AN INDSUTRIAL TRAINING

REPORT
UPPCL 132KV SUBSTATION PALIA KALAN
Submitted By-
HARSHIT SHUKLA
B.TECH FINAL YEAR
1604620001
Submitted To-
Mr. Anjaney Nigam

ELECTRICAL ENGINEERING DEPARTMENT

MAHARANA PRATAP ENGINEERING COLLEGE
KOTHI MANDHANA KANPUR

DR. A. P. J. ABDUL KALAM TECHNICAL UNIVERSITY

LUCKNOW
SEPTEMBER 19
 MAHARANA PRATAP ENGINEERING COLLEGE

KOTHI MANDHANA KANPUR

DEPARTMENT OF ELECTRICAL ENGINEERING

CERTIFICATE

Certified that Industrial Training done at “UPPCL 132 KV SUBSTATION PALIA

KALAN” has been carried out by “HARSHIT SHUKLA” in particular fulfillment
of the degree of Bachelor of Technology in Electrical Engineering, during the
academic year 2019-20, to the best of my knowledge and belief. This work is not
been submitted elsewhere for the award of any other degree.

Mrs. Lovi Kaushal Mr. Anjaney Nigam

Head of the Department Assistant Professor
 ACKNOWLEDGEMENT

I would like to express my special thanks of gratitude to my mentor “ Mr. MAURAYA” for their
able guidance and support in completing my training. His dedication and keen interest above all
his overwhelming attitude to help his students and been solely and mainly responsible for
completing my work. His timely advice, meticulous scrutiny, scholarly advice and scientific
approach have helped me to a very great extent to accomplish this task. Primarily. Then I would
like to thank coworkers “Mr. Raj Kishor, Mr. Suresh Maurya, Mr. Deepak Upadhyay, whose
guidance has been the one that helped me patch the report. Then I would like to thank my parents
and friends who have helped me with their valuable suggestions. Last but not the least I would like
to thank my classmate who helped me a lot
 ABSTRACT
A substation receives electrical power from generating station via incoming transmission line and
delivers electrical power through feeders and this is used for controlling the power on different
routes. Substations are integral part of a power system and form important part of transmission
and distribution network of electrical power system Their main functions are to receive energy
transmitted at high voltage from the generating stat ions, reduce the voltage to a value appropriate
for local distribution and provide facilities for switching some sub-station are simply switching
stations different connections between various transmission lines are made, others are converting
sub-stations which either convert AC into DC or vice-versa or convert frequency from higher to
lower or vice-versa. The various circuits are joined together through these components to a bus-
bar at substation. Basically, sub-station consists of power transformers, circuit breakers, relays,
isolators, earthing switches, current transformers, voltage transformers, synchronous condensers/
capacitor banks etc. This mini project covers the important equipment &their function in a sub-
station And also an attempt is made to cover the general maintenance of substation and checks the
observations to be made by shift engineer.

iv
 TABLE OF CONTENT

CHAPTER NO. TITLE PAGE NO.

ABSTRACT iv
TABLE OF CONTENT v
LIST OF FIGURES vi
1. INTRODUCTION 1
2. SELECTION OF SITE 3
3. TYPES OF SUBSTATION 4
3.1 Transmission Substation 4

