Customer : Project : ABB Ref.no. :
Vk Value calculation forTransformer Diff. Protection ( Relay used : CAG34)
System Voltage in kV 11CT Primary 1200CT Secondary ( 1 or 5A) 1Trasnformer rating in kVA 500Rct (CT Sec.) 8RL (Lead Resistance) 100
Formula : Vk = 40 I (Rct+2RL) Vk 394.40 Vk value required is 414 Volts
Magnetising current, Ie < 30mA at VK / 2
Customer : Project : ABB Ref.no. :
Vk Value calculation forTransformer REF Protection ( Relay used : CAG14)
System Voltage in kV 6.6CT Primary 250CT Secondary ( 1 or 5A) 1Trasnformer rating in kVA 2250Percentage Impedence ( Z %) 6.5Rct (CT Sec.) 2RL (Lead Resistance) 5
196.83
3028.15
If 12.11
Formula : Vk = 2 If (Rct+2RL) Vk 50.70 Vk value required is 56 Volts
Magnetising current, Ie < 30mA at VK / 2
Full load current = Transformer Rating / ( V3 / System Voltage)
Fault current = Full load current / Percentage Impedence
Fault Current reflected to CT Sec. = (Fault current / CT Primary) x CT Secondary
Customer : Project : ABB Ref.no. :
Vk Value calculation forMotor Diff. Protection ( Relay used : CAG34)
System Voltage in kV 6.6 KVCT Primary 350 ACT Secondary ( 1 or 5A) 1 AMotor rating 2555 kWPower factor 0.8 Cos Percentage Impedence ( Z %) 8 %Rct (CT Sec.) 2 OhmRL (Lead Resistance) 5 Mtrs.
279.39
3492.36
If 9.98
Formula : Vk = 2 If (Rct+2RL) Vk 41.77 Vk value required is 46 Volts
Magnetising current, Ie < 30mA at VK / 2
Full load current = Transformer Rating / ( V3 / System Voltage)
Fault current = Full load current / Percentage Impedence
Fault Current reflected to CT Sec. = (Fault current / CT Primary) x CT Secondary
Customer : Project : ABB Ref.no. :
Vk Value calculation forStabilising Resistors & Metrocils ( Relay used : CAG34)
System Voltage in kV 6.6 KVCT Primary 250 ACT Secondary ( 1 or 5A) 1 AMotor rating 1805 kWPower factor 0.8 Cos Percentage Impedence ( Z %) 8 %Rct (CT Sec.) 2 OhmRL (Lead Resistance) 5 Mtrs.Relay rated current (1 or 5A) 1 AAssuming relay setting (10-40%) 0.1Relay burden at setting current 1 VARelay setting in Amp (Is) 0.1 A
197.38
2467.21
If 9.87
Formula : Vk = 2 If (Rct+2RL) Vk 41.31 Vk value required is 45 Volts
Magnetising current, Ie < 30mA at VK / 2
Voltage across relay Vr 20.66 Formula : Vr = If (Rct+2RL)
Stabilising Resistor Rs 106.55
Vk 2038.45
V Peak 812.30
Full load current = Transformer Rating / ( V3 / System Voltage)
Fault current = Full load current / Percentage Impedence
Fault Current reflected to CT Sec. = (Fault current / CT Primary) x CT Secondary
Formula : Rs = {Vr-Is - VA Burden of Relay / (Is) Sq.}
Vf = Maximum volts that would produce if CT did not sature under internal faults.
Formula : Vf = If {Rs + VA Burden of Relay / (Is) Sq.}
V Peak = Peak Volts developed by CT under internal faults
Formula : V Peak = 2 V2 Sqrt ( Vk ( Vf -Vk ) )
Top Related