某220kV变电站220kV 某开关无保护动作跳闸，伴有直流接地告警信号，直流接地时母线绝缘监测报“电阻R+ 001.7k 电阻R- 000.8k”，即直流正负均接地，但无支路直流空开跳闸且无接地选线记录。试讨论有可能产生这种现象的原因。
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