1. INTRODUCTION

220 KV GRID is located in Devigarh, Patiala .The grid receives 220 KV lines and steps down

further into 66 KV and 11 KV lines .The 66KV Grid was setup in the year 1973 and it is

modified to 220KV up to Feb 2014The various components used for stepping down the

voltage and protection are installed in the grid like transformers , circuit breakers, relays ,

current transformers ,potential transformers ,battery bank, busbar, lightning arrestor ,

insulators ,capacitor banks and various other sensors and devices.

Incoming Feeder:-

220KV Bhateri(Bhadurgarh)

Outgoing Feeder:-

66 KV

1. Bhunerheri

2. Magar Sahib

3. Rohar Jagir

11 K.V.

1. Jhawalapur 10. S.S.Wala

2. Mehon 11. Dudhan

3. Bangra 12. UPS-01

4. Kisanpur 13. UPS-02

5. Partapgarh 14. UPS-03

6. Hasanpur 15. Binjal

7. Masingan 16. Julkhan

8. Shekhupur 17. Gagrola

9. Bhunerheri 18. Waliyan

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NEED OF PROJECT WORK

The project entitled “STUDY OF VARIOUS COMPONENTS USED IN 220 KV

DEVIGARH GRID AND PROTECTION ,MAITENANCE OF POWER TRANSFORMER”

was carried out to have deep and sound knowledge of what are the various components used

in the grid , how are the various components installed , what is the use of the various

components , how do these components work etc . It also gave a knowledge of how the

power transformer operate, its protection, maintenance and lot of other things related to

transformer. This project made me aware of all these things.

Our main purpose for this visit is to be familiar with industrial environment and to get

practical knowledge of electrical power transmission and distribution Students of 3rd

semester will get the idea of electrical power transmission and distribution.

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2. SUBSTATION

An electrical sub-station is an assemblage of electrical components including busbars,

switchgear, power transformers, auxiliaries etc.

These components are connected in a definite sequence such that a circuit can be switched off

during normal operation by manual command and also automatically during abnormal

conditions such as short-circuit. Basically an electrical substation consists of No. of incoming

circuits and outgoing circuits connected to a common Bus-bar systems. A substation receives

electrical power from generating station via incoming transmission lines and delivers elect.

power via the outgoing transmission lines.

Sub-station are integral parts of a power system and form important links between the

generating station, transmission systems, distribution systems and the load points.

Fig 2.1 Graphical view of 220 KV Grid

MAIN TASKS

Associated with major sub-stations in the transmission and distribution system include the

following:

1. Protection of transmission system.

2. Controlling the Exchange of Energy.

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3. Ensure steady State & Transient stability.

4. Load shedding and prevention of loss of synchronism. Maintaining the system

frequency within targeted limits.

5. Voltage Control; reducing the reactive power flow by compensation of reactive power,

tap-changing.

6. Securing the supply by proving adequate line capacity.

7. Data transmission via power line carrier for the purpose of network monitoring; control

and protection.

8. Fault analysis and pin-pointing the cause and subsequent improvement in that area of

field.

9. Determining the energy transfer through transmission lines.

10. Reliable supply by feeding the network at various points.

11. Establishment of economic load distribution and several associated functions.

TYPES OF SUBSTATION

The substations can be classified in several ways including the following :

1. Classification based on voltage levels, e.g. : A.C. Substation : EHV, HV, MV, LV;

HVDC Substation.

2. Classification based on Outdoor or Indoor : Outdor substation is under open skv.

Indoor substation is inside a building.

3. Classification based on configuration, e.g. :

Conventional air insulated outdoor substation or

SF6 Gas Insulated Substation (GIS)

Composite substations having combination of the above two

4. Classification based on application

Step Up Substation : Associated with generating station as the generating voltage

is low.

Primary Grid Substation : Created at suitable load centre along Primary

transmission lines.

