母线电流差动保护采用电压闭锁元件，主要是为了防止（   ）。

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69381' and id < 4491730 and id<>'4491730' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69381' and id > 4491730 and id<>'4491730' order by id asc limit 5