Developmentofsinglebreak420kVGCB,Developmentofsynchronousswitchingcontrollerforgascircuitbreakers,EMTPsimulationofSLFinterruptingperformancefortwaseriallyconnectedarcswithdifferentarcparameters,Feasibilitystudyonapplicationofhighvoltageandhighpowervacuumcircuitbreaker.