The switchgear consists of a fixed cabinet and a vacuum circuit breaker. The outer casing and the partition are made of high-quality steel plate. They have strong anti-oxidation and corrosion resistance, and the rigidity and mechanical strength are higher than ordinary low-carbon steel. Pressure relief plates are mounted on the top of the three high-pressure chambers. In the event of an internal fault, the pressure generated in the chamber can be released through the openings since the door is securely sealed.

Locking/protection against unauthorized use.

With a series of interlocking devices, the functions can be summarized as follows:

• The circuit breaker can be closed (mechanical and electrical interlock) when the handcart is fully in the test or operating position.
• When the handcart is in the test or running position without controlling voltage, the circuit breaker can not close, but can only open manually (electrical interlock).
• When the handcart is in the test or running position without control voltage, the circuit breaker cannot be closed and can only be manually opened (electrical interlock)
• When the handcart is in operation position, the control plug is locked and cannot be pulled out.
• The grounding switch can only be closed when the handcart is in the test/isolated position or removed (mechanical interlock)
• When the grounding switch is closed, the handcart cannot move from the test/isolation position to the operating position (mechanical interlock)