An arc fault in switchgear is a failure with enormous effects and a high hazard potential to persons in its vicinity. Therefore the switchgear manufacturers intensively look for possibilities to minimize this hazard potential. The ways used in industrial practice can be separated in to two basic directions, the active and the passive protection. The active protection tries to exclude the possibilities for an arc fault to occur as far as possible. The passive protection limits the effects of an existing arc fault. However both basic directions are associated with specific drawbacks. For safety-relevant and economic reasons a protection concept would be useful, which accepts the realistic possibility of an arc fault, but which reacts before a high-current and destruction-intensive arc fault exists. This is the objective of the "preventive arc fault protection".