Electrical 42 Pages

7/29/2019 Electrical 42 Pages

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on

panipat thermal power station

(a unit of h.p.g.c.l., haryana)

submitted in partial fulfillment of the requirement for the

award of degree in

electrical engg.submited to : prepared by:

____________ ___________

____________ ___________Page | 1


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in every step of achiving any concert, there is need

of guidence, inspiration & help for better result.

i am hereby thankfull to following persons for not

only their valuable instructions that they given me

to prepare this project report but also for their

cooperation during training period.

1. er. ______________________/xen trg

2. er. ______________________

3. aee______________________

4. j.e . ______________________

i am equally thankful to all other workers who

tried their best to help me & provided me

informations required for training and my friends

who directly or indirectly helped me for completion of this projectreport.

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index

* introduction

* functional description

* 6.6 kv supply system

* motorh.t.motorsl.t motors

* transformers

* switchyard components

* turbo generator

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introduction

the salient features of the plant are as under:

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capacity 4x110mw+2x210mw+2x250mw

unit-1 01-11-1979

unit-2 27-03-1980

unit-3 01-01-1985

unit-4 11-01-1987

unit-5 28-03-1989

unit-6 04-07-2001

unit-7 16-10-2004

unit-8 02-02-2005

daily coal req. 15,000m.t.

height ofcooling

towers

123.5 mtr. in stage 1&2143.5 mtr. in stage 3&4

140 mtr. in stage 5&6


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functional description

the thermal power station burns fuel & uses the resultant tomake the steam ,which derives the turbo generator. the fuel i.e.coal is burnt in pulverised form . the pressure energy of thesteam proudced is converted into mechanical energy with thehelp of turbine . the mechanical energy is fed to the genertorwhere the magnets rotates inside a set of stator winding & thuselectricity is prouduced. in india 65% of total power is generatedby thermal power stations. to understand the working of thethermal power station plant ,we can divide the whole process intofollowing parts :

1.coal flow:

in coal fired plants, raw material are air &water .in ptps ,coal istransported through railway wagons from m\s. coal india & iskept reserved on a buffer stock .the brought out to the station isunloded with the help of wagon tippler .after unloading ,the coalis sent to crusher house with the helpof conveyor belts. the coalwhich is now resuced to very small pieces,is sent to the coalbunkers with the help of conveyor belt .the raw coal is fed to coalmills through raw coal feeders . raw coal feeders basicallyregulate raw coal to pulverise mill. the raw pulverised coal is fedto the furnacewith the help ofprimary fan through pulverisedcoal pipes .a porition of the primary air is heated utilising theheat of the flue gases & then mixed with the cold air as perrequirement by the pulverised coal. normally the temp. of ismaintainedat 60 to 70 degrees .the coal is now burnt in thefurnace using oil in the beginning, showerd through the nozzlesat different elevations in the furnace .to provide air for

combution ,the heat of the flue gases also heat it. the heatproduced due to combution is utilised for the conversion of waterinto steam .this water is stored in the boiler drum .there are twosets of pipes attached to the drum ,one called riser& other knownas down corner through which the water comes to the ringheader& steam moves up due to the density difference of water & steam .

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this steam is super heated using super heaters & meanwhile the fluegases are throughout in the atmosphere through chimney.

2. steam flow:

the super heated steam is sent to the turbine throughpipelines.there are three turbines in the units, using this steam atdifferent temp. & pressures. after passing through high pressureturbine the steam is sent to the reheaterfor rising the temp. of thesteam.after reheating the steam is sent to the intermediate pressureturbine through reheated line. here it losses most of its temp. &pressure, & finally sent to low pressureturbine. the uses of threedifferent turbines helps in increasing theefficiency of the plant. the

turbine in turn connecting with a generator produces electricity. thenthis electricity is stepped upto 220 kv with the help of step uptransformer & supplied to various substations/grids.

meanwhile, the steam through low pressure ( l.p.) turbine iscondensed and the condensed water is stored in hot well.

