cdd

CDDDirectional overcurrent and earth fault

AREVA T&D

Customer Benefits

• Dusttightdrawout case• Simpleconstruction andeasyaccessibility.• Hightorque,ensuring consistenttimingeven underadverseconditions.

CDD relays are intended for directional phase or earthfault protection of ring mains, parallel transformers, transformer feeders, parallel feeders etc., employing the time grading principle. It is a self-powered relay without any requirement of auxillary supply.

Features • Highspeeddirectionalcontrol. • Sensitivedirectionaldiscriminationdown to1%ratedvoltage. • Identicaltime/currentcharacteristicson alltaps. • Hightorque,ensuringconsistenttiming evenunderadverseconditions. • Lowovershoot. • Simpleconstruction,easilyaccessible. • Comprehensiverangeofauxiliaryand highsetunitratings. • Dusttightdrawoutcaseandtropicalised finish. • CDD21andCDD31relaysareself powered.Hencenoauxiliarysupply isrequired.

ApplicationDirectionalphaseorearthfaultprotectionofringmains, parallel transformers, feeders, parallelfeedersetc.,employingtimegradingprinciple.

DescriptionType CDD relay comprises an induction discovercurrentunitwithwoundshadingcoilsandadirectional high speed induction cup unit. Thecupunitcontactiswiredacrosstheshadingcoilssothatnotorque isexertedonthediscof theovercurrentunituntilthecupunitcontactcloses.The induction disc unit is thus directionallycontrolledanditoperatesonlywhenthecurrentflowsinthetrippingdirection.

The IDMT relay has an auxiliary unit whichis powered by a secondary winding on theelectromagnet through a rectifier and as such,a separate auxiliary supply is notrequired.When the disc unit operates and closes itscontact,theauxiliaryelementconnectedacrossthe secondary winding on the electromagnetoperatesandonenormallyopencontactoftheauxiliary element reinforces the disc contact.Twoothercontactsoftheauxiliaryelementarebroughtout to the terminalsof the relay.(Referfigure2)

Thedirectionalunit isahighspeed, lowinertiafourpoleinductioncupmovementdesignedtogive a high, steady and non-vibrating torque.Its current coil is connected in series with theoperating coil of the induction disc unit. Thedirectionalunitisnormallyprovidedwithvoltagepolarising coil. However, the earth fault relaydirectionalunit canbeprovidedwithacurrentpolarisingcoil,ifrequired.

Types CDD 21, CDD 23 and CDD 24 aredirectional versions of types CDG 11, CDG13 and CDG 14 (plain inverse, very inverseand extremely inverse time current) relaysrespectively.TypesCDG11,CDG13andCDG14relaysaredescribedinrelevantpublications.

Ahighsetinstantaneousovercurrentunitcanbefittedinthesamecasetoprovideinstantaneousprotection under maximum short circuitconditions and to improve discrimination ontime gradedprotective systems. This highsetunitcanbedirectionalisedifrequired.

TypesCDD21,23and24aresinglepolerelays.Types CDD 31, 33 and 34 have instantaneoushighsetunits,inadditiontothedirectionalIDMT.In typesCDD41,43and44, thehighsetunitsarealsodirectionalised.

Oftheaboverelays,onlyCDD21andCDD31relaysareself-powered.

PROTECTION

Technical dataSettings

O/Celements IDMT:50%-200% Highset:250%-2000%

E/Felement IDMT:10%-40%or20%-80% Highset:100%-800%

Directional unit coil ratings

Currentcoil:0.2, 1.0, 2.0 and 5 amps. Rating selected ascloseaspossibletocentretapcurrentsettingofinductiondiscunit.

Relay

CDD21with3VAdiscunit(selfpowered)

BuRden at min. setting

2.25VA

BuRden at max. setting

CDD21with1VAdiscunit

CDD23

CDD24

1.0VA

1.0VA

0.6VA

7.5VA

5.3VA

6.0VA

6.0VA

Burdens

Currentcoil:3VAor1VAnominalfordiscunit.3VAdiscunitshouldbeusedwhereCTsareadequatelyrated.

Currentpolarisingcoil:1VAatratedcurrent.Voltagepolarisingcoil:9VAor4.5Wat110Vac.3VAor1.5Wat63.5Vac.Currentandvoltagetransformerrequirementswillbegivenonrequest.

CuRRent Coil tap

times CuRRent setting

1 2 3 4 5

4.5 3.7 3.2 2.7 2.6

6

2.4

7

2.2

Withstands20timesmaximumcurrentfor3s.Voltagepolarisingcoilcontinuouslyratedfor200Vac.

CDD21relaywithdrawnfromcase

Thermal ratings

Maximumcontinuouscurrentratingslimitedbydiscunitcoilrating.

2>3

Voltagepolarisingcoil:63.5or110Vac,50Hz.

Currentpolarisingcoil:1A or 5A for earthfault relay. For currentpolarisation, a suitable current transformer isrequiredintheneutraltoearthconnectionofapowertransformer.

