超高压线路单相接地故障时，潜供电流产生的原因是(    )。

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69532' and id < 4505198 and id<>'4505198' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69532' and id > 4505198 and id<>'4505198' order by id asc limit 5