erection and maintenance of transformers

8/14/2019 Erection and Maintenance of Transformers

1/82

ERECTION,OPERATION

AND MAINTENANCE OF

DISTRIBUTION AND

POWER TRANSFORMERS


2/82

RECEIPT OF TRANSFORMER AT SITE

(1)Dispatched with Core & Windings fitted in the

Tank and filled with Nitrogen upto 0.15kgc!.s" or

filled with #nsulating $il a%oe Windings.

(') #f filled with Nitrogen check Nitrogen ressure and

if less than 0.' kgc!.s" replenish it upto

0.15kgc!.s".

(*) +ll other parts such as Conserator Tank,ushings

(-&/)adiators+ccessoriesrotectie deises

are dispatched in separate packages.


3/82

() 2eep the following Tools & 3aterials read4

6teel 6lings of arious capacities-4draulic

/ifting 7acks Wooden 6leepers Wooden

acking ieces + 3o%ile Crane etc.

(5) ,efore Co!!encing 8rection Nitrogen !ust %e

slowl4 released and the tank flushed with Dr4

$94gen or filled with #nsulating $il slowl4 to

aoid contact of winding with +t!ospheric +ir.


4/82

Precautions to be taken Long Storage of the Transformer is not

recommended.

Store Oil Drums properly

Assembly should commence from Bottom

Core !indings should be filled "ith Oil as soon

as #itrogen is e$pelled.

Choose a Dry Day "hen "eather is clear

Care to be taken so as to not to allo" any foreign

ob%ect falling into the Transformer

Blanking Plates should be remo&ed "hen "e are

ready for assembly.


5/82

Blanking Plates should also be stored safely after

"ork is completed.

The Person "orking "ith Tools used inside

Transformer must tie it by cotton tape

#o coins'pens'"atches etc should be used by the

persons "orking on the Transformer

(askets must be tightened properly ie #ot too much

or too less

#e" (askets must be used for Bushings )adiators'etc

*nsure tightness of all the connections inside and

proper Locking


6/82

Transformer Oil must be pumped from the Drums to

the Storage Tank through Purifier

Lea&e about +,mm oil at the bottom of each drum.-tmay be impure.

Pumping in Oil must be through the Drain &al&e. Also

Draining. Lea&e one Opening at the Top Open to

release *ntry Air.

Before Commencing Oil filling and purification'Clean

the top of oil drums'flush hoses'Oil Tank'and the

ilter also. /se (asket Paste "hen fi$ing them

Once the 0oint is detached' use fresh (askets


7/82

(asket Paste shall be applied uniformly before

pressing onto a metal surface.

All the Bushings must be thoroughly cleanedespecially the Bottom Portion before assembly.

Bushing Shields must be fitted to the Bushing before

assembly. Storage of (asket is &ery important.#o rolling'folding

Oil Pockets for OT- !T- must be filled "ith Oil

before fitting the Sensing Bulbs

or Transformers rated belo" 11k& 2acuuming to be

done at belo" 34,mm5g


8/82

or Transformers abo&e 11k& 2acuuming to be

done at 678mm of 5g

*9uali:er pipe connections must be connected

bet"een the ;ain Tank and OLTC to a&oid

Buckling of OLTC

The Bursting 5ead of *$plosion 2ent to be

remo&ed and a Blanking Plate fi$ed before

&acuuming the Transformer.

The )e9uired &acuuming shall be for t"o

hours. )eplace 2ent *$plosion 5ead

Oil may be in%ected through the Bottom Drain

2al&e into the Transformer.#o )ubber 5oses


9/82

5ot Oil Circulation to be done to e$pel moisture

from the insulation at 1,


10/82

i$ the Arcing 5orns for the Bushings ?for 11k& and

abo&e@and ad%ust

Connect the Transformer Body earth

)elease any Trapped Air from the Bushings' TopCo&er etc

Connect the 5eating Coils of the !T- to BCT

Terminals.