3.2 Distribution Substation 4

3.3 Collector Substation 5

3.4 Converter Substation 5

3.5 Switching Substation 6

3.6 Railways Substation 6

3.7 Mobile Substation 6

4. DESIGN 7

4.1 Element of Substation 7

4.2 Location Selection 7

4.3 Design Diagram 8

4.4 Automation 9

4.5 Insulation 10

4.6 Structure 10

5. SUBSTATION 11
COMPONENT
5.1 List of Equipment 11
5.1.1 Instrument Transformer 12
 5.1.2 Current Transformer 12

5.1.3 Potential Transformer 13

5.1.4 Conductors 14

5.1.5 Insulators 15

5.1.6 Isolators 15

5.1.7 Busbar 16

5.1.8 Lightning Arrester 17

5.1.9 Circuit Breaker 18

5.1.10 Relays 19

5.1.11 Capacitor Bank 20

5.1.12 Batteries 21

5.1.13 Wave Trapper 22

5.1.14 Switch Yard 23

6. PROTECTION USED IN 24
SUBSTATION
6.1 Distance Protection 24

6.2 Differential Protection 24

6.3 Overvoltage Protection 25

6.4 Overcurrent Protection 25

6.5 Breaker Lock Protection 25

6.7 Earth Fault Protection 26

7. FINAL RESULT AND 27

CONCLUSION
8. SCOPE OF FUTURE 28
STUDY
 LIST OF FIGURES

S. No Name of Figure Page No.

1. Single Line Diagram 2
2. Current Transformer 13
3. Voltage Transformer 14
4. Insulators 15
5. Isolators 16
6. Busbar 17
7. Lightning Arrester 18
8. Circuit Breaker 19
9. Relay 20
10. Capacitor Bank 21
11. Batteries 22
12. Wave Trapper 22
13. Switchyard 23
1
 1. INTRODUCTION
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. Substation may also conclude , circuit
breaker, bus-bar, insulator, lightning arrester are the main components of an electrical substation.

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.

Single Line Diagram of an Electrical Substation

The single line diagram of the substation is shown in the figure below. The connection of the
substation is divided as

 Incoming or power feeder connection

 Outgoing feeder for feeding the other subsequent substations or switchgear.
 Power transformer connection.
 Voltage transformer connection for control and metering.

The circuit breaker is connected between the bus-bar and each incoming and outgoing circuit. The
isolator is provided on each side of the circuit breaker. The current transformer is used for
measurement and protection. The current transformers are placed on both sides of circuit breaker
so that the protection zone are overlapped and cover the circuit breaker. Lightning or surge arrester
are connected phase to ground at the incoming line as the first apparatus and also at the terminal

1
of transformer and capacitor bank, the terminal of shunt reactor and a terminal of the generator,
the terminal of the large motor to divert switching.

Single line diagram of the substation is given below:

Fig.1.1 Single Line Diagram

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2. SELECTION AND LOCATION OF A SITE FOR AN ELECTRICAL
SUBSTATION

The following factor is considered while making site selection for a substation.

2.1 Type of substation – The category of the substation is important for its location. For example,
a step-up transformer is a point where power from various sources is pooled and step up for long
distance transmission should be located as cool as possible to minimize the losses. Similarly, the
step-down transformer should be located nearer to the load center to reduce transmission losses,
the cost of the distribution system and better reliability of supply.

2.2 Availability of suitable and sufficient land – The land selected for a substation should be
level and open from all sides. It should not be waterlogged particularly in the rainy season. The
site selected for substation should be such that approach of transmission lines and their take off
can be easily possible without any obstruction. The places nearer to airdrome, shooting practice
ground, etc. should be avoided.

2.3 Communication facility – Suitable communication facility is desirable at a proposed station,

both during and after its construction. It is better, therefore, to select the site alongside the existing
road to facilitate an easier and cheaper transportation.

2.4 Atmospheric Pollution – The atmosphere around the ground factories produces metal
corroding gas, air fumes, conductive dust, etc. And the area near the sea coast may be more humid
and is harmful to the proper running of the power system. Thus, the substation should not be
located near the factories or sea coast.

2.5 Availability of Essential Facilities to the Staff – The site should be such where staff can be
provided essential facilities like school, hospital, drinking water, housing, etc.

2.6 Drainage Facility – The site selected for the proposed substations should have proper drainage
arrangement or the possibility of making effective drainage, avoid pollution of air and growth of
micro-organism and health.

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 3. TYPES OF SUBSTATIONS
1. Transmission substation

2. Distribution Substation

3. Collector Substation

4. Converter Substation

5. Switching Substation

6. railways Substation

7. Mobile Substation

3.1 Transmission substation

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).

3.2 Distribution substation

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.

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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.

3.3 Collector substation

In distributed generation projects such as a wind farm or Photovoltaic power station, a collector
substation may be required. It resembles a distribution substation although power flow is in the
opposite direction, from many wind turbines or inverters up into the transmission grid. Usually for
economy of construction the collector system operates around 35 kV, although some collector
systems are 12 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.