3.water flow:

the condensed water is extracted from the hot well throughcondensate extraction pumps & sent to the boiler drum with the help ofboilerfeed pump (b.f.p.) before passing through low pressure heater anddeareter. while loss in water is made up from c.s. tank, which have d.m.moor in it. the c.s tank is directly conneced to hot well.

the water used in condensor is sent to cooling tower for cooling .after cooling this water is again sent to condensor with the help ofcirculating waterpump. the loss is made up from raw water pump housethrough calorifier pump house.

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boiler feed pump

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brief explanation

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1.wagon tippler:-it is the machine which is used to tip the coalfrom the wagon . the coal tipped is directly fed to conveyor belt. itscapicity is 12 wagon per hour .

2.crusher:-it crush the coal into small pieces.

3.coal mills:-in it small pieces of coal are converted intopulverised form. they are 6 in number.

4.furnace:-it is the chamber in which fuel burns & fire blows.

5.boiler drum:-it contains water for boiling.

6.electrostatic precipitator:-in this we have electrodes whichattracts fly ash and extract it from flue gases so that it can notenter atmosphere.

7.chimney;-it is used to release flue gases into the atmosphere.

8.turbine:-turbine is the part which revolves due to steampressure.it is of three types:

a).high pressure turbine

b).intermediate pressure turbine.

c).low pressure turbine.

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9.turbo generator:-it is the main machine which produces 210mw electricity. it is water and h2(hydrogen) gas cooled.therefore it is contained in cylindrical chamber.

10.condensor:-it condense steam coming from low pressureturbine(l.p.t.) to hot water.

11.cooling water (c.w.) pump :-this pump send water fromcooling tower to condensor.

12.cooling tower:-it is used to cool the water its height is near

about 143.5mtr.

13.raw water pump house :-it supplies raw water to the boiler.

14.clearifier pump house:-the water from raw is cleared atclearifier by putting alum in it & filtering it & then supplied to thecondensor.

15.condensate extraction pump:- c.e.p. pump is used to extractthe condense water from the hot well and supply to the deareaterafter passing through l.p. heater& economisier,so that highpressure steam in the cylinder can be created.

16.low pressure heater:-it is used to increase the temperature ofwater, in this way efficiency of system increases.

17.deareater:-it is used to remove air from water,which isentrapped in the water molecules. it is very important part becausethe entrapped air effect air drum badly.

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18.boiler feed pump(b.f.p.):-it is the heaviest drive in the plant &supply water to boiler drum from deareater.

19.high pressure heater(h.p.):-in this temperature of waterincreases, thus efficiency further increases.

20.economiser:-in this flue gases exchange heat to the water toincrease system efficiency.

general working diagram

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6.6 kv circuit breakera circuit breaker is a device which:-

makes or breaks a circuit either manually or by remote

control under normal conditions.

breaks a circuit automatically under fault conditions.

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thus a circuit breaker is just a switch which can be operated undernormal & abnormal conditions both automatic or manually. toperform this operation ,a circuit breaker is essentialconsisting of fixed and moving contacts called electodes.when a fault occures on power system, the trip coil of circuitbreakeris energised which pulls apart moving contacts, thusopen the circuit dc supply is used for the operation of circuitbreaker.on the basis of medium used for a extinction thecircuit breaker are classified as :

1. oil circuit breakers2. air blast circuit breaker3. sulpher hexafluoride circuit breaker.

oil circuit breakerit is well known that when a circuit carrying a large current isbroken, an arc occurs at that point where the contacts areseparate, the arching is specially severe when high voltages areinvolved and if a short circuit occurs on a high voltage cable whichis supplied from large power station. the arc would be powerfull tobridge the contacts of the switch and destroy it by burning. thedevice is employed as an oil breaker. an oil breaker posses theproperty of always breaking an alternative current at its zero value.

these switches are suitable for a maximum voltage of 6.6 kv. thecontacts of these switches , which breaks high tension circuit, areimmersed in oil to ensure rapid & effective rapture of the circuit.when the arc occurs, the oil in its path is vaporised and the gas

thereby generated extract a pressure on the surrrounding oil. thispressure is utilised in arc controlled devices to cause a movementof fresh cool oil across the path of the arc, thereby efficientlyassisting its interruption.

