小电流接地系统异名相接地故障分析及跳闸策略研究

Analysis of Ground Fault Occurred in Different Phases and Research on Tripping Strategy in Small Current Grounding System

城市低压电网一般采用小电流接地系统、电缆供电方式,单一馈供线路发生接地故障容易引起其他线路电缆击穿而多点接地。两条线路不同相别同时存在接地点时,由于中性点消弧线圈感性注入电流的影响,对两故障相合成故障电流产生不同助增与汲出作用,进一步可能导致保护装置无法正确动作。从小电流接地系统不同线路异名相两点接地故障差流故障电流入手,结合线性叠加原理,推导了故障电流偏差计算公式及产生原因,通过将过电流保护模块与接地距离保护模块配合使用,快速确定并跳开两条接地故障线路,防止进一步绝缘击穿引发的故障范围扩大。通过实际电网故障模型仿真证明了方法的正确性与可靠性,具有一定的理论与工程应用价值。

There are a lot of problems of two-point ground fault occurred in different phases and different lines caused by single-phase ground fault in small current grounding systems. When two-point ground fault occurs in different phases in arc suppression coil grounding system,due to the influence of neutral point current injection,there is a deviation of different fault phases current in the two fault lines,and the protection can not trip accurately. Based on linear superposition principle,the deviation calculation formula and reasons are derived theoretically,and through using over-current protection module and grounding distance protection module,the two grounding fault lines are determined and tripped quickly,which prevents the expansion of fault scope caused by the further insulation breakdown. The simulation of actual grid fault model proves the correctness and reliability of the proposed method,which has certain theoretical and engineering application value.