The main feature of this series of switchgear is that it can be flexibly combined according to the required circuit scheme of each unit. In case of failure, the unit can be pulled out in a very short time and replaced with a standby unit for continuous use. The same unit can be interchanged on any cabinet. The unit compartment is provided with a ventilation channel, and a pressure relief device is set on the top of the cabinet to release the high-pressure free gas generated in case of internal failure of the distribution cabinet.