Summer training report

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MALAVIYA NATIONALINSTITUTE OF TECHNOLOGY,
JAIPUR
A REPORT ON INDUSTRIAL TRAINING
ON
(SWITCHGEAR & PROTECTION SYSTEM)
AT
220kV GSS Kotputli
Jaipur
Under the guidance of
Mr. Subhash Meena
(A.En., RRVPNL)
Submittedby:-
SUNILKUMARYADAV
2013UEE1176
Batch-E1
Submittedto:-
Dr. Nitin Gupta
Dr. SatyanarayanaNeeli
Dept. of ElectricalEngineering

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Acknowledgement
This report is an outcome of the contributions made by some of the
peoples. Therefore, it is my sole responsibility to acknowledge them. I am
greatly thankful to the sincere efforts made by Mr. M.P. BADGUJAR,
X.En. (GSS, Kotputli) without whom this project would be abstract. I also
thank the staff of 220kV Grid Transmission Substation, Kotputli-Jaipur
who took out their precious time to tell me about the various equipments.
My special thanks is dedicated to Mr. Subhash Meena, A.En.
(maintenance).
SUNIL KUMAR YADAV
B. Tech (7th Sem)
Electrical Engineering
MALAVIYA NATIONAL INSTITUTE OF TECHNOLOGY
JAIPUR (RAJASTHAN)

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DECLARATION
I hereby declare that this Industrial Training Report entitled ("switchgear
and protection systems") is an authentic record of my own work as
requirements of 45 days Industrial for the award of degree of B.Tech
(Electrical Engineering), MNIT Jaipur.
(Signature of student)
(Name of Student)
(Registration Number)
Date: 19 September,2016

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ABSTRACT
Training at 220 KV GSS Kotputli, Jaipur gives the insight of the real instruments
used. There are many instruments like transformer, CT, PT, CVT, LA, relay, PLCC,
bus bars, reactors, insulator, isolators, controlroom, etc. There are various problems
seen in substation while handling these instruments. There are various occasion
when relay operate and circuit breaker open, load shedding, shut down of a feeder
in case of a fault , shutdown of total system, overheating of transformer, blasting of
current transformer in case of excessive current, transformer oil replacement, aging
of transformer oil, wireless communication, insulator classification as per current
rating, conductor requirement as per rating ,2 line and 3 line transmission, how to
put system on load and how to remove the system from load, automatic resetting of
relay, isolator operation on off-load.
GSS is the mean of connection between generating station and consumer by
providing safety and reliability of system in case of fault. This sub-station step
down the incoming voltage power transmission to the required value and then is
supplied to the consumer feeder or GSS done by connecting auto transformer
operation and requirement of various equipment have been include in detail, further
in case of report is the bus bar. Arrangement of different feeder level and switch
yards included information of bus bar arrangement of different level isolator and
growing substation also power transformer circuit breaker oil, filtration plant, and
compression protection control room and place are leveled.
The most important part of a G.S.S. is the battery roomor most commonly known
as the heart ofa G.S.S. without the battery systemall the controlpanel, metering and
relay panel will not operate and therefore it will lead to failure of substation. As the
most important part of a GSS is battery room as controlpanel operate on this supply
it must be kept in spare as we have 220V DC supply and each battery supplies 2
volts hence 110 batteries will be kept in parallel to supply the same, hence always a
backup of 110 batteries are always kept in storage room
Relay system is termed as the brain of the G.S.S. as it controls the circuit breaker
operations as it is very necessary to operate the circuit break operation in time, we
can take our time for closing on the circuit breaker but during fault circuit breaker
must be operated as soon as possible and arc must be quenched accordingly.
To get insight ofthe substation, how things operate, how things are managed inside
a substation. Practical training as a whole proved to be extremely informative and
experience building and the things I learned here would definitely help a lot in
snapping the future ahead in a better way.

