针对当前煤矿井下选择性漏电保护存在的不足,对零序电流方向式漏电保护工作原理进行重点研究,提出采用零序电压启动,比较零序电压和零序电流的相位的方法来判断零序电流方向,从而实现选择性漏电保护。方案实施以DSP为控制核心,通过软件实现零序电压和零序电流的比相,最后给出硬件电路设计及软件程序流程图,并试验验证了对漏电故障正确的选择性保护。 Aiming at the shortcomings of selective leakage protection in coal mine at present, the working principle of zero-sequence current directional leakage protection is mainly studied. The zero-sequence voltage start-up, comparison of zero-sequence voltage and phase of zero- Direction, in order to achieve selective leakage protection. Program implementation to DSP as the core control, the zero-sequence voltage and zero sequence current phase ratio by software, and finally gives the hardware circuit design and software program flow chart, and test to verify the correct selective protection of leakage fault.