Adaptive Residual Current Compensation for Robust Fault-Type Selection in mho Elements

In order to accurately measure the impedance, the residual current for impedance measurement in ground distance relay is compensated in a fixed manner. It has been shown that the above compensation manner may have negative impact on the phase selection in mho elements in a single-pole trip scheme. A new residual current compensation method based on the magnitude of current of each phase for mho elements is presented in this paper. The performance of this new method is analyzed under all kinds of fault conditions. Simulation studies are carried out to investigate the new compensation method based fault component impedance relay in a typical transmission system. The relay has shown satisfactory performances under various fault conditions especially for the close-in ground fault and cross-country fault. This new compensation method can also be used in phase selector based on impedance measurement.