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A Free sample background from www.powerpointbackgrounds.com

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B"#$ make %nstrumentB"#$ make %nstrument&ransformers&ransformers

More than 35 years of Experience

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B"#$ make %nstrument &ransformersB"#$ make %nstrument &ransformers

"ig' reliability is demanded from application"ig' reliability is demanded from applicationpoint of (iew) w'ic' is ade*uately e+'ibitedpoint of (iew) w'ic' is ade*uately e+'ibited, pro(en by successful operation of B"#$, pro(en by successful operation of B"#$make %nstrument &ransformersmake %nstrument &ransformers

-e are able to meet di(erse demands of-e are able to meet di(erse demands of(arious clients(arious clients

ur %nstrument &ransformers conform to t'eur %nstrument &ransformers conform to t'elatest pro(isions of %ndian as well aslatest pro(isions of %ndian as well as%nternational standards%nternational standards

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Major CustomersMajor Customers

B"#$ make %nstrument &ransformersB"#$ make %nstrument &ransformersare in successful operation at (ariousare in successful operation at (arious

sub stations ofsub stations of/&1) owerrid) #B) 41$)/&1) owerrid) #B) 41$)&/#B) BBB) 5#B) 5&1$) /eepco)&/#B) BBB) 5#B) 5&1$) /eepco)#B)-B#B etc.#B)-B#B etc.

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Instrument TransformersInstrument Transformers

%nstrument &ransformers are subdi(ided as7%nstrument &ransformers are subdi(ided as7

8 1urrent &ransformers) utdoor type1urrent &ransformers) utdoor type

8 9oltage &ransformers ........:9&9oltage &ransformers ........:9&

9&s are again of two types9&s are again of two types

8 agnetic 9oltage &ransformers ;9&

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Current TransformersCurrent Transformers

"ig'ly reliable operation of current transformers is"ig'ly reliable operation of current transformers issuccessfully pro(ed by7successfully pro(ed by7

8 artial disc'arges wit'in specified limitsartial disc'arges wit'in specified limits

8 "ig' s'ort time current wit'stand tested for 60 kA for 3 econds"ig' s'ort time current wit'stand tested for 60 kA for 3 econds 8 Our 400 kV CTS are capa!e to "ithstan# 50 k$ for oneOur 400 kV CTS are capa!e to "ithstan# 50 k$ for one

Secon# the fau!t !e%e! foreseen y &0'&Secon# the fau!t !e%e! foreseen y &0'&

8 uitable to wit'stand abnormal stresses due to operation ofuitable to wit'stand abnormal stresses due to operation ofisolators) $As) breakersisolators) $As) breakers

8 &'ermal stability pro(ed by tests&'ermal stability pro(ed by tests

8 $ow temperature coefficient of &angent delta ensures 'ig'$ow temperature coefficient of &angent delta ensures 'ig'stability of insulation e(en at ele(ated (oltagesstability of insulation e(en at ele(ated (oltages

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(e!iai!ity(e!iai!ity

B"#$ make instrument transformers 'a(eB"#$ make instrument transformers 'a(eperformed in #"9 systems e+ceptionally wellperformed in #"9 systems e+ceptionally well

4se of our instrument transformers ensures4se of our instrument transformers ensureslong trouble free ser(ice) w'ic' meanslong trouble free ser(ice) w'ic' meansa(ailability of protection w'en neededa(ailability of protection w'en needed

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Manufacturin) *rocessManufacturin) *rocess

All stages of anufacturing rocess are according to B"#$ All stages of anufacturing rocess are according to B"#$procedures , @uality assurance system w'ic' is certified toprocedures , @uality assurance system w'ic' is certified to% 00‑% 00‑

&'e main insulation , assembly are done in a clean&'e main insulation , assembly are done in a cleansurrounding in order to a(oid contamination.surrounding in order to a(oid contamination.

Before filing wit' processed insulating transformer oil) t'eBefore filing wit' processed insulating transformer oil) t'etransformers are dried under (acuum so as to reduce t'etransformers are dried under (acuum so as to reduce t'emoisture contentmoisture content

#ffecti(e sealing is pro(ided to enable negligible moisture le(el#ffecti(e sealing is pro(ided to enable negligible moisture le(elduring ser(ice.during ser(ice.