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specification:-low oil circuit breakertype e7531/10.

1. voltage:- 6.6/11kv2. current:- 3150 a.3. frequency:- 50hz4. short time current:- 50/35ka for 1/3 s5. breaking current:- 44/39.4ka6. weight:- 350kgs

type:- e7512/10.1. voltage:- 6.6/11kv2. current:- 1250a

3. frequency:- 50hzs4. short time current:- 50/40ka for 1/3s5. breaking current:- 44/39.4ka6. weight:- 210kgs

type:- e7525/10

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1. voltage:- 6.6/11 kv2. current:- 2500a3. frequency:- 50hz4. short time current:- 50/35ka for 1/3s5. breaking current:- 44/39.4ka6. weight:- 220kgs

index

incomertieload1250 a circuit breaker2500 a circuit breaker3150 a circuit breaker

iii-a

1.dummy for tie to 5 a2.tie to 5 a3.dummy for tie to c-11-a4.tie to c-ii a5.r.w.t. iii6.f.o.t. iiia7.bus p.t

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8.s.s.t. iiia9.s.b.t. iia10.to c.h.s. iiia11.c.m.8a, 340kw, 325a12.i.d.f.m. 5b, 130 kw, 147.5a13.ash water recovery t/f.14.h.p.w.p.m. iiib, 260kw, 29a15.h.p.w.p.m. iiia, 260kw, 29a16.c.w.p.m. 3c, 1265kw. 140a17.a.h.t. iiia.18.c.l.m.t. iiia.19.b.c.w.p.m. iiib, 135kw, 38a20.b.c.w.p.m. iiia, 335kw, 38a21.incomer

22.dummy for incomer23.tie for unit 6a

iii-b

1. tie to unit 6b2. dummy for incomer 3. incomer 4. b.c.w.p.m. iiic, 335 kw,38a.5. b.c.w.p.m. iiid, 335kw, 38a6. c.l.w.t. iiib7. a.h.t. iiib8. h.p.w.p.m. iiic, 260kw, 29a.9. h.p.w.p.m. iiid, 260kw, 29a.10. h.p.w.p.m. iiie, 260kw, 29a11. spare motor 12. e.p.t.13. c.m. 8b, 340kw, 325a,14. c.h.s.

15. s.b.t. iiib16. s.s.t. iiib17. bus p.t.18. f.o.t. iiib19. b.f.p.m. iiib, 3500kw, 360a.20. tie to c- ii b21. dummy for tie to c ii b

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22. tie to 5b23. dummy for tie to 5b.

index

5( a )

1. u.s.t.-52. e.p.t.-5a3. bus p.t.4. b.f.p.m.-5 a,3500 kw,3605. p.a.f.m-5 a,1250 kw,132 a6. f.d.f.m.-5 a,750 kw,80.2 a

7. p.m.-5 a,340 kw,40.7 a8. p.m.-5b,340 kw,40.7a9. p.m.-5c,340kw,40.7a

10. i.d.f.m.-5a,1300kw,147.5a11. rect. t/f12. c.w.m.-5a,500kw,525a13.c.w.p.m.-5a,265kw,140a14.incomer15.dummy for incomer16.tie to ssiii-a17.dummy for tie to ssiii-a

5(b)

