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CHAPTER 1

INTRODUCTION

Electrical power is generated, transmitted in the form of alternating current. The

electric power produced at the power stations is delivered to the consumers through a

large network of transmission & distribution. The transmission network is inevitable

long and high power lines are necessary to maintain a huge block of power source of

generation to the load centers to inter connected. Power house for increased reliability

of supply greater.

The assembly of apparatus used to change some characteristics (e.g. voltage, ac

to dc, frequency, power factor etc.) of electric supply keeping the power constant is

called a substation.

An electrical substation is a subsidiary station of an electricity generation,

transmission and distribution system where voltage is transformed from high to low or

the reverse using transformers. Electric power may flow through several substations

between generating plant and consumer, and may be changed in voltage in several

steps.

Fig.1.1 - 132 KV GSS Lakheri [4]

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Substations have switching, protection and control equipment and one or more

transformers. In a large substation, circuit breaker are used to interrupt any short-

circuits or overload currents that may occur on the network.

Depending on the constructional feature, the high voltage substationsmay be further subdivided:

(a) Outdoor substation

(b) Indoor substation

(c) Base or Underground substation

1.1) 132KV Grid Substation, Lakheri:

Its part of RVPN. It is situated 25 km away from Bundi. The power mainly comes from

132 KV Swai Madhopur , 132KV Kota . The substation is equipped with various

equipments and there are various arrangements for the protection purpose. The

equipments in the GSS are listed previously. At this substation following feeders are

established.

1. TIE FEEDERS

2. RADIAL FEEDERS

132KV GSS LAKHERI is an outdoor type primary substation and distribution as wellit has not only step down but the distribution work

The electrical work in a substation comprises to:

1. Choice of bus bar arrangement layout.

2. Selection of rating of isolator.

3. Selection of rating of instrument transformer.

4. Selection of rating of C.B.

5. Selection of lighting arrester [LA]

6. Selection of rating of power transformer

7. Selection of protective relaying scheme, control and relay boards.

8. Selection of voltage regulator equipment.

9. Design a layout of earthing grids and protection against lightening stockes.

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1.2) INCOMING FEEDERS:

The incoming feeders are:

1) 132 kV GSS (Swai Madhopur)

2) 132 kV GSS (Kota)

1.3) OUTGOING FEEDERS:

The outgoing feeders are:

1) Lakheri

2) Ramganj

3) Jharkhoda

4) Nanakpuriya

5) NRI

Rajasthan Rajya Vidyut Prasaran Nigam Limited (RVPN) a company under the

Companies Act, 1956 and registered with Registrar of Companies as "RAJASTHAN

RAJYA VIDYUT PRASARAN NIGAM LIMITED" vide No. 17-016485 of 2000-

2001 with its Registered Office at VIDYUT BHAWAN, Lakheri has been established

on 19 July, 2000 by Govt. of Rajasthan under the provisions of the Rajasthan Power

Sector Reform act 1999 as the successor company of RSEB.

Our aim is to provide reliable electric transmission service to these customers. As a

public utility whose infrastructure serves as the link in transporting electricity to

millions of electricity users, RVPN has following duties and responsibilities:

Ensuring development of an efficient, co-ordinate and economical system of intra-

state transmission of electricity from generating stations to Load Centers.

Non-discriminatory Open Access to its transmission system on payment oftransmission charges

Complying with the directions of RLDC and SLDC, operating SLDC until any other

authority is established by the State Govt.

Now RVPN is "An ISO 9001:2000 Certified Company" [2]

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Fig 1.2: Single Line Diagram of 132KV GSS Lakheri (Bundi) [4]

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CHAPTER 2

LIGHTNING ARRESTER

A lightning arrester (also known as surge diverter) is a device connected

between line and earth i.e. in parallel with the over headline, HV equipments and

substation to be protected. It is a safety valve which limits the magnitude of lightning

and switching over voltages at the substations, over headlines and HV equipments and

provides a low resistance path for the surge current to flow to the ground. The practice

is also to install lightning arresters at the incoming terminals of the line.

