当电力系统中发生不对称故障时，破坏三相系统运行状态的对称性，这时可采用(  )。

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69514' and id < 4503432 and id<>'4503432' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69514' and id > 4503432 and id<>'4503432' order by id asc limit 5