guru nanak dev thermal power.docx

8/20/2019 Guru Nanak Dev Thermal Power.docx

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Guru Nanak Dev Thermal Power Plant is a coal-based plant. The requirement of

coal for four units based on specific fuel consumption of 0.60 k ! k"h. The conve#in

and crushin s#stem will have the same capacit# as that of the unloadin s#stem. The

coal comes in as lare pieces. This coal is fed to primar# crushers$ which reduce the si%e

of coal pieces from &00mm to '(0mm. Then the coal is sent to secondar# crusher throuh

forward conve#ors where it is crushed from '(0mm to )00mm as required at the mills.

Then the coal is sent to boilers with the help of primar# fans. The coal is burnt in the

boiler. *oiler includes the pipes carr#in water throuh them+ heat produced from the

combustion of coal is used to convert water in pipes into steam. This steam enerated is

used to run the turbine. "hen turbine rotates$ the shaft of enerator$ which is

mechanicall# coupled to the shaft of turbine$ ets rotated so$ three phase electric suppl# is

produced.

The basic requirements are,-

uel /coal

*oiler

1team turbine

Generator

2sh handlin s#stem

3nit au4iliaries

INTRODUCTION


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Due to hih rate of increasin population da# b# da#$ widenin ap between power

demand and its availabilit# was one the basic reason for envisain the G.N.D.T.P. for the

state of Pun5ab. The other factors favorin the installation of the thermal power station

were low initial cost and comparativel# less estation period as compared to h#dro

electric eneratin stations. The foundation stone of G.N.D.T.P. at bathinda was laid on

'

th

November '6$ the auspicious occasion of (00

th

birth anniversar# of reat Guru

Nanak Dev 7i.

The historic town of bathinda was selected for this first and prestiious thermal

pro5ect of the state due to its ood railwa# connections for fast transportations of coal$

availabilit# of canal water and pro4imit# to load center.

The total installed capacit# of the power station &&08" with four units of

''08" each. The first unit of the plant was commissioned in 1eptember$ '9&.

1ubsequentl# second$ third and fourth units started eneration in 1eptember '9($ 8arch

'9:$ and 7anuar# '9 respectivel#. The power available from this plant ives spin to

the wheels of industr# and aricultural pumpin sets.

BRIEF HISTORY OF

PLANT


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;>, ; < >, - @rder for e4ecutin ;


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The selection of site for Thermal Power Plant is more difficult compared to E#dro

Power Plant$ as it involves number of factors to be considered for its economic

5ustification. The followin consideration should be e4amined in detail before selection

of the site for the Plant. The location for plant should be made with full consideration not

onl# of the trends in the development and location but also the availabilit# and location of

the cheapest source of primar# ener#,-

2vailabilit# of fuel

2sh disposal facilities

1pace requirement

Nature of land

2vailabilit# of labour

Transport facilities

Public societ# problems

Development of *ackward 2rea

LANDMARK ACHIEVED


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G.N.D.T.P. won an award of ;s. =.'6 crores from Govt. of >ndia for better

performance in ':=-:&.

>t achieved a rare distinction of scorin hart ;ick b# winnin meritorious

productivit# awards of Govt. of >ndia$ 8inistr# of Fner# for #ear ':9$ ':: and

': due to its better performance.

>t aain won meritorious productivit# awards durin the #ear ')-'= and

'=-& and has become entitled for the #ear '6-'9 for better performance.

>t also won awards for reduction in fuel oil consumption under Govt. of >ndia

incentive scheme #ears from ')-'= /awards mone# for ')$ '= and '&

alread# released for '($ '6 and '9 under the consideration of Govt. of

>ndia.

G.N.D.T.P. had achieved a eneration of )9)&)&0 A3Cs /at a PAf of 90B and

reisterin an oil consumption as low as '.96ml!kwh durin the #ear '=-& has

broken all previous records of performance since the inception of plant.

CONTRIBUTION OF

THE PLANT


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Guru Nanak Dev Thermal Plant$ *athinda$ in addition to indirect contribution in various

facts of state econom#$ is also responsible for,-

♣ Narrowin the ap between power demand and power availabilit# of the state.

♣ Providin emplo#ment potentials to thousands of workers.

♣ ?overin the backward surroundin area into full# developed >ndustrial

Township.

♣ Providin additional relief to aricultural pumpin sets to meet the irriation

needs for enhancin the ariculture production.

♣ ;eliabilit# and improvement in continuit# of suppl# and s#stem voltae.

♣ 2chievin cent percent rural electrification of the state.

PLANT SALIENT FEATURES

THE PLANT


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PROJECT AREA:-

Power plant )=: acres

2sh disposal :&(

Aake ':0

;esidential colon# ):(

8arshallin #ard )(6

Total area ':0&

T@T2A ?@1T, - ;s. ''( crores

1T2T>@N ?2P2?>T, - four units of ''08".each

BOILER:-

8anufacturers *.E.F.A.

8a4imum continuous ratin /8.?.;. =9( T!hr.

1uperheater outlet pressure '= k!cmH

;eheater outlet pressure ==.: k!cmH

inal superheater!reheater temperature (&0°?

eed water temperature )&0°?

Ffficienc# :6B

?oal consumption per da# per unit '&00 tones /2ppro4imate

STEAM TURBINE:-


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;ated output ''0 8".

;ated speed =000 r.p.m.

Number of c#linders three

;ated pressure '=0 k!cmH

;ated temperature (=(°?

?ondenser vacuum 0. k!cmH

GENERATOR:-


;ated output

/3nit- ' < ) ')(000I2

/3nit -= < & '=9000I2

Generator voltae ''000 volts

;ated phase current

/unit J' < ) 6(60 2mps. /unit J= < & 9))0 2mps.

Generator coolin h#droen

BOILER FEED PUMPS:-

Number per unit two of '00B dut# each

T#pe centrifual

;ated dischare &&( T!hr.

Dischare head '60 8"?.

1peed &(00 r.p.m.


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CIRCULATING WATER PUMPS:-

Numbers for two units five of (0B dut# each

T#pe mi4ed flow

;ated dischare :600 T!hr.

Dischare head )& 8"?.

COOLING TOWERS:-

Numbers four

"ater cooled ':000 T!hr.

?oolin rane '0°?

Eeiht ')0!') metres

COAL PULVERISING MILLS:-

Numbers three per unit

T#pe drum-ball

;ated output )9 T!hr.

?oal bunkers '6 per unit

RATING OF 6.6 KV AUXILLIARY MOTORS:-

?oal mill 6=0 I"

apour fan =)0 I"

?.". an :00!9&6 I"

?oal crusher ()0 I"


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Primar# air fan =)0 I"

orced drauht fan =)0 I"

*oiler feed pump =(00 I"

>nduced drauht fan 00!'000 I"

?ondensate pump '9( I"


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?oal received from collieries in the rail waon is mechanicall# unloaded b#

"aon Tippler and carried b# belt ?onve#or 1#stem *oiler ;aw ?oal *unkers after

crushin in the coal crusher. The crushed coal when not required for ;aw ?oal *unker is

carried to the coal storae area throuh belt conve#or. The raw coal feeder reulates the

quantit# of coal from coal bunker to the coal mill$ where the coal is pulveri%ed to a fine

powder. The pulveri%ed coal is then sucked b# the vapour fan and finall# stored in

pulveri%ed coal bunkers. The pulveri%ed coal is then pushed to boiler furnace with the

help of hot air steam supplied b# primar# air fan. The coal bein in pulveri%ed state ets

burnt immediatel# in the boiler furnace$ which is comprised of water tube wall all aroundthrouh which water circulates. The water ets converted into steam b# heat released b#

the combustion of fuel in the furnace. The air required for the combustion if coal is

supplied b# forced drauht fan. This air is however heated b# the outoin flue ases in

the air heaters before enterin the furnace.

The products of combustion in the furnace are the flue ases and the ash. 2bout

)0B of the ash falls in the bottom ash hopper of the boiler and is periodicall# removed

mechanicall#. The remainin ash carried b# the flue ases$ is separated in the electrostatic

precipitators and further disposed off in the ash dampin area. The cleaner flue ases are

let off to atmosphere throuh the chimne# b# induced drauht fan.

The chemicall# treated water runnin throuh the water walls of boiler furnace

ets evaporated at hih temperature into steam b# absorption of furnace heat. The steam

is further heated in the super heater. The dr# steam at hih temperature is then led to the

turbine comprisin of three c#linders. The thermal ener# of this steam is utili%ed in

turbine for rotatin its shaft at hih speed. The steam dischared from hih pressure

/E.P. turbine is returned to boiler reheater for heatin it once aain before passin it into

the medium pressure /8.P. turbine. The steam is then let to the coupled to turbine shaft

is the rotor of the enerator$ which produces electricit#. The power from the enerator is

pumped into power rid s#stem throuh the enerator transformer b# steppin up the

voltae.

WORKING OF

THERMAL PLANT


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The steam after doin the useful work in turbine is condensed to water in the

condenser for rec#clin in the boiler. The water is pumped to deaerator from the

condenser b# the condensate e4traction pumps after bein heated in the low pressure

heater /A.P.E from the deaerator$ a hot water storae tank. The boiler feed pump

dischare feed water to boiler at the economi%er b# the hot flue ases leavin the boiler$

before enterin the boiler drum to which the water walls and super heater of boiler are

connected.

