calculation for the value of stabilizing resistor ref setting
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1.Calculation For The Value of Stabilizing Resistor_1000kVA
Calculation for the Value of Stabilizing Resistor & Relay SettingEnter the values on cells highlighted in white,Result will be displayed in cells highlighted in Green & general datas in Blue
The CT requirements are class X with a knee point voltage in excess of twice the setting voltage.
Setting:The setting volatge may be determined by:
VS = IF/n [Rct + 2RL + Ra ]VS = Setting VoltageIS = Setting CurrentIF = Fault level in CT Primaryn = CT Ratio
Rct = Resistance of CT at operating temperatureRL = Lead resistance at operating temperatureRa = Additional resistance due to relay,contact/connection resistance etc at operating temperature
The Full CT requirement is therefore : Class X, ratio N,CT resistance Rct and knee point voltage > 2 x Vs
Dated:3/12/2011
Transformer DetailsTRF Capacity = 1000 kVATRF Primary = 11000 Volts
TRF Secondary = 400 VoltsTRF Impedance = 5 %
CT Primary(n) = 2000 AmpsCT Secondary = 1 Amps
n = 2000CT Secondary wiring Length = 30 Meters Neutral CT traveling distance
CT Secondary wiring size = 2.5 Sq.mmResistance of conductor = 7.41 Ohms / KM Refer the chart
CT resistance(RCT) = 8 Ohms CT Manufacturer to adviceCT magnitization current(Im) = 64 mA CT Manufacturer to advice
Fault level in CT Primary:IF = TRF Capacity x 1000 Example: IF=1600 x 1000 / 415 x 1.732 x 0.06 = 37100 Amps
TRF Secondary x 1.732 x ImpIF = 28868 Amps
Dated:3/12/2011
1.Calculation For The Value of Stabilizing Resistor_1000kVA
Lead resistance:RL = CT Secondary wiring Length x Resistance of conductor per meterRL = 0.22 Ohms Example: RL=20 x 7.41/1000 = 0.15 Ohms
Additional Resistance:Ra is usually ignored,but may have the value 0.01ohms
Ra = 0.01 OhmsVS = IF/n [Rct + 2RL + Ra ] Example: VS=37000/2500 [8 + 2(0.15) + 0.01] = 123 VoltsVS = 122 Volt
CT Knee Point voltage must be in excess of 2 x VS:
VKn = 244 Volts Example: Vkn=2 x 123 = 246 Volt
Required Loop Resistance Value:RS = VS / ISIS = 40 %IS = 0.4 Amps Example: IS=0.2 x 1(CT Secondary Amps) = 0.2A
Dated:3/12/2011
IS = 0.4 Amps Example: IS=0.2 x 1(CT Secondary Amps) = 0.2AVS = 122 Volts RS=123 / 0.2 = 615 OhmsRS = 305 Ohms
With the MREF relay the relay burden is less than 0.005VA and may therefore be neglectedRstab = 305 Ohms Stabilizing Resistor Value
Note:Under Fault Condition this resistor must pass
Value = 14.43 Amps Example: 37000 / (2500/1) = 14.8A
Peak Voltages:Under Fault conditions the peak voltage ignoring saturation of the C.T given by
VP = IF/n [Rct + 2RL + Ra + Rstab + Rr ] Rr = Relay resistance can be neglected= 4524 Volts Example: VP=37100/2500 [8 + 2(0.15) +0 .01 + 615] = 9250 Volt
VP = 4.524 KV
Dated:3/12/2011
1.Calculation For The Value of Stabilizing Resistor_1000kVA
Peak Voltage including saturation of the CT given by Vpk Value must be below approximately 3KV
Vpk = 2 √ 2 Vkn [ Vp - Vkn ] Example: Vpk=2 √ 2 246 [ 9250 - 246 ] = 4209 Volt= 2890 Volt
Vpk = 2.89 KV
In Case the value exceed 3KV,we must adjust the setting current and re-caulculate as below:If the VPK value was less than 3KV please fill the same setting current value so as to attain the P.O.C value.
