Abstract: Single phase-to-ground fault-detection for distribution system has been a challenge for many years, but the research has been mainly concentrated on permanent grounding fault, which is not general. Actually, the unstable arc-grounding and intermittent arc-grounding faults, which are kind of non-permanent grounding faults, are most likely to occur in the power system. When non-permanent arc-grounding fault happens, many high frequency components will be produced correspondingly. An adaptive notch filter (ANF) algorithm is introduced in this paper to extract the fifth harmonics signal of zero-sequence current . The algorithm can track the change of signal automatically by adjusting its own parameters. Thus it can accurately extract the real-time fifth harmonics signal. Empirical results show that the proposed method can find the fault feeder correctly when non-permanent grounding fault occurs. The principle is simple and reliable.

Key words: distribution system, intermittent arc-grounding, selection of fault feeder, ANF, fifth harmonics