Maximum torque angle

(Characteristicangle)

Phasefault:

45º or 30º current leading. Quadratureconnection normally used with current coilconnectedinonephaseandvoltagecoilacrossothertwophases.

Earthfault:

14º current lagging for resistance earthedsystems.45ºor60ºcurrentlaggingforsolidlyearthed systems. A 3 phase 5 limb VT withopendeltatertiaryor3singlephaseVTswithtertiary winding used for supply to polarisingcoil. MTA for current polarised relay is 0º ascurrentincurrentcoilandpolarisingcoilareinphase.

Operating time

Less than 0.010 second for directional unitwhich is very small compared with overalloperatingtimeofCDDrelay.

Accuracy

Errorclassindex: • E7.5asperBS142 • 7.5asperIS3231

Frequency error

Timingerror lessthan8%for2Hzfrequencyvariations. Time grading unaffected by suchsmall error, since all relays are similarlyaffected.

Temperature error

For 10 times setting current at ambienttemperature between +45ºC and -5ºC,percentage timingerrorsareasfollows: • CDD21:3secondsrelay,-3%and+4% • CDD21:1.3secondsrelay,-4% and+4% • CDD23:+1%and-1% • CDD24:-3%and+5%

Directional discrimination

Down to about 1% normal voltage with 1 to15timescoilratedcurrent.Downtoabout3%normalvoltagewith0.4to40timescoilratedcurrent.Directionalcharacteristicsof45ºMTACDDrelayshowninFigure1.

Output contacts

These are provided via an auxiliary unit with2 pairs of self, hand or combined self andhandresetcontacts,whichreinforcesthedisccontactandahandresetoperationindicatorisalsoprovided.

Coil rating

Voltage operated auxiliary unit 30, 110 or220Vdcwithnominalburdenof3wattsupto110Vand6W for220V.Othercoil ratingsareavailableonrequest.

Contact ratings

Disccontact:Makeandcarryfor0.5s2500VAwithmaximaof10A/660Vac/dc.

Auxiliaryunitcontact:Makeandcarryfor0.5s5700VAwithmaximaof30A/660Vac/dc.

Insulation

Therelaymeets therequirementsof IS3231/IEC255-5SeriesC-2KVfor1minute.

Case

1½ D vertical case suitable for flush orprojection mounting and finished eggshellblack and tropicalised. Suitable trip isolatingswitchandCTshortingswitchesprovidedonthecradleassembly/case.

Figure1:Directionalcharacteristicsofa45°MTACDDrelay

Figure2:Typical external and internalconnections for type CDD 21voltage polarised directionalearthfault relay with shuntreinforcingunit

4>5

Relay Case size

Heightmm

maximum oveRall dimensions appRoximate gRoss

weight Kg.Widthmm Depth*mm

CDD21,23,24CDD31,33,34CDD31,33,34

1½D 362 170 203 12.0

*Add76mmformaximumlengthofterminalstuds,alternatively,29mmforterminalscrews.Theapproximategrossweightsgivenaboveareinclusiveofcartons,mountingappendagesandterminaldetails.TherelayscomplyfullywiththerequirementsofIS3231andaresuitableforuseinnormaltropicalenvironments.

Information required with order

1. Typeofrelay(CDD21,23or24,CDD 31,33or34,CDD41,43or44)and systemfrequency.

2. Currenttransformersecondaryrating.

3. Currentsettingrange.

4. Voltagetransformersecondaryrating(for voltagepolarisedrelays).

5. Currenttransformersecondaryrating(for currentpolarisedearthfaultrelays).

6. Maximumtorqueangle.

7. Characteristic(0-3.0sor0-1.3sat10times currentsetting.forCDD21relaysonly).

8. Selfpoweredornot.forCDD21/31relays only.9. Auxiliaryvoltage(forshuntauxiliaryunits).

10.Operationindicatorinscriptionifrequired.

11.Auxiliarycontacts.handorselfreset.

12.Currentsettingrangeofhighsetunit,if required.

13.Typeofmounting.flushorprojection.

Dimensions and weights

AREVA T&D

Pallavaram Works19/1, G.S.T. Road,Pallavaram, Chennai - 600 043Tel: 91-44-2264 8000

Fax: 91-44-2264 0040

AREVA T&D Worldwide Contact Centre:http://www.areva-td.com/contactcentre/Tel.: +44 (0) 1785 250 070

www.areva-td.com

Our policy is one of continuous development. Accordingly thedesignofourproductsmaychangeatanytime.Whilsteveryeffortismadetoproduceuptodateliterature.Thisbrochureshouldonlybe regardedasaguideand is intended for informationpurposesonly. Itscontentsdonotconstituteanoffer forsaleoradviseontheapplicationofanyproductreferredtoinit.Wecannotbeheldresponsibleforanyrelianceonanydecisionstakenonitscontentswithoutspecificadvice.

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