AFCI device which detects upstream and downstream series and parallel ARC faults

• US 6,504,692 B1
• Filed: 04/06/2001
• Issued: 01/07/2003
• Est. Priority Date: 04/06/2000
• Status: Expired due to Term

• Current Assignee: Pass And Seymour Incorporated (Legrand SA)
• Original Assignee: Pass And Seymour Incorporated (Legrand SA)
• Inventors: Richards, Jeffrey C., Packard, Thomas N., Romano, James P., Macbeth, Bruce F.
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US09/828,622
• Time in Patent Office: 641 Days
• Field of Search: 361/42, 361/43, 361/44, 361/45, 361/46, 361/47, 361/48, 361/49, 361/50, 361/69, 361/93.1, 361/94, 324/536, 324/924
• US Class Current: 361/42
• CPC Class Codes: H02H 1/0015 Using arc detectors
• CPC Class Codes: H02H 1/04 Arrangements for preventing response to transient abnormal conditions, e.g. to lightning or to short duration over voltage or oscillations; Damping the influence of dc component by short circuits in ac networks
• CPC Class Codes: H02H 3/44 responsive to the rate of change of electrical quantities
• CPC Class Codes: H02H 3/50 responsive to the appearance of abnormal wave forms, e.g. ac in dc installations

Abstract

Downstream series and parallel arcing in AC power lines is determined by using a detector and microprocessor to detect characteristic di/dt behavior received from a current sensor through which the power lines pass. When downstream parallel arcing is detected, the microprocessor uses a speedy algorithm which cannot be used to detect series arcing. Upstream series arcing is detected by sensing a flat voltage portion of the line voltage. Upstream parallel arcing is detected by sensing a voltage spike followed by a voltage flat portion of the line voltage. When upstream parallel arcing is detected, the microprocessor is temporarily shut off to avoid false tripping.

Claims

1. An arc fault circuit interrupter operatively connected between a line side and a load side of an AC electric power distribution system, comprising:

first sensing means for sensing a line current in said AC electric power distribution system and producing a di/dt signal;

circuit means for processing said di/dt signal and producing an output;

tripping means for interrupting power to said load;

processing means for processing said output to determine an existence of a downstream arc fault, said processing means including a normal algorithm and a speedy algorithm for processing said output, said processing means sending a trip signal to said tripping means upon determination of said downstream arc fault;

second sensing means for sensing a sinusoidal load current of a fundamental frequency of said power distribution system above a first predetermined level;

circuit means, responsive to said second sensing means, for initiating said speedy algorithm within said processing means;

circuit means for detecting an existence of an upstream series arc, and upon detection of said upstream series arc, for signaling said processing means to send said trip signal to said tripping means; and

circuit means for detecting an existence of an upstream parallel arc, and upon detection of said upstream parallel arc, for deactivating said processing means so that said processing means does not send said trip signal to said tripping means.

2. An arc fault circuit interrupter according to claim 1, further comprising circuit means for detecting an upstream surge voltage, which upon detection of said upstream surge voltage signals said processing means so that said processing means does not send said trip signal to said tripping means.

3. An arc fault circuit interrupter according to claim 1, further comprising circuit means for detecting an upstream brownout voltage, which upon detection of said upstream brownout voltage signals said processing means so that said processing means does not send said trip signal to said tripping means.

4. An arc fault circuit interrupter according to claim 1, wherein said circuit means for detecting an existence of an upstream parallel arc also detects an upstream brownout voltage, which upon detection of one of said upstream brownout voltage and said upstream parallel arc, signals said processing means so that said processing means does not send said trip signal to said tripping means.

5. An arc fault circuit interrupter according to claim 4, wherein, when said brownout voltage ceases by increasing in amplitude, said circuit means for detecting an existence of an upstream parallel arc does not signal said processing means to send said trip signal.

6. An arc fault circuit interrupter according to claim 1, further comprising third sensing means for sensing said sinusoidal load current of said fundamental frequency above a second predetermined level, which upon sensing said load current above said second predetermined level, activates said tripping means without signaling said processing means.

7. An arc fault circuit interrupter according to claim 1, further comprising circuit means for detecting a status of said tripping means, which upon detection that said tripping means has interrupted power to said load, sends a signal deactivating said processing means until said tripping means no longer interrupts power to said load.

8. An arc fault circuit interrupter according to claim 1, further comprising circuit means for blocking upstream noise which mimics a signature of arc faults in said load side of said AC power distribution system.

9. An arc fault circuit interrupter according to claim 8, wherein said circuit means for blocking noise consists of a passive filter.

10. An arc fault circuit interrupter according to claim 1, wherein said circuit means for processing said di/dt output further comprises a high pass filter having a break frequency wherein said break frequency rejects signals associated with power line converters below about 50 KHz.

11. An arc fault circuit interrupter according to claim 1, wherein said circuit means for processing said di/dt output further comprises blocking means for blocking di/dt pulses which exceed a predetermined magnitude substantially associated with nonarcing inrush events.

12. An arc fault circuit interrupter according to claim 11, wherein said blocking means presents a high impedance to said first sensing means.

