Chambal Power House (c.p.h) Yard

Summer practical training 2011

INTRODUCTION TO CHAMBAL POWER HOUSE (C.P.H) YARD

The 132 KV G.S.S. CHAMBAL RAJASTHAN RAJYA VIDYUT PRASARAN NIGAM Ltd. is ideally located at the HawaSadak, Sodala, Jaipur & was established in 1962.

G.S.S. is the means of connection between Generating Station & Consumers (Industrial & Domestic etc.) by providing safety & reliability of whole system in case of fault.

The steps of this sub-station are:-

To step down the incoming voltage of the power transmission to a required value i.e. 132 KV to 33 KV &11 KV

Supply to consumer’s feeders or GSS is done by connecting auto t/f operation & requirement of various equipments have been included in detailed further in report.

There are three incoming lines from different three sub-stations.

These are:-

Chambal is connected to Heerapura G.S.S. of 220 KV from which two lines are coming from Heerapura

1. Directly from heerapura2. Heerapura to Nallah Power House(N.P.H.) then to Chambal.

Another line from Sanganer G.S.S.to Chambal via Mansarovar G.S.S.

Incoming volts of Power Transmission of 132 KV is stepped down to 33 KV & 11 KV &then is supplied to consumer’s feeders from this G.S.S.

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NECESSARY COMPONENTS FOR A SUB STATION

(A)Outdoor switch yard (i) Incoming lines (i/c)(ii) Outgoing lines(o/g)(iii) Bus bars(iv) Transformers(t/f s)(v) Insulators(vi) Sub-station equipments such as circuit breakers, insulators, earthing

strips, lightening arrestors, CTs, PTs, isolators, clamps & connectors.(vii) Overhead earth wire shielding against lightening strokes (viii) Galvanized steel structures for towers, gantries, support(ix) Power Line Carrier Communication (PLCC) equipments including

wave trap, turning unit coupling capacitor etc.(x) Control cables for metering protection & control(xi) Road railway tracks(xii) Capacitor bank(xiii) Station lightening system

(B) Main office building (i) Main administration buildings

(C) Battery room direct current( D.C.) distribution system (i) D.C. dry cells batteries & charging equipments(ii) D.C. distribution system or D.C. panel

(D)Mechanical , electrical & other auxiliaries (i) Fire extinguishers(ii) Lightening system(iii) Oil purification system(iv) Telephone system

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(v) Workshops, stores, etc.

(E) Protection system (i) Current t/f s & potential t/f s(ii) Protective cables(iii) Protective relays(iv) Circuit breakers(v) Lightening arrestors

EQUIPMENTS AVAILABLE IN THE CHAMBAL G.S.S. JAIPUR, RAJASTHAN

S. No.

NAME OF EQUIPMENTS TYPE & MAKE T.N. No. & DATE

DATE OF COMMISION

(a) TRANSFORMERS (S.R. NO.)1. 132/11 KV,16/20 MVA

(220066)TRANSFROMERS & RECTIFIER (I) Ltd.

TN 2794/ 31.12.08

2010

2. 132/11 KV,16/20 MVA(220064)

TRANSFROMERS & RECTIFIER (I) Ltd.

TN 2794/ 31.12.08

2009

3. 132/11 KV,16/20 MVA(B-29372)

GEC ALSTOM TN 2414

4. 132/11 KV,16/20 MVA(T-8543/1)

CROMPTON GREEVES

TN 2414

5. 132/33 KV,40/50 MVA (01572/144P)


TN 2861/ 21.02.05

28.12.05

6. 132/33 KV,40/50 MVA(2000-06.3/144P)


07.03.06

7. 11KV/0.4V,250 KVA GEC 17.07.90

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8. 11KV/0.4V,100KVA KAYCEE 23.03.849. 132/11 KV,10/12.5 MVA TELK,KERELA 10.11.20

00(b) 132 KV C.B.

1. 132 KV C.B.(16/20 MVA) T/F s SIEMENS-SF6 TN-2611/ 24.02.03

07.02.05

2. 132 KV C.B. for NPH SIEMENS-SF6 17.02.053. 132 KV C.B. for Sanganer SIEMENS-SF6 17.02.054. 132 KV C.B. for 20 MVA T/F s SIEMENS-SF6 03.02.055. 132 KV Bus Coupler C.B. SIEMENS-SF6 03.02.056. 132 KV OCB for I/C Heerapura C.G.E.KSO-138-

50001967

7. 132 KV OCB for 40/50 MVA Tr.2 C.G.E.KSO-138-5000

1967

8. 132 KV OCB for 40/50 MVA Tr.1 SIEMENS-SF6 TN-2611/ 24.02.03

21.04.06

(c) 33 KV C.B.’s1. 33 KV VCB for I/C – 1 BHEL/VCB/

PVN-362705 28.12.05

2. 33 KV VCB for I/C – 2 BHEL/VCB/PVN-36

15.03.97

3. 33 KV OCB BHEL 19814. 33 KV VCB Vidhan Sabha S&S Power 12.01.985. 33 KV VCB KhasaKothi S&S Power 03.01.986. 33 KV VCB Durgapura BHEL 18.03.977. 33 KV VCB LalKothi BHEL 15.03.978. 33 KV OCB BHEL HLC

36110001979

9. 33 KV VCB MREC S&S Power 01.01.9810. 33 KV VCB Capacitor No.1

(4.19 MVAR) S&S Power 27.12.97

11. 33KV VCB Capacitor No.2(4.19 MVAR)

S&S Power 27.12.97

12. 33 KV VCB Capacitor No. 3(2.10 MVAR)

S&S Power 27.12.97

(d) 11 KV OUTDOOR VCB’s

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1. 11 KV I/C - 1 for 20 MVA TRF 32. 11 KV I/C - 2 for 20 MVA TRF 33. 11 KV outgoing NBC BHEL-VCB