1. dummy for tie to ssiii-b2. tie to ssiii-b3. dummy for incomer 4. incomer

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5. c.w.p.m.-5b,265kw,140a6. c.p.m.-5b,500kw,525a7. 11kw,temporary supply8. i.d.f.m.-5c,1300kw,147.5a9. p.m.-5d,340kw,40.7a10. p.m.-5e,340kw,40.7a11. p.m.-5f,340kw,40.7a12. f.d.f.m.-5b,750kw,80.2a13. p.a.f.m.-5b,1250kw,132a14. b.f.p.m.-5c,3500kw,360a15. bus p.t.16. e.p.t.-5b17. spare motor

motor

A) high tension motor

high tension motors operated at high voltages

in tau devi lal thermal power station, these motors are operated at6.6kv. some of these motors are as follows:-

I. circulating water(c.w.) pump motors:-

a).specifications:-i. maker b.h.e.l.

ii. capacity(k.w.)-1265iii. rated voltage(volts)-6600iv. rated r.p.m.-493v. rated current-140avi. connectins-star vii. duty- continuousviii. insulation class-f

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ix. installation position- verticalx. quantity-3

b).function:- c.w. pump is used to circulate cooling water to the

condensers so that low pressure steam in the cylinder can beconverted into water.

2.c.e.p. pump motor:-

a).specifications:-

make- b.h.e.l.

capacity-500kw

rated voltage-6600v

rated r.p.m.-1482

rated current-52.8a connections-star

duty-(2 working,1standby) continuous

insulation class-f

insulation position-vertical

quantity-3

b).function:-c.e.p.pump is used to extract the condense water

from the hot well and supply to the deareator after passing throughl.p. heater& economisier,so that high pressure steam in thecylinder can be created.

3.boiler feed pump(b.f.p.) motor:-

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a).specifications:-

make- b.h.e.l.

capacity-3500kw

rated voltage-6600volts

rated current-360a

rated r.p.m.-1481

connections- star

duty(2 working,1 standby)-continuous

insulation class-f

quantity-3

b).function:-its function is to supply the water to the boiler drum. it

takes water from the deareator by creating strong suction. it is thebiggest motor in the plant.

4.coal mill motor:-

a). specifications:-

make-b.h.e.l.

rated voltage-6600

capacity-340kw

rated r.p.m.-992

rated current-40.7a

connections- star

duty- continuous

insulation class-f

installation position horizontal

quantity-6

b).functions:-its function is to grind the coal pieces to finepowder (pulverised) form i.e. upto size of 25 micron.

5.coal crusher:-i).make-n.g.f.eii).capacity-600kwiii).rated voltage-6600v

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iv).rated r.p.m.-747v).rated current-72a

vi). connections-starvi).quantity-2

b).function:-its function is to crush the big size coal pieces to a

size of 25mili meter square, which are than carried to bunkersthrough conveyor belt.

6. primary air fan motor:-i).make-b.h.e.l.ii).capacity (k.w.)-1250iii).rated voltag (volts)-6600iv).rated r.p.m.-1487

v).rated current (amps)-132vi).connections-starvii).duty-continuousviii).insulation class-fix).quantity-3

b).function:- its function is to carry pulverized coal from the coalmill to the furnace for its ignition. it creates strong draft of air thatcarries pulverized coal.

7). force draught (f.d.) fan motor:- i).make-b.h.e.l.

ii).capacity-750kwiii).rated voltage-6600viv).rated r.p.m.-1490v).rated current-80.2avi).connection-starvii).duty-continuousviii).insulation class-f

ix).quantity-2 b).function:-f.d. fan is used to supply fresh air to the furnace forthe proper ignition of coal into the furnace.

8). induced draft (i.d.) fani).make-b.h.e.l.ii).capacity-1300kw

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iii).rated voltage-6600viv).rated r.p.m.-750v).rated current-147.5avi).connection-starvii).duty-continuousviii).insulation class-fix).quantity-3b).function:-its function is to discharge flue gases to theatmosphere through the chimney after passing through theprecipitator.

9.bearing cooling water pump motor:-a).specification:-i).make-b.h.e.l.

ii).capacity-335kwiii)rated voltage-6600viv).rated r.p.m.-980v).-connection-starvi).insulation class-fvii).installation position-horizontal

b).function:-it supply cooling water to the motor &other auxillaryfor cooling puposes.& other auxillary for cooling puposes.

