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SPECIFICATION Ho' DDS-80:2007

L.r cuRRFNr TUUI|!)FIUERS

-:-- FoR METEBINQ

Io. rQEWARD

0'l.llrisspecificationhasbeenpreparedbyDesigri&Standardsof{ice,PolterWirtq, Wnlll)4.

i

I lris specilication is inlended for the puipose of procurement of matcrial and

;;;;'il;iinctucJe the provision of contract'

llre specification is subiect to revision as and when required'

current transformers shall be tested itr accordance with lEc-185 and IEC-

60044'1 amended uPto date'

SCOPE

rerililrcfprn'rers'to be used for meteringI his spccification Describes LT Crrt - {. . - :: : -'

rated three phase ,",.C

;.;il;;^; in conjunction with' curcil rarsfiontreropet

energy meters 3* U*- Horlr {Rea{rg energy') melers'

PE. of current tiansformer has.. -t'een'lypc one namely W-OUNP y

:h'of whiih shatt ir;.vestarrdardizc:d in t*'o Oifo"tU ry of 2515'50/5 eac'

'

100% over current rated caPacnry-

i

\9

02

03

04

I

TI

17-

13

3?1

lype one namely t'\'lNIlCn'U TPF' of current ^transformer

has I een

standardized in ""t""-Cr"'*tt Elingi'?r^]9.0/5' 29?.1?:-100/5' 40ci5' 6(;0/5'

;i)0/5,'1oo.ts, eactr of t'tdtlt shall ha-ve 1'CI% over current'

l

Currelrl ffanslgrmers.

Arritrstrumentlranslormerinwhichthese.gond.?'Icufrent,irrntlrrrra|conditions of u=",

-ii suUitantiaff' ;piopo':lio.nai to the primary crirrent and

differs in phase 1,o]nilV tn i"gi"it"rictr is approximately'zero for an

iitpinpti"te direction of the connection' '

llaltctl l)rinrary-Cgr19:1t :

,rimary current on wi;rich tre perfor,mance of the transf: rmer??

is based,

I.

?3

24

11 a te d -Se co{dq-Ly_qqrrent.

-IlL'valrrr-'of seconcJary current onwhictr the performance of the liansformer

is based.

Current error (Ratio "rroi)

'lhe err'or which ttre transforiner introduce$ into the measurement of a cuireht

and which arises from the fact that the actual transformation ratio is not equal

to the raled transformation ratio. The current error expressed in percirnt is

given hry ttre formula.

Current error o/o = (Kn x ls-: lp) X100I

i

I

Whcre.Kn is lhe rated transtormaiion ratil lp is the actual primary curreni & lsis flowing under the ccnditions of

?55

is tne actual secondary current where lpInreasurernent.

NO [t:: fhis definition h stricily correct for sintrsoidal currents only

:l'h?se Dlqplaceugd

I t ne Oilt"r*nce in phase between tlre primary & secondary current Vectors the

direclion of the vectors being so chosen that the angle is zero for a perfect

.lransformer. The phase displacenent is said to be positive when thetsecondary current vector leads S.* pttryty current vector. lt is usually

expres5ed in minutes or centiradians-

26

2.7

2B

2.9

'As-ag$qy-Qla-r!t.

A clesignation assigned to the cutrent transformer lhe enors of which rett ;:in

wilhin ipecilied limits under prescribed conditions of use-

:

;l.lurrjenI

,'l'he irnpedance of the secondary circuit in O, & ,powgl faclor - The Burden is

tusually'expressed as the apparent power in volt amperes abscrbed at a

'spccified power factor and al the rated secondary current

lratqdlullleL-l he value of the burden on which the accuracy requirements of the

, specifications are based-

i

Baled-9-utP-ul

'lhe value of the apparent power (in volt ?mperes at a specified powe.r fuctor)'which the transforli"t l. ilttu"ded, to subply tq thg sqcondary circuit ;rl the

ratecJ secondary current and with':rated buiden:corlnected'to it-

1 0 Rated short-ti&e-1be$relsgrrgnt flx)

|.hennsvalueoftheprimarycurrentwhichatransformerwillwiihstanclorohe ser;oruJ without suffering h;;iui effects, Lhe secondary winding beittg

shorl circuiled'

? 1 1 llatcd l)yrramic-currell-( l-gy!)

i r tlia nrirn?rv cltrrent which a transformer willIjhe pcak value of ttre primary 9uLt€wittrorttbeingdamagedelectricityormechanicallybytheelcctrornaqnetic forcel]ir'* =u"ondary

winding being short ciriuited

withstand,resultinS,

7 |'.)I

Iiated instrument securitv currenl

lps .

