Patent ID: 6362628
Filing Date: 2002-03-26
Classification: G01R,H02H

Abstract:
An arc fault detecting device for protecting electric power lines, the device comprising:a sensor coupled to a power line for detecting broad band arc noise caused by an arc fault in the electric power lines; a pulse generator connected to the sensor for generating an arc start pulse at the start of the broad band arc noise; a power line zero cross detector generating a zero cross pulse; a time interval generator connected to the zero cross detector which is triggered by the start of the zero cross pulse and which is reset by a transition of the arc start pulse, and which generates a time interval proportional to a delay time between the zero cross and the start of an arc; a memory for storing the time interval; a comparator connected to the time interval generator and the memory for comparing the delay time of a present arc start pulse with the delay time of a previous arc start pulse, wherein the delay times are of random duration corresponding to the broad band arc noise generated by the arc fault in the electric power lines; a counter connected to the comparator, the counter being incremented if the difference between the present delay time and the previous delay time is greater than a first predetermined value; and a second comparator for generating an arc fault detection signal when the counter reaches a second predetermined value.