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+enera! ,escription of Out#oor+enera! ,escription of Out#oorCurrent TransformersCurrent Transformers

utdoor 1&s are basically of 3 types ofutdoor 1&s are basically of 3 types of

1onstruction1onstruction

Dead &ank wit' 4 ;"air in< s'aped Dead &ank wit' 4 ;"air in< s'aped

primaryprimary

2 Dead &ank wit' #ye Bolt primary2 Dead &ank wit' #ye Bolt primary

3 $i(e &ank or %n(erted primary 1&3 $i(e &ank or %n(erted primary 1&

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1onstructional Details of B"#$1onstructional Details of B"#$make 1&smake 1&s

-e at B"#$ manufacture "air pin-e at B"#$ manufacture "air pin CTsCTsbecause of pro(en e+ceptionally 'ig'because of pro(en e+ceptionally 'ig'reliability , suitable for eart' *uake pronereliability , suitable for eart' *uake prone

areasareas

&'ese 1&s are il filled and 'ermetically&'ese 1&s are il filled and 'ermetically

sealed wit' /itrogen gas cus'ionsealed wit' /itrogen gas cus'ion

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1onstructional Details of B"#$1onstructional Details of B"#$

make 1&smake 1&s

&'e primary is linked wit' independent&'e primary is linked wit' independentsecondary ring cores 'a(ing windingssecondary ring cores 'a(ing windingsconnected to terminal bo+ on t'e tank side.connected to terminal bo+ on t'e tank side.

&'e w'ole assembly forms a common space&'e w'ole assembly forms a common spacefor oil and is sealed from t'e atmosp'ere)for oil and is sealed from t'e atmosp'ere)

t'e top c'amber ser(ing as an e+pansiont'e top c'amber ser(ing as an e+pansionc'amber.c'amber.

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Constructiona! ,etai!s ofConstructiona! ,etai!s of

-.E/ make CTs-.E/ make CTs &'e space abo(e t'e oil is filled wit'&'e space abo(e t'e oil is filled wit'

nitrogen w'ic' acts as a cus'ion fornitrogen w'ic' acts as a cus'ion forc'anges in oil (olume due toc'anges in oil (olume due totemperature and load current (ariations.temperature and load current (ariations.

&'e positi(e pressure of nitrogen inside&'e positi(e pressure of nitrogen insidepre(ents contamination from outsidepre(ents contamination from outsideatmosp'ere) t'ereby pro(ide effecti(eatmosp'ere) t'ereby pro(ide effecti(e'ermetical sealing.'ermetical sealing.

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Application of 1urrent Application of 1urrent&ransformers&ransformers

1urrent &ransformers are furt'er1urrent &ransformers are furt'erclassified from application point intoclassified from application point into

8 Meterin)Meterin) CTs CTs

8 *rotecti%e*rotecti%e CTsCTs

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$pp!ication of CTs$pp!ication of CTs

&'e duty of t'e etering 1&s re*uires&'e duty of t'e etering 1&s re*uires'ig'er accuracy o(er t'e normal'ig'er accuracy o(er t'e normaloperating current rangeoperating current range

&'e duty of t'e rotecti(e 1&s re*uires&'e duty of t'e rotecti(e 1&s re*uiresspecified accuracy for correctspecified accuracy for correct

reproduction during t'e passage of t'ereproduction during t'e passage of t'eabnormal current t'roug' primary due toabnormal current t'roug' primary due tosystem fault conditions.system fault conditions.

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ulti ratio 1& , selection of ratiosulti ratio 1& , selection of ratios;e.g. =0 200 300 C

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,isa#%anta)es of *rimary,isa#%anta)es of *rimaryreconnectionsreconnections

'ort circuit forces increases at 'ig'er primary'ort circuit forces increases at 'ig'er primaryturnsturns

4seful only w'en ratios are in geometric4seful only w'en ratios are in geometricproportions ;e.g. =0 300 >00 C 00 C <

Eeconnection is possible only after s'utdown ,Eeconnection is possible only after s'utdown ,opening of line connectionsopening of line connections

%n case of multi core 1&s) independent selection of%n case of multi core 1&s) independent selection ofratio is not possibleratio is not possible

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$#%anta)es of *rimary (econnections$#%anta)es of *rimary (econnections

Fi+ed secondary outputFi+ed secondary output

"ig'er Amp. &urns e(en at lower ratio"ig'er Amp. &urns e(en at lower ratioleading to better accuracy , reduced coreleading to better accuracy , reduced coresiesie

imple secondary windingimple secondary winding

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Some specia! features ofSome specia! features of

Instrument TransformersInstrument Transformers roper drying of t'e paper insulation used inroper drying of t'e paper insulation used in%nstrument &ransformers is an essential%nstrument &ransformers is an essentialpre re*uisite for its long and trouble free‑pre re*uisite for its long and trouble free‑

ser(iceser(ice

-e ensure t'at t'e paper insulation used is-e ensure t'at t'e paper insulation used is

in a state of perfect dryness by continuousin a state of perfect dryness by continuousmonitoring of t'e processmonitoring of t'e process

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Technica! features of -.E/ makeTechnica! features of -.E/ make

400 kV C Ts400 kV C Ts

"air pin design 'a(ing porcelain wit'"air pin design 'a(ing porcelain wit'metallic flanges w'ic' is e+tremely robustmetallic flanges w'ic' is e+tremely robustand stable.and stable.

