Arc fault circuit detector having two arc fault detection levels

• US 6,972,937 B1
• Filed: 08/11/2004
• Issued: 12/06/2005
• Est. Priority Date: 02/17/2000
• Status: Expired due to Term

• Current Assignee: Pass & Seymour Incorporated (Legrand SA)
• Original Assignee: Pass & Seymour Incorporated (Legrand SA)
• Inventors: Richards, Jeffrey C., Macbeth, Bruce F.
• Primary Examiner(s): LEJA, RONALD W
• Application Number:
  US10/915,965
• Time in Patent Office: 482 Days
• Field of Search: 361/42, 361/43, 361/44, 361/45, 361/46, 361/47, 361/48, 361/49
• US Class Current: 361/42
• CPC Class Codes: H02H 1/0015 Using arc detectors

Abstract

The present invention is directed to an arc fault protective device that includes a sensor configured to generate a sensor signal in response to an electrical current signal propagating in an electrical distribution system. A level detection circuit is coupled to the electrical distribution system. The level detection circuit is configured to generate a first level detection signal if a magnitude of the electrical current signal is between a first predetermined threshold level and a second predetermined threshold level. The level detection circuit also is configured to generate a second level detection signal if a magnitude of the electrical current signal is greater than the second predetermined threshold level. An arc detection circuit is coupled to the sensor and the level detection circuit. The arc detection circuit is configured to compare the sensor signal to a first arc fault signature and a second arc fault signature. The arc detection circuit is configured to provide an arc detection signal in response to the first level detection signal if the sensor signal corresponds to the first arc fault signature. The arc detection circuit also is configured to provide an arc detection signal in response to the second level detection signal if the sensor signal corresponds to the second arc fault signature. A response mechanism is coupled to the arc detection circuit, the response mechanism being responsive to the arc detection signal.

Claims

1. An arc fault protective device comprising:

a sensor configured to generate a sensor signal in response to an electrical current signal propagating in an electrical distribution system;

a level detection circuit coupled to the electrical distribution system, the level detection circuit being configured to generate a first level detection signal if a magnitude of the electrical current signal is between a first predetermined threshold level and a second predetermined threshold level, the level detection circuit also being configured to generate a second level detection signal if a magnitude of the electrical current signal is greater than the second predetermined threshold level;

an arc detection circuit coupled to the sensor and the level detection circuit, the arc detection circuit being configured to compare the sensor signal to a first arc fault signature and a second arc fault signature, the arc detection circuit being configured to provide an arc detection signal in response to the first level detection signal if the sensor signal corresponds to the first arc fault signature, and the arc detection circuit also being configured to provide an arc detection signal in response to the second level detection signal if the sensor signal corresponds to the second arc fault signature; and

a response mechanism coupled to the arc detection circuit, the response mechanism being responsive to the arc detection signal.

2. The device according to claim 1, wherein the level detection circuit includes a shunt that provides the level detection circuit with the electrical current signal.

3. The device according to claim 1, wherein the sensor includes a toroidal transformer.

4. The device according to claim 1, wherein the level detection circuit includes a comparator for sensing the magnitude of the arc fault condition.

5. The device according to claim 1, wherein the sensor signal represents a derivative (di/dt) component of the electrical current signal.

6. The device according to claim 5, wherein the derivative (di/dt) component is compared to the first arc fault signature and the second arc fault signature.

7. The device according to claim 5, wherein the toroidal transformer includes a tapped secondary winding.

8. The device according to claim 1, wherein the second arc fault signature includes the first arc fault signature.

9. The device according to claim 1, wherein the first level detection signal is provided in response to a series arc fault condition and the second level detection signal is provided in response to a parallel arc fault condition.

10. The device according to claim 9, wherein the first predetermined threshold level is substantially equal to five (5) amperes and the second predetermined threshold level is substantially equal to thirty (30) amperes.

11. The device according to claim 1, wherein the response mechanism includes a circuit interrupter that disconnects a load from the electrical distribution system in response to the arc detection signal.

12. The device according to claim 1, wherein the arc detection circuit is not configured to provide the arc detection signal in response to the first level detection signal if the sensor signal does not correspond to the first arc fault signature.

13. The device according to claim 1, wherein the arc detection circuit is not configured to provide the arc detection signal if the magnitude of the electrical current signal is below the first predetermined threshold level.

