Study on Identification Method of Single Phase Permanent Ground Fault in Distribution Network Feedout Line

Abstract

The single phase ground fault of the distribution network is related to the change of the fault transition resistance. With the increase of the transition resistance, the fault current will decrease and the fault will disappear; with the decrease of the transition resistance, the original fault will be strengthened; if the transition resistance remains unchanged, it will be a stable permanent fault.Using the zero sequence component of the fault feeder to construct the V-I curve, calculate the curve area and make a straight-line fitting, using the slope of the straight-line to infer the change of the fault transition resistance, and then infer the nature of the single-phase ground fault.According to the prediction of fault nature, the neutral point is put into arc suppression coil or small resistance correspondingly. The phase and amplitude changes of zero sequence current caused by the change of neutral point are used to check whether the fault disappears, and the nature of single-phase ground fault is further determined. This identification method is easy to realize in engineering application, and can improve the self-healing ability of distribution network and the adaptability of single-phase grounding protection.