METHOD AND APPARATUS FOR DETECTION OF RESISTIVE FAULT CONDITIONS

• US 20080122447A1
• Filed: 05/31/2007
• Published: 05/29/2008
• Est. Priority Date: 11/29/2006
• Status: Active Grant

• Current Assignee: 2D2C, Inc..
• Original Assignee: 2D2C, Inc..
• Inventors: Jones, Nicolas, Montgomery, Steven R.
• Granted Patent: US 7,847,562 B2
• Time in Patent Office: Days
• US Class Current: 324/542
• CPC Class Codes: G01R 27/16 Measuring impedance of element or network through which a current is passing from another source, e.g. cable, power line
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults

Abstract

A resistive fault condition detector for conducting one or more tests of a circuit to detect a resistive fault condition. The detector includes means for determining changes in current through a load during the test, and means for measuring changes in first and second voltages respectively between the circuit'"'"'s live and neutral conductors and between the circuit'"'"'s neutral and ground conductors during the test, the changes in the first and second voltages corresponding to the changes in the current respectively. The detector also includes means for calculating apparent source impedances for the live and neutral conductors respectively, based on the changes in current and the measured changes in the first and second voltages respectively, and means for calculating an estimated source impedance for each of the live and neutral conductors for the test.

Claims

1. A resistive fault condition detector for conducting at least one test of a circuit comprising a live conductor, a neutral conductor, a ground conductor, and a load, the detector comprising:

means for determining changes in current through the load during said at least one test;

means for measuring changes in first and second voltages respectively between the live and neutral conductors and between the neutral and ground conductors during said at least one test, said changes in said first and second voltages corresponding to said changes in said current respectively;

means for calculating apparent source impedances for the live and neutral conductors respectively based on said changes in said current and said measured changes in said first and second voltages respectively; and

means for calculating an estimated source impedance for each of said live and neutral conductors respectively for said at least one test.

2. A resistive fault condition detector according to claim 1 additionally comprising means for generating an alarm signal if any of the respective estimated source impedances for the live conductor and the neutral conductor exceeds a respective predetermined threshold value therefor.

3. A resistive fault condition detector according to claim 2 which is adapted for temporary connection to the circuit.

4. A resistive fault condition according to claim 2 which is adapted for permanent connection to the circuit.

5. A resistive fault condition detector according to claim 1 additionally comprising means for determining an imbalance between the respective estimated source impedances for the live and neutral conductors.

6. A resistive fault condition detector according to claim 5 additionally comprising means for generating an alarm signal if the imbalance exceeds a predetermined imbalance threshold value.

7. A resistive fault condition detector according to claim 6 which is adapted for temporary connection to the circuit.

8. A resistive fault condition detector according to claim 6 which is adapted for permanent connection to the circuit.

9. A resistive fault condition detector according to claim 6 in which said predetermined imbalance threshold value is variable.

10. A resistive fault condition detector according to claim 6 in which the predetermined imbalance threshold value is based on a predetermined imbalance between the respective estimated source impedances for the live and neutral conductors.

11. A resistive fault condition detector according to claim 1 in which said changes in said current are determined by measurement of said current.

12. A resistive fault condition detector according to claim 1 in which the load is connected to the circuit during said at least one test to produce said changes in said current.

13. A resistive fault condition detector according to claim 12 in which the load has known characteristics and said changes in said current are determined by calculation thereof.

14. A resistive fault condition detector according to claim 6 additionally comprising means for receiving the alarm signal and means for indicating detection of a resistive fault condition upon receipt of the alarm signal.

15. A resistive fault condition detector according to claim 6 additionally comprising means for receiving the alarm signal and means for disconnecting the live conductor upon receipt of the alarm signal.

16. A resistive fault condition detector according to claim 11 in which the circuit is repeatedly tested.

17. A resistive fault condition detector according to claim 12 in which the circuit is repeatedly tested.

18. A resistive fault condition detector according to claim 2 in which each of said respective predetermined threshold values is variable.

19. A resistive fault condition detector according to claim 2 in which each of said respective predetermined threshold values is based on a predetermined impedance for each of the live and neutral conductors respectively.