-ell adapted against eismic forces-ell adapted against eismic forces

"ig' reliability pro(ed in ser(ice"ig' reliability pro(ed in ser(ice

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400 kV C Ts400 kV C Ts ositi(e pressure of /itrogen is pro(ided o(er oil forositi(e pressure of /itrogen is pro(ided o(er oil for

'ermetical sealing) w'ic' controls contamination of'ermetical sealing) w'ic' controls contamination ofoil. &'us 1& is practically maintenance freeoil. &'us 1& is practically maintenance free

"ig' conducti(ity copper tube is used as primary"ig' conducti(ity copper tube is used as primary

winding ensuring better t'ermal and mec'anicalwinding ensuring better t'ermal and mec'anicalperformance) during fault conditionsperformance) during fault conditions

&otal independent selection of ratios t'roug' taps&otal independent selection of ratios t'roug' tapson secondary windings pro(ides operationalon secondary windings pro(ides operational

simplicity wit' indi(idualistic ratio selection on anysimplicity wit' indi(idualistic ratio selection on anysecondary coresecondary core

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400 kV C Ts400 kV C Ts

etering core is carefully designed toetering core is carefully designed topro(ide safety to t'e connectedpro(ide safety to t'e connectedinstruments from too large a (alue ofinstruments from too large a (alue ofo(er current during fault conditions.o(er current during fault conditions.

-it' t'e nearby "ig' power s'ort circuit-it' t'e nearby "ig' power s'ort circuit1E% test station) all ot'er &esting1E% test station) all ot'er &esting

facilities for complete routine and typefacilities for complete routine and typetests for 'ig' (oltage are a(ailabletests for 'ig' (oltage are a(ailable

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Technica! features of -.E/ makeTechnica! features of -.E/ make400 kV C Ts400 kV C Ts

1&s 'a(e been demonstrated to be1&s 'a(e been demonstrated to bee+ceptionally robust to wit'stand 'ig'e+ceptionally robust to wit'stand 'ig'fre*uency FA& transient currents asfre*uency FA& transient currents as

prescribed by 1%E#.prescribed by 1%E#.

uc' transients are now known to 'a(e leduc' transients are now known to 'a(e ledto catastrop'ic failures of 1&s worldwide.to catastrop'ic failures of 1&s worldwide.

&'e appearance of suc' transients is&'e appearance of suc' transients ise+plained undere+plained under “Unusual Stresses” “Unusual Stresses”

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+enera! ,esi)n $spects CTs+enera! ,esi)n $spects CTs

Fi(e main factorsFi(e main factors

8 Eated rimary 1urrentEated rimary 1urrent

8 Eated 'ort time 1urrentEated 'ort time 1urrent

8 %nsulation $e(el%nsulation $e(el

8 ollution re*uirementollution re*uirement

8 Burden , Accuracy on different secondary coresBurden , Accuracy on different secondary cores

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+enera! ,esi)n $spects 1 CTs+enera! ,esi)n $spects 1 CTs

(ate# *rimary Current(ate# *rimary Current&'e design is made according to t'e standards&'e design is made according to t'e standards

for permitted temperature rise o(er t'efor permitted temperature rise o(er t'e

specified ambient for t'e continuous Eatedspecified ambient for t'e continuous Eatedrimary 1urrent. &'e e+tended current ratingrimary 1urrent. &'e e+tended current ratingif specified is to be taken care of.if specified is to be taken care of.

&'e e+tended current rating may be from 20G&'e e+tended current rating may be from 20G

to 200G.to 200G.&'e e+tended current means t'at accuracy is&'e e+tended current means t'at accuracy ismaintained up to t'at le(el and 1& canmaintained up to t'at le(el and 1& cancontinuously carry t'e t'ermal current e*ualcontinuously carry t'e t'ermal current e*ualto t'e rated e+tended currentto t'e rated e+tended current

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+enera! ,esi)n $spects 1 CTs+enera! ,esi)n $spects 1 CTs

