Arc fault detector with circuit interrupter

• US 7,925,458 B2
• Filed: 02/15/2008
• Issued: 04/12/2011
• Est. Priority Date: 10/03/2002
• Status: Expired due to Fees

• Current Assignee: Leviton Manufacturing Company Incorporated
• Original Assignee: Leviton Manufacturing Company Incorporated
• Inventors: Kolker, David, Mernyk, Ross, Bradley, Roger M.
• Primary Examiner(s): Schechter; Andrew
• Assistant Examiner(s): O MALLEY, MARY CATHERINE
• Application Number:
  US12/032,431
• Publication Number:
  US 20080140354A1
• Time in Patent Office: 1,152 Days
• Field of Search: 702/60, 702 64- 66, 702 70- 71, 702/73, 702/124, 702182-183, 702/185, 702/190, 361 2- 5, 361 45- 46, 361 78- 79, 361 85- 87, 361/93.1, 361 935- 936, 324508-509, 324/520, 324/522, 324538-539
• US Class Current: 702/59
• CPC Class Codes: G01R 31/1272 of cable, line or wire insulation, e.g. using partial discharge measurements locating faults in cables G01R31/083
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: H02H 1/0015 Using arc detectors
• CPC Class Codes: H02H 3/162 for ac systems
• CPC Class Codes: H02H 3/334 with means to produce an artificial unbalance for other protection or monitoring reasons or remote control H02H3/338 takes precedence
• CPC Class Codes: H02H 3/44 responsive to the rate of change of electrical quantities

Abstract

A method and apparatus are provided for detecting the occurrence of arcing of a conductor by monitoring the current on an AC power line.

Claims

1. A method in an arc fault detecting device capable of being electrically connected to an electrical wiring system between line side phase and neutral conductors and load side phase and neutral conductors, said method detecting the occurrence of arcing of a conductor by monitoring the current on an AC power line, said method comprising:

detecting current in said conductor of the electrical wiring system and generating a signal representative of the detected current;

generating at least one modified signal which represents the filtered or unfiltered current detected in the conductor; and

receiving the at least one modified signal by a controller and performing the following by the controller;

generating a SINE signal having half cycles and zero crossings from a raw input signal, or a signal from a finite impulse response (FIR) filter, or a signal from an infinite impulse response (IIR) filter;

comparing the generated SINE signal with the at least one signals generated from the signal modifying means to generate a DELTA signal;

analyzing the DELTA signal for at least one characteristic representative of the occurrence of an arc; and

generating an output signal upon detection of the at least one characteristic representative of the occurrence of an arc,

wherein the step of detecting current provides for the use of a current transformer,

wherein the step of generating at least one modified signal provides a CURRENT signal representative of the current in the line,

wherein the CURRENT signal is used by the controller to generate the SINE signal, and

wherein the CURRENT signal is fed to a multipoint running finite impulse response filter to smooth the signal prior to being used to generate the SINE signal.

2. The method according to claim 1, wherein the CURRENT signal is fed to an infinite impulse response (IIR) filter to smooth the signal prior to being used to generate the SINE signal.

3. The method according to claim 1, wherein the step of generating at least one modified signal for generating the CURRENT signal provides for the use of a programmable gain amplifier controlled by the controller which scales the output signal to one of a number of scales.

4. The method according to claim 3, comprising a voltage follower located between the transformer and the programmable gain amplifier, and a low pass filter located between the programmable gain amplifier and the controller, wherein the programmable gain amplifier and the low pass filter operate as a D/A converter for generating the CURRENT signal.

5. The method according to claim 1, wherein the step of generating at least one modified signal provides negative and positive di/dt signals of the detected current in the line.

6. The method according to claim 5, wherein the step of generating at least one modified signal provides a signal of the high frequency noise on the line.

7. The method according to claim 1, wherein either the phase or neutral conductor is coupled to the current transformer.

8. The method according to claim 1, further comprising:

detecting a ground fault between the conductors; and

electrically disconnecting the load side phase and neutral conductors from the line side phase and neutral conductors based on the detection of the ground fault.

9. The method according to claim 1, wherein the controller is selected from the group consisting of a micro-controller, a microprocessor, an integrated circuit chip, a processor, and a CPU.

10. A method in an arc fault detecting device capable of being electrically connected to an electrical wiring system between line side phase and neutral conductors and load side phase and neutral conductors, said method detecting the occurrence of arcing of a conductor by monitoring the current on an AC power line, said method comprising:

detecting current in said conductor of the electrical wiring system and generating a signal representative of the detected current;

generating a CURRENT signal which represents the filtered or unfiltered current detected in the conductor; and

receiving the CURRENT signal by a controller and performing the following by the controller;

generating a SINE signal having half cycles and zero crossings from a raw input signal, or a signal from a finite impulse response (FIR) filter, or a signal from an infinite impulse response (IIR) filter, when generating the SINE signal,

locates a starting CURRENT zero crossing,

finds the average of following half cycles of the CURRENT signal,

finds a peak of the same polarity as the average in that half cycle,

multiplies the peak height by the CURRENT at that point,

assumes that real zero crossings are exactly 1/240 second on either side of the peak, and

lockouts ¼

cycle from the leading zero crossing when advancing to next zero crossing,

subtracts the CURRENT signal from the generated SINE signal and divides the result by the SINE signal to obtain a DELTA signal,

analyzes the DELTA signal for at least one characteristic representative of the occurrence of an arc, and

generates an output signal upon detection of the at least one characteristic representative of the occurrence of an arc.