PVN-1224171/ 23.12.95

1997

4. 11 KV outgoing Pratap Lines ALSTOM/PCOB- 17.5 VCB

2639 09.06.06

5. 11 KV outgoing Gandhi Nagar - 1 ALSTOM/PCOB- 17.5 VCB

2639 13.06.06

6. 11 KV outgoing Jamuna Nagar ALSTOM/PCOB- 17.5 VCB

2639 07.06.06

7. 11 KV outgoing Gandhi Nagar - 2 GEC ALSTOM /VCB/PCOB-15

2417 17.06.06

8. 11 KV Queen’s Road GEC ALSTOM /VCB/PCOB-15

17.05.97

9. Ajmer Road GEC ALSTOM /VCB/PCOB-15

14.05.97

10. R/N Bagh– 2 GEC ALSTOM /VCB/PCOB-15

20.05.97

11. KhasaKothi GEC ALSTOM /VCB/PCOB-15

22.04.97

12. 22 Godam GEC ALSTOM /VCB/PCOB-15

25.05.97

13. LalKothi GEC ALSTOM /VCB/PCOB-15

22.05.97

14. Capacitor Bank 1, 5 MVAR (Trf 3) S&S POWER/VCB 13.12.9415. Capacitor Bank 2, 4 MVAR (Trf 4) AREVA/PCOB-

17.5 VCB2706 03.06.06

16. Sewage Farm ABB-SF6/HPA-12/1240

30.05.03

1. 2x12.5 MVA 9/C-1 ABB-SF6/HPA-12/1240

09.05.95

2. 2x12.5 MVA 9/C-2 ABB-SF6/HPA-12/1240

06.05.95

3. R/N Bagh-2 ABB-SF6/HPA-12/1240

04.05.95

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4. Akashwani-Nirman Nagar BHEL VCB/ PVN-12

15.09.97

5. Mahesh Nagar BHEL VCB/ PVN-12

15.04.97

6. N.S. Road ALSTOM/PCOB- 17.5 VCB

2639 20.06.06

7. Residency BHEL VCB/ PVN-12

08.04.97

8. E.S.I. BHEL VCB/ PVN-12

06.04.97

9. Bus Coupler BHEL VCB/ PVN-12

09.04.97

10. Capacitor Bank No. 1, 5 MVAR (Trf 1& 2)

VCB SIEMENS TN 2417 29.10.99

11. Capacitor Bank No. 2, 4 MVAR (Trf 1& 2)

04.11.91

12. I/C No. 1 TR4 (CROMPTON) TN 2417A 05.11.9913. I/C No. 2 TR4 (CROMPTON) TN 2417A 05.11.99

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DESCRIPTION OF EQUIPMENTS ASSEMBLED IN THE YARD

1) WAVE TRAP: It is used to trap the communication signals & send it to the PLCC control room through CVT. This wave trap allows the power frequency to pass through it &obstructs the communication signals & allows them to pass through CVT. It has inductive coil of 0.5 mH.

Wave trap

2) CAPACITIVE VOLTAGE TRANSFORMER: It allows the carrier signals to pass through it. These signals are then send to the “carrier set”.

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Capacitive voltage transformer

3) COUPLING CAPACITOR: Coupling capacitor is used to minimize the noise & disturbance in the communication line. This is connected b/w wave trap & communication line. It consists of high frequency receiver transmitted to one of the line conductor.

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Coupling capacitor or dead tank breaker

4) POWER LINE CARRIER COMMUNICATION: There is no use of telephone lines in the exchange of important information between grid sub-station.

This information are received by wave traps in GSS. These wave traps are connected with 132 KV lines in series with L.A. & coupling capacitors.

The main work of wave trap is interchange of electrical waves into sound waves & sound waves into electrical waves.

When information is send b/w one GSS to the other GSS, sound waves get trapped& these waves are converted into electrical waves& these electrical waves get in other GSS through main line.

5) BUS BARS: “bus bar” term is used for main bar or conductor carrying an electric current to which many connections may be made.

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In some arrangement two buses are provided to which the incoming or outgoing feeders & the principle equipment may be connected. One bus is usually called “main bus “and the other is called “auxiliary bus”.

6) INSULATORS: In order to prevent the flow of current to earth from the support, the transmission lines or distributions lines are all secured to the supporting towers or poles with the help of insulators. Thus the insulators play an important part in the successful operation of the lines.

The chief operation or requirements for the insulators are :-

(i) They must be mechanically very strong.(ii) Their dielectric strength must be very high.(iii) They must provide very high insulation resistance to the leakage

currents.(iv) They must be free from the internal impurities.(v) They should not be porous.(vi) They must be impervious to the entrance of gases or liquids.(vii) They should not be affected with the change in temperature.(viii) They must have high ratio of puncture strength of flash over voltage.

There are many types of insulators in power system, but at extra high voltage transmission only 3 types of insulators are used.

They are:

Strain type or tension type insulators (upto 33KV) Suspension type insulators or disc type insulators (above 33 KV) Post type insulator (for supporting the bus bar & disconnecting

switches in sub-stations).

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Product Description Cross-arm Composite Insulator:

Rated voltage(kv): 10KV Rated curve withstand loading: 5KN Frame height: 250mm Min. Electric arc distance: 380mm Min. Creepage distance: 480mm

7) EARTHING: Connecting of an electrical equipment or apparatus to the earth with the help of a connecting wire of negligible resistance is known as “earthing”.The earthing can be divided into two parts :-

SYSTEM EARTHINGIt is required to provide low fault independent to the ground fault current for proper operations of the protective relays & for meeting the system requirements by effective earthed system.

SAFETY EARTHINGIt is required to provide protection to the operating staff working in the yard & sub-station from injury during fault conditions by keeping the voltage gradient within safe limits.