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OBJECTIVE
As a part of the engineering course curriculum every student has to go through a
minimum 45 days practical training from a premiere national level institute, this
training gives a chance to the student to really see how things are done practically
and how the problems are managed.
I decided to complete my training at 220 KV GSS, KOTPUTLI. As I am interested
in switchgear and protection systems a place better than G.S.S. could not have been
found.
My objective of training was to see how the equipment work in a proper manner,
how load is distributed, how power factor of system is improved, how fault is
measured with the help of megger(i.e. the potential difference between two lines) ,
how current transformers are installed , how logs are maintained, in what manner
earthing & protection system are installed, how cooling systems are operated.
Capacitor banks are really important in a substation as they help in improving the
power factor hence improving the voltage level in a system, because they supply
locally reactive power to the systemand hence help in maintaining the tariff in limit.
As we all know that at a HV SUBSTATION we have assisting supplies also such a
motors and other loads also so to supply these we have an arrangement of stepping
down the voltage, this arrangement is really fascinating to me, to see this
arrangement was one of the main objective of the training.
As the most expensive and most important part of a substation is Transformer, so I
was really interested in seeing how the protection systems for transformers are
installed.
As the protection system includes C.T., RELAY & C.B., it was really important to
see the functioning of these instruments in co-ordination with each other.
While dealing with such equipments and at such a high voltage there is always a
possibility of accidental fires and water cannot be used to extinguish fire as current
is there in line, so fire extinguishing arrangement at a substation is really important
and I really wanted to see the extinguishing system.

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INTRODUCTION
The "220 KV.GSS, RVPN Ltd. is ideally located at the KOTPUTLI, JAIPUR. GSS
is the medium of connection between generating station and consumers (Traction,
Industrial & Domestic etc.) by providing safety and reliability of whole system in
case of fault.
Steps of this sub-station are:- to step down the incoming voltage of power
transmission to a required value i.e. 220 KV to 132 KV, 132 KV to 33KV and then
supply to consumer's feeders of GSS done by connecting auto-transformer.
Operation requirement of various equipments have been included in detailed
manner further in report. There is one incoming line from ALWAR sub-station.
There are two 4 different outgoing line of 132kV, next we have 8 line of 33kV
outgoing feeder namely :
1. 33 kV PAOTA
2. 33 kV PANIYALA
3. 33 kV PANASIEA
4. 33 kV PATTAN CHALLA
5. 33 kV KOTPUTLI
6. 33 kV BEHROR II
7. 33 kV S. CEMENT
8. 33 kV PUTLI
We have 132 kV outgoing line to 4 different locations as:
1. 132 kV BEHROR
2. 132 kV NEEM KA THANA
3. 132 kV BANSUR
4. 132 kV SHAHPURA

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INTRODUCTION OF RRVPNL
When India becomes independent its overall installed capacity was hardly 1900
MW. During first year plan (1951-1956) this capacity was only 2300 MW. The
contribution of Rajasthan state was negligible during 1&2 year plans & the
emphasis was on industrialization for that end it was considered to make the system
of the country reliable. Therefore, Rajasthan state electricity board came into
existence in July 1957.In India electrical power is generated at a voltage of 11KV
to 33 KV which is stepped up to the transmission level in the range of 66 KV to 400
KV. For transmitting power member of transmission and switching have to be
created. These are known as “SUB STATION”.
Along these transmission lines secondary substations are created where voltage is
further stepped down to sub transmission and primary distribution voltage.
A substation is an assembly of apparatus, which transform the characteristics of
electrical energy from one form to another say from one voltage level to another
level. Hence a substation is an intermediate link between the generating station and
consumer.
For economic transmission the voltage should be high so it is necessary to step up
the generated voltage for transmission and step down transmitted voltage for
distribution. For this purpose, substations are installed. The normal voltages for
transmission are 400kv, 220kv, 132kv and for distribution 33kv, 11kv etc.
Electricity boards are setup in all states of India which are responsible for
1.Generation
2.Transmission
3.Distribution

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They also construct, install and maintain all the station made for these purpose.
In Rajasthan, R.R.V.P.N.L. is responsible for transmission and distribution of
electrical power all over Rajasthan. It has its own generating station and it’s also
gets power from various other stations also. It gets power from following stations:-
1. Badarpur
2. Bhakara Nangal Project (at sutlaj in Punjab)
3. Gandhi Sagar Dam Kota
4. Jawahar Dam Kota
5. Rana Pratap Sagar Dam Kota
6. Rajasthan Atomic Power Plant (RAPP) Kota
7. Kota Super Thermal Power Station (KSTPS) Kota
8. Anta Gas Power Plant Anta
9. Rajasthan share in Bhakara Beas Management Board (BBMB)
Power obtain from these stations is transmitted all over Rajasthan with the help of
grid stations. Depending on the purpose, substations may be classified as:-
1. Step up substation
2. Primary grid substation
3. Secondary substation

