Method for predicting fault conditions in an intelligent electronic device

• US 6,121,886 A
• Filed: 05/18/1999
• Issued: 09/19/2000
• Est. Priority Date: 05/18/1999
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Andersen, Bo L.
• Primary Examiner(s): Lefkowitz, Edward
• Application Number:
  US09/313,795
• Time in Patent Office: 490 Days
• Field of Search: 340/635, 340/638, 340/644, 361/93
• US Class Current: 340/635
• CPC Class Codes: G05B 23/0235 based on a comparison with predetermined threshold or range, e.g. "classical methods", carried out during normal operation; threshold adaptation or choice; when or how to compare with the threshold
• CPC Class Codes: G08B 21/187 Machine fault alarms
• CPC Class Codes: H02H 3/006 Calibration or setting of parameters
• CPC Class Codes: H02H 3/04 with warning or supervision in addition to disconnection, e.g. for indicating that protective apparatus has functioned watching of pilot wires H02H1/0084; protection of protective arrangements H02H7/008; indication of the state of electronic switches H03K17/18
• CPC Class Codes: H02H 3/44 responsive to the rate of change of electrical quantities

Abstract

A method of predicting an eminent circuit breaker trip condition using an intelligent electronic device such as a trip unit, a protective relay, a power meter or other IED is presented. The intelligent electronic device includes a microcontroller and associated memories. An algorithm (program) stored in a memory of the intelligent electronic device generates a near-trip event for each trip event calculation if preset thresholds for the measured parameters are breached.

Claims

1. A method of predicting fault conditions in an intelligent electronic device having a trip event threshold, said method comprising:

sensing an electrical signal to provide a sensed signal indicative of an electrical characteristic of the electrical signal;

comparing a rate of change in said sensed signal and a near-trip event threshold to detect a near-trip event, said near-trip event threshold defining said near-trip event before a potential trip event as defined by the trip event threshold of the intelligent electronic device; and

generating a near-trip event signal when said near-trip event is detected.

2. The method of claim 1 wherein said comparing a rate of change in said sensed signal and said near-trip event threshold comprises comparing said rate of change in said sensed signal, said near-trip event threshold and a time interval.

3. The method of claim 1 wherein said comparing a rate of change in said sensed signal and said near-trip event threshold comprises:

subtracting said sensed signal from the trip event threshold to define a difference;

dividing said difference by the trip event threshold to define a quotient;

comparing said quotient to said near-trip event threshold; and

detecting said near-trip event when said quotient is greater than or equal to said near-trip event threshold.

4. The method of claim 1 wherein the trip event threshold is associated with said electrical characteristic.

5. The method of claim 1 wherein the trip event threshold is associated with time.

6. The method of claim 1 wherein said comparing of said rate of change in said sensed signal and said near-trip event threshold comprises:

multiplying the trip event threshold and said near-trip event threshold to define a product;

comparing said product to said sensed signal; and

detecting said near-trip event when said sensed signal is greater than or equal to said product.

7. The method of claim 1 wherein said electrical characteristic comprise electrical current.

8. The method of claim 1 wherein said electrical characteristic comprise electrical voltage.

9. The method of claim 1 further comprising:

remotely setting said near-trip event threshold.

10. The method of claim 1 wherein the intelligent electronic device comprises an electronic trip unit or a protective relay.

11. The method of claim 1 further comprising:

displaying information indicating the occurrence of said near-trip event.

12. An intelligent electronic device comprising:

a sensor for sensing an electrical signal to provide a sensed signal indicative to an electrical characteristic of the electrical signal; and

a signal processor responsive to said sensed signal, and having memory for storing signals including program signals defining an executable program for,

comparing a rate of change in said sensed signal and near-trip event threshold to detect a near-trip event, said near-trip event threshold defining said near-trip event before a potential trip event as defined by the trip event threshold of the intelligent electronic device, and

generating a near-trip event signal when said near-trip event is detected.

13. The intelligent electronic device of claim 12 wherein comparing a rate of change in said sensed signal and said near-trip event threshold comprises comparing said rate of change in said sensed signal, said near-trip event threshold, and a time interval.

14. The intelligent electronic device of claim 12 wherein said comparing of rate of change in said sensed signal and said near-trip event threshold comprises:

subtracting said sensed signal from the trip event threshold to define a difference;

dividing said difference by the trip event threshold to define a quotient;

comparing said quotient to said near-trip event threshold; and

detecting said near-trip event when said quotient is greater than or equal to said near-trip event threshold.

15. The intelligent electronic device of claim 12 wherein the trip event threshold is associated with said electrical characteristic.

16. The intelligent electronic device of claim 12 wherein the trip event threshold is associated with time.

17. The intelligent electronic device of claim 12 wherein said comparing of said rate of change in said sensed signal and said near-trip event threshold comprises:

multiplying the trip event threshold and said near-trip event threshold to define a product;

comparing said product to said sensed signal; and

detecting said near-trip event when said sensed signal is greater than or equal to said product.

18. The intelligent electronic device of claim 12 wherein said electrical characteristic comprise electrical current.

19. The intelligent electronic device of claim 12 wherein said electrical characteristic comprise electrical voltage.

20. The intelligent electronic device of claim 12 wherein said program signals further define said executable program for remotely setting said near-trip event threshold.

21. The intelligent electronic device of claim 12 wherein the intelligent electronic device comprises an electronic trip unit or a protective relay.

22. The intelligent electronic device of claim 12 further comprising:

a display responsive to said near-trip event signal for displaying information indicating the detection of said near-trip event.