Circuit breaker with integrated self-test enhancements

• US 6,426,634 B1
• Filed: 03/29/2000
• Issued: 07/30/2002
• Est. Priority Date: 03/29/1999
• Status: Expired due to Fees

• Current Assignee: GSK Technologies Incorporated
• Original Assignee: George A. Spencer
• Inventors: Clunn, Robert Henry, Blanton, LeRoy
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): Hamdan, Wasseem H.
• Application Number:
  US09/538,395
• Time in Patent Office: 853 Days
• Field of Search: 324/424, 324/76.47, 324/76.55, 324/536, 324/522, 361/93.2, 361/98, 361/94, 361/85
• US Class Current: 324/536
• CPC Class Codes: H02H 3/044 Checking correct functioning of protective arrangements, e.g. by simulating a fault for differential current circuit breakers H02H3/335

Abstract

A circuit switching device or circuit breaker with integrated self-test enhancements is disclosed having separable contacts operable under processor control to control power to a circuit responsive to at least one of a plurality of fault conditions and operable according to a method for testing, including the steps of: controlling the switching device during a sampling cycle, to input one or more operating parameters sensed in the circuit to an A/D converter for measurement wherein the operating parameters enable detection of the fault conditions; determining whether to read a select one of the operating parameters from an output of the A/D converter into a first memory; and reading pre-determined parameter values from a second memory into the first memory during the sampling cycle instead of the operating parameters read from the A/D converter if a self-test has been invoked during the sampling cycle.

Claims

1. Apparatus for testing a circuit switching device, having separable contacts for controlling AC power supplied to a circuit responsive to at least one of a plurality of fault conditions, wherein the AC power provides an alternating line current having a line voltage and a frequency comprising:

a processor having an A/D converter with parameter inputs coupled thereto and operating according to a periodic sampling cycle to measure operating parameters of said circuit with a sensing circuit and detect said fault conditions occurring therein;

a first memory coupled to said processor for storing said operating parameters of said circuit output from said A/D converter when measured by said processor for use in determining said fault conditions;

a second memory coupled to said processor and having stored therein predetermined parameter values for substitution for said measured parameters when a self-test has been invoked during said sampling cycle;

a controller for running said self-test upon being invoked during said sampling cycle.

2. The apparatus of claim 1, comprising:

said controller automatically, upon reaching a predetermined number of counts or manually upon actuation of a test switch, running said self-test.

3. The apparatus of claim 2, wherein said controller causes an exit from said self-test if any one of a select group of operations is in process wherein said select group of operations includes one or more operations from the select group including the separable contacts have opened, an arc detection is in process or a ground fault detection is in process.

4. The apparatus of claim 2, wherein an operating parameter is read into said A/D converter for measurement upon a determination by said controller that a preliminary condition is satisfied.

5. The apparatus of claim 4, wherein said preliminary condition for measuring line current in said circuit comprises a determination whether said separable contacts are closed.

6. The apparatus of claim 4, wherein said preliminary condition for measuring line voltage of said circuit comprises a determination whether said line voltage is at or near a peak value.

7. The apparatus of claim 4, wherein said preliminary condition for measuring temperature in said switching device comprises a determination whether arc detection sensing and ground fault sensing have been completed.

8. The apparatus of claim 2, wherein said controller comprises:

indicating means for indicating a test failure when said self-test is invoked upon reaching said predetermined number of counts and a self-test procedure fails.

9. The apparatus of claim 2, wherein said controller comprises:

trip means for opening said separable contacts when said self-test is invoked upon actuation of said test switch and a self-test procedure fails; and

indicating means for indicating actuation of said test switch.

10. The apparatus of claim 2, wherein said controller comprises:

test means for performing one or more self-test procedures in a sequence;

a log for keeping track whether any self-test object failed to meet a test condition; and

a flag for setting to true at the end of said sequence.

11. The apparatus of claim 10, wherein said test means comprises:

a first pulse generator for generating a test pulse;

a first coupling means for conducting said test pulse to a line current sensing circuit; and

a first comparator for determining whether a response of said output of said A/D converter to said test pulse exceeds a self-test limit.

12. The apparatus of claim 10, wherein said test means comprises:

a first pulse generator for generating a test pulse;

a second coupling means for conducting said test pulse to a ground fault sensing circuit; and

a comparator for determining whether a response of said output of said A/D converter to said test pulse exceeds a self-test limit.

13. The apparatus of claim 10, wherein said test means comprises:

a second pulse generator for generating a test trip pulse;

a third coupling means for transmitting said test trip pulse to a trip terminal of said switching device; and

a second comparator for determining whether said test trip pulse was present at said trip terminal.

