小电阻接地系统零序电流Ⅱ段保护整定策略研究

小电阻接地系统发生接地故障时,各级零序电流保护动作切除接地故障,该故障电流包括短路电流和电容电流,在整定零序电流Ⅱ段保护定值时必须考虑电容电流对10 kV线路零序保护和主变低后备零序定值的影响.利用图示说明10 kV线路发生单相接地时电容电流和故障电流的流向,定性地计算10 kV线路发生单相接地时,线路零序保护和主变低后备零序电流保护获得的故障电流的大小,为主变低压侧零序电流Ⅱ段保护和10 kV线路零序电流Ⅱ段保护的定值配合提供参考数据.

Study on Definite-time of Zero Sequence Over-current Protection Settings for Low Resistance Grounding System

The zero sequence over-current protection would clear fault in low resistance ground system. The fault current contains the short circuit and the capacitance current. Therefore, the effects of capacitance current on zero sequence protection of 10 kV line and transformer backup zero sequence protection should be considered, especially for the value setting of definite-time of zero sequence over-current protection. The direction of capacitance current and fault current of 10kV line is investigated. The quantitative effects of single-line ground fault on line zero sequence protection and transformer backup zero sequence protection are analyzed. It provides a reference for coordinating protection settings between transformer backup definite-time of zero sequence protection and 10kV line definite-time of zero sequence protection.