11/82

Precautions to be taken !en orkin"

in a #i$e Substation %

Do not "ork too close to another Li&e e9uipment Before "orking Take a Permit. All sources of po"er

must be disconnected

A safety earth to be pro&ided "here&er necessary

The Area of "ork should be surrounded "ith a

Safety )ibbon and all the staff clearly educated

Trained and 9ualified persons must carry out

inspection and enforce safety


12/82

All the Testing de&ices must be handled by ualified

persons A Safety Sargent should be posted at the "ork site

"ho should deenergi:e if needed

-f it is necessary to "ork inside the Tank' Dry Air

must be allo"ed as the Oil is pumped out .

Dry Air supply must be slo"ly allo"ed inside from

the Bottom and allo"ed to go out from the top by

keeping one Blanking Plate Open should a person

"ork inside


13/82

Another Person should al"ays stay outside

"atching the person inside

*lectrical Tools should be used "ith plug pins only

!arning Boards should be *$hibited

Before energi:ing the *9uipment ensure that all the

"orking personnel ha&e come out and all the *arths

pro&ided for safe "orking are remo&ed.


14/82

ERECTION,O&M OF ' P!ase (()*+''*

DISTRIBUTION TRANSFORMERS

)ead the ;anufacturers -nstructions carefully.

The Transformer should be commissioned only after

completing all the assembly and Pre


15/82

;obile Crane or other appro&ed de&ices should be

used.

or Loading and /nloading the Transformer the T"oLifting Lugs pro&ided on the sides of the Transformer

should only be used.

Ade9uate care must be taken "hen shifting the Tr

to site from Storage ard

The Transformer is dispatched in complete shape "ith

the Tank' core !indings' Conser&ator' 2ent' 52

L2 Bushings' assembled. 2isual -nspection must be

done before erection to detect any damages' leakage

of oil'cracks.


16/82

Pre commissioning Site Tests such as ;egger

Test' )atio Test' *$citation Current' !inding

Continuity'Oil sample Testing for Dielectric and

Acidity to be done.

Oil is inflammable.Take care not to bring naked

flame or light such as during "elding near the

Transformer

ibrous cleaning material should not be used./se cloth


17/82

Equipment for Erection, Testing andEquipment for Erection, Testing and

CommissioningCommissioning

AC 2oltmeters ?,,,, &olts or +,,,&olts@

*lectric Oil Pump = 5and Pump

Spanners Single=Double *dged' )ing' complete Set

Scre" Dri&ers' assorted si:es' Tester

Enife' TailorFs scissors

;S Bolts #uts' !ashers ?plain and spring@


18/82

Cotton cloth for cleaning

Paint Brush "ith Paint as re9uired

Oil Sampling Bottle and Testing Eit Transformer should be erected on a Le&el

oundation

The oundation must be properly designed. Sufficient clearances bet"een phases and (round

shooed be maintained

or -ndoor -nstallation' good &entilation muste$ist

*$amine Standard ittings like )ating Plate' Oil

(auge'Lifting Lugs' Conser&ator'2ent' etc


19/82

Bi ;etallic Connectors to be used in 52 L2

connections Transformer *arthing Terminals must be earthed.

?#ote C)(O core is connected to clamping frame

"hich is connected to the Transformer Tank@

Lifting Lugs pro&ided on the Tank Co&er is meant

for Lifting Core !indings. #or for Lifting Tank

Check for Drain &al&e' Sampling 2al&e' Oil Le&el

(auge' Breather' 2ent' Bottom Channel ?;ounting@'

Corrugated ins for )adiator.


20/82

Pre Co--issionin" TestsPre Co--issionin" Tests atio Testatio Test

This can be done by using a Turns )atio Tester or byusing T"o 2olt meters.

Applying a 3 phase >7 &olts supply on 52 side'

measure the 2oltages on the L2 side bet"een phases and also

bet"een phase and (round on e&ery Tap.