Fig.2.1- Lightning arrester [6]

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All the electrical equipments must be protected from the severe damages of lightning

strokes. The techniques can be studied under:-

Protection of transmission line from direct stroke.

Protection of power station and sub-station from direct stroke.

Protection of electrical equipments from travelling waves.

2.1) Types of Arrestors:-

2.1.1) Rod/sphere gap: - It is a very simple protective device i.e. gap is

provided across the stack of Insulators to permit flash-over when

undesirable voltages are impressed of the system.

2.1.2) Expulsion type LA: - It have two electrodes at each end and

consists of a fibre tube capable of producing a gas when is produced.

The gas so evolved blows the arc through the bottom electrode.

2.1.3) Valve type LA: - It consists of a divided spark-gap in series will a

non linear resistor. The divided spark gap consists of a no. of similar

elements, each of it two electrodes across which are connected high

resistor.[3]

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CHAPTER 3

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 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 effect the clearances when it swings while over tensioning may

damage insulators. Clamps or even effect 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.

3.1) BUS BAR ARRANGEMENT MAY BE OF FOLLOWING TYPE

WHICH IS BEING ADOPTED BY R.R.V.P.N.L.:-

3.1.1) Single bus bar arrangement

3.1.2) Double bus bar arrangement

a) Main bus with transformer bus

b) Main bus-I with main bus-II

3.1.3) Double bus bar arrangement with auxiliary bus.

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3.1.1) SINGLE BUS BAR ARRANGEMENT :

This arrangement is simplest and cheapest. It suffers, however, from major

defects.

1. Maintenance without interruption is not possible.

2. Extension of the sub station without a shut down is not possible

3.1.2) DOUBLE BUS BAR ARRANGEMENT :

1. Each load may be fed from either bus.

2. The load circuit may be divided in to two separate groups if needed

from operational consideration. Two supplies from different sources

can be put on each bus separately.

3. Either bus bar may be taken out from maintenance of insulators.

The normal bus selection insulators can not be used for breaking load currents.

The arrangement does not permit breaker maintenance without causing

stoppage of supply.

3.1.3) DOUBLE BUS BAR ARRANGEMENTS CONTAINS MAIN

BUS WITH AUXILARY BUS :

The double bus bar arrangement provides facility to change over to either bus to

carry out maintenance on the other but provide no facility to carry over breaker

maintenance. The main and transfer bus works the other way round. It provides

facility for carrying out breaker maintenance but does not permit bus

maintenance. Whenever maintenance is required on any breaker the circuit is

changed over to the transfer bus and is controlled through bus coupler breaker.

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CHAPTER 5

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

Fig.5.1- Isolators [6]

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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. [1]

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CHAPTER 6

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.

Circuit breaker can be classified as "live tank", where the enclosure that

contains the breaking mechanism is at line potential, ordead tankwith the enclosure at

earth potential. High-voltage AC circuit breakers are routinely available with ratings up

to 765,000 volts.

6.1) Various types of circuit breakers:-

6.1.1) SF6 Circuit Breaker

6.1.2) Air Blast Circuit Breaker

6.1.3) Oil Circuit Breaker

6.1.4) Bulk Oil Circuit Breaker (MOCB)

6.1.5) Minimum Oil Circuit Breaker

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6.1.1) SF6 CIRCUIT BREAKER:-

Sulphur hexafluoride has proved its-self as an excellent insulating and arc quenching

medium. It has been extensively used during the last 30 years in circuit breakers, gas-

insulated switchgear (GIS), high voltage capacitors, bushings, and gas insulated

transmission lines. In SF6 breakers the contacts are surrounded by low pressure SF6

gas. At the moment the contacts are opened, a small amount of gas is compressed and

forced through the arc to extinguish it.

