Switch cabinet (switch cabinet) is a kind of electrical equipment, switch cabinet outside the line first into the cabinet main control switch, and then into the sub-control switch, each sub-circuit according to its needs set. Such as instrumentation, automatic control, motor magnetic switch, a variety of AC contactors, etc., some also have a high-voltage room and low-voltage room switch cabinet, with high-voltage bus, such as power plants, etc., some also have to protect the main equipment of low-week load shedding. Switchgear (switchgear) is the main role in the power system for power generation, transmission, distribution and conversion of electrical energy in the process of opening and closing, control and protection of electrical equipment. Switchgear components are mainly circuit breakers, disconnect switches, load switches, operating mechanisms, transformers and insulation components of the protection device. Among them, the role of insulation components for support, load-bearing, isolation and other requirements, so the insulation material requirements for: higher electrical strength, higher mechanical strength, more able to resist arc, etc.. Commonly used GPO3