Patent ID: 8023235

Claim:
An electrical fault detection device for use in a branch of a power circuit, comprising: an AC line current sensor for monitoring the AC current in an electrical distribution line comprising a primary line and neutral line and carrying an AC power signal the AC line current sensor generating a representative signal proportional to the load current delivered to at least one branch of a power circuit; a line high-frequency sensor coupled to the electrical distribution line for detecting and outputting a broadband high-frequency component of the AC power signal; a differential current sensor coupled to the primary and neutral lines of the electrical distribution line for monitoring the net current between the primary line and neutral line, comparing the net current with the AC load current signal and generating a signal that indicates whether the net line-to-neutral current is inconsistent with a load current by a predetermined acceptable amount; a ground fault current sensor for detecting a current imbalance between the primary and neutral lines of the electrical distribution line; a signal conditioner in electrical signal communication with the AC current line current sensor, the line high frequency sensor, the differential current sensor and the ground fault current sensor and adapted to generate a signal indicative of the load current associated with a branch of the power circuit; a sampling circuit for sampling the signal outputted by the signal conditioner and generating a sampled signal; and a processing resource for processing the sampled signal, the processing resource having stored therein data representing a plurality of time-versus-current curves that define a plurality of regions in which tripping may or may not occur, wherein at least one region has time data and current data that define a time duration for a particular current magnitude for which no tripping will occur, and wherein at least one other region has time data and current data that define a time duration for a particular current magnitude for which tripping will occur, the processing resource processing the sampled signal to (i) provide processed time data and current data, (ii) determine the region to which the processed time data and current data correspond, and (iii) generating a signal to initiate tripping if the sampled signal yields time data and current data that corresponds to a region for which tripping must occur.