Secondary Substation : Along Secondary Transmission Line.

Distribution Substation : Created where the transmission line voltage is Step Down

to supply voltage.

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Bulk supply and industrial substation : Similar to distribution sub-station but

created separately for each consumer.

Mining Substation : Needs special design consideration because of extra

precaution for safety needed in the operation of electric supply.

Mobile Substation Temporary requirement.

NOTE :

Primary Substations receive power from EHV lines at 400KV, 220KV, 132KV

and transform the voltage to 66KV, 33KV or 22KV (22KV is uncommon) to suit

the local requirements in respect of both load and distance of ultimate consumers.

These are also referred to ‘EHV’ Substations.

Secondary Substations receive power at 66/33KV which is stepped down usually

to 11KV.

Distribution Substations receive power at 11KV, 6.6 KV and step down to a volt

suitable for LV distribution purposes, normally at 415 volts.

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3. LIGHTNING ARRESTOR

Lighting arrestor is a device, which protects the overhead lines and other electrical apparatus

viz , transformer from overhead voltages and lighting When the positively charged cloud

produce negative charge on the overhead line by electrostatic induction then the negative

charge is however presented right under the cloud and portion of the line away from the cloud

becomes positively charged This charge on the line does not flow

Every instrument must be protected from the damage of lighting stroke. The three protection

sin a substation is essential:-

Protection for transmission line from direct strokes

Protections of power station or substation from direct strokes

Protection of electrical apparatus against traveling waves

Effective protection of equipment against direct strokes requires a shield to prevent lighting

from striking the electrical conductor together with adequate drainage facilities over insulated

structure.

Installation Location :-

Install arrester electrically as close as possible to the appearatus being protected Line and

ground connections should be short and direct

Fig 3.1 Lightning Arresters

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Grounding:-

The arrester ground should be connected to the apparatus grounds and the main station

ground utilizing a reliable common ground network of low resistance. The efficient operation

of the lightning arrester requires permanent low resistance grounds : Station class arresters

should be provided with a ground of a value not exceeding five ohms.

Clearances:- These are given on the drawings. These are the maximum recommended. The

term ‘clearance’ means the actual distance between any part of the arrester or disconnecting

device at line potential, and any object at ground potential or other phase potential.

It consist of a isolator in series and connected in such a way that long isolator is in upward

and short isolator is in downward so that initially large potential up to earth is decreased to

zero

An ideal arrestor must therefore have the following properties:

1. It should be able to drain the surge energy from the line in a minimum time

2. Should offer high resistance to the flow of power current

3. Performance of the arresters should be such that no system disturbances are

introduced by its operation

4. Should be always in perfect from to perform the function assigned to it

5. After allowing the surge to pass, it should close up so as not to permit power current

to flow to ground

Fig 3.2 Lightning Arresters

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Working:-

Lightning, is a form of visible discharge of electricity between rain clouds or between a rain

cloud and the earth The electric discharge is seen in the form of a brilliant arc, sometimes

several kilometres long, stretching between the discharge points How thunderclouds become

charged is not fully understood, but most thunderclouds are negatively charged at the base

and positively charged at the top However formed, the negative charge at the base of the

cloud induces a positive charge on the earth beneath it, which acts as the second plate of a

huge capacitor

When the electrical potential between two clouds or between a cloud and the earth reaches a

sufficiently high value (about 10,000 V per cm or about 25,000 V per in), the air becomes

ionized along a narrow path and a lightning flash results.

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4. WAVE TRAP

It is used to trap the communication signals & send PLCC room through CVT.   Rejection

filters are known as the line traps consisting of a parallel resonant circuit ( L and C in

parallel) tuned to the carrier frequency are connected in series at each and of the protected

line such a circuit offer high impedance to the flow of carrier frequency current thus

preventing the dissipation. The carrier current used for PLC Communication have to be

prevented from entering the power equipments such as attenuation or even complete loss of

communication signals. For this purpose wave trap or line trap are used between transmission

line and power station equipment to avoid carrier power dissipation in the power plant reduce

cross talks with other PLC Circuits connected to the same power station. Ensure proper

operating conditions and signal levels at the PLC transmit receive equipment irrespective of

switching conditions of the power circuit and equipments in the stations. 

