Arcing fault detection system

• US 5,682,101 A
• Filed: 02/13/1996
• Issued: 10/28/1997
• Est. Priority Date: 03/13/1995
• Status: Expired due to Term

• Current Assignee: Square D Company (Schneider Electric SE)
• Original Assignee: Square D Company (Schneider Electric SE)
• Inventors: Strader, Walter H., Brooks, Stanley J., Dickens, James W.
• Primary Examiner(s): Arana, Louis M.
• Application Number:
  US08/600,512
• Time in Patent Office: 623 Days
• Field of Search: 324/520, 324/521, 324/522, 324/509, 324/529, 324/530, 324/532, 324/535, 324/536, 324/544
• US Class Current: 324/536
• CPC Class Codes: H01H 2083/201 the other abnormal electrical condition being an arc fault
• CPC Class Codes: H01H 71/125 characterised by sensing elements, e.g. current transformers for differential protection H01H83/144
• CPC Class Codes: H02H 1/0015 Using arc detectors
• CPC Class Codes: H02H 1/06 Arrangements for supplying operative power power supply arrangements in general G05F, H02M
• CPC Class Codes: H02H 3/44 responsive to the rate of change of electrical quantities

Abstract

A system to detect arcing faults in an electrical distribution system with a line conductor connected to a utility power transformer. The system monitors the rate of change of electrical current in the line conductor and produces a signal which represents the rate of change. The system produces a pulse each time the rate-of-change signal exceeds a selected threshold, filters the rate-of-change signal and/or the pulses to substantially eliminate a signal or pulse which represents changes in the electrical current outside a selected frequency range, monitors the remaining pulses to detect when the number of pulses that occur within a selected time interval exceeds a predetermined threshold, and generates an arc-fault-detection signal in response to the occurrence of a number of pulses which exceed the threshold within the selected time interval.

Claims

1. A method of detecting arcing faults in an electrical distribution system that includes a line conductor connected to a utility power transformer, said method comprising:

monitoring the rate of change of electrical current in the line conductor and producing a signal representing the rate of change,

producing a pulse each time the rate-of-change signal exceeds a selected threshold,

filtering at least one of said rate-of-change signal and said pulses to substantially eliminate signals or pulses representing changes in said electrical current outside a selected frequency range while preserving unfiltered signals or pulses representing changes in said electrical current within said selected frequency range,

producing a signal representing a number of said unfiltered signals or pulses occurring within a selected time interval; and

generating an arc-fault-detection signal in response to said signal representing said number of unfiltered signals or pulses occurring within a selected time interval exceeding a trip threshold level.

2. The method of claim 1 wherein said step of producing a pulse each time the rate-of-change signal exceeds a selected threshold includes a comparison of the amplitude of the rate-of-change signal to a predetermined reference signal.

3. The method of claim 1 wherein said filtering step comprises filtering said rate-of-change signal to substantially eliminate signals representing a rate of change outside the range from about 60 Hz to about1 MHz.