization
level. This job is again accomplished by suitable apparatus called sub-station.

CHAPTER-2
ABOUT THE SUBSTATION
1. Definition of sub-station:
“The assembly of apparatus used to change some characteristics (e.g. Voltage ac to dc freq. p.f. etc) of
electric supply is called sub-station”
2. Sub-Station:
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. The word substation comes from the days before the distribution system became a grid.
As central generation stations became larger, smaller generating plants were converted to
distribution stations, receiving their energy supply from a larger plant instead of using their own
generators. The first substations were connected to only one power station, where the generators
were housed, and were subsidiaries of that power station.
3. Types of Substation:
Substations may be described by their voltage class, their applications within the power system,
the method used to insulate most connections, and by the style and materials of the structures
used. These categories are not disjointed; to solve a particular problem, a transmission substation
may include significant distribution functions, for example.
 Transmissionsubstation
 Distribution substation
 Collectorsubstation
 Converter substation
 Switching station

 Transmissionsubstation:
A transmission substation connects two or more transmission lines. The simplest case is where
all transmission lines have the same voltage. In such cases, substation contains high-voltage
switches that allow lines to be connected or isolated for fault clearance or maintenance. A
transmission station may have transformers to convert between two transmission voltages,
voltage control/power factor correction devices such as capacitors, reactors or static VAR
compensators and equipment such as phase shifting transformers to control power flow between
two adjacent power systems.
Transmission substations can range from simple to complex. A small "switching station" may be
little more than a bus plus some circuit breakers. The largest transmission substations can cover a
large area (several acres/hectares) with multiple voltage levels, many circuit breakers and a large
amount of protection and control equipment (voltage and current transformers, relays and
SCADA systems). Modern substations may be implemented using international standards such
as IEC Standard 61850.
 Distribution substation:
A distribution substation in Scarborough, Ontario disguised as a house, complete with a
driveway, front walk and a mown lawn and shrubs in the front yard. A warning notice can be
clearly seen on the "front door". Disguises for substations are common in many cities.
A distribution substation transfers power from the transmission system to the distribution system
of an area. It is uneconomical to directly connect electricity consumers to the main transmission
network, unless they use large amounts of power, so the distribution station reduces voltage to a
level suitable for local distribution.
The input for a distribution substation is typically at least two transmission or sub transmission
lines. Input voltage may be, for example, 115 kV, or whatever is common in the area. The output
is a number of feeders. Distribution voltages are typically medium voltage, between 2.4 kV and
33 kV depending on the size of the area served and the practices of the local utility. The feeders
run along streets overhead (or underground, in some cases) and power the distribution
transformers at or near the customer premises.
In addition to transforming voltage, distribution substations also isolate faults in either the
transmission or distribution systems. Distribution substations are typically the points of voltage
regulation, although on long distribution circuits (of several miles/kilometers), voltage regulation
equipment may also be installed along the line.

The downtown areas of large cities feature complicated distribution substations, with high-
voltage switching, and switching and backup systems on the low-voltage side. More typical
distribution substations have a switch, one transformer, and minimal facilities on the low-voltage
side.
 Collectorsubstation:
In distributed generation projects such as a wind farm, a collector substation may be required. It
resembles a distribution substation although power flow is in the opposite direction, from many
wind turbines up into the transmission grid. Usually for economy of construction the collector
system operates around 35 kV, and the collector substation steps up voltage to a transmission
voltage for the grid. The collector substation can also provide power factor correction if it is
needed, metering and control of the wind farm. In some special cases a collector substation can
also contain an HVDC converter station.
Collector substations also exist where multiple thermal or hydroelectric power plants of
comparable output power are in proximity. Examples for such substations are Brauweiler in
Germany and Hradec in the Czech Republic, where power is collected from nearby lignite-fired
power plants. If no transformers are required for increase of voltage to transmission level, the
substation is a switching station.
 Converter substation:
Converter substations may be associated with HVDC converter plants, traction current, or
interconnected non-synchronous networks. These stations contain power electronic devices to
change the frequency of current, or else convert from alternating to direct current or the reverse.
Formerly rotary converters changed frequency to interconnect two systems; such substations
today are rare.
 Switching station:
(Switchyard at Grand Coulee Dam, USA, 2006)
A switching station is a substation without transformers and operating only at a single voltage
level. Switching stations are sometimes used as collector and distribution stations. Sometimes
they are used for switching the current to back-up lines or for parallelizing circuits in case of
failure. An example is the switching stations for the HVDC Inga–Shaba transmission line.
A switching station may also be known as a switchyard, and these are commonly located directly
adjacent to or nearby a power station. In this case the generators from the power station supply
their power into the yard onto the Generator Bus on one side of the yard, and the transmission
lines take their power from a Feeder Bus on the other side of the yard.