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FUNCTIONS/ PROCESSES/ WORK DONE AT THE 220
KV GSS:
1.1 SUB STATION:
Electrical networks comprise the following region:
• GENERATING STATIONS
• TRANSMISSION SYSTEM
• RECEVING STATIONS
• DISTRIBUTUION SYSTEM
• LOAD POINTS
In all these regions, the power flow from generation station to final load point
takes place through electrical substation. A substation receives electrical power
from generating station via transformer incoming lines and delivers electrical
power via the outgoing transmission lines. A substation is an assembly of
electrical component including bus bars, switching, power transformer and
auxiliaries. Basically an electrical substation consists of number of incoming and
outgoing circuit connected to a common bus bar system. Bus bars are conducting
bars to which a no. of incoming and outgoing circuit are connected.
1.2 AN ELECTRICAL AUTHORITY AIMS AT THE
FOLLOWING:
1. Supply of electrical power to all the consumers continuously at all times.
2. Max coverage of the supply network over the given geographical area.
3. Max reliability of supply.
4.Minimum operation time of circuit breaker in fault duration.
5.Optimum efficiency of plants and the networks.
6.Supply of electrical power within specified voltage limits.
7.Supply of electrical energy to the consumers at the lowest cost.

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1.3 THE TASK ARISES WITH THE MAJOR SUB STATION IN
THE TRANSMISSION AND DISTRIBUTION SYSTEMS ARE AS
FOLLOW :-
- Protection of transmission system
- Controlling the exchange of energy
- Ensuring the steady state and transient stability
- Load shedding and prevention of loss of synchronism maintaining the system
frequency within targeted limits.
- Voltages control, reducing the reactive power and tap changing
- Providing the adequate line capacity and facility for changing the transmission
paths
- Data transmission via power line carrier for the purpose of network monitoring,
controls and protection
- Determination the energy transfer through transmission lines and tie lines.
- Fault analysis and pin pointing the cause and subsequent improvement
- Established economic load distribution.

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1.4 POWER SYSTEM DESIGN
In the power system design the following aspects have to be considered and studied
carefully.
(1) Land data, magnitude of rate of growth, Design of power station with details of
Equipment parts.
(2) Design of transmission lines and networks in the system for necessary load
transmission over a given distance with technical limitation and required
characteristics.
(3) Design of interconnections in the system.
(4) Design of distribution system.
(5) Choice ofvoltage, system controlincluding voltage control, controlofactive and
reactive Load, system losses.
(6) Line compensation. System satiability studies and reliability studies.
(7) Bus - Bar arrangement.
(8) Power system protection, protection against fault protection against lighting.
1.5 E. H. V SUBSTATION DESIGN
(1) Types of substation and their classification.
(2) Choice of layouts & key diagrams.
(3) Selection of bus bar arrangements.
(4) Choice of BIL of equipment & main technical parameters, insulation cord.
(5) Selection of safety clearance.
(6) Design of ear thing system.
(7) Design of overhead shielding.
(8) Design of illumination system.
(9) Design of D.C supply.
(10) Design of fire protection.
(11) Design of communication system.
(12) Gas insulated substation.
(13) Design & selection of protective relaying system.
(14) Problems of operation & maintenance.

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1.6 FOLLOWING ESSENTIAL EQUIPMENT:-
1.0 Main bus
2.0 Auxiliary bus
3.0 Insulators
4.0 Protective Relays
5.0 Circuit Breaker
6.0 Isolators
7.0 Power Transformers
8.0 Current Transformers
9.0 Potential Transformers
10.0 Lightning Arrestors
11.0 Relay and metering panels
12.0 Color Coding
13.0 Shunt capacitors and shunt reactors
14.0 Bus Coupler
15.0 Disturbance Recorder
16.0 Event Logger
17.0 On Load Tap Changer
18.0 No Load Tap Changer
19.0 Synchronoscope
As all the important and available equipment at the 220kv GSS are mentioned
above, explanation of each of the instrument available at the GSS are explained in
detailed and lucrative manner below:
2.0 BUS BARS
Bus Bars are the common electrical componentthrough which a large no of feeders
operating at same voltage have to be connected. If the bus bars are of rigid type
(Aluminum types) the structure height are low and minimum clearance is required.
While in case of strain type of bus bars suitable ACSR(aluminum conductor steel
reinforced) conductorare strung/tensioned by tension insulators discs according to