Check Continuity of "inding at e&ery tap.

*nsure that the &oltages as measured is as per the

)ating plate and "ithin the Tolerance permitted.

Alternati&ely ' the Turns )atio can be directly

checked at &arious Taps by )atio Tester


21/82

-nsulation )esistance-nsulation )esistance

The -) &alues should be checked "ith a 7,,

2olts megger for L2 "inding and a >,,,=+,,,&olts megger for 52 "inding

-) &alues bet"een Phase to (round on all 52

and L& "indings must be taken . Also bet"een52 L2 . The Temperature at the time of test

must be noted

The ;egger Leads must be continuous


22/82

The 52 L2 Bushings must be thoroughly

cleaned.

The Safe -) 2alues as per CB-P >>k& and 33k&

are 2oltage.. ;inimum safe -) in ;ega Ohms at a

Temperature of

G C 3, , 7, 1,

>>k& ,, +,, >,, 7,

33k& 7,, +7, >+7 17

Temp >.84 3.87 6.47 >7.47Correction


23/82

Precautions Precautions

Any -) 2alue taken must be )educed to +, deg C.

All the &alues must be taken "ith the same

instrument'temperature recorded "ith the same meter.

NoteNotethat for e&ery >, GC rise in Temperature the -)

&alue gets 5al&ed.

T+N D8/T+T+N D8/T+(Dielectric Dissipation :actor) on(Dielectric Dissipation :actor) onthe Windingsthe Windings

This Test indicates the Dielectric Loss actor.

The Po"er actor of the -nsulation is directly related

to the moisture absorbed by the "inding.

The higher the Po"er actor'the greater is the moisture

absorption. The ideal "ould be ,.,>H >, to the po"er

of


24/82

3agneti;ing Current 3agneti;ing Current

A 3 phase >7 2olts supply is applied to the

Primary and the ;agneti:ing current measured in

all the phases.

These &alues must be e9ual and confirm to the

;anufacturers Test Certificates.


25/82

$il Tests$il Tests

The BD2 of -nsulating Oil must "ithstand 3, k& perminute "hen Tested "ith a Eit ha&ing >+mm spheres

and a +.7 mm (ap

The same "ill hold good in respect of OLTC oil forPo"er Transformers.

Oil samples from Top and Bottom ha&e to be collected

for this Test.


26/82


27/82

After all the Tests as abo&e are satisfactory

Allo" a settling time of *ight hours

)elease Air from all the pockets

*nergi:e the Transformer "ith L2 uses in the

Distribution Bo$ remo&ed

Obser&e for any abnormal 5um or Sound

-f OE' measure 2oltage bet"een phases and

bet"een phase to (round

After a fe" hours' take out the Transformer' check

and rectify any abnormality and put it back into

operation


28/82

MAINTENANCE OF TRANSFORMERS

3aintain a register indicating all the reco!!issioning

Test esults.

+n4 !aintenance should %e done after de=energisation

of Transfor!er and 8arthing

h4sical inspection !ust %e done periodicall4 for an4$il /eakages /oose - & / & 8arth Connections

Clean the ,od4 ,ushings etc

During $er hauls the core and winding !ust %e

lifted windings inspected for displace!ent core foran4 looseness Tie ods cla!ps %olts and nuts for

tightness Ducts for an4 %lockage due to sludge and

re!ed4.


29/82

Check the /oad in +!peres on / side egularl4

Check /T oltages in all the phases

Check $il leel./eakages.

Check for tightness of -/Connections once in

si9 !onths.

Test the $il for Dielectric 6trength and +cidit4 once

in a 4ear.

$erhaul the Transfor!er atleast once in :ie>ears.