(ate# Short time Current(ate# Short time Current &'is is t'e ma+imum t'ermal current %&'is is t'e ma+imum t'ermal current % t't' w'ic'w'ic'

must be wit'stood by 1& for a period of onemust be wit'stood by 1& for a period of onesecond. &'e ma+imum temperature permittedsecond. &'e ma+imum temperature permitted

for oil insulated 1&s is 2=0 Deg.1.for oil insulated 1&s is 2=0 Deg.1. %t is essential t'at 1& can safely wit'stand t'e%t is essential t'at 1& can safely wit'stand t'e

fault current flowing t'roug' it. %n t'efault current flowing t'roug' it. %n t'ee(entuality of 1& failure t'e entire associatede(entuality of 1& failure t'e entire associatede*uipment is left unprotected as no signal wille*uipment is left unprotected as no signal will

be a(ailable to relay for decision making.be a(ailable to relay for decision making. &'e dynamic wit'stand is calculated by t'e first&'e dynamic wit'stand is calculated by t'e first

current peak w'ic' can reac' 2.= times t'e %current peak w'ic' can reac' 2.= times t'e % t't'

eneral Design Aspects 1&s

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© 003 y e au t


de =

%f s'ort time wit'stand current is not%f s'ort time wit'stand current is notspecified) it can be estimated byspecified) it can be estimated by

con(erting t'e Fault le(el in 9A to s'ortcon(erting t'e Fault le(el in 9A to s'orttime current using t'e rated (oltage) or)time current using t'e rated (oltage) or)t'e breaking capacity of t'e associatedt'e breaking capacity of t'e associatedbreaker may be usedbreaker may be used

For 600 k9 1&s t'e 'ort time ratedFor 600 k9 1&s t'e 'ort time ratedcurrent is gi(en as 60 kA for one econdcurrent is gi(en as 60 kA for one econd

'ort &ime 1urrent ;%t'<

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y


&'e peak (alue of t'e dynamic current gi(es&'e peak (alue of t'e dynamic current gi(esrise to t'e electromagnetic forces between t'erise to t'e electromagnetic forces between t'eprimary winding turns or arms of t'e 'airpin.primary winding turns or arms of t'e 'airpin.

&'e force is proportional to t'e s*uare of t'is&'e force is proportional to t'e s*uare of t'isdynamic peak currentdynamic peak current

%t is essential t'at 1& s'ould wit'stand bot' t'e%t is essential t'at 1& s'ould wit'stand bot' t'et'ermal effects of s'ort time current as well ast'ermal effects of s'ort time current as well ast'e forces due to t'e dynamic currentt'e forces due to t'e dynamic current

'ort &ime 1urrent ;%t'<

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y


&'e 1&s or t'e %nstrument &ransformers must&'e 1&s or t'e %nstrument &ransformers mustwit'stand t'e continuous operational (oltagewit'stand t'e continuous operational (oltageand also t'e o(er(oltages of t'e network.and also t'e o(er(oltages of t'e network.&'ese include7&'ese include7

8 A1 one minute test (oltage A1 one minute test (oltage

8 $ig'tning %mpulse wit'stand (oltage$ig'tning %mpulse wit'stand (oltage

8 witc'ing %mpulse wit'stand (oltage aswitc'ing %mpulse wit'stand (oltage asdefined for 300 k9 and abo(e systemdefined for 300 k9 and abo(e system(oltages(oltages

8 "ig'est ystem (oltage 4m"ig'est ystem (oltage 4m

Insu!ation /e%e!Insu!ation /e%e!

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y


*rimary 2in#in)*rimary 2in#in)

&'e primary winding insulation is&'e primary winding insulation isdesigned on t'e basis of e*ualdesigned on t'e basis of e*ualcapacitance and uniform A+ialcapacitance and uniform A+ial

stresses principle.stresses principle.

&'e insulation of 330 and 600 k9&'e insulation of 330 and 600 k91&s is formed from > e*ual1&s is formed from > e*ual

capaciti(e grading steps formedcapaciti(e grading steps formedfrom t'e insertion of Aluminium foilsfrom t'e insertion of Aluminium foilsbetween "ig' *uality 5raft paper between "ig' *uality 5raft paper

PP1

CORE 5

CORE 4

CORE 1

CORE 2

CORE 3

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y


*o!!ution Con#ition*o!!ution Con#ition

&'e total creepage is specified according&'e total creepage is specified accordingto %#17 66 for t'e pollution condition asto %#17 66 for t'e pollution condition as

8 /i)ht Me#ium .ea%y an# Very hea%y/i)ht Me#ium .ea%y an# Very hea%y

w'ere t'e minimum creepage distance of t'ew'ere t'e minimum creepage distance of t'eporcelain weat'er casing is >) 20) 2= , 3porcelain weat'er casing is >) 20) 2= , 3

mmCk9 respecti(ely.mmCk9 respecti(ely.

