基于相序电流一致性的小电流接地故障方向算法

Algorithm of Small Current Grounding Fault Direction Based on Consistency of Phase Current Fault Component and Zero-sequence Current

为解决小电流接地系统故障方向保护问题,提出一种基于三相稳态电流突变量与零序电流一致性关系的小电流接地系统故障方向算法。根据小电流接地系统中单相接地故障后三相电流突变量变化特征得出,在接地故障发生后,健全路径三相电流突变量与零序电流一致性关系相同;不接地系统中故障点上游故障路径三相电流突变量与零序电流的一致性关系存在明显差异;而谐振接地系统中故障点上游故障路径三相电流突变量与零序电流的一致性关系主要取决于消弧线圈失谐度。利用三相稳态电流突变量与零序电流的一致性关系可实现故障方向判断,仿真和现场实验验证了方法的正确性。

To solve the problem of fault direction protection in a small current grounding system,a fault direction algorithm based on the consistency relationship between the three-phase steady-state current fault component and zero-sequence current is proposed. The characteristics of three-phase current fault component under single-phase grounding fault in the small current grounding system are analyzed. It is found that under the grounding fault,the three-phase current fault component in the non-fault path has the same consistency relationship as the zero-sequence current,while there are obvious differences in the consistency relationship between the three-phase current fault component in the fault path before the fault point and zero-sequence current in the ungrounded system. However,in a resonant grounding system,the consistency relationship between the three-phase current fault component and zero-sequence current in the fault path before the fault point mainly depends on the arc extinguishing coil’s detuning degree. The fault direction judgment can be realized by using the consistency relationship between the three-phase steady-state current fault component and zero-sequence current,and the proposed method was verified by simulation results and field test data.