RS = VS / IS Example: IS=0.4 x 1 = 0.4AIS = Setting Current ( May be taken in % ) RS=123 / 0.4 = 307.5 OhmsIS = 20 % Enter the value until VPK falls below 3KVIS = 0.2 Amps
VS = 122 VoltsRS = 610 Ohms
Rstab = 610 Ohms Stabilizing Resistor ValueVP = IF/n [Rct + 2RL + Ra + Rstab + Rr ] Rr = Relay resistance can be neglected
8927 V lt
Dated:3/12/2011
= 8927 VoltVP = 8.927 KV
Vpk = 2 √ 2 Vkn [ Vp - Vkn ]= 4117 Volt
Vpk = 4.12 KV
Effective setting [ Primary operating Current ] 20 %Setting CurrentP.O.C = n [N x Im + Inr + Is]
N = The number of connected CTsIm = The magnitization current for a single CT at setting VoltageIs = Setting current
Inr = Non Linear resistor current at setting VoltageInr = [(Vs)
/ (MI)]4
Inr = 0 Amps Inr Value is Zero since Non-Linear Resistor not used.P.O.C = 912 Amps Example: POC = 2500 [(4 x 0.013) + 0 + 0.4] = 1130Amps
% of Transformer rating = 45.6 %As per ESI 48-3 standard,the fault current setting shall be between 10% to 60% of the rated current of the winding.
Dated:3/12/2011
1.Calculation For The Value of Stabilizing Resistor_1000kVA
Limiting Peak VoltageIf it is not possible to limit the peak voltage,by careful selection of setting current,a voltage dependent Non-Linear resistor should be used.A Non-Linear Resistor Must be used with 40 % setting
Vp = MV [ IF / n ]0.25
MV = Coefficient Value Refer the chartMV = 900 Example: Vp=450[3700/2500]0.25 = 883Volt
IF = 28868 Ampsn = 2000 Amps
Vp = 1754 Volt
Inr = [(Vs) / (MI)]4
Vs = 122 VoltMI = Coefficient Value
= 900Inr = 0.0003 Amps Example: Inr =[123/450]4 =0.0056Amps
Dated:3/12/2011
P.O.C = 1312.6 Amps Example: POC = 2500 [(4 x 0.013) + 0.0056 + 0.2] = 644Amps% of Transformer rating = 65.63 %
As per ESI 48-3 standard,the fault current setting shall be between 10% to 60% of the rated current of the winding.
Dated:3/12/2011
1.Calculation For The Value of Stabilizing Resistor_1000kVA
Dated:3/12/2011Dated:3/12/2011
Calculation for the Value of Stabilizing Resistor & Relay SettingEnter the values on cells highlighted in white,Result will be displayed in cells highlighted in Green & general datas in Blue
The CT requirements are class X with a knee point voltage in excess of twice the setting voltage.
Setting:The setting volatge may be determined by:
VS = IF/n [Rct + 2RL + Ra ]VS = Setting VoltageIS = Setting CurrentIF = Fault level in CT Primaryn = CT Ratio
Rct = Resistance of CT at operating temperatureRL = Lead resistance at operating temperatureRa = Additional resistance due to relay,contact/connection resistance etc at operating temperature
The Full CT requirement is therefore : Class X, ratio N,CT resistance Rct and knee point voltage > 2 x Vs
Transformer DetailsTRF Capacity = 2000 kVATRF Primary = 11000 Volts
TRF Secondary = 400 VoltsTRF Impedance = 6.3 %
CT Primary(n) = 4000 AmpsCT Secondary = 1 Amps
n = 4000CT Secondary wiring Length = 30 Meters Neutral CT traveling distance
CT Secondary wiring size = 2.5 Sq.mmResistance of conductor = 7.41 Ohms / KM Refer the chart
CT resistance(RCT) = 17 Ohms CT Manufacturer to adviceCT magnitization current(Im) = 64 mA CT Manufacturer to advice
Fault level in CT Primary:IF = TRF Capacity x 1000 Example: IF=1600 x 1000 / 415 x 1.732 x 0.06 = 37100 Amps
TRF Secondary x 1.732 x ImpIF = 45823 Amps
