A Novel Method of Ground Fault Phase Selection in Weak-Infeed Side

The sequence current-based fault phase selector and traditional low-voltage fault phase selector have difficulties in being applied to the weak-infeed side. This study proposes a new method of ground fault phase selection for high-voltage/extra-high-voltage transmission-line protection under weak-infeed conditions. The method utilizes the relative phase-angle relationship between negative- and zero-sequence voltages and a relative phase relationship between superimposed positive-sequence voltage and superimposed negative-sequence voltage to identify the fault phase under weak-infeed conditions. Theory analysis and simulation have proven that the proposed method has high immunity against fault resistance as well as impedance phase-angle inequality and overload.