20. A resistive fault condition detector according to claim 2 additionally comprising means for receiving the alarm signal and means for indicating detection of a resistive fault condition upon receipt of the alarm signal.

21. A resistive fault condition detector according to claim 2 additionally comprising means for receiving the alarm signal and means for disconnecting the live conductor upon receipt of the alarm signal.

22. A resistive fault condition detector according to claim 1 additionally comprising a means for initiating said at least one test.

23. A method for conducting at least one test to detect a resistive fault condition in a circuit comprising a live conductor, a neutral conductor, a ground conductor, and a load, the method comprising:

(a) determining changes in current through the load during said at least one test;

(b) measuring changes in first and second voltages respectively between the live and neutral conductors and between the neutral and ground conductors during said at least one test, said changes in said first and second voltages corresponding to said changes in said current respectively;

(c) calculating apparent source impedances for the live and neutral conductors respectively based on said changes in said current and said measured changes in said first and second voltages respectively; and

(d) calculating an estimated source impedance for each of said live and neutral conductors respectively for said at least one test.

24. A method according to claim 23 additionally comprising:

(e) generating an alarm signal if any of the respective estimated source impedances for the live conductor and the neutral conductor exceeds a respective predetermined threshold value therefor.

25. A method according to claim 23 additionally comprising:

(e) determining an imbalance between the respective estimated source impedances for the live and neutral conductors.

26. A method according to claim 25 additionally comprising:

(f) generating an alarm signal if the imbalance exceeds a predetermined imbalance threshold value.

27. A method according to claim 23 in which said changes in said current are determined by measurement of said current.

28. A method according to claim 23 additionally comprising a step of connecting the load during said at least one test to produce said changes in current.

29. A method according to claim 28 in which the load has known characteristics and said changes in said current are determined by calculation thereof.

30. A resistive fault condition detector for conducting at least one test of a circuit comprising a live conductor, a neutral conductor, a ground conductor, and a load, the detector comprising:

means for initiating said at least one test;

means for determining a change in current through the load during said at least one test;

means for measuring a change in each of first and second voltages respectively between the live and neutral conductors and between the neutral and ground conductors during said at least one test, said changes in each of said first and second voltages corresponding to said change in said current;

means for calculating at least one apparent source impedance for each of the live and neutral conductors respectively based on said change in said current and said measured changes in said first and second voltages;

means for calculating an estimated source impedance for each of said live and neutral conductors respectively for said at least one test; and

means for generating an alarm signal if any one of the respective estimated source impedances for the live conductor and the neutral conductor exceeds a respective predetermined threshold value therefor.

31. A resistive fault condition detector for conducting at least one test of a circuit comprising a live conductor, a neutral conductor, a ground conductor, and a load, the detector comprising:

means for initiating said at least one test;

means for determining a change in current through the load during said at least one test;

means for measuring a change in each of first and second voltages respectively between the live and neutral conductors and between the neutral and ground conductors during said at least one test, said changes in each of said first and second voltages corresponding to said change in said current;

means for calculating at least one apparent source impedance for each of the live and neutral conductors respectively based on said change in said current and said measured changes in each of said first and second voltages;

means for calculating an estimated source impedance for each of said live and neutral conductors respectively for said at least one test; and

means for determining an imbalance between the respective estimated source impedances for the live and neutral conductors.

32. A resistive fault condition detector according to claim 31 additionally comprising means for generating an alarm signal if the imbalance exceeds a predetermined imbalance threshold value.

33. A resistive fault condition detector for monitoring a circuit comprising a live conductor, a neutral conductor, a ground conductor, and a load, the detector comprising:

means for determining changes in current through the load;

means for measuring changes in first and second voltages respectively between the live and neutral conductors and between the neutral and ground conductors, said changes in said first and second voltages corresponding to said changes in said current respectively;

means for calculating apparent source impedances for the live and neutral conductors respectively based on said changes in said current and said measured changes in said first and second voltages respectively; and

means for calculating estimated source impedances for said live and neutral conductors respectively.