ZN12-40.5 indoor HV vacuum circuit breaker is an indoor HV switchgear with rated voltage of 40.5kV and three-phase ac of 50HZ. It is manufactured by Siemens 3AF technology introduced from Germany. The circuit breaker mechanism is integrated with the switch. The special spring energy storage type operating mechanism can be operated by AC/DC energy storage or manually. This circuit breaker has simple structure, strong breaking ability, long life, complete operation function, no explosion risk, simple maintenance, suitable for power plant, urban power grid, substation and other transmission and distribution system control or protection switch, especially suitable for breaking important load and frequent operation place.