SCHOOL OF

ELECTRICAL, ELECTRONICS & COMMUNICATION (SEEC) ENGG MANIPAL UNIVERSITY JAIPUR, JAIPUR – 303007, RAJASTHAN, INDIA

INDUSTRIAL TRAINING REPORT SWITCHGEAR & PROTECTION SYSTEM

Submitted By Name: ROHITASHAV GOYAL

Registration Number: 110106002

Under the Guidance of

Mr. Harish Varmar

Executive Engineer, RRVPNL

AND

Mr. Ritesh Singh

Assistant Professor, EEE

Manipal University Jaipur

ABSTRACT

Training at 220 KV GSS Hindaun City, Karauli 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, control room, 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 room or most commonly known as the heart of a G.S.S.

without the battery system all the control panel, 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 control panel

operate on this supply it must be kept in spare as we have 220V DC supply ,and each battery supplies 2

volt 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 of the 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.

DECLARATION

I hereby declare that the 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 & Electronics Engineering), Manipal University Jaipur.

(Signature of student)

(Name of Student)

(Registration Number)

Date: ____________________

Certified that the above statement made by the student is correct to the best of our knowledge and belief.

Signatures

Examined by:

1. 2. 3. 4.

Certified that the above statement made by the student is correct to the best of our knowledge and

belief.

Head of Department

ACKNOWLEDGMENTS

I would like to express my profound gratitude to our Dean Dr. Kumkum Garg for extending

her support in all endeavors.

I would like to thank Prof. Shravan Kumar Jhajharia,(H.O.D) electrical and electronics

Department for his guidance and encouragement throughout my academic career and

My department guide associate professor Mr. Ritesh Singh.

I express deep sense of gratitude to Mr. Harish Varmar(Exen.), 220 KV G.S.S, Hindaun City,

Karauli, Mr. J.K. Jain (Assistant engineer) Mr. Ashutosh Bhardawaj(Jen), Mr. Malik and other staff

Members at sub-station for their guidance and co-operation during my training period.

I would also like to express my profund gratitude to the T&P cell and also to Dr. Nidhi Singhal(training

&placement cell coordinator) for extending her support for the recommendation letter.

INTRODUCTION

The "220 KV.GSS, RVPN Ltd. is ideally located at the HINDAUN CITY. 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 are 3 incoming line from 2 different sub-station. One line of 220KV

coming from DAUSA(Lilo siki-aye), second line & third line (D/C) of 220 KV GUDAPOLE coming

from 400KV GSS HINDAUN.

There are two different outgoing traction line of 132kv for railways, next we have eight 33kv outgoing

feeder namely :

1. 33 kv Gudapole

2. 33 kv RICCO(R)

3. 33 kv Mahu

4. 33 kv Khera

5. 33 kv RICCO(I)

6. 33 kv Jat Ki Saray

7. 33 kv Hindaun

8. 33 kv Suroth

We have 132 kv outgoing line to 6 different locations as:

1.132 kv Todabhim

2.132 kv Shri Mahaveer Ji

3.132 kv Gangapur

4. 132 kv Karauli

5.132 kv Weir

6.132 kv Baseri

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 substation 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

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

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,HINDAUN CITY.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 system and

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 reaaly wanted to see the extinguishing system.

FUNCTIONS/ PROCESSES/ WORK DONE AT THE 220 KV GSS:

1.1 SUB STATION :-

Electrical networks comprises 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.

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 pwr 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.

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 of voltage, system control including voltage control, control of active 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.

1.6 FOLLOWING ESSENTIAL EQUIPMENT :-

2.0 Main bus and auxiliary bus

3.0 Insulsators

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 Colour 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 component through 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(aluminium conductor steel reinforced) conductor are strung/tensioned by tension insulators discs

according to 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 hindaun city we have 2 main bus bars of 220kv main bus-1 and main bus2 ,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 for them 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

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 order to withstand conductor load, wind load etc.

High electrical resistance of insulator material in order to avoid leakage currents to earth.

High relative permittivity of insulator material in order that 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)

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 purpose is 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 or at 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.

Fig2 relay panel

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 for determining the existence of a 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 tank with the enclosure at earth potential. High-voltage AC circuit breakers are

routinely available with ratings up to 765,000 volts.

Fig 3(Circuit Breaker)

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 post having contact arm which is arranged to move through 90` on its axis.

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 50 MVA capacity and 220/132kv

2. GEC transformer of 100 MVA capacity and 220/132kv

3. TELK transformer of 100 MVA capacity and 220/132kv.

Along with these transformers of 220/132 kv we have three more transformers of 132/33 kv capacity

namely:

1.IMP transformer of 25 MVA capacity

2.GEC transformer of 25 MVA capacity

3.BHEL transformer of 12.5 MVA capacity

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.

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 conductor of individual

phase shall be non-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.

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, where as the winding

temperature measurement is indirect

Fig.(5.1) OTI(temperature meter)

.

7.5 Silica Gel Breather:

Both transformer oil and cellulosic paper are highly hygroscopic. Paper being 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.(5.2) 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 for three phase and final leads taken to protection /metering scheme.

Fig.6-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.

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.

10.0 LIGHTNING ARRESTOR

A lightning arrester (in Europe: surge arrester) is a device used on power systems

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 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, such as 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 substation use 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 port on

the side of the device vents the occasional internal explosion without shattering the porcelain cylinder.

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.7 Lightening Arrester on pole

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 8 ACDB 220 KV GSS HINDAUN CITY

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 purpose is to boost up the voltage. so when we want to lower the voltage we use reactors.

it is also use to stop the sudden change. 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.

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 of tapings are provided on the secondary of 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.9 tap changer

18.0 NO LOAD TAP CHANGER (NLTC)

In this we change the tap manually for which we have to shut down the 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

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 session after 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.

REFERENCES

BOOKS: [1] “A Course In Power Systems” by J.B. GUPTA(11

th edition)

[2] “Modern Power System Analysis” by D.P. KOTHARI & I.J. NAGRATH(4th

edition)

ONLINE SOURCES

http://www.it.iitb.ac.in/~abhisheka/btp/BTech_Project_Report.doc

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.

REPORTS:

Constructional manual of 220 kv GSS Hindaun city(revised in 2008)