Line matching filter and protective equipment:-

For matching the transmitter and receiver unit to coupling capacitor and power line matching

filters are provided. These flitters normally have air corral transformers with capacitor

assumed.

The matching transformer is insulated for 7-10 KV between the two windings and perform

two functions. Firstly, it isolates the communication equipment from the power line.

Secondly, it serves to match .

Transmitter:-

The transmitter consists of an oscillator and a amplifier. The oscillator generates a frequency

signal with in 50 to 500 HZ frequency bands the transmitter is provided so that it modulates

the carrier with protective signal. The modulation process usually involves taking one half

cycle of 50 HZ signal and using this to create block to carrier.    

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Fig 4.1 Wave Trap

Receivers:-

The receivers usually consist of and alternate matching transformer band pass filter and

amplifier detector.

The amplifier detector converts a small incoming signal in to a signal capable of operating a

relatively intensive carrier receiver relay. The transmitter and receiver at the two ends of

protected each corresponds to local as far as transmitting. 

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5. ISOLATOR

When carrying out inspection or maintains work in substation ,it is essential to disconnect

reliability the unit of other station on which the work is done from all other parts on

installation in order to ensure full safety of working staff .So guard against mistake it is

desirable that should be done by an apparatus is called “ISOLATOR”. In other words a

device which is used to open or close the circuit either when negligible current is interrupted

or when no significant change in voltage across the terminal of each pole of the isolator will

result from operation .they must only be opened or closed when current is zero. There is

single ear thing Isolator used .

Isolator is switching device used to open (or close) a circuit either when a negligible current

exists or when no significant change in voltage across the terminal of each pole of the

isolator, will result from the operation. Broadly speaking isolator are the switches which’s

operate under "No current” condition.

Fig 5.1 View of Isolator

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Isolators are file with earthing blades as an integral part of it. They may be isolators with

single ear thing blades or two earthling blades on either side of it.They must only be opened

or closed when current is zero. Isolators are classified into following categories.

1. Bus isolator

2. Line isolator

3. Transformer isolating switch

From constructional point of view the isolator may be classified as-

1.The post- centre post rotating part, double post break type.

2.Two post single type.

3.Base: - Each pipe phase isolator is mounted on a robust base of steal construction.

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6. POTENTIAL TRANSFORMER

There are two types of instrument transformer:-1. Potential Transformer

2. Current Transformer

Potential Transformer:-

Similar to CT it is another  type of instrument type of instrument transformer .Transformer

used for voltage measurements are called voltage transformer or Potential transformer. it may

be of 1 phase or 3 phase                                        

These transformers make the instruments suitable for measurement of high voltage and

isolating then from high voltage. these TX. Are connected in parallel and secondary winding

is always open ckt.

The primary has large no of turn in  secondary,which  provided step down of voltage , and

then the voltmeter is connected  across secondary terminal  the high voltage line.Some terms

related to PT :-

1. Rated voltage :-  the capacity voltage  of the PT which it can stand

2. Rated transformer ratio:- The ratio of the rated primary voltage to the rated second voltage.

3. Rated secondary voltage:- 130 / root (3) = 63.3 VAR.

Voltage transformer which step down system voltage to sufficient form high value to low

value are necessary in every system for

Induction of d.c supply voltage conduction.

Metering of the supply of energy.

Relaying

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Syncronizing.

Design and ranges are selected according to the secondary size of potential transformer for

indicating instruments, meter and relays. But calibration of these instruments is done

according to the primary voltage

Fig 6.1 Potential Transformer

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7. CURRENT TRANSFORMER

The current transformers are kept in the category of the instrument transformer. The C.T. are

used to reduce/ stepping down A.C form high value to lower value  for  measurement /

protection / control.

