[本科]闭锁式方向纵联保护跳闸的必要条件是（  ）。

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69478' and id < 4500873 and id<>'4500873' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69478' and id > 4500873 and id<>'4500873' order by id asc limit 5