Arc fault detector with circuit interrupter

• US 5,963,406 A
• Filed: 12/19/1997
• Issued: 10/05/1999
• Est. Priority Date: 12/19/1997
• Status: Expired due to Term

• Current Assignee: Leviton Manufacturing Company Incorporated
• Original Assignee: Leviton Manufacturing Company Incorporated
• Inventors: Bradley, Roger M., Zaretsky, Albert, Rose, William J., Pearse, James N., Neiger, Benjamin B.
• Primary Examiner(s): SHERRY, MICHAEL JUDE
• Application Number:
  US08/994,772
• Time in Patent Office: 655 Days
• Field of Search: 361/42-50, 361/69, 361/93, 361/94, 361/102
• US Class Current: 361/42
• CPC Class Codes: H01H 2300/03 Application domotique, e.g. for house automation, bus connected switches, sensors, loads or intelligent wiring
• CPC Class Codes: H02H 1/0015 Using arc detectors
• CPC Class Codes: H02H 3/331 responsive to earthing of the neutral conductor H02H3/338 takes precedence
• CPC Class Codes: H02H 3/335 the main function being self testing of the device
• CPC Class Codes: Y02B 70/30 Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
• CPC Class Codes: Y04S 20/20 End-user application control systems

Abstract

An arc fault detector embodied as both a stand alone device and in combination with a circuit interrupting device such as a ground fault circuit interrupter (GFCI) functions to provide protection from potentially dangerous arc fault conditions. The device utilizes line side and load side pickup coils to permit distinguishing between arc faults occurring on the line side and the load side of the device. The arc fault circuit interrupter (AFCI) circuitry portion of the device shares components from the GFCI circuitry portion as an integral part of its functionality. The AFCI utilizes the electromechanical power carrying, portion of the GFCI, including the AC line disconnect circuitry, the power supply and the physical housing. In addition, the AFCI employs quantitative detection using variable gain control in combination with either a load disconnect or audible/visual alarm indication. The device also includes a timer circuit, which permits the user to temporarily inhibit or disable the arc detection, and selective frequency filtering permitting arc detection in the presence of power line carrier communications. In addition, the device includes communication means to permit the device to communicate the occurrence and location of an arc fault to a centralized monitoring station.

Claims

1. An arc fault circuit interrupter (AFCI) device electrically connected to an electrical wiring system between a source of electrical power including line side phase and neutral conductors and a load including phase and neutral conductors, said device comprising:

first arc fault circuit means for detecting arc faults occurring on said line side of said electrical wiring system and outputting an arc fault indicative signal of a line side arc fault;

second arc fault circuit means for detecting arc faults occurring on said load side of said electrical wiring system and outputting an arc fault indicative signal of a load side arc fault;

means responsive to said arc fault indicative signals for distinguishing between arc faults occurring on said line side and said load side of said device, and for generating an arc fault trigger signal in response to the detection of an arc fault at least for arc faults occurring on said load side;

trigger means for generating a switching signal upon receipt of said arc fault trigger signal; and

switching means electrically connected in series between said line side phase and neutral conductors and said load side phase and neutral conductors, said switching means for disconnecting said source of electrical power to said load side phase and neutral conductors in response to said switching signal.

2. The device according to claim 1, further comprising means for interrupting the flow of current to a load electrically connected to said device in response to the detection of a fault other than an arc fault.

3. The device according to claim 2, wherein said interrupting means comprises ground fault circuit interrupter (GFCI) means for detecting the occurrence of a ground fault between said phase conductor and ground or between said neutral conductor and ground, said ground fault circuit means being operative to generate a ground fault trigger signal in response to the detection of said ground fault.

4. The device according to claim 1, wherein said first arc fault circuit means comprises line pickup means located on said line side of said device for detecting arcing occurring on said electrical wiring system.

5. The device according to claim 4, wherein said line pickup means comprises a toroidal ferrite transformer.

6. The device according to claim 4, wherein said line pickup means comprises a resonance damping network for enhancing broadband frequency pickup.

7. The device according to claim 4, wherein said line pickup means comprises capacitive coupling means for coupling said line side of said device to said electrical wiring system.

