_ _ 1 _ _ 2
_ 2
_ _ 1 _ _ 2
_ 1
_ _ 1 _ _ 2
IDA I A W I A W
Vn W
IDB A I B W B I B W
Vn W
IDC I C W I C W
é ù é ù é ù
ê ú ê ú ê ú
= × + × ×
ê ú ê ú ê ú
ê ú ê ú ê ú
ë û ë û ë û
_ _ 1 _ _ 2
_ 2
_ _ 1 _ _ 2
_ 1
_ _ 1 _ _ 2
IDA I A W I A W
Vn W
IDB A I B W B I B W
Vn W
IDC I C W I C W
é ù é ù é ù
ê ú ê ú ê ú
= × + × ×
ê ú ê ú ê ú
ê ú ê ú ê ú
ë û ë û ë û
_ _ 1 _ _ 2
_ 2
_ _ 1 _ _ 2
_ 1
_ _ 1 _ _ 2
IDA I A W I A W
Vn W
IDB A I B W B I B W
Vn W
IDC I C W I C W
é ù é ù é ù
ê ú ê ú ê ú
= × + × ×
ê ú ê ú ê ú
ê ú ê ú ê ú
ë û ë û ë û
EQUATION1879 V1 EN-US (Equation 1)
where:
1. is the resulting Differential Currents
2. is the current contribution from the W1 side
3. is the current contribution from the W2 side
_ _ 1 _ _ 2 _ _ 3
_ 2 _ 3
_ _ 1 _ _ 2 _ _ 3
_ 1 _ 1
_ _ 1 _ _ 2 _ _ 3
IDA I A W I A W IL A W
Vn W Vn W
IDB A I B W B I B W C IL B W
Vn W Vn W
IDC I C W I C W IL C W
é ù é ù é ù é ù
ê ú ê ú ê ú ê ú
= × + × × + × ×
ê ú ê ú ê ú ê ú
ê ú ê ú ê ú ê ú
ë û ë û ë û ë û
EQUATION1882-ANSI V1 EN-US (Equation 2)
where:
1. is the resulting Differential Currents
2. is the current contribution from the W1 side
3. is the current contribution from the W2 side
4. is the current contribution from the W3 side
and where, for equation 1 and equation 2:
ID_A is the fundamental frequency differential current in phaseA (in W1 side primary
amperes)
ID_B is the fundamental frequency differential current in phase B (in W1 side primary
amperes)
ID_C is the fundamental frequency differential current in phaseC (in W1 side primary
amperes)
I_A_W1 is the fundamental frequency phase current in phaseA on the W1 side
I_B_W1 is the fundamental frequency phase current in phaseB on the W1 side
I_C_W1 is the fundamental frequency phase current in phaseC on the W1 side
I_A_W2 is the fundamental frequency phase current in phaseA on the W2 side
I_B_W2 is the fundamental frequency phase current in phase B on the W2 side
I_C_W2 is the fundamental frequency phase current in phase C on the W2 side
Table continues on next page
Section 6 1MRK 502 066-UUS B
Differential protection
120
Technical manual
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