3.4 Converter substations

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.

5
Formerly rotary converters changed frequency to interconnect two systems; nowadays such
substations are rare.

3.5 Switching station

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, companies aim at keeping the system up and
running while performing maintenance. All work to be performed, from routine testing to adding
entirely new substations, should be done while keeping the whole system running.

3.6 Railways
Electrified railways also use substations, often distribution substations. In some cases a conversion
of the current type takes place, commonly with rectifiers for direct current (DC) trains, or rotary
converters for trains using alternating current (AC) at frequencies other than that of the public grid.
Sometimes they are also transmission substations or collector substations if the railway network
also operates its own grid and generators to supply the other stations.

3.7 Mobile substation

A mobile substation is a substation on wheels, containing a transformer, breakers and busywork
mounted on a self-contained semi-trailer, meant to be pulled by a truck. They are designed to be
compact for travel on public roads, and are used for temporary backup in times of natural
disaster or war.

6
 4. DESIGN
4.1 Element of Substation

Substations generally have switching, protection and control equipment, and transformers. In a
large substation, circuit breakers are used to interrupt any short circuits or overload currents that
may occur on the network. Smaller distribution stations may use recloser circuit
breakers or fuses for protection of distribution circuits. Substations themselves do not usually have
generators, although a power plant may have a substation nearby. Other devices such
as capacitors, voltage regulators, and reactors may also be located at a substation.

Substations may be on the surface in fenced enclosures, underground, or located in special-purpose

buildings. High-rise buildings may have several indoor substations. Indoor substations are usually
found in urban areas to reduce the noise from the transformers, for reasons of appearance, or to
protect switchgear from extreme climate or pollution conditions.

A grounding (earthing) system must be designed. The total ground potential rise, and the gradients
in potential during a fault (called touch and step potentials), must be calculated to protect passers-
by during a short-circuit in the transmission system. Earth faults at a substation can cause a ground
potential rise. Currents flowing in the Earth's surface during a fault can cause metal objects to have
a significantly different voltage than the ground under a person's feet; this touch potential presents
a hazard of electrocution. Where a substation has a metallic fence, it must be properly grounded
to protect people from this hazard.

The main issues facing a power engineer are reliability and cost. A good design attempts to strike
a balance between these two, to achieve reliability without excessive cost. The design should also
allow expansion of the station, when required.

4.2 Location Selection

Selection of the location of a substation must consider many factors. Sufficient land area is required
for installation of equipment with necessary clearances for electrical safety, and for access to
maintain large apparatus such as transformers.

Where land is costly, such as in urban areas, gas insulated switchgear may save money overall.
Substations located in coastal areas affected by flooding and tropical storms may often require an

7
elevated structure to keep equipment sensitive to surges hardened against these elements.[8] The
site must have room for expansion due to load growth or planned transmission additions.
Environmental effects of the substation must be considered, such as drainage, noise and road
traffic effects.

The substation site must be reasonably central to the distribution area to be served. The site must
be secure from intrusion by passers-by, both to protect people from injury by electric shock or
arcs, and to protect the electrical system from mis operation due to vandalism.

4.3 Design Diagram

The first step in planning a substation layout is the preparation of a one-line diagram, which shows
in simplified form the switching and protection arrangement required, as well as the incoming
supply lines and outgoing feeders or transmission lines. It is a usual practice by many electrical
utilities to prepare one-line diagrams with principal elements (lines, switches, circuit breakers,
transformers) arranged on the page similarly to the way the apparatus would be laid out in the
actual station.

In a common design, incoming lines have a disconnect switch and a circuit breaker. In some cases,
the lines will not have both, with either a switch or a circuit breaker being all that is considered
necessary. A disconnect switch is used to provide isolation, since it cannot interrupt load current.
A circuit breaker is used as a protection device to interrupt fault currents automatically, and may
be used to switch loads on and off, or to cut off a line when power is flowing in the 'wrong'
direction. When a large fault current flows through the circuit breaker, this is detected through the
use of current transformers. The magnitude of the current transformer outputs may be used to trip
the circuit breaker resulting in a disconnection of the load supplied by the circuit break from the
feeding point. This seeks to isolate the fault point from the rest of the system, and allow the rest of
the system to continue operating with minimal impact. Both switches and circuit breakers may be
operated locally (within the substation) or remotely from a supervisory control center.