METHODS OF EARTHING Pipe earthing

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Plate earthing

8) ISOLATORS An isolator or disconnecting switch is used to open some given part of a power circuit after switching off the load by means of a CB. Thus isolators serve only for preventing the voltage from being applied to some given section of the bus switch gear installation or to one or another price of apparatus in the installation.In some cases isolators may be used as a C.B. device, their use for this purpose is strictly limited by definite conditions such as the power rating of the given circuit.There are 2 types of isolators:(1) Single pole isolators(2) Three pole isolators

Description :Model NO.:GW7Standard:IECPrice:NegotiableTechnical specification:

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9) FUSES “fuse” is a wire of short length or thin strip of material having low melting point, which is inserted in an electric circuit as a protective device to the flow of an excessive current (i.e. current greater than maximum current (i.e. current greater than maximum current allowed to flow through the circuit in normal conditions).

Fuse

CAPACITOR BANK

We know that power factor depends on the nature of load which we are supplying.

If the load is purely resistive then the power factor will be unity. If the load is purely inductive then the power factor will be lagging. If the load is purely capacitive then the power factor will be leading.

But most of the load is inductive so that the line power factor becomes lagging and affects the regulation point of view. So to improve the power factor, capacitor bank is erected or used at 132 KV G.S.S.

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Rated voltage 132KVHighest system voltage 145KVInsulation level ( 275 -650 ) KVFrequency 50Hz


Since due to low power factor, voltage drop gets higher, the regulation of the line disturbs.

Capacitor bank

Rated voltage 400-700KVRated power 6.25kvarRated frequency 50HZSwitching contactors

Equipments used in capacitor bank

(1) Lightening arrestor

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(2) Isolator with earthing table(3) Circuit Breaker(4) Residual voltage t/f(5) Series reactor(6) Cell(7) Fuses(8) Protection relay (9) CT for protection

Protection provided to a capacitor bank

(1) Current unbalance protection(2) Voltage unbalance protection(3) Over current and earth fault protection(4) Over voltage protection(5) No voltage protection(6) Fuse protection(7) Series reactor(8) Neutral displacement protection

BRIEF DESCRIPTION

SERIES REACTOR: Normally series reactors are used with the capacitor banks which help in suppressing the switches transient to a permissible value. Normally a value of 6% of the rating of the capacitor bank is chosen. While selecting the rated voltage of the capacitor core shall be paid for the over voltage cause due to the series reactor. It is always advisable to operate the bank at full rating as far as possible with the particular reactor. If the capacitor bank is of lesser rating then there are chances of resonance occurring between the capacitor bank and reactor which may cause failure of capacitors. Hence it is advisable not to operate the capacitor bank at a lower rating with the series reactor.

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RESIDUAL VOLATGE TRANSFORMER : In the event of partial failure of capacitor unit, the healthy units connected in parallel are subjected to over voltages, various methods of unbalance protection to detect the failed units are used. The most commonly used method of protection is through the open delta winding of a RVT.

LIGHTENINGARRESTOR : The ground wire or earthing screen does not provide protection against the high voltage waves reaching the terminal equipment. So some protective devices are necessary to protect the power stations, sub stations and transmission lines against the voltage waves reaching there.The most common device used for protection for the power system against the high voltage surge diverter, which is connected between the line and the earth. So divert the incoming high voltage wave to earth. Such a diverter is also called L.A. It acts similar to a safety valve. As soon as the voltage again comes to normal value, it stops the flow of current.

TYPES OF LIGHTENING ARRESTOR

Rod gap type:It is simple but used rarely due to that it does not fulfill the basic requirement of a true protective device. It does not cut off power voltage after it has flashed over a surge.

Expulsion type:In this type a spark gap is enclosed in a fiber tube and another external ordinary spark gap is in the air. On occurrence of a high voltage the two spark gap breakdown occurs at once establishing a conduction path in the form of an arc, & it becomes a short circuit on the network.Used in C.P.H. G.S.S.

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Lighting arrester

Burj lighting arrestor

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Lighting arrester on transformer

Conventional valve type:It comprises of a divided spark gap in series with the resistance element having nonlinear characteristics. The normal power frequency system voltage can cause break down on the arrival of an over voltage of appropriate magnitude the device becomes conductive and spark gap cannot on their own interrupt the follow current due to power frequency system voltage.

Disc type or thyrite type:This type of L.A. has basic cell made of thyrite, which is a particular type of clay material mixed with carborundum. Thyrite has a remarkable property of being practically an insulating material.A standard cell is rated for 1 KV and is formed into a disc which is sprayed on both the sides to give a good contact with each disc.

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LOCATIONS OF LIGHTENING ARRESTOR

The location of LA plays an important role in the GSS. Generally these are on the right terminals of the transformer. The L.A. may be installed at a distance less than the maximum possible from the t/f.

CHARACTERISTICS OF LIGHTENING ARRESTOR

1. STABILITY: It should remain in operation during normal conditions even under polluted atmosphere.

2. RESPONSE: Protective device should have means of sensing the transient appearing across its terminals very quickly.

3. PROTECTION: After passes the surge current the power frequency current which is called “power flow current” through the arrestor.

POTENTIAL TRANSFORMER

T/F s used for voltage measurements are called “voltage transformers” or “potential transformers”

These t/f s make the ordinary low voltage that is suitable for measurement of high voltage and isolate them from high voltage.

The primary winding of the PT is connected to the main bus bar of switch gear installation and to the secondary winding various indicating and metering instrument and relays are connected.

When the rated high voltage is applied to the primary of P.T. the voltage of 110 volts appears across the secondary winding.

