Calculation of overpressure in the surroundings of fault arcs in SF6-air mixtures

Because of the excellent insulating and quenching properties of SF₆ it is used e.g. in compact switchgear installations. In the case of internal arcing, hot SF₆ escapes from the faulty compartment carrying energy into the air surroundings, which causes overpressure within the switchgear and the switchgear building. During this process the SF₆ concentration varies continuously. In order to calculate the pressure rise the gas properties of the varying SF₆-air mixture must be included in the calculation procedure. A calculation model has been developed, which considers the changing gas properties according to the varying SF₆ concentration. The model is evaluated by comparing experimental with calculation results.