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system voltages. In the widely used strain type bus bars stringing tension is about
500-900 Kg depending upon the size of conductor used. Here proper clearance
would be achieved only if require tension is achieved. Loose bus bars would affect
the clearances when it swings while over tensioning may damage insulators. Even
the Clamps affect the supporting structures in low temperature conditions. The
clamping should be proper, as loose clamp would spark under in full load condition
damaging the bus bars itself. At 220 kV GSS Kotputli we have 2 main bus bars of
220 kv main bus-1 and main bus-2 ,also we have one auxiliary bus bar of 220 kv in
case of failure of one of the bus bar it can supply power hence increasing the
reliability of the system, apart from 220 kv bus bar we have one main bus bar of
132 kv namely main bus 1 and auxiliary bus of 132kv.
Various voltage levels and the suitable conductors used forthem at the 220 kv GSS
are mentioned below:
220 kV Main Bus : Quadruple / Twin ACSR Zebra / Twin AAC Tarantulla
220 kV Auxiliary Bus : ACSR Zebra
220 kV equipment interconnection : Twin ACSR Zebra / Single ACSR Zebra
220 kV overhead bus & droppers in all bays : Twin ACSR Zebra / Single ACSR Zebra
132 kV Main Bus : ACSR Zebra
132 kV Auxiliary Bus : ACSR Panther
132 kV equipment inter connection : ACSR Zebra / ACSR Panther
132 kV overhead bus & droppers in all bays : ACSR Panther
33 kV Main Bus ACSR Zebra
33 kV Auxiliary Bus ACSR Zebra

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3.0 INSULATOR
The insulator for the overhead lines provides insulation to the power conductors
from the ground so that currents from conductors do not flow to earth through
supports. The insulators are connected to the cross arm of supporting structure and
the power conductor passes through the clamp of the insulator. The insulators
provide necessary insulation between line conductors and supports and thus prevent
any leakage current from conductors to earth. In general, the insulator should have
the following desirable properties:
• High mechanical strength in orderto withstand conductorload, wind load etc.
• High electrical resistance of insulator material in order to avoid leakage
currents to earth.
• High relative permittivity ofinsulator material in orderthat dielectric strength
is high.
• High ratio of puncture strength to flash over.
These insulators are generally made of glazed porcelain or toughened glass. Poly
come type insulator [solid core] are also being supplied in place of hast insulators
if available indigenously. The design of the insulator is such that the stress due to
contraction and expansion in any part of the insulator does not lead to any defect. It
is desirable not to allow porcelain to come in direct contact with a hard metal screw
thread.
Fig 1. Insulator

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4.0 PROTECTIVE RELAYS
Relays must be able to evaluate a wide variety of parameters to establish that
corrective action is required. Obviously, a relay cannot prevent the fault. Its primary
purposeis to detect the fault and take the necessary action to minimize the damage
to the equipment or to the system. The most common parameters which reflect the
presence of a fault are the voltages and currents at the terminals of the protected
apparatus orat the appropriate zone boundaries. The fundamental problem in power
system protection is to define the quantities that can differentiate between normal
and abnormal conditions. This problem is compounded by the fact that “normal” in
the present sense means outside the zone of protection. This aspect, which is of the
greatest significance in designing a secure relaying system, dominates the design of
all protection systems.
Fig 2. Relay Panel

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5.0 CIRCUIT BREAKER
The function of relays and circuit breakers in the operation of a power system is to
prevent or limit damage during faults or overloads, and to minimize their effect on
the remainder of the system. This is accomplished by dividing the system into
protective zones separated by circuit breakers. During a fault, the zone which
includes the faulted apparatus is de-energized and disconnected from the system. In
addition to its protective function, a circuit breaker is also used for circuit switching
under normal conditions.
Each having its protective relays fordetermining the existence ofa fault in that zone
and having circuit breakers for disconnecting that zone from the system. It is
desirable to restrict the amount of system disconnected by a given fault; as for
example to a single transformer, line section, machine, or bus section. However,
economic considerations frequently limit the number of circuit breakers to those
required for normal operation and some compromises result in the relay protection.
Some of the manufacturers are ABB, AREVA, Cutler-Hammer (Eaton), and
Mitsubishi Electric,
Pennsylvania Breaker, Schneider Electric, Siemens, Toshiba, Končar HVS and
others.
Circuit breaker can be classified as "live tank", where the enclosure that contains
the breaking mechanism is at line potential, or dead tankwith the enclosure at earth
potential. High-voltage AC circuit breakers are routinely available with ratings up
to 765,000 volts.