ERECTION O&M OF 'P ''+(()*ERECTION O&M OF 'P ''+(()*


30/82

ERECTION,O&M OF 'P,''+(()*ERECTION,O&M OF 'P,''+(()*

'.(/-$a,/.0-$a TRANSFORMERs'.(/-$a,/.0-$a TRANSFORMERs

)ead the -nstruction ;anual Carefully.

)ead the complete set of Dra"ings .

*nergi:e only after completing all the assembly

"ork'conducting all the Pre Commissioning Checks

and satisfactory pre commissioning Tests.

The )ele&ant -ndian standards are

-S +,+1 ?P>@' ?P+@' ?P3@' ?P@' ?P7@ onPo"er Transformer (eneral'Temp )ise'Dielectric

Tests' Terminal marking Tapings' Bushings

Clearances


31/82

Small capacity Transformers' after tests are

dispatched filled "ith Oil.!here the Conser&ator

and )adiators are of detachable type' Oil is filled

upto >,mm belo" Top Co&er.

/se Lifting Lugs pro&ided on the Top of the

Transformer on either side. Do not use the Lugs

pro&ided on t he Top Co&er. These are meant for

Lifting Core and !indings

/se Suitable ;obile Crane or appro&ed Lifting

De&ices for unloading=Loading

Packages containing Bushings Accessories

must be carefully handled


32/82

-n Lifting the Complete Transformers use such Lugs

to maintain balance and a&oid Tilting

Before /nloading the Transformers recei&ed fromthe actory' *$amine the parts for any missing'

damaged itemsI

Before commissioning' conduct 2isual Checks'

;egger the !indings'Do the )atio Test' Check

!inding Continuity'*$cite "ith Lo" 2oltage'

Conduct BD2 of Oil

Do not store for Longer periods.All Blanking plates

etc must be preser&ed


33/82

A properly designed oundation must be ready.

Oil Soak Pits are recommended.

*asy access around the Transformer.

*nsure Proper Clearance to Li&e Parts.

Cardon the !ork place "ith Safety )ibbon and

Danger Boards.

-ndoor -nstallations must be "ell &entillated.

Oil is inflammable.Take care "hen "elding nearby.

A&oid assembly' as far as possible on a moist day.

Those ha&ing access to the interior of the Transformer


34/82

Those ha&ing access to the interior of the Transformer

must empty their pockets.

!orkmen should tie the spanners they use' to their

hands' "ith Strings?Cotton@ Clean e&ery part "ith Oil or "ith #on fluffy cloth

for "iping

The Transformer oil can be circulated to get aTemperature abo&e ambient before accessing

interiors.

Transformer should be erected on a Le&el

oundation Oil ilteration to be Stopped !hen BD2 is

,E&=mt' !C


35/82

Tools Testing *9uipment )e9uired

Oil Test Eit

)atio ;eter ? T"o AC 2olt ;eters@

;obile Crane

2acuum (auge

;egger';otor Operated'>.,k&=+.7E&

5ydraulic 0acks'!ooden Sleepers= Packing "ood'spanners'tools.

Stream Line ilter

Slings' Shackles Chain Pulley Blocks=Tirfor

Tarpaline')opes'Cleaning rags etc


36/82

Pre Commissioning Tests

)atio Test

Polarity Test )esistance of "indings "ith Eel"in Bridge

-nsulation )esistance

;agneti:ing Current Oil Tests BD2=Acidity

*rection' assembly must bear the safety clearances

"hen "orking in Li&e Stations

Settings of all Current and 2oltage Operated )elays

and Testing

Operation of Alarms Tripping

All 5 d L2 ti t b ti ht


37/82

All 5& and L2 connections must be tight

*nsure Proper #eutral and Body *arthing

)elease Air from all Air )elease Pockets *nsure all )adiator 2al&es are Open

*nsure Drain 2al&es'Sample 2al&es'Top &al&es in

closed condition

Thermometer Pockets are filled "ith Oil

Oil Le&el is as re9uired

Arcing 5orns and (aps set.

!T- CT connected to Compensating 5eater.

