对输电线反时限零序电流保护选择性的分析

通过对接地故障零序电流分布的分析,讨论了特殊电网方式下输电线零序反时限电流保护不能保证选择性的问题。即在某些情况下,相邻线路中的零序电流不一定小于故障线中的零序电流。从而可能造成相邻线路反时限零序保护的误动,即使考虑相继动作也不能保证其选择性。作为零序保护简化的一种选择,宜在反时限特性中增加一段附加延时,将反时限零序保护作为接地距离保护的补充,用以反应高阻接地故障。

Analysis of inverse time zero-sequence current relay and its selectivity

This paper analyzes the distribution of zerosequence current to ground faults.It discusses that in some operating conditions,zero-sequence current of the fault line maybe less than or equal to the next line.So the inverse time zero-sequence relay of next line will trip before the fault line.Even if the breakers of the the next line trip successively,the selectivity of inverse time zero-sequence current relay can not be provided.As an alternative of simplifying zero-sequence protection,inverse time zero-sequence current protection with a lagged timer can be used as an auxiliary to the grounding distance protection.It will provide sensitivity to high impedance ground faults.