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IDMT Relay Setting for Transformer (Over Current / Earth Fault / Differential) ProtectionJignesh.parmar,www.electricalnotes.wordpress.com,jiguparmar@yahoo.com
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:Transformer Details:IDMT Over Current Relay Setting (50/51)IDMT Earth Fault Relay Setting (50N/51N)Differential Protection Relay
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3111
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Transformer Capacity25MVALT Side DetailsLT Side Details
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Primary Voltage (HT)66KVMain ProtectionMain Protection
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Secondary Voltage(LT)11KVOver Load Current :125%X IsEarth Fault Current :20%X In
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Rated Primary Current (Ip)218.7AmpOver Load Current :(In)1640AmpEarth Fault Current :(Inf)328AmpNormal Tap100%Normal Inverse (NI)
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Rated Secondary Current (Is)1312.2AmpRequired Over Current Relay Plug Setting3.2804954863.28 A X InRequired Earth Fault Relay Plug Setting0.65609909720.66 A X InVery Inverse (VI)
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Max.Earth Fault Current at HV Side (L-G)1100AmpActual Plug Setting of Over Current Relay (I>)125%1.25 A X InActual Plug Setting of Earth Fault Relay (Ie>)25%0.25 A X InLT SideExteremely Inverse (EI)
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Min.Earth Fault Current at HV Side (L-G)1000AmpPick Up Setting of Over Current Relay (PMS): (I>)6.25AmpPick Up Setting of Earth Fault Relay (PMS): (Ie>)1.25AmpFull Load Current1312.2AmpLong Inverse
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Max.Earth Fault Current at LV Side (LG)900AmpFault Current At CT Secondary Side45AmpFault Current At CT Secondary Side9AmpCurrent in Sec. Side of CT6.705Amp
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Min.Earth Fault Current at LV Side (L-G)800AmpPlug Setting Multiplier (PSM):7.2AmpPlug Setting Multiplier (PSM):7.2AmpHT Side
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Max.Earth Fault Current at Downstrem of TC (L-G)700AmpCurve Selection:Normal Inverse (NI)Curve Selection:Normal Inverse (NI)Full Load Current218.70Amp
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Min.Earth Fault Current at Downstrem of TC (L-G)600AmpTime Dial Setting of Over current Relay(TMS):0.1SecTime Dial Setting of Earth Fault Relay(TMS):0.1SecCurrent in Sec. Side of CT5.467Amp
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Max.Fault Current at HV Side (L-L)5000AmpTime of Operation of Relay3.476SecTime of Operation of Relay3.476SecSpil Over current in Relay-1.238Amp
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Min.Fault Current at HV Side (L-L)5500AmpActual Operaion Time of Relay: (t>)0.348SecActual Operaion Time of Relay: (te>)0.348SecPercentage Differntial Current-20.3%
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Max.Fault Current at LV Side (L-L)4500AmpBack Up Protection for Down StreamBack Up Protection for Down Stream
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Min.Fault Current at LV Side (L-L)4000AmpActual Plug Setting of Over Current Relay (I>>)150%1.5 A X InActual Plug Setting of Earth Fault Relay (Ie>>)25%0.25 A X InHighest Tap (+)10%
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Max.Fault Current at Downstrem Side of TC (L-L)3500Amp
Pick Up Setting of Over Current Relay (PMS): (I>>)
7.5Amp
Pick Up Setting of Over Current Relay (PMS): (Ie>>)
1.25AmpTransformation Primary Voltage at + 10%72.60KV
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Min.Fault Current at Downstrem Side of TC (L-L)3000AmpFault Current At CT Secondary Side30AmpFault Current At CT Secondary Side6AmpTransformation SecondaryVoltage at + 10%11KV
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CT for O/C & Earth Fault Protection:Plug Setting Multiplier (PSM):4AmpPlug Setting Multiplier (PSM):4.8AmpLT Side
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CT Ratio (LT Side)Curve Selection:Normal Inverse (NI)Curve Selection:Normal Inverse (NI)Full Load Current1312.2Amp
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Prim. Current (Amp)500Time Dial Setting of Over current Relay(TMS):0.1SecTime Dial Setting of Earth Fault Relay(TMS):0.1SecCurrent in Sec. Side of CT6.71Amp
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Sec. Current (Amp)5Time of Operation of Relay4.980SecTime of Operation of Relay4.393SecHT Side
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CT Ratio (HT Side)Actual Operaion Time of Relay: (t>>)0.498SecActual Operaion Time of Relay: (te>>)0.439SecFull Load Current198.8Amp
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Prim. Current (Amp)100Current in Sec. Side of CT4.97Amp
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Sec. Current (Amp)5Actual Plug Setting of Over Current Relay (I>>>)140%1.4 A X InActual Plug Setting of Earth Fault Relay (Ie>>>)25%0.25 A X InSpil Over current in Relay1.735Amp
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CT for Differential Protection:
Pick Up Setting of Over Current Relay (PMS): (I>>>)
7Amp
Pick Up Setting of Earth Fault Relay (PMS): (Ie>>>)
1.25AmpPercentage Differntial Current29.7%
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CT Ratio (LT Side)Fault Current At CT Secondary Side35AmpFault Current At CT Secondary Side7AmpHighest Tap (-)15%
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Prim. Current (Amp)1000Plug Setting Multiplier (PSM):5.000AmpPlug Setting Multiplier (PSM):5.600AmpTransformation Primary Voltage at - 15%56.10KV
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Sec. Current (Amp)5.11Curve Selection:Normal Inverse (NI)Curve Selection:Normal Inverse (NI)Transformation Secondary Voltage at - 15%11KV
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CT Ratio (HT Side)Time Dial Setting of Over current Relay(TMS):0.1SecTime Dial Setting of Earth Fault Relay(TMS):0.1SecLT Side