Allo" a settling Time of + hours

) l th Ai f ll th P k t i


38/82

)elease the Air from all the Pockets again

*nergi:e the Transformer from 52.

#ote for any abnormal 5um= sound Check the L2 2oltages

Build up the 2oltage in Steps and )ecord

Transformer should be s"itched off again after + hrs

#ote any abnormal Temperature=&ibration= hum=

beha&iour.)ectify.

*nergise and Load the Transformer.

All the details to be recorded and informed to the

;anufacturer.

Check points for Large Transformers


39/82

Check points for Large Transformers

Eeep a fire fighting e9uipment )eady

!elding "orks must bear ire Safety

#o smoking near the Transformer=ilter

*arth all Control Cabinets'and;Bs

*nsure that the Tank has no pressure "hen BlankingPlate is being opened

)emo&e all loose parts on the Top co&er

asten tools to "rist. *mpty Pockets. /tmost care at "ork site

All components to be "ell cleaned.

;inimum *$posure of Core !inding

Any ob%ect dropped inside despite all precautions


40/82

Any ob%ect dropped inside despite all precautions

must be brought out.

Assemble Turrets in )ight places

Calibrate OT- !T-

Check Oil Le&els in Bushings

Settings of OT- !T-' Alarm=Trip

*arth )esistance of Transformer *arth

5and operation of OLTC in all Taps

Limit S"itches Operation of OLTC Step By Step Operation of OLTC

Local=)emote Operation of OLTC

Tap Position -ndicator

f l f h


41/82

Out of Step )elay of Tap cahnger

Off Circuit Tap Changer -nter Lock

Analyse any (as Collected in Buch )elay

Check -nter Trip operation

Trip ree Operation of 52 L2 CBs.

Check Alarms =Trips as belo"

Bucholt:' !T- 'OT-' Oil lo"'!ater lo"'

Differential Pressure ?Lo" Cooling@'an fail'P)

2al&e 'Diffl )elay'O=C )elay'*= )elay')* )elay.

Color of (as Due to Decomposition of


42/82

Color of (as Due to Decomposition of

!hite Paper Cloth

ello" !ood

(rey -ron

Black *lectric arc in Oil

Clear Air

!hen (as Passed throF 7J Ag #o3 sol

!hite Precipitate turning Bro"n. Oil Decomposition

!hen (as passed thro "eak Ammonia solution' if the

curdled precipitate turns to Dark Bro"n' indicates

Paper'"ood'cotton decomposition.

2acuum iltration of Oil should be done separately


43/82

2acuum iltration of Oil should be done separately

at 7,7ppm !C

2AC//; T)*AT;*#T

k& *&acuate5old Standing Time

?>7 >+5rs >+5rs

upto+, +5rs 45rs@ +, 315rs >+,5rs

No 8lectrical Test er!itted in acuu!

Don1ts 2or Poer Trans2or-ersDon1ts 2or Poer Trans2or-ers


44/82

Don ts 2or Poer Trans2or-ers.Don ts 2or Poer Trans2or-ers.

>.DonFt *nergise "ithout -n&estigation if it Trips

+.DonFt )e *nergise "ithout analysis of (as ifBucholt: )elay Acts

3.DonFt )e *nergise "ithout conducting all Pre

Commissioning Tests.DonFt 5andle Off Ckt Tap changer "hen the

Transformer is in ser&ice

7.DonFt *nergise the Transformer unless the Off CktTC is Locked

1.DonFt Lea&e Tertiary Terminals un


45/82

6.DonFt allo" OT-=!T- to e$ceed 17 deg C.ilter Temp

beyond 6,deg C.

