Patent ID: 7227729

Claim:
Arc fault detection apparatus, comprising: a power input configured to monitor a power line current; a differential current input sense circuit operative to sense a differential current (di/dt) signal associated with the line current; a differential current characteristics sense circuit operative to detect at least one characteristic of the di/dt signal, wherein the at least one characteristic of the di/dt signal includes a level associated with a plurality of di/dt events, and a variation with time of the plurality of di/dt events over a specified number of cycles of the line current; an absolute current input sense circuit operative to sense an absolute current signal associated with the line current; an absolute current characteristics sense circuit operative to detect at least one characteristic of the absolute current signal, wherein the at least one characteristic of the absolute current signal includes a peak level and an RMS level of the line current; and a processor operative to receive representations of the at least one characteristic of the di/dt signal and the at least one characteristic of the absolute current signal, and to determine whether the characteristics of the di/dt and absolute current signals are indicative of an arc fault based on the level associated with the plurality of di/dt events, the variation with time of the plurality of di/dt events over the specified number of current cycles, and a ratio of the peak level and the RMS level of the line current.