High voltage equipment according to their different functions and effects can be divided into: (1) the elements and combinations include: circuit breakers, disconnectors, grounding switches, reclosers, breaking device, load switches, contactors, fuses and a combination of the above elements load switch - fuse combinations, contact - fuse (FC) combinations, isolation load switch, fuse switch, open type electrical appliances. (2) complete sets of equipment: the above elements and in combination with other electrical appliances (such as transformers, current transformers, voltage mutual high-voltage distribution cabinet high-voltage distribution cabinet sensors, capacitors, reactors, surge arresters, bus, into the bushing , cable terminals and secondary elements, etc.) the rational allocation of organically combined in a metal enclosure, with a relatively complete use of functional products. The metal-enclosed switchgear (switchgear), gas-insulated metal-enclosed switchgear (GIS), and high / low voltage prefabri