VITZROEM MCB is installed to promptly and accurately interrupt the over-current in case of a failure in the circuit after the secondary part of main transformer when the AC section is being operated. It is also a switch that performs the opening and closing of the main circuit in case of interrupting the fault current and at normal alternating current section and nonpressurized section. Thus, it has both roles of the breaker and the switch. This device is exclusively for the alternating current and interruption should not be carried out at the direct current section. This breaker is generally called the vacuumcircuit breaker (collectively, VCB) and uses the high dielectric strength at vacuumed state and the diffusion of arc. It is fixed inside the enclosed vacuum container and both electrodes of starting operation are arranged to interrupt the current by cutting off the electrodes.