With overhead transmission lines, the propagation of lightning and switching surges can
cause insulation failures into substation equipment. Line entrance surge arrestors are used to
protect substation equipment accordingly. Insulation Coordination studies are carried out
extensively to ensure equipment failure (and associated outages) is minimal.
8
Once past the switching components, the lines of a given voltage connect to one or more buses.
These are sets of busbars, usually in multiples of three, since three-phase electrical power
distribution is largely universal around the world.

The arrangement of switches, circuit breakers, and buses used affects the cost and reliability of the
substation. For important substations a ring bus, double bus, or so-called "breaker and a half" setup
can be used, so that the failure of any one circuit breaker does not interrupt power to other circuits,
and so that parts of the substation may be de-energized for maintenance and repairs. Substations
feeding only a single industrial load may have minimal switching provisions, especially for small
installations.

Once having established buses for the various voltage levels, transformers may be connected
between the voltage levels. These will again have a circuit breaker, much like transmission lines,
in case a transformer has a fault(commonly called a "short circuit").

Along with this, a substation always has control circuitry needed to command the various circuit
breakers to open in case of the failure of some component.

4.4 Automation

Early electrical substations required manual switching or adjustment of equipment, and manual
collection of data for load, energy consumption, and abnormal events. As the complexity of
distribution networks grew, it became economically necessary to automate supervision and control
of substations from a centrally attended point, to allow overall coordination in case of emergencies
and to reduce operating costs. Early efforts to remote control substations used dedicated
communication wires, often run alongside power circuits. Power-line carrier, microwave
radio, fiber optic cables as well as dedicated wired remote control circuits have all been applied
to Supervisory Control and Data Acquisition (SCADA) for substations. The development of
the microprocessor made for an exponential increase in the number of points that could be
economically controlled and monitored. Today, standardized communication protocols such
as DNP3, IEC 61850 and Modbus, to list a few, are used to allow multiple intelligent electronic
devices to communicate with each other and supervisory control centers. Distributed automatic
control at substations is one element of the so-called smart grid.

9
4.5 Insulation

Switches, circuit breakers, transformers and other apparatus may be interconnected by air-
insulated bare conductors strung on support structures. The air space required increases with
system voltage and with the lightning surge voltage rating. For medium-voltage distribution
substations, metal-enclosed switch gear may be used and no live conductors exposed at all. For
higher voltages, gas-insulated switch gear reduces the space required around live bus. Instead of
bare conductors, bus and apparatus are built into pressurized tubular containers filled with sulfur
hexafluoride (SF6) gas. This gas has a higher insulating value than air, allowing the dimensions of
the apparatus to be reduced. In addition to air or SF6 gas, apparatus will use other insulation
materials such as transformer oil, paper, porcelain, and polymer insulators.

4.6 Structure

Outdoor, above-ground substation structures include wood pole, lattice metal tower, and tubular
metal structures, although other variants are available. Where space is plentiful and appearance of
the station is not a factor, steel lattice towers provide low-cost supports for transmission lines and
apparatus. Low-profile substations may be specified in suburban areas where appearance is more
critical. Indoor substations may be gas-insulated switchgear (at high voltages), or metal-enclosed
or metal-clad switchgear at lower voltages. Urban and suburban indoor substations may be finished
on the outside so as to blend in with other buildings in the area.

A compact substation is generally an outdoor substation built in a metal enclosure, in which each
item of the electrical equipment is located very near to each other to create a relatively smaller
footprint size of the substation.

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5. ELECTRICAL SUBSTATION COMPONENTS

The electricity substation is a network of electrical equipment which is connected in a structured

way in order to supply electricity to end consumers. There is numerous electrical substation
components like outgoing and incoming circuitry each of which having its circuit breakers,
isolators, transformers, and busbar system etc. For the smooth functioning of the system. The
power system is having numerous ingredients such as distribution, transmission, and generation
systems and Substations act as a necessary ingredient for operations of the power system. The
substations are entities from which consumers are getting their electrical supply to run their loads
while required power quality can be delivered to the customers by changing frequency and voltage
levels etc..

