Arc detection using load recognition, harmonic content and broadband noise

• US 20030072113A1
• Filed: 03/27/2002
• Published: 04/17/2003
• Est. Priority Date: 10/17/2001
• Status: Active Grant

• Current Assignee: Square D Company (Schneider Electric SE)
• Original Assignee: Square D Company (Schneider Electric SE)
• Inventors: Scott, Gary W., Wong, Kon B.
• Granted Patent: US 7,068,480 B2
• Time in Patent Office: Days
• US Class Current: 361/5
• CPC Class Codes: G01R 31/14 Circuits therefor , e.g. for generating test voltages, sensing circuits G01R31/1209 - G01R31/1227 take precedence; for testing switches G01R31/327
• CPC Class Codes: H02H 1/0015 Using arc detectors
• CPC Class Codes: H02H 3/44 responsive to the rate of change of electrical quantities

Abstract

A method of determining whether arcing is present in an electrical circuit includes sensing a change in current in the circuit and developing a corresponding input signal, analyzing the input signal to determine the presence of broadband noise in a predetermined range of frequencies, and producing a corresponding output signal, and processing the input signal and the output signal in a predetermined fashion to determine whether an arcing fault is present in the circuit. The processing includes determining a type of load connected to the electrical circuit, based at least in part upon the input signal and the output signal.

Claims

1. A method of determining whether arcing is present in an electrical circuit comprising:

sensing a change in current in said circuit and developing a corresponding input signal;

analyzing said input signal to determine the presence of broadband noise in a predetermined range of frequencies, and producing a corresponding output signal; and

processing said input signal and said output signal in a predetermined fashion to determine whether an arcing fault is present in said circuit;

said processing including determining a type of load connected to said electrical circuit, based at least in part upon said input signal and said output signal.

2. The method of claim 1 and further including producing a trip signal in response to a determination that an arcing fault is present in said circuit.

3. The method of claim 1 wherein said processing comprises incrementing one or more of a plurality of counters in a predetermined fashion in accordance with said input signal and said output signal and determining the type of load based at least in part on the states of one or more of said plurality of counters.

4. The method claim 1 wherein said processing comprises incrementing one or more of a plurality of counters in accordance with input signal and said output signal and periodically determining whether an arcing fault is present based at least in part on the states of said one or more of plurality of counters.

5. The method claim 3 wherein said processing comprises determining whether an arcing fault is present based at least in part on the states of one or more of said plurality of counters.

6. The method of claim 5 wherein said counters are implemented in software.

7. The method of claim 1 wherein said processing further includes determining whether an arcing fault is present based at least in part upon the type of load determined to be connected to said electrical circuit.

8. The method of claim 4 wherein said processing further includes determining whether an arcing fault is present based at least in part upon the type of load determined to be connected to said electrical circuit.

9. The method of claim 5 wherein said processing further includes determining whether an arcing fault is present based at least in part upon the type of load determined to be connected to said electrical circuit.

10. The method of claim 4 wherein said incrementing is further done in accordance with the type of load determined to be connected to said electrical circuit.

11. The method of claim 5 wherein said incrementing is further done in accordance with the type of load determined to be connected to said electrical circuit.

12. The method of claim 1 wherein said determining a type of load includes selecting one of a plurality of load types, including compressor load, computer load, resistor load, resistive load, inductive brush load, light dimmer load, light dimmer resistive load, and variable speed motor mode.

13. The method of claim 3 wherein said determining a type of load includes selecting one of a plurality of load types, including compressor load, computer load, resistive computer load, resistive load, inductive brush load, light dimmer load, light dimmer resistive load, and variable speed motor load.

14. The method of claim 9 wherein said determining a type of load includes selecting one of a plurality of load types, including compressor load, computer load, resistive computer load, resistive load, inductive brush load, light dimmer load, light dimmer resistive load, and variable speed motor load.

15. The method of claim 12 wherein said determining a type of load includes designating one of said load types as a default selection in the absence of a determination of any one of said other load types.