The condenser is havin a lare number of brass tubes throuh which the cold

water is circulated continuousl# for condensin the steam passin out sides the surface of

the brass tubes$ which has dischared down b# circulatin it throuh the coolin tower

shell. The natural drauht of cold air is created in the coolin tower$ cools the water fall

in the sump and is then recirculated b# circulatin water pumps to the condenser.


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BOILER FEED PUMP:-

2s the heart is to human bod#$ so is the boiler feed pump to the steam power plant. >t is

used for rec#clin feed water into the boiler at a hih pressure for reconversion into

steam. Two nos. '00B dut#$ barrel desin$ hori%ontal$ centrifual multistae feed pumps

with h#draulic couplin are provided for each unit. This is the larest au4iliar# of the

power plant driven b# =(00 I" electric motor.

The capacit# of each boiler at GURU NANAK DEV THERMAL PLANT is

=9( tones!hr. The pump which supplies feed water to the boiler is named as boiler feed

pump. This is the larest au4iliar# in the unit with '00B capacit# which takes suction of feed water from feed water tank and supplies to the boiler drum after preheatin the same

in EP-'$ EP-) and economi%er. The deliver# capacit# of each boiler feed pump is &&(

tones!hr. to meet better requirements correspondin to the various loads$ to control steam

temperature$ boiler make up water etc. The detailed particulars checkin of protections

and inter locks$ startin permission etc. are as below,-

Part!"#ar$ %& BFP a'( t$ )a' )%t%r:-

BOILER FEED PUMP: - The ''0 8" turboset is provided with two boiler feed pumps$ each of '00B of total quantit#. >t is of barrel desin and is of hori%ontal

arranement$ driven b# an electric motor throuh a h#draulic couplin.

T#pe )00 IE>

No. of staes 6

Deliver# capacit# &&( t!hr.

eed water temperature '(:°?

1peed &(00 rpm

Pressure at suction :.=0 k!cmH

1tuffin bo4 mechanical seal

Aubrication of pump b# oil under pressure

2nd motor bearin supplied b# h#draulic couplin

?onsumption of coolin water )=0 A!min.

GENERAL DESCRIPTION


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WATER TREATMENT PLANT:-

The water before it can be used in the boiler has to be chemicall# treated$ since untreated

water results in scale formation in the boiler tubes especiall# at hih pressure and

temperatures. The water is demineralised b# >on F4chane Process. The water treatment

plant has production capacit# of ':00 Tonnes per da# for meetin the make-up water

requirement of the power station.

COAL MILL:-

?oal 8ill pulveri%es the raw coal into a fine powder before it is burnt in the boiler

furnace. The pulveri%in of coal is achieved with the impact of fallin steel balls$

weihin ().( tonnes$ contained in the mill drum rotatin at a slow speed of '9.( r.p.m.

The raw coal is dried$ before pulveri%in$ with inert hot flue ases tapped from the boiler.

Three coal mills each with a pulveri%in capacit# of )9 T!hr. are provided for one unit.

INDUCED DRAUG*T FAN:-

Two nos. a4ial flow >nduced Drauht ans are provided for each unit to e4haust ash laden

flue ases from boiler furnace throuh dust e4traction equipment and to chimne#. The fan

is driven b# an electric motor throuh a fle4ible couplin and is equipped with remote

controlled reulatin vanes to balance drauht conditions in the furnace. The fan is

desined to handle hot flue ases with a small percentae of abrasive particles in

suspension.

CONTROL ROOM:-

The control room is the operational nerve center of the power plant. The performance of

all the equipments of the plant is constantl# monitored here with the help of sophisticated

instrumentation and controllers. 2n# adverse deviation in the parameters of various

s#stems is immediatel# indicated b# visual and audio warnin and suitable correctiveaction is taken$ accordinl#. The control room is air conditioned to maintain the desired

temperature for proper functionin of the instruments.


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SWITC* YARD:-

Flectricit# enerated at '' I b# the turbo-set is stepped-up b# unit transformers to

'=)!))0 I for further transmission throuh hih tension lines to 8aur$ 8uktsar$

8alout$ N..A.$ 1anrur and Audhiana. Transmission of power to rid is controlled

throuh 9 nos. ))0 I and '( nos. '=) I. 2ir *last ?ircuit *reakers alon with their

associated protective s#stems.

WAGON TIPPLER:-

The coal received from the collieries$ in more than '00 rail waons a da#$ is unloaded

mechanicall# b# two nos. waon tipplers out of which one serves as a standb#. Fach

loaded waon is emptied b# tipplin it in the underround coal hopper from where the

coal is carried b# conve#or to the crusher house. 2rranements have been provided for

weihin each rail waon before and after tipplin. Fach tippler is capable of unloadin

6-: rail waons of (( tonnes capacit# in an hour.

CRUS*ER *OUSE:-

?oal unloaded b# the waon tippler is carried to crusher house throuh conve#ors for

crushin. Two nos. hammer t#pe coal crushers are provided$ which can crush coal to a

si%e of '0 mm. The crushed coal is then supplied to *oiler ;aw ?oal *unkers. The

surplus coal is carried to coal storae area b# series of conve#ors. ?rushin of coal is an

essential requirement for its optimum pulveri%in and safe storae.

COOLING TOWERS:-

?oolin Towers of the power plant are the land mark of the *athinda ?it# even for a far

distance of :-'0 kilometers. @ne coolin tower is provided for each unit for coolin

':000 tones of water per hour b# '0°?. coolin towers are massive erro-concrete

structure havin h#perbolic profile creatin natural drauht of air responsible for

achievin the coolin effect. ?oolin tower is as hih as &0 store# buildin.


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BOILER:-

>t is a sinle drum$ balanced drauht$ natural circulation$ reheat t#pe$ vertical combustion

chamber consists of seamless steel tubes on all its sides throuh which water circulates

and is converted into steam with the combustion of fuel. The temperature inside the

furnace where the fuel is burnt is of the order of '(00 °?. The entire boiler structure is of

&)meter heiht.

BOILER C*IMNEY:-

The flue from the boiler$ after removal of ash in the precipitators$ are let off to

atmosphere throuh boiler chimne#$ a tall ferro-concrete structure standin as hih as the

historic Kutab 8inar. our chimne#s$ one for each unit$ are installed. The chimne# is

lined with fire bricks for protection of ferro-concrete aainst hot flue ases. 2 protective

coatin of acid resistant paint is applied outside on its top '0 meters.

CIRCULATING WATER PUMP:-

Two nos. of circulatin water pumps provided for each unit$ circulate water at the rate of

'9)00 T!hr. in a closed c#cle comprisin of Turbine ?ondenser and ?oolin Tower. 2n

additional ?irculatin "ater Pump provided serves b# for two units. The water

requirement for bearin coolin of all the plant au4iliaries is also catered b# these pumps.


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1ince G.N.D.T.P. units are primaril# coal fired units so each boiler is

provided with closed millin circuits to pulveri%e the raw coal which is

received from coal conve#in s#stem after coal crushes before it is fired in

the furnace. The necessit# of pulveri%in the coal is to be ensurin its

ma4imum possible combustion in the furnace. The coal data for units are, -

COAL DATA UNITS 1 & 2 UNITS 3 & 4

T#pe of ?oal

Net ?alorific alue

8oisture

2sh ?ontent

olatile 8atter

>ncombustible

>nlet of ?oal

*ituminous

&=00 Ical!k

'0 B

=0 B

)& B

'0 mm

*ituminous

&9)9 Ical!I

9.( B

=) B

)9 B

)0 mm

;aw coal of ma4imum si%e '0 mm J )0 mm is pulveri%ed in the millin

circuit and the output from the mill is fine coal. 8illin circuits of the

followin main constituents, -

COAL MILLING PLANT


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'. ;aw ?oal *unkers /;.?. *unkers.

). ;aw ?oal ?hain eeders.

=. Drum 8ill or ?oal 8ill.

&. ?lassifiers.

(. ?#clone 1eparator.

6. apour an.

9. Pulveri%ed ?oal *unkers /P.?. *unkers.

COAL MILL


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RAW COAL BUNKER:-

Fach of three raw coal bunkers is fabricated from the sheet metal and is well stiffened all

around. The storae capacit# of each raw coal bunker is about (00 tones. There are four

outlet ates with each bunker. The ates are electricall# operated from site. >n case of failure of the electric motors the ate can be hand operated from site. 2t a time onl# one

ate openin is suffices but should be chaned so that there is no pillin within the

bunker.

RAW COAL C*AIN FEEDER:-

The raw coal chain feeder transports coal from raw coal bunker to the inlet chute leadin

to the pulveri%ed!coal mills. There is a double link chain of hih tensile strenth steel$

which moves on wheels and sweeps the raw coal fallin over the top of the raw coal

chute of the mill. The heiht of the coal bed in the chain feeder can be ad5usted manuall#

b# means of lever operated damper. The ma4imum and minimum heihts of the coal bed

are )00mm and ')0mm respectivel#. The sinalin equipment indicates the absence of

coal flow in the feeder$ which is annunciated in the unit control board /3.?.*.. The main

shaft on the drivin end is connected to the drivin unit$ consistin of variator$ a ear bo4

and a motor all mounted as a sinle unit. The chain wheel on the drivin end shaft is

provided with a shear pin$ which will shear off and disconnect the drivin mechanism if

there is an# overload on the feeder. The speed of the chain feeder is reulated

automaticall#!remotel# b# actuatin the control spindle of the variator throuh a

servomotor. 2 pump for circulatin the oil in the ear bo4 of variator is an interal part of

variator driven b# a separator motor. 1ome of the technical data about the raw coal chain

feeder is iven here,-

'. @utput of the chain feeder '0-&( tonnes!hr.