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6.0 ISOLATORS
“Isolator" is one, which can break and make an electric circuit in no load
condition. These are normally used in various circuits for the purposes of Isolation
of a certain portion when required for maintenance etc. Isolation of a certain portion
when required for maintenance etc. "Switching Isolators" are capable of:
• Interrupting transformer magnetized currents
• Interrupting line charging current
• Load transfer switching
Its main application is in connection with transformer feeder as this unit makes it
possible to switch out one transformer, while the other is still on load. The most
common type of isolators is the rotating Centre pots type in which each phase has
three insulator post, with the outer posts carrying fixed contacts and connections
while the Centre posthaving contactarm which is arranged to move through 90` on
its axis.
Fig 3. Circuit Breaker

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The following interlocks are provided with isolator:
a) Bus 1 and2 isolators cannot be closed simultaneously.
b) Isolator cannot operate unless the breaker is open.
c) Only one bay can be taken on bypass bus.
d) No isolator can operate when corresponding earth switch is on breaker.
Fig.4 Isolator
7.0 POWER TRANSFORMER
Distribution transformers reduce the voltage of the primary circuit to the voltage
required by customers. This voltage varies and is usually:
• 120/240 volts single phase for residential customers
• 480Y/277 or 208Y/120 for commercial or light industry customers.
• We have three transformers of total capacity 250 MVA namely:
1. BHEL transformer of 100 MVA capacity and 220/132kv
2. TELK transformer of 100 MVA capacity and 220/132kv.
Along with these transformers of 220/132 kv we have two more transformers of
132/33 kv capacity namely:
1.BBL transformer of 25 MVA capacity
2.TELK transformer of 25 MVA capacity

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Three-phase pad mounted transformers are used with an underground primary
circuit and three single phase pole type transformers for overhead service.
Network service can be provided for areas with large concentrations of businesses.
These are usually transformers installed in an underground vault. Power is then sent
via underground cables to the separate customers.
Parts of Transformer: -
7.1 Windings:
Winding shall be of electrolytic grade copper free from scales & burrs. Windings
shall be made in dust proof and conditioned atmosphere. Coils shall be insulated
that impulse and power frequency voltage stresses are minimum. Coils assembly
shall be suitably supported between adjacent sections by insulating spacers and
barriers. Bracing and other insulation used in assembly of the winding shall be
arranged to ensure a free circulation of the oil and to reduce the hot spot of the
winding. All windings of the transformers having voltage less than 66 kV shall be
fully insulated. Tapping shall be so arranged as to preserve the magnetic balance of
the transformer at all voltage ratio. All leads from the windings to the terminal
board and bushing shall be rigidly supported to prevent injury from vibration short
circuit stresses.

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Fig.5 Power Transformer
7.2 Tanks and fittings:
Tank shall be of welded construction & fabricated from tested quality low carbon
steel of adequate thickness. After completion of welding, all joints shall be
subjected to dye penetration testing.
At least two adequately sized inspection openings one at each end of the tank shall
be provided for easy access to bushing & earth connections. Turrets & other parts
surrounding the conductorofindividual phaseshall benon-magnetic. The main tank
body including tap changing compartment, radiators shall be capable of
withstanding full vacuum.
7.3 Cooling Equipment:
Cooling equipment shall conform to the requirement stipulated below:
7.3.1 Each radiator bank shall have its own cooling fans, shut off valves at the top
and bottom (80mm size) lifting lugs, top and bottom oil filling valves, air release
plug at the top, a drain and sampling valve and thermometer pocket fitted with
captive screw cap on the inlet and outlet.

