FZN21-12D/T630-20, FZN21-12DR/T125-31.5 high-voltage vacuum load switches and combination devices are used in three-phase AC 10KV, 50Hz distribution systems. It has the advantages of compact structure, small size, light weight, long service life, strong closing and breaking ability, safety and reliability. When used in conjunction with fuses (referred to as combination appliances), it can replace expensive circuit breakers, and its operation and maintenance are simple and convenient.