). 1peed variations 0.0(0=-0.'('m!sec.=. 8ain motor 9.(k"$ &'($ (0E%.

&. @il pump motor 0.0(k"$ ))0

(. @peratin motor of each ate =EP$ &'( and (0E%.


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DRUM MILL:-

Fach mill consists of sinle compartment drum$ bearins drivin motor$ coal inlet

and dischare pipin$ ball chane and lubricatin equipment for mill bearins. 8ill drum

is fabricated from thick steel plates and is supported on to the anti-friction bearins. Themill is driven b# an electric motor of capacit# 6=0k"$ 0 rpm$ 6.6k throuh a

reduction ear$ which reduces the speed to '9.( rpm. The ball chare for the mill consists

of the three different si%es of fored steel balls detailed as below. The capacit# of each

mill is )9 T!hr. in case of unit ' < ) and ): T!hr.

'. &0mm diameter ))(00 k

). (0mm diameter )0000k

=. 60mm diameter '0000k

4. To!" B!"" C#!$% '2'(()%

Durin operation onl# 60mm diameter balls are added is appro4. (00 k per week

and the uidin factor is the amperae of the coal mill$ normall# it should be 66-ampere

appro4. at full load and when it falls below the above value ball charin of the mill is

carried out. Aubricatin s#stem consists of the oil tank$ ear pump$ oil cooler and base

frame to mount all these equipments. Gear pump is driven b# an electric motor of ratin '

E.P.$ &'( $ '&&0 rpm. 1uction side of the ear pump is connected to the tube oil tank and

the deliver# side is connected to inlet of the oil cooler and after coolin oil oes to the

bearins. The oil from the bearins is cooled to the required temperature in the cooler b#

the means of plant bearin cooler water.

CLASSIFIER:-

The classifier is fabricated from the steel plates. >t is an equipment that separates fine

pulveri%ed coal from the coarser pieces. The pulveri%ed coal alon with the carr#in as

well as dr#in medium /flue as strikes the impact plate in the classifier and the coarser

pieces et separated due to the chane in the direction of flow and o back to mill. The

stream then passes to the outlet branch of the classifier throuh an ad5ustable telescopic

tube. 2t the outlet ad5ustable vanes are provided to chane the si%e of coal when required.


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CYCLONE SEPARATOR:-

The centrifual t#pe c#clone separator consists of two c#clones made up of welded

sheets. >t is equipment in the millin plant$ which serves for separatin the pulveri%ed

coal from the vapours i.e. carr#in medium. The pulveri%ed coal ets stored in the pulveri%ed coal bunkers and vapours o to suction of vapour fan. 2t the bottom of the

c#clone separator a rotar# valve /Turnikete is provided to transport coal from c#clone

separator to P.?. bunker on the worm conve#or as the case ma# be.

VAPOUR FAN:-

Pulveri%ed coal bunker is welded from thick steel sheets and has a capacit# of & hours

coal consumption at ma4imum continuous ratin of the boiler. The whole bunker is

insulated e4ternall#. The carbon-dio4ide blanketin s#stem has been provided in the P.?.

bunker to prevent fire ha%ards inside the bunker. The while storae bunker is divide into

four parts namel# 2$ * ? < D. urther four coal feeders are taken out from each bunker

leadin to each corner of the furnace.

CRUS*ING OF COAL:-

"hen coal reaches the plant$ normal si%e of coal is about (00mm. 2fter unloadin the

coal from the rake is fed to primar# crusher$ which reduces the si%e to ')0mm. Then coal

is fed to secondar# crusher which reduces the si%e to )(mm and this coal oes to bunker

with the help of conve#or belt from where coal finall# oes to coal mill where coal is

transferred in form of pulveri%ed coal. The coal is heated with the help of hot primar# air.

"e maintain the temperature of about 90°? in coal mill. This temperature is maintained

with the help of cold air and a hot air damper.

USE OF OIL:-

*efore the coal reaches the furnace$ we preheat the furnace in order to remove the

moisture and raise the temperature of furnace$ so that coal can catch fire easil# without

an# dela#. This preheatin of furnace is done with the help of oil. "ith burnin of oil$ we


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maintain the temperature of furnace at =(0°?. we cut the oil suppl# after =(0°? because

oil is ver# costl#. 1ource of oil for G.N.D.T.P.$ *athinda is 8athura @il ;efiner#. @ther

use of oil is in bearin s#stem for coolin. There are lare number of bearins for plant.

or e4ample bearin s#stem of turbine. These bearins et heated upto hih temperature$

which is danerous. 1o we cool the bearin b# circulatin water in bearin.

COAL FEEDING AND COAL MILL:-

rom the coal handlin plant$ coal comes in two belts namel# (2 and (* and then b#

belts 62 and 6* coal comes in bunkers. *unker capacit# is =00 tonnes. Number of outlets

of bunker is three. irst ate is opened for one hour and second and then third. >f open the

one ate for lon time$ then coal will stop oin to mill. That is wh# we open the ate

turn b# turn.

RAW COAL C*AIN FEEDER:-

;aw coal chain feeder is 5ust below raw coal bunker. >t is a slidin chain which feed the

coal to mill. "e can chane the quantit# of coal which is fed to mill in two wa#s.

*# chanin the speed of chain

*# chanin the depth of coal in chain

1peed of chain can be chaned b# addin a ear s#stem to motor. "e connect the

ear s#stem with motor with a pin called shear pin. The prevent the overloadin of motor

because when the coal quantit# of coal on chain is reater than its capacit# then the pin

will break and prevent the pin from overloadin. 1peed of ;aw ?oal chain is )L to 6L!sec.

COAL MILL:-These are mainl# of two t#pes,-

i *all 8ills

ii *owl 8ills


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Ba## M##$: - >n *all 8ills there are steel balls which are revolvin in hori%ontal

c#lindrical drum. These balls are free from an# shaft and balls are touchin with each

other and with internal bod# of drum. These t#pes of mills are at *athinda Thermal Plant.

@n the other hand$ bowl mills part of the mill contain drive s#stem i.e. it contains 6.6 k

electric motor and ear s#stem which translates the revolution about hori%ontal a4is to

revolve about vertical a4is. The revolvin vertical a4is contains a bowl about the drivin

s#stem. This bowl is fi4ed with drivin and revolvin with shaft. There are also three

rollers which are suspended at some inclination$ so that there is a ap of few mm between

roller surface. These rollers are free to rotate about the a4is.

Bo*" M+""- The coal is rinded and then fed into the mill at the center or near of

revolvin bowl. >t passes between the rindin rin in revolvin bowl and rolls as

centrifual force causes the material to travel towards the out perimeter of bowl. The

sprins$ which load the rolls$ impart the necessar# force for rindin. The partiall#

pulveri%ed coal continue oin up and down and over the ede of bowl.


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The G.N.D.T.P. units are primaril# coal-fired units and the coal consumption at

ma4imum continuous ratin /8.?.;. per unit is about (: T!Er. the coal used at

G.N.D.T.P. is of bituminous and sub-bituminous t#pe and this is received from some

collieries of 8.P. and *ihar. The desined composition of coal is as below,-

T#pe *ituminous ?oal

Net calorific value &=00 kcal!k

8oisture content in coal '0B

2sh content =0B olatile matter in combustibles )&B

Grind abilit# inde4 (0 Eard Groove

The coal handlin plant at G.N.D.T.P. has been supplied and erected b# 8!s Flecon

Fnineerin ?ompan# Aimited$ allabh id#a Naar$ Guarat. ?oal is transported from

the coal mines to the plant site b# ;ailwa#s. Generall#$ the raw coal comes b# railwa#

waons of either eiht wheels weihin about 9( to :0 tones each or four wheels

weihin about =( to &0 tones each. The loaded waon rake is brouht b# railwa#s main

line loco and left on one of the loaded waon tracks in the power station marshallin

#ard. The main line loco escapes throuh the enine track. The station marshallin #ard is

provided with : tracks. The arranement of the tracks in the marshallin #ard is as

follows,-

DESTINATION NO. OF TRACKS

Aoaded waons receivin tracks our

Fmpt# waon standin tracks Three

Fnine escape tracks @ne

COAL HANDLING PLANT

/CHP0


26/125

UNLOADING OF COAL:-

>n order to unload coal from the waons$ two ;oadside Tipplers of Flecon make

are provided. Fach is capable of unloadin ') open t#pe of waons per hour. Normall#

one tippler will be in operation while the other will be standb#. The loaded waons are brouht to the tippler side b# the loco shunters. Then with the help of inhaul beetle one

waon is brouht on the tippler table. The waon is then tilted upside down and emptied

in the hopper down below. The emptied waon comes back to the tippler table and the

outhaul beetle handles the empt# waons on the dischare side of the tippler. The tippler

is equipped with the interal weihbride machine. This machine consists of a set of

weihin levers centrall# disposed relative to tippler. The rail platform rests on the

weihin irders and free from rest of the tippler when the waon is bein weihed. 2fter

weihin the loaded waons is tipped and returned empt# to the weihin irders and

aain weihed. Thus the difference of the ross weiht and the tare weiht ives the

weiht of the waon contents. The tipplers are run b# motors of :0 E.P. each throuh

ears onl#.