Fig.6.1-SF6 Circuit Breaker [4]

6.1.2) AIR BLAST CIRCUIT BREAKER:

The principle of arc interruption in air blast circuit breakers is to direct a blast of

air, at high pressure and velocity, to the arc. Fresh and dry air of the air blast

will replace the ionized hot gases within the arc zone and the arc length is

considerably increased. Consequently the arc may be interrupted at the first

natural current zero. In this type of breaker, the contacts are surrounded by

compressed air. When the contacts are opened the compressed air is released in

forced blast through the arc to the atmosphere extinguishing the arc in the

process.

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Fig.6.2-Air Blast Circuit Breaker[4]

Advantages:

An air blast circuit breaker has the following advantages over an oil circuit breaker:

The risk of fire is eliminated

The arcing products are completely removed by the blast whereas the oil

deteriorates with successive operations; the expense of regular oil is

replacement is avoided

The growth of dielectric strength is so rapid that final contact gap needed for arc

extinction is very small this reduces the size of device

The arcing time is very small due to the rapid build up of dielectric strength

between contacts. Therefore, the arc energy is only a fraction that in oil circuit

breakers, thus resulting in less burning of contacts

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Due to lesser arc energy, air blast circuit breakers are very suitable for

conditions where frequent operation is required

The energy supplied for arc extinction is obtained from high pressure air and is

independent of the current to be interrupted.

Disadvantages:

Air has relatively inferior arc extinguishing properties.

Air blast circuit breakers are very sensitive to the variations in the rate of

restriking voltage.

Considerable maintenance is required for the compressor plant which supplies

the air blast

Air blast circuit breakers are finding wide applications in high voltage installations.

Majority of circuit breakers for voltages beyond 110 kV are of this type.

6.1.3) OIL CIRCUIT BREAKER:

Circuit breaking in oil has been adopted since the early stages of circuit breakers

manufacture. The oil in oil-filled breakers serves the purpose of insulating the live parts

from the earthed ones and provides an excellent medium for arc interruption. Oil circuit

breakers of the various types are used in almost all voltage ranges and ratings.

However, they are commonly used at voltages below 115KV leaving the higher

voltages for air blast and SF6 breakers. The contacts of an oil breaker are submerged in

insulating oil, which helps to cool and extinguish the arc that forms when the contacts

are opened. Oil circuit breakers are classified into two main types namely: bulk oil

circuit breakers and minimum oil circuit breakers.

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The advantages of using oil as an arc quenching medium are:

1. It absorbs the arc energy to decompose the oil into gases, which have

excellent cooling properties.

2. It acts as an insulator and permits smaller clearance between live conductors

and earthed components.

The disadvantagesof oil as an arc quenching medium are:

1. Its inflammable and there is risk of fire

2. It may form an explosive mixture with air.

3. The arcing products remain in the oil and it reduces the quality of oil after

several operations. This necessitates periodic checking and replacement of oil.

6.1.4) BULK OIL CIRCUIT BREAKER:

Bulk oil circuit breakers are widely used in power systems from the lowest

voltages up to 115KV. However, they are still used in systems having voltages

up to 230KV.The contacts of bulk oil breakers may be of the plain-break type,

where the arc is freely interrupted in oil, or enclose within arc controllers. Plain-

break circuit breakers consist mainly of a large volume of oil contained in a

metallic tank. Arc interruption depends on the head of oil above the contacts

and the speed of contact separation. The head of oil above the arc should be

sufficient to cool the gases, mainly hydrogen, produced by oil decomposition. A

small air cushion at the top of the oil together with the produced gases will

increase the pressure with a subsequent decrease of the arcing time.

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6.1.5) MINIMUM OIL CIRCUIT BREAKER:

Bulk oil circuit breakers have the disadvantage of using large quantity of oil. With

frequent breaking and making heavy currents the oil will deteriorate and may lead to

circuit breaker failure. This has led to the design of minimum oil circuit breakers

working on the same principles of arc control as those used in bulk oil breakers. In this

type of breakers the interrupter chamber is separated from the other parts and arcing is

confined to a small volume of oil. The lower chamber contains the operating

mechanism and the upper one contains the moving and fixed contacts together with the

control device. Both chambers are made of an insulating material such as porcelain.