E=lon

r*e

.IhevalueolthecrrrrentassignedbythemanufactureraStlrelowestprlmary

currenl (tps]"at orti"t-tnu rmi value o] itt* secondary current (lss) multiptied

bv ttre transformation ratio (Kn) does not *i"""d 0'9 times the value *f the

;l#"-;#i:'il;";r;ia,y uu'gun-u"ing equal to the E'-Tl'v bl':d91

rhis mey he express*rl by th* lsrfi$la'

** lss < 0.9-.lPs

2 "1?- Bslqd Lnsllr{lst*s€qurj1y"-cgIIs$

Atype.testmaybeperformedtlsirqfirn|onow-lngindirecttest.Witirtheprimary winding open-circu',g. * ieconOary 'wiiding

Energiz-ed al rated

rreq'ency nf a-suOstantia'y sil;;d;ita,gei.?ving ii't r.m's value equal t:

the seconc,ary timiting "*r. r#ffi;g ;;q'qpn iurrent (texe)' expres$e(i

ai a pierc;;il;;'';itn*irat o secondlry curent (lsn) multiplied bv tlir'

insirunrenr olllhr"Lil;C;;;u" tq';r to'or exc6ed the rared value ::r

tlre conrPosi[e of 10%'

lexclsn FS

x 100 >10

3 lftlrisre?-tlllot_**9:r-en-tshouldbecalledintoquestion.aconirrrllingmo?lsrirernont"sh"il--m-p*rror**I ffih' td-;irect test (seen annex'.')' the

reiLrlt of which is than rnandatory

? 1 3 I rrslrr-rme!l-t-89*I!!y-fuqntlE)

nt'security current ( I ps) to the rated primary

buirent (lpn) as e-xPressed by lheJormula

3i

R

L

I

I

I

l

!l

I

4_

4.1

42

4.3

44

4.s

KThygroscoptic-

DIMENSIONS

a

a

The dimensions shall be as per fig: I, ll & iil.

GENEBAL REQU|RMENTS

I he currenl transformers shall be single pole, single ratio, snd dry type.

err lype onc the general shape shall be as shown in Fig: l.

or typc lwo the general shape inatt be as shown in Fig: ll.

I he core shall be toroidal (ring) fdrm and it shall be rnade of high Gradesilicon steel or solne olher low loss steel of suitable grade;

The insr.ilafion used for secondary winding shall be able to withstand I-6eeffects'oFhealing an&mechahicai'stressei to which it may ne iuqecieu innorma! operalion and under.short circuit conditions and it shall be non-

4.6

4.7

4B

-lhe crrrent lransformers shall be protected againstdarnage by the Use ofhousinglbody of PO LYC AR BO NAT ElEquivatent niateria L:

jfhe current lransformer ratio shall be clqarty rnarked on the body.

f,he secondary winding shall termimte and fixed' permanently to lhesuilable terminals as shown in Fg lll- Tle terlninals shall be rigidly fixed totlrc body and shall be of chromelhi*d platedrbrass"

Note: A Transparenl tenninds cover shall be provided with propersealing arrangerneril- i

!

5.0

5'l

RATINGS

I

Qjrr1_e11jlallgs

[:or wound type ratirlgs as under have been standardized each of wlrlchshall have an exterdd range of 100% of the rated primary current.

Exten{gd ranqgPrimary Secondary

\^

lf,asic rating-sPrimary Secondary

?-5

50

50

100

10

10

.+"

Easic ratinqs*Primary SecondarY

100

The other ratings standardized are.as given under, eacn #,which shatl

have an extended range of 200%-i

;!