WAGON TIPPLER

The tippler is desined to work on the followin c#cle of operation,-

Tippin 0 seconds

Pause (-') seconds

;eturn 0 second1


27/125

"eihin =0 seconds

Total )'(-))) seconds

2llowin :( seconds for waon chanin it will be seen that ') eiht-wheel waons or

)& four-wheel waons per hours can be tipped. Eowever since the coal carr#in capacit#

is (00 tones per hour load of ') waons comes to : to per hour.

DUST TRAPPING SYSTEM:-

The tippler is also provided with the dust trappin s#stems b# which the dust nuisance

will be minimi%ed. 2s the tippler rotates$ a normall# closed hopper valve opens

automaticall# and the dischared material passes throuh it into the hopper with its dust-

settin chamber$ there is an air valve of lare area$ which opens$ simultaneousl# with the

hopper valve. The ob5ect of this air valve is to blow back throuh the hopper valve into

the tippin chamber$ which must occur if$ the settlin chamber were closed$ it bein

remembered that a lare waon contains some )&0 cubic feet of material and that this

volume of dust air would be forced back at each tip if the hopper chamber were a Mclosed

bottleL. The air valve and the hopper valve are shut immediatel# on reversal of the tippler

and are kept shut at all times e4cept durin the actual dischare. The hopper valve is

operated b# a motor of '0 E.P.$ &'( olts and the air valve is operated b# electro-

h#draulic thruster. >nlet valve consists of lare number of plates slidin under the waon

tippler ratin. ?oal in the waon tippler hopper forms the heap and as such obstructs the

movement of slidin valve and damain the plates. The inlet and outlet valves have

therefore been b#passed.

The unloaded material falls into the waon tippler hopper /common to both

tipplers havin a capacit# of )'0 tones. The hopper has been provided with a ratin of

=00mm =00mm si%e at the top so as to lare si%e boulders ettin into the coal stream.

There is also a provision of unloadin the waons manuall# into the 82N32AA

3NA@2DFD E@PPF; of ''0 tones capacit#. 8anuall# unloadin will be restored to

while unloadin coal from sick waons or closed waons.


28/125

MAGNETIC PULLEYS:-

@n belt conve#or no. &2 and &*$ there have been provided hih intensit#

electromanetic pulle#s for separatin out tramp iron particles!pieces from the main

stream of coal conve#in. D.?. suppl# for the manet is taken on &'( volt$ = phase$ (0c#cles 2.?. suppl# s#stem.

>n addition to above hih intensit# suspension t#pe electromanets have also been

provided on belt conve#ors &2 and &* for separatin out tramp iron pieces!particles.

RECLAIMING:-

>f the receipt of coal on an# da# more than the requirement of the boilers$ the

balanced material will be stocked via conve#or 92and 9* and throuh telescopic chute

fitted at the end of the conve#or. 2t the end of the chute one tele level switch is provided$

which automaticall# lifts the telescopic chute to a predetermined heiht ever# time. The

tele level switch is actuated b# the coal pile. "hen the telescopic chute reaches ma4imum

heiht durin operation$ which will be cut off b# limit$ switch and stop the conve#in

s#stem. "hen the pile under the telescopic chute is cleared$ the telescopic chute can be

independentl# lower manuall# b# push buttons.

There are five bulldo%ers to spread and compact the coal pile. *ulldo%ers of *harat Farth

8overs Aimited 8ake are fitted with )(0 E.P. diesel enines. Fach bulldo%er is able to

spread the crushed coal at the rate of )(0 tones!hr. over a load distance of 60m the coal

can be stacked to a heiht of 6m the stockpile stores coal for about &( da#s for four units

with an annual load factor of 0.66.

"henever coal is to be reclaimed the bulldo%ers are emplo#ed to push the coal in

the reclaim hopper havin a capacit# of ''0 tones. The coal from the reclaim hopper is

fed either 2 or * belt conve#or throuh vibrator# feeders :2 and :*.

CRUSHER HOUSE-

The crusher house accommodates the dischare ends of the conve#or &2$ &* receivin

ends of conve#or (2$ (* and conve#or 92 and 9*$ two crushers$ vibratin feeders and


29/125

necessar# chute work. There are two crushers each driven b# 900E.P. electric motor$ =

phase$ (0 c#cles and 6.6 k suppl#. The ma4imum si%e of the crushed coal is '0mm. The

capacit# of each crusher is (00 tones!hr. one crusher works at a time and the other is

standb#. rom the crusher the coal can be fed either to the conve#ors (2$ (* or 92$ 9*

b# ad5ustin the flap provided for this purpose. There is built in arranement of b#passin

the crusher b# which the coal can be fed directl# to the conve#ors b#passin crusher.

CONVEYOR BELT AND CRUSHER HOUSE


30/125

SWITCH GEAR

INTRODUCTION


31/125

The apparatus includin its associated au4iliaries emplo#ed for switchin$ controllin and

protectin the electrical circuits and equipments is known as switchear.

2 tumbler switch$ which is an ordinar# fuse$ is the simplest form of switchear and is

enerall# used to control and protect the domestic and commercial appliances andequipments. or hih ratin circuits$ a hih rupturin capacit# /E.;.?. fuse in

conduction with switch ma# serve the purpose. Eowever$ such switchear cannot be

applied on power s#stem operatin at hih voltaes$ i.e. more than '' I because of the

followin reasons, -

'. "hen fuse blows$ it takes sometime to replace it and consequentl# there is

interruption of power suppl#.

). @n hih voltae s#stem$ a fuse cannot successfull# interrupt lare fault currents.

=. "hen fault occurs$ fault takes sometime to blow. Durin this time the costl#

equipments e.. enerators$ transformers etc. ma# be damaed.

Therefore in order to protect lines$ enerators$ transformers and other electrical

equipments from damae$ an automatic protective device or switchear are required.

2utomatic protective switchear mainl# consists of the rela#s and circuit breakers. 2

circuit breaker is switchear$ which can be open or close the circuit after an operation.

Therefore$ a circuit breaker is rather preferred even in the instance when a fuse is

adequate.

S+t!, : -

>t makes and breaks the circuit under full load or no load condition but cannot be

operated under fault conditions. >t is enerall# operated manuall#.

I$%#at%r: -

>t is onl# operated under no load conditions. >ts main purpose is to isolate a portion of

the circuit from the other. >solators are enerall# place on the both sides of a circuit

breaker from the other in order to make repairs and maintenance on the circuit breaker

without an# daner. There are two t#pes of isolators, -

TYPES OF ISOLATER:-


32/125

• 1inle pole >solator

• Double pole >solator

FUSES:-

2 fuse is short piece of metal$ insert in series with the circuit$ which melt e4cessive

current flows throuh it and thus breaks the circuit. The material used for the fuse

element should possess the followin properties, -

• Aow meltin point.

• Eih conductivit#.

• ree from o4idation.

The common materials used for the fuse element are copper$ tin-lead allo# /tin 6=B and

lead =9B$ silver$ aluminum etc. 2 fuse is connected in series with the circuit to be

protected and carries the load current without overheatin under normal conditions.

Eowever when abnormal condition occurs$ an e4cessive current flows throuh it. This

raises the temperature$ which melt the fuse element and open the circuit. This protects the

machine or apparatus from the damae$ which can be used b# e4cessive currents.

CIRCUIT BREAKERS

?ircuit breaker is on!off switch operatin in an electric circuit in normal as well as

abnormal operatin conditions. "hile makin or breakin contact there is a transition

stae of arcin between contacts which is overned b# electric dischare between the

contacts at instant of separation$ thus current continuous in the circuit till dischare

appears.

The stud# of this phenomenon is ver# important for desin and operational

characteristics of ?.*.

F"'!t%'$ %& S+t!,ar: -

3nder different conditions ?* is sub5ected to var#in stresses as current varies from few

amp due to no load current of T! up to man# I amp heaviest short circuit current and


33/125

var#in circuit impedance. ?* not onl# interrupts$ but also closes the circuit. >f breaker

closes durin short circuit it causes some trouble because then the voltae break down

that brides the contact ap produces hih current arc which melt the contact before

closer such situations is not desirable as breaker ma# not reopen. @ften automatic re-

closin is required because usuall# fault is of temporar# nature. 2bout )0B of the short

circuit current persists however immediatel# after re-closin the breaker has to re-

interrupt the short circuit current. This is main function speciall# if there are e4tremel#

hih currents$ which would result in the contact wear and tear.

The main function$ which ?* has in addition to satisf# the rated breakin capacit# and

rated makin and breakin times are, -

•1hort ?ircuit interruption.

• >nterruption of small induction currents.

• ?apacitor 1witchin.

• 2s#nchronous 1witchin.

• >nterruption of 1hot Aine aults.

O/rat' Pr'!/# O& Cr!"t Bra0r: -

2 circuit breaker is a device which, -

8akes or *reaks a circuit either manuall# or b# remote contact under normal

/full load conditions.

*reaks a circuit manuall# or b# remote control under abnormal conditions.

*reaks a circuit automaticall# under abnormal conditions i.e. fault conditions.

Thus circuit breaker is 5ust a switch$ which can be operated under normal$ and

abnormal conditions both manuall# and automaticall#.

To perform the above operation a circuit breaker essentiall# consists of fi4ed andmovin contacts$ called electrodes. "hen fault occurs on the power s#stem$ the trip coil

of the circuit breaker is eneri%ed$ which pulls apart the movin contacts from the fi4ed

contacts as shown in fi thus opens the circuit.


