Circuit breaker

CIRCUIT BREAKER The invention relates to a circuit breaker for an electrical low voltage circuit. Said circuit breaker has an arc fault detection device function that can ascertain arcing faults in the electrical low voltage circuit and, in the event of an arcing fault limit value being exceeded, can interrupt the electrical low voltage circuit, a residual current breaker function that can ascertain fault currents in the electrical low voltage circuit and, in the event of a fault current limit value being exceeded, can interrupt the electrical low voltage circuit, and an electrical power supply for the arc fault detection device function and the residual current breaker function. The circuit breaker is configured such that the voltage in the low voltage circuit is ascertained and the arc fault detection device function is disengaged in the event of a first limit value of the voltage not being reached.