The oil in both chambers is completely separated from each other. By this arrangement

the amount of oil needed for arc interruption and the clearances to earth are roused.

However, conditioning or changing the oil in the interrupter chamber is more frequent

than in the bulk oil breakers. This is due to carbonization and slugging from arcs

interrupted chamber is equipped with a discharge vent and silica gel breather to permit

a small gas cushion on top of the oil. Single break minimum oil breakers are available

in the voltage range 13.8 to 34.5 KV.

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CHAPTER 7

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.

Fig.7.1-Relays [6]

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7.1) Distance Relays:

Distance relays respond to the voltage and current, i.e., the impedance, at the

relay location. The impedance per mile is fairly constant so these relays respond to the

distance between the relay location and the fault location. As the power systems

become more complex and the fault current varies with changes in generation and

system configuration, directional over current relays become difficult to apply and to

set for all contingencies, whereas the distance relay setting is constant for a wide

variety of changes external to the protected line.

7.2) Types of Distance relay:-

7.2.1) Impedance Relay:

The impedance relay has a circular characteristic centred. It is non directional and is

used primarily as a fault detector.

7.2.2) Admittance Relay:

The admittance relay is the most commonly used distance relay. It is the tripping relay

in pilot schemes and as the backup relay in step distance schemes. In the

electromechanical design it is circular, and in the solid state design, it can be shaped to

correspond to the transmission line impedance.

7.2.3) Reactance Relay:

The reactance relay is a straight-line characteristic that responds only to the reactance

of the protected line. It is non directional and is used to supplement the admittance

relay as a tripping relay to make the overall protection independent of resistance. It is

particularly useful on short lines where the fault arc resistance is the same order of

magnitude as the line length.[4]

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CHAPTER 8

POWER TRANSFORMER

Power transformers are called autotransformers.

8.1) 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.8.1-Power Transformer [6]

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8.2) 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.

8.3) Cooling Equipments:

Cooling equipment shall conform to the requirement stipulated below:

(a.) 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.

(b.) 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.

Fig.8.2-Radiator with fan [6]

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8.4) Transformer Accessories:

8.4.1) Buchholz Relay:

This has two Floats, one of them with surge catching baffle and gas collecting space at

top. This is mounted in the connecting pipe line between conservator and main tank.

This is the most dependable protection for a given transformer.

Gas evolution at a slow rate that is associated with minor faults inside the transformers

gives rise to the operation or top float whose contacts are wired for alarm. There is a

glass window with marking to read the volume of gas collected in the relay. Any major

fault in transformer creates a surge and the surge element in the relay trips the

transformer. Size of the relay varies with oil volume in the transformer and the

mounting angle also is specified for proper operation of the relay.

Fig.8.3-Buchholz Relay [4]

8.4.2) 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.

This is done by adding the temperature rise due to the heat produced in a heater coil

(known as image coil) when a current proportional to that flowing in windings is passed

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in it to that or top oil. For proper functioning or OTI & WTI it is essential to keep the

thermometers pocket clean and filled with oil.

Fig.8.4-Winding and oil temperature indicator[5]

8.4.3) 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.8.5-Silica gel Breather [5]

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8.4.4) Conservator:

With the variation of temperature there is corresponding variation in the oil volume. To

account for this, an expansion vessel called conservator is added to the transformer

with a connecting pipe to the main tank. In smaller transformers this vessel is open to

atmosphere through dehydrating breathers (to keep the air dry). In larger transformers,

an air bag is mounted inside the conservator with the inside of bag open to atmosphere

through the breathers and the outside surface of the bag in contact with the oil surface.

Fig.8.6-Conservator with Buchholz relay and tank [6]

Total No. of transformers = 3 No. of transformers

132/33 KV------------------------------------20/25MVA 2

33/.415 KV-------------------------------------- 250KVA 1

MAKE Company

132/33 KV, 20/25 MVA X-Mer ----------------------------------- BBL

132/33 KV, 20/25 MVA X-Mer ---------------------------------- EMCO

33/.415 KV, 250KVA X-Mer ---------------------------------- SWATHIK

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CHAPTER 9

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.