13. An arc fault circuit interrupter according to claim 1, wherein said second sensing means includes a shunt resistance in series with said line current sensed by said first sensing means.

14. An arc fault circuit interrupter according to claim 1, wherein said first sensing means includes a line current sensor transformer having the line as a primary winding and having a secondary winding connected to a Zener diode, said Zener diode being connected to said tripping means, in which sensed ground fault current by said first sensing means produces a signal which breaks over said Zener diode which in turn activates said tripping means.

15. An arc fault circuit interrupter operatively connected between a line side and a load side of an AC electric power distribution system, comprising:

tripping means for interrupting power to said load;

first sensing means for sensing upstream arc faults in said AC electric power distribution system and producing an output;

processing means for processing said output to determine an existence of a downstream arc fault, said processing means sending a trip signal to said tripping means upon determination of said downstream arc fault;

first circuit means for detecting an existence of an upstream series arc, and upon detection of said upstream series arc, for signaling said processing means to trip said tripping means; and

second circuit means for detecting an existence of an upstream parallel arc, and upon detection of said upstream parallel arc, for deactivating said processing means so that said processing means does not send said trip signal to said tripping means.

16. An arc fault circuit interrupter according to claim 15, wherein said first sensing means senses line voltage in said AC electric power distribution system proximate said arc fault circuit interrupter.

17. An arc fault circuit interrupter according to claim 16, wherein said first sensing means includes a shunt resistance in series with said line current.

18. An arc fault circuit interrupter according to claim 15, further comprising:

second sensing means for sensing downstream arc faults in said AC electric distribution system; and

third circuit means for detecting an existence of downstream series and parallel arcs, and upon detection of said downstream arc, for signaling said processing means to trip said tripping means.

19. An arc fault circuit interrupter according to claim 18, wherein said second sensing means senses line current in said AC electric power distribution system and produces a di/dt signal responsive to said arc fault.

20. An arc fault circuit interrupter according to claim 19, wherein said second sensing means is a toroidal transformer.

21. An arc fault circuit interrupter according to claim 18, wherein said third circuit means includes a high pass filter having a break frequency of about 50 kHz.

22. An arc fault circuit interrupter according to claim 15, further comprising:

DC power supply means for providing a prerequisite voltage for operation of said first and second circuit means and said processing means;

said second circuit means including voltage loss detection means for early detection of said existence of said upstream parallel arc; and

said voltage loss detection means deactivating said processing means before said DC power supply means fails to supply said prerequisite voltage, thereby assuring said processing does not signal said tripping means to trip.

23. An arc fault circuit interrupter according to claim 15, further comprising second sensing means for establishing that a fundamental frequency of a load current of said AC electric power distribution system is above a predetermined level, which upon sensing said load current being above said predetermined level, activates said tripping means without signaling said processing means.

24. An arc fault circuit interrupter according to claim 23, wherein said second sensing means is a line current sensor transformer having the line as a primary winding and having a secondary winding connected to a Zener diode, said Zener diode being connected to said tripping means, in which sensed ground fault current by said first sensing means produces a signal which breaks over said Zener diode which in turn activates said tripping means.

25. An arc fault circuit interrupter according to claim 15, further comprising circuit means for detecting a status of said tripping means, which upon detection that said tripping means has interrupted power to said load, sends a signal deactivating said processing means until said tripping means no longer interrupts power to said load.

35. An arc fault circuit interrupter according to claim 23, wherein said processing means includes a reset terminal, said voltage loss detection means imposing a reset condition on said processing means for a predetermined interval exceeding a predetermined probable duration of said voltage brownout condition.

26. An arc fault circuit interrupter operatively connected between a line side and a load side of an AC electrical power distribution system, comprising:

tripping means for interrupting power to said load;

sensing means for sensing arc faults in said AC electrical power distribution system and producing an output;

processing means for processing said output to determine an existence of a downstream arc fault, said processing means sending a trip signal to said tripping means upon determination of said downstream arc fault;

first circuit means for detecting an existence of an arc fault signal, and upon detection of said arc fault signal, for signaling said processing means to trip said tripping means; and

second circuit means for detecting an existence of upstream arc mimicking noise, and upon detection of said upstream arc mimicking noise, for deactivating said processing means so that said processing means does not send a trip signal to said tripping means.

27. An arc fault circuit interrupter according to claim 26, wherein said arc mimicking noise comprises an upstream voltage surge condition.

28. An arc fault circuit interrupter according to claim 27, wherein said voltage surge condition is detected by a voltage on a semiconductor exceeding a barrier voltage and a current passing therethrough.

29. An arc fault circuit interrupter according to claim 28 wherein said voltage surge condition is detected by a metal oxide varistor.

30. An arc fault circuit interrupter according to claim 27, further comprising voltage surge detection circuitry, wherein said processing means includes a reset terminal, said voltage surge detection circuitry imposing a reset condition on said processing means for a predetermined interval exceeding a predetermined probable duration of said voltage surge condition.

