ZW28 is applicable to outdoor three-phase AC power distribution system with rated voltage of 12kV and rated frequency of 50Hz, which is used for opening and closing load current and closing short circuit current. It is applicable to substations, industrial and mining enterprises, urban and rural power grids as protection cities, agricultural power grids, automatic distribution networks and places with frequent operation. It has manual and electric operation functions. The switch body adopts the technology of Toshiba, Japan. This switch is maintenance-free. Vacuum arc extinguishing and SF6 gas are used as insulation medium to ground and between phases. It can be used as outdoor boundary vacuum circuit breaker with fault detection function, protection control function and communication function. It is installed on 10KV overhead line and can realize automatic removal of single-phase ground fault and automatic isolation of interphase short circuit fault. The installation point is applicable to the responsibility dividing point of the incoming line of the 10KV distribution line user, and also to the branch line connection meeting the requirements. Automatically lock the interphase short circuit fault, quickly locate the fault point and automatically remove the single-phase grounding fault.