34/125

"hen the movin contacts are separated from the fi4ed contacts$ an arc is struck

between them. The production of arc not onl# dela#s the current interruption process but

also enerates enormous heat which ma# cause damae to the equipments of the power

s#stem or the breaker itself. Therefore ever# effort is made to e4tinuish the arc produced

in the circuit breaker as quickl# as possible.

Cr!"t Bra0r Rat'$: -

2 circuit breaker is required to be operated under all conditions. Eowever this ma5or

dut# of the circuit breaker is to operate the circuit under short circuit condition. 3nder

short circuit conditions$ a circuit breaker is required to perform three ma5or duties, -

• >t must be capable of operatin circuit on the occurrence of the fault.

• >t must be capable of closin the circuit on fault.

• >t must be capable of carr#in a fault current safel# for a short time$ while another

circuit breaker /in series is clearin the fault.

2ccordin to the duties to be performed b# a circuit breaker$ there are three t#pes of

ratins, -

Bra0' Ca/a!t1: -The r.m.s. value of current that a circuit breaker is capable of breakin at a recover#

voltae under specified conditions /i.e. recover# voltae and rate of recover# voltae is

known as breakin capacit# of a circuit breaker. *reakin ?apacit# in 82O √= × rated

voltae × rated breakin current × '0-6.

Ma0' Ca/a!t1: -

The peak or ma4imum value of the current /includin d.c. component durin the first

c#cle of the current wave after the circuit is closed b# the breaker /under dead short

circuit is called makin capacit#.8akin ?apacit#O √=× '.: × 1#mmetrical breakin

capacit#.

S,%rt T) Ca/a!t1: -


35/125

The period for which the circuit breaker is able to carr# the fault current while remainin

closed is called short time capacit# of the circuit breaker.

N%r)a# C"rr't Rat': -The r.m.s. value of the current which a circuit breaker is capable of carr#in continuousl#

at its rated frequenc# under specified conditions without overheatin the arc or contacts is

called normal current ratin.

O# Cr!"t Bra0r: -

>n this circuit breaker+ the current carr#in contacts are immersed in transformer oil.

"hen the contacts are separated$ arc is struck between them. The heat of the arc

dissociates the oil and ases viz. E#droen etc are evolved. The h#droen as bubble

surrounds the arc and cool it downs which help in de-ioni%ation of the medium between

the contacts and e4tinuishes the arc. 8oreover$ ases setup turbulence in the oil and

force it into the arc space when the current is %ero which further helps in e4tinuishin

the arc.

A(2a'ta$: -

• >t absorbs the ener# of the arc b# decomposin the oil into ases.

• The ases evolved provide ood coolin effect.

• The surroundin oil enclose the pro4imit# to the arc provides coolin effect.

• >t has abilit# to flow in the arc space after the current is %ero.

>t acts as insulator between the live contacts and earthed tank.

D$

a(2a'ta$:-

• >t is easil# inflammable.


36/125

• >t ma# form an e4plosive mi4ture with air.

• >t requires more maintenance.

M')") O# Cr!"t Bra0r: -

>n bulk oil circuit breaker$ transformer oil is not onl# used e4tinuish the arc but also

serves as insulation between the live and earthed parts. 2 heav# quantit# of oil$

dependin upon s#stem voltae$ is used in the bulk oil circuit breakers /about (000 liters

in ))0I s#stem. This not onl# increases the e4penses but also increases the fire risk.

Therefore minimum oil circuit breakers are desined in which onl# '0 B of the oil is

used to e4tinuish the arc. The container of minimum oil circuit breakers is supported on

porcelain insulators. To provide the required insulation between the live and earthed

parts. Thus the minimum oil circuit breakers also require less space for installation.


37/125

MOCB3$ have followin merits and demerits, -

Mrt$: -a. >t requires lesser quantit# of oil i.e. onl# for arc e4tinction.

b. >t requires smaller space for installation.

c. ;isk of fire is considerabl# reduced.

d. Aesser maintenance.

D-Mrt$: -

a. Due to smaller quantit# of oil the deree of carboni%ation is increased

therefore oil needs replacement after each operation.

b. Proper desin is required to remove the ases from the contacts space

in time


38/125

BRIEF DESCRIPTION OF . KV41'V

SWITC*GEAR

SUPPLIED TO G.N.D.T.P. BAT*INDA

>n 6.6!&'( I switchear we have two unit transformer and one station T!f that after

steppin down the voltae$ fed it to two 6.6 I unit buses and to station bus. arious

feeders are connected to 6.6 I buses and in order to avoid complete shutdown$ suppl#

is maintained b# drawin suppl# from station bus$ to =* < &* bus. 1uppl# from =2 bus

is stepped down to &'( b# '000 I2 1"G; T! J ' < fed to &'( bus. 1ame in &*

bus. >n case of trippin standb# bus used. arious feeders are connected to these buses.

"e enerate electricit# at '' I < step-down to 9 I b# 32T. ;atin of 32T T! is '(

82 < station T!f is ))( 82$ ''!9 I.

CIRCUIT BREAKER USED IN INDOOR SWITC*GEAR: -

8ainl# two t#pes of ?*Cs are used in switchear accordin to the requirement, -

'. 6.6I 8@?*Cs

). &'( 2?*Cs

M')") O# CB 46.6 KV5: -

>t is provided for each motor feeder of ratin 6.6 I and as incomin breaker for 6.6 I

bus. >n these ?*Cs arc is quenched in arcin chamber with minimum quantit# of oil.

SPECIFICATIONS OF MOCB OF MOTOR FEEDER-

;ated oltae 6.6 I$ (0 E%$ =-pole

;ated current ')(0 2mperes

*reakin ?urrent =&.9 I2 /1#m-=9: /2s#m

*reakin ?apacit# =( 82


39/125

8akin ?apacit# :: Peaks I2

1hort Time ?urrent ?apacit# =&.9 I2 for ' 1ec

8@?* uses solid material for insulatin purposes and use 5ust minimum oil for arc

quenchin. The arc-interruption device is enclosed in a tank of insulatin material$ which

is a line voltae in normal operation. Thus are also known as live tank breathers.

arious protections rela# are used in con5unction with 8@?*Cs accordin to requirement

of connected equipment are, -

• @ver current rela#

• >nstantaneous rela#

• Aocked rotor rela#

• 3nbalanced protection rela#

• Farth fault protection rela#

• 3nder voltae rela#

41'V ACB-

>n these ?*Cs air at atmospheric pressure is used for quenchin the arc.

S/!&!at%'$ %& ACB3$: -

;ated oltae 660 /2?

;ated ?urrent '600 2mperes

;ated 8akin ?apacit# ( I2 /PF2I

;ated *reakin ?apacit# &( I2 /rms

8a4. 1witchin requenc#!hour '( make!break open

@penin Time )0msec


40/125

T%ta# O/'' T) I'!#"((

2rcin Time =0.=( msec

?losin Time (00 msec

T,$ CB $ Pr%2(( Wt, T,r Ma' Pr%t!t%' Tr/$: -

'. T,r)a# D#a1( O2r C"rr't Tr/:

This consists of three bimetal strips$ each headed b# a current T!$ which is slid on to the

appropriate phase conductor. Tunin the calibrated knob var# the settin. 2 temp$

compensatin strip is also used which makes the trippin time larel# independent of

ambient temperature.

2. I'$ta'ta'%"$ O2r C"rr't Tr/: -

This is fitted in contact assemblies. The 3 shaped manet cores with associated armature

are mounted on the conductor and eneri%ed b# breaker current.

3. U'(r V%#ta Tr/: -

>t opens the breaker instantl# if the au4iliar# as main voltae drop to (0B of the rated

coil voltae.

VARIOUS REUIREMENTS OF CB USED IN S7G

a 2ll the ?* should be three-pole and there should be suitable for remote!localelectrical operation and manual operation also.

b The ?* should be suitable for the operation on ))0 dc au4iliar# control suppl#.

c The ?* is required to drive motors and also be suitable for incomin from AT T!.


41/125

d The closin @f ?* should be direct motor drive t#pe as stored ener# t#pe.

e The ?* should be provided with manual closin and trippin device also.

f The ?* should also provide with shunt trippin coil suitable for ))0 .

?* should have mechanical indication for @N!@ position.

h ?* should be provided with the device$ which does not allow closed breaker

reached in as reached out

i The ?*Cs should be suitable for lockin$ test < service position < it should also

be suitable for electrical!mechanical operation in both testin service position.

B"$ Bar$ 46.6 KV789 V5: -

This term is used for main bar on conductor carr#in electric current throuh which man#

connections are made for connectin switches and the equipments like bus bar made of

2luminum because it has hiher conductivit#$ corrosion resistant and lower cost ascompared to copper

S+t!, Gar 6.6 KV ?ircuit *reakers 8inimum @il T#pe

;upturin ?apacit# =(0 82

?urrent ;atin ')(0 2mperes

S+t!, Gar 89 V

?ircuit *reakers 2ir T#pe

;upturin ?apacit# ==) 2

?urrent ;atin 0.:2mpere


42/125

D.C. SUPPLY SYSTEM

D.? 1uppl# is the brain of the plant. Fach unit has its own ))0volts D.? s#stem located

in the electrical ba#. &: batter# of requisite ratin are also bein provided. Fach D.?

s#stem comprises of the followin,-

'. 1torae batter#

) *atter# ?hares

=. Distribution < sub-distribution boards

The batteries are of lead acid t#pe. *atter# cells have hih dischare performance cellt#pes each of )volts. *atter# chare are static t#pe < capable of trickle charin < boost

charin. 2dequate standb# provision is also made for the outae of the charer in the

form of installation of standb# chares.