Lead resistance:RL = CT Secondary wiring Length x Resistance of conductor per meterRL = 0.22 Ohms Example: RL=20 x 7.41/1000 = 0.15 Ohms
Additional Resistance:Ra is usually ignored,but may have the value 0.01ohms
Ra = 0.01 OhmsVS = IF/n [Rct + 2RL + Ra ] Example: VS=37000/2500 [8 + 2(0.15) + 0.01] = 123 VoltsVS = 200 Volt
CT Knee Point voltage must be in excess of 2 x VS:
VKn = 400 Volts Example: Vkn=2 x 123 = 246 Volt
Required Loop Resistance Value:RS = VS / ISIS = 20 %IS = 0.2 Amps Example: IS=0.2 x 1(CT Secondary Amps) = 0.2AIS = 0.2 Amps Example: IS=0.2 x 1(CT Secondary Amps) = 0.2A
VS = 200 Volts RS=123 / 0.2 = 615 OhmsRS = 1000 Ohms
With the MREF relay the relay burden is less than 0.005VA and may therefore be neglectedRstab = 1000 Ohms Stabilizing Resistor Value
Note:Under Fault Condition this resistor must pass
Value = 11.46 Amps Example: 37000 / (2500/1) = 14.8A
Peak Voltages:Under Fault conditions the peak voltage ignoring saturation of the C.T given by
VP = IF/n [Rct + 2RL + Ra + Rstab + Rr ] Rr = Relay resistance can be neglected= 11656 Volts Example: VP=37100/2500 [8 + 2(0.15) +0 .01 + 615] = 9250 Volt
VP = 11.656 KV
Peak Voltage including saturation of the CT given by Vpk Value must be below approximately 3KV
Vpk = 2 √ 2 Vkn [ Vp - Vkn ] Example: Vpk=2 √ 2 246 [ 9250 - 246 ] = 4209 Volt= 6002 Volt
Vpk = 6 KV
In Case the value exceed 3KV,we must adjust the setting current and re-caulculate as below:If the VPK value was less than 3KV please fill the same setting current value so as to attain the P.O.C value.
RS = VS / IS Example: IS=0.4 x 1 = 0.4AIS = Setting Current ( May be taken in % ) RS=123 / 0.4 = 307.5 OhmsIS = 20 % Enter the value until VPK falls below 3KVIS = 0.2 Amps
VS = 200 VoltsRS = 1000 Ohms
Rstab = 1000 Ohms Stabilizing Resistor ValueVP = IF/n [Rct + 2RL + Ra + Rstab + Rr ] Rr = Relay resistance can be neglected
11656 V lt= 11656 VoltVP = 11.656 KV
Vpk = 2 √ 2 Vkn [ Vp - Vkn ]= 6002 Volt
Vpk = 6 KV
Effective setting [ Primary operating Current ] 20 %Setting CurrentP.O.C = n [N x Im + Inr + Is]
N = The number of connected CTsIm = The magnitization current for a single CT at setting VoltageIs = Setting current
Inr = Non Linear resistor current at setting VoltageInr = [(Vs)
/ (MI)]4
Inr = 0 Amps Inr Value is Zero since Non-Linear Resistor not used.P.O.C = 1824 Amps Example: POC = 2500 [(4 x 0.013) + 0 + 0.4] = 1130Amps
% of Transformer rating = 45.6 %As per ESI 48-3 standard,the fault current setting shall be between 10% to 60% of the rated current of the winding.
Limiting Peak VoltageIf it is not possible to limit the peak voltage,by careful selection of setting current,a voltage dependent Non-Linear resistor should be used.A Non-Linear Resistor Must be used with 20 % setting
Vp = MV [ IF / n ]0.25
MV = Coefficient Value Refer the chartMV = 900 Example: Vp=450[3700/2500]0.25 = 883Volt
IF = 45823 Ampsn = 4000 Amps
Vp = 1656 Volt
Inr = [(Vs) / (MI)]4
Vs = 200 VoltMI = Coefficient Value
= 900Inr = 0.0024 Amps Example: Inr =[123/450]4 =0.0056Amps
P.O.C = 1833.6 Amps Example: POC = 2500 [(4 x 0.013) + 0.0056 + 0.2] = 644Amps% of Transformer rating = 45.84 %
As per ESI 48-3 standard,the fault current setting shall be between 10% to 60% of the rated current of the winding.
