IEC 61850 User Feedback Task Force

To detect faults occurring between the busbar and the HV side of a transformer/autotransformer, a specific function based on impedance measurement is installed of the LV side of the transformer/autotransformer. This function shares similarities with the distance protection (PDIS) : it computes the 6 impedance loops based on voltage and current measurements to detect if a fault has occurred. However, to detect phase-to-ground faults, the traditional approach of using the k0 factor to compute the phase-to-ground impedance loops cannot be used as it is the case for distance protection, especially if the transformer coupling is delta-delta (residual current cannot flow). The phase-to-ground impedance loops are thus computed by simply dividing the voltage by the current without taking into consideration neither the k0 factor nor the residual current.

Proposal : a new LN (PIMP = Impedance protection ?), with associated DO and DA should be created to deal with this use case.