In turn, the short-circuiting switch 12b associated with the fault arc A is closed to quench the fault arc A. Then, one of the circuit breakers 13a, 13b or 13e cuts off the faulty section of the electrical appliance 9a as a consequence of the excessive current flowing over said circuit breakers 13a, 13b or 13e. By providing different current trigger levels for the circuit breakers 13a . . . 13h, cutting off can take place in a predetermined way. Usually, care is taken, that small sections 11a, 11b of the electrical appliance 9a are switched off in case of an arc fault. In FIG. 1 this means, that the circuit breaker 13b or 13e shall open in case of the fault arc A.

In the end, the hazardous situation is cleared. However, clearing takes some time and the fault arc A may cause serious damage to the electrical appliance 9a or injury of personnel in the electrical appliance 9a even in this short time period of about 30-50 ms, which is necessary to clear the hazardous situation.