关键后备保护过负荷闭锁方案研究

Study on the blocking scheme for key backup protections against cascading trips

针对电网中关键位置后备保护过负荷跳闸易于引发连锁事故的情况,提出了一种适于在保护安装处实施的过负荷跳闸闭锁方案。根据主、后备保护配合原则,当区内故障导致后备保护动作时,必然有故障两侧的主保护或断路器动作信息,后备保护应开放;反之,若后备保护未收到任一主保护、断路器动作信息,则可判定过电流是过负荷造成的,应在线路热稳定极限前可靠闭锁后备保护。据此,文章提出了一种关键后备保护过负荷闭锁方案,详细给出了后备保护过负荷闭锁实现判据、信息搜索方法及程序流程,并进一步分析了提出方案在信息缺失、相邻变电站直流消失等情况下的动作行为。方案原理简单可靠,所需信息量少,在实际电网中具有可行性。

To avoid cascading trips caused by overload trips of key backup protections,a blocking scheme suitable for implementing in installation location of backup protection is presented.According to coordination relationship between main protection and backup protection,the following principle is proposed： there must be operating information from main protections and circuit breakers in case of in-zone short-circuit fault,and the pick-up of backup protection should be permitted.Otherwise,if none of the above information is received,then the pick-up of backup protection must be due to power transferring,and should be blocked within thermal stability time of line.On this basis,the blocking criterion,information searching method and program flowchart for the proposed scheme are given.And the operating performance of the proposed scheme is further analyzed in case of loss of information,failure of substation DC system,etc.The proposed scheme is with simple and reliable principle,small amount of information,and is executable in practical grid.