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Calculation of IDMT Over Current Relay Settings(50/51):Calculation of IDMT Earth Fault Relay Settings(50N/51N):Jignesh.Parmar www.electricalnotes.wordpress.com jiguparmar@yahoo.com
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Name of FeederName of Feeder
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Load Current: (IL)384AmpLoad Current: (IL)384Amp
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Min Fault Current ( Line-Line):11000AmpMin Fault Current ( Line-Ground):11000Amp
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Max Fault Current ( Line-Line):22000AmpMax Fault Current ( Line-Ground):22000Amp
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Relay TypeRelay TypeNormal Inverse (NI)
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Relay CodeRelay CodeVery Inverse (VI)
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Relay NoRelay NoExteremely Inverse (EI)
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CT Primary Current600AmpCT Primary Current600AmpLong Time Inverse
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CT Secondary Current1AmpCT Secondary Current1Amp
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Relay Error (%)7.5%Relay Error (%)7.5%
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CT Error (%)10.0%CT Error (%)10.0%
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Over shoot0.05SecOver shoot0.05Sec
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C.B Interrupting Time0.17SecC.B Interrupting Time0.17Sec
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Safety 0.33SecSafety 0.33Sec
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Total Grading Time0.58SecTotal Grading Time0.58Sec
Enter Data in White Background Cells
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Expected Operating Time of Relay0.271SecExpected Operating Time of Relay0.176Sec
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Over Current Relay Setting Earth Fault Relay Setting
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Low Over Current Setting: (I>)Low Earth Fault Setting: (Ie>)
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Over Load Current :125%X ILEarth Fault Current :20%X In
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Over Load Current :(In)480AmpEarth Fault Current96Amp
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Required Over Current Relay Plug Setting0.80.8 A X InRequired Earth Fault Relay Plug Setting0.20.2 A X In
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Actual Plug Setting of Over Current Relay0.800.8 A X InActual Plug Setting of Earth Fault Relay0.160.2 A X In
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Time Dial Setting of Over Current Relay (TMS)0.125SecTime Dial Setting of Earth Fault Relay (TMS)0.125Sec
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Curve Selection for RelayNormal Inverse (NI)Curve Selection for RelayNormal Inverse (NI)
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Pick Up Setting of Over Current Relay (PMS): (I>)0.8AmpPick Up Setting of Earth Fault Relay (PMS): (Ie>)0.16Amp
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Plug Setting Multiplier (PSM):22.92Plug Setting Multiplier (PSM):114.58
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Operation Time of Relay2.17SecOperation Time of Relay1.41Sec
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Actual Operating Time of Relay : (tI>)0.271SecActual Operating Time of Relay : (te>)0.18Sec
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Total Grading Time0.58SecTotal Grading Time0.58Sec
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Operating Time of Previous Up steam Relay0.85SecOperating Time of Previous Up steam Relay0.76Sec
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High Over Current Setting: (I>>)High Earth Fault Setting: (Ie>>)
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Actual Plug Setting of Relay2.502.5 A X InActual Plug Setting of Relay2.502.5 A X In
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Time Dial Setting of Over Load Relay (TMS)0.100SecTime Dial Setting of Over Load Relay (TMS)0.100Sec
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Curve Selection for RelayNormal Inverse (NI)Curve Selection for RelayNormal Inverse (NI)
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Pick UP Setting of Over Load Relay (PMS): (I>>)2.5Amp
Pick UP Setting of Earth Fault Relay (PMS): (Ie>>)
2.5Amp
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Plug Setting Multiplier (PSM):7.33Plug Setting Multiplier (PSM):7.33
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Time of Operation of Relay3.44SecTime of Operation of Relay3.44Sec
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Actual Operating Time of Relay : (tI>>)0.34SecActual Operating Time of Relay : (te>>)0.34Sec
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Total Grading Time0.58SecTotal Grading Time0.58Sec
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Operating Time of Previous Up steam Relay0.92SecOperating Time of Previous Up steam Relay0.92Sec
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Summary of Over Current Relay Setting:Summary of Earth Fault Relay Setting:
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Pick Up Setting of Over Current Relay (PMS): (I>)OK
Pick Up Setting of Over Current Relay (PMS): (I>)
OK
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Low Over Current Setting: (I>)0.8 A X InAmpLow Earth Fault Setting: (Ie>)0.2 A X InAmp
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Actual Operating Time of Relay(tI>)0.271SecActual Operating Time of Relay(te>)0.176Sec
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High Over Current Setting: (I>>)2.5 A X InAmpHigh Earth Fault Setting: (Ie>>)2.5 A X InAmp
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Actual Operating Time of Relay(tI>>)0.34SecActual Operating Time of Relay(te>>)0.34Sec
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