They are usually installed in the outdoor switch. The primary conductor at high voltage with

respect to earth. The secondary of  C.T. is just like the ring type C.T. the primary winding

consists of a very few turns , and therefore there is no. appreciation volt drop across injection

Current is transformed by  C.T. the current transformer is used with primary winding ,

connected in series with the line carrying the current to be measured and therefore primary

current is dependent upon load connected in the system.

  Fig 7.1 Current Transformer

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Measurement of alternating current is one of the most frequent operation not only because of

it’s inheriant but a also because it is necessary in determining other parameters of electrical

circuit. A current transformer value of current is used for

1. Indication of current

2. kwh and kw meters

3. Telementry

4. Protective relay etc

A current transformer is intended to operate normally with rated current of the system

flowing through the primary winding which is increased in the series with the network

Secondary winding of current transformer connected to measuring instruments and relay

supplies currents circulating in the design of current transformer.

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8. POWER TRANSFORMER

There are two power transformers of 160 MVA and 100 MVA . They are used convert 220

KV/66KV.And two power transformers  are used of 20 MVA and 16/20 MVA which convert

66KV/11KV. Which transforms e/e energy from one voltage level to another desired level

with corresponding change in current value and without any change in frequency value.

The physical basis of a transformer is mutual induction between the circuits linked by a

common magnitude pulse voltage supplied to one set of winding called primary switch builds

up a magnitude flux through the iron.

A transformer in simplest form consist of two magnetic coil, which are electrically separated

from each other but magnetically linked through path of reluctance .

Fig 8.1 Power Transformer

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Transformer parts are:-

1. BUCHHOLZ RELAY: It is a very sensitive gas and oil  operated instrument which safely

detect the formation of  gas or sudden pressure inside the oil transformer.

2. CONSERVATOR: It is used to provide adequate space for the expansion of oil when

transformer is loaded or when ambient temprature changes.

3. SILICA GEL BREATHER: It sucks the moisture from the air which is taken by

transformer so that dry air is taken by transformer.

4. DOUBLE DIAPHRAGM EXPLOSION VENT: It is used to discharge excess pressure in

the atmosphere when excess pressure is developed inside the transformer during loading.

5. OIL LEVEL INDICATOR: It is used to show the oil level in the transformer.

6. Winding temperature indicator: used to show the temperature of transformer winding.

7. RADIATORS: These are used for cooling of the transformer oil.

Fig 8.2 Various Parts of Transformer

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9. INSULATOR

Transmission line insulators are devices used to contain, separate or support electrical

conductors on high voltage electricity supply networks. Transmission insulators come in

various shapes and types, including individual or strings of disks, line posts or long rods.

They are made of polymers, glass and porcelain--each with different densities, tensile

strengths and performing properties in adverse conditions.

Pin Type Insulators

Pin type insulators are used for the transmission of lower voltages. A single pin type insulator

is used to transmit voltages up to 11 kV (kilovolts) and higher voltages require two-, three- or

four-piece pin insulators. They are not economically feasible for 33 kV and higher

transmission lines. Pin type insulators are secured with steel or lead bolts onto transmission

poles. These are typically used for straight-running transmission lines.

Fig 9.1 Pin type insulator

Suspension Type Insulators:-

Suspension type transmission line insulators suspend and support high voltage transmission

lines. They are cost effective for higher voltage transmission, typically replacing multiple pin

type insulators. Suspension type insulators have a number of interconnected porcelain discs,

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with each individual unit designed to support a particular voltage. Together, a system of these

discs is capable of effectively supporting high voltages. There are three types of suspension

insulators: cemented cap suspension insulators; interlinking or Hewlett suspension insulators;

and link or core suspension insulators.

