Abstract: At present, most of the research on underground power supply system grounding fault positioning in coal mine adopts the transient method, which needs to collect zero sequence voltage and zero sequence current of the line at the same time. Because it is difficult to collect zero sequence voltage accurately, it is easy to misjudge the normal operation section as the fault operation section when positioning the fault section, resulting in leapfrog tripping phenomenon. However, the current protection scheme for leapfrog tripping of underground power supply system is not suitable for neutral grounded system through arc suppression coil, and the cost is relatively high. In order to solve those problems, this paper presents an underground power supply system grounding fault section positioning method based on wide-area current transient component. When grounding fault occurs in underground power supply system of coal mine, the direction of zero-sequence current flowing through normal line and fault line is different. The closing opening difference operation (CODO) in mathematical morphology is used to extract the direction information of transient zero-sequence current of each line. The selection of structural element length in COCD plays a decisive role in the output of underground power supply system. The particle swarm optimization (PSO) algorithm is used to adaptively optimize the length of structural element, and the reliable extraction of polarity characteristics of grounding fault transient zero sequence current direction is realized. Based on the topology of multi-level power supply system, the polarity signals of the zero sequence current transient component output by the protection elements on each line are logically calculated. When the value is 1, the line is a normal operation line, and when the value is 0, the line is a fault line. Therefore, the precise positioning of the fault section is realized. Based on the neutral ungrounded system and the neutral grounded system through arc suppression coil, the positioning method is verified. The results show that the underground power supply system grounding fault section positioning method based on wide-area current transient component only needs to collect the zero-sequence current, and the method can achieve accurate positioning of the fault section in the operation mode of the neutral ungrounded and the neutral grounded through the arc suppression coil.