500kV系统的平均额定电压为(  )。

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69513' and id < 4503354 and id<>'4503354' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69513' and id > 4503354 and id<>'4503354' order by id asc limit 5