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High voltage transformer

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Primary rating 132KVSecondary rating 11KVPower 20MVAFrequency 50Hz

ROUTINE TEST FOR POTENTIAL TRANSFORMERS

Verification of terminal marking & polarity. Power frequency test on secondary winding& primary winding for

capacitive P.T. High voltage power frequency test Accuracy test at rated frequency Setting of protective gap

IMPORTANT FEATURES OF A VOLTAGE TRANSFORMER

o Absolutely airtight fully sealed construction:In the hermetic t/f a synthetic rubber diaphragm completely separates the oil from the ambient air. On account of its corrugated construction this diaphragm can follow the changes in volume of the oil without producing the slightest increases of internal pressure in the equipment. The equipment is hermetically sealed after processing in the factory so as to preclude any contact with the external air & any ingress of moisture is likewise rendered impossible. Thus, in service, the oil retains the same dielectric strength as that obtained under factory conditions(300-350 KV per cm). This type of sealed construction eliminatesthe need for extraction of samples of the oil for analysis.

o Cascade connection of the primary coilsThe cascade construction used in the hermetic voltage t/fs, separates the primary winding into several coils. The secondary winding or windings are fitted on the last coil only a proportion of the voltage. Furthermore, the

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rectangular core on which the coils are mounted is connected to the mid-point of the primary winding& is thus raised to a potential mid-way b/w that of the high voltage & earth.

o Use of anti-resonant winding techniqueThis technique consists of winding a single layer of turns over a greater possible length of the coil & then returning with a further layer of turns after having insulated this from the first layer by the insertion of an insulating material. This attenuates the influences of the capacities in parallel between the layers of windings & earth,to the benefit of the cities in series between individual layers of the winding. In this way a linear distribution of the voltage within winding is achieved,both under transient conditions (by means of the capacitive component) & under steady-state conditions (by means of the inductive component). In this way it is possible to eliminate all electrical resonance effect which could arise within the windings in the oscillating circuit which is made up of the inductive & capacitive portion of a HV winding.

o Porcelain insulators with long leakage pathThe column insulators used with the hermetic instrument t/fare provided with an increased number of skin. These results in a ratio of developed leakage path to insulating voltage of the order of 2.7 cm per KV, whereas the insulators employed do not generally achieve 2 cm per KV. The insulators fitted to the hermetic t/f s can be used without hesitation under conditions of highest atmospheric pollution & greatest saline content whilst only need maintenance at infrequent intervals.

o Problems of corrosion,connection & oil tightness effectively resolvedThe base &the trolley (supplied on request, extra price) are, in fact, made of steel & are protected by hot galvanizing. On the other hand hermetic cover,the mounting flanges & the terminal box are made of the light alloy with an anodized protective finish. The hermetic of the t/f is protected by

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means of a PVC plated aluminium skin. Finally all screws, bolts, etc., are made of corrosion-resistant alloy (Cupronickel).

CURRENT TRANSFORMERS (C.T.)

These instrument t/f s are connected in A.C. power circuit to feed the current coils of indicating & metering instrument (ammeters, watt-meters, watt-hour meters) & protective relays. Thus the circuit broadens the limits of measurements& maintains a watch over the current flowing in the circuit& over the power loads.

The current t/f basically consists of iron core which are wound by a primary & one or two secondary windings.

The primary is directly in the power circuit (the circuit in which current is to be measured) & to the secondary winding or windings the indicating & metering instruments & relays are connected. When the rated current of CTs flows through its primary winding of 5 ampere will appear in its secondary winding.

The primary winding is usually single turn winding& the number of turns on secondary winding depends upon the powercircuit current to be measured. The larger is the current to be measured, more is the number of turns on secondary. The ratio of primary current & secondary current is known as transformation ratio of the CTs.

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Current transformer

Primary rating 11KV to 33KVSecondary rating 110VCT: primary rating 2.5A to 300A Secondary rating 1A, 5A

CIRCUIT BREAKER

A C.B. is a piece of equipment which can break a circuit automatically under fault condition & make a circuit manually or by remote control under fault condition.

REQUIREMENT OF A CIRCUIT BREAKER

These are following:

It must safely interrupt the normal working current as well as the short circuit current.

After occurrence of fault the breaker must isolate the faulty circuit as quickly as possible.

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It must have sense of discrimination. It should not operate when an over current flows under healthy conditions.

MAIN COMPONENTS OF CIRCUIT BREAKER

1. C.B. contacts2. Bushings3. Bus bars & conductors4. Instrument t/f

TYPES OF CIRCUIT BREAKER

(1) OIL CIRCIUT BREAKER These are one of the oldest type of C.B. The separating contacts of the breaker are remade to separate within insulting oil.The bubbles of the gas formed prevent re-striking of the arc after the current reaches zero point of the cycle. The type of oil C.B. used is “Bulk oil circuit breaker”.

Oil circuit breaker

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Rated Symmetrical Breaking Current (RMS) capacity

18.4KA

Type MOCBRated voltage 12KVRated current 800A

(2) VACUUM CIRCUIT BREAKER

Vacuum C.B. is a gang operated, triple pole C.B. fitted with vacuum interrupters. It is suitable for direct connections to overhead supply lines.In this type of C.B. the quenching medium is vacuum instead of oil. The vacuum to interrupters is mounted in a porcelain insulator to form an interrupter assembly. There such assemblies are mounted on a base frame which has a common operating shaft. This assembly is mounted on a steel structure instead to locate the line terminals at a safe distance above the ground. The structure also encloses the operating mechanism. The breakers can be electrically operated from control room or by hand locally. There shall be spring charger to charge the spring offer every one operation of breaker. The spring charged can either by manually or by means of electric motor.

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33KV vacuum circuit breaker

Rated voltage 12KVRated current 1250ARated Symmetrical Breaking Current (RMS) capacity.

25KA

Operating Sequence. 0-0.3sec.