Fig 9.2 Suspension type insulator

Strain Type Insulators

Strain type insulators are horizontally suspended suspension insulators. They are used to

handle mechanical stresses and take the pressure off a conductor at the end of a transmission

line, at a sharp corner or curve or over long river crossings. Strain insulators are typically

used for higher voltage transmissions.

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Fig 9.3 Strain type insulator

Shackle Type Insulators:-

Shackle type insulators, similar to strain type insulators, are used on sharp curves, end poles

and in section poles. However, unlike strain insulators, shackle insulators are designed to

support lower voltages. These insulators are single, round porcelain parts that are mounted

horizontally or vertically.

Fig 9.4 Shackle type insulator

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10. CIRCUIT BREAKER

A circuit breaker is an automatically operated electrical switch designed to protect an

electrical circuit from damage caused by overload or short circuit Its basic function is to

detect a fault condition and, by interrupting continuity, to immediately discontinue electrical

flow Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be

reset (either manually or automatically) to resume normal operation Circuit breakers are

made in varying sizes, from small devices that protect an individual household appliance up

to large switchgear designed to protect high voltage circuits feeding an entire city.

In any circuit, carrying a large amount of current, if a contact is opened then normally a spark

is produced due to fact that current traverses its path through air gap Arcing is harmful as it

can damage precious equipment media are provided between contacts.

This is one of the important equipment in power system It protects the system by isolating

the faulty section while the healthy one is keep on working Every system is susceptible to

fault or damages while can be caused due to overloading, short-circuiting, earth fault etc thus

to protect the system and isolate the faulty section C B are required Apart from breaking and

making contacts, a C B should be capable of doing

1. Continuously carry the maximum current at point of installation

2. Make and break the circuit under abnormal and normal condition

Close or open the faulty section only where fault exists

There are different arc quenching media:-

1)       Air blast

2)       Oil

3)       SF6 gas

4)       Vacuum

In 220 kV Grid Devigarh , SF6 gas circuit breaker are used, as for greater capacity SF6 type

breakers are very efficient .

SF6 BREAKER

The outstanding physical and chemical properties of SF6 gas makes it an ideal dielectric

media for use in power switchgear.These properties of SF6 gas makes it an ideal dielectric

media for use in power switchgear,these properties are included:

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1) High dielectric strength

2) unique arc quenching ability

3) Excellent thermal stability

4) Good thermal conductivity

In addition, at normal temperature SF6 is chemically inert,inflammable,noncorrosive and

non-condensable at low temperatures.

SF6 versus oil :-

SF6 is not flammable and toxic like oil.It is easier to handle,maintain and repair equipment

filled with SF6.

In case of breakdown of oil strong surges of pressure may occur due to sudden development

of gaseous products.In case of breakdown of SF6,the only pressure rise will result from the

thermal expansion of gas.

Fig 10.1 SF6 Circuit Breaker

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11. EARTHING

Earthing is the provision of a surface under the substation, which has a uniform potential as

nearly as zero or equal to Absolute Earth potential. The provision of an earthing system for

an electric system is necessary by the following reason. 

1. In the event of over voltage on the system due to lighting discharge or other system fault.

These parts of equipment which are normally dead as for as voltage, are concerned do not

attain dangerously high potential.

2. In a three phase, circuit the neutral of the system is earthed in order to stabilize the

potential of circuit with respect to earth.

The resistance of earthing system is depending on shape and material of earth electrode

used.    

 the earthing is of two principal types  :-

1. Neutral Earthing

2. Equipment Body Earthing

Neutral Earthing:-

Neutral Earthing also known as System Neutral Earthing (or Grounding) means connecting

the neutral point i.e. the star point of generator,transformer etc. to earth. In rotating machines,

generator, transformer circuit etc., the neutral point is always connected to earth either

directly or through a reactance. The neutral point is usually available at every voltage level

from generator or transformer neutral. If neutral point is not available, then the most common

method used is using a Zigzag transformer. Such a transformer has no secondary. Each phase

of primary has two equal parts. There are 3 limbs and each limb has two winding, providing

flux density under normal condition. Since the fluxes are opposite, the transformer takes very

small magnetizing current under normal conditions. During fault, the circuit is primary side,

which provides very less impedance to the current. The grounding transformers are short time

rating. Their size is almost one tenth as compared to power transformer. 