8. The device according to claim 1, wherein said second arc fault means comprises load pickup means located on said load side of said device for detecting arcing occurring on said electrical wiring system.

9. The device according to claim 8, wherein said load pickup means comprises a toroidal ferrite transformer.

10. The device according to claim 8, wherein said load pickup means comprises a resonance damping network for enhancing broadband frequency pickup.

11. The device according to claim 8, wherein said load pickup means comprises capacitive coupling means for coupling said load side of said device to said electrical wiring system.

12. The device according to claim 1, wherein said first arc fault means comprises line side impedance means for enhancing the high frequency line impedance on said line side of said device.

13. The device according to claim 12, wherein said line side impedance means comprises a ferrite bead.

14. The device according to claim 1, wherein said second arc fault means comprises load side impedance means for enhancing the high frequency line impedance on said load side of said device.

15. The device according to claim 14, wherein said load side impedance means comprises a ferrite bead.

16. The device according to claim 1, wherein said first arc fault circuit means comprises a line side transformer through which either said line side phase or neutral conductor passes through, said transformer being operative to generate a current proportional to the current flowing through said line side phase or neutral conductor.

17. The device according to claim 1, wherein said second arc fault circuit means comprises a load side transformer through which either said load side phase or neutral conductor passes through, said transformer being operative to generate a current proportional to the current flowing through said load side phase or neutral conductor.

18. The device according to claim 1 further comprising means for partially disabling arc detection for a finite period of time, the disabling of arc detection providing a user with the ability use an electrical device exhibiting arcing.

19. The device according to claim 1 further comprising communication means for communicating the generation of said switching signal.

20. The device according to claim 1 further comprising means for receiving an external disable command and disabling arc detection in accordance therewith.

21. The device according to claim 1 further comprising means for a user to manually turn arc detection on and off.

22. The device according to claim 1 further comprising means for disabling arc detection during daylight hours and enabling arc detection during night hours.

23. The device according to claim 1 further comprising means for disabling and enabling arc detection in accordance with signals received from a remote infrared (IR) transmitter.

24. An arc fault detecting circuit operatively coupled to a line side and a load side of at least one conductor of an electrical wiring system, comprising:

line detection means for sensing high frequency signals on said line side of said at least one conductor;

load detection means for sensing high frequency signals on said load side of said at least one conductor;

line circuit means for generating a line output signal in accordance with the output of said line detection means;

load circuit means for generating a load output signal in accordance with the output of said load detection means; and

arc detect means for generating said arc fault trigger signal when said load output signal is greater than said line output signal.

25. The device according to claim 24, further comprising audible alarm means for sounding an audible alarm when said line output signal is greater than said load output signal.

26. An arc fault circuit interrupter (AFCI) device electrically connected to an electrical wiring system between a source of electrical power including line side phase and neutral conductors and load including phase and neutral conductors, said device comprising:

arc fault circuit means for detecting arc faults occurring on said electrical wiring system, said arc fault circuit means for distinguishing between arc faults occurring on said line side and said load side of said device, said arc fault circuit means operative to generate an arc fault trigger signal in response to the detection of an arc fault;

trigger means for generating a switching signal upon receipt of said arc fault trigger signal;

switching means electrically connected in series between said line side phase and neutral conductors and said load side phase and neutral conductors, said switching means for disconnecting said source of electrical power to said load side phase and neutral conductors in response to said switching signal; and

timer means for partially disabling arc detection for a finite period of time, the disabling of arc detection providing a user with the ability to use an electrical device exhibiting arcing, said timer means enabling arc detection after use of said electrical device has been discontinued.

28. The device according to claims 26 or 27, further comprising means for interrupting the flow of current to a load electrically connected to said device in response to detection of a fault other than an arc fault.

29. The device according to claim 28, wherein said interrupting means comprises ground fault circuit interrupter (GFCI) means for detecting the occurrence of a ground fault between said phase conductor and ground or between said neutral conductor and ground, said ground fault circuit means being operative to generate a ground fault trigger signal in response to the detection of said ground fault.

