在电力系统正常状况下，220V单相供电的用户受电端的供电电压允许偏差为额定值的(    )。

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69458' and id < 4498300 and id<>'4498300' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69458' and id > 4498300 and id<>'4498300' order by id asc limit 5