Method and apparatus for detecting partial discharge within electrical equipment

Patent metadata

Field	Value
Publication number	US-10317451-B2
Application number	US-201314763561-A
Country	US
Kind code	B2
Filing date	Nov 21, 2013
Priority date	Apr 22, 2013
Publication date	Jun 11, 2019
Grant date	Jun 11, 2019

Abstract

A partial discharge detection apparatus detects a plurality of discharge events, finds a time interval between the plurality of discharge events, and determines, where the discharge events occur at a time interval shorter than a threshold time, that a partial discharge has occurred within a metal enclosure, or determines, where the discharge events occur only at a time interval longer than the threshold time, that a discharge has occurred outside the metal enclosure. The partial discharge detection apparatus can thus readily distinguish between a partial discharge that occurs within the metal enclosure of a gas-insulated switchgear and a discharge that occurs outside the metal enclosure.

First claim

The invention claimed is:

1. A method for detecting a partial discharge within electrical equipment in which a conductor is provided within a metal enclosure filled with an insulating gas, and an alternating current (AC) high voltage of a frequency not higher than a utility frequency is applied between the conductor and the metal enclosure, the method detecting a partial discharge within the metal enclosure, the method comprising:
detecting a plurality of discharge events;
finding a time interval between each two consecutive discharge events of the plurality of discharge events;
determining:
when at least one of the time intervals is shorter than a threshold time defined between a discharge time interval in a SF 6 gas and a discharge time interval in the atmosphere, that the partial discharge has occurred within the metal enclosure, and
when each of the time intervals is longer than the threshold time, that a discharge has only occurred outside the metal enclosure; and

notifying a user that the partial discharge has occurred within the metal enclosure upon determination that the partial discharge has occurred within the metal enclosure.

2. The method for detecting a partial discharge within the electrical equipment according to claim 1 , the method further comprising:
creating a histogram showing occurrence frequencies of time intervals between each two consecutive discharge events of the plurality of discharge events;
when it is determined that the partial discharge has occurred within the metal enclosure, finding a half-value of the histogram as a width of variation in occurrence frequencies of the time interval;
when the half-value width falls within a first range, determining that a cause of the partial discharge is a first discharge source; and
when the half-value width falls within a second range, determining that the cause is a second discharge source.

3. The method for detecting a partial discharge within the electrical equipment according to claim 1 , wherein the threshold time is 100 μs.

4. The method for detecting a partial discharge within the electrical equipment according to claim 1 , wherein the threshold is a lower limit of the discharge time interval in the atmosphere.

5. A method for detecting a partial discharge within electrical equipment in which a conductor is provided within a metal enclosure filled with an insulating gas, and an alternating current (AC) high voltage of a frequency not higher than a utility frequency is applied between the conductor and the metal enclosure, the method detecting a partial discharge within the metal enclosure, the method comprising:
detecting a plurality of events;
finding a peak value of occurrence frequencies of time intervals between each two consecutive discharge events of the plurality of discharge events;
determining:
when the peak value is present within a time interval shorter than a threshold time defined between a discharge time interval in a SF 6 gas and a discharge time interval in the atmosphere, that the partial discharge has occurred within the metal enclosure, and
when the peak value is present only within a time interval longer than the threshold time, that a discharge has occurred outside the metal enclosure; and
notifying a user that the partial discharge has occurred within the metal enclosure upon determination that the partial discharge has occurred within the metal enclosure.

6. The method for detecting a partial discharge within the electrical equipment according to claim 5 , wherein the threshold is a lower limit of the discharge time interval in the atmosphere.

7. An apparatus for detecting a partial discharge within electrical equipment in which a conductor is provided within a metal enclosure filled with an insulating gas, and an alternating current (AC) high voltage of a frequency not higher than a utility frequency is applied between the conductor and the metal enclosure, the apparatus detecting a partial discharge within the metal enclosure, the apparatus comprising:
a discharge sensor configured to detect a plurality of discharge events; and
circuitry configured to:
find a time interval between each two consecutive discharge events of the plurality of discharge events;
determine:
when at least one of the time intervals is shorter than a threshold time defined between a discharge time interval in a SF 6 gas and a discharge time interval in the atmosphere, that the partial discharge has occurred within the metal enclosure, and
when each of the time intervals is longer than the threshold time, that a discharge has only occurred outside the metal enclosure; and
notify a user that the partial discharge has occurred within the metal enclosure upon determination that the partial discharge has occurred within the metal enclosure.

8. The apparatus for detecting a partial discharge within the electrical equipment according to claim 7 , wherein
the circuitry is further configured to:
create a histogram showing occurrence frequencies of time intervals between each two consecutive discharge events of the plurality of discharge events;
when the circuitry determines that the partial discharge has occurred within the metal enclosure, find a half-value of the histogram as a width of variation in the occurrence frequency of the time interval between the plurality of discharge events;
when the half-value width falls within a first range, determine that a cause of the partial discharge is a first discharge source; and
when the half-value width falls within a second range, determine that the cause is a second discharge source.

9. The apparatus for detecting a partial discharge within the electrical equipment according to claim 7 , wherein the threshold time is 100 μs.

10. The apparatus for detecting a partial discharge within the electrical equipment according to claim 7 , wherein the threshold is a lower limit of the discharge time interval in the atmosphere.

11. An apparatus for detecting a partial discharge within electrical equipment in which a conductor is provided with a metal enclosure filled with an insulating gas, and an alternating current (AC) high voltage of a frequency not higher than a utility frequency is applied between the conductor and the metal enclosure, the apparatus detecting a partial discharge within the metal enclosure, the apparatus comprising:
a discharge sensor configured to detect a plurality of discharge events; and
circuitry configured to:
find a peak value of occurrence frequencies of time intervals between each two consecutive discharge events of the plurality of discharge events, and
determine:
when the peak value is present within a time interval shorter than a threshold time defined between a discharge time interval in a SF 6 gas and a discharge time interval in the atmosphere, that the partial discharge has occurred within the metal enclosure, and
when the peak value is present only within a time interval longer than the threshold time, that a discharge has occurred outside the metal enclosure; and
notify a user that the partial discharge has occurred within the metal enclosure upon determination that the partial discharge has occurred within the metal enclosure.

12. The apparatus for detecting a partial discharge within the electrical equipment according to claim 11 , wherein the threshold is a lower limit of the discharge time interval in the atmosphere.

Assignees

• Mitsubishi Electric Corp

Inventors

• Yoshimura Manabu
• Yabe Tatsuya
• Ito Takashi

Classifications

• G01R31/1254 Primary

  of gas-insulated power appliances or vacuum gaps (testing switches G01R31/327; detecting electrical or mechanical defects in encased switchgear H02B13/065) · CPC title

• H02B13/055

  Features relating to the gas · CPC title

• H02B13/065

  Means for detecting or reacting to mechanical or electrical defects · CPC title

• G01R31/44

  Testing lamps · CPC title

• H02G5/06

  Totally-enclosed installations, e.g. in metal casings · CPC title