Extended ranqePrimary SecondarY

200 1,0

9

200

300

40()

600

8fi1

ltxto

5

5

5

5

5

5

400

600

800

1200I

1600

2000

10

1g

10

10

10

10

5-3 !zunur! n"rro output at the basic secondary c'rrent, i.e, 5 aryps shall be 5VA'

ra

t^

\|l

Thecurrentl.ransformershailbeabletopass.!Pto2oo%'orJneqrimalcurrent,' with secondary camected to ynity power factor butt'en

co*esponAing to inu t"t*O ouiput, continuously without any damag;t:'

5 4 1 lhernalraltjrg

: l"tr* ,rrrr"nt transfomEf drall be able td withstand wlthoqr.any damage i

current of up to 25li|nes the rated primary current. f,of g'perid of one

i second. ;

tt.4.2 Py:ramic rallng .. : ,_

The current transformer shall be able to wrtlptand.'wjthout any damage a

short time ovnamic ctment up to 2.5 times],ratdd.thermal durrent for a

5.4 lRated iofrtinupus thermal cunent'

period of one second'

5 5 Bslei-Jrrsgb$on levsl

l-he rated insulation level

FrequencY uot:tn:'*

s 6 l-e-ruPSfalge-risei

I

shall be 3 Kv {r.m.s} for

II

i

:

:

one minute Power

I

I

t

I

II

tr

The stardard accuracy class ofcurrenl r6$ngs shall be class 0.S.

6.2 Ttrc lirnils of error shall be as under:

The maximum temperature rise of the winding or that of the core Shall notexceed 50 deg. c when carrying a primary-current equal to 200% ratedcurrent, with the secondary connected [o a unity Power factor burc1en -borresponding to the rated output.

:

t,

@'

The value of the instrument security factor shall be less than 5 (see' CJef initions 2.13)

.l

t

all the current transformers of Differenl

l':

!

i

!

I

5,7

61

+ percentage current ( ratio)error at percentage ofrated current shown below.

10 20 100 2001.0 0 75 0,5 0.5

+ phase.displacemenl etpercentage of rated snownbelow in minutes

20 100 2il045' 30 30

:1060

7.0

71

TERMINAL MARKINGS

l'he marking of the terminal shall be as'shown in Fig 2 " s 1 " & " ii2', !,'rallbe marke'd on the secondary terminals whereas p1 & pz shall be m;ri-ked rncurrent transformer housing to indicate the primary winding polaritics.

I

All the current translormers shall carry at tea!t the following lnfoi-mation,which shall be marked, on the external rating'plate attached to the currenttransformer housing. All the Markings must,be indelible and distinct

Manufacturers name or trade markType designation'l'ire rated Primary and secondary currents, e.g, 100/SA-Rated frequency.Rated output and accuracy class and lhe extended current Ranlre(e g, 5VA, class 0.5, ext. 200%),ryspeciivety,

7.2 I'he terminals market'Pl' and'Si' shall have the same policy at tire s{r,neinstant.

/.3 .fhe marking shall be clear and indelible.

{],O RA ING PLATE

a.b.c.de.I

i

i

I

l

iI

f. Meter security factor n<5.

I

I

;'*,ii:;"x.tjtni:

v

i

10.1,1I

@r 1I. PACKING

I

(aJI

9-vef-V-ollage-lntqr turn Test ,

1

One test shall be selected from (a) or { b) below

with the secondary winding open circuited, a voltage at raied frequency

*r,orr 6u apptied fdr f minute tct the primary wind.ing. The value ot |!evgtfage shail be ,u"h ut to produee primaty current glrms value equal tqt

lhe extende,l ,ang" primary current or a value, which correspcllds to a

secondary voltage cf 3.5 Kv Peak, which ever be lower'

wth the primary winding open circuited a voltage at rated ft:quency

sha6 be apptied for 1 miiute to the ieconOary win?ing' The val re of the

,rott"g* shall be sucn as .to produce a secondary cuffent 9! rrns value

*qn "ito the extended fange secondary current or a value cf 3'St(v peak'

nrhich ever be the lower'

4I

i

(b)

I

It;pL* Qu-| (rr,tnr-rsoog ALAM)

l'nrcrl:.]:_?

fui

:_rr:t gacfr current.transformer shall 6e securely packed in an individual carton

t capable or wirnitanding the rigorous of tr-ansportation by Railway or truck

i

12 ENql=glgltRE-g

'.1 .t ' wlz)-#ell

I

I

ULIEFIN&

- t-:E&t(MOilAMMAD AKBAR)

DY. DIRECTOR (DAS)

' cHl{DESIG

|AS$AN Kl"lAN)NGINEERSTANDARNS)

10.6 Visual fXaminatjpn'l lte currenl transformers shall be examined visually for the defects As urrder:

Exarnination Defecti

1. Oonstruction Not of General shape shpwn in Fig: 1, ll & lll,Any component part missing or damagedRating label/sticker missing Terminal loose

Jh" marking of the terminal or tha{ on ilre ratrnglabel/sticker not conforming to clauses 7 & g. Ratio nolmarked on the body

2 Markings

3- Fn'dsh General workmanship poor, presence of rust on any part.

