三段式过电流保护中，（   ）是后备保护。

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69376' and id < 4491185 and id<>'4491185' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69376' and id > 4491185 and id<>'4491185' order by id asc limit 5