Patent ID: 6839208
Filing Date: 2005-01-04
Classification: G01R,H02H

Abstract:
1. An arc fault detector for protecting electric power lines, comprising: a sensor coupled to said power lines for detecting broad band arc noise; a di/dt detector connected to said sensor for generating an output pulse having a time width associated with a time during which a pulse of broad band arc noise is above a predetermined threshold; a processor connected to said detector; a power line zero cross detector generating a time reference pulse for said processor; wherein said processor evaluates a width of said di/dt detector output pulse during each half wave following a zero cross pulse and opens a detection window for a first predetermined number of power line half cycles if, during any one power line half cycle, either (a) said width of said output pulse is equal to or exceeds a first predetermined interval, or (b) said width of said output pulse is equal to or exceeds two or more second predetermined intervals; wherein a length of said second predetermined interval is less than a length of said first predetermined interval; and wherein during said open detection window said processor ignores said output pulses for a rejection period lasting a second predetermined number of half cycles at a start of said window.