5.1 List of Electrical Substation Equipment:

1. Instrument Transformers

2. Current Transformer

3. Potential Transformer

4. Conductors

5. Insulators

6. Isolators

7. Busbars

8. Lightning Arrestors

9. Circuit Breakers

10. Relays

11. Capacitor Banks

11
12. Batteries

13. Wave Trapper

14. Switchyard

15. Metering and Indication Instruments

16. Equipment for Carrier Current

17. Prevention from Surge Voltage

18. The Outgoing Feeders

5.1.1. Instrument Transformer

The instrument transformer is a static device utilized for reduction of higher currents and voltages
for safe and practical usage which are measurable with traditional instruments such as digital
multi-meter etc. The value range is from 1A to 5A and voltages such as 110V etc. The transformers
are also used for actuation of AC protective relay through supporting voltage and current.
Instrument transformers are shown in the figure below and its two types are also discussed
underneath.

5.1.2. Current Transformer

A current transformer (CT) is a type of transformer that is used to reduce or multiply an alternating
current (AC). It produces a current in its secondary which is proportional to the current in its
primary.

Current transformers, along with voltage or potential transformers, are instrument transformers.
Instrument transformers scale the large values of voltage or current too small, standardized values
that are easy to handle for measuring instruments and protective relays. The instrument
transformers isolate measurement or protection circuits from the high voltage of the primary
system. A current transformer provides a secondary current that is accurately proportional to the

12
current flowing in its primary. The current transformer presents a negligible load to the primary
circuit.

Current transformers are the current-sensing units of the power system and are used at generating
stations, electrical substations, and in industrial and commercial electric power distribution

Fig.2 Current Transformer

5.1.3. Potential Transformers

Potential transformer is a voltage step-down transformer which reduces the voltage of a high
voltage circuit to a lower level for the purpose of measurement. These are connected across or
parallel to the line which is to be monitored.
The basic principle of operation and construction of this transformer is similar to the standard
power transformer. In common, the potential transformers are abbreviated as PT.
The primary winding consists of a large number of turns which is connected across the high voltage
side or the line in which measurements have to be taken or to be protected. The secondary winding

13
has lesser number of turns which is connected to the voltmeters, or potential coils of wattmeter
and energy meters, relays and other control devices. These can be single phase or three phase
potential transformers. Irrespective of the primary voltage rating, these are designed to have the
secondary output voltage of 110 V.
Since the voltmeters and potential coils of other meters have high impedance, a small current flows
through the secondary of PT. Therefore, PT behaves as an ordinary two winding transformer
operating on no load. Due to this low load (or burden) on the PT, the VA ratings of PTs are low
and in the range of 50 to 200 VA. On the secondary side, one end is connected to the ground for
safety reasons

Fig.3 Voltage Transformer

5.1.4. Conductors
Conductors are the materials which permit flow of electrons through it. The best conductors are
copper and aluminum etc. The conductors are utilized for transmission of energy from place to
place over substations.

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5.1.5. Insulators
The insulators are the materials which do not permit flow of electrons through it. Insulators are
resisting electric property. There are numerous types of insulators such as shackle, strain type,
suspension type, and stray type etc. Insulators are used in substations for avoiding contact with
humans or short circuit.

Fig.4 Insulators

5.1.6. Isolators
Electrical isolator which is commonly known as isolator or disconnector is a piece of equipment
that is used in electric devices and power systems with the main function of effectively isolating
two different parts of an instrument. By definition, isolation is the process of complete separation
of various parts of an apparatus and this separation can either be physical or electrical or both.
The main purpose of an isolator is safety because if a fault occurs in one section of a circuit
or power supply then electrical isolator is used as a switch to keep apart that section from other
sections of system to perform repair work. In a similar scenario, isolators also ensure safety of
workers in regular maintenance and service of the power system. Isolators separate a certain circuit
from the electricity mains and discharge any residual current, left in the circuit, to the ground.

