Alternating current series arc fault detection method

• US 7,633,729 B2
• Filed: 10/22/2007
• Issued: 12/15/2009
• Est. Priority Date: 10/22/2007
• Status: Active Grant

• Current Assignee: Hamilton Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Hamilton Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Kilroy, Donald G., Oldenburg, Wayne H.
• Primary Examiner(s): Leja; Ronald W
• Application Number:
  US11/876,004
• Publication Number:
  US 20090103216A1
• Time in Patent Office: 785 Days
• Field of Search: 361/42
• US Class Current: 361/42
• CPC Class Codes: H02H 1/0015 Using arc detectors

Abstract

A method of detecting and indicating a presence of alternating current (AC) series arc fault events in current supplied by an AC electrical power source to an electrical load for the power source comprises the steps of: measuring positive and negative current through the load over a first sample cycle of the AC power to establish first measured positive and first measured negative current levels; determining the absolute value of the first measured positive and first measured negative current levels to establish a first absolute positive current level and a first absolute negative current level; adding the first absolute positive current level and the first absolute negative current level to establish a first sum current level; measuring positive and negative current through the load over a second sample cycle staggered from the first sample cycle to establish second measured positive and second measured negative current levels; determining the absolute value of the second measured positive and second measured negative current levels to establish a second absolute positive current level and a second absolute negative current level; adding the second absolute positive current level and the second absolute negative current level to establish a second sum current level; subtracting the second sum current level from the first sum current level to establish a current difference level; and indicating a series arc fault event if the current difference level exceeds a predetermined threshold level.

Claims

1. A method of detecting and indicating a presence of alternating current (AC) series arc fault events in current supplied by an AC electrical power source to an electrical load for the power source, comprising the steps of:

measuring positive and negative current through the load over a first sample cycle of the AC power to establish first measured positive and first measured negative current levels;

determining the absolute value of the first measured positive and first measured negative current levels to establish a first absolute positive current level and a first absolute negative current level;

adding the first absolute positive current level and the first absolute negative current level to establish a first sum current level;

measuring positive and negative current through the load over a second sample cycle of the AC power staggered from the first sample cycle to establish second measured positive and second measured negative current levels;

determining the absolute value of the second measured positive and second measured negative current levels to establish a second absolute positive current level and a second absolute negative current level;

adding the second absolute positive current level and the second absolute negative current level to establish a second sum current level;

subtracting the second sum current level from the first sum current level to establish a current difference level; and

indicating a series arc fault event if the current difference level exceeds a predetermined threshold level.

2. The method of claim 1, wherein the second sample cycle is staggered by one half cycle of the AC power after the beginning of the first sample cycle.

3. The method of claim 2, wherein the method repeats in consecutive AC half cycles to detect and indicate consecutive series arc fault events.

4. The method of claim 1, wherein the second sample cycle is staggered by a full cycle of the AC power after the beginning of the first sample cycle.

5. The method of claim 4, wherein the method repeats in consecutive AC full cycles to detect and indicate consecutive series arc fault events.

6. The method of claim 1, wherein the indicating step comprises the step of interrupting power supplied by the power source to the load if the current difference level exceeds a predetermined threshold level.

7. The method of claim 1, wherein the indicating step comprises delaying indication of a series arc fault event until at least a predetermined number of current difference levels exceed the predetermined threshold level within a predetermined period.

8. The method of claim 1, wherein the indicating step comprises delaying protection of a series arc fault event until at least a predetermined number of current difference levels exceed the predetermined threshold level within a predetermined period.