4.DonFt Parallel Transformers unless conditions are

satisfied

8.DonFt /se Lo" Capacity Lifting 0acks

>,. DonFt ;o&e the Transformers "ith Bushings fitted

>>.O&er Load Transformer ?limits as per -S 11,,@

>+.Change !T-=OT- settings fe9uently

>3.Lea&e the )ed Pointer?;a$@ behind the Black

Pointer?-nstant@


46/82

>.Allo" Loose Connections

>7.;eddle "ith Protection Circuits

>1.Allo" Conser&ator Oil Le&el fall belo" >= le&el

>6.Allo" Oil Le&el in Bushings fall .Top up

immediately

>4.Allo" shalling Bo$ and Control Cabinetsunlocked.

>8.S"itch off 5eater in ;B off.

+,.Allo" Dirt Deposits on Bushings

+>.Allo" any /n


47/82

++.Lea&e Ladders /n


48/82

D$A6 :$ $W8 T+N6:$386 D$A6 :$ $W8 T+N6:$386

>.Check thouroughly "hen an Alarm =Trip occurs

+.Check Air Cell in Conser&ator3.Attend Lakages of Oil in Bushings -mmediately

.Clean Petty Coats of Bushings occassionally

7.Check BD2 !C of Oil in ;ain tank and BD2 for

OLTC

1.Check Oil Seal in Breather'top up if re9d

6.Check Oil for Acdity

4.Tighten -nspection co&er Bolts #uts /niformly"hen re9d

8.Clean )elay Alarm Contacts'their operation'accuracy

etc


49/82

>,.Periodically check Protection Circuits

>>.Pointers of all the gauges for free mo&ement

>+.Clean the Oil Conser&ator thoroughly before *rection

>3.Check Bucholt: )elay Operation

>.Check Painting and touch up if necessary

>7.Check !T-=OT- Oil Pockets and replenish Oil if need

be

>1.)elease Air through 2ent of Di&ertor before *nergising

>6.Check Oil Le&el in Di&ertor

>4.Check (ear Bo$ Oil Le&el'Top up

>8.)eplace "orn out OLTC contacts as re9uired


50/82

+,.Check all Bearings and Lubricate

+>.Eeep the *9ualising Pipe 2al&e bet"een the Tank

OLTC if pro&ided' open during 2acuuming and Oilfilling.

++.Connect a #+ Cylinder and keep the &al&e open'

maintain a positi&e pressre through the Automatic ?or

;anual@ regulator+3.ill the Transformer "ith Oil at the *arliest.

+ .Check Door Seals of ;arshalling Bo$ and )eplace

+7. Check "hether the ;ain Tank can "ithstand 2acuum

and if so the Safe Limit.?or *52 class >.,, Torr@

NoteNote adiators and Conserator Tanks cannotadiators and Conserator Tanks cannot

withstand acuu!withstand acuu!

MAINTENANCE SCEDU#ES


51/82

MAINTENANCE SCEDU#ES(For Power Transformers)

Hourly :

!inding Temperature' Oil Temperature' AmbientTemperature

Load in Amps ?;in=;a$@'2oltages?;in=;a$@

Daily :

Oil Le&el in Conser&ator'OLTC'Bushings'Oil Leakages

Mon!ly :

Breather functioning'Silica gel'Oil seal'Cleanliness of

Bushings'Loose Connections?5ot Spots@

"uarerly :


52/82

Cleanliness of Bushings'Oil Leakages'BD2 and !C of Oil

unctioning of Cooler ans ' Oil Pumps

Check OLTC Operation


53/82

Bushing Connectors for Tightness

Test Bucholt: )elay by Air -n%ection

Test Pressure )elief Trip Tan Delta for Bushings and !inding

Ma3or O$er au4Ma3or O$er au4

($nce in B to 10 >ears)($nce in B to 10 >ears)

Detailed e9a!ination of the windingCore $il,ushingsrotectie Deices6elector& Diertor

6witches etc.