An important function performed by a substation is switching, which is the connecting and
disconnecting of transmission lines or other components to and from the system. Switching
events may be "planned" or "unplanned". A transmission line or other component may need to be
de-energized for maintenance or for new construction, for example, adding or removing a
transmission line or a transformer. To maintain reliability of supply, no company ever brings
down its whole system for maintenance. All work to be performed, from routine testing to
adding entirely new substations, must be done while keeping the whole system running.
Perhaps more important, a fault may develop in a transmission line or any other component.
Some examples of this:
 A line is hit by lightning and develops an arc
 A tower is blown down by high wind.
The function of the switching station is to isolate the faulted portion of the system in the shortest
possible time. De-energizing faulted equipment protects it from further damage, and isolating a
fault helps keep the rest of the electrical grid operating with stability.
4. 220KV Sub-station :
220KV Sub-Station forms an important link between Transmission network and Distribution
network. It has a vital influence of reliability of service. Apart from ensuring efficient
transmission and Distribution of power, the sub-station configuration should be such that it
enables easy maintenance of equipment and minimum interruptions in power supply. Sub-Station
is constructed near as possible to the load center. The voltage level of power transmission is
decided on the quantum of power to be transmitted to the load center.
5. About the substation:
220 KV Barahuwa sub-station is the third largest sub-station of Gorakhpur District. The most
important of any substation is the grounding (Earthing System) of the instruments, transformers
etc. used in the substation for the safety of the operation personnel as well as for proper system
operation and performance of the protective devices. An earths system comprising of an earthing
mat buried at a suitable depth below ground and supplemented with ground rod sat suitable
points is provided in the substations. These ground the extra high voltage to the ground as it is
dangerous to us to go near the instrument without proper earth. If the instruments are not ground
properly they may give a huge shock to anyone who would stay near it and also it is dangerous
for the costly instrument as they may get damaged by this high voltage.

CHAPTER-3
SELECTION OF SITE
Main points to be considered while selecting the site for Grid Sub-Station are as follows:
i) The site chosen should be as near to the load center as possible.
ii) It should be easily approachable by road or rail for transportation of equipments.
iii) Land should be fairly leveled to minimize development cost.
iv) Source of water should be as near to the site as possible. This is because water is
required for various construction activities (especially civil works), earthing and
for drinking purposes etc.
v) The sub-station site should be as near to the town / city but should be clear of
public places, aerodromes, and Military / police installations.
vi) The land should be have sufficient ground area to accommodate substation
equipments, buildings, staff quarters, space for storage of material, such as store
yards and store sheds etc. with roads and space for future expansion.
vii) Set back distances from various roads such as National Highways, State
Highways should be observed as per the regulations in force.
viii) While selecting the land for the Substation preference to be given to the Govt.
land over private land.
ix) The land should not have water logging problem.
x) Far away from obstructions, to permit easy and safe approach/termination of high
voltage overhead transmission lines.

CHAPTER-4
EQUIPMENT IN A 220KV SUB-STATION
The equipment required for a transformer Sub-Station depends upon the type of Sub-Station,
Service requirement and the degree of protection desired.
220KV EHV Sub-Station has the following major equipments:
 Bus-bar
 Insulators
 Isolating Switches
 Circuit breaker
 Protective relay
 Current Transformer
 Voltage Transformer
 Metering and Indicating Instrument
 Miscellaneous equipment
 Transformer
 Lightening arrestors
 Line isolator
 Wave trap
 Bus-bar:
When a no. of lines operating at the same voltage have to be directly connected electrically, bus-
bar are used, it is made up of copper or aluminum bars (generally of rectangular X-Section) and
operate at constant voltage.
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
.

 Insulators:
The insulator serves two purpose, they support the conductor (or bus bar) and confine the current
to the conductor. The most commonly used material for the manufactures of insulators is
porcelain. There are several type of insulator (i.e. pine type, suspension type etc.) and there used
in Sub-Station will depend upon the service requirement.
 Isolating Switches:
In Sub-Station, it is often desired to disconnect a part of the system for general maintenance and
repairs. This is accomplished by an isolating switch or isolator.
An isolator is essentially a knife Switch and is design to often open a circuit under no load, in
other words, isolator Switches are operate only when the line is which they are connected carry
no load. For example, consider that the isolator are connected on both side of a circuit breaker, if
the isolators are to be opened, the C.B. must be opened first.
 Circuit breaker:
A circuit breaker is an equipment, which can open or close a circuit under normal as well as fault
condition. These circuit breaker breaks for a fault which can damage other instrument in the
station.
It is so designed that it can be operated manually (or by remote control) under normal conditions
and automatically under fault condition.
There are mainly two types of circuit breakers used for any substations. They are
(a) SF6 circuit breakers
(b)Spring circuit breakers
For the latter operation a relay which is used with a C.B. generally bulk oil C.B. are used for
voltage up to 66 KV while for high voltage low oil & SF6 C.B. are used. For still higher voltage,
air blast vacuum or SF6 cut breaker are used.
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.