CO-3 min. -CO

(3) SULPHUR HEXAFLURIDE CIRCUIT BREAKER(SF6,CB) The latest design for A.C. C.B. is SF6 gas type. In which SF6 gas works as quenching medium as well as insulating medium.

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SF6 circuit breaker

Rated voltage 132KVDielectric test(kv/rms) 308Breaking capacity(ka/rms) 50

CONTROL CUBICLEEach triple pale C.B. is improved with cubicle which consists of

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(i) ON/OFF indicator(ii) Local remote selector switch(iii) Pressure gauge(iv)STOP/DRAIN valve(iv) Pressure switch block closing/opening/reclosing in the event of low

pressure(v) Heaters(vi) Operation counter

SAFETY SUPER DEVICE Gas density monitor Pressure switch Phase discrepancy switch Anti humping device Mechanical close interlock Pressure switch for low pressure alarm switch

TECHNICAL DATE

PARICULARS PVN12 PVN36Rated voltage KV 12 36Rated normal current A 630/1250 1250/1600Rated power frequency withstand voltage

KV 28 170

Rated lightening impulse withstand voltage

KVp 75 170

Rated short circuit breaking current KA 13.1/26.3/31.5 25Rated short time withstand current KA 13.1/26.3/31.5 25/40Duration Sec 3 3/1Rated short circuit making current KAp 33.4/63/80 63/100Rated duty cycle 0.03 sec-CO-3

min-COO:opening

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C:closedRated aux supply for spring charging motor

230 VAC

Motor rating 750 WattsRated supply voltage for trip/ close coils

24/30/110/220/250 VDC

Power required for trip/ close coils 100/200 Watts

Applicable standards IS:13119/IEC:56

POWER TRANSFORMER

Power transformer is a static device used in transmission & distribution system to set up & step down A.C. voltage.

Principle: The principle of a transformer is explained by Faraday’s law of electro-magnetic induction, which states “an e.m.f. is induced in a closed magnetic circuit whenever there is a change in the magnetic flux linkage of that circuit; the induced e.m.f. is proportional to the rate of change of flux linkage.”

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Dry type power transformer

Rated capacity 30-2500KVARated high voltage 3-15Kv

Working: When the primary winding is connected to an A.C. source, an exciting current flows through the winding. As the current is alternating it will produce an alternating flux in the core linked by both the Primary & Secondary Windings.

The induced e.m.f. in the primary winding is almost equal to the applied voltage & it will oppose it. The e.m.f. induced in the secondary winding.

Winding can be utilized to deliver power to any load connected across it. Thus power is transferred from primary to secondary winding by “electromagnetic

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induction”. The magnitude of the e.m.f. induced in the secondary depends upon its no of turns.

PARTS & FITTINGS OF THE TRANSFORMER

Core: It is used to provide closed magnetic coupling b/w L.V. & H.V. coils & to reduce leakage flux & to provide low reluctance path. Core is made of laminated magnetic material. The material is generally in the form of laminated Silicon alloy steel. Silicon risks the permeability at low flux density, reduces hysteresis loss & eddy current loss. Each lamination is coated with thin layer of insulation varnish.

Winding:Winding of a t/f that is L.V. & H.V. winding are attached on the limbs. They are made up of copper. Cylindrical, concentric winding are used for core type t/f for L.V. & H.V.

Tank & tank cover: Inside the tank oil is filled & the core is placed. The tank cover is used to prevent the entry of dust particles & external impurities.

L.V. & H.V. bushings: Bushings comprises of a central conductor surrounded by graded insulation. A bushing is necessary when a conductor is taken out through a metallic tank.

Tap changer: Adjustment of voltage is done by changing the effective turns ratio of the system transformer by proper selections of tappings on the winding. There are 2 types of tap changing:

(i) OFF LOAD TAP CHANGING(ii) ON LOAD TAP CHANGING

In the first form as none implies it is essential to switch off the t/f before changing the tap. On load tap changers are employed to regulate voltage while t/f is delivering normal load.

Tap changers are provided on the outer winding or moreover the H.V. side has number of turns. During transition two adjacent taps are momentarily

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connected & the short circuit is limited by the automatic insertion of impedance b/w the corresponding tapping.

Carriage: it is used to move the t/f when it is to be installed or is to be taken to repair.

Jacking or lifting lugs: they are used to lift the t/f.

FITTINGS Radiator: It is used for cooling purpose of the insulating oil. Pressure relief pipe or vent pipes: It is a cylindrical steel pipe whose one

end is connected to the main tank through the bolts & the other is connected to diaphragm (thin glass plate). It prevents the tank from bursting when excessive gas gets collected in the tank.

Breather: If the moisture enters the t/f then the dielectric strength of the oil reduces. The breather absorbs the moisture from the conservator. It is connected to the conservator. It consists of crystals of silica gel. Dry cell gel is of blue color. Moist silica gel becomes pink.

Arching horn: To prevent the t/f from lightening & excessive voltage & to send the current obtained from this to earth, two rods of horn shape are fitted on the voltage bushing.

Oil gauge: It is used to note the oil level in the conservator tank. Pressure gauge: It is used to note the pressure inside the tank. Oil temperature indicator: It indicates the temperature of the oil inside the

main tank of the t/f. Winding temperature indicator: It indicates the temperature of the

windings of the t/f. Oil level indicator: It indicates level of oil in the conservator tank & also

show the level of oil according to temperature.

BUCHHOLZ’S RELAY

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The t/f is fitted with double float buchholz’s relay. It is fitted in the feed pipe from conservator to tank & is provided with two set of mercury contacts. The device comprises of a cast iron housing containing the hinged floats. One is upper part & the other part is the lower part. Each float is filled with a mercury switch leads of switch are connected to a terminal box.