Calculation for the Value of Stabilizing Resistor & Relay SettingEnter the values on cells highlighted in white,Result will be displayed in cells highlighted in Green & general datas in Blue
The CT requirements are class X with a knee point voltage in excess of twice the setting voltage.
Setting:The setting volatge may be determined by:
VS = IF/n [Rct + 2RL + Ra ]VS = Setting VoltageIS = Setting CurrentIF = Fault level in CT Primaryn = CT Ratio
Rct = Resistance of CT at operating temperatureRL = Lead resistance at operating temperatureRa = Additional resistance due to relay,contact/connection resistance etc at operating temperature
The Full CT requirement is therefore : Class X, ratio N,CT resistance Rct and knee point voltage > 2 x Vs
Transformer DetailsTRF Capacity = 1600 kVATRF Primary = 11000 Volts
TRF Secondary = 400 VoltsTRF Impedance = 6.3 %
CT Primary(n) = 3000 AmpsCT Secondary = 1 Amps
n = 3000CT Secondary wiring Length = 30 Meters Neutral CT traveling distance
CT Secondary wiring size = 2.5 Sq.mmResistance of conductor = 7.41 Ohms / KM Refer the chart
CT resistance(RCT) = 12 Ohms CT Manufacturer to adviceCT magnitization current(Im) = 64 mA CT Manufacturer to advice
Fault level in CT Primary:IF = TRF Capacity x 1000 Example: IF=1600 x 1000 / 415 x 1.732 x 0.06 = 37100 Amps
TRF Secondary x 1.732 x ImpIF = 36658 Amps
Lead resistance:RL = CT Secondary wiring Length x Resistance of conductor per meterRL = 0.22 Ohms Example: RL=20 x 7.41/1000 = 0.15 Ohms
Additional Resistance:Ra is usually ignored,but may have the value 0.01ohms
Ra = 0.01 OhmsVS = IF/n [Rct + 2RL + Ra ] Example: VS=37000/2500 [8 + 2(0.15) + 0.01] = 123 VoltsVS = 152 Volt
CT Knee Point voltage must be in excess of 2 x VS:
VKn = 304 Volts Example: Vkn=2 x 123 = 246 Volt
Required Loop Resistance Value:RS = VS / ISIS = 50 %IS = 0.5 Amps Example: IS=0.2 x 1(CT Secondary Amps) = 0.2AIS = 0.5 Amps Example: IS=0.2 x 1(CT Secondary Amps) = 0.2A
VS = 152 Volts RS=123 / 0.2 = 615 OhmsRS = 304 Ohms
With the MREF relay the relay burden is less than 0.005VA and may therefore be neglectedRstab = 304 Ohms Stabilizing Resistor Value
Note:Under Fault Condition this resistor must pass
Value = 12.22 Amps Example: 37000 / (2500/1) = 14.8A
Peak Voltages:Under Fault conditions the peak voltage ignoring saturation of the C.T given by
VP = IF/n [Rct + 2RL + Ra + Rstab + Rr ] Rr = Relay resistance can be neglected= 3867 Volts Example: VP=37100/2500 [8 + 2(0.15) +0 .01 + 615] = 9250 Volt
VP = 3.867 KV
Peak Voltage including saturation of the CT given by Vpk Value must be below approximately 3KV
Vpk = 2 √ 2 Vkn [ Vp - Vkn ] Example: Vpk=2 √ 2 246 [ 9250 - 246 ] = 4209 Volt= 2944 Volt
Vpk = 2.94 KV
In Case the value exceed 3KV,we must adjust the setting current and re-caulculate as below:If the VPK value was less than 3KV please fill the same setting current value so as to attain the P.O.C value.