Electrical Earthing:-

electrical Earthing is different from neutral earthing. During fault condition, the metallic parts

of an electrical installation which do not carry current under normal conditions, may attain

high potential with respect to ground. As human body can tolerate only I=0.165A/T current

for a given time t so to ensure safety we connect such metallic parts to earth by means of

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Earthing system ,which comprises of electrical conductor to send fault current to earth. The

conductor used is generally in the form of rods, plates, pipes etc. 

Earthing system ensures safety in following ways :-

1. The potential of earthen body does not reach dangerously high value about earth,

since it is connected to earth.

2.  Earth fault current flows through earthing and readily causes the operation of fuse or

an earth relay.

Connection of Electrical Equipment to Substation:- 

S.No. Apparatus Path to be connected

1.Supporting of bus

insulatorBase plate

2.High voltage circuit

breakerOperating mechanism frame

3. Isolator Operating mechanism frame bed

4. Potential transformer Transformer tank LV

5. Power transformer Core tank

Merits of neutral Earthing:-

1. Arcing grounding is reduced.

2. Voltage of heating with respect to earth remains at harmless value they don't increase to

root 3 times of normal value. 

3. Suitable neutral point.

4. The earth fault relaying is relatively simple useful amount of earth fault current is available

to operate earth fault relay.

5. The over voltage due to lightening are discharged to earth. 

6. Improved service reliability due to limitation of arcing ground and improved of

unnecessary fringing of CB.

At Devigarh the neutral point of power transformer is connected solidly to earth generally the

earth connection are provided which leads reliability.

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12. PROTECTION RELAY

A relay is an electrically operated switch Current flowing through the coil of the relay

creates a magnetic field which attracts a lever and changes the switch contacts The coil

current can be on or off so relays have two switch positions and they are double throw

(changeover) switches.

Relays allow one circuit to switch a second circuit which can be completely separate from the

first For example a low voltage battery circuit can use a relay to switch a 230V AC mains

circuit There is no electrical connection inside the relay between the two circuits, the link is

magnetic and mechanical.

The coil of a relay passes a relatively large current, typically 30mA for a 12V relay, but it can

be as much as 100mA for relays designed to operate from lower voltages. Most ICs (chips)

cannot provide this current and a transistor is usually used to amplify the small IC current to

the larger value required for the relay coil The maximum output current for the popular 555

timer IC is 200mA so these devices can supply relay coils directly without amplification

Types of Relays

These are called normally opened, normally closed in GSS control room there is panel in

which the relays are set and there are many types of relays

1. Over voltage relays

2. Over current relays

3. I D M T fault relay

4. Earth fault relay

5. Bucheloz’s relay

6. Differential relay

OVER VOLTAGE RELAY: - This protection is required to avoid damage of system in case

line becomes open circuited at one end These fault would trip the local circuit breaker thus

block the local and remote ends This relay is operated i e , energized by CVT connected to

lines.

OVER CURRENT RELAY: -This relay has the upper electromagnet of non-directional relay

connected in series with lower non-directional electromagnet When the fault current flow

through relay current coil which produces flux in lower magnet of directional element Thus

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the directional relay has the winding over the electromagnets of non-directional element and

produces a flux in lower magnet and thus over current operates.

