Identification and location method of asymmetric faults in coal mine power network

Three asymmetrical faults of singe-phase grounding, singe-phase line breakage and ferroresonance in coal mine power network are easily misjudged, and existing methods hardly identify the three faults correctly. In order to solve above problems, fault sequence characteristics of singe-phase grounding, singe-phase line breakage and power-frequency ferroresonance were analyzed, and distribution laws of sequence current in coal mine power network were obtained, which showed that negative-sequence current only flowed through fault line and preceding power network, while negative-sequence current in non-fault lines was zero , and there was no negative-sequence current and only weak zero-sequence current in power network under the condition of ferroresonance fault. On this basis, an identification and location method of asymmetrical faults in coal mine power network was proposed. The method uses negative-sequence current to judge ferroresonance fault, zero-sequence current to identify singe-phase grounding or singe-phase line breakage fault, and distribution coefficient of negative-sequence current to locate fault line. The simulation results show that the method can identify and locate the three asymmetrical faults in coal mine power network correctly and reliably.