 Protective relay:
A protective relay is a device that detects the fault and initiates the operation of the C.B. to
isolate the defective element from the rest of the system”. The relay detects the abnormal
condition in the electrical circuit by constantly measuring the electrical quantities, which are
different under normal and fault condition. The electrical quantities which may change under
fault condition are voltage, current, frequency and phase angle. Having detect the fault, the relay
operate to close the trip circuit of CB.
 Instrument Transformer:
The line in Sub-station operate at high voltage and carry current of thousands of amperes. The
measuring instrument and protective devices are designed for low voltage (generally 110V) and
current (about 5A). Therefore, they will not work satisfactory if mounted directly on the power
lines. This difficulty is overcome by installing Instrument transformer, on the power lines.
There are two types of instrument transformer-
1. Current Transformer:
A current transformer is essentially a step-down transformer which steps-down the current in a
known ratio, the primary of this transformer consist of one or more turn of thick wire connected
in series with the line, the secondary consist of thick wire connected in series with line having
large number of turn of fine wire and provides for measuring instrument, and relay a current
which is a constant faction of the current in the line. 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 1amp. This is done because we have no instrument for measuring of such a
large current.
The main use of his transformer is:
(a) distance protection
(b) backup protection
(c) measurement
2. Potential Transformer:
It is essentially a step – down transformer and step down the voltage in known ratio. The primary
of these transformer consist of a large number of turn of fine wire connected across the line. The

secondary way consist of a few turns and provides for measuring instruments and relay a voltage
which is known fraction of the line voltage.
3. C V T:
A capacitor voltage transformer (CVT ) is a transformer used in power systems to step-down
extra high voltage signals and provide low voltage signals either for measurement or to operate a
protective relay. In its most basic form the device consists of three parts: two capacitors across
which the voltage signal is split, an inductive element used to tune the device to the supply
frequency and a transformer used to isolate and further step-down the voltage for the
instrumentation or protective relay. The device has at least four terminals, a high-voltage
terminal for connection to the high voltage signal, a ground terminal and at least one set of
secondary terminals for connection to the instrumentation or protective relay. CVTs are typically
single-phase devices used for measuring voltages in excess of one hundred kilovolts where the
use of voltage transformers would be uneconomical. In practice the first capacitor, C1, is often
replaced by a stack of capacitors connected in series. This results in a large voltage drop across
the stack of capacitors that replaced the first capacitor and a comparatively small voltage drop
across the second capacitor,C2, and hence the secondary terminals.
 Metering and Indicating Instrument:
There are several metering and indicating Instrument (e.g. Ammeters, Volt-meters, energy meter
etc.) installed in a Substation to maintain which over the circuit quantities. The instrument
transformers are invariably used with them for satisfactory operation.
 Miscellaneous equipment:
In addition to above, there may be following equipment in a Substation :
i) Fuses
ii) Carrier-current equipment
iii) Sub-Station auxiliary supplies
 Transformer:

There are four transformers in the incoming feeders so that the four 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 Auto
transformer.
Transformer is static equipment which converts electrical energy from one voltage to another. As
the system voltage goes up, the techniques to be used for the Design, Construction, Installation,
Operation and Maintenance also become more and more critical. If proper care is exercised in
the installation, maintenance and condition monitoring of the transformer, it can give the user
trouble free service throughout the expected life of equipment which of the order of 25-35 years.
Hence, it is very essential that the personnel associated with the installation, operation or
maintenance of the transformer is through with the instructions provided by the manufacture
diverted around the protected insulation in most cases to earth.
Auto transformer:
Transformer is static equipment which converts electrical energy from one voltage to another. As
the system voltage goes up, the techniques to be used for the Design, Construction, Installation,
Operation and Maintenance also become more and more critical. If proper care is exercised in
the installation, maintenance and condition monitoring of the transformer, it can give the user
trouble free service throughout the expected life of equipment which of the order of 25-35 years.
Hence, it is very essential that the personnel associated with the installation operation or
maintenance of the transformer is through with the instructions provided by the manufacture.
Basic principles:
The transformer is based on two principles: firstly, that an Electric current can produce a
magnetic field (electromagnetism) and secondly that a changing magnetic field within a coil of
wire induces a voltage across the ends of the coil (electromagnetic induction). Changing the
current in the primary coil changes the magnetic flux that is developed. The changing magnetic
flux induces a voltage in the secondary coil.
It is a device that transfers electrical energy from one circuit to another through inductively
coupled conductors — the transformer's coils. Except for air-core transformers, the conductors
are commonly wound around a single iron-rich core, or around separate but magnetically -
coupled cores. A varying current in the first or "primary" winding creates a varying magnetic
field in the core (or cores) of the transformer. This varying magnetic field induces a varying
electromotive force (EMF) or "voltage" in the "secondary" winding. This effect is called mutual
induction.
If a load is connected to the secondary, an electric current will flow in the secondary winding and
electrical energy will flow from the primary circuit through the transformer to the load. In an
ideal transformer, the induced voltage in the secondary winding (VS) is in proportion to the