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&'e primary of 1& is connected in series&'e primary of 1& is connected in serieswit' t'e transmission line , t'us t'ewit' t'e transmission line , t'us t'eprimary current is not affected by t'eprimary current is not affected by t'eburden of 1& secondary coresburden of 1& secondary cores

/eglecting e+citing current of 1& core)/eglecting e+citing current of 1& core)from t'e principle of e*ual Ampere&urns)from t'e principle of e*ual Ampere&urns)t'e primary and secondary 1urrents of 1&t'e primary and secondary 1urrents of 1&are related by7are related by7

s

p p

s

N

I N I

×

=

Burden and AccuracyBurden and Accuracy

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&'e errors in t'e 1& are introduced by&'e errors in t'e 1& are introduced by

t'e e+citing current as s'own in t'et'e e+citing current as s'own in t'ee*ui(alent circuit , its simplifiede*ui(alent circuit , its simplified(ersion7(ersion7

-ur#en an# $ccuracy-ur#en an# $ccuracy

B4ED#/

ip %sie

iw wli

B4ED#/

ip ie %s

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&'e error in t'e 1& is introduced by t'e&'e error in t'e 1& is introduced by t'ee+citing current %e+citing current %ee as can be seen by t'eas can be seen by t'erelation7relation7

%%pp H % H %ee I %I %ss ) or ) or

%%ss HH %%pp % %ee


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ErrorsErrors

&'e e+citing current %&'e e+citing current %ee introduces errors inintroduces errors inratio and p'ase) w'ic' are defined byratio and p'ase) w'ic' are defined bystandards as7standards as7

100

.

)( ×

−

=

p

p sn

I

I I K

Error RatioCurrent

Phase displacement:

&'is is t'e p'ase angle difference betweenprimary , econdary 1urrent 9ectors , is

positi(e w'en econdary current leads

primary current

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0 0.2 0.4 0.60

5

10

15

20

Ma)netisin) Characteristic Cur%e of C(+O M4 +ra#e

Exciting Current in Amp/cm

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0 1 2 3 40

5

10

15

20

Ma)netisin) Characteristic Cur%e of C(+O M4 +ra#e

Exciting Current in Amp/cm

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For keeping t'e e+citing current lowFor keeping t'e e+citing current low

8 Flu+ density in t'e 1& core is kept low)Flu+ density in t'e 1& core is kept low)

8 &'e 1& core diameter must be reduced&'e 1& core diameter must be reduced

8 &'e A &4E/ are made as 'ig' as possible.&'e A &4E/ are made as 'ig' as possible.


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$$ccuracy

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$ccuracy$ccuracy

&'e 1& error is in(ersely proportional to t'e&'e 1& error is in(ersely proportional to t'es*uare of Ampere &urnss*uare of Ampere &urns

&o get 'ig' accuracy wit' low (alue of&o get 'ig' accuracy wit' low (alue ofinstrument security factor t'e core material isinstrument security factor t'e core material ismade of /ickel %ron alloymade of /ickel %ron alloy

Meterin) coresMeterin) cores 7 &o protect t'e meters and7 &o protect t'e meters andinstruments from t'e damaging effects of 'ig'instruments from t'e damaging effects of 'ig'fault currents t'e core must be designed tofault currents t'e core must be designed to

saturate at say = to 0 times rated currentsaturate at say = to 0 times rated current

.. F)F) Instrument Security actor Instrument Security actor in generalin general

indicates t'e o(er current e+pressed as aindicates t'e o(er current e+pressed as amultiple of t'e rated current. &'is ismultiple of t'e rated current. &'is is

applicable only at t'e rated burden.applicable only at t'e rated burden.

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&'e accuracy class is maintained from 2=G&'e accuracy class is maintained from 2=Gto 'undred per cent of t'e rated burden.to 'undred per cent of t'e rated burden.

&'erefore if 'ig' 9A burden is specified t'e&'erefore if 'ig' 9A burden is specified t'eerrors will increase at lower burdens due toerrors will increase at lower burdens due tot'e in(ariable use of t'e &4E/ correction.t'e in(ariable use of t'e &4E/ correction.

ince t'e minimum error is generally reac'edince t'e minimum error is generally reac'edbetween =0 ?=G of rated burden) t'e corebetween =0 ?=G of rated burden) t'e corecan be optimised by setting t'e rated burdencan be optimised by setting t'e rated burdenat about .= times t'e real burden.at about .= times t'e real burden.