'lhe dimensions shall,be verified forconlormance to those given Fig, I. ll, lll

lO B Verificatio-n pf Bp-lgg tebelgldcr

[Jsc of a conductor for the Printrywi.nding ani then with direct current passinglhrouqh lhe secondary utinery. connect a lrigh voltage i.e, Voltn-rtter :rcros.slhe orrllet terminals of lhe sarne winding $o as to Get a small positirre defrsslio,of lhe pointer. Then hansfer the two voltmeter leads directty acror:s thelransformer to the alfiacent primary respectively corespondingl teads Thedirect current excitation b then broken, thereb! inducting a voltage in the p iinarywinding ( lnductive kft*) ttrtrich will cause a defleclion in the voltnreter. tf thep-ointer lfrng in tte same direction as before ( Positive ), thepolarii'7 is c lrrectlf lhe pdinter srirgs in the negative direclion, the polarity is incorrect

1 0 9 P-sw,er.-8rc-qgengr-Ie$ an Primarv Windinqr --J

I

10 10

For type one a test voltage of 3 Kv rms,. which shall be substantiallysinusoidal wave form and of any convenient frequency belv.,een zs &100l.lz shall be applied for one minute bel.ween the primdry conCr:ctor andearlh, the frame being connected to earth.

llqWg1-l:le-qUercV Test On $ecqndA i g

f ltc secondary winding insulation shall, withstanclrfor 1 minute a testvoltage of 3 Kv rms which shall be substlntialfy. sinusoidal waveform a:rd ofany convenient frequency between,25 & 100 i{2. The test voltage shall heapplied between terminal of the secondary win,Jing connectec lo.ietherand earth: the frame being connected to earth.

\^

r I .:;'

-,_ _-_1.::!:,.:-

I

91

,rE-$ls_ *,i

iTyp.e _-T_q_qt.q

,Tlre frlllowirrg typre tests shall. be performed on one current transfornrer *f eaclrir"liflercnl type or raling offered. :

T_,,^^ A----, il I ype Accuracy test., b Tenrperature rise test.

. i c lnstrunrent security current test.I d. Srrort time current tebt for c'f with fixed primary winding.s 2 Bqqtir:elesls

I i y:T,ffiiliilttt;,.,',c- Routine accuracy test.d. Verification of teiminal markings

" e fower freguency test on primary windingr f. powe.r frequency test on ,u"ond"ry winJing. g. Over voltage inter turn test.

IO TEST ilETHODS-

lo I *gg&r,uqu'!-9.r.The test shalt be conducted to prore cornpliance wiilr clause 6. -fests

slrall tre,made fcrr each curretrt value givLn m oaus! e.il; al zsa/a and 100% of ratedib,r<lnn -r vvaqrr\

| 0.2 B_qrrtrjte.A_cqqla.qyJe$

T.he rorltitte accLlracy tesl striafl be conductecl lor only one value of cur.:nt ai-r1burden The current shdl be ffre vatue of rated extended range or}-1e cilrrr.1rrtransformer and the burden shafl be the rated burden.

10 3 fe. tnp_efglUre-Bjse_tegl

'A tdst shall be made to provide compljance with clause s.6. The currer,,transfornter shall be deemed to have atiained a steady t**pui"ioiu i,+.:en lrerate of tenrperature rise does not exceed.one deg. ceniigraol6l;;";t0 4 UqttulrentS.ecuritv Cunent.

-. -r -'-*.

rhe test shall be corducted lo prove that,llhe.in'slrument,security current doesnot exceed the rated varue. The test may be made with lil h;h:; il; *;;;llr.rofilr"rrring

lhe primary current and the other med.uiing in; =s*".,,noary

10.5 $bojlTime Current Test :

Short time circuit raling af 12.5 KA for one5015 A shall be performed in accordanceamende{up to date ' ,'

se,c-ond,.for CT, ratio 25lS A anrlwith IEC-1c5 and IEC-60O44.

.t

Gl

b

v