Failure Mechanism Analysis of High Resistance Grounding Fault Protection in Distribution Network

When a high resistance grounding fault originates in the distribution network line,the fault current flowing through the system is highly faint. At this time, the zero-sequence voltage and zero-sequence current of the feeder are more and more affected by the asymmetry of the three-phase grounding admittance, which makes the weak fault electrical characteristics of the high-resistance grounding fault more blurred. The difficulty of detecting and processing high-resistance grounding faults increases, and the number of long-standing faults that cannot be detected increases. In this paper, the characteristics of zero sequence voltage and feeder zero sequence current of asymmetric distribution network under high resistance grounding fault are analyzed in depth. The capacity that the distribution network can perceive transition resistance, the critical transition resistance when phase selection failure and the fuzzy boundary of feeder zero-sequence current fault characteristics are quantified respectively. The essential reasons for the failure of protection start-up, phase selection and line selection under high-resistance grounding fault are revealed.