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nusua! Stresses in E.V CTsnusua! Stresses in E.V CTs

&'e understanding of 'ig' fre*uency&'e understanding of 'ig' fre*uencystresses in 4"9 systems and ot'erstresses in 4"9 systems and ot'erconsiderations suc' as t'ermal stability etc.considerations suc' as t'ermal stability etc.makes it possible to critically re(iew designsmakes it possible to critically re(iew designs

and produce most reliable %nstrumentand produce most reliable %nstrument&ransformers&ransformers

&'e 'ig' fre*uency stresses in #"9 1&s can&'e 'ig' fre*uency stresses in #"9 1&s canbe represented on a one ofbe represented on a one of

amp!itu#e fre6uency p!ane‑amp!itu#e fre6uency p!ane‑ . For e+ample in. For e+ample in600 k9 1&s t'e amplitude is up to600 k9 1&s t'e amplitude is up to '000 kV'000 kV ,,fre*uency fromfre*uency from '00 k.7 to 51&0 M.7'00 k.7 to 51&0 M.7

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nusua! Stressesnusua! Stresses8Cont9#:8Cont9#:

&'e traditional tests t'erefore did not co(er&'e traditional tests t'erefore did not co(ert'e stresses produced by disconnector)t'e stresses produced by disconnector)breaker or $A operation in a station for a 600breaker or $A operation in a station for a 600k9 system.k9 system.

&'e operation of t'e %solator is t'e most&'e operation of t'e %solator is t'e mostdangerous for t'e 600 k9 1&s. /umerousdangerous for t'e 600 k9 1&s. /umerousarcing disc'arges take place w'ene(er it isarcing disc'arges take place w'ene(er it is

opened or closed to put t'e (oltage on t'eopened or closed to put t'e (oltage on t'ebus bar or to take away t'e energisation frombus bar or to take away t'e energisation fromt'e busbar.t'e busbar.

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$et us consider t'e closing of t'e$et us consider t'e closing of t'edisconnector.disconnector.

-'en t'e gap between t'e poles starts to-'en t'e gap between t'e poles starts toreduce during closing operation t'e firstreduce during closing operation t'e firstdisc'arge will take place between poles atdisc'arge will take place between poles at(oltage ma+imum.(oltage ma+imum.


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Because of sudden c'ange of t'e (oltage fromBecause of sudden c'ange of t'e (oltage fromero ;%gnoring t'e c'arge in t'e busbar due toero ;%gnoring t'e c'arge in t'e busbar due tot'e capaciti(e coupling< to t'e crest of t'et'e capaciti(e coupling< to t'e crest of t'esystem (oltage) t'e 'ig' fre*uency current willsystem (oltage) t'e 'ig' fre*uency current willflow.flow.

&'is wa(e t'en spreads on t'e bus bar and&'is wa(e t'en spreads on t'e bus bar andsuccessi(e reflections of t'ese wa(es leads tosuccessi(e reflections of t'ese wa(es leads to'ig' fre*uency oscillations. &'ere are many'ig' fre*uency oscillations. &'ere are many

resonant fre*uencies due to t'e presence ofresonant fre*uencies due to t'e presence ofdifferent inductances and capacitances.different inductances and capacitances.


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&'e capacitance of t'e %nstrument&'e capacitance of t'e %nstrumenttransformer and ower transformer mainlytransformer and ower transformer mainlysupports t'is current. &'e disc'arge ceasessupports t'is current. &'e disc'arge ceaseswit'in a few microsecondswit'in a few microseconds

.. &'e Jaws of t'e disconnector after some&'e Jaws of t'e disconnector after some

milliseconds again s'all 'a(e t'e disrupti(emilliseconds again s'all 'a(e t'e disrupti(edisc'arge but at a lesser (oltage. &'is rate ofdisc'arge but at a lesser (oltage. &'is rate ofspark o(er increases as t'e poles get nearer.spark o(er increases as t'e poles get nearer.

-'en t'e disconnector arms are nearer in a-'en t'e disconnector arms are nearer in a600 k9 network) as many as 60 restrikes can600 k9 network) as many as 60 restrikes cantake place across its slowly mo(ing poles.take place across its slowly mo(ing poles.


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Due care in design is e+ercised to a(oidDue care in design is e+ercised to a(oidformation of large (oltage drop patc'es atformation of large (oltage drop patc'es at'ig' fre*uencies w'ere t'ere were none at'ig' fre*uencies w'ere t'ere were none at

ower fre*uency of =0 ".ower fre*uency of =0 ".

&'is a(oids failure of 1& insulation due to t'e&'is a(oids failure of 1& insulation due to t'e

operation of Disconnectors) $As andoperation of Disconnectors) $As andBreakersBreakers


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,O;s for CTs,O;s for CTs

1'eck for any transit damage1'eck for any transit damage

1'eck t'e nitrogen pressure on t'e top c'amber1'eck t'e nitrogen pressure on t'e top c'amberbefore commissioningbefore commissioning

1'eck oil le(el in 1&1'eck oil le(el in 1&

Attend leakages on bus'ings immediately Attend leakages on bus'ings immediately

#+amine t'e porcelain for dirt deposits , clean#+amine t'e porcelain for dirt deposits , cleanperiodicallyperiodically

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,O;s for CTs,O;s for CTs8Cont9#:8Cont9#:

#nsure t'at t'e terminals of unloaded#nsure t'at t'e terminals of unloadedsecondary are s'ortedsecondary are s'orted

#art' t'e power factor terminal by eart'ing#art' t'e power factor terminal by eart'ing

postpost 1'eck t'at tank is eart'ed positi(ely and1'eck t'at tank is eart'ed positi(ely and

permanently.permanently.

