Location of single phase disconnection fault with non-grounding in distribution grid based on positive sequence voltage

A fault location method of single phase disconnection fault with non-grounding is proposed which is based on the characteristic of positive sequence voltage decrease after fault occurs. Based on three-phase voltage of distribution transformers, positive sequence voltage is calculated using the method of symmetrical components. The positive sequence voltage at the high voltage side (HV side) of a distribution transformer located behind the fault point is far less than that at the front of it or at a non-fault distribution line, and the positive sequence voltage at the low voltage side (LV side) behind the fault point becomes about 50% of that before the fault occurs. According to characteristic of positive sequence voltage decreasing, the paper calculates the positive sequence voltage of each load point in real time. If the positive sequence voltage of a load point at a time becomes significantly smaller with the positive sequence voltage of its´ downstream load point at the same time becoming smaller too and the positive sequence voltage of its´ upstream load point without changing, the fault is single phase disconnection fault with non-grounding. Its´ location is between the load point and its´ upstream load point. Simulation studies fully verify the validity of the algorithm.