1 1_ 1 1_ 2 1_ 3
_ 2 _ 3
2 2_ 1 2_ 2 2 _ 3
_ 1 _ 1
3 3_ 1 3_ 2 3_ 3
IDL IL W IL W IL W
Un W Un W
IDL A IL W B IL W C IL W
Un W Un W
IDL IL W IL W IL 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
EQUATION1556 V2 EN (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:
IDL1 is the fundamental frequency differential current in phase L1 (in W1 side primary amperes)
IDL2 is the fundamental frequency differential current in phase L2 (in W1 side primary amperes)
IDL3 is the fundamental frequency differential current in phase L3 (in W1 side primary amperes)
IL1_W1 is the fundamental frequency phase current in phase L1 on the W1 side
IL2_W1 is the fundamental frequency phase current in phase L2 on the W1 side
IL3_W1 is the fundamental frequency phase current in phase L3 on the W1 side
IL1_W2 is the fundamental frequency phase current in phase L1 on the W2 side
IL2_W2 is the fundamental frequency phase current in phase L2 on the W2 side
IL3_W2 is the fundamental frequency phase current in phase L3 on the W2 side
IL1_W3 is the fundamental frequency phase current in phase L1 on the W3 side
IL2_W3 is the fundamental frequency phase current in phase L2 on the W3 side
IL3_W3 is the fundamental frequency phase current in phase L3 on the W3 side
Ur_W1 is transformer rated phase-to-phase voltage on the W1 side (setting parameter)
Ur_W2 is transformer rated phase-to-phase voltage on the W2 side (setting parameter)
Ur_W3 is transformer rated phase-to-phase voltage on the W3 side (setting parameter)
A, B and C are three by three matrices with numerical coefficients
Values of the matrix A, B and C coefficients depend on:
1. The Power transformer winding connection type, such as star (Y/y) or delta (D/
d)
2. The Transformer vector group such as Yd1, Dy11, YNautod5, Yy0d5 and so on,
which introduce phase displacement between individual windings currents in
multiples of 30°.
3. The Settings for elimination of zero sequence currents for the individual
windings.
Section 6 1MRK 502 048-UEN A
Differential protection
88
Technical manual
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