B) low tension motor

low tension motors are those which are of 415v. they are mainlyused in h.t.motor auxillary.

1. b.c.w. drain motor:-

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a).specification:-

i).capacity-136kwii).rated r.p.m.-987iii).rated current-43aiv).frequency-50hzv).make-kriloskervi).insulation class-bb)function:-it pump the b.c. water to the sump.

2. seal water pump motor:-

a).specification:-

i). capacity-25kwii). rated r.p.m.- 1479iii) rated current 43aiv) frequency -50hzv). phase-3vi). make ngefvii). insulation class b

b).function it provides a layer of water to the lower position ofboiler in order to seal it from the entry of atmospheric air.

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3. seal water vapour exhaust fan:-

a.)specifications

i) capacity 1.5 kwii) rated r.p.m. 6205iii) rated current 3.1aiv) frequency 50hzv) phase 3vi) make kirlosker vii) insulation class b

a) function- it prevents the entry of air bubbles in the turbinecylinder by providing the opposite push.

4. centrifuge pump motor:-

a). specifications

i). capacity 7.5kw ii). rated r.p.m-1440iii). rated current-14.iv). frequency 50hz

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v). phase 3vi). make crompton greavesvii). insulation class b

b). function to centrifuge the vapour that enters bychange in turbine an remove them

5. ash slurry pump motor:

a).specifications

i) capacity 100kwii) rated r.p.m. 1485iii) rated current 176iv) frequency 50hz.v) phase - 3vi) make ngef vii) insulation class b

b). function to pump ash slurry to the ash disposal area.

6. emergency oil pump:

a). specifications

1. capacity 15 kw2. rated r.p.m. 14253. rated current 1254. frequency n.a. (dc)

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5. phase not applicable

b).function to provide oil to the shaft and bearing of the turbine ifseal oil pump and taking oil pump fails.

7. raw water motor pump:

a) specifications-i).capacity-90kwii).rated r.p.m.-1450iii).rated current-154aiv).frequency-50hzvi).phase-3vii).make-kirloskerviii).insulation class-b

b).function-it is use to pump raw water from the lake to theplant.

8. instument air compressor :-

a).specifications:-i).capacity-105kwii).rated r.p.m-1485

iii).rated current-184aiv).frequency-50hzv).phase-3vi).make- kirlosker

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vii).insulation class- b

b).function- it is used to compress the air used tocontrol pneumatic controlled instruments at a pressure 6 to 7kg/cm cube.

9.service air compressor:-

a). specifications-

i).capacity-30kw

ii).rated r.p.m.-1485iii).rated current-184aiv).frequency-50hzv).phse-3vi).make-ngefvii).insulation class-b

b).function- its function is similar to instrument aircompressor.

10.clarifier water pump motor-

a).specification-i)capacity-30kwii).rated r.p.m-1470

iii).rated current-53aiv).frequency-50hzv).phase-3vi).make-cromptonvii).insulation class-b

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b).function- it pump the filtered water from clearifier to d.m.water treatment plant.

transformers

the transformer is the most convenient & economical devicefor transfer of power from one voltage to another voltage atthe same frequency. it works on the principle of

electromagnetic induction. there is hardly any installationwithout a transformer.due to this equipment,it has beenpossible to transmit bulk power to load centers from far offpower houses and to various machineries and switchgearsof the power plant. transformers are of two types:-

#step-up transformerwhich step-up the voltage atsecondry side called step-up transformer.

#step-down trnsformer- which step-down the voltage atsecondry side are called step-down transformer.

main parts of power transformers

# primary winding# secondry winding# oil tank# drain coke

# conservator# brether# tubes for cooling# trnsformer oil# earth point# explosion vent# temperature gauge

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# buchholz relay# primary terminals# secondary terminals

accessories of transformers

1.oil conservator:-oil conservator is a short of dum mounted

on the top of transformer. a level indicator is fixid to it, which givesalarm at low level. conservator is connected through a pipe to the

transformer tank containing oil. this oil expands & contract dependingupon the heat produced & so the oil level in conservator is left opento the atmosphere through a breather so that the extra air may go outor come in.

