单相接地故障时电压选相元件的研究

Research on voltage selector for single-phase earth fault

通过对单相接地故障各电气量的分析,指出了在大电流接地系统中,尤其是在线路出口(保护安装处)发生单相接地故障时,若低电压选相元件电压定值选择不合适容易导致误选相。提出在各相(故障相和非故障相)电压接近时,采用零序电压补偿的低压选相方案,三相电压均采用零序补偿,补偿后的故障相电压幅值降低,非故障相电压升高。低电压选相元件以补偿后的三相电压进行选相,具有很好的灵敏度。EMTP数字仿真验证了其正确性和实用性。

After analyzing the electrical quantities of the single phase grounding faults, it is clear that in the grounded neutral system, especially when the single phase grounding fault occurs at the beginning of the transmission line （or at the relay location）, if the settings of the low-voltage selector is improper, it will lead to incorrect phase selection. When the voltage ofeach phase （the fault phase and the healthy phase） is close to each other, the low-voltage selection based on zero-sequence voltage compensation should be adopted. The three-phase voltages all use zero sequence compensation. After the compensation, the amplitude of the fault phase voltage becomes lower, while the amplitude of healthy phase becomes higher. Then the low-voltage selector can select the fault phase based on the three-phase voltages after the zero sequence compensation, which has very good sensitivity. EMTP simulations proved its validity and utility.