The D.? distribution < sub-station boards are compartmentali%ed+ draw out t#pe$

construction$ housin switches < fuses for various feeders are as per the requirements for

the plant.

The batter# rooms are well ventilated < well lihted < there is adequate provision for

e4pellin acid fumes < fumes h) as out from the batter# room.

'. Dr# cell batteries

). Aead acid batteries

=. 2lkaline cell batteries.

Aead acid cells are of further two t#pes,-

' 2utomobile batter#

) 1tationar# lead acid batter#.

@ut of theses three t#pes of the cells lead acid cell < alkaline cells are rechareable

whereas dr# cells cannot be rechared. >n case of lead acid ell both the electrodes are of

the same material i.e. Aead in case of 2lkaline cell electrodes are of two t#pes,-


43/125

'. Nickle$Aead

). >ron$Nickle.

Flectrodes$ which is mostl# used is potassium h#dro4ide. 2s the batter# dischares$

concentration of lead sulphate oes on increasin$ at a specific ravit# for '.)=

discharin stops < the batter# will not provide an# amount of D.? ener#. The batteries

which are used at G.N.D.T.P. >s havin the ratin of 600 2h. >f these havin '0 ratin$ the

batter# supplies 602mp. @f current ratin '0 hours.

*atteries used in the G.N.D.T.P. for the main purpose of,-

'. Fmerenc# lihtenin

). Protection

Two sets of the batteries are used for each circuit. 1o that if one fails second comes in

action.

BATTERY C*ARGING SYSTEM AT G.N.D.T.P.


44/125

The various requirements for charin the batteries are listed bellow

'. Power requirement

). 2cid=. connections of cells

&. connections polarit#

POWER REUIREMENT

2 D? source capable of deliverin current as specified. The voltae required will be two

times the No. of cells in batter#. The initial charin of the batter# will takes appro4imate

(( to 0 hours.

ACID

The acid used fillin batter# is sulphuric ravit# '.'00.00(/at )9 c

CONNECTIONS OF CELLS

The Qve terminal lu of the cell in one row is connected to the Jve lu of the end cell in

the other row. The connections b!w the two rows ma# be made with the necessar# lenth

of ?3 of the si%e used b!w the switchboard < batter#.

POLARITY OF T*E CONNECTIONS

>tCs ver# important that Qve terminal of the batter# is connected to the Qve lead of the

charin source.

To ascertain the polarit# of the charin leads connected a lamp in the series < dip the

ends in a lass of slihtl# saline water. 1witch on the suppl#. ine bubbles of the as will


45/125

be iven off from the Jve lead. The lamp connected in the series eliminates the daner of

accidental short circuit.

C*ARGING EUIPMENT

C*ARGING

*atteries have to be chared occasionall# to restore them to be in workin condition.

Durin the charin D? current is passed throuh the batter# in the direction opposite to

that when the batter# is bein used. ?harin current is usuall# obtained from batter#

charer$ which is the selenium or transformers desined to step up the voltae or down to

suitable values.

BATTREY C*ARGING EUIPMENT

The charin of batter# is done b# a s#stem known as trickle charin unit.

TRICKLE C*ARGING UNIT

loat charer

*oost charer

BRIEF DESCRIPTION OF T*E BATTERY C*ARGING

'. loat charer operates on constant voltae mode < maintains the D? output

within Q!-'B of the set value.

). The boost charer operates on constant current mode till the o!p current reaches

set value$ be#ond which it operates in constant current mode.

=. Durin charin or providin the equali%in charer to the batter# the boost

charer operates in constant current mode.


46/125

3nder normal runnin condition the D? load is connected across the float

charer < the batteries are also connected across the float charer throuh the D?

contactor < ets the trickle charer from the float charer so that if in case suddenl#

the 2? suppl# fails the batteries will suppl# the D? power to the continuous D? load

< disturbance will not be created. The float charer floats on the D? bus thatCs wh# it

is called float charer. *asicall# the float charer is provided for the continuous Dc

load < at the same time trickle charers the batteries so that when the mains fail the

load demand meet the batter# immediatel#. Now if the batter# ets dischared while

suppl#in the load. To chare the batter# aain boost chare is provided which

boostl# chares up the batter# to the desired level of the voltae.*oth the boost <

float chares are th#irosterised power supplies havin automatic voltae current

reulation features.

BOOST C*ARGER

The workin of the boost charer depends on the voltae of the cells of the batter# i.e.

when the voltae of the a sinle cell of the batter# reaches '.: volts!cell the boost charer

is automaticall# tuned @N 9 starts charin the batter# cells < remains @N till the

voltae reaches ).9 volt!cell i.e. =(.' volt of the total batter#.

The float charer will determine the load voltae. "hen the 2? suppl# is

available both the float charer < the batteries are connected across the D? cont. load.

The float charer simpl# converts the 2? suppl# to D? suppl# < feed the continuous Dc

load as well as to float the batteries at ).'6 volts!cell.

1uddenl# if now 2? fails the batteries will come across the Dc load current

requirement. Now when the 2? supplies resumes the boost charer is connected to the

batteries to rechare them with the boost ener#. *oost charer operates in the constant

current mode.

COMPONENTSS OF T*E FLOAT C*ARGER

'. >nput switch


47/125

). E;? fuses

=. ?ontractor with thermal overload rela#

&. indication lihts

(. Dc voltmeter < ammeter

WORKING

The circuit "orks on the 2? phase control principle. The 1?; is a semiconductor device

with = terminals i.e. anode cathode ate. The main load current is carried b# the anode$

cathode$ while the control current flows throuh the ate < cathode. ?haracteristics of

the 1?; are such that iot blocks the forward voltae when ate is not supplied with the

anode current. "hile it oes into conduction when ate current reaches a specified level

therefore charin the instant at which the ate current or the pulse is supplied can

control the instant at which the 1?; oes into conduction. @nce the 1?; is triered it

remains in conduction until anode current is reduced to %ero or reverse voltae is applied

anode.Thus chanin the instant of firin of the 1?;. Potentiometer ; ' is used for

ad5ustin the output voltae settin can control the output voltae of the rectifier bride.

The D? output load current is sensed b# the Dc shunt. The sinal proportional to this load

is fed to the controller. >n the event of the load current e4ceeds the rated full load current$

the output voltae starts droppin$ thus limitin the load current. This inherent is

provided in the float charer apart from the back-up.

SPECIFACTIONS OF FLOAT C*ARGER

>t is th#ristor controlled power suppl# transformer is double wound =-phase$ natural air

cooled. ;ectifier *ride is =-phase$ full wave$ half controlled. Fach device is protected

from the voltae sure with suitable suppressor network < from overload with E;? s!c

fuses. Durin overload the charer output is drops below set level$ their allowin batteries

to take current sure.loat charer is provided with >!P switch$ E;? fuse$ contactor with

thermal overload rela# $D? voltmeter < auto manual switch.

MAIN POWER SUPPLY CIRCUIT


48/125

8ain incomin power suppl# is connected to the main t!f throuh the rotar# switch$ fuses

< 2? contactors.Three indicatin lamps are provided to indicate the 2? main suppl#

available.@N < @ switch is provided for switchin @N < @ the

contactor.>ndicatin lamps indicate the contactor @8N condition.The contactor would

trip of durin phase sequences fail or 2? overload as the coil of the contactor is

connected in the series with N? contacts of the phase fail rela# < ac overload rela#.The

transformer is connected in star-delta confiuration.The secondar# of the main

transformer is connected in delta < its = outoin lines are connected to the diode/1?;

half controlled rectifier bride that consist of three diode D'$D)$D=$D& < =

1?;C1.1?;'$ 1?;)$ 1?;=.Diode is freewheelin diode.1ure suppressor ;?' T@ ;?9$

which consist of the reisters < capacitors n!w$ protect the 1?;Cs diode aainst transit

voltae.The output of the bride is filtered usin A-? circuit.The filtered output is

connected to the load circuit or batter# throuh a rotar# switch.2 shunt 1E' is used for

current limit control which is also used for output current on ammeter.2 D? voltmeter

indicates the D? output voltae.>ndicatin lamp indicates D? on condition. *lockin

diodes are used to prevent reverse current followin from the batter# to the charer."hen

the charer voltae oes below the batter# voltae or the charer is off.The D? voltmeter

reads voltae across float$ boost or batter# tap throuh a switch.

CONTROL CIRCUIT

The o!p of the charer is controlled throuh the electronic controlled. The control circuit.

Eas plu in t#pe cards with connections for e4ternal connections. The output is

controlled usin the phase control of the 1?; < feedback.

MAIN FUNCTIONAL CIRCUITS Power 1uppl#

37T firin for 1?; control

2mplifier

D? under voltae!over voltae sensin


49/125

2? under voltae!over voltae sensin

POWER SUPLLY

Power suppl# in the form of power suppl# car. >t provides ;eulated power of Q!-')volts.3nreulated power of )& volts used for >?Ls < rela#s respectivel#.

BOOST C*ARGER

>n the boost charer main T! is used to step down voltae. The primar# has suitable >!P

taps for Q!-'0B of the normal voltae. 1econdar# of the T! is directl# fed to = phase full

wave full controlled bride rectifier stack < the D? @!P is used for charin the batteries.

Durin the boost charin the D? contractor is de-eneri%ed < inhibits the e4cess

voltae of the boost charer to reach the D? load terminals. >f now durin the boost

charin of the batter# aain the 2? suppl# fails. Then the D? contractor will operate <

the full batter# voltae is provided across the load.