4se t'e lifting lugs pro(ided on t'e bottom4se t'e lifting lugs pro(ided on t'e bottomtank for lifting t'e 1& by slingstank for lifting t'e 1& by slings

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Some specia! features ofSome specia! features of

Instrument TransformersInstrument Transformers

%n order to ensure leak proof gasket Joints)%n order to ensure leak proof gasket Joints)%nstrument &ransformers%nstrument &ransformers of B"#$ make areof B"#$ make are

subJectedsubJected to oilto oil pressurepressure test of 0.?test of 0.? kgkg== perpers*. cm ;0 psi

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#(olution of 19& 1oncept#(olution of 19& 1oncept

1apacitor Di(ider 1apacitor Di(ider

1apacitor Di(ider wit' &ransformer 1apacitor Di(ider wit' &ransformer

1apacitor Di(ider wit'1apacitor Di(ider wit' &uning Eeactor and&uning Eeactor and&ransformer &ransformer

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C$*$CITO( ,IVI,E(C$*$CITO( ,IVI,E(

9

92

1

12K

%$ %$

9 in 92

1

12

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C$*$CITO( ,IVI,E( 2IT.C$*$CITO( ,IVI,E( 2IT.

T($ C ' @ C &$

9 9 2

9 i ni n

I L

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C$*$CITO( ,IVI,E( 2IT.C$*$CITO( ,IVI,E( 2IT.T

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Schematic ,ia)ram of CVTSchematic ,ia)ram of CVTC'

C&'n

'a

'a;

/I

32 6 = > ? 0

'&

/I

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1apacitor 9oltage &ransformer 1apacitor 9oltage &ransformer

&'e 1apacitor 9oltage &ransformers&'e 1apacitor 9oltage &ransformers;19&s< are used for supplying (oltage;19&s< are used for supplying (oltagesignal to t'e measuring instruments andsignal to t'e measuring instruments and

protecti(e relaysprotecti(e relays

imultaneously t'e 19&s are used asimultaneously t'e 19&s are used ascoupling capacitors for ower $ine 1arriercoupling capacitors for ower $ine 1arrier

1ommunication ;$11

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Design features of B"#$ makeDesign features of B"#$ make

19&s19&s

tepless Designtepless Design

"ermetically ealed 4nit"ermetically ealed 4nit

imple and Eeliable 1ircuit and :.imple and Eeliable 1ircuit and :.

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D i f t f B"#$ kD i f t f B"#$ k

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Design features of B"#$ makeDesign features of B"#$ make19&s19&s

$11 erformance$11 erformance

8 "ig' fre*uency capacitance wit'in 0G to"ig' fre*uency capacitance wit'in 0G to

=0G of t'e rated (alue , "F resistance=0G of t'e rated (alue , "F resistance60 'ms at carrier fre*uencies.60 'ms at carrier fre*uencies.

8 tray capacitance C tray conductance oftray capacitance C tray conductance of

$9;"F< terminal of 1apacitor di(ider of$9;"F< terminal of 1apacitor di(ider of19& less t'an 300I0.0=M1n pF and =019& less t'an 300I0.0=M1n pF and =0micro iemens respecti(ely from 30 tomicro iemens respecti(ely from 30 to=00 k"=00 k"

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Design features of B"#$ make 19&sDesign features of B"#$ make 19&s

erro1resonance Stai!ityerro1resonance Stai!ity &'e 19& must be stable against Ferroresonant&'e 19& must be stable against Ferroresonantoscillations. &'is is assured by careful matc'ing ofoscillations. &'is is assured by careful matc'ing of'ig' impedance damping de(ice wit' t'e 19&'ig' impedance damping de(ice wit' t'e 19&parameters. &'e design pro(ides stability in allparameters. &'e design pro(ides stability in all

respects suc' as )respects suc' as )

udden energiing of t'e 19& w'en connectingudden energiing of t'e 19& w'en connectingin t'e 4"9 line or t'e busin t'e 4"9 line or t'e bus

ingle or t'ree pole 'ig' speed auto reclosingingle or t'ree pole 'ig' speed auto reclosing

Eemo(al of secondary s'ort circuit) andEemo(al of secondary s'ort circuit) and

udden c'anges of primary 9oltageudden c'anges of primary 9oltage

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erro1resonance Stai!ityerro1resonance Stai!ity

&'e 19& must not enter into ferroresonance in&'e 19& must not enter into ferroresonance in'unt EeactorNs presence t'at compensate t'e'unt EeactorNs presence t'at compensate t'eline capacitance partially.line capacitance partially.

