VTX

PROTECTION

VTX Supervision Relay

 VTX relay is used for the continuous supervision of CT secondary  wiring and connections of busbar protection schemes. A built in delay of 3 seconds is provided to avoid unwanted alarm during external/internal faults.The relay after operation will short the CT bus wires.

Features • • • • •

Description

Consis Consisten tenta taccu ccura racy cy.. Reli Reliab abil ilit ity y. Low Lowbu burd rden en.. Reduced Reducedmain maintenan tenance. ce. Immunitytotransientsand Immunitytotransientsandsurges, surges, withs withstan tands ds5K 5KV Vimp impuls ulsev evolt oltage agete test. st.

Application Thisrelayisusedforthecontinuoussupervision of CT seco second ndar ary y wiri wiring ng and and conn connec ecti tion ons s of busba busbar r prote protecti ction on schem schemes. es. Each Each prote protecte cted d zoneofthebusbarinstallationisequippedwith analarmrelay,shouldtheCTsecondarywiring developafaultwhileloadcurrentisflowing,an alarmisgivenafteratimedelayof3seconds. The delay delay isgiven isgiven toprevent toprevent analarm inthe caseofgenuinebusbarfaultwhenthebusbar protectionisrequiredtooperateandisolatethe faultysection.Further,duetoitssensitivesetting requir requiremen ement, t, the relay relay maybe unstableunder unstableunder heavy heavy externalfaultconditio externalfaultconditions,the ns,the time delay delay allowsthefaulttobecleared allowsthefaulttobeclearedbytheappr bytheappropriate opriate protectionthuspreven protectionthuspreventingunwantedal tingunwantedalarms. arms. Therearetwotypes: Therearetwotypes:Singlephas SinglephaseVTX11and eVTX11and threephaseVTX31.ThefollowingTablegives thefunctionaldetailsofboththetypes.

The The rela relay y cons consis ists ts of thre three e stag stages es, , pick pick-u -up p voltagecontrolstage,timingstageandoutput stage.TheblockdiagramofVTX11isshownin Figure1.ThethreephaseversionVTX31 Figure1.ThethreephaseversionVTX31issame issame asVTX 11except 11except that that a threephas threephase e recti rectifie fier r bridgeisusedtoconvertacinputquantitiesto dcsignal. Underhealthyconditionsoftheprotectedcircuit thereisnoacinputtotherelayandtheauxiliarydc supplycausestransistorT1toconduct,shorting outthecapacitorinthetimingcircuit.Whena voltageappear voltageappearsacross sacross theac input input terminals terminals, , the recti rectifie fied d dc output output ofthe bridge bridge tends tends to biasoffthetransistorT1,incasetheacinputis higherthanthevoltagesetting.WithT1off,the timingcircuitcapacitorbeginstochargeupfrom thestabiliseddcsupply.Afteratimedelayof3 seconds, seconds, thecapacitorvoltagereach thecapacitorvoltagereachesa esa prepredeterminedvalueandtriggersthetransistorT2 whichinturn whichinturn switches switcheson on theoutputtransis theoutputtransistor tor T3.Theinternalelectromechanicalauxiliaryunit, being being in theload circuitof circuitof transisto transistor r T3 picks picks up and and init initia iate tes s alar alarm m and and othe other r func functi tion ons. s. Cont Contin inuo uous us adju adjust stme ment nt of the the rela relay y volt voltag age e settin setting g is provi provided ded by a potent potentiom iomete eter r in the bridge bridge output output circuit. circuit. Protecti Protective ve devices devices have beenincludedinthecircuitrytopreventdamage dueto spikesin spikesin theinput voltagesor voltagesor reverse reverse connectionofthedcauxiliarysupply.

Customer Benefits • High stability on external faults • Tuned to rated frequency • 25ms operating time at 5 times current setting

Singlephaseusedwithearth faultschemes

Threephaseusedwithphase andearthfaultschemes

Will Will dete detect ct open open circ circui uit t of currenttransformers.

Will Will dete detect ct open open circ circui uit t of currenttransformers Willdetectbrokenorcrossed CTpilots

AREVA T&D

Technical data Voltage setting 2to14Vcontinuouslyadjustableat50Hz.

