Abstract: Because zero-sequence voltage or zero sequence current can not reach fixed value,selective leakage protection can not function properly in the coal mine when mine low-voltage power lines use selective leakage protection.In response to these issues,this paper analyzes the phase relationship among negative sequence voltage and zero-sequence voltage and negative sequence current and zero sequence current in ground faults.The phase angle difference between negative sequence voltage and zero-phase sequence voltage is in 0 ° ～ 45 °,and the phase angle difference between the negative sequence current and zero sequence current is 0 °.Accordingly,the paper proposes that the zero-sequence voltage or zero sequence current can be insteaded by the negative sequence voltage or negative sequence current to determine the direction of zero sequence power and achieve selective protection when zero-sequence voltage or zero sequence current will not reach the fixed value.