Permissible BD2 !C


54/82

Belo" 6+.7k& K ,k&=mt' +7ppm

6+.7 to >7k& K 7,k&=mt' +,ppm

>7 abo&e K 1,k&=mt'>7ppm

?The (ap in Testing Eit to be +'7mm@

-) &alues at 3,deg C for Po"er DistributionTransformers

33=>>k& >>k& =,2

52 to *arth +7,; +,,;L2 to *arth +,,; >,,;

52 to L2 +7,; +,,;

Sin"4e P!ase A-or5!ous Meta4


55/82

Sin"4e P!ase A-or5!ous Meta4

Trans2or-er

Suitable for Direct Pole ;ounting

Plinth ;ounting

Temperature )ise ?Abo&e Ambient@

7 deg C by !inding

, deg C by Oil

)ating

>>k&=+,2'.7J M'67k&?Peak@ B-L'copper

Core

Shell Type' made of Amorphous ;etal ?-ronah Grain has to + oh# #

Grain Boundary has + to the %ower of + The Resistane of the Inter Granular 8ayer

dereases at a threshold (alue

Disharge ta"es %lae and nor#ali5ed The Resistane is :on68inear.

There are thre ty%es of Regions/


74/82

9) Brea" Down stage

9') A% Return; E +++& %er $# $ube

So#e I#%ortant 7ara#eters;

9) $O3 ; :or#al 3oltage/s? rt of '

9)M$O3 ; Ma= sys C3/s?.rt.of ' Rated C3 F Ma= sys "( G44

G44 9Ground 4ault 4ator)F

+.1 for Solidly earthed syste# .+ for In effeti(ely >arthed syste#

8& Disharges; 2"& to +"&.

7ressure Relief Dia%hrag# is %ro(ided as


75/82

an >=haust 3ent to safe guard e?ui%#ents

8as designed on 7ollution 8e(els ;

8ight.,##

Mediu#+##

!ea(y..2## 3.!ea(y..'##

Other $onditions;

bient ; H2+$ to 6+$&ltitude ; &bo(e +++#ts

8oation ; $orrosi(e / 7olluted /S#o"e

$he#ial / $onta#ination

&bnor#al 4re?ueny ;


76/82

-1!< or E ,!arth Jua"e

3ibrations

!igh @ind Iing

!ealth Monitoring ;

9) $he" Surge $ounter Rading regularly 9) $he" 8ea"age $urrents

9') $he" >=haust 3ents

Curren Transformers:

The 7ri#ary winding is generally a Bar


77/82

The 7ri#ary winding is generally a Bar.

It ould onsist of two or #ore turns to sa(e o%%er of the

seondary winding

There is no a%%reiable (oltage dro% in the 7ri#ary.

& !ea(y urrent ould flow through the 7ri#ary at a !igh

3oltage.

The urrent in the 7ri#ary is not de%endant on the 8oad

on the seondary.

& nu#ber of seondary windings 9alled oresRing

Ty%e) are %laed around the 7ri#ary.

The $lassifiation ould be for #etering%rotetion et The Iron $ore #ust be of 8ow 8oss 8ow Relutane

ty%e #ust ha(e 8ow 4lu= Density 9about +++ lines /s?

#). MAM>T&8 9:i64e &lloy) is used as $ore.

The Ratio hanging ould be on 7ri#ary or Seondary.


78/82

Generally a $urrent Transfor#er in the

>!3 l i h ti ll l d d i


79/82

>!3 lass is her#etially sealedand is

Maintenane 4ree 9Internal)

I#%ortant ; The Seondary @inding shouldnot be left o%en or loose.Dangerously !igh

3oltages will a%%ear.

$8>&R&:$>S ; 9##) (oltge 4or e?ui%#ent %h6%h s%aing in

rating %h6%h %h6> Isol Sw 9&!)

"( -,+ '+ ,+ *+

''"( *+ ,+ 0,+ +

'"( 0++ ++ -+ '+2+

$learanes in Strung Bus 9##)


80/82

C3 Rating S%ae between ondutors

+ -2++

' ',++

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