The switch oversteptrip incidents of two substations are described and the causes of its misoperation are analyzed. One is the mismatching of line overcurrent time(1 s) and switch instant trip time(0.7 s).

• 说明了2座变电站开关越级跳闸的事故情况；分析了西门子7SJ600装置在天津电网运行中2次拒动的原因:1次是线路的过电流时间(1s)与开关速断保护时间(0.；7s)不配合；造成相应开关跳闸;