primary voltage (VP), and is given by the ratio of the number of turns in the secondary to the
number of turns in the primary as follows:
By appropriate selection of the ratio of turns, a transformer thus allows an alternating current
(AC) voltage to be "stepped up" by making NS greater than NP, or "stepped down" by making
NS less than NP.
Transformers come in a range of sizes from a thumbnail-sized coupling transformer hidden
inside a stage microphone to huge units weighing hundreds of tons used to interconnect portions
of national power grids. All operate with the same basic principles, although the range of designs
is wide. While new technologies have eliminated the need for transformers in some electronic
circuits, transformers are still found in nearly all electronic devices designed for household
("mains") voltage. Transformers are essential for high voltage power transmission, which makes
long distance transmission economically practical. Pole -mounted single-phase transformer with
center-tapped secondary. Note use of the grounded conductor as one leg of the primary feeder.
Induction law:
The voltage induced across the secondary coil may be calculated from Faraday's law of
induction, which states that:
Where VS is the instantaneous voltage, NS is the number of turns in the secondary coil and Φ
equals the magnetic flux through one turn of the coil. If the turns of the coil are oriented
perpendicular to the magnetic field lines, the flux is the product of the magnetic field strength B
and the area A through which it cuts. The area is constant, being equal to the cross-sectional area
of the transformer core, whereas the magnetic field varies with time according to the excitation.
The simplified description above neglects several practical factors, in particular the primary
current required to establish a magnetic field in the core, and the contribution to the field due to
current in the secondary circuit.
Models of an ideal transformer typically assume a core of negligible reluctance with two
windings of zero resistance, when a voltage is applied to the primary winding, a small current
flows, driving flux around the magnetic circuit of the core. The current required to create the flux
is termed the magnetizing current; since the ideal core has been assumed to have near-zero
reluctance, the magnetizing current is negligible, although still required to create the magnetic
field.
The changing magnetic field induces an electromotive force (EMF) across each winding. Since
the ideal windings have no impedance, they have no associated voltage drop, and so the voltage
VP and VS measured at the terminals of the transformer, are equal to the corresponding EMFs.

The primary EMF, acting as it does in opposition to the primary voltage, is sometimes termed the
"back EMF". This is due to Lenz's law which states that the induction of EMF would always be
such that it will oppose development of any such change in magnetic field.
 Lightening Arrester:
To discharge the switching and lightening voltage surges to earth.
 Wave trap:
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.

CHAPTER-5
SINGLE LINE DIAGRAM (SLD)
A Single Line Diagram (SLD) of an Electrical System is the Line Diagram of the concerned
Electrical System which includes all the required ELECTRICAL EQUIPMENT connection
sequence wise from the point of entrance of Power up to the end of the scope of the mentioned
Work.
As these feeders enter the station they are to pass through various instruments. The instruments
have their usual functioning.
They are as follows in the single line diagram:
 Lightening arrestors
 C V T
 Wave trap
 Isolators with earth switch
 Circuit breaker
 BUS
 Potential transformer with a bus isolator
 Isolator
 Current transformer
 A capacitor bank attached to the bus

The line diagram of the substation:
Fig: single line diagram of 220 KV substation Barahuwa
This substation has the capacityof 220kvand can step down to 132kvusing
four input lines through the incoming feeders.
The input feeders are namely,
 PGCIL SAHJANWA
 NTPC TANDA
 GKP CKT-1
 GKP CKT-2
These feeders come into the substationwith 220kv.
The substationof 220kv/132kvhas sevenoutgoing feeders, namely:
 MOHADDIPUR
 MAU-1
 MAU-2(KAUDI RAM)

 FCI-1
 FCI-2
 ANAND NAGAR
 GIDA
These out going feeders are of 132kvline.
Further, the substation of 132kv/33kv has ten outgoing feeders, namely:
 RUSTAMPUR
 PGCIL SAHJANWA
 LAL-DIGGI
 NAUSAD
 HARPUR GANGTAHI
 STATION TRANSFORMER-1
 STATION TRANSFORMER-2(COLONY)
 SAHJANWA
 GIDA
 SPARE

CHAPTER-6
TRANSFORMER
Transformer is a static machine, which transform the potential of alternating current at same
frequency. It means the transformer transforms the low voltage into high voltage and high
voltage into low voltage at same frequency. It works on the principle of static induction
principle. When the energy transformed into higher voltage, the transformer is called step up
transformer but in case of other is known as step down transformer.
Fig: 220/132 KV 160 MVA Transformer at barahuwa sub-station
 TYPES OF TRANSFORMER:
 Power Transformer
 Auto Transformer

Further, Transformerclassifiedin two types:
 On the basis of working
 On the basis of structure
 POWER TRANSFORMER:
Fig: 132/33 KV 40 MVA transformer at barahuwa sub-station

 INSTRUMENT TRANSFORMER:
Fig: Instrument Transformer at Barahuwa Sub-Station
 Auto Transformer:

 POWER TRANSFORMER:
o Single phase transformer
o Three phase transformer
 INSTRUMENT TRANSFORMER:
o Current transformer
o Potential transformer
 AUTO TRANSFORMER:
o Single phase transformer
o Three phase transformer
 On the basis of working:
o Step down: convert HIGH VOLTAGE into LOW VOLTAGE
o Step up: convert LOW VOLTAGE into HIGH VOLTAGE
 On the basis of structure:
o Core Type
o Shell Type

