VCB-12 series solid-sealed indoor vacuum circuit breaker is an indoor high-voltage switchgear for three-phase power system with rated voltage of 12 kV and frequency of 50 Hz. It is used as protection and control appliance due to vacuum circuit breaker. The special advantages are especially suitable for frequent operations requiring rated current or multiple short-circuit currents. VCB-12 series solid-sealed indoor vacuum circuit breakers are fixedly mounted, mainly used for fixed switchgear. The circuit breaker can be used alone or in ring power supply, box transformer or various non- power supply system.