Fault phase selector for transmission line protective relaying using current fault components

When adopting the technique of single-phase automatic reclosing in EHV/UHV transmission line protection, fault phases should be selected correctly in advance. The relationships among the current sequence components for different faults are analyzed, and an efficient method for determining the fault phases is proposed, which is based on the analysis of phases-angle and amplitudes of the current sequence components. When a grounding fault occurs, A, B, or C region is judged by the phase-angle between the zero sequence and negative sequence components of the current. Each region contains a kind of single phase to ground fault and phase to phase with ground fault. Then the fault phases will be selected by the phases-angle between the abrupt discontinuous components of positive sequence and negative sequence components. The principle of the fault selector is simple and the margin of the phase-angle is big enough to select the fault phases. The selector proposed has excellent performance under high-resistance ground-fault conditions. Furthermore, the inequality between the positive sequence and negative sequence impedance of the system has no effect on the selector. In particular, the results of EMTP and physical simulations show that the selector can determine fault phases correctly and meet the requirement of phase-selection in real environment.