CHAPTER-7
INSULATORS
An electrical insulator is a material whose internal electric charges do not flow freely, and
therefore make it nearly impossible to conduct an electric current under the influence of an
electric field. This contrasts with other materials, semiconductors and conductors, which
conduct electric current more easily. The property that distinguishes an insulator is its
resistivity; insulators have higher resistivity than semiconductors or conductors.
A perfect insulator does not exist, because even insulators contain small numbers of mobile
charges (charge carriers) which can carry current. In addition, all insulators become
electrically conductive when a sufficiently large voltage is applied that the electric field tears
electrons away from the atoms. This is known as the breakdown voltage of an insulator.
Some materials such as glass, paper and Teflon, which have high resistivity, are very good
electrical insulators. A much larger class of materials, even though they may have lower bulk
resistivity, are still good enough to prevent significant current from flowing at normally used
voltages, and thus are employed as insulation for electrical wiring and cables. Examples
include rubber-like polymers and most plastics.
Insulators are used in electrical equipment to support and separate electrical conductors
without allowing current through themselves. An insulating material used in bulk to wrap
electrical cables or other equipment is called insulation. The term insulator is also used more
specifically to refer to insulating supports used to attach electric power distribution or
transmission lines to utility poles and transmission towers. They support the weight of the
suspended wires without allowing the current to flow through the tower to ground.

INSULATING MATERIL
The main cause of failure of overhead line insulator, is the flash over, occurs in between line and
earth during abnormal over voltage in the system.
During the flash over, the huge heat produced by arching, causes puncher in insulator body.
PROPERTIESOF INSULATING MATERIAL:
For successful utilization, this material should have some specific properties as listed
below:
 It must be mechanically strong enough to carry tension and weight of conductors.
 It must have very high dielectric strength to withstand the voltage stresses in High
Voltage system.
 It must possessed high Insulation Resistance to prevent leakage current to the earth.
 The insulating material must be free from unwanted impurities.
 It should not be porous.
 There must not be any entrance on the surface of electrical insulator so that the moisture
or gases can enter in it.
 There physical as well as electrical properties must be less affected by changing
temperature.
TYPES OF INSULATING MATERIALS:

Two types of insulating material are mainly used:
i) Porcelain insulator
ii) Glass insulator
i) Porcelain insulator:
Porcelain in most commonly used material for over head insulator in present days. The porcelain
is aluminium silicate. The aluminium silicate is mixed with plastic kaolin, feldspar and quartz to
obtain final hard and glazed porcelain insulator material.
The surface of the insulator should be glazed enough so that water should not be traced on it.
Fig: porcelain insulator
ii) Glass insulator:
Now days glass insulator has become popular in transmission and distribution system. Annealed
tough glass is used for insulating purpose.

Fig; glass insulator
Advantages of Glass Insulator:
 It has very high dielectric strength compared to porcelain.
 Its resistivity is also very high.
 It has low coefficient of thermal expansion.
 It has higher tensile strength compared to porcelain insulator.
 As it is transparent in nature the is not heated up in sunlight as porcelain.
 The impurities and air bubble can be easily detected inside the glass insulator body
because of its transparency.
 Glass has very long service life as because mechanical and electrical properties of glass
do not be affected by ageing.
 After all, glass is cheaper than porcelain.
DisadvantagesofGlass Insulator:
 Moisture can easily condensed on glass surface and hence air dust will be deposited on
the wed glass surface which will provide path to the leakage current of the system.
 For higher voltage glass can’t be cast in irregular shapes since due to irregular cooling
internal cooling internal strains are caused.

TYPES OF INSULATORS:
There are five types of insulators:
1. Pin type insulator
2. Suspension type insulator
3. Strain type insulator
4. Shackle type insulator
5. Stay type insulator
1. Pin type insulator:
Pin Insulator is earliest developed overhead insulator, but still popularly used in power network
up to 33 KV system. Pin type insulator can be one part, two parts or three parts type, depending
upon application voltage. In 11 KV system we generally use one part type insulator where whole
pin insulator is one piece of properly shaped porcelain or glass. As the leakage path of insulator
is through its surface, it is desirable to increase the vertical length of the insulator surface area for
lengthening leakage path.
Fig: pin type insulator
2. Suspensiontype insulator:
In higher voltage, beyond 33KV, it becomes uneconomical to use pin insulator because size,
weight of the insulator become more. Handling and replacing bigger size single unit insulator are
quite difficult task. For overcoming these difficulties, suspension insulator was developed.

In suspension insulator numbers of insulators are connected in series to form a string and the line
conductor is carried by the bottom most insulator. Each insulator of a suspension string is called
disc insulator because of their disc like shape.
fig: suspension type insulator
3. STRAIN TYPE INSULATOR:
When suspension string is used to sustain extraordinary tensile load of conductor it is referred as
string insulator. When there is a dead end or there is a sharp corner in transmission line, the line
has to sustain a great tensile load of conductor or strain. A strain insulator must have
considerable mechanical strength as well as the necessary electrical insulating properties.
Fig: strain type insulator
4. SHACKLE TYPE INSULATOR:

The shackle insulator or spool insulator is usually used in low voltage distribution network. It
can be used both in horizontal and vertical position. The use of such insulator has decreased
recently after increasing the using of underground cable for distribution purpose. The tapered
hole of the spool insulator distributes the load more evenly and minimizes the possibility of
breakage when heavily loaded. The conductor in the groove of shackle insulator is fixed with the
help of soft binding wire.
Fig: shackle type insulator
5. STAY TYPE INSULATOR:
For low voltage lines, the stays are to be insulated from ground at a height. The insulator used in
the stay wire is called as the stay insulator and is usually of porcelain and is so designed that in
case of breakage of the insulator the guy-wire will not fall to the ground.
Fig: stay type insulator

