System and apparatus for predicting failure in insulated systems

• US 6,300,767 B1
• Filed: 11/30/1998
• Issued: 10/09/2001
• Est. Priority Date: 11/30/1998
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Premerlani, William James, Glaser, John Stanley, Krahn, John Raymond, Kliman, Gerald Burt, Lester, Howard Leroy
• Primary Examiner(s): Metjahic, Safet
• Assistant Examiner(s): Nguyen, Vincent Q.
• Application Number:
  US09/201,224
• Time in Patent Office: 1,044 Days
• Field of Search: 324/509, 324/536, 324/520, 324/521, 324/544, 324/551
• US Class Current: 324/536
• CPC Class Codes: G01R 31/14 Circuits therefor , e.g. for generating test voltages, sensing circuits G01R31/1209 - G01R31/1227 take precedence; for testing switches G01R31/327

Abstract

A radio frequency (RF) or other form of detector detects discharges of an insulated system which can occur when electrical insulation becomes wet, for subsequent analysis and decision processes. Additionally, for RF detection, a frequency selector can be used to select a “quiet” region of the discharge spectrum before demodulation and further analysis and decision. Finally, redundant sets of such filters avoid the need to continuously reconfigure the detection system.

Claims

1. A failure prediction system for predicting failure in an insulated system, the failure prediction system comprising:

at least one RF discharge detector for generating at least one output signal representative of insulated system discharge effects; and

a data acquisition processor receiving the at least one output signal from the at least one discharge detector and analyzing the at least one output signal to predict failure of the insulated system, the data acquisition processor comprising at least one processor type selected from the processor type group consisting of;

a demodulator for demodulating the at least one output signal to an audio frequency range and at least one frequency selector for selecting at least one limited frequency band from the at least one output signal.

2. The failure prediction system of claim 1, wherein the data acquisition processor comprises the at least one frequency selector, and wherein the at least one frequency selector includes:

a mixer mixing the output signal with an adjustable frequency source and heterodyning the output signal to a desired frequency band; and

a filter filtering the heterodyned signal.

3. The failure prediction system of claim 1, wherein the data acquisition processor comprises the at least one frequency selector, and wherein the at least one frequency selector includes:

a converter receiving the output signal and outputting a demodulated signal to a resistor R-1 connected to a plurality of capacitors C selectably connected to ground such that an output bandwidth of the converter is determined by R-1*C for the selected capacitor; and

a varactor and associated variable frequency tank circuit selecting a frequency of the demodulated signal.

4. The failure prediction system of claim 1, wherein the data acquisition processor comprises the at least one frequency selector, and wherein the at least one frequency selector includes a plurality of substantially similar frequency selectors selecting frequency bands in a like-numbered plurality of distinct spectral regions, and wherein the data acquisition processor analyzes and compares the output signal in the frequency bands to determine the origin of any detected noise as between the insulated system and an extraneous noise source.

5. The failure prediction system of claim 1, wherein the data acquisition processor comprises the at least one frequency selector, and wherein the at least one frequency selector includes a single variable frequency filter used to cyclically visit and examine a plurality of preselected frequency bands, and wherein the data acquisition processor analyzes and compares the output signal in the plurality of preselected frequency bands.

6. A failure prediction system for predicting failure in an insulated system, the failure prediction system comprising:

at least one RF discharge detector for generating at least two output signals representative of insulated system discharge effects on multiple phases of the insulated system, and

a data acquisition processor for receiving the at least two output signals from the at least one discharge detector and comparing the at least two output signals to determine if the discharge effects from one phase to another phase are of opposite polarity to predict failure of the insulated system.

7. A failure prediction system for predicting failure in an insulated system comprising a busway including at least first and second busbars, the failure prediction system comprising:

at least one RF discharge detector for generating at least one output signal representative of insulated system discharge effects, the at least one RF discharge detector comprising a signal transfer circuit comprising a first capacitor connected between first busbar and, by a wire, a connection point selected from a connection point group consisting of;

(a) an electrical ground and (b) a second capacitor connected to second busbar, an RF detector transformer having a core, the wire extending from the first capacitor and passing through the core to the connection point, and a secondary winding wound about the core for providing a winding signal; and

a signal conditioner for filtering and amplifying the winding signal to generate the at least one output signal; and

a data acquisition processor for receiving the at least one output signal from the at least one discharge detector and analyzing the at least one output signal to predict failure of the insulated system.

8. The failure prediction system of claim 7, wherein the signal transfer circuit is designed to act as a matching network for the busway.

9. The failure prediction system of claim 7, wherein the insulated system includes a switchgear cabinet, the signal transfer circuit being positioned within the switchgear cabinet.