EARTH FAULT RELAY: -when a conductor breaks due to some reason and it is earthen

then earth fault occurs The fault current is very high thus, there is need to of over current

relay This relay has minimum operating time

DIRECTIONAL RELAY: - It allows flowing the current only in one direction then only this

relay operates It has a winding connected through the voltage coil of relay to lower magnet

winding called current coil Which is energized by C T if fault occurs This relay operates

when v/I is less than theoretical value The v/I is normally constant .

Fig 12.1 Over Current and Voltage Relays

DIFFERENTIAL RELAY: - This relay operates when phase difference of two electrical

quantities exceeds the predetermined value It has always two electrical quantities; hence in

400kv GSS for transformer differential relay is used

INVERSE TIME CHARACTERISTICS RELAY: - The relay using here having the inverse

time characteristics having the time delays dependent upon current value This characteristic

is being available in relay of special design There are:-

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    i.    Electromagnetic Induction type

       ii.    Permanent magnetic moving coil type

       iii.    Static type

BUCHHOLZ’S RELAY: - It is the protective device of the transformer When any fault

occurs in the transformer then it indicates about fault and we disconnect the transformer from

the circuit It is used in the power transformer It is connected between the tank and

conservator It has two floats on which two mercury switch are attached One float is used for

the bell indication and other float is used for the tripping In the normal position the relay is

filled with the oil and contacts of the mercury switch are opened When the earth fault occurs

in the transformer then it increases the temperature of oil and oil flows into the conservator

through relay On the way it makes the contacts of the tripping circuit short So in the we can

say that this relay works as circuit breaker.

Fig12.2 Buchholz Relay

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13. CONTROL ROOM

To remote control of power switch gear requires the provision of suitable control plates

located at a suitable point remote from immediate vicinity of CB 's and other equipments.

At "220KV DEVIGARH" the separate control room provided for remote protection of

220KV switch yards transformer incoming feeder, outing feeders. Bus bar has their own

control plant in their control rooms. The control panel carrier the appropriate relays.

Necessary meters indicating lamp control switches and fuses. There are meters for reading

purpose. A circuit concerning the panel is shown on the panel with standard co lour.

On each panel a control switch is provided for remote operation of circuit breaker. There are

two indicators which show that weather circuit breaker is closed or open. A control switch for

each insulator is also provided. The position indicator of isolator is also done with the help of

single lamp and indicator. The co lour of signal lamps are as follows :- 

RED :- For circuit breaker or isolator is close option

GREEN :- For CB or isolator in open position.    

In addition to used indication an alarm is also providing for indicating abnormal condition

when any protective relay or tripping relay has operated. Its constants energies on auxiliary

alarm. Relay which on operation completes the alarm belt circuit. 

Energy Meter:-

These are fitted on different panel to record transmitted energy and recorded in energy hours.

For this purpose MWH meter have been provided. 

Watt Meter:-

This is mounted on each feeder panel to record import or export power. 

Frequency Power:-

Provided to each feeder to measure frequency which analog or digital. 

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Volt Meter :-

Provided on each panel or the purpose of indication of voltage. 

Ammeter:-

These are used to indication the line current. 

MVAR Meter:-

Provided for indicating power factor of import and export. 

Maximum Indicator Demand :-

Chief requirement of these indicators to record the minimum power factor taken by feeder

during a particular period. This record the average power successive predetermined period.

Fig 13.1 Control Room

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14. BATTERY ROOM

There is a battery room which has 55 batteries of 2 volt each for 132KV section and 110

batteries for 220KV section. Therefore D.C. power available is for functioning of the control

panels. A battery charger to charge the battery. 

1. Various parts of lead acid batteries:-

1. Plates

2. Separators

3. Electrolyte

4. Container

5. Terminal port

6. Vent plugs

Fig 14.1 View of Battery Room

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CHARGING OF BATTERIES:-

Initial charging

It is the first charging given to batteries by which the   positive plates are converted to “lead

peroxide”, whereas  the –ve plates will converted to spongy lead. Also in a fully charged

battery the electrolyte specific gravity will be at its highest venue or 1.2 and its terminal

voltage will be 24  volts                      

Discharging:-

When a fully charged battery delivers its energy out by meeting a load the lead peroxide of

the +ve plates slowly gets converted to lead sulphate and the spongy lead of the –ve plates

also gets converted into lead sulphate during this time the specific gravity of the electrolyte

also decreases the value around 1.00 and the terminal voltage also decreases from its initial to

a lower value which may be around 1.85 or 1.8.

