A novel phase selection element

This paper investigate the phase selection element used for zero sequence current differential protection and negative sequence current differential protection. Faulted phase is specified by phase relationship of sequence components of differential currents in the fault branch: the negative sequence component of the three-phase differential current is in phase with the negative sequence current of the fault branch, and by subtracting the capacitive current caused by system power source from the positive sequence component of the three-phase differential current, the corrected positive sequence differential current is in phase with the positive sequence current of the fault branch. Then, based on the phase relationship between the negative sequence differential current and the corrected positive sequence differential current, the faulted phase can be selected. The phase selection element proposed in the paper is immune to the distributed capacitive current along the line, is available during the whole fault period with high sensitivity. Simulation based on PSCAD model verified the validity of proposed phase selection element.