9. Computer-readable media for storing instructions to detect and indicate a presence of alternating current (AC) series arc fault events in current supplied by an AC electrical power source to an electrical load for the power source, comprising:

instructions to measure positive and negative current through the load over a first sample cycle of the AC power to establish first measured positive and first measured negative current levels;

instructions to determine the absolute value of the first measured positive and first measured negative current levels to establish a first absolute positive current level and a first absolute negative current level;

instructions to add the first absolute positive current level and the first absolute negative current level to establish a first sum current level;

instructions to measure positive and negative current through the load over a second sample cycle of the AC power staggered from the first sample cycle to establish second measured positive and second measured negative current levels;

instructions to determine the absolute value of the second measured positive and second measured negative current levels to establish a second absolute positive current level and a second absolute negative current level;

instructions to add the second absolute positive current level and the second absolute negative current level to establish a second sum current level;

instructions to subtract the second sum current level from the first sum current level to establish a current difference level; and

instructions to indicate a series arc fault event if the current difference level exceeds a predetermined threshold level.

10. The computer-readable media of claim 9, wherein the instructions to measure positive and negative current through the load over a second sample cycle comprises instructions to stagger the sample by one half cycle of the AC power after the beginning of the first sample cycle.

11. The computer-readable media of claim 10, wherein the instructions repeat in consecutive AC half cycles to detect and indicate consecutive series arc fault events.

12. The computer-readable media of claim 9, wherein the instructions to measure positive and negative current through the load over a second sample cycle comprises instructions to stagger the sample by one full cycle of the AC power after the beginning of the first sample cycle.

13. The computer-readable media of claim 12, wherein the instructions repeat in consecutive AC full cycles to detect and indicate consecutive series arc fault events.

14. The computer-readable media of claim 9, wherein the instructions indicate a series arc fault event comprise instructions to interrupt power supplied by the power source to the load if the current difference level exceeds a predetermined threshold level.

15. The computer-readable media of claim 9, wherein the instructions to indicate a series arc fault event comprise instructions to delay indication of a series arc fault event until at least a predetermined number of consecutive current difference levels exceed the predetermined threshold level within a predetermined period.

16. The computer-readable media of claim 9, wherein the instructions to indicate a series arc fault event comprise instructions to delay protection of a series arc fault event until at least a predetermined number of consecutive current difference levels exceed the predetermined threshold level within a predetermined period.

17. An electrical system comprising:

an electrical alternating current (AC) load;

an electrical AC power source;

an electrical AC power bus for coupling power from the source to the load; and

a system control unit for controlling the electrical system that detects and indicates a presence of alternating current (AC) series arc fault events in current supplied by the power source to the load;

wherein the system control unit;

measures positive and negative current through the load over a first sample cycle of the AC power to establish first measured positive and first measured negative current levels;

determines the absolute value of the first measured positive and first measured negative current levels to establish a first absolute positive current level and a first absolute negative current level;

adds the first absolute positive current level and the first absolute negative current level to establish a first sum current level;

measures positive and negative current through the load over a second sample cycle of the AC power staggered from the first sample cycle to establish second measured positive and second measured negative current levels;

determines the absolute value of the second measured positive and second measured negative current levels to establish a second absolute positive current level and a second absolute negative current level;

adds the second absolute positive current level and the second absolute negative current level to establish a second sum current level;

subtracts the second sum current level from the first sum current level to establish a current difference level; and

indicates a series arc fault event if the current difference level exceeds a predetermined threshold level.

18. The system of claim 17, wherein the second sample cycle is staggered by one half cycle of the AC power after the beginning of the first sample cycle.

19. The system of claim 18, wherein the system control unit repeats samples in consecutive AC half cycles to detect and indicate consecutive series arc fault events.

20. The system of claim 17, wherein the second sample cycle is staggered by a full cycle of the AC power after the beginning of the first sample cycle.

21. The system of claim 20, wherein the system control unit repeats samples in consecutive AC full cycles to detect and indicate consecutive series arc fault events.

22. The system of claim 17, wherein the system control unit interrupts power supplied by the power source to the load if the current difference level exceeds a predetermined threshold level.

23. The system of claim 17, wherein the system control unit delays indication of a series arc fault event until at least a predetermined number of consecutive current difference levels exceed the predetermined threshold level within a predetermined period.

24. The system of claim 17, wherein the system control unit delays protection of a series arc fault event until at least a predetermined number of consecutive current difference levels exceed the predetermined threshold level within a predetermined period.