CHAPTER-8
CIRCUIT BREAKER & ISOLATOR
CIRCUIT BREAKER:
A circuit breaker is the equipment, which can open or close a circuit under normal as well as
fault condition. These circuit breaker breaks for a fault which can damage other instrument in the
station.
It is so designed that it can be operated manually (or by remote control) under normal conditions
and automatically under fault condition.
A circuit breaker is an automatically operated electrical switch designed to protect an electrical
circuit from damage caused by over current or overload or short circuit. Its basic function is to
interrupt current flow after protective relays detect a fault.
Fig: SF6 circuit breaker
WORKING PRINCIPLE OF CIRCUIT BREAKER:
The Circuit Breaker mainly consist of fixed contacts and moving contacts. In normal “no”
condition of circuit breaker, these two contacts are physically connected tp each other due to
applied mechanical pressure on the moving contacts.
There is an arrangement stored potential energy in the operating mechanism of circuit breaker
which is realized if switching signal is given to the breaker. The potential energy can be stored in
the circuit breaker by different ways like by deforming metal spring, by compressed air or by
hydraulic pressure.

TYPES OF CIRCUIT BREAKER:
According to different criteria there are different type of circuit breaker:
According to their arc quenching media the circuit breaker can be divided as:
 Oil circuit breaker
 Air blast circuit breaker
 SF6 circuit breaker
 Vacuum circuit breaker
 OIL CIRCUIT BREAKER:
A high-voltage circuit breaker in which the arc is drawn in oil to dissipate the heat and
extinguish the arc; the intense heat of arc decomposes the oil, generating a gas whose high
pressure produced a flow of fresh fluid through the arc that furnishes the necessary insulation to
prevent a re-strike of the arc.
The arc is then extinguished, both because of its elongation upon parting of contacts and because
of intensive cooling by the gases of oil vacuum.
Fig: oil circuit breaker

 AIR BLAST CIRCUIT BREAKER:
Fast operations, suitability for repeated operation, auto re-closure, unit type multi break
constructions, simple assembly and modest maintenance are some of the main features of air
blast circuit breakers. The compressors plant necessary to maintain high air pressure in the air
receiver. The air blast circuit breakers are especially suitable for railway and arc furnaces, where
the breaker operates repeatedly. Air blast circuit breaker is used for interconnected lines where
rapid operation is desired.
Fig: air blast circuit breaker
High pressure air at a pressure between 20 to 30 kg/cm2 stored in the air reservoir. Air is taken
from the compressed air system. Three hollow insulator columns are mounted on the reservoir
with valves at their basis. The double arc extinguished chambers are mounted on the top of the
hollow insulator chambers. The current carrying parts connect the three arc extinction chamber
to each other in series and the pole to the neighbouring equipment. Since there exist a very high
voltage between the conductor and the air reservoir, the entire arc extinction chambers assembly
is mounted on insulators.
 SF6 CIRCUIT BREAKER:
In such circuit breaker, sulphur hexafluoride (SF6) gas is used as the arc quenching medium. The
SF6 is an electronegative gas and has a strong tendency to absorb free electrons.

The SF6 circuit breakers have been found to a very effective for high power and high voltage
service. SF6 circuit breakers have been developed for voltage 115 KV to 230 KV, power rating
10MVA.
It consists of fixed and moving contacts. It has chamber, contains SF6 gas. When the contacts are
opened, the mechanism permits a high pressure SF6 gas from reservoir to flow towards the arc
interruption chamber. The moving contact permits the SF6 gas to let through these holes.
A typical SF6 circuit breaker consists of interrupter units. Each unit is capable of interrupting
currents up to 60 KA and voltage in the range 50-80 KV. A number of units are connected in
series according to system voltage. SF6 breakers are developed for voltages range from 115 to
500 KV and power of 10MVA rating and with interrupting time of 3 cycles and less.
Fig: SF6 circuit breaker
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.
 VACUUM CIRCUIT BREAKER:
Vacuum circuit breakers are the breakers which are used to protect medium and high voltage
circuit from dangerous electrical situations. Like other types of circuit breakers, vacuum circuit
breakers are literally break the circuit so that energy can not continue flowing through it, thereby
preventing fires, power surge and other problems which may emerge. These devices have been
utilized since the 1920s and several companies have introduced refinements to make them even
safer and more effective.
Fig: vacuum circuit breaker
ISOLATORS:
Isolator is used to ensure that an electrical circuit is completely de-energized for service or
maintenance.
In Sub-Station, it is often desired to disconnect a part of the system for general maintenance and
repairs. This is accomplished by an isolating switch or isolator.
An isolator is essentially a knife Switch and is design to often open a circuit under no load, in
other words, isolator Switches are operate only when the line is which they are connected carry