14. The apparatus of claim 1, comprising:

a sensing circuit, having an output coupled to a corresponding input of said A/D converter of said processor for sensing a one of said circuit parameters in said circuit controlled by said switching device, for obtaining a value of one of said circuit parameters to be measured.

15. The apparatus of claim 1, said processor comprising:

a first output for providing a failure indication when a self-test condition is not met.

16. The apparatus of claim 1, wherein said processor generates said periodic sampling cycle at a rate substantially synchronized with and substantially higher than the frequency of the AC power.

17. The apparatus of claim 1, wherein said operating parameters include one or more of at least voltage, current or temperature, each sensed at one or more locations in said circuit.

18. The apparatus of claim 16, wherein said rate of said periodic sampling cycle is at least equal to the Nyquist rate for ten times said line frequency of said AC power.

19. The apparatus of claim 17, wherein said operating parameters are read at predetermined times during said sampling cycle.

20. The apparatus of claim 1, wherein said first memory comprises a buffer memory for said output from said A/D converter.

21. The apparatus of claim 1, wherein said second memory comprises a look up table.

22. A method for testing a circuit switching device having separable, contacts and is operable under processor control to control AC power to a circuit in response to at least one of a plurality of fault conditions, wherein the AC power provides an alternating line current having a line voltage and a frequency comprising the steps of:

controlling the switching device during a sampling cycle, to input one or more operating parameters sensed in the circuit to an A/D converter for measurement wherein the operating parameters enable detection of the fault conditions;

determining whether to read a select one of the operating parameters from an output of the A/D converter into a first memory; and

reading predetermined parameter values from a second memory into the first memory during the sampling cycle instead of the operating parameters read from the A/D converter if a self-test has been invoked during the sampling cycle.

23. The method of claim 22, wherein the method for testing a circuit switching device further comprises the step of:

issuing a failure indication when a self-test condition is not met.

24. The method of claim 22, wherein the step of controlling the switching device comprises the steps of:

repeating the sampling cycle at a periodic rate substantially synchronized with a line frequency of the AC power under control of the processor in the switching device; and

including among the operating parameters one or more of at least voltage, current or temperature, each sensed at one or more locations in the circuit.

25. The method of claim 24, wherein the step of repeating comprises the step of:

setting the periodic rate substantially higher than the frequency of the AC power supplied to the circuit.

26. The method of claim 24, wherein the step of repeating comprises the step of:

setting the periodic rate at least equal to the Nyquist rate for ten times the frequency of the AC power.

27. The method of claim 24, wherein the step of including among the operating parameters comprises the step of:

reading the operating parameters at predetermined times during the sampling cycle.

28. The method of claim 22, wherein the step of determining comprises the step of:

conditioning the reading of one or more of the operating parameters sensed in the circuit upon a preliminary result during the operation of the sampling cycle.

29. The method of claim 28, wherein the step of conditioning comprises the step of:

checking whether the separable contacts are closed preliminary to measuring a line current in the circuit.

30. The method of claim 28, wherein the step of conditioning comprises the step of:

checking whether the line voltage of the AC power is near a peak value preliminary to measuring the line voltage.

31. The method of claim 28, wherein the step of conditioning comprises the step of:

checking whether arc sensing and ground fault sensing have been completed preliminary to measuring the temperature of the switching device.

32. The method of claim 22, wherein the step of reading comprises the steps of:

invoking a self-test automatically upon reaching a predetermined number of counts or manually upon actuation of a test switch; and

running the self-test.

33. The method of claim 32, wherein the step of running the self-test comprises the step of:

exiting the self-test if any one of a select group of operations is in process wherein the select group of operations includes one or more operations from the group including the separable contacts have opened, an arc detection is in process or a ground fault detection is in process.

34. The method of claim 32, wherein the step of invoking comprises the step of:

providing an indication of a test failure when the self-test is invoked upon reading the predetermined number of counts and a self-test procedure fails.

35. The method of claim 32, wherein the step of invoking comprises the steps of:

opening the separable contacts when the self-test is invoked upon actuation of the test switch and a self-test procedure fails; and

indicating operation of the test switch in human perceptible form.

36. The method of claim 32, wherein the step of invoking a self-test comprises the steps of:

performing one or more tests in sequence;

logging whether any self-test object failed to meet a test condition; and

setting a self-test flag true at the end of a test sequence.

37. The method of claim 36, wherein the step of performing comprises the steps of:

transmitting a test pulse to a current sensing circuit; and

testing an output of the A/D converter in response thereto.

38. The method of claim 36, wherein the step of performing comprises the steps of:

transmitting a test pulse to a ground fault sensing circuit; and

testing an output of the A/D converter in response thereto.

39. The method of claim 36, wherein the step of performing comprises the steps of:

transmitting a test trip pulse to a trip circuit in the circuit switching device; and

testing an output of the trip circuit in response thereto.