>n case of failure of the float charer the continuit# if the D? suppl# is maintained

throuh the blockin diodes connected throuh the tap cells of the batter#.

To cure this problem of failure of the float charer the boost charer is also used to

suppl# the D? load. *ut this is an e4traordinar# situation when the boost charer is

operated in the constant voltae mode. 2nd the D? contractor will not be DF eneri%ed

durin this time. The boost voltae is set to ).'6 volts!cell < would remain constant

within Q!-'B of the set voltae.

There are special desined features which are incorporated in the boost charer

enables it to be used as a float charer so that the dela# cause durin rectif#in the float

charer does not effect the D? suppl# s#stem.

FLOAT C*ARGER

The charer is so called because if floats on the D? bus. The charer is fed from = phase

2c suppl# < ives the D? stabili%ed @!P at rated full load current. The variation in D?


50/125

@!P voltae is limited to Q!-'B for 0-'00B load variation < simultaneousl# 2? voltae

variation of Q!-'0B < frequenc# variation of Q!-(B from (0 ER.

RELAYS

;ela# is a device that detects the fault mostl# in the hih voltae circuit. < initiates the

operation of the ?* to isolate the defective section from the rest of the circuit."henever

fault occurs on the power s#stem$ the rela# detects that fault < closes the trip coil circuit.

This results in the openin of the ?* which disconnects the fault# circuit. Thus the rela#

ensures the ensures the safel# of the circuit. equipment from damae which the fault ma#

cause.

PURPOSE OF PROTECTIVE RELAY AND RELAYING

The capital investment involved in a power s#stem for the eneration$ transmission <

distribution if electrical power is so reat that the proper precautions must be taken to

ensure that the equipment not onl# operates as nearl# as possible to peak efficienc# but

also that it is protected from accidents. The normal path of the electric current is from the

power source throuh copper conductors in the enerators$ transformers < transmission

lines to the load < it is confined to this path b# insulation. The insulation however ma#

be broken down either b# effect of temp. < ae or b# a ph#sical accident$ so that the

current then follows an abnormal path enerall# known as short-circuit or fault.

"henever this occurs the destructive capabilities of the enormous ener# the power

s#stem ma# be causes e4pensive damae to the equipment$ severe drop in the voltae <

loss of revenue due to interruption of service. 1uch faults ma# be made infrequent b#

ood desin of the power apparatus < lines the provision of protective devices$ such as

sure diverters < round fault neutrali%ers$ but a certain number will occur inevitabl# dueto lihtenin < unforeseen accidental conditions.The purpose of protective rela#s <

rela#in s#stems is to operate correct ?.* so as to disconnect onl# the fault# equipment

from the s#stem as quickl# as possible.

CONSTRUCTION:


51/125

2ll the rela#s have followin three essential fundamental elements,

9. SENSING ELEMENT:

1ometime it is also called measurin element. >t is element which is the responsible to

the chane in manitude or phase of the quantit#.

2. COMPARING ELEMENT:

>t is the element which compares the action of the actuatin quantit# of the

rela# with the pre-desined rela# settin. The rela# onl# picks up if the

actuatin quantit# is more than the rela# settin.

3. CONTROL ELEMENT:

"hen the rela# picks up it accomplishes a sudden chane in controlled quantit# such as

closin of the trip coil circuit.

TYPES:-

2ccordin to the conc. < principle of operation rela#s are of followin three t#pes.

1. THERMAL RELAYS-

The operation of these rela#s depends on the headin effect of the electric current.

2. E.M. ATTRACTION RELAYS-

These are the electromanetic rela#s. The operation of these rela#s depends

on the movement of armature under the influence of attractive forces due to

manetic field up b# current flowin throuh the rela# coil.

3. INDUCTION RELAYS-


52/125

The operation of these rela#s depends on the electromanetic induction phenomena. *#

induction$ edd# currents are induced in the 2A in the disc$ free to rotate$ which e4erts

torque on it.

VARIOUS TYPES OF RELAYS USED FOR PROTECTION

ARE:

1. OVER CURRENT RELAY-

>n this protection trip coil is eneri%ed when current in the circuit is '0 times the normal

current. This protection is applied b!w = phases.

2. INSTANTANEOUS RELAY-

The time operation of this rela# is 0.' sec. >t is more effective where impedance b!w the

sources n this protection the trip coil is eneri%ed when

the current usuall# durin startin the current is ( to 6 times the normal current.

&. UNBALANCE PROTECTION,-

>t protects aainst Jve phase sequence current. The rela# normall# used is an >D8T rela#.

(. EARTH FAULT PROTECTION,-

The s' terminals of = ?.*Cs are connected to = phases ;$$* < second terminals 1) are

connected toether. This form neutral thus connections are star connected. >deall# there is

no current in neutral. *ut if b# an# reason the circuit. 1tart to flow in the neutral the earth

fault occurs < trip coil is eneri%ed thus trippin the ?.*Cs.

. UNDER VOLTAGE RELAY-


53/125

>n this protection the coil is eneri%ed when the voltae drops to 90B of the normal

value. >tCs app. >s reverse time under voltae protection of a.c circuit capacitor$ rectifier <

m!c such as induction motorS


54/125

ELECTROSTATIC PRECIPITATOR

Dust e4tractions from industrial ases become a necessit# for environmental reasons.

8ost of the plants in >ndia use coal as fuel for eneratin steam. The e4haust ases

contain lare amount of smoke and dust$ which are bein emitted into atmosphere. This

poses a real threat to the mankind as a health ha%ards. Eence it has become necessar# to

free the e4haust ases from smoke and dust.

N( F%r I'$ta##at%' O& N+ E#!tr%$tat! Pr!/tat%r at GNDTP U't$:

The electrostatic precipitators installed at GNDTP units are desined to ive an emission

level of 9: m!N8= for a coal havin an ash content of not more than =0B. Eowever on

actual testin it has been found that emission level from F1PCs was about =.0 m!8 =. The

hih level of emission is due to the fact that coals burnt in the boiler have much hiher

ash content than what boilers are desined for. The pollution control board of Pun5ab

Govt. has specified an emission level of =:0 m!8 = from chimne#. >n order to achieve

this new emission level additional F1PCs have been installed at GNDTP *athinda.

Wo$)+% P$+5+6", -

The Flectrostatic precipitator utili%es electrostatic forces to separate the dust particle

form the as to be cleaned. The as is conducted to a chamber containin M?urtainsL of

vertical steel plates. These curtains divide the chamber into a number of parallel as

passaes. The frames are linked to each other to form a riid framework.The entire

framework is held in place b# four supports insulators$ which insulates it electricall# from

all parts$ which are rounded. 2 hih voltae D? is applied between the framework and

the round thereb# creatin a stron electrical field between the wires in the framework

and the steel curtains. The electrical field becomes stronest near the surface of the wire$

so stron that an electrical dischares. MThe ?oronaL dischare is developed alon the

wires. The as is ioni%ed in the corona dischare and lare quantities of positive and


55/125

neative ions are formed. The positive wires are immediatel# attracted towards the

neative wires b# strenth of the field induced. The neative ions however have to travel

the entire space between the electrodes to reach the positive curtains. @n routes towards

the steel curtains the ions collide with each other and et chared and also this chare is

transferred to the particles in the as. The particles thereb# become electricall# chared

and also bein to travel in the same direction as the ions towards the steel curtains. The

electrical force on each particle becomes much reater than ravitational force. The speed

of miration towards the steel curtains is therefore much reater than the speed of

sedimentation in free fall.

G'ra# D$!r/t%': -

There various parts of the precipitators are divided into two roups, -

a. 8echanical s#stem comprisin of casin$ hoppers$ as distribution s#stem$

collectin and emittin s#stems$ rappin mechanism$ stairwa# and alleries.


56/125

b. Flectrical s#stem comprisin of transformer rectifier units with Flectronic

?ontroller$ 2u4iliar# ?ontrol Panels$ 1afet# >nterlocks and ield Fquipment

Devices.

1) Pr!/tat%r Ca$' : -

The precipitator casin is an all welded pre-fabricated wall and roof panels. The casin is

provided with inspection doors for entr# into the chamber at each field. The doors are of

heav# construction with machined surface to ensure a as tiht seal.

The roof carries the precipitatorCs internals$ insulator housins$ transformers etc. The

casin rests on roller supports which allows for free thermal e4pansion of the casin

durin operatin conditions. Galleries and stairwa# are provided on the sides of the

casin in eas# access to rappin motors$ inspection doors$ transformers etc. walkwa#s

are provided inside FP between fields for inspection and maintenance. The dust is


57/125

collected in lare quantities on the curtains$ the collected electrodes. Due to periodic

rappin$ the dust falls into the hopper.

) Ho66$, -

The hoppers are si%ed to hold the ash for : hrs. ?ollection. *uffer plates provided in

each hopper to avoid as leakae. >nspection door is provided on the one side of

hoper wall. Thermostaticall# controlled heatin elements are arraned at the bottom

portion of the hopper to ensure free flow of ash.

= G! D+$+78+o S9:, -

The ood performance of the precipitators depends on the event distribution of as over

the entire cross-section of the field. 2s the as e4pands ten-fold while enterin the precipitator$ uide vanes$ splitters and screens are provided in the inlet funnel to

distribute the flue as evenl# over the entire cross section of the FP.