no load. For example, consider that the isolator are connected on both side of a circuit breaker, if
the isolators are to be opened, the C.B. must be opened first.
“An Isolator or a disconnector is a mechanical switch device, which provides in the open
position, an isolating distance in accordance with special requirements. An isolator is capable of
opening and closing a circuit when either negligible current is broken/made or when no
significant change in the voltage across the terminals of each of the poles of isolator occurs. It is
also capable of carrying current under normal circuit conditions and carrying for a specified
time, current under abnormal conditions such as those of short circuit.”
Fig: isolator
OPERATION OF ELECTRICALISOLATOR:
An isolator is a mechanical switch that is manually operated. Depending on the requirement of a
given system, there are different types of isolators. With isolators, one is able to see any open
circuit physically as compared to circuit breakers where no physical observation can be made.
Since no technique for arc quenching exists in isolators, the operation of electrical isolators
should only be carried out when no possible current is flowing through a circuit. An isolator
should not be used to open a completely closed live circuit. Additionally, live circuits should not
be completed and closed using an isolator. This is to avoid large amounts of arcing from taking
place at the isolator contacts. Hence isolators should only be opened after a circuit breaker is
open and should be closed before closing a circuit breaker.
Electrical isolators can be operated using a motorized mechanism as well as by hand. Hand
operation happens to be cheaper, compared to a motorized arrangement.
As no arc quenching technique is provided in isolator it must be operated when there is no
chance of current flowing through the circuit. No live circuit should be closed or opened by
isolator operation. A complete live closed circuit must not be opened by isolator operation and
also a live circuit must not be closed and completed by isolator to avoid huge arcing in between

isolator contacts. That is why isolator must be open after circuit breaker is open and these must
be closed before circuit breaker is closed. Isolator can be operated by hand locally as well as by
motorized mechanism from remote position. Motorized operation arrangement costs more
compared to hand operation; hence decision must be taken before choosing an isolator for the
system whether hand operated or motor operated economically optimum for the system. For
voltage up to 145 KV system hand operated isolators are used whereas for higher voltage
systems like 245 KV or 420 KV and above motorized isolator are used.
Fig: isolator
TANDEMISOLATORS:
Tandem isolator, often called split breaker or double breakers, provides two separate circuits in
the space of rectangular sized breaker opening. Every circuit breaker panel has a limited number
of circuits available. The problem is that when the openings are all used up and you still need to
add another circuit, what do you do you? You could change the electrical panel or double up
circuits on a breaker, but this could place to much load on a particular circuit. So what then? The
answer that many have found is tandem breaker. This type of breaker is the same size as any
other breaker, but it has its difference.
Fig: Tandem Isolator

CHAPTER-9
CONTROL & RELAY ROOM
The control room has various control panels which shows the information like incomming
power, outgoing power, frequency, time common to all sub-stations, status of various
lines(healthy, faulted, under outage or maintenance), status of various protective instruments like
isolators, circuit breaker, temperature of various instruments, working tap of transformer etc.
The DAS (Data Acquisition System) is used to accumulate the data received from various
sources.
The relay room is separate from the control room. All relay used here are numerical and are
either from Siemens® or ABB®
.
The protection system is so fast that it can detect a fault within 30 ms and hence the circuit
breaker can be operated within as less as 80 ms. For 400KV side C.B., one time auto reclosure is
allowed in order to clear the faults automatically.
BATTERYROOM:
 The control panels and relays of the sub-station required DC supply of 110 V.
 The DC supply is made with the help of battery bank reserve normally kept in a separate
room called battery room.
 The batteries used in this sub-station are Nickel-Cadmium (NI-Cd) batteries. These batteries
re used due to their advantages like low maintenance, longer life (15-20 years) etc.
 Each cell is of 2 V and 300 Ah Capacity.

Fig: batteries at sub-station
Used of battery in sub-station:
Storage battery system is used in emergency situation for the working of electrical equipments:
 To open and close the switch gear
 For indication and control
 Emergency lighting
 Relay and interlocking equipments
 For working of alarm circuit.
Protective Relaying:

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
i. Over Current Relay:
The over current relay responds to a magnitude of current above a specified value. There are four
basic types of construction: They are plunger, rotating disc, static, and microprocessor type. In
the plunger type, a plunger is moved by magnetic attraction when the current exceeds a specified
value. In the rotating induction-disc type, which is a motor, the disc rotates by electromagnetic
induction when the current exceeds a specified value.
Static types convert the current to a proportional D.C mill volt signal and apply it to a level
detector with voltage or contact output. Such relays can be designed to have various current-l
type of rotating induction-disc relay, called the voltage restrained over current relay. The
magnitude of voltage restrains the operation of the disc until the magnitude of the voltage drops
below a threshold value. Static over current relays are equipped with multiple curve
characteristics and can duplicate almost any shape of electromechanical relay curve.
Microprocessor relays convert the current to a digital signal. The digital signal can then be
compared to the setting values input into the relay. With the microprocessor relay, various curves
or multiple time-delay settings can be input to set the relay operation. Some relays allow the user
to define the curve with points or calculations to determine the output characteristics.
ii. Distance Relay:has the overall effect of measuring impedance. The relay operates
instantaneously (within a few cycles) on a 60-cycle basis for values of impedance below the set
value. When time delay is required, the relays energizes a separate time-delay relay or function
with the contacts or output of this time-delay relay or function performing the desired output

