Through analyzing the two cases of protection malfunction due to incorrect connection of open - delta connection of busbar voltage transformer , the importance of correct connection of open - delta connection when earthing fault occurring in a power system was explained 摘要通過分析兩起母線電壓互感器開口三角形接線錯誤引起的保護(hù)不正確動作,從而說明在系統(tǒng)發(fā)生接地故障時電壓互感器開口三角形接線正確的重要性。