Controlled pressure stress on switchgear rooms during internal arc faults

The experience of internal arc testing of modern compact substations with SF₆-insulated medium voltage load break switchgear shows that it is possible to reduce the pressure stress on the switchgear rooms by means of special pressure reducing and cooling elements in the substation. This experience is used to design new medium voltage load break switchgear for installation in older buildings with limited pressure withstand capability. This new switchgear is equipped with an absorber to reduce the pressure stress outside the switchgear and to cool the hot arc gases. The effectiveness of this absorber is shown by internal arc tests at the new switchgear installed in a 20 feet container. The absorber reduces the pressure stress on the substation housing by a factor of 4. By means of special diagram, the test results can be transferred to switchgear rooms of different volume and different pressure relief opening. In this way, it is possible to determine the pressure stress on substation housings when new SF₆-insulated medium voltage load break switchgear is installed in older buildings of limited pressure withstand capability and to ensure a simultaneously high level of personnel safety