functions. The relay operates on the magnitude of impedance measured by the combination of
restraint voltage and the operating current passing through it according to the settings applied to
the relay. When the impedance is such that the impedance point is within the impedance
characteristic circle, the relay will trip. The relay is inherently directional. The line impedance
typically corresponds to the diameter of the circle with the reach of the relay being the diameter
of the circle.
iii. Differential Relay:
The differential relay is a current-operated relay that responds to the difference between two or
more device currents above a set value. The relay works on the basis of the differential principle
that what goes into the device has to come out .If the current does not add to zero, the error
current flows to cause the relay to operate and trip the circuit.
The differential relay is used to provide internal fault protection to equipment such as
transformers, generators, and buses. Relays are designed
to permit differences in the input currents as a result of current transformer mismatch and
applications where the input currents come from different system voltages, such as transformers.
A current differential relay provides restraint coils on the incoming current circuits. The restraint
coils in combination with the operating coil provide an operation curve, above which the relay
will operate. Differential relays are often used with a lockout relay to trip all power sources to
the device and prevent the device from being automatically or remotely reenergized. These
relays are very sensitive. The operation of the device usually means major problems with the
protected equipment and the likely failure in re-energizing the equipment.
iv. DirectionalOver current Relay:
A directional over current relay operates only for excessive current flow in a given direction.
Directional over current relays are available in electromechanical, static, and microprocessor
constructions. An electromechanical overcorrect relay is made directional by adding a directional
unit that prevents the over current relay from operating until the directional unit has operated.
The directional unit responds to the product of the magnitude of current, voltage, and the phase
angle between them or to the product of two currents and the phase angle between them. The
value of this product necessary to provide operation of the directional unit is small, so that it will
not limit the sensitivity of the relay (such as an over current relay that it controls). In most cases,
the directional element is mounted inside the same case as the relay it controls. For example, an
over current relay and a directional element are mounted in the same case, and the combination
is called a directional over current relay. Microprocessor relays often provide a choice as to the
polarizing method that can be used in providing the direction of fault, such as applying residual
current or voltage or negative sequence current or voltage polarizing functions to the relay.

CHAPTER-10
WAVE TRAP
Line trap is also known as wave trap. What it does is trapping the high frequency communication
signals sent on the line from the remote sub-station and diverting them to the
telecom/teleprotection panel in the substation control room (through coupling capacitor and
LMU).
This is relevant in power line carrier communication (PLCC) systems for communication among
various substations without dependence on the telecom company network. The signals are
primarily teleprotection signals and in addition, voice and data communication signals.
The line trap offers high impedance to high frequency communication signals thus obstructs the
flow of these signals in to the substations bus-bars. If there were not to there, then signal loss in
more and communication will be ineffective/probably impossible.
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.

CHAPTER-11
CONCLUSION
Now from this report we can conclude that electricity plays an important role in our life. We are
made aware of how the transmission the transmission of electricity is done. We too came to
know about the various parts of the substation system. The three wings of electrical system viz.
generation, transmission and distribution are connected to each other and that too very perfectly.
Thus for effective transmission and distribution a substation must:
 Ensure steady state and transient stability
 Effective voltage control
 Prevention of loss of synchronism
 Reliable supply by feeding the network at various points
 Fault analysis improvement in respective field
 Establishment of economic load distribution

REFERENCES
 "Joint Consultation Paper: Western Metropolitan Melbourne Transmission Connection and
Subtransmission Capacity" (PDF). Jemena. Powercor Australia, Jemena, Australian Energy
Market Operator. Retrieved 4 February 2016.
 a b c Stockton, Blaine. "Design Guide for Rural Substations" (PDF). USDA Rural
Development. United States Department of Agriculture. Retrieved 4 February 2016.
 Steinberg, Neil. "Lights On but Nobody Home: Behind the Fake Buildings that Power
Chicago". Retrieved 14 December 2013.
 "Transformer Fire Video". metacafe. User Eagle Eye. Retrieved 4 February 2016.
 a b Donald G. Fink, H. Wayne Beatty Standard Handbook for Electrical Engineers Eleventh
Edition, McGraw Hill 1978 ISBN 0-07-020974-X Chapter 17 Substation Design
 Baker, Joseph W,. "Eliminating Hurricane Induced Storm Surge Damage To Electric
Utilities Via In-place Elevation Of Substation Structures And Equipment" (PDF). DIS-
TRAN Packaged Substations. Crest Industries. Retrieved 4 February 2016.
 John, Alvin. "EE35T - Substation Design and Layout". The University Of The West Indies
at St. Augustine, Trinidad And Tobago. Retrieved 4 February 2016.
 R. M. S. de Oliveira and C. L. S. S. Sobrinho (2009). "Computational Environment for
Simulating Lightning Strokes in a Power Substation by Finite-Difference Time-Domain
Method". IEEE Transactions on Electromagnetic Compatibility. 51 (4): 995–1000.
doi:10.1109/TEMC.2009.2028879.
 www.ieeeexplorer.com

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