Patent ID: 8717725

Claim:
An intelligent electronic device (IED) for providing restricted earth fault protection comprising: a phase angle comparator configured to receive an input comprising a vector representing electrical conditions associated with a plurality of phases of a mufti-phase electrical power delivery system and a vector representing electrical conditions associated with a neutral line of the mufti-phase electrical power delivery system, to determine a phase angle difference between the input and a phase angle reference, and to selectively generate a phase angle comparator fault indicator based on the phase angle difference with respect to a phase angle deviation threshold; an amplitude comparator configured to receive the input and to selectively generate an amplitude comparator fault indicator based on the input with respect to an amplitude threshold; and selection logic configured to generate a selection logic output corresponding to one of the phase angle comparator fault indicator and the amplitude comparator fault indicator, to the exclusion of the other, based on a selection logic threshold, and the input from the mufti-phase electrical power delivery system.