不接地系统高阻接地故障特征及选线适用性分析

Characteristics of High-resistance Grounding Fault in Isolated Neutral Systems and the Adaptability Analysis of Fault Line Selection

在不接地系统中,相比于低阻接地故障,高阻接地故障电流更小,故障点更不稳定,故障选线难度更大。基于故障等值电路,分析了不接地系统高阻接地故障工频及暂态电流特征,并对故障与健全出线的故障工频及暂态电气量进行了比较。得到了故障电流随不同故障条件(过渡电阻、线路电感、系统对地电容、故障初始相角)的变化规律。证明了现有常用的暂态电流幅值比较、极性比较以及暂态功率方向判别等选线方法仍适用于不接地系统高阻接地故障。若借助故障工频电气量辅助选线,可提高选线可靠性。最后,利用仿真验证了故障特征及选线方法的正确性。

In an isolated neutral system,compared with the low-resistance grounding fault,the high-resistance ground-ing fault current is smaller and the fault location is more unstable,which leads to higher difficulty in fault line selection.Based on a fault equivalent circuit,the high-resistance grounding fault characteristics of power frequency current andtransient current in the isolated neutral system are analyzed,and the power frequency and transient current informationare compared between the fault and healthy lines. The changing rule of the fault current under different fault conditions(e.g.,fault resistance,line inductance,capacitance to earth and initial phase angle)is obtained. It is proved that theline selection methods such as transient current amplitude comparison,polarity comparison and transient power direc-tion selection can also be applied to the isolated neutral system under high-resistance grounding fault. Moreover,if thefault power frequency information is applied to assist the line selection,then the selection reliability will be improved.Finally,simulation results verify the validity of fault characteristics and line selection methods.