Arc fault detector with a first electric line and at least a first sensor adapted for monitoring an electric current and/or voltage spectrum in the first electric line and outputting a measurement signal, further comprising a signal-pattern-analysing-unit adapted to compare the measurement signal with at least a first predefined arc pattern, and to output a first arc-detection-signal on a first output in case the measurement signal matches the arc pattern, wherein the current and/or voltage in the electric line are evaluated in parallel in at least three different units (4, 6, 8), and wherein the arc fault detector further comprises: - a slew-rate-detection-unit adapted to determine a slew rate of the electric current in the first electric line, comparing the determined slew rate with a threshold slew rate, and outputting a slew-rate-detection-signal on a second output in case the determined slew rate is higher than the threshold slew rate, characterised in that the measurement signal is a broadband measurement signal with a bandwidth from at least 10 Hz to 10 MHz, especially a bandwidth from 1 Hz to 20 MHz, and in that the arc fault detector further comprises: - an envelope-step-detection-unit adapted to determine a change of an envelope-value of at least a predefined frequency band of the broadband measurement signal within a predefined timespan, the envelope-step-detection-unit contains a band-pass-filter arranged at an input of the envelope-step-detection-unit, the envelope-step-detection-unit comprises an envelope determination unit, the envelope determination unit comprises a rectifier unit coupled to the exit of the band-pass-filter, the exit of the rectifier unit is connected to a unit to detect the maximum values of the rectified signal and further interpolating a curve along the maximum values to build the envelope, the envelope-step-detection-unit comprises a unit to differentiate the envelope curve, the envelope-step-detection-unit being further adapted to output an envelope-step-detection-signal on a third output in case that the determined change is higher than a threshold change, - a first controller-unit connected to the second output and the third output, the first controller-unit being adapted to output a second arc-detection-signal on a fourth output in case the first controller-unit receives the slew-rate detection signal and the frequency-detection-signal within a first predefined detection-time-window, - a second controller-unit connected to the first output and the fourth output, the second controller-unit being adapted to output a trigger signal on a trigger output in case the second controller-unit receives the first arc-detection-signal and the second arc-detection-signal for at least a defined total time within a second predefined detection-time-window. - a slew-rate-detection-unit adapted to determine a slew rate of the electric current in the first electric line, comparing the determined slew rate with a threshold slew rate, and outputting a slew-rate-detection-signal on a second output in case the determined slew rate is higher than the threshold slew rate, characterised in that the measurement signal is a broadband measurement signal with a bandwidth from at least 10 Hz to 10 MHz, especially a bandwidth from 1 Hz to 20 MHz, and in that the arc fault detector further comprises: - an envelope-step-detection-unit adapted to determine a change of an envelope-value of at least a predefined frequency band of the broadband measurement signal within a predefined timespan, the envelope-step-detection-unit contains a band-pass-filter arranged at an input of the envelope-step-detection-unit, the envelope-step-detection-unit comprises an envelope determination unit, the envelope determination unit comprises a rectifier unit coupled to the exit of the band-pass-filter, the exit of the rectifier unit is connected to a unit to detect the maximum values of the rectified signal and further interpolating a curve along the maximum values to build the envelope, the envelope-step-detection-unit comprises a unit to differentiate the envelope curve, the envelope-step-detection-unit being further adapted to output an envelope-step-detection-signal on a third output in case that the determined change is higher than a threshold change, - a first controller-unit connected to the second output and the third output, the first controller-unit being adapted to output a second arc-detection-signal on a fourth output in case the first controller-unit receives the slew-rate detection signal and the frequency-detection-signal within a first predefined detection-time-window, - a second controller-unit connected to the first output and the fourth output, the second controller-unit being adapted to output a trigger signal on a trigger output in case the second controller-unit receives the first arc-detection-signal and the second arc-detection-signal for at least a defined total time within a second predefined detection-time-window.