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15. CAPACITOR BANK

A capacitor bank is a grouping of several identical capacitors interconnected in parallel or in

series with one another. These groups of capacitors are typically used to correct or counteract

undesirable characteristics, such as power factor lag or phase shifts inherent in alternating

current (AC) electrical power supplies. Capacitor banks may also be used in direct current

(DC) power supplies to increase stored energy and improve the ripple current capacity of the

power supply. Single capacitors are electrical or electronic components which store electrical

energy. Capacitors consist of two conductors that are separated by an insulating material or

dielectric. When an electrical current is passed through the conductor pair, a static electric

field develops in the dielectric which represents the stored energy. Unlike batteries, this

stored energy is not maintained indefinitely, as the dielectric allows for a certain amount of

current leakage which results in the gradual dissipation of the stored energy. The energy

storing characteristic of capacitors is known as capacitance and is expressed or measured by

the unit farads. This is usually a known, fixed value for each individual capacitor which

allows for considerable flexibility in a wide range of uses such as restricting DC current

while allowing AC current to pass, output smoothing in DC power supplies, and in the

construction of resonant circuits used in radio tuning. These characteristics also allow

capacitors to be used in a group or capacitor bank to absorb and correct AC power supply

faults.

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Fig 15.1 Capicator Bank

The use of a capacitor bank to correct AC power supply anomalies is typically found in

heavy industrial environments that feature working loads made up of electric motors and

transformers. This type of working load is problematic from a power supply perspective as

electric motors and transformers represent inductive loads, which cause a phenomenon

known as phase shift or power factor lag in the power supply. The presence of this

undesirable phenomenon can cause serious losses in terms of overall system efficiency with

an associated increase in the cost of supplying the power. The use of a capacitor bank in the

power supply system effectively cancels out or counteracts these phase shift issues, making

the power supply far more efficient and cost effective. The installation of a capacitor bank is

also one of the cheapest methods of correcting power lag problems and maintaining a power

factor capacitor bank is simple and cost effective. One thing that should always be kept in

mind when working with any capacitor or capacitor bank is the fact that the stored energy, if

incorrectly discharged, can cause serious burns or electric shocks. The incorrect handling or

disposal of capacitors may also lead to explosions, so care should always be exercised when

dealing with capacitors of any sort.

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CONCLUSION

The training at grid substation was very helpful. It has improved my theoretical concepts of

electrical power transmission and distribution. Protection of various apparatus was a great

thing. Maintenance of transformer, circuit breaker, isolator, insulator, bus bar etc was

observable.

I had a chance to see the remote control of the equipments from control room itself,

which was very interesting.

So the training was more than hope to me and helped me to understand about power

system more.

Now I have studied a lot about the electrical transmission system. One must have never

thought that so many things are required for just switching on a television or a refrigerator or

say an electric trimmer. The three wing of electrical system viz. Generation, transmission and

distribution are connected to each other and that too very perfectly. Here man and electricity

work as if they are a family. Lots of labour, capital and infrastructure is involved in the

system just to have a single phase,220V,50Hz power supply at our houses. At last I would

say...

Energy

Saved

Is

Energy

Produced

35

REFERENCES

1. www.electrical4u.com

2. www.wikipedia.com

3. www.youtube.com

4. www.slideshare.com

5. “Power System” by C.L.Wadhwa

6. “Power System” by V.K. Mehta

7. “Electrical Machine” by P.S. Bimbra

8. Thapar Library

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