电力系统是由 （       ） 等环节组成的。

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69632' and id < 4513474 and id<>'4513474' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69632' and id > 4513474 and id<>'4513474' order by id asc limit 5