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7.3.2 Cooling fans shall not be directly mounted on radiator bank which may cause
undue vibration. These shall be located so as to prevent ingress of rain water. Each
fan shall be suitably protected by galvanized wire guard.
7.4 Temperature Indicators:
Most of the transformer (small transformers have only OTI) are provided with
indicators that displace oil temperature and winding temperature. There are
thermometers pockets provided in the tank top cover which hold the sensing bulls
in them. Oil temperature measured is that of the top oil, whereas the winding
temperature measurement is indirect
Fig.(6.1) OTI(temperature meter)

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7.5 Silica Gel Breather:
Both transformer oil and cellulosic paperare highly hygroscopic. Paperbeing more
hygroscopic than the mineral oil The moisture, if not excluded from the oil surface
in conservator, thus will find its way finally into the paper insulation and causes
reduction insulation strength of transformer. To minimize this conservator is
allowed to breathe only through the silica gel column, which absorbs the moisture
in air before it enters the conservator air surface.
Fig.(6.2) Silica Gel Breather
8.0 CURRENT TRANSFORMER
As you all know this is the device which provides the pre-decoded fraction of the
primary current passing through the line/bus main circuit. Such as primary current
60A, 75A, 150A, 240A, 300A, 400A, to the secondary output of 1A to 5A.
When connecting the jumpers, mostly secondary connections is taken to three
unction boxes where star delta formation is connected forthree phase and final leads
taken to protection /metering scheme.

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Fig.7. Current Transformers
It can be used to supply information for measuring power flows and the electrical
inputs for the operation of protective relays associated with the transmission and
distribution circuit or for power transformer. These current transformers have the
primary winding connected in series with the conductor carrying the current to be
measured or controlled. The secondary winding is thus insulated from the high
voltage and can then be connected to low voltage metering circuits.

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9.0 POTENTIAL TRANSFORMER
A potential transformer (PT) is used to transform the high voltage of a power line
to a lower value, which is in the range of an ac voltmeter or the potential coil of an
ac voltmeter.
The voltage transformers are classified
as under:
 Capacitive voltage transformer or
capacitive type
 Electromagnetic type.
Capacitive voltage transformer is being used more and more for voltage
measurement in high voltage transmission network, particularly for systems voltage
of 132KV and above where it becomes increasingly more economical. It enables
measurement of the line to earth voltage to be made with simultaneous provision
for carrier frequency coupling, which has reached wide application in modern high
voltage network for tele metering remote control and telephone communication
purpose.
10.0LIGHTNING ARRESTOR
A lightning arrester (in Europe: surge arrester)is a device used on powersystems
and telecommunications systems to protect the insulation and conductors of the
system from the damaging effects of lightning. The typical lightning arrester has a
high-voltage terminal and a ground terminal. When a lightning surge (or switching
surge, which is very similar) travels along the power line to the arrester, the current
from the surge is diverted through the arrestor, in most cases to earth.
In telegraphy and telephony, a lightning arrestor is placed where wires enter a
structure, preventing damage to electronic instruments within and ensuring the
safety of individuals near them. Smaller versions of lightning arresters, also called

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surge protectors, are devices that are connected between each electrical conductor
in power and communications systems and the Earth. These prevent the flow of the
normal power or signal currents to ground, but provide a path over which high-
voltage lightning current flows, bypassing the connected equipment. Their purpose
is to limit the rise in voltage when a communications or power line is struck by
lightning or is near to a lightning strike.
If protection fails or is absent, lightning that strikes the electrical system introduces
thousands of kilovolts that may damage the transmission lines, and can also cause
severe damage to transformers and other electrical or electronic devices. Lightning-
produced extreme voltage spikes in incoming power lines can damage electrical
home appliances.
Potential target for a lightning strike, suchas a television antenna, is attached to the
terminal labeled A in the photograph. Terminal E is attached to a long rod buried in
the ground. Ordinarily no current will flow between the antenna and the ground
because there is extremely high resistance between B and C, and also between C
and D. The voltage of a lightning strike, however, is many times higher than that
needed to move electrons through the two air gaps. The result is that electrons go
through the lightning arrester rather than traveling on to the television set and
destroying it.
A lightning arrester may be a spark gap or may have a block of a semi conducting
material such as silicon carbide or zinc oxide. Some spark gaps are open to the air,
but most modern varieties are filled with a precision gas mixture, and have a small
amount of radioactive material to encourage the gas to ionize when the voltage
across the gap reaches a specified level. Other designs of lightning arresters use a
glow-discharge tube (essentially like a neon glow lamp) connected between the
protected conductor and ground, or voltage-activated solid-state switches called
varistors or MOVs.
Lightning arresters built for power substationuse are impressive devices, consisting
of a porcelain tube several feet long and several inches in diameter, typically filled
with disks of zinc oxide. A safety porton the side of the device vents the occasional
internal explosion without shattering the porcelain cylinder.