10. A failure prediction system for predicting failure in an insulated system comprising a busway, the failure prediction system comprising:

at least one RF discharge detector for generating at least one output signal representative of insulated system discharge effects; and

a data acquisition processor for receiving the at least one output signal from the at least one discharge detector and analyzing the at least one output signal to predict failure of the insulated system; and

at least one matching network positioned across the busway.

11. The failure prediction system of claim 10, wherein the at least one matching network positioned across the busway comprises at least two matching networks positioned across opposite ends of the busway.

12. A failure prediction system for predicting failure in an insulated system comprising a busway including joints, the failure prediction system comprising:

a plurality of discharge detectors situated proximate the joints for obtaining output signals to detect an effect of a discharge in the insulated system, each of the discharge detectors comprising at least one detector selected from the discharge detector group consisting of;

a chemical discharge detector;

an RF discharge detector;

an ultrasonic discharge detector; and

an audio vibration detector; and

a data acquisition processor receiving the output signals from the plurality of discharge detectors and analyzing the output signals to predict failure of the insulated system.

13. The failure prediction system of claim 12, wherein the plurality of discharge detectors comprise substantially one discharge detector per each of the joints, and wherein the data acquisition processor identifies an approximate discharge location by comparing output signals from the plurality of discharge detectors.

14. The failure prediction system of claim 12, wherein the system includes more joints than discharge detectors, and wherein the data acquisition processor identifies an approximate discharge location by comparing a relative time of arrival of pulses from output signals from the plurality of discharge detectors.

15. The system of claim 12, wherein the plurality of discharge detectors comprises a plurality of RF discharge detectors.

16. A method for predicting failure in an insulated system on-line comprising:

obtaining at least one output signal to detect an effect of a discharge in the insulated system by using at least one RF discharge detector; and

analyzing the at least one output signal to predict failure of the insulated system by using at least one processing method selected from the processing method group consisting of;

demodulating the at least one output signal to an audio frequency range and selecting at least one limited frequency band from the at least one output signal.

17. The method of claim 16 wherein obtaining at least one output signal comprises obtaining at least two output signals representative of discharge effects on multiple phases of the insulated system, and

wherein analyzing the at least one output signal further comprises analyzing the at least two output signals to predict failure of the insulated system by comparing the at least two output signals to determine if the discharge effects from one phase to another phase are of opposite polarity.

18. The method of claim 16, wherein analyzing the output signal includes selecting at least one limited frequency band from the output signal by:

mixing the output signal with an adjustable frequency source and heterodyning the output signal to a desired frequency band; and

filtering the heterodyned signal.

19. The method of claim 16, wherein analyzing the output signal includes selecting at least one limited frequency band from the output signal by using an image reject double-balanced mixer/oscillator.

20. The method of claim 16, wherein analyzing the output signal includes selecting a plurality of frequency bands from the output signal using a plurality of substantially similar frequency selectors and analyzing and comparing the output signal in the frequency bands to determine the origin of any detected noise as between the insulated system and an extraneous noise source.

21. The method of claim 16, wherein analyzing the output signal includes using a frequency selector including a single variable frequency filter to cyclically visit and examine a plurality of selected frequency bands from the output signal and analyzing and comparing the output signal in the frequency bands to determine the origin of any detected noise as between the insulated system and an extraneous noise source.

22. An on-line method for predicting failure in an insulated system comprising a busway including joints, the method comprising:

obtaining output signals to detect an effect of a discharge in the insulated system by using a plurality of discharge detectors situated proximate joints of the busway, each of discharge detectors comprising at least one detector selected from the discharge detector group consisting of;

an RF detector, a chemical detector, an ultrasonic detector, and a vibration detector; and

analyzing the output signals to predict failure of the insulated system.

23. The method of claim 22, wherein the plurality of discharge detectors comprise substantially one discharge detector per each of the joints, and wherein analyzing further includes identifying an approximate discharge location by comparing output signals from the plurality of discharge detectors.

24. The method of claim 22, wherein the system includes more joints than discharge detectors, wherein analyzing further includes identifying an approximate discharge location by comparing a relative time of arrival of pulses from output signals from the plurality of discharge detectors.

25. A failure prediction system for predicting failure in an AC line-powered insulated system, the failure prediction system comprising:

at least one discharge detector generating at least one output signal representative of insulated system discharge effects;

a data acquisition processor receiving the at least one output signal from the discharge detector and analyzing the output signal to predict failure of the insulated system; and

an electronically controllable switch for passing the at least one output signal from the at least one discharge detector to the data acquisition processor at selected intervals in the vicinity of positive and negative peaks of an AC waveform of the AC line-powered system.

26. A method for predicting failure in an AC line-powered insulated system comprising:

obtaining an output signal to detect an effect of a discharge in the insulated system; and

analyzing the output signal at selected intervals in the vicinity of positive and negative peaks of an AC waveform of the AC line-powered system to predict failure of the insulated system.