母线差动保护采用电压闭锁元件的主要目的是（  ）。

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69479' and id < 4501057 and id<>'4501057' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69479' and id > 4501057 and id<>'4501057' order by id asc limit 5