Abstract: The typical topological structure of 10 kV cable line is summarized and proposed according to the zero sequence trip event during the transformation of neutral grounding mode of substation. Combined with the practical work, the parallel small resistance grounding mode with arc suppression coil in the current pilot application is introduced in detail, and the recommended value of zero sequence protection is given. Combined with the case, the fault treatment process is explained in depth, the fault causes such as ground change tripping logic error and FA self-healing failure of cable lines are comprehensively analyzed, and the improvement measures are proposed, which lays a practical foundation for the key work of rapid isolation of grounding fault of urban distribution network.