2.breather:-the breather is a box containing calcium chloride or

silica gel to absorb moisture of our entering the conservator as it iswell known fact that the insulating property of the transformers oil islost if a small amount of moisture enter in it. so dry air is allowed to

pass through the breather.when oil levrl in oil conservator changes, air moes in

& out of the conservator. this action is known as breathing. dry silicagel is of the blue color. it turns pale pink as it absorbs moisture . thewet silica gel can be regenerated by drying.

3.buchholz relay:-this relay is a gas-actuated relay which is

meant for the protecting of oil immersed transformer from insulation

failure, core heating or any type of internal fault which may cause theheating of oil beyond the specified temp.. due to any internal fault, oilis heated up & oil vapour so formed causeseither the alarmcircuit(for less fault) or trip the circuit(for sever fault).

4.explosion vent:-

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it is also a safety device of the transformerwhich protects the transformer tank from gases induced by & anytype of short circuit in the transformer. this consist of a vertical pipeclosed by a dia pharm made of thin bakelite sheet. this diapharm burst orslides out in case of abnormal pressure inside the tank. a diverter plate isused at the bottom of the explosion vent to ensure that gases proudceinside the transformer are directed toward the buchholz relay & dont getcollected inside the ventilation and equilise the pressure on each side ofthe diverter plate.

5.temp. indicator:-it is also a protective device fitted to the

transformer to indicate temp.of transformer oil. for measuring temp. of theoil, bulb of the vapour pressure type thermometer is placed in the hot oil &

dial of the thermometer is mounted outside the tank. two indicatingpointers black and red are provided. alarm contacts are also providedwhich come into action when predetermined permissible highertemparature is reached under abnormal operating conditions.

6.bushing: the bushing serve as supports and insulation of the bus bars andtransformer terminal. the bushing consists of procelain shell body, upperand lower locating washer used for fixing the position of bush bar and

mounting flange with the hole drilled for fixing bolt and it is supplied with anearthing bolt.

7. maganetic oil gauge:-the maganetic oil level gauge

supervises the level of oil in the conservator tank. the oil level gauge isprovided on the transformer are of dial type with minimum and maximumlevel marking and a pointer which indicate the level of oil in theconservater. sometime the scale is also graduated for oil temperature on

the basis of its level.

8. tap changer:the voltage control of transmission

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and distribution systems is obtained by tap changer. tap changer areeither on load or off load tap changer. tap changer is fitted with thetransformer for adjusting secondary voltage.

important transformers in the plant

1. generator transformer (240 mva, 15.75 kv/220kv)

it converts 15.75 kv which is supplied from generator 220kv andsupplied it to the bus bar/ grid.

2. station service transformer (40mva, 220kv/7kv)

it converts 220kv which is coming to station from bbmb to 7kv and fedto station auxiliary.

3. unit auxiliary transformer (15mva, 15.75kv/7kv)

it converts 15.75kv which is supplied from generator to 7kv to fed unitauxiliary.

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switchyard components

1. switch-gear

switch gear is a control switch thatcontrol the operation of a power circuit. the two fucntion of a switch inpower systems are

i). to permit the transmission lines to be convenient put into and takenout from service.

ii). to disable the some plant and lines when these become faulty, tobe repidly and safely isolated by automatic means.

the first of these can be served by relatively simple switchesthe second however require circuit breakers, which are more robust &capable of breking the large value of fault power that results in faultson major power system. since all plants and lines are liable todevelop faults as a results of mechanical damage, electrical

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breakdown, errors in operation etc. the simple isolators switch infavour of automatic circuit breakers even for switching function. thewhole switchgear assembly consists of two parts:-

a.panel- panel consists of protective relays,mountig of potentialtransformer,current transformer,ammeter,voltmeter & energy meter.the potential transformer is mounted on the panel. the primary isconnected to 11kv & the reduce voltage from the secondary is givento energy meter as line voltages & for protective purposes.

b.trolly- the trolly consists of current carying contacts calledelectrodes. these are normally engaged but in predetermined

conditions, separate to interrupt the circuit, when the contacts aremade.

