工频过电压的特点是频率低，持续时间短。（    ）

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69489' and id < 4501347 and id<>'4501347' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69489' and id > 4501347 and id<>'4501347' order by id asc limit 5