Cdd
6
CDD Directional overcurrent and earth fault AREVA T&D Customer Benefits • Dust tight drawout case • Simple construction and easy accessibility. • High torque, ensuring consistent timing even under adverse conditions. 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 • High speed directional control. • Sensitive directional discrimination down to 1% rated voltage. • Identical time/current characteristics on all taps. • High torque, ensuring consistent timing even under adverse conditions. • Low overshoot. • Simple construction, easily accessible. • Comprehensive range of auxiliary and highset unit ratings. • Dust tight drawout case and tropicalised finish. • CDD 21 and CDD 31 relays are self powered. Hence no auxiliary supply is required. Application Directional phase or earth fault protection of ring mains, parallel transformers, feeders, parallel feeders etc., employing time grading principle. Description Type CDD relay comprises an induction disc overcurrent unit with wound shading coils and a directional high speed induction cup unit. The cup unit contact is wired across the shading coils so that no torque is exerted on the disc of the overcurrent unit until the cup unit contact closes. The induction disc unit is thus directionally controlled and it operates only when the current flows in the tripping direction. The IDMT relay has an auxiliary unit which is powered by a secondary winding on the electromagnet through a rectifier and as such, a separate auxiliary supply is notrequired. When the disc unit operates and closes its contact, the auxiliary element connected across the secondary winding on the electromagnet operates and one normally open contact of the auxiliary element reinforces the disc contact. Two other contacts of the auxiliary element are brought out to the terminals of the relay.(Refer figure 2) The directional unit is a high speed, low inertia four pole induction cup movement designed to give a high, steady and non-vibrating torque. Its current coil is connected in series with the operating coil of the induction disc unit. The directional unit is normally provided with voltage polarising coil. However, the earth fault relay directional unit can be provided with a current polarising coil, if required. Types CDD 21, CDD 23 and CDD 24 are directional versions of types CDG 11, CDG 13 and CDG 14 (plain inverse, very inverse and extremely inverse time current) relays respectively. Types CDG 11, CDG 13 and CDG 14 relays are described in relevant publications. A highset instantaneous overcurrent unit can be fitted in the same case to provide instantaneous protection under maximum short circuit conditions and to improve discrimination on time gradedprotective systems. This highset unit can be directionalised if required. Types CDD 21, 23 and 24 are single pole relays. Types CDD 31, 33 and 34 have instantaneous highset units, in addition to the directional IDMT. In types CDD 41, 43 and 44, the highset units are also directionalised. Of the above relays, only CDD 21 and CDD 31 relays are self-powered. PROTECTION
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Transcript of 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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