Now a day mostly separate current transformer units are used instead of bushing

mounting CTs on leveled structure they should be for oil level indication and base

should be earthed properly. Care should be taken so that there should be no strain as the

terminals.

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. There should be no chance of secondary circuit remaining

opens as it leads to extremely high voltage which ultimately damages the CT itself

Fig.9.1-Current Transformers [4]

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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.

Current transformers are also used for street lighting circuits. Street lighting

requires a constant current to prevent flickering lights and a current transformer is used

to provide that constant current. In this case the current transformer utilizes a moving

secondary coil to vary the output so that a constant current is obtained.

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CHAPTER 10

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.

Fig.10.1-Potential Transformer [6]

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.

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The capacitance type voltage transformers are of twp type:

Coupling Capacitor type

Pushing Type

The performance of CVT is affected by the supply frequency switching

transient and magnitude of connected Burdon. The CVT is more economical than an

electromagnetic voltage transformer when the nominal supply voltage increases above

66KV.

The carrier current equipment can be connected via the capacitor of the CVT.

There by there is no need of separate coupling capacitor. The capacitor connected in

series act like potential dividers, provided, the current taken by burden is negligible

compared with current passing through the series connected capacitor.

CVT as coupling capacitor for carrier current application:

The carrier current equipments is connected to the power line via coupling capacitor.

The coupling CVT combines the function of coupling and voltage transformer.[3]

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CHAPTER 11

CAPACITIVE VOLTAGE TRANSFORMER

A capacitor voltage transformer (CVT) is a transformer used in power systems

to step-down extra high voltage signals and provide low voltage signals either for

measurement or to operate a protective relay. In its most basic form the device consists

of three parts: two capacitors across which the voltage signal is split, an inductive

element used to tune the device to the supply frequency and a transformer used to

isolate and further step-down the voltage for the instrumentation or protective relay.

The device has at least four terminals, a high-voltage terminal for connection to the

high voltage signal, a ground terminal and at least one set of secondary terminals for

connection to the instrumentation or protective relay. CVTs are typically single-phase

devices used for measuring voltages in excess of one hundred kilovolts where the use

of voltage transformers would be uneconomical. In practice the first capacitor, C 1, is

often replaced by a stack of capacitors connected in series. This results in a large

voltage drop across the stack of capacitors that replaced the first capacitor and acomparatively small voltage drop across the second capacitor, C2, and hence the

secondary terminals.

The porcelain in multi unit stack, all the potentials points are electrically tied and

suitably shielded to overcome the effect of corona RIV etc. Capacitive voltage

transformers are available for system voltage. [4]

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CHAPTER 12

CONTROL ROOM

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.12.1-Control Room in GSS Lakheri [6]

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12.1) MEASURING INSTRUMENT USED:

12.1.1) ENERGY METER: To measure the energy transmitted energy meters are

fitted to the panel to different feeders the energy transmitted is recordedafter one hour regularly for it MWHr, meter is provided.

12.1.2) WATTMETERS: It is attached to each feeder to record the power exported

from GSS.

12.1.3) FREQUENCY METER: To measure the frequency at each feeder there is

the provision of analog or digital frequency meter.

12.1.4) VOLTMETER: It is provided to measure the phase to phase voltage .It is

also available in both the analog and digital frequency meter.

12.1.5) AMETER: It is provided to measure the line current. It is also available in

both the forms analog as well as digital.

12.1.6) MAXIMUM DEMAND INDICATOR: There are also mounted the control

panel to record the average power over successive predetermined period.

12.1.7) MVAR METER: It is to measure the reactive power of the circuit.

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CHAPTER 13

CAPACITOR BANK

The capacitor bank provides reactive power at grid substation. The voltage

regulation problem frequently reduces so of circulation of reactive power.

Unlike the active power, reactive power can be produced, transmitted and

absorbed of course with in the certain limit, which have always to be workout. At any

point in the system shunt capacitor are commonly used in all voltage and in all size.

