Influence of buffer volumes on pressure rise in switchgear installations due to internal arcing

During internal arcing in gas insulated and metal-enclosed switchgear, overpressure is discharged through relief openings into the switchgear room. At high power input the mechanical strength of the switchgear room (building) can be exceeded. Normally this is avoided by sufficient large relief openings in the walls of the building to the environment. A further possibility is the use of intermediate rooms (volumes between the compartment, where the arc burns, and the switchgear room) as buffer volumes, in which the hot gas of the arc expands first before delivering its energy to the switchgear room. By this procedure a reduction of the pressure in the switchgear room is reachable. Exploratory overpressure calculations are performed in order to find out the efficiency of such a measure in dependence of several parameters like the size of the intermediate volume and relief openings.