相间接地故障时常规选相元件动作行为分析及改进措施

Analysis of phase selector action and improving scheme for two-phase-to-ground fault

针对高压线路相间接地故障时两故障相对地电阻可能不均衡的现象,通过对典型相间接地故障模型进行分析,总结出故障电流特点,并分析了此类故障情况下两种典型选相元件的动作行为。在此基础上,提出了相电流突变量的附加选相判据结合序分量的选相判据的综合选相方法。PSCAD和RTDS仿真表明两故障相对地电阻不对称的相间接地故障时,可能导致距离保护常规单独基于相间电流突变量原理和序分量原理的选相元件不正确动作,并验证了提出的综合选相方法的有效性。

For a two-phase-to-ground fault occurred on high-voltage transmission line, if the grounded resistances is unequal, traditional phase selectors may lead to mal-operation of distance protection. In this paper, a fault model is established to analyze this kind of fault. The characteristic of fault current is derived based on the fault model. The behavior of several typical selectors based on difference of phase currents and sequence component are analyzed under the fault condition of two unequal phase-to-ground fault resistances. Based on the analysis results, a kind of synthesis selection scheme, which takes the additional criterion based on phase superimposed component and the phase selector based on sequence component as supplementary method, is proposed. Simulations with PSCAD and the real time digital simulator （RTDS） show that the condition may cause the mal-operation of the selector, and verify the effectiveness of the synthesis selection scheme.