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EP-4382925-B1 - PARTIAL DISCHARGE DETERMINATION DEVICE AND METHOD

EP4382925B1EP 4382925 B1EP4382925 B1EP 4382925B1EP-4382925-B1

Inventors

  • YAMADA, HIROMICHI
  • Onoe, Shinsuke
  • KIDO, MITSUYASU

Dates

Publication Date
20260513
Application Date
20220607

Claims (8)

  1. A partial discharge determination apparatus that determines partial discharge occurring in a power transmission facility, the partial discharge determination apparatus comprising: a partial discharge measurement unit (5) that acquires measurement data representing a charge amount and a phase of each partial discharge occurring in the power transmission facility; a noise processing unit (51) that removes or reduces noise included in the measurement data based on statistical information; a φ-q-n data generation unit (52) that generates φ-q-n data representing a charge amount, a phase, and the number of pulses of each of the partial discharge and the noise included in the measurement data from the measurement data from which the noise has been removed or reduced by the noise processing unit; a learning model generation unit (54) that generates a learning model by performing machine learning using the φ-q-n data of the partial discharge and the noise; and a determination unit (56) that determines whether or not at least the partial discharge has occurred by using the learning model based on the φ-q-n data generated by the φ-q-n data generation unit.
  2. The partial discharge determination apparatus according to claim 1, wherein the noise processing unit removes or reduces the noise from the measurement data by separating the measurement data into data of the partial discharge and data of the noise with a predetermined range centered on a charge amount at which a frequency is maximum in charge amount distribution of the measurement data as the noise.
  3. The partial discharge determination apparatus according to claim 2, wherein the noise processing unit thins the separated data of the noise at a predetermined ratio, and combines the thinned data of the noise and the separated data of the partial discharge to remove or reduce the noise from the measurement data.
  4. The partial discharge determination apparatus according to claim 1, wherein the determination unit determines a progress degree of the partial discharge in a case where the partial discharge has occurred.
  5. A partial discharge determination method executed in a partial discharge determination apparatus that determines partial discharge occurring in a power transmission facility, the partial discharge determination method comprising: a first step of acquiring measurement data representing a charge amount and a phase of each partial discharge occurring in the power transmission facility; a second step of removing or reducing noise included in the measurement data based on statistical information; a third step of generating φ-q-n data representing a charge amount, a phase, and the number of pulses of each of the partial discharge and the noise included in the measurement data from the measurement data from which the noise has been removed or reduced; and a fourth step of determining whether or not at least the partial discharge has occurred by using a learning model generated by performing machine learning using the φ-q-n data of the partial discharge and the noise based on the φ-q-n data.
  6. The partial discharge determination method according to claim 5, wherein in the second step, the noise is removed or reduced from the measurement data by separating the measurement data into data of the partial discharge and data of the noise with a predetermined range centered on a charge amount at which a frequency is maximum in charge amount distribution of the measurement data as the noise.
  7. The partial discharge determination method according to claim 6, wherein in the second step, the separated data of the noise is thinned at a predetermined ratio, and the thinned data of the noise and the separated data of the partial discharge are combined to remove or reduce the noise from the measurement data.
  8. The partial discharge determination method according to claim 5, wherein in the fourth step, a progress degree of the partial discharge is determined in a case where the partial discharge has occurred.

Description

Technical Field The present invention relates to a partial discharge determination apparatus and a partial discharge determination method, and is suitably applied to, for example, a partial discharge determination apparatus that determines insulation degradation of an underground power transmission cable. Background Art In an urban area, a huge power transmission network is laid in the ground, and power generated in a power plant is transmitted to each power consumer via the power transmission network. Since underground power transmission facilities have increased in the high economic growth period, and many of them are now 40 years old from the start of operation, a technology for diagnosing aging degradation has become important. A main factor of aging degradation of a cable is degradation of an insulator used for the cable. As one of degradation diagnosis technologies for the underground power transmission cable, there is a partial discharge measurement method. The underground power transmission cable has a structure in which a conductor through which a current flows is covered with an insulator. In a case where a void is generated in the insulator due to aging degradation, partial discharge occurs in the void, and finally insulation breakdown occurs. In the partial discharge measurement method, such a partial discharge is observed, and the degree of insulation degradation of the underground power transmission cable is diagnosed based on the observation result, and various companies and research organizations have conducted studies to elucidate a partial discharge generation mechanism and estimate the degree of insulation degradation from partial discharge characteristics. For example, NPL 1 describes a degradation diagnosis estimation method to which a result of measuring a phase angle characteristic of a partial discharge pulse from the start of voltage application to insulation breakdown using an experimental electrode, and a pattern recognition method are applied. Here, the phase angle characteristic of the partial discharge pulse is defined as a characteristic of the number n of partial discharge pulses with a charge amount q generated at a phase angle φ of a cable application voltage, and is also referred to as a φ-q-n characteristic. In this literature, changes in φ-q-n characteristic in five time zones from the start of voltage application to insulation breakdown are illustrated. For example, immediately after voltage application, a positive partial discharge pulse is generated in a phase angle range of -30° to 90°, and a negative partial discharge pulse is generated in a phase angle range of 150° to 270°. A discharge charge amount is distributed from 10 pC to 400 pC for the positive pulse, and is distributed from -10 pC to -800 pC for the negative pulse. This causes a change in phase angle range and discharge charge amount range over time. In the degradation estimation method, the φ-q-n characteristic is generated from measurement data, and similarity comparison with a standard pattern corresponding to each of degree of degradations of a plurality of stages created in advance is performed. In addition, NPL 2 discloses modeling of a state of degradation of an oil-filled (OF) cable in which bubbles are generated in an oil gap defect, design electric fields from 66 or 77 kV to 275 kV, measurement of a partial discharge characteristic under a hydraulic condition within an actual operation range, and an analysis result. Among them, it is described that a range of 100 pC or less is excluded as base noise removal in measurement of partial discharge by a digital oscilloscope. Further, PTL 1 discloses a partial discharge detection system that performs machine learning on a signal generated during a predetermined period from the start of operation of an electric device to determine whether or not partial discharge has occurred in the electric device based on a learning model that learns a signal including noise near the electric device and a signal generated after the predetermined period has elapsed. Citation List Patent Literature PTL 1: JP 2020-12726 A Non-Patent Literatures NPL 1: Fumitaka Komori and three others, "Insulation degradation Diagnosis and Remaining Life Estimation Using Pattern Recognition by Partial Discharge Occurrence Phase Angle Distribution", The Institute of Electrical Engineers of Japan, 1993, Vol. 113-A, No. 8, p. 586-593NPL 2: Yuta Makino, "Influence of Hydraulic Pressure and Electric Field on Partial Discharge Characteristic in OF Cable Oil-Impregnated Paper_Insulating Oil-Impregnated Insulation System Including Oil Film Defect", Report of Central Research Institute of Electric Power Industry, H15107, 2016 Summary of Invention Technical Problem Since a power cable and an electric device are exposed to environmental noise, it is considered that noise is mixed in a measured signal. In the φ-q-n (phase-charge amount-pulse number) characteristic of random noise, it is considered tha