11. The method according to claim 10, wherein the controller analyzes the DELTA signal, continuously, a half cycle at a time to identifying arcing by detecting, in a half cycle, two peaks.

12. The method according to claim 11, wherein the controller further analyzes the DELTA signal for the occurrence of a second peak that is lower than the first peak to further identify arcing.

13. The method according to claim 12, wherein the controller still further analyzes the DELTA signal to obtain a further indication of arcing when a half cycle containing two peaks surrounds a period of one or more half cycles during low current flow.

14. The method according to claim 10, further comprising:

detecting a ground fault between the conductors; and

electrically disconnecting the load side phase and neutral conductors from the line side phase and neutral conductors based on the detection of the ground fault.

15. The method according to claim 10, wherein the controller is selected from the group consisting of a micro-controller, a microprocessor, an integrated circuit chip, a processor, and a CPU.

16. An arc fault detecting device electrically connected to an electrical wiring system between a line conductor and load conductor, said device comprising:

at least one transformer adapted to generate a voltage based on a current present on the line conductor;

a comparator configured to generate at least one signal based on the voltage generated by the transformer;

a first path configured to modify the at least one signal to represent the current present on the line conductor;

a second path configured to modify the at least one signal to represent at least one of a positive step change in the current as a function of time and a negative step change in the current as a function of time;

a third path configured to modify the at least one signal to represent a noise signal on the line conductor; and

a controller electrically connected to the comparator by at least one of the first, second, and third path and configured to compare the at least one modified signal to a first waveform generated by the controller, wherein the controller generates a second waveform based on the comparison between the at least one modified signal and the first waveform to cause a switch to electrically disconnect the load conductor from the line conductor based on the second waveform, wherein the first path includes a programmable gain amplifier configured to output the at least one signal from the comparator to a low pass filter adapted to remove high frequency noise from the at least one signal to provide the at least one modified signal to the controller.

17. The arc fault detecting device according to claim 16, wherein the comparator is a operational amplifier.

18. The arc fault detecting device according to claim 16, wherein the switch is a silicon-controlled rectifier.

19. The arc fault detecting device according to claim 16, wherein the second path includes a differentiator configured to output the at least one signal from the comparator to at least one threshold comparator to remove noise from the at least one signal, the at least one threshold comparator configured to output the at least one signal to a peak detector configured to provide a negative threshold output of the current and a positive threshold output of the current to the controller.

20. The arc fault detecting device according to claim 16, wherein the third path includes a band pass filter adapted to remove low frequency noise from the at least one signal and configured to output the at least one signal from the comparator to an integrator configured to provide a voltage representative of the high frequency noise of the at least one signal to the controller.

21. The arc fault detecting device according to claim 16, further comprising a ground fault circuit interrupter configured to cause the switch to electrically disconnect the load conductor from the line conductor based on a detection of a ground fault by the ground fault circuit interrupter.

22. The arc fault detecting device according to claim 16, wherein the first waveform generated by the controller is based on at least one input signal from the at least one transformer.

23. The arc fault detecting device according to claim 16, wherein the comparison between the at least one modified signal and the first waveform represents an absolute difference therebetween.

24. The arc fault detecting device according to claim 16, wherein the controller is selected from the group consisting of a micro-controller, a microprocessor, an integrated circuit chip, a processor, and a CPU.

25. A method of detecting an arc fault between a line conductor electrically connected to a load conductor, comprising:

detecting a current present on the line conductor;

generating at least one signal based on the detected current;

modifying the at least one signal to represent the detected current;

generating a first waveform based on one of an unfiltered signal and a filtered signal;

comparing the first waveform with the at least one modified signal;

generating a second waveform based on the comparison between the first waveform and the at least one modified signal;

detecting at least one condition of the second waveform representative of the arc fault; and

generating an output signal to electrically disconnect the load conductor from the line conductor based on the detection of the at least one condition, wherein the modifying step further comprises filtering the at least one signal via at least one of an infinite impulse response filter and a multipoint running finite impulse response filter prior to generating the first waveform using a microcontroller.

26. A method of detecting an arc fault between a line conductor electrically connected to a load conductor according to claim 25, wherein the output signal is generated by a controller based on the first waveform.

27. A method of detecting an arc fault between a line conductor electrically connected to a load conductor according to claim 25, wherein the at least one modified signal represents one of a positive step change in the current and a negative step change in the current.

28. A method of detecting an arc fault between a line conductor electrically connected to a load conductor according to claim 25, further comprising generating an output signal to electrically disconnect the load conductor from the line conductor based on the detection of a ground fault.

29. A method of detecting an arc fault between a line conductor electrically connected to a load conductor according to claim 25, wherein the comparison of the generating step is an absolute difference between the first waveform and the at least one modified signal.

30. A method of detecting an arc fault between a line conductor electrically connected to a load conductor according to claim 25, further comprising:

detecting a ground fault between the conductors; and

electrically disconnecting the load conductor from the line conductor based on the detected ground fault.

31. A method of detecting an arc fault between a line conductor electrically connected to a load conductor according to claim 25, wherein the microcontroller generates the output signal to electrically disconnect the load conductor from the line conductor based on the detection of the at least one condition.