Detection and monitoring of partial discharge of a power line

• US 20080048710A1
• Filed: 10/20/2006
• Published: 02/28/2008
• Est. Priority Date: 07/07/2006
• Status: Active Grant

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Ambient S A
• Inventors: Cern, Yehuda
• Granted Patent: US 7,532,012 B2
• Time in Patent Office: Days
• US Class Current: 324/772
• CPC Class Codes: G01R 31/1272 of cable, line or wire insulation, e.g. using partial discharge measurements locating faults in cables G01R31/083
• CPC Class Codes: H04B 2203/5495 having measurements and testing channel
• CPC Class Codes: H04B 3/54 Systems for transmission via power distribution lines

Abstract

There is provided a method that includes (a) determining a characteristic of a fundamental spectral component of a spectrum of a power spectrum of noise on a power line, and (b) determining a condition of the power line based on the characteristic.

Claims

1. A method comprising:

determining a characteristic of a fundamental spectral component of a spectrum of a power spectrum of noise on a power line; and

determining a condition of said power line based on said characteristic.

2. The method of claim 1, wherein said determining said characteristic comprises determining whether said fundamental spectral component is synchronous with a phase of a power voltage on said power line.

3. The method of claim 1, wherein said determining said characteristic comprises determining whether said fundamental spectral component has a frequency equal to either of (a) a frequency of a power voltage on said power line, or (b) twice said frequency of said power voltage.

4. The method of claim 1, further comprising, prior to said determining said characteristic, acquiring said power spectrum during a sweep of a range of frequencies, wherein said sweep is triggered with respect to a phase of a power voltage on said power line.

5. The method of claim 4, wherein said determining said characteristic comprises:

multiplying said power spectrum by a template waveform to yield a product waveform, wherein said template waveform has a period that corresponds to either of (a) a period of said power voltage, or (b) one half of said period of said power voltage; and

determining a net area under said product waveform, wherein said net area under said product waveform is indicative of said characteristic.

6. The method of claim 4,

wherein said determining said characteristic comprises:

multiplying said power spectrum by a template waveform to yield a product waveform, wherein said template waveform has a period that corresponds to either of (a) a period of said power voltage, or (b) one half of said period of said power voltage; and

integrating said product waveform to yield a score, and

wherein said score is indicative of said characteristic.

7. The method of claim 6, wherein said condition indicates an occurrence of a partial discharge on said power line if said score is greater than a threshold value.

8. The method of claim 4,

wherein said determining said characteristic comprises:

multiplying said power spectrum by a first template waveform to yield a first product waveform;

integrating said first product waveform to yield a first score;

multiplying said power spectrum by a second template waveform to yield a second product waveform;

integrating said second product waveform to yield a second score; and

selecting a greater of said first score or said second score, to yield a resultant score, and

wherein said resultant score is indicative of said characteristic.

9. The method of claim 8, wherein said first template has a first duty cycle and said second template has a second duty cycle.

10. The method of claim 4,

wherein said determining said characteristic comprises:

multiplying said power spectrum by a template waveform to yield a first product waveform, wherein said template waveform is periodic, and wherein said multiplying is performed using a first phase relationship between said template waveform and said power spectrum;

integrating said first product waveform to yield a first score;

multiplying said power spectrum by said template waveform using a second phase relationship between said template waveform and said power spectrum, to yield a second product waveform;

integrating said second product waveform to yield a second score; and

selecting a greater of said first score or said second score, to yield a resultant score, and

wherein said resultant score is indicative of said characteristic.

11. The method of claim 4,

wherein said determining said characteristic comprises:

multiplying said power spectrum by a template waveform to yield a first product waveform, wherein said template waveform has a period that corresponds to a period of said power voltage, and wherein said multiplying is performed with said template waveform being substantially in-phase with said power spectrum;

integrating said first product waveform to yield a first score;

multiplying said power spectrum by said template waveform with said template waveform being shifted by 180 degrees, to yield a second product waveform;

integrating said second product waveform to yield a second score; and

calculating a ratio of said first score and said second score, and

wherein said ratio is indicative of said characteristic.

12. The method of claim 1,

wherein said determining said characteristic is a determining of said characteristic at a first time,

wherein said method further comprises determining said characteristic at a second time, and

wherein said condition is based on whether said characteristic changes between said first time and said second time.

13. The method of claim 1, further comprising:

determining a first magnitude of a spectral component of said power spectrum having a first frequency;

determining a second magnitude of a spectral component of said power spectrum having a second frequency that is different from said first frequency; and

determining a difference between said first and second magnitudes, and

wherein said condition is further based on said difference.

14. The method of claim 13,

wherein said power spectrum is measured at a point on said power line, and

wherein said difference is indicative of a distance between said point and a source of a partial discharge on said power line.

15. The method of claim 1,

wherein said power spectrum comprises a first frequency range and a second frequency range, and

wherein said first frequency range and said second frequency range are obtained simultaneously.

16. The method of claim 1,

wherein said power spectrum is a composite of a plurality of spectra, and

wherein said composite comprises a greatest magnitude detected for each of said plurality of spectra.

17. The method of claim 1,

wherein said method is employed at a plurality of locations in a power distribution system, thus yielding an indication of a power line condition detected at each of said plurality of locations, and

wherein said method further comprises communicating said indications of said power line condition detected at each of said plurality of locations to a central location.

18. The method of claim 17, further comprising comparing said indications of said power line condition detected at each of said plurality of locations to determine a most probable location for a source of partial discharge.

19. The method of claim 1, further comprising, prior to said determining said characteristic, acquiring discrete points of said power spectrum by a plurality of bandpass filters, wherein said points are recorded with respect to a phase of a power voltage on said power line.

20. A system that performs the method of claim 1.

21. A method comprising:

determining a first magnitude of a first spectral component of a power spectrum of noise on a power line, wherein said first spectral component is synchronous with a phase of a power voltage on said power line, and has a first frequency;

determining a second magnitude of a second spectral component of said power spectrum, wherein said second spectral component is synchronous with said phase of said power voltage, and has a second frequency that is different from said first frequency;

determining a difference between said first and second magnitudes; and

determining a condition of said power line based on said difference.