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Prim. Current (Amp)200Time of Operation of Relay4.280SecTime of Operation of Relay3.994SecFull Load Current1312.2Amp
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Sec. Current (Amp)5Actual Operaion Time of Relay: (t>>>)0.428SecActual Operaion Time of Relay: (te>>>)0.399SecCurrent in Sec. Side of CT6.71Amp
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HT Side
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HT Side DetailsHT Side DetailsFull Load Current257.2937636Amp
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:Results of IDMT Relay Settings:Over Load Current :125%X IpEarth Fault Current :20%X InCurrent in Sec. Side of CT6.43Amp
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IDMT Over Current Relay Setting (50/51)
Over Load Current :(In)273AmpEarth Fault Current :(Inf)55AmpSpil Over current in Relay-0.27Amp
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LV SideRequired Over Current Relay Plug Setting2.732.73 A X InRequired Earth Fault Relay Plug Setting0.550.55 A X InPercentage Differntial Current-4.2%
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Plug Setting of Over Current Relay (I>)
1.25 A X In
Actual Plug Setting of Over Current Relay (I>)128%1.28 A X InActual Plug Setting of Earth Fault Relay (Ie>)25%0.25 A X In
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Actual Operaion Time of Relay: (t>)0.348SecPick Up Setting of Over Current Relay (PMS): (I>)6.4AmpPick Up Setting of Over Current Relay (PMS): (Ie>)1.25Amp
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Plug Setting of Over Current Relay (I>>)1.5 A X InFault Current At CT Secondary Side250AmpFault Current At CT Secondary Side55Amp
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Actual Operaion Time of Relay: (t>>)0.498SecPlug Setting Multiplier (PSM):39.06AmpPlug Setting Multiplier (PSM):44.00Amp
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Plug Setting of Over Current Relay (I>>>)1.4 A X InCurve Selection:Normal Inverse (NI)Curve Selection:Normal Inverse (NI)
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Actual Operaion Time of Relay: (t>>>)0.428SecTime Dial Setting of Over current Relay(TMS):0.1SecTime Dial Setting of Earth Fault Relay(TMS):0.1Sec
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HV SideTime of Operation of Relay1.841SecTime of Operation of Relay1.781Sec
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Plug Setting of Over Current Relay (I>)
1.28 A X In
Actual Operaion Time of Relay: (t>)0.184SecActual Operaion Time of Relay: (te>)0.178Sec
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Actual Operaion Time of Relay: (t>)0.184SecBack Up Protection for Down StreamBack Up Protection for Down Stream
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Plug Setting of Over Current Relay (I>>)1.6 A X InActual Plug Setting of Over Current Relay (I>>)160%1.6 A X InActual Plug Setting of Earth Fault Relay (Ie>>)25%0.25 A X In
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Actual Operaion Time of Relay: (t>>)0.211Sec
Pick Up Setting of Over Current Relay (PMS): (I>>)
8Amp
Pick Up Setting of Over Current Relay (PMS): (Ie>>)
1.25Amp
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Plug Setting of Over Current Relay (I>>>)1.5 A X InFault Current At CT Secondary Side200AmpFault Current At CT Secondary Side40Amp
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Actual Operaion Time of Relay: (t>>>)0.199SecPlug Setting Multiplier (PSM):25.000AmpPlug Setting Multiplier (PSM):32.000Amp
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IDMT Earth Fault Relay Setting (50N/51N)
Curve Selection:Normal Inverse (NI)Curve Selection:Normal Inverse (NI)
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LV SideTime Dial Setting of Over current Relay(TMS):0.1SecTime Dial Setting of Over current Relay(TMS):0.1Sec
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Plug Setting of Earth Fault Relay (Ie>)
0.25 A X In
Time of Operation of Relay2.105Time of Operation of Relay1.951
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Actual Operaion Time of Relay: (te>)0.348Actual Operaion Time of Relay: (t>>)0.211SecActual Operaion Time of Relay: (te>>)0.195Sec
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Plug Setting of Earth Fault Relay (Ie>>)
0.25 A X In
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Actual Operaion Time of Relay: (te>>)0.439Actual Plug Setting of Over Current Relay (I>>>)150%1.5 A X InActual Plug Setting of Earth Fault Relay (Ie>>>)25%0.25 A X In
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Plug Setting of Earth Fault Relay (Ie>>>)
0.25 A X In
Pick Up Setting of Over Current Relay (PMS): (I>>>)
7.5Amp
Pick Up Setting of Earth Fault Relay (PMS): (Ie>>>)
1.25Amp
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Actual Operaion Time of Relay: (te>>>)0.399Fault Current At CT Secondary Side225AmpFault Current At CT Secondary Side45Amp
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HV SidePlug Setting Multiplier (PSM):30.000AmpPlug Setting Multiplier (PSM):36.000Amp
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Plug Setting of Earth Fault Relay (Ie>)
0.25 A X In
Curve Selection:Normal Inverse (NI)Curve Selection:Normal Inverse (NI)
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Actual Operaion Time of Relay: (te>)0.178SecTime Dial Setting of Over current Relay(TMS):0.1SecTime Dial Setting of Earth Fault Relay(TMS):0.1Sec
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Plug Setting of Earth Fault Relay (Ie>>)
0.25 A X In
Time of Operation of Relay1.989SecTime of Operation of Relay1.884Sec
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Actual Operaion Time of Relay: (te>>)0.195SecActual Operaion Time of Relay: (t>>>)0.199SecActual Operaion Time of Relay: (te>>>)0.188Sec
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Plug Setting of Earth Fault Relay (Ie>>>)
0.25 A X In
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Actual Operaion Time of Relay: (te>>>)0.188Sec
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