14. The device according to claim 1, wherein the arc detection circuit is configured to provide an arc detection signal in response to the first level detection signal if the sensor signal corresponds to the second arc fault signature.

15. The device according to claim 1, wherein the arc detection circuit is not configured to provide an arc detection signal in response to the second level detection signal if the sensor signal corresponds to the first arc fault signature.

16. The device according to claim 1, wherein the arc detection circuit is not configured to provide an arc detection signal in response to the second level detection signal if the sensor signal does not correspond to the second arc fault signature.

17. The device according to claim 1, wherein the first predetermined threshold level is substantially equal to five (5) amperes and the second predetermined threshold level is substantially equal to thirty (30) amperes.

18. An arc fault protective device comprising:

a sensor configured to generate a sensor signal in response to an electrical current signal propagating in an electrical distribution system;

a level detector coupled to the electrical distribution system, the level detector comparing a magnitude of the electrical current signal to at least one predetermined threshold level, the level detector providing at least one control signal if the magnitude is greater than the at least one predetermined threshold level;

an arc detector coupled to the at least one sensor and the level detector, the arc detector providing an arc detection signal in response to the at least one control signal if the sensor signal corresponds to the arc fault signature; and

a response mechanism coupled to the arc detector that is responsive to the detected arc fault.

19. The device according to claim 18, further comprising a shunt coupled to the level detector, the shunt providing the magnitude to the level detector.

20. The device according to claim 18, wherein the at least one sensor includes a toroidal transformer.

21. The device according to claim 20, wherein the toroidal transformer includes a center tapped secondary winding.

22. The device according to claim 20, wherein the sensor signal provides a derivative (di/dt) component of the electric current signal.

23. The device according to claim 18, wherein the at least one control signal is provided in response to a series arc fault condition.

24. The device according to claim 23, wherein the at least one predetermined threshold level is substantially equal to 5 Amperes.

25. The device according to claim 23, wherein the at least one control signal is activated if the magnitude of the electric current signal is greater than approximately 5 Amperes.

26. The device according to claim 18, wherein the response mechanism includes a circuit interrupter that disconnects a load from the electrical distribution system in response to the arc detection signal.

27. An arc fault protective device comprising:

a sensor configured to generate a sensor signal in response to an electrical current signal propagating in an electrical distribution system;

a level detection circuit coupled to the electrical distribution system, the level detection circuit being configured to generate a first level detection signal if a magnitude of the electrical current signal is between a first threshold substantially equal to five (5) amperes and a second threshold substantially equal to thirty (30) amperes, the level detection circuit also being configured to generate a second level detection signal if a magnitude of the electrical current signal is greater than thirty (30) amperes;

an arc detection circuit coupled to the sensor and the level detection circuit, the arc detection circuit being configured to compare the sensor signal to a first arc fault signature and a second arc fault signature, the arc detection circuit being configured to provide an arc detection signal in response to the first level detection signal if the sensor signal corresponds to the first arc fault signature, and the arc detection circuit also being configured to provide an arc detection signal in response to the second level detection signal if the sensor signal corresponds to the second arc fault signature; and

a circuit interrupter coupled to the arc detection circuit, the circuit interrupter being configured to disconnect a load from the electrical distribution system in response to the arc detection signal.

28. An arc fault protective device comprising:

a sensor configured to generate a sensor signal in response to an electrical current signal propagating in an electrical distribution system;

a level detection circuit coupled to the electrical distribution system, the level detection circuit being configured to generate a first level detection signal if a magnitude of the electrical current signal is between a first threshold substantially equal to five (5) amperes and a second threshold substantially equal to thirty (30) amperes, the level detection circuit also being configured to generate a second level detection signal if a magnitude of the electrical current signal is greater than thirty (30) amperes;

a microprocessor circuit coupled to the sensor and the level detection circuit, the microprocessor circuit being programmed to,

compare the sensor signal to a first arc fault signature and a second arc fault signature, the arc detection circuit being configured to provide an arc detection signal in response to the first level detection signal if the sensor signal corresponds to the first arc fault signature, and

provide an arc detection signal in response to the second level detection signal if the sensor signal corresponds to the second arc fault signature; and

a circuit interrupter coupled to the microprocessor circuit, the circuit interrupter being configured to disconnect a load from the electrical distribution system in response to the arc detection signal.