Faulty Feeder Detection of Single Phase-Earth Fault Using Grey Relation Degree in Resonant Grounding System
It is difficult to detect the faulty feeder if single phase-earth faults occur in a resonant grounding system, mainly due to its very low-current fault. Since the similarity of transient zero-sequence current waveforms between faulty feeder and sound feeder is lower than that between two sound feeders, this paper presents a protection scheme for faulty feeder detection based on the grey relation degree that can characterize the similarity among curves. Slope relation degree, one kind of grey relation degree, is chosen to characterize the similarity of transient zero-sequence current waveforms between one feeder and other feeders, and the slope relation matrix that represents the relationship among all feeders can be established. The protection criterion established by using the slope relation matrix can be applied to detect the faulty feeder of single phase-earth faults. It is noted that the proposed method is applicable to the system where at least three or more feeders are presented. Electromagnetic Transients Program (EMTP) simulation results and adaptability analysis have confirmed the effectiveness and reliability of the proposed scheme.