2 bus bar arrangement

conductors to which a number of circuits are connected called bus bars. in power plants, shut down results dissconection of supply to alarge area. hence to avoid shut down the major plants should have

elaborate bus bar arrangement with duplicate buses, alternativesupply arrangement section etc. the extra high voltage equipmentssuch as isolators, circuit breaker are generally costly henceunnecessary equipment should not be provided.

1. single bus bar arrangement:-the single arrangement consisits of a single (three phase) bus bar

to which various feeders are connected. in case of fault ormaintenance of bus, the entire bus bar has to be de-energisedand the total shutdown results. this scheme is most economicaland simple.

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2. double bus bar arrangement:-the double bus systems provide additonal flexibility, continuityof supply and permit periodic maintenance. in the event of faulton the bus bar the other can be used the figure shows to thebus bar arrangement.there are two buses called main bus andreseve bus . the coupler can be closed so as to connect twobuses while trnasferring the power to the reserve bus.

i) closed bus coupler, the two buses are now at samepotential.

ii) closed isolator on reserve bus.iii) open isolator on main bus.

3 lighting arrester

a lighting arrester is device, which proves low impedence pathfor the flow of current between the line and earth when the systemsvoltage increases more than the desire value and regains its originalproperties of an insulator at normal voltage. it is connected betweenline and earth at the swith yard near the transformer.the lighting arresters are extensively used for protection oftransformers, swith gears and electrical equipments of over head

lines, power houses and sub-station . these are also use to protectthe line and equipments from skylighting.following are the main typeof lighting arresters-

i) horn gap lighting arrester.ii) expulsion type lighting arresters.iii) oxide film lighting arrester.iv) pellet lighting arresterv) thyrite lighting arrester.vi) auto value lighting arrester.

expulsion type lighting arrester

it consists of

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i) a tube made of fibre which is very effective gas evolvingmaterials.

ii) an isolating spark gap ( or external series gap)iii) an intrupting spark gap inside the fibre tube.during operation, arc due to impulse spark or inside the fibroustube causes some fibre material of the tube voltise in form ofgas, which is expelled through a vent from the bottom of thetube, thus extinguishing the arc just like in circuit breaker. sincethe gases generated have to be expelled, one of the electrodeis hollo and diverter is open at its lower end.

thyrite lighting arrester:-

this type of lighting arrester consists of number of discs of

inorganic ceramic compound. these discs are placed in a serieshaving some gaps in between them and are sealed in a procelaintube. this tube has matellic cap and electrodes at its end.the compound used for discs serve as an insulator but chages to agood conductor when voltages across it rises to a certainpredetermined value. it is used upto 220kv systems.

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lighting arrester

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210 mw turbo generator

general:-

modern features of direct cooling by water & hydrogen areincorporated in the 210 mw turbo generator, thus evolve aneconomical & reliable design. the machine is provided with a fastacting excitation system & dependable auxillary service to giveprolonged trouble free operation over the years. all the material thatgoes into the manufacture of this machine subjected to various testas per national & international standards. each compononetsundergoes series of stagewise tests. description of various parts isgiven balow:-

1.stator winding and insulation:-

the stator has a three phase, double layer, short chorded, bar typewinding, having two parallel pats. each coil side consists of glassinsulated solid and hollow conductors with cooling water passingthrough the patter. the elementary conductors are roebel transposed

in the slot poetion of winding to minimise eddy current losses.adequate protection is provided to avoid corona & other discharges.in the slots, the sides are firmly held in the position by fiborousslotwages, which are mechanically strong and have high dielectricproperties. the overhang portion of the coil is securely lashed withglass chord to bondage rings& special breckets of non magneticsteel, which are in turn fixed to the core press rings. on short circuits

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the forces betweenthe conductor tend to open the cone formed byoverhang portion of the coils , but the movement is effectivelypresented by supports & lashings.

