VKB-12 Indoor Vacuum Circuit Breaker is a new indoor switchgear with new generation of enclosed type pole and high endurance in the electric power system of three-phase AC 50HZ, and rated voltage of 12KV. The circuit breaker adopts modularized elastic spring actuator, so it has high reliability and easy maintenance, and applies to adverse working conditions. The whole series of products have passed type test of GB and IEC standard, own the switching capacitor C2 level capacity, and can be used as the updating products of sleeve type vacuum breakers of VS1, etc.