15
 Fig.5 Isolators

5.1.7. Busbars
The busbar is among the most important elements of the substation and is a conductor which carries
current to a point having numerous connections with it. The busbar is a kind of electrical junction
which has outgoing and incoming current paths. Whenever a fault occurs in the busbar, entire
components connected to that specific section should be tripped for giving thorough isolation in a
small time, for instance, 60ms for avoiding danger rising due to conductor’s heat. These are of
different types such as ring bus, double bus, and single bus etc. A simple bus bar is shown in the
figure below which is considered as one of the most vital electrical substation components.

16
 Fig.6 Busbar

5.1.8 Lighting Arresters

The lightning arresters can be considered as the first ever components of a substation. These are
having a function of protecting equipment of substation from high voltages and are also limiting
the amplitude and duration of the current’s flow. These are connected amid earth and line i.e.
connected in line with equipment in the substation. These are meant for diversion of current to
earth if any current surge appears hence by protecting insulation as well as conductor from
damages. These are of various types and are distinguished based on duties.

The following are the damages that are caused by the travelling wave on the substation equipment.

1. The high peak or crest voltage of the surge may cause flash-over in the internal winding thereby
spoil the winding insulation.

2. The steep wave fronts of the surges may cause external flashover between the terminal of the
transformer.

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3. The highest peak voltage of the surge may cause external flashover, between the terminal of the
electrical equipment which may result in damage to the insulator.

Fig.7 Lightning Arrester

5.1.9 Circuit Breakers

The circuit breakers are such type of switches utilized for closing or opening circuits at the time
when a fault occurs within the system. The circuit breaker has 2 mobile contacts which are in OFF
condition in normal situations. At the time when any fault occurs in the system, a relay is sending
the tripped command to the circuit breaker which moves the contacts apart, hence avoiding any
damage to the circuitry.

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 Fig.8 Circuit Breaker
5.1.10 Relays
Relays are a dedicated component of electrical substation equipment for the protection of system
against abnormal situations e.g. faults. Relays are basically sensing gadgets which are devoted for
sensing faults and are determining its location as well as sending interruption message of tripped
command to the specific point of the circuit. A circuit breaker is falling apart its contacts after
getting the command from relays. These are protecting equipment from other damages as well
such as fire, the risk to human life, and removal of fault from a particular section of the substation.
Following is the substation component diagram is known as a relay.

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 Fig.9 Relay
5.1.11 Capacitor Bank
The capacitor bank is defined as a set of numerous identical capacitors which are connected either
in parallel or series inside an enclosure and are utilized for the correction of power factor as well
as protection of circuitry of the substation. These are acting like the source of reactive power and
are thus reducing phase difference amid current and voltage. These are increasing the capacity of
ripple current of supply and avoid unwanted selves in the substation system. The use of capacitor
banks is an economical technique for power factor maintenance and for correction of problems
related to power lag.

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 Fig. 10 Capacitor Bank

5.1.12 Batteries
Some of the important substation parts such as emergency lighting, relay system, and automated
control circuitry are operated through batteries. The size of the battery bank is depending on the
voltage required for operation of the DC circuit respectively. The storage batteries are of two basic
types i.e. acid-alkaline batteries and lead-acid batteries. The lead acid batteries are of the most
common type and used in substations in abundance as these provide high voltages and are cheaper
in cost.

21
 Fig. 11 Batteries
5.1.13 Wave Trapper
The wave trapper is one of the substation components which is placed on the incoming lines for
trapping of high-frequency waves. The high-frequency waves which are coming from nearby
substations or other localities are disturbing the current and voltages, hence its trapping is of great
importance. The wave trapper is basically tripping high-frequency waves and is then diverting the
waves into telecom panel.

22
 Fig. Wave Trapper
5.1.14 Switchyard

The switchyards, switches, circuit breakers, and transformers for the connection and disconnection
of transformers and circuit breakers. These are also having lighting arrestors to protect the
substation or power station from strokes of natural lighting.