Buchholz relay inside the transformer

3=conservative tank, 4= Magnetic Oil Level Gauge, 8= Silicagel Breather, 12= Top Filter Valve , 13= Drain Valve, 18= Rating & Diagram Plate

This alarm detects minor or major faults in the t/f. The alarm element will operate after specified volume of gas has collected to five an alarm indication. Such faults are :-

Broken down core-bolt insulation Shorted laminations Over heating of parts

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The alarm element will also operate even there is oil leakage or if air gets into system.

CONSERVATOR TANK

As the temperature of oil increases or decreases during operation there is a corresponding rise or fall in the oil. To account for this an expansion vessel (conservator) is connected to the t/f tank. The tank has a capacity of oil level equal to 75% of the total oil in the t/f. This is provided with the magnetic oil gauge on one end covers with a low oil level alarm. The low oil level alarm is suitable for 240 V D.C. or A.C. a prismatic oil gauge is also fitted at the other end. A valve is fitted at the lowest point of the tank for draining & sampling of oil. On the feed pipe “ Buchholz’s relay” is mounted.

MAINTAINANCE SCHEDULES.No. Item to be inspected Inspection notes Actions required

HOURLY

1. Ambient temperature Check the temperature rise is reasonable

Shutdown the t/f, investigate if either is persistently higher than normal

2. Winding temperature

3. Oil temperature

DAILY

1. Oil level in t/f Check oil level from oil gauge

Top up if found low

2. Oil level in tap changer diverter switch

Check oil level from the gauge glass

Top up if found low

3. Oil levels in bushings Check oil level from Top up if found low

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the gauge glass

MONTHLY

1. Buccholz relay Check oil level Release collected gas/air

2. Dehydrating breather Check color of silica gel

Reactive/replace with new charge, it found

QUATERLY

1. T/f oil & tap changer oil Check for dielectric strength & moisture content

Take suitable action to restore quality of oil

2. Cooler fan bearing & control pumps

Check contents manual control & interlocks

Lubricate the fan bearing clean/adjust control

3. Dehydrating breather Check oil level in the cup & ensure air passages are free

Top up if found low clean air passages

YEARLY

1. T/f oil Check for characteristics in with IS: 1866

Filter/replace as required to restore the quality

2. OTI & WFI pockets Check oil in the WTI & OTI pockets

Replenish if required

3. Earth strips Check earthing resistance

Take suitable action

4. Packing gaskets of tans Inspect the condition of packing gaskets

Replace if worn out or resilience lost

5. Gasket joints Check the tightness of Tighten evenly all

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bolts loose bolts nuts locking etc.

6. Diverter switch oil Filter oil irrespective of strength

Replenish with new oil

7. Tank cover & conservator Dust dirt surface Clean touch-up painting

8. Bushing top connectors Check contact joints RetightenTWO YEARLY

1. T/f oil Examine values as per IS: 1866

Filter oil if required

2. Buccholz relay Mechanical inspection Set floats if required

SPECIFICATIONS OF POWER TRANSFORMERS

TRANSFORMER NO.1

Make Transformers & Rectifiers (India) Ltd.Voltage ratio 132/11 KVSerial no. 220066Capacity 16/20 MVAHigh voltage (HV) load 69.98/87.48 ALow voltage (LV) load 839.78/1049.73 APercentage (%) impedance Max. (10.29)

Nor. (10.05)Min. (9.30)

Weight of oil 13000 kgTotal weight 52000 kgYear of manufacture 2010Oil quantity 14600 litersVector group refer. YNyn0Type of cooling ONAN/ONAF

TRANSFORMER NO.2

Make Transformers & Rectifiers (India) Ltd.

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Voltage ratio 132/11 KVSerial no. 220064Capacity 16/20 MVAHigh voltage (HV) load 69.98/87.48 ALow voltage (LV) load 839.78/1049.73 APercentage (%) impedance Max. (10.49)

Nor. (10.25)Min. (9.51)

Weight of oil 13000 kgTotal weight 52000 kgYear of manufacture 2009Oil quantity 14600 litersVector group refer. YNyn0Type of cooling ONAN/AONAF

TRANSFORMER NO.3

Make GEC ALSTOMVoltage ratio 132/11 KVSerial no. B-29372Capacity 16/20 MVAHigh voltage (HV) load 87.5 ALow voltage (LV) load 1049.7 APercentage (%) impedance 10.534Weight of oil 11.3 TONNESTotal weight 440 TONNESYear of manufacture 1977Commissioned on 14.08.1999Oil quantity 13000 Liters

Year of repair 1999 (by G.E.C.)

TRANSFORMER NO.4

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Make CROMPTONVoltage ratio 132/11 KVSerial no. T-8543/1Capacity 16/20 MVAHigh voltage (HV) load 69.0/87.5 ALow voltage (LV) load 830.8/1049.7 APercentage (%) impedance 9.58Total mass 46 MTYear of manufacture 1999 TN- 2414Commissioned on 29.09.1999Oil quantity 13000 Liters

TRANSFORMER NO.5

Make Transformers & Rectifiers (India) Ltd.Voltage ratio 132/33 KVSerial no. 01572/144PCapacity 40/50 MVAHigh voltage (HV) load 174.95/218.69 ALow voltage (LV) load 699.82/874.77 APercentage (%) impedance Max. (12.86),Nor. (12.70),Min. (11.74)Weight of oil 20500 kgTotal weight 87500 kgYear of manufacture 2005Oil quantity 23000 litersVector group refer. YNyn0Type of cooling ONAN/AONAFCommissioned on 28.12.2005T N No. 2681

TRANSFORMER NO.6

Make Transformers & Rectifiers (India) Ltd.

