The product is used in the three-phase AC 50l_z power system of 40.5KV. It is used as the distribution room of power plants, substations and industrial and mining enterprises to receive and distribute electrical energy, and has functions of control, protection and monitoring for circuits. In addition to widely used in general power systems, it can also be used in frequent operating places. The normal use conditions stipulated in GB3906 - 1991 "3 ~ 35KV exchange metal closed switch equipment" are used.