Thermal rating • Singlephaserelay:  600Vacrmsat50Hzbetweenthe inputterminalscontinuouslyonany setting.

 VTXrelay withdrawnfromcase

• Threephaserelay:  300Vacrmsat50Hzbetweenany phaseandneutraloftheinputterminals continuouslyonanysetting.Therelay willalsowithstand2kVacrms50Hz forthreesecondsonanysetting.

Auxiliary supply Therelaycanbesuppliedsuitableforoperation at30V,110Vand220Vdc.Forvoltagesabove 30V, an external dropping resistor is used. Satisfactory operation is maintained over a rangeof75%-120%.

Accuracy •

Atratedauxiliarysupplyandrated frequency,therelayhasanaccuracyof ±5%ofthesettingvalueonanysetting.

•

Operatingtemperaturerange-5ºCto +50ºC.

Operating time Nominal3seconds.

Figure1: BlockdiagramforVTX11relay

2>3

Burden Continuousburdenimposedondcauxiliarysupply isasshowninthetablebelow: 30V

110V

220V

relAy unoperAted (W)

1.0

3.5

7.0

relAy operAted (W)

1.7

4.0

7.7

 AuxiliAry voltAge

 Approximateacburdenperphaseforbothtypesof relaysonanysettingisasfollows:  Applied voltAge Burden (vA)

10V

300V

1414V

0.002

4.2

86

Contacts Twopairsofnormallyopen,selfresetcontactsare providedontheoutputattractedarmatureunit. Contact ratings MAke And cArry  continuously 

MAke And cArry  for 0.5 second

BreAk 

 AC

1250VAwith maximaof5A and660V

7500VAwith maximaof 30Aand660V

1250VAwith maximaof5A and660V

DC

1250W with maximaof5A and660V

7500Wwith maximaof 30Aand660V

100W(resisitive) 50W(inductive) withmaximaof 5Aand660V

Operation indicator  A hand reset mechanical operation indicator is fitted as standard on the output attracted armatureunit.

Insulation The relay willwithstand2.5kV rms50 Hzfor 1secondbetweenalllivepartsandearth,and betweenallcircuitsnotintendedtobeconnected together.Itwillalsowithstand1.25kVrms50Hz for1sacrossopencontacts.

Impulse withstand level The relay will withstand 5 kV impulse voltage testinaccordancewithIECrecommendations.

High frequency disturbance Therelaymeetsthe IECtest recommendation for the high frequency disturbance test. The relay accuracy is unaffected by repetitive 1 MHz bursts having an initial peak of 1.0 KV super-imposedacrossinputcircuitsand2.5KV betweenindependentcircuitsandearth,witha timedelayof3to6microseconds,withtherelay energised.

Case Singlephaseandthreephaserelaysaresupplied insize 1 drawout(1D) cases suitable forflush mountingand arefinished eggshell black and tropicalised. The drawout feature considerably simplifiesmaintenanceandpermitstestingtobe carriedouteasilyandquickly.Acradlemounted isolatingswitchisprovidedwhichautomatically isolatesthetripcircuitwhenthecradleassembly is withdrawn from the case for maintenance. This prevents any inadvertent tripping of the circuitbreaker. A filter breather is fitted which equalises the pressure inside and outside the casewithoutadmittingdust.

Information required with order 1.Typeofrelay 2.Auxiliarydcvoltage

Figure2: Typical connection diagram of  VTX 31 relay in 3 phase bus zone protection scheme for phaseandearthfaults.

4>5

Dimensions and weights

MAxiMuM overAll diMensions relAy

 VTX31

cAse size

height MM

Width MM

depth* MM

1D vert.

233

170

203

 ApproxiMAte gross Weight kg

4.5

* Add76mmformaximumlengthofterminalstuds,alternatively,29mmforterminalscrews. Theapproximategrossweightsgivenaboveisinclusiveofcartons,mountingappendages andterminaldetails. TherelayscomplyfullywiththerequirementsofIS3231andaresuitableforuseinnormal tropicalenvironments.

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