16. The method of claim 13 wherein said incrementing is performed in a different fashion for each of said load types.

17. The method of claim 5 wherein said incrementing includes incrementing a separate one or more of said counters for each type of load.

18. The method of claim 17 wherein said incrementing further includes incrementing a load type counter not associated with any of said load types.

19. The method of claim 14 wherein said incrementing includes incrementing a separate one or more of said counters for each of said load types.

20. The method of claim 4 wherein said determining whether an arcing fault is present includes using the states of selected ones of said plurality of counters for determining the presence of selected sub-harmonics in the current.

21. A system for determining whether arcing is present in an electrical circuit comprising:

a sensor for sensing current in said circuit and developing a corresponding sensor signal;

a circuit for analyzing said sensor signal to determine the presence of broadband noise in a predetermined range of frequencies, and producing a corresponding output signal; and

a controller for processing said sensor signal and said output signal to determine current characteristics and a type of load connected to said electrical circuit and to determine, using said load current characteristics and the presence of broadband noise, whether an arcing fault is present in said circuit.

22. The system of claim 21, said controller further producing a trip signal in response to a determination that an arcing fault is present in said circuit.

23. The system of claim 21 wherein said controller increments one or more of a plurality of counters in a predetermined fashion in accordance with said sensor signal and said output signal and determines the type of load based at least in part on the states of one or more of said plurality of counters.

24. The system claim 21 wherein said controller increments one or more of a plurality of counters in accordance with said sensor signal and said output signal and periodically determines whether an arcing fault is present based at least in part on the states of one or more of said plurality of counters.

25. The system claim 23 wherein said controller periodically determines whether an arcing fault is present based at least in part on the states of one or more of said plurality of counters.

26. The system of claim 25 wherein said counters are implemented in software.

27. The system of claim 21 wherein said controller further determines whether an arcing fault is present based in part upon the type of load determined to be connected to said electrical circuit.

28. The system of claim 24 wherein said controller further determines whether an arcing fault is present based in part upon the type of load determined to be connected to said electrical circuit.

29. The system of claim 25 wherein said controller further determines whether an arcing fault is present based in part upon the type of load determined to be connected to said electrical circuit.

30. The system of claim 24 wherein said controller performs said incrementing in accordance with the type of load determined to be connected to said electrical circuit.

31. The system of claim 21 wherein said controller selects one of a plurality of load types, including compressor load, computer load, resistor load, resistive computer load, inductive brush load, light dimmer load, light dimmer resistive load, and variable speed motor load.

32. The system of claim 23 wherein said controller selects one of a plurality of load types, including compressor load, computer load, resistive computer load, resistive load, inductive brush load, light dimmer load, light dimmer resistive load, and variable speed motor load.

33. The system of claim 30 wherein said controller selects one of a plurality of load types, including compressor load, computer load, resistive computer load, resistive load, inductive brush load, light dimmer load, light dimmer resistive load, and variable speed motor load.

34. The system of claim 25 wherein said controller selects one of a plurality of load types, including compressor load, computer load, resistive computer load, resistive load, inductive brush load, light dimmer load, light dimmer resistive load, and variable speed motor load.

35. The system of claim 31 wherein said controller designates one of said load types as a default selection in the absence of a determination that one of said other load types is present.

36. The system of claim 32 wherein said controller increments said one or more of said plurality of counters in a different fashion for each of said load types.

37. The system of claim 25 wherein said controller increments a separate one or more of said counters for each type of load.

38. The system of claim 37 wherein said controller further increments a load type counter not associated with any of said specified load types in a predetermined fashion in response to said sensor signal and said output signal.

39. The system of claim 33 wherein said controller increments a separate one or more of said counters for each type of load.

40. The system of claim 24 wherein said controller determines whether an arcing fault is present using the states of selected ones of said plurality of counters for determining the presence of selected sub-harmonics in the current.

41. A controller for a system for determining whether arcing is present in an electrical circuit in response to input signals, said input signals corresponding to a changing current in said circuit and to the presence of broadband noise in a predetermined range of frequencies in said circuit, said controller comprising:

a plurality of counters;

means for incrementing one or more of said plurality of counters in accordance with said input signals and

means for determining a type of load connected to said electrical circuit and whether an arcing fault is present using at least the states of one or more of said plurality counters.

