Figure. 5.4.18. - 84. Correctly selected transformer setting prevents the differential function operation in out of zone earth faults.
This selection basically does for the “N” or “n” selected side or both of them the zero sequence
elimination by applying the before mentioned correction.
Important note!: By enabling the zero sequence compensation by selecting the “N” or “n” in the
transformer vector group, simultaneously the sensitivity to single phase one end fault will decrease by
1/3. For this reason restricted earth fault protection should be enabled for the zero sequence
compensated side. Restricted earth fault enabling requires that in addition to phase currents
measurement also the starpoint current is available and can be connected to the residual current
channel of the relay on corresponding (HV/LV) side measurement.
AQ-T257
Instruction manual
Version: 2.00
© Arcteq Relays Ltd
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