58/125

& C%##!t' E#!tr%( $1$t): -

The collectin plates are made of '.6 mm cold rolled mild steel plate and shaped in piece

b# roll formin. The collectin plates and shaped in one piece b# roll formin. The

collectin electrode has unique profile with a special confiuration on its lonitudinal

edes. This profile is desined to ive riidit# and to contain the dust in quiescent %one

free from re-entertainment+ collectin plates are provided with hooks at their top ede for

suspension. The hooks enae in slot of the supportin anle. 2ll the collectin plates in

arrow are held in position b# a shock bar at the bottom. The shock bars are spaced b#

uides.

iure, - TYPICAL COLLECTION PLATES

5) E)tt' E#!tr%( $1$t): -

The most essential part of precipitators is emittin electrode s#stem. our insulators

support this$ the frames for holdin the emittin electrodes are located centrall# between


59/125

collectin electrodes curtains. The entire dischare frames are welded to form a riid bo4

like structure. The emittin electrodes are kept between the frames.

F: R( &ra) ($!,ar #!tr%( ($'

6 Ra//' S1$t): -

;appin mechanism is provided for collectin and emittin electrodes. Geared motors

drive the rappin mechanism. The rappin s#stem emplo#s tumblin hammers$ which are

mounted on a hori%ontal shaft. 2s the shaft rotates slowl# the hammers which are

mounted on a hori%ontal shaft. 2s the shaft rotates slowl# the hammers tumble on the

shock bar!shock$ which transmits blow to the electrodes. @ne complete revolution of the

rappin shaft will clean the entire field. The rapper prorammer decided the frequenc# of

rappin. The tumblin hammers disposition and the periodicit# of the rappin are

selected in such a wa# that less than )B of the collectin area is rapped at one time. This

avoids re-entertainment of dust and puffin at the stock outlet.


60/125

The rappin shaft of emittin electrodes s#stem is electrical isolated from the eared

motor driven b# a shaft insulator. The space around the shaft insulator is continuousl#

heated to avoid condensation.

ollowin 2re the 8odules for the @utoin eeders, -

• Eopper heater for each field

• 1upport insulator heaters.

• 1haft insulator heaters.

• ?ollectin electrode-rappin motor for each field.


61/125

• Fmittin electrode rappin motor for each filed.

*, V%#ta Tra'$&%r)r R!t&r 4*VR5 +t, E#!tr%'! C%'tr%##(

4EC5: -

The rectifier supplies the power for as particle charin and collection. The basic

function of the F? is to feed the precipitator with ma4imum power input under constant

current reulation should there be an# flash between collectin and emittin electrodes$

the F? will sense the flash and quickl# react b# brinin the input period voltae to %ero

and blockin it for a specific period. 2fter the ioni%ed ases are cleaned and the dielectric

strenth restored$ the control will quickl# brin back the power to a present value and

raise it to the oriinal non-sparkin level. Thus the F? ensure the electrical disturbance

within precipitator. ;eulated 2? power from F? is fed to the primar# of the

transformer$ which is stepped up and rectified to ive a full wave power output. The

transformer is mounted on roof of the precipitator while the F? is located in an air

conditional room.

A";#ar1 C%'tr%# Pa'# 4ACP5: -

The 2?P houses the power and circuits required for eneri%in rappin motor and

heatin elements of the precipitator. 2?P controls each as path. The complete 2?P is of

modular t#pe with individual module for each feeder. Fach module houses the power and

control circuit with meters. Push buttons$ witches and indicatin lamps are mounted on

the door of the compartments.

Ma;)t should be the aim of ever# operator to ma4imi%e the performance b#

5udiciousl# ad5ustin the controllable variables.

C#a'' O& E#!tr%($: -

The performance of the F1P depends on the amount of electrical power absorbed b# the

s#stem. The hihest collection efficienc# is achieved when ma4imum possible electric

power for a iven set of operatin conditions is utili%ed on the fields. Too thick a dust

la#er on the collectin plates will lead to drop in the effective voltae$ which


62/125

consequentl# reduces the collection efficienc#. >t also leads to unstable to unstable

operatin conditions. Therefore the rappin s#stem of collectin and emittin electrodes

should be kept in perfectl# workin condition. 2ll the rappin motors have been

prorammed to achieve the optimum efficienc#.

A$, *%//r E2a!"at%': -

>mproper!incomplete hopper evacuation is a ma5or cause for the precipitator

malfunction. >f the hopper are not emptied reularl#$ the dust will build up to the hih

tension emittin s#stem causin shot circuitin. 2lso the dust can push the internals up

causin misalinment of the electrodes. Thouh the hoppers have been desined for a

storae capacit# of : hours$ under 8?; conditions$ this provision should be used in case

of emerenc#. Normall#$ the hopper should not be rearded as storae as storae asstorae space for the collected ash.

O# !%)="$t%': -

The combustion of oil used durin start up or for stabili%ation of the flames can have an

important impact on precipitator operation. 3n burnt oil$ if passed into F1P can deposit

on the emittin and collectin electrodes and deteriorates the electrical condition i.e.

reduce the precipitators operatin voltae due to hih electrical resistivit# and

consequentl# the F1PCs performance is affected adversel#. The precipitator performance

remains poor until the oil vapori%es and the ash la#er ets rapped off$ which usuall# takes

alon time.

TEC*NICAL DATA OF ELECTROSTATIC PRECIPITATOR COLLECTING ELECTRODE

'. Total No. of collectin plates). Nominal heiht of collectin plate

=. Nominal Aenth of collectin plate

)&:0 ').( m

&00 mm


63/125

EMITTING ELECTRODES

'. T#pe

). 1i%e

=. No. of electrodes in each field

&. Plate!"ire spacin.

1piral

).9mm

'&&0

'(0 mm

RAPPERS FOR COLLECTING ELECTRODES

'. No. < t#pe of

rapper

@ne drop hammer per row

of collectin electrodes

D+% Co;++o U+1,3,4

'. Gas flow rate). Temperature

=. Dust concentration

&. Number of precipitator

(. Number of as path per boiler

6. No. of fields in series in each

as pass

)00m=!sec '&(0 ?

=:. ms!Nm=

@ne

)

(


64/125

).requenc# of

;ap

=.Drive

&.Aocation

surface area 0 m)

ar#in from ') raps!hr at

the inlet field to ' rap!hr at

e4ist

Geared electric motor?ontrolled b# s#nch.

prorammer

2t the bottom of

collectin s#stem

RAPPERS FOR EMMITING ELECTRODES

'.No. and t#pe of rappers

). requenc# of ;ap

=. Driver

&. Aocation

2ppro4. one drop hammers!tworows of electrodes

'0 raps!hour

Geared Flectric 8otor controlled b#

1#nch. Prorammer

@n the side of emittin frame

middle position

HOPPERS

'. T#pe

).No of Eoppers

=. ?apacit#

P#ramidal

)0

: hour storae

MOTORS RAPPING OF EMMITING ELECTODE

'. Kuantit# '0 Nos.


65/125

). ;atin

=. Aocation

Geared 8otor

0.==hp!).( rpm at =-

phase &'( (0 E%

@n the top FP

RAPPING OF COLLECTING ELECTODE

'. Kuantit#

). ;atin

=. Aocation

'0 Nos.

Geared 8otor$ ==

hp!).( rpm at =

Phase &'( (0 E%.

@n the top FP

ELECTRICAL ITEM

RECTIFIERS

'. ;ectifier ;atin

). Number!*oiler

=. T#pe

&. Aocation

90 I /peak :00 82 /8ean

'0

1ilicon Diode ull "ave$

*ride connection

8ounted on the top of

precipitator

RECTIFIER CONTROL PANEL


66/125

'. T#pe of ?ontrol

). Aocation

Th#ristor

>n the ?ontrol ;oom


67/125

B%#r $!t%'

The steam eneratin unit is desined to meet the nominal requirements of ''08" turbo

enerator set. The unit is desined for a ma4imum continuous ratin of =9( tones!hr. at a

pressure of '=k!cm) and a steam temperature of (&00°?. the reheated steam flows at

8?; =)E tones!hr. at the feed water temp at 8?; is )&00°?. The unit is a balance

drauht dr# bottom+ sinle drum natural circulation$ vertical water tube t#pe$ construction

with skin casin and a sinle reheat s#stem. The furnace is arraned for dr# ash dischare

and is fitted with burners located at the four corners. Fach corner burner comprises coal$

vapour oil and secondar# air compartments. The unit is provided with three ball mills and


68/125

arraned to operate with intermediate cool powder bunker. The steam super heater

consists of & staes i%. ?eilin$ convection$ platen and final superheated. The ceilin

super heated forms the roof of the furnace and hori%ontal pass and finishes as the rear

wall of the second pass. The convection super heated is made up of hori%ontal banks

located in the second pass. "hile the platens are located at the furnace e4it$ the portion

above the furnace nose encloses the final superheated reheater are in two staes$ first

stae is the triflu4 heat e4chaners located in the second pass$ which absorbs heat from

superheated steam as well as from the flue ases. The second stae is e4it reheater

located in the hori%ontal pass as pendant tubular loops.

/a The flue as for dr#in the cool in the mills is tapped off after the triflu4 heat

e4chaners. The damper located in the hot flue ases pipe leadin to mill controls the

quantit#. ?ontrol the circulatin vapour of the mill entr# effect temperature control.

>mmediatel# after the triflu4 heat e4chaner$ the air heaters and economi%ers are located.

The air heater is in ) staes.

/b The hot air for combustion from air heater stae ) is led into the common wind bo4

l

guru nanak dev thermal power.docx

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