32. The device according to claim 26 further comprising means for partially disabling arc detection for a finite period of time, the disabling of arc detection providing a user with the ability use an electrical device exhibiting arcing, said timer means enabling arc detection after use of said electrical device has been discontinued.

33. The device according to claims 26 or 27, further comprising communication means for communicating the generation of said switching signal.

34. The device according to claims 26 or 27, further comprising means for receiving an external disable command and disabling arc detection in accordance therewith.

35. The device according to claims 26 or 27, further comprising means for a user to manually turn arc detection on and off.

36. The device according to claims 26 or 27, further comprising means for disabling arc detection during daylight hours and enabling arc detection during night hours.

37. The device according to claims 26 or 27, further comprising means for disabling and enabling arc detection in accordance with signals received from a remote infrared (IR) transmitter.

27. An arc fault circuit interrupter (AFCI) device electrically connected to an electrical wiring system between a source of electrical power including line side phase and neutral conductors and a load side including phase and neutral conductors, said device comprising:

line detection means for sensing high frequency signals on said electrical wiring system on the line side of said device;

load detection means for sensing high frequency signals on said electrical wiring system on the load side of said device;

line circuit means for generating a line output signal in accordance with the output of said line detection means, said line output signal being indicative of an arc fault on said line side on said electrical wiring system;

load circuit means for generating a load output signal in accordance with the output of said load detection means, said load output signal being indicative of an arc fault on said load side on said electrical wiring system;

arc detect means for generating an arc fault trigger signal upon the occurrence of a load side arc fault;

trigger means for generating a switching signal upon receipt of said arc fault trigger signal; and

switching means electrically connected in series between said line side phase and neutral conductors and said load side phase and neutral conductors, said switching means for disconnecting said source of electrical power to said load side phase and neutral conductors in response to said switching signal.

30. The device according to claim 27, wherein said arc detect means generates said arc fault trigger signal when said load output signal is greater than said line output signal.

31. The device according to claim 27, further comprising means for generating an alarm signal when said line output signal is greater than said load output signal.

38. The device according to claim 27 further comprising means for partially disabling arc detection for a finite period of time, the disabling of arc detection providing a user with the ability use an electrical device exhibiting arcing.

39. In an arc fault circuit interrupter (AFCI) device connected to an electrical wiring system via line side phase and neutral conductors and load side phase and neutral conductors, a method of detecting arc faults, comprising the steps of:

detecting high frequency signals on said line side of said device and processing said high frequency signals to generate a line output signal if said high frequency signals include an arc fault;

detecting high frequency signals on said load side of said device and processing said high frequency signals to generate a load output signal if said high frequency signals include an arc fault; and

disconnecting said source of electrical power from at least one of said load side phase and neutral conductors when said load output signal exceeds said line output signal.

41. The method according to claims 39 or 40, further comprising the step of partially disabling arc detection for a finite period of time, the disabling of arc detection providing a user with the ability use an electrical device exhibiting arcing, and enabling arc detection after use of said electrical device has been discontinued.

42. The method according to claims 39 or 40, further comprising the step of communicating the disconnection of said source of electrical power from said load.

43. The method according to claims 39 or 40, further comprising the step of receiving a disable command and disabling arc detection in accordance therewith.

44. The method according to claims 39 or 40, further comprising the step of providing the ability for a user to manually turn arc detection on and off.

45. The method according to claims 39 or 40, further comprising the step of disabling arc detection during daylight hours and enabling arc detection during night hours.

46. The method according to claims 39 or 40, further comprising the step of disabling and enabling arc detection in accordance with signals received from a remote infrared (IR) transmitter.

40. In an arc fault circuit interrupter (AFCI) device connected to an electrical wiring system via line side phase and neutral conductors and load side phase and neutral conductors, a method of detecting arc faults and ground faults, comprising the steps of:

detecting high frequency signals on said line side of said device and processing said high frequency signals to generate a line output signal if said high frequency signals include an arc fault;

detecting high frequency signals on said load side of said device and processing said high frequency signals to generate a load output signal if said high frequency signals include an arc fault;

detecting ground faults associated with said conductors, and generating a ground fault trigger signal in response to the detection of a ground fault;

disconnecting said source of electrical power from at least one of said load side phase and neutral conductors when said load output signal exceeds said line output signal or in response to said ground fault trigger signal.