Fig.13.1-Capacitor Bank [4]

Benefits of using the capacitor bank are many and the reason is that capacitor

reduces the reactive current flowing in the whole system from generator to the point of

installation.

1 .Increased voltage level at the load

2. Reduced system losses

3. Increase power factor of loading current

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CHAPTER 14

POWER LINE CARRIER COMMUNICATION

As electronics plays a vital role in the industrial growth, communication is also a

backbone of any power stations. Communication between various generating and

receiving station is very essential for proper operation of power of power system. This

is more in case of large interconnected system where a control leads dispatch station

has to co-ordinate the working of various unit to see that the system is maintained in

the optimum working condition, power line communication is most ec2onomic and

reliable method of communication for medium and long distance in power network.

14.1) Wave Trap:

Line trap also is known as Wave trap. What it does is trapping the high

frequency communication signals sent on the line from the remote substation

and diverting them to the telecom teleprotection panel in the substation control

room (through coupling capacitor and LMU).

Fig.14.1-Wave Trap [4]

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This is relevant in Power Line Carrier Communication (PLCC) systems for

communication among various substations without dependence on the telecom

company network. The signals are primarily teleprotection signals and in addition,

voice and data communication signals.

The Line trap offers high impedance to the high frequency communication signals thus

obstructs the flow of these signals in to the substation bus bars. If there were not to be

there, then signal loss is more and communication will be ineffective/probably

impossible.[2]

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CHAPTER 15

EARTHING OF THE SYSTEM

The provision of an earthing system for an electric system is necessary by the following

reason.

In the event of over voltage on the system due to lightening 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.

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.

Depth in the soil.

Specific resistance of soil surrounding in the neighbourhood of system electrodes.

15.1) PROCEDURE OF EARTHING:

Technical consideration the current carrying path should have enough capacity to deal

with more faults current. The resistance of earth and current path should be low enough

to prevent voltage rise between earth and neutral. The earth electrode must be driven in

to the ground to a sufficient depth to as to obtain lower value of earth resistance. To

sufficient lowered earth resistance a number of electrodes are inserted in the earth to a

depth, they are connected together to form a mesh. The resistance of earth should be for

the mesh in generally inserted in the earth at 0.5m depth the several point of mesh then

connected to earth electrode or ground conduction. The earth electrode is metal plate

copper is used for earth plate.

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15.2) NEUTRAL EARTHING:

Neutral earthing of power transformer all power system operates with

grounded neutral. Grounding of neutral offers several advantages the neutral

point of generator transformer is connected to earth directly or through a

reactance in some cases the neutral point is earthed through an adjustable

reactor of reactance matched with the line.

The earth fault protection is based on the method of neutral earthing.

The neutral earthing is associated switchgear.

The neutral earthing is provided for the purpose of protection arcing grounds

unbalanced voltages with respect to protection from lightening and for improvement of

the system.

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CHAPTER 16

BATTERY ROOM

In a GSS, separate dc supply is maintained for signalling remote position control, alarm

circuit etc. Direct current can be obtained from 132volt 3 phase ac supply via rectifier

and in event of ac failure, from the fixed batteries, which are kept, charged in normal

condition by rectifier supply.

Fig.16.1-Battery Room [5]

Battery System:

The batteries used are lead acid type having a solution of sulphuric acid and

distilled water as electrolytes. In charged state, it has a specific gravity of 1.2 at

temperature of 30C.In the battery room batteries are mounted on wooden stand. The

cells are installed stand by porcelain.

Following precautions are taken in a battery room:

The conductor connecting the cells are greased and coated with electrolyte resisting

varnish.

Proper care is taken so that acid vapours do not accumulate in the room to avoid

risk of explosion, smoking, winding etc.

The windows of battery are of forested glass to avoid the batteries from direct action of

sun light.