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#limination of spark gap#limination of spark gap

8 &'e 19& is designed so t'at spark gap&'e 19& is designed so t'at spark gapor o(er (oltage protection de(ice acrossor o(er (oltage protection de(ice acrossintermediate capacitor is not neededintermediate capacitor is not needed

8 &'e impro(ed damping and spark gap&'e impro(ed damping and spark gap

elimination ensure e+cellent reliability ofelimination ensure e+cellent reliability of19& during operation19& during operation

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&ransient Eesponse&ransient Eesponse

8 eticulous design care) in particulareticulous design care) in particular

t'e 'ig' impedance ferroresonancet'e 'ig' impedance ferroresonancedamping de(ice presenting minimumdamping de(ice presenting minimumburden 'as ensured better transientburden 'as ensured better transientresponse for 19&s as compared toresponse for 19&s as compared to%7 3=>C%#1 > stipulations%7 3=>C%#1 > stipulations

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,esi)n features of -.E/ make CVTs,esi)n features of -.E/ make CVTs

1apacitor 9oltage Di(ider O&emperature compensated capacitor

dielectric system) results in low temperature

coefficient of capacitance.

O'ift in accuracy) due to steady as well as t'e

sudden temperature c'anges is minimum)

w'ic' leads to stable 19& accuracy.

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recommissioning 1'ecks 19&srecommissioning 1'ecks 19&s1'eck ratio of t'e 19& at low (oltage of about1'eck ratio of t'e 19& at low (oltage of about

230 to 2000 (olts to confirm soundness. &'e230 to 2000 (olts to confirm soundness. &'e19& ratio will tally wit' t'e marked (alue.19& ratio will tally wit' t'e marked (alue.

Kero secondary (oltageKero secondary (oltage indicates one of t'eindicates one of t'epossibilities of7 econdary s'orting ) or)possibilities of7 econdary s'orting ) or)

discontinuity in winding inside t'e transformer)discontinuity in winding inside t'e transformer)

or) Broken connection inside t'e capacitor.or) Broken connection inside t'e capacitor.

"ig'er (oltage on secondary"ig'er (oltage on secondary indicates partialindicates partialbreakdown on t'e 'ig' (oltage capacitorbreakdown on t'e 'ig' (oltage capacitor

$ower secondary (oltage$ower secondary (oltage is due to partialis due to partialfailure in t'e intermediate capacitor onefailure in t'e intermediate capacitor one

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DPs for 19&sDPs for 19&s

1'eck for any transit damage.1'eck for any transit damage. 1'eck t'e /itrogen pressure and 19& ratio at low1'eck t'e /itrogen pressure and 19& ratio at low

(oltage before commissioning.(oltage before commissioning. 1'eck oil le(el in # 4nit.1'eck oil le(el in # 4nit. Attend leakages on 19& immediately Attend leakages on 19& immediately #+amine t'e capacitor porcelain for dirt deposits#+amine t'e capacitor porcelain for dirt deposits

and clean periodically on deenergised and safelyand clean periodically on deenergised and safelyeart'ed 19&.eart'ed 19&.

1'eck t'at t'e tank is eart'ed at two points and1'eck t'at t'e tank is eart'ed at two points andlinks )2 , 3 are kept in position.links )2 , 3 are kept in position.

1'eck t'at t'e primary and secondary terminal bo+1'eck t'at t'e primary and secondary terminal bo+co(ers are in position and sealed properly.co(ers are in position and sealed properly.

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D/P&s for 19&sD/P&s for 19&s

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Do not connect Au+iliary 9&Cor inducti(e burdenDo not connect Au+iliary 9&Cor inducti(e burdenin 19& secondary w'ic' saturates before t'reein 19& secondary w'ic' saturates before t'reetimes t'e rated (oltagetimes t'e rated (oltage

Do not s'ort t'e 19& secondary terminals orDo not s'ort t'e 19& secondary terminals orprimary tapping coilsprimary tapping coils

Do not connect 19& secondary in closed deltaDo not connect 19& secondary in closed delta

pen delta connections s'ould not be eart'ed atpen delta connections s'ould not be eart'ed at

more t'an one point.more t'an one point.

Do not roll) donNt keep upside down) and donNtDo not roll) donNt keep upside down) and donNtlea(e t'e capacitor 'ousings in 'oriontallea(e t'e capacitor 'ousings in 'oriontalposition w'ic' is generally obser(ed at siteposition w'ic' is generally obser(ed at site

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-e from B"#$ wis' to t'ank

you) for gi(ing a patient 'earing

ct & cvt

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