Abstract: Frequency voltage rise to 1.4 times operation in the power grid is rare, all levels of grid voltage by all levels of scheduling according to the jurisdiction of the scope of responsibility for the adjustment, the grid in normal operation is not likely to be the phenomenon of frequency voltage rise. This case belongs to the new equipment put into operation, its 220 kV bus voltage is not in the range of grid scheduling monitoring point, industrial frequency voltage rise operation 9 minutes 31 seconds, at the same time, due to the bus-side isolation switch closing is not in place, resulting in the bus-side GIS isolation switch gas chamber explosion; due to the line shunt reactor turn-to-turn protection error adjustment, resulting in the action of the protection.