42. The controller of claim 41 and further including means for producing a trip signal in response to a determination that an arcing fault is present in said circuit.

43. The controller of claim 41 wherein said counters are implemented in software.

44. The controller of claim 41 wherein said means for determining whether an arcing fault is present also uses the type of load determined to be connected to said electrical circuit.

45. The controller of claim 41 wherein said means for incrementing is responsive to the type of load determined to be connected to said electrical circuit.

46. The controller of claim 41 wherein said means for determining a type of load includes means for selecting one of a plurality of load types, including compressor load, computer load, resistive computer load, resistive load, inductive brush load, light dimmer load, light dimmer resistive load, and variable speed motor load.

47. The controller of claim 44 wherein said means for determining a type of load includes means for selecting one of a plurality of load types, including compressor load, computer load, resistive computer load, resistive load, inductive brush load, light dimmer load, light dimmer resistive load, and variable speed motor load.

48. The controller of claim 45 wherein said means for determining a type of load includes means for selecting one of a plurality of load types, including compressor load, computer load, resistive computer load, resistive load, inductive brush load, light dimmer load, light dimmer resistive load, and variable speed motor load.

49. The controller of claim 46 and further including means for designating one of said load types as a default selection in the absence of a determination of one of said other load types.

50. The controller of claim 46 wherein said means for incrementing operates in a different fashion for each of said load types.

51. The controller of claim 46 wherein said means for incrementing increments a separate one or more of said counters for each of said load types.

52. The controller of claim 46 further including means for incrementing a load type counter not associated with any of said load types.

53. The controller of claim 41 further including means for using the states of selected ones of said plurality of counters for determining the presence of selected sub-harmonics in the current.

54. The controller of claim 53 including means for incrementing one or more said counters in response to the presence of said one or more of selected sub-harmonics.

55. A method of determining whether arcing is present in an electrical circuit in response to input signals, said input signals corresponding to a changing current in said circuit and to the presence of broadband noise in a predetermined range of frequencies in said circuit, said method comprising:

incrementing one or more of a plurality of counters in accordance with said input signals; and

determining a type of load connected to said electrical circuit and whether an arcing fault is present using the states of one or more of said plurality of counters.

56. The method of claim 55 and further including producing a trip signal in response to a determination that an arcing fault is present in said circuit.

57. The method of claim 55 wherein said counters are implemented in software.

58. The method of claim 55 wherein said determining whether an arcing fault is present also uses the type of load determined to be connected to said electrical circuit.

59. The method of claim 55 wherein said incrementing is responsive to the type of load determined to be connected to said electrical circuit.

60. The method of claim 55 wherein said determining a type of load includes selecting one of a plurality of load types, including compressor load, computer load, resistive computer load, resistive load, inductive brush load, light dimmer load, light dimmer resistive load, and variable speed motor load.

61. The method of claim 57 wherein said determining a type of load includes selecting one of a plurality of load types, including compressor load, computer load, resistive computer load, resistive load, inductive brush load, light dimmer load, light dimmer resistive load, and variable speed motor load.

62. The method of claim 59 wherein said determining a type of load includes selecting one of a plurality of load types, including compressor load, computer load, resistive computer load, resistive load, inductive brush load, light dimmer load, light dimmer resistive load, and variable speed motor load.

63. The method of claim 60 and further including designating one of said load types as a default selection in the absence of a determination of one of said other load types.

64. The method of claim 60 wherein said incrementing operates in a different fashion for each of said load types.

65. The method of claim 60 wherein said incrementing includes incrementing a separate one or more of said counters for each of said load types.

66. The method of claim 60 further including incrementing one or more of a load type counter not associated with any of said load types.

67. The method of claim 55 wherein further including using the states of selected ones of said plurality of counters for determining the presence of selected sub-harmonics in the current.

68. The method of claim 67 including incrementing one or more others of said counters in response to the presence of said one or more of selected sub-harmonics.