A method for detecting high impedance faults, including: receiving an input waveform from a circuit; computing a root mean square of the input waveform; fitting a regression line to the root mean squares; computing a deviation between the regression line and the root mean squares; determining whether the deviations are above a threshold; and outputting a value indicating that a fault has occurred in the circuit when the deviation is above the threshold and outputting a value indicating that a fault did not occur in the circuit when the deviation is below the threshold.