2.distillate headers or stator water header:-

ring type water headers, made of copper are provided seperately fordistillate inlet & outlet in the stator on turbine side. the headers aresupported on insulators and isolated from stator body. the windingends are soledly soldered into the coil lugs which are thanultrasonically tested. individual bars are provided with waterinlet/outlet connections made of p.t.f.e. houses. the bar heads areinsulated by fibre moulded corners. the winding scheme along withthe water connections. the complete water path assemblty is

subjected to the rigid hydroatic pneumatic tests at various stages toensure water tightness and to detect blocking of the flows paths.

3.terminal bushings :-

water colled terminal bushings are housed in the lower part of thestator on the slip ring side. procelain insulators are provided toinsulate the terminal bars from the stator body. effective sealing isprovided between the terminal bushingnand the statir bidy to avoidany possibility of leakage of hydrogen. terminal bushing are housedinside a chamber made of non magnetic steel plates. three phaseterminals are brought out to facilitate external connections. theterminal plate of the end terminals, where bus bar connections aremade is silver plated.the terminal bushings can be replaced without removing the statorfrom foundation. provision is made for fixing the external bus ductswith the terminal plate.

4.rotor:-

the rotor is of cylindrical type shaft and body being forged in onepiece from chromium, nickel,molybendum & vanadium steel. prior tomatching, a series of comprehensive ultrasonic examination andother tests are carried out on rotor byody and shsft portion to ensureof any internal defects. the rotor with all the details assembled ,

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dynamically balanced to a high degree of accuracy and subjected to20% over speeding for 2 minutes ensuring mechanical strength.

5.field winding:-the field winding is made from hard drawn silver bearingcopper. rotor winding is held in position against centrifugal forces byduralium forces wedges in the slot portion & by non magnetic steelretaining rings in the over hang portion . gap pick up system isemployed for direct hydrogen cooling of rotor winding. several groupsof ventilation ducts are mulled on the sides of the rotor coil for gaspassage. the rotor slot wedges are of special profiles with ellipticalholes rolled in to match the ventilation ducts on the winding stacks.the end windings are insulated from rings with the help of glass epoxymoulded segments. copper segmental type damper winding is

provided in the end zone of rotor mordws to prevent over heating ofreturning ring s during assymetrical & asynchronous operation.

6.shaft mounted fans:-

for circulating the cooling gas inside the gensrator, two propeller typefans are shaft mounted on this & of rotor body. fan hubs are madefrom alloy steel forging and are hot fitted on the rotor shaft withsufficient interference . the alloy steel cast fan blades are machined inthe tail portion to suit the fan hub and held in position with the help ofconical pins. the blades can be easily removed from or assembled inthe fan hub. fan shields fixed to the end shields, guide the flow of gasthrough the fan sections.

7.slip rings:-

the slip ring consists of hellically grooved alloy steel rings shrunk onthe rotor shaft & insulated from it. for convenience in assembly boththe rings are mounted on a ssingle, common steel bush, which has

an insulated jacket pre moulded on it. the complete bush with slip ringis shrunk on the rotor shafts. the slip rings are provided with inclinedholes for self-ventilation. the helical grooves cut on the outer surfaceof the slip rings improves brush performance.

turbo generator ratings

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capacity in kw- 210000power factor- 0.85capacity in kva- 247000stator:-a).15750 v

b).90.60arotor:-a).310v.

b).2600arotor r.p.m.- 3000frequency- 50hzphase- 3connection- starcoolent- h2+h2ono. of poles- 2

turbo generator

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Documents

Electrical 42 Pages