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Lightning arresters are rated by the peak current they can withstand, the amount of
energy they can absorb, and the break over voltage that they require to begin
conduction. They are applied as part of a lightning protection system, in
combination with air terminals and bonding.
220 kV LIGHTNING ARRESTOR:
Manufacture: English electric company
No. of phase: One
Rated voltage: 360 kV
Nominal discharge current: (8×20µs) 10 kA
High current impulse: (4× 100µs) 100 kA
Long distribution rating: (200µs) 500 kA
Fig.8 Lightening Arrester on pole

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11.0 CONTROL PANEL
Control panel contain meters, control switches and recorders located in the control
building, also called the dog house. These are used to control the substation
equipment to send power from one circuit to another or to open or to shut down
circuits when needed.
Fig 9. 220 KV GSS Kotputli Control Panel

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12.0 COLOUR CODING
* 33KV GREEN
* 132 KV BLACK
* 220KV BROWN
* 440 VOLTS VOILET/INDIGO
* 110 VOLTS ORANGE
13.0 REACTOR
It is used to lower the over excited capacitor. Capacitor bank is connected in shunt
over the reactor. Capacitors main purposeis to boostup the voltage. so when we
want to lower the voltage we use reactors. it is also use to stop the suddenchange.
the commonly used reactor is NGR(Neutral ground reactor).
14.0 BUS COUPLERS
It is used to equalize the load on both Bus bars.
15.0 DISTURBANCE RECORDER
It records the distance & fault on graph with voltage w.r.t time.

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16.0 EVENT LOGGER
It monitors as well as provides the details as a printed material.
These details may contain the sequence of operation, switching time, closing time
etc.
17.0 ON LOAD TAP CHANGER (OLTC)
In this method a number oftapings are provided onthe secondaryof the transformer.
The voltage drop in the line is supplied by changing the secondary emf of the
transformer through the adjustment of its number of turns by using transition
resistor which is placed in between each tapping.
Fig.10. Tap Changer

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18.0 NO LOAD TAP CHANGER (NLTC)
In this we change the tap manually for which we have to shut downthe transformer.
When the load increases the voltage across the primary drops but the secondary
voltage can be kept at the previous value by placing the movable arm on to a higher
stud. Whenever a tapping is to be changed in this type of transformer, the load is
kept off and hence the name off load tap-changing transformer.
19.0 SYNCHRONOSCOPE
A synchronoscope is used to determine the correct instance of closing the switch
with connect the new supply to bus bar the correct instance of synchronizing is
indicated when bus bar and incoming voltage
* are equal in magnitude
* are equal in phase
* have the same frequency

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SUMMARY AND GAINS FROM THE TRAINING
A technician needs to have not just theoretical but practical as well and so every
student is supposed to undergo practical training sessionafter 3rd year where I have
imbibed the knowledge about transmission, distribution, generation and
maintenance with economical issues related to it. During our 45 days training
session we were acquainted with the repairing of the transformers and also the
testing of oil which is a major component of transformer. At last I would like to say
that practical training taken at 220 kV GSS has broadened my knowledge and
widened my thinking as a professional.

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REFERENCES
 BOOKS:
[1] “A Course In Power Systems” by J.B. GUPTA(11th edition)
[2] “Modern Power System Analysis” by D.P. KOTHARI & I.J.
NAGRATH(4th edition)
 ONLINE SOURCES
• http://www.alfredkim.co.in/bangalore/lightning-arrestor.html
• RVPNL HOME SITE :
• http://www.rvpn.co.in/aboutus/amis.shtml
• GATHERINGS DURING THE TRAINING PERIOD IN 220 KV G.S.S.
• Wikipedia
• REPORTS:
• Constructional manual of 220 kV GSS Kotputli(revised in 2008)