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CHAPTER 17

RATINGS

17.1) TRANSFORMER:

Total No. of transformers = 3 No. of transformers

132/33 KV------------------------------------20/25MVA 2

33/.415 KV-------------------------------------- 250KVA 1

MAKE Company

132/33 KV, 20/25 MVA X-Mer ----------------------------------- BBL

132/33 KV, 20/25 MVA X-Mer ---------------------------------- EMCO

33/.415 KV, 250KVA X-Mer ---------------------------------- SWATHIK

17.2) CIRCUIT BREAKER:

No. of 132KV breaker - 5


No. of Capacitor Bank (33kv)- 2


SF6 CB

BREAKER SERIAL NO. 030228

RATED VOLTAGE 145KV

NORMAL CURRENT 25KA

FREQUENCY 5OHz

LIGHTNING IMPULSE WITHSTAND 650KV (Peak)

DURATION OF SHORT CIRCUIT 3 Sec.

SF6 GAS PRESSURE AT 27C 7.0 Bar

TOTAL MASS OF CB 1300Kg

MASS OF SF6 GAS 8.7Kg [7]

17.3)BATTERY CHARGER:

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Battery Charger 132AH VDC HBL NIFE LTD.

440AH VDC HBL NIFE LTD.

Capacitor BankNo.-1 ABB 38KV 7.2MVAR

Capacitor BankNo.-1 ABB 38KV 7.2MVAR

17.4) CURRENT TRANSFORMER:

FREQUENCY 50Hz

HIGHEST SYSTEM VOLTAGE 145KV

SHORT TIME CURRENT 25KA/15

RATED CURRENT 600A

17.5)CAPACITIVE VOLTAGE TRANSFORMER:

SERIAL NO. 0173537

INSULATION LEVEL 460KV

RATED VOLTAGE FACTOR 1.2/cont

TIME 1.5/30sec.

HIGHEST SYSTEM VOLTAGE 145KV

PRIMARY VOLTAGE 22OKV/1.732

TYPE OUTDOOR Wgt. 850Kg

PHASE SINGLE TBONP.CAT 50C

SECONDARY VOLTAGE 110/1.732 110/1.732FREQUENCY 49.5-50.5Hz [7]

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CONCLUSION

Training at 132KV GSS Lakheri, Bundi gives the insight of the real instruments used.

There are many instruments like transformer, CT, PT, CVT, LA, relay , PLCC, bus bars,

capacitor bank, insulator, isolators, control room, Battery room etc. What is the various

problem seen in substation while handling this instruments. There are various occasion

when relay operate and circuit breaker open, load shedding, shut down, which has been

heard previously.

To get insight of the substation, how things operate, how things manage all is

learned there. Practical training as a whole proved to be extremely informative and

experience building and the things learnt at it would definitely help a lot in snapping

the future ahead a better way.

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REFERENCES

1. ASHFAQ HUSSAIN (2005), ELECTRICAL POWER SYSTEM CBS

publisher and distributors P79, P501, P516.

2. B.R.GUPTA (2005), POWER SYSTEM ANALYSIS AND DESIGN

S.Chand & Company Ltd. pp121-154

3. V.K.MEHTA (2002), POWER SYSTEM S.chand & company Ltd. P447,

P483, P507, P527, P555.

4. https://reader009.{domain}/reader009/html5/0403/5ac3036e689fd/5ac3037d3f9e9.png

5. HTTP://WWW.GOOGLE.CO.IN/SEARCH?

HL=EN&SAFE=ACTIVE&BIW=1024&BIH=576&TBM=ISCH&SA=1&Q=

GRID+SUBSTATION&OQ=GRID+SUB&AQ=0&AQI=G1G-

M2&AQL=&GS_SM=E&GS_UPL=201433L218873L0L222807L44L22L2L0

L0L6L270L3543L0.10.9L20L0

6. www.browzen.com/relay

7. Manual of GRID SUB STATION
http://upload.wikimedia.org/wikipedia/en/6/63/cvt.pnghttp://www.browzen.com/relayhttp://www.browzen.com/relayhttp://upload.wikimedia.org/wikipedia/en/6/63/cvt.pnghttp://www.browzen.com/relay

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