Abstract: For poor actual protection effect of existing line selection methods based on characteristic quantity of single-phase grounding fault, a simulation model of mine power supply system was established in RTDS/RSCAD real-time digital simulation system taking an actual mine power supply system as research object. Fault characteristics laws of zero-module current and zero-module voltage of lines were analyzed under operation modes of ungrounded neutral and arc suppression coil grounded neutral. Influences of different fault location, initial phase angle of fault and grounding resistance on time domain characteristics of zero-module current were also researched under single-phase grounding fault of mine power supply system. The research results are as follows: ① Influences of neutral point operation mode on zero-module current of non-fault line and zero-module voltage of bus can be ignored, but influence on zero-module current of fault line is greater. Polarities of the first half wave of zero-module current in fault line and non-fault line are opposite under the two operation modes. ② The farther fault location away from the bus, the smaller impact value of transient zero-module current is. Fault location has less influence on steady-state zero-module current. ③ The larger of the initial phase angle of fault, the larger the impact value of transient zero-module current is, the slower the impact value grows, and the shorter time reaching steady-state of transient zero-module current of fault line is. The initial phase angle of fault has no influence on amplitude of steady-state zero-module current, which only affects initial phase angle. ④ The larger grounding resistance, the smaller impact value and its attenuation rate of transient zero-module current and amplitude of steady-state zero-module current are.