RS = VS / IS Example: IS=0.4 x 1 = 0.4AIS = Setting Current ( May be taken in % ) RS=123 / 0.4 = 307.5 OhmsIS = 20 % Enter the value until VPK falls below 3KVIS = 0.2 Amps
VS = 152 VoltsRS = 760 Ohms
Rstab = 760 Ohms Stabilizing Resistor ValueVP = IF/n [Rct + 2RL + Ra + Rstab + Rr ] Rr = Relay resistance can be neglected
9439 V lt= 9439 VoltVP = 9.439 KV
Vpk = 2 √ 2 Vkn [ Vp - Vkn ]= 4713 Volt
Vpk = 4.71 KV
Effective setting [ Primary operating Current ] 20 %Setting CurrentP.O.C = n [N x Im + Inr + Is]
N = The number of connected CTsIm = The magnitization current for a single CT at setting VoltageIs = Setting current
Inr = Non Linear resistor current at setting VoltageInr = [(Vs)
/ (MI)]4
Inr = 0 Amps Inr Value is Zero since Non-Linear Resistor not used.P.O.C = 1368 Amps Example: POC = 2500 [(4 x 0.013) + 0 + 0.4] = 1130Amps
% of Transformer rating = 45.6 %As per ESI 48-3 standard,the fault current setting shall be between 10% to 60% of the rated current of the winding.
Limiting Peak VoltageIf it is not possible to limit the peak voltage,by careful selection of setting current,a voltage dependent Non-Linear resistor should be used.A Non-Linear Resistor Must be used with 50 % setting
Vp = MV [ IF / n ]0.25
MV = Coefficient Value Refer the chartMV = 900 Example: Vp=450[3700/2500]0.25 = 883Volt
IF = 36658 Ampsn = 3000 Amps
Vp = 1683 Volt
Inr = [(Vs) / (MI)]4
Vs = 152 VoltMI = Coefficient Value
= 900Inr = 0.0008 Amps Example: Inr =[123/450]4 =0.0056Amps
P.O.C = 2270.4 Amps Example: POC = 2500 [(4 x 0.013) + 0.0056 + 0.2] = 644Amps% of Transformer rating = 75.68 %
As per ESI 48-3 standard,the fault current setting shall be between 10% to 60% of the rated current of the winding.
5 1 7.5 5 1 7.5 5 1 7.5
0 2 5 0 2 5 0 2 5
0 3 10 0 3 10 0 3 10
0 4 20 0 4 20 0 4 20
0 5 40 0 5 40 0 5 40
6 6 6
Is = 40% Is = 50%Is = 20%
Relay Setting - Front Panel - DIP Switch Position
P+B MREF Restricted Earth Fault Relay
2000kVA 1000kVA 1600kVA
Summary Sheet For Stabilizing Resistor
TransfomerCapacity
TransfomerPrimary
TransfomerSecondary
Transfomer% Impedance Busbar Rating Fault Level Incomer
1000kVA 11000 V 400 V 5% 2000A 65kA for 1Sec 2000AT/2000AF
1600kVA 11000 V 400 V 6.3% 3200A 65kA for 1Sec 3200AT/3200AF
2000kVA 11000 V 400 V 6.3% 4000A 65kA for 1Sec 4000AT/4000AF
Restricted Earth Fault Relay CT's
Distance Between Star Point(Neutral) of ''CT'' To Relay
Cable Size From Star Point(Neutral) of
''CT'' To Relay
CT Knee Point Voltage [Vkn]
CT Resistance [RCT]
CT magnetizing current [Im]
2000/1A CL.X 30 meters 2.5 Sq.mm 350 V 8 Ω -
3000/1A CL.X 30 meters 2.5 Sq.mm 500 V 12 Ω -
4000/1A CL.X 30 meters 2.5 Sq.mm 700 V 17 Ω -
Calculated Fault Current in "CT"
Primary [IF]
Calculated "CT"Knee point Voltage
[Vkn]
Relay Setting[% Is]
Stabilizing Resistor [Rstab]
Non-Linear Resistor (Metrosil)
Primary Operating
Current
% of Transformer
Rating
Current Transformer Details
6594_Resistor Vaue
Transfomer Details SwitchBoard Details
1 of 1 Dated : 3/12/2011