31. An arc fault circuit interrupter according to claim 26 wherein said first circuit means is not responsive to upstream parallel arc faults.

32. An arc fault circuit interrupter according to claim 26 wherein said arc mimicking.

33. An arc fault circuit interrupter according to claim 32, further comprising:

DC power supply means for providing a prerequisite voltage for operation of said first and second circuit means and said processing means;

voltage loss detection means for early detection of said voltage brownout condition; and

said voltage loss detection means deactivating said processing means before said DC power supply fails to supply said prerequisite voltage, thereby assuring said processing means does not signal said tripping means to trip.

34. An arc fault circuit interrupter according to claim 33, wherein, when a voltage associated with said voltage brownout condition increases in amplitude such that said voltage brownout condition ceases, said first circuit means does not signal said processing means to send said trip signal.

36. An arc fault circuit interrupter operatively connected between a line side and a load side of an AC electric power distribution system, comprising:

tripping means for interrupting power to said load;

sensing means for sensing arc faults in said AC electric power distribution system and producing an output;

processing means for processing said output to determine an existence of a downstream arc fault, said processing means sending a trip signal to said tripping means upon determination of said downstream arc fault;

first circuit means for detecting an existence of arc fault signal, and upon detection of said arc fault signal, for signaling said processing means to trip said tripping means; and

filter means located upstream of said sensing means;

wherein said filter means prevents arc mimicking noise on said AC electric power distribution system from signaling s aid processing means to trip said tripping means.

37. An arc fault circuit interrupter according to claim 36 further comprising a housing, all components of said arc fault circuit interrupter being contained therein.

38. An arc fault circuit interrupter according to claim 37 wherein said housing is a receptacle.

39. An arc fault circuit interrupter according to claim 36 where in s aid filter means comprises:

an inductor in series with said line; and

a downstream impedance containing capacitance in parallel with said AC electric power.

40. An arc fault circuit interrupter according to claim 36, further comprising circuit means for detecting an existence of an upstream series arc, and upon detection of said upstream series arc, for signaling said processing means to trip said tripping means.

41. An arc fault circuit interrupter according to claim 40, further comprising circuit means for detecting an existence of an upstream parallel arc, and upon detection of said upstream parallel arc, for deactivating said processing means so that said processing means does not send said trip signal to said tripping means.

42. An arc fault circuit interrupter according to claim 41, wherein said means for detecting an existence of an upstream parallel arc includes means for detecting an input voltage level to said arc fault circuit interrupter and means for converting said input voltage level to a digital signal, wherein said digital signal deactivates said processing means.

43. An arc fault circuit interrupter operatively connected between a line side and a load side of an AC electric power distribution system, comprising:

tripping means for interrupting power to said load;

first sensing means for sensing a line current in said AC electric power distribution system and producing a di/dt signal;

circuit means for processing said di/dt signal and producing an output;

processing means for processing said output to determine an existence of a downstream arc fault, said processing means including a normal algorithm and a speedy algorithm for processing said output, said processing means sending a trip signal to said tripping means upon determination of said downstream arc fault;

second sensing means for sensing a sinusoidal load current of a fundamental frequency of said power distribution system above a first predetermined level; and

circuit means, responsive to said second sensing means for initiating said speedy algorithm within said processing means when said first predetermined level is exceeded for a predetermined interval, wherein said second sensing means includes a shunt resistance in series with said line.

44. An arc fault circuit interrupter according to claim 43, wherein said first sensing means is a line current sensor transformer having the line as a primary winding and having a secondary winding connected to a Zener diode, said Zener diode being connected to said tripping means, in which sensed ground fault current by said first sensing means produces a signal which breaks over said Zener diode which in turn activates said tripping means, without signaling said processing means.

45. An arc fault circuit interrupter operatively connected between a line side and a load side of an AC electric power distribution system, comprising:

tripping means for interrupting power to said load;

sensing means for sensing a ground fault current in said AC electric power distribution system;

where in said sensor is connected to a Zener diode, said Zener diode being connected to said tripping means, in which sensed ground fault current by said first sensing means produces a signal which breaks over said Zener diode which in turn activates said tripping means.

46. An arc fault circuit interrupter according to claim 45 in which said sensor is a toroidal transformer in which the line is a primary winding and said Zener diode is connected to a secondary winding.

47. An arc fault circuit interrupter operatively connected between a line side and a load side of an AC electric power distribution system, comprising:

tripping means for interrupting power to said load;

sensing means for sensing a line current in said AC electric power distribution system, said sensing means including a toroidal transformer in which the line is a primary winding and a secondary winding produces a di/dt signal;

circuit means for processing said di/dt signal and producing an output;

processing means for processing said output to send a trip signal to said tripping means upon detection of said di/dt signal;

circuit means for determining a magnitude of said di/dt signal; and

high impedance means responsive to said magnitude, wherein a plurality of di/dt signals greater than a pre-established threshold cause said high impedance means to open, thereby blocking said plurality of di/dt signals from said processing means, and unloading said secondary winding of said sensor.

48. An arc fault circuit interrupter according to claim 47 wherein said high impedance means includes an FET.