A fault-arc identification unit for an electric circuit, includes at least one voltage sensor, for the periodic determination of electric voltage values; and at least one current sensor, for the periodic determination of electric current variables of the circuit. Both sensors are connected to an evaluation unit, designed such that: electric voltage values are fed to a first fault-arc identification function which carries out a first fault-arc identification based upon a signal profile of the voltage, and emits a first fault-arc identification signal upon a first threshold value being exceeded; electric voltage values and current variables are fed to a second fault-arc identification function which carries out a second fault-arc identification based upon the voltage values and current variables, and emits a second fault-arc identification signal upon a second threshold value being exceeded. The fault-arc identification signals are fed to an inclusive disjunction function, to emit a fault-arc identification signal.