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Voltage ratio 132/33 KVSerial no. 200-06.3/144PCapacity 40/50 MVAHigh voltage (HV) load 174.95/218.69 ALow voltage (LV) load 699.82/874.77 APercentage (%) impedance Max. (13.01),Nor. (12.88),Min. (11.77)Weight of oil 20500 kgTotal weight 87500 kgYear of manufacture 2006Oil quantity 23000 litersVector group refer. YNyn0Type of cooling ONAN/AONAFCommissioned on 07.03.2006TN No. 2681

DISTRIBUTION OF ENERGY

CHAMBAL POWER HOUSE: There are various transformers as mentioned in the table given below.

S.No. No. of T/F CAPACITY TYPE MAKE1. 01 16/20 MVA 132/11 KV T/F s & RECTIFIERS (I) Ltd.2. 02 16/20 MVA 132/11 KV T/F s & RECTIFIERS (I) Ltd.3. 03 16/20 MVA 132/11 KV G.E.C. ALSTOM4. 04 16/20 MVA 132/11 KV CROMPTON5. 05 40/50 MVA 132/33 KV T/F s & RECTIFIERS (I) Ltd.6. 06 40/50 MVA 132/33 KV T/F s & RECTIFIERS (I) Ltd.

There are 7 (33 KV) & 12(11 KV) outgoing feeders from CPH. They are:

S.No. T/F No. CAPACITY TYPE O/G FEEDERS FROM T/F

1. 01 & 02 16/20 MVA 132/11 KV (A) RAM NIVAS BAGH-I(B) NIRMAN NAGAR(C) MAHESH NAGAR

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(D) NEW SANGANER ROAD(E) RESIDENCY(F) ESI

2. 03 & 04 16/20 MVA 132/11 KV (A) RAM NIWAS BAGH-II(B) QUEEN’S ROAD(C) AJMER ROAD(D) KHASA KOTHI(E) 22 GODAM(F) LAL KOTHI(G) GANDHI NAGAR 1(H) GANDHI NAGAR 2(I) JAMUNA NAGAR(J) N.B.C.(K) PRATAP LINES

3. 05 & 06 14.6/20 MVA 132/33 KV (A) KHASA KOTHI(B) DURGAPURA(C) MNIT(FORMER MREC)(D) LAL KOTHI(E) E.S.I.(F) SEWAGE FARM(G) BISALPUR(H) 22 GODAM(I) VIDHAN SABHA

TRANSFORMER PROTECTION

If the electric transmission & distribution system is like as a human body then a transformer is as a back bone in human body. So protection for a transformer is necessary.

The following protections are provided to a power transformer mounted at G.S.S.

Over current protection Earth fault protection

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Differential protection Over pressure protection Temperature over rise protection Winding temperature rise protection Oil temperature rise protection Buccholz’s protection Over voltage protection

(A) OVER CURRENT PROTECTIONWhen the load increases on the transformer, current taken by the transformer also increases in steps. In this situation transformer is said to be in over current position & if this position is maintained for a long period, then there can be dangerous hazard to transformer & obviously there can be damage to lines.So to protect the transformer from over current, there is a relay called over current relay is connected to the transformer, which operates when the transformer gets in the control panel & automatically the circuit breaker opens & cut off the transformer from mains. This relay is energized by 110 V d.c. coming from the battery room.

(B) EARTH FAULT PROTECTIONWhen from any reason, the winding insulation or conductor insulation break’s down, then bare conductor touches metallic part spreading current in the whole of the metallic body. If anybody touches it in this condition, then there maybe a great electric shock to the human body. This fault is called earth fault. In earth fault condition the potential difference between phase & earth becomes zero.

(C) DIFFERENTIAL PROTECTIONThe operation of relay is dependent on the difference in magnitude or phase of current or voltage. For this purpose two current transformers are

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used at both ends of the system to be protected. These transformers have same ratio of transformation & their secondary are inter-connected.For this protection is also relay used which is connected in parallel with there. It will be observed that this protection is being used for the feeder between the sub stations. Whenever there is a difference in the magnitude or phase in either current or voltage between the input & outputs of transformers, relay operators & gives a signal to the C.B. to be operated providing protection to the transformer.

(D) OVER PRESSURE PROTECTIONWhen knows that a transformer is fitted up with transformer oil. This oil is filled in a particular pressure. When there is any heating in winding oil, gas formation develops which the pressure in the tank. Tank is made for a definite pressure to be tolerated.If the pressure increases from this definite valve, there can be a danger to transformer from over pressure situation there is a pressure relief valve is used at the top of the tank. Whenever the pressure exceeds, this valve operates or opens providing free exits of a formatted gases so that over pressure can be converted into normal pressure & escape the tank from over pressure.

(E) TEMPERATURE OVER RISE PROTECTIONThis type of protection protects the transformer from the overheating of transformer’s winding & oil. So this protection is called over temperature rise protection.As the current flows through the winding, there is a IR losses takes place in winding resulting in the heating of winding. Whenever the transformer is over loaded, over heating of transformer oil &winding becomes. If this over heating will not be compensated by any source then there can be burning of winding or failure of the insulation. If the insulation of winding fails, then there may be short circuiting between winding turns.

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So to protect the transformer & to compensate the overheating, there are two types of coolings are used :

(i) OIL NATURAL AIR NATURAL(ONAN)This type of cooling is done by providing radiators on the outer part of transformer & by providing conservator tank over transformer. When transformer’s oil is over heated, its volume is increased & spreads through the radiators & conservators. This overheated oil is cooled by the external air blowing. There is no relay used for this protection.

(ii) OIL FORCED AIR FORCED (OFAF)This type of protection is done by a centrifugal pump when temperature over rises, then pumps operates automatically which churns the oil, resulting in the temperature down of oil & hence the whole temperature down, providing protection to the transformer from overheating.