Fig.12 Switchyard

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 6. PROTECTIONS USED IN SUBSTATION
Following are the main protections used in substation:

1. Distance protection.

2. Differential Protection

3. Overvoltage protection.

4. Overcurrent protection.

5. Earth fault protection.

6. Breaker lock-out protection.

6.1 Distance Protection

A distance protection compares the currents and voltages at the relaying point with current
providing the operating torque and the voltage provides the restraining torque. In other words, a
distance protection is a voltage restrained overcurrent relay.

The equation at the balance point in a simple impedance relay is K1V2 = K2I2 or V/I = K3 where
K1, K2 and K3 are constants. In other words, the relay is on the verge of operation at a constant
value of V/I ratio, which may be expressed as impedance.
Type of Distance Relay:

1. Impedance relay
2. Reactance relay
3. Mho relay
4. Modified impedance relay

6.2 Differential Protection

This protection scheme employs the principle of comparing the actuating quantities of both sides
of the protected system which is sensed by CTs installed on both sides, the quantities is compared

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and if difference found is large, it sends a signal to trip the breaker. The differential or error is
generated due to faults such as line-line, line to earth, double line to earth, three phases to ground
etc.

6.3 Overvoltage Protection

Over voltages in power network are caused because of two reasons- internal and external causes.
The causes of internal overvoltage’s are switching surges, insulation failure, arcing ground,
resonance. The causes of external overvoltage’s are lightning. For overvoltage protection
lightning arresters, visitors and suppression diodes are used. There is no ideal component that
could fulfill all the technical requirement of overvoltage protection equally effectively, therefore
to optimize the overvoltage protection carefully matched group of these components are often
combined in one protective module.

6.4 Overcurrent Protection

The over current protection is the simplest type of protection system. As the name implies, the
relay is designed to operate when more than a predetermined amount of current flows into a
particular portion of the power system.
There are two basic forms of over current relays: the instantaneous type and the time-delay type.
The instantaneous over current relay is designed to operate with no intentional time delay when
the current exceeds the relay setting. Nonetheless, the operating time of
This type of relay can vary significantly. It may be as low as 0.016 seconds or as high as 0.1
seconds.
The time-over current relay has an operating characteristic such that its operating time varies
inversely as the current flowing in the relay. The three most commonly used time-over current
characteristics: inverse, very inverse, and extremely inverse.

6.5 Breaker Lock Protection

All the protection operates to trip the circuit breaker so as to disconnect the faulty part of the
system. So, it is very necessary that the circuit breaker operate properly. In SF6 circuit breaker,
SF6 gas pressure is 8 bars. If this pressure reduces below 7.6 bar, then the circuit breaker
ceases to operate, and this is called breaker lockout protection

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6.6 Earth Fault Protection
Earth Faults are the most common faults in the Power system. When an Earth Fault occurs in a
three-phase transmission network, the current will not be balanced and there will be the residual
current flowing through the neutral wire the relay is designed to operate when more than a
predetermined amount of current flows in the neutral.

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 7. FINAL RESULT AND CONCLUSION
On completing this work on “Sub-Station Equipment operation and maintenance: A Case study
of 132/33 substation Palia Kalan. It can be concluded that; regular check and operation period
is an important managerial responsibility, as it helps in identifying the problems and quick
solution for them. Also, beside this following are the direct benefits to the company results came
forward:

 Reduction in breakdown of equipment and thus increase in availability.

 Fall in forced outage due to system failure.
 Reduction in numbers of standby modules and equipment.
 Stable and secure power supply.
 Improved profitability of company.

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 8. SCOPE OF FUTURE STUDY
To provide and maintain safe and reliable power, the knowledge of substation is of immense
important. There are many vital issues which have to be studied in detail for reducing the failures
to maintain secure power supply and safety of man power. Some of the issues are pointed here:

1. The study of earthing and to develop awareness for it.

2. Study of maintenance planning so that break down time is reduced.
3. The study about safe working practices.
4. More and more emphasis should be on automation.

Finally, it is necessary to encourage everybody to safe utilization of power and save power as this
work suggests that, “Maintenance is a key to Energy Conservation”.

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