Patent ID: 7847562

Claim:
A resistive fault condition detector for conducting at least one test of a circuit comprising a live conductor, a neutral conductor, a ground conductor, and a load, the detector comprising: means for determining changes in current through the load during said at least one test; means for measuring changes in first and second voltages respectively between the live and neutral conductors and between the neutral and ground conductors during said at least one test, said changes in said first and second voltages corresponding to said changes in said current respectively; means for calculating sets of apparent source impedances for the live and neutral conductors respectively based on said changes in said current and said corresponding measured changes in said first and second voltages respectively; means for calculating an estimated source impedance for each of said live and neutral conductors respectively for said at least one test, the estimated source impedances for the live and neutral conductors respectively for each said set being deemed to be equal to the modes thereof if a proportion of the apparent source impedances matching the mode in each said respective set is greater than a predetermined proportion, each said set in which the proportion of the apparent source impedances matching the mode is less than the predetermined proportion being discarded; means for determining if any of the respective estimated source impedances for the live conductor and the neutral conductor exceeds a respective predetermined threshold value therefor, wherein at least one resistive fault condition in the circuit is detected if one of the predetermined threshold values is exceeded; means for generating an alarm signal upon detection of said at least one resistive fault condition; and means for disconnecting the live conductor upon receipt thereby of the alarm signal.