47. An arc fault circuit interrupter device for installation in electrical wiring systems having phase and neutral conductors, said device being capable of being electrically connected at a line side to a source of electrical power and at a load side to at least one load, said device comprising:

a first arc fault detector operatively associated with at least one of the line side phase and neutral conductors to detect arc faults occurring on the line side of the electrical wiring system and to output a first arc fault signal indicative of a line side arc fault;

a second arc fault detector operatively associated with at least one of the load side phase and neutral conductors to detect arc faults occurring on the load side of the device and to output a second arc fault signal indicative of a load side arc fault;

a signal processing circuit coupled to the outputs of the first and second arc fault detectors, the processing circuitry being responsive to at least one of said first and second arc fault signals to distinguish between arc faults occurring on the line side and the load side of the device, and to output an arc fault trigger signal at least when an arc fault occurs on said load side of the device;

a trigger circuit coupled to the output of the signal processing circuit, the trigger circuit being responsive to the arc fault trigger signal so as to output a switching signal upon receipt of said arc fault trigger signal; and

a switch electrically connected in series between at least one of the line and load side phase conductors and the line and load side neutral conductors, and responsive to said switching signal from the trigger circuit, such that said switch interrupts power between the line side and load side of said device in response to said switching signal.

48. The device according to claim 47 further comprising a fault detector operatively associated with at least one of the line and phase conductors to detect faults other than arc faults and to output a trigger signal to said trigger circuit, such that upon detection of a fault other than an arc fault said trigger circuit causes said switch to interrupt power between the line and load side of the device.

49. The device according to claim 48, wherein said fault detector comprises a ground fault circuit interrupter that detects the occurrence of a ground fault.

50. The device according to claim 47, wherein said first arc fault detector comprises a line pickup associated with at least one of the line side phase and neutral conductors.

51. The device according to claim 50, wherein said line pickup comprises a toroidal ferrite transformer.

52. The device according to claim 50, wherein said line pickup comprises a resonance damping network.

53. The device according to claim 50, wherein said line pickup comprises a capacitive coupling network.

54. The device according to claim 47, wherein said second arc fault detector comprises load pickup associated with at least one of the load side phase and neutral conductors.

55. The device according to claim 54, wherein said load pickup comprises a toroidal ferrite transformer.

56. The device according to claim 54, wherein said load pickup comprises a resonance damping network.

57. The device according to claim 54, wherein said load pickup comprises a capacitive coupling network.

58. The device according to claim 47, wherein said first arc fault detector comprises a line side transformer through which at least one of said line side phase and neutral conductors pass through, said line side transformer being operative to generate a current proportional to the current flowing through said at one of said line side phase and neutral conductors.

59. The device according to claim 47, wherein said second arc fault detector means comprises a load side transformer through at least one of said line side phase and neutral conductors pass through, said load side transformer being operative to generate a current proportional to the current flowing through said at least one of said load side phase and neutral conductors.

60. An arc fault detecting circuit operatively coupled to a line side and a load side of at least one conductor of an electrical wiring system, comprising:

a line sensor operatively associated with the at least one conductor of the electrical wiring system at the line side, which senses high frequency signals on the at least one conductor at the line side and outputs a line arc fault sense signal;

a line output signal generator coupled to the output of said line sensor, and responsive to said line arc fault sense signal to generate a line output signal if said sensed high frequency signal includes an arc fault;

a load sensor operatively associated with the at least one conductor of the electrical wiring system at the load side, which senses high frequency signals on the at least one conductor at the load side and outputs a load arc fault sense signal;

a load output signal generator coupled to the output of said load sensor, and responsive to said load arc fault sense signal to generate a load output signal if said sensed high frequency signal includes an arc fault; and

an arc detector coupled to said line and load output signal generators which generates said arc fault trigger signal when said load output signal is greater than said line output signal.