(F) DISTANCE PROTECTIONDistance protection is a resistance dependant time graded protection. The operating time of which is determined by the distance to the fault. This protection is used for transmission lines. It is a non unit type protection & is simple to apply. It can be used as a primary & back-up protection.Distance relays are double acting quantity relays with one coil energized be current. The torque develops is such that when V/I reduces below a set value, the relay operates during a fault on a line. The fault current increases & the voltage at fault point reduces. The ratio V/I is measured at the location of CT’s & PT’s. The voltage at VT location depends on the distance between the VT fault. If fault is nearer, measured voltage is lesser. If fault is farther, measured voltage is more. Hence assuming constant fault

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resistance fault resistance each value of V/I measured from relay location corresponds to distance between the relying point & the fault. Hence such protection is called “impedance or distance protection”

(G) BUCCHOLZ’S PROTECTIONIt is gas & oil actuated protection and is used practically in all oil immersed transformers with the exception of smaller distribution transformer. The device relies on the fact than an electrical fault inside the transformer tank is accompanied by generation of gas & if the fault current is high enough by a surge of oil from the tank to the conservator.

(H) RELAY PROTECTIONEach electrical equipment needs protection. The relays are compact, self contended device which response to an abnormal condition. The components at a substation, which are provided with the protection schemes, are(1) Power transformer protection(2) Transmission line feeders (3) Shunt capacitors banks

POWER TRANSFORMER PROTECTION: a power transformer may be subjected to following faults.

(a) Overload & external short circuit(b) Terminal faults(c) Winding faults(d) Incipient faults

TRANSMISSION LINE FEEDERS PROTECTION: the different protection scheme for transmission lines in the following

1) Differential relaying2) Distance relaying

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OPERATION

In case a fault occurs, gas bubbles are generated in the transformer tank, an account of increased heating produced by fault currents. These bubbles rise & go towards the conservator. The gas bubbles are trapped in the upper part of the relay chamber & since the chamber is full of oil is displaced which lowers the top float. The float sinks ultimately thereby causing the closure of contacts of the alarm circuit.

CONTROL ROOM

There is a “Control Room” in the “CHAMBAL POWER HOUSE” in which “Control Panel” are present. All the connections of the transformer &feeder’s are done here from “Remote Operation”. These panels operate by DC supply. From this I/C & O/G supply is connected. The “Control Cables & Conduit System” is required for affecting automatic controls. The cable system generally operates at 110 V or 220 V. For laying these cables generally, ducts run from “Control Room” basement to centrally located ”Junction Box” from where the conduits are send to the required points. For providing D.C. voltage 55 dry cells connected in series. There is a separate room or ”Battery Room” for having these batteries.

Concepts of:1. CONTROL WIRING

AIM: to understand “control wiring” From the fig on the next page we can easily understand the concept of “control wiring”

2. CONTROL & RELAY PANEL

AIM: the figure of “control & relay panel” is show on the next page.

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BATTERY ROOM

There is a battery section or battery room, which has 55 batteries of 2 Volts each. Therefore total DC power available is 110 V for functioning of the control panel. A battery charger is there to charge the battery.

ABBREVIATIONS

S.No. SYMBOL NAME1. S.L.D. Single Line Diagram2. K.V. Kilo Volts3. G.S.S. Grid Sub-Station4. C.P.H. Chambal Power House5. I/C Incoming Lines6. O/G Outgoing Lines7. N.P.H. Nalah Power House8. C.T.s Current Transformers 9. P.T.s Potential Transformers10. L.A. Lightening Arrestors11. C.C. Coupling Capacitor12. C.V.T. Capacitive Voltage Transformer13. P.L.C.C. Power Line Carrier Communication14. INS Insulators15. ISO Isolators16. R.V.T. Residual Voltage Transformer17. C.B. Circuit Breaker18. B.O.C.B. Bulk Oil Circuit Breaker19. O.C.B. Oil Circuit Breaker20. SF6 Sulphur Hexa Flouride

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21. V.C.B. Vacuum Circuit Breakers22. O.L.T.C. On Load Tap Changer23. L.V. Low Voltage24. H.V. High Voltage25. T.S.M. Time Setting Multiplier26. P.S.M. Plug Setting Multiplier27. O.T.I. Oil Temperature Indicator28. W.T.I. Winding Temperature Indicator29. T/F Power Transformer30. Winding Winding31. Circuit Circuit32. E.S.I. Employee state insurance33. a.c. Alternating current34. b/w Between

REFERENCE

-Materials provided by Mr. R.K Sharma(Assistant Engineer, in 132KV;G.S.S. Chambal, R.R.V.P.N.L,Jaipur)

- http://en.wikipedia.org/wiki/Power_station

- http://www.google.co.in/

-JB Gupta -Sunil S Rao

Project Report on

132KV G.S.S.Chambal Sub Station

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http://www.google.co.in/

http://en.wikipedia.org/wiki/Power_station


Department Of Electrical Engineering

Malaviya National Institute Of Technology Jaipur

Submitted By :

Md. Shahim Raeen VII SEMESTER

Electrical Engineering

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contents

Sl. No. Topics Page No 1 Introduction 2-32 Necessity components for sub station 3-43 Equipment available in g.s.s jaipur 5-84 Description of equipment in switch yard 9-155 Capacitor bank 15-216 Potential transformer 22-247 Current transformer 25-268 Circuit breaker 26-289 Type of circuit breaker 28-3010 Control cubicle 30-3111 Safety super device 31

12 Technical data 3113 Power transformer 31-3314 Part &fitting of transformer 34-3515 Buchhlog relay 35-3616 Conservator tank 3717 Maintainance schedule 38-3918 Specification of power transformer 39-4219 Distribution of energy 42-4520 Transformer protection 43-4721 Operation 4822 Control room 48-4923 Battery room 49-50

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Chambal Power House (c.p.h) Yard

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Transcript of Chambal Power House (c.p.h) Yard