一起110kV线路故障引起主变后备保护动作的原因分析

Reason analysis of transformer backup protection operates when the fault locates in transmission line

在一次110kV线路因覆冰影响发生单相接地故障时,造成线路保护与主变中压侧后备保护同时动作,经变电站运行人员检查设备动作情况,确定线路开关确已分开,主变中压侧后备保护动作并非线路开关拒动引起。进一步对主变中压侧后备保护的动作行为进行了分析,确定了主变中压侧后备保护动作的原因为零序过流保护与零序方向过流保护因灵敏度不同,造成保护失配,最后提出了应该吸取的经验教训。

When a 110 kV transmission line had the single-phase grounding fault because of ice recovering, it caused the line protection and the main transformer backup protection acted in the same time. After the examination of electric equipment, they definite that the transmission line circuit breaker has separated, and the main transformer backup protection movement was not caused by the resistance to move of the transmission line circuit breaker. Further analysis on the movement behavior of the main transformer backup protection, they determined the reason of the main transformer backup protection movement was the sensitivity between zero foreword overflow protection and zero foreword direction overflow protection was different, which caused the protection unbalance. Finally, the lessons are proposed.