双母线差动保护的复合电压(U0、U1、U2)闭锁元件，闭锁每一断路器失灵保护，其原因是（   ）。

试卷相关题目

SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69397' and id < 4492355 and id<>'4492355' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69397' and id > 4492355 and id<>'4492355' order by id asc limit 5