JP6837378B2 - Partial discharge detection device and partial discharge detection method - Google Patents

Description

The present disclosure relates to a partial discharge detection device and a partial discharge detection method for detecting the occurrence of a partial discharge by detecting an electromagnetic wave accompanying the occurrence of the partial discharge.

A method of detecting the occurrence of a partial discharge by receiving an electromagnetic wave accompanying the occurrence of a partial discharge with an antenna is generally used. In such a partial discharge detection method, it is a problem to determine the source of the partial discharge, and further to distinguish between the external noise received by the antenna and the electromagnetic wave accompanying the partial discharge.

For example, in the method for searching for a partial discharge source disclosed in Japanese Patent Application Laid-Open No. 2005-98800 (Patent Document 1), the frequency characteristics of electromagnetic waves differ depending on the type of partial discharge source. Distinguish between sources of discharge. Specifically, according to this document, if the partial discharge source is "in oil", the frequency characteristic of the electromagnetic wave has a peak near 150 MHz. If the partial discharge is derived from the "overhead wire" corona discharge, the frequency characteristic of the electromagnetic wave will have a peak near 50 MHz. If the partial discharge source is "in the insulator surface", the frequency characteristic of the electromagnetic wave has a peak near 25 MHz.

The partial discharge detection device disclosed in Japanese Patent Application Laid-Open No. 2014-169978 (Patent Document 2) utilizes the technique described in Patent Document 1 described above and distinguishes it from external noise based on communication waves or broadcast waves. It has the means of. Specifically, the partial discharge detection device of this document includes a filter unit, a peak hold unit, and a determination unit. The filter unit selectively passes an electric signal of a frequency band component of the 150 MHz band from the received voltage of the antenna. The peak hold unit temporarily holds the peak value of the electric signal output from the filter unit. The determination unit outputs a detection signal when the difference value between the level of the electric signal output from the peak hold unit and the level of the electric signal output from the filter unit exceeds a predetermined threshold value.

Japanese Unexamined Patent Publication No. 2005-98800 Japanese Unexamined Patent Publication No. 2014-169978

The inventors of the present invention optimally detect electromagnetic waves in the vicinity of the 150 MHz band used in Patent Documents 1 and 2 above when detecting a partial discharge in oil of an oil-filled bushing. Whether or not it was verified by detecting the radiated electromagnetic waves from the actual oil-filled bushing. Furthermore, by measuring field noise in the environment of a substation where an oil-filled bushing of the actual equipment is installed, a frequency range in which partial discharge can be detected while the S / N (Signal to Noise) ratio is high is examined. did.

This disclosure is based on the above study results, the purpose of which is to detect partial discharge detectors and parts that can detect electromagnetic waves associated with partial discharge in oil of oil-filled bushings in a high S / N ratio. It is to provide a discharge detection method.

The partial discharge detection device according to one embodiment is for detecting a partial discharge in oil of an oil-filled bushing, and includes an antenna, an A / D converter, a Fourier transform unit, and a determination unit. The antenna detects electromagnetic waves coming from the oil-filled bushing. The A / D converter converts the received signal of the antenna into A / D (Analog to Digital). The Fourier transform unit generates an amplitude spectrum by Fourier transforming the A / D-converted received signal. The determination unit determines the presence or absence of partial discharge in the oil of the oil-filled bushing based on the amplitude of the portion of the generated amplitude spectrum corresponding to the specific frequency range of 450 MHz or more and 460 MHz or less.

According to the above embodiment, since the presence or absence of partial discharge is determined based on the amplitude of the portion corresponding to the specific frequency range of 450 MHz or more and 460 MHz or less, the electromagnetic wave accompanying the partial discharge in the oil of the oil-filled bushing is S / S. It can be detected in a state where the N ratio is high.

It is a block diagram which shows the structural example of the partial discharge detection apparatus according to Embodiment 1. FIG. It is a flowchart which shows the procedure of determining the specific frequency range for detecting the electromagnetic wave accompanying a partial discharge. It is a figure which shows typically the step S100 of FIG. It is a figure which shows the detection result of the radiated electromagnetic wave by the partial discharge in oil of an oil-filled bushing. It is a figure which shows the amplitude spectrum of the antenna reception voltage when a partial discharge occurs along the insulator of an oil-filled bushing. It is a figure which shows typically the step S110 of FIG. It is a figure which shows the detection result of the radiated electromagnetic wave accompanying the partial discharge in oil of an oil-filled bushing, and the detection result of the field noise in a field environment. FIG. 7 is an enlarged view showing a portion of FIG. 7 from 100 MHz to 200 MHz. FIG. 7 is an enlarged view showing a portion of FIG. 7 from 400 MHz to 500 MHz. FIG. 5 is a flowchart showing a procedure for detecting a partial discharge in oil of an oil-filled bushing in the partial discharge detection device of the first embodiment. It is a figure which shows typically the mode that the partial discharge detection apparatus 201 according to Embodiment 2 detects a partial discharge in oil of an oil-filled bushing 120. It is a block diagram which shows the structural example of the partial discharge detection apparatus 201 according to Embodiment 2. It is a figure for demonstrating the principle of A / D conversion of an undersampling method. FIG. 5 is a flowchart showing a procedure for detecting a partial discharge in oil of an oil-filled bushing in the partial discharge detection device of the second embodiment.

Hereinafter, each embodiment will be described in detail with reference to the drawings. The same or corresponding parts are designated by the same reference numerals, and the description is not repeated.

Embodiment 1.
[Configuration example of partial discharge detection device]
FIG. 1 is a block diagram showing a configuration example of the partial discharge detection device according to the first embodiment. With reference to FIG. 1, the partial discharge detection device 200 includes an antenna 110, an amplifier 130, an oscilloscope 111, and a personal computer (PC) 112.

The antenna 110 is for receiving electromagnetic waves arriving from the oil-filled bushing, which is the object to be inspected. In this embodiment, a wide band antenna 110 is used. The wideband antenna 110 receives field noise such as broadcast wave and communication wave 123 together with the electromagnetic wave 103 associated with the partial discharge of the inspection object.

The amplifier 130 amplifies the received signal of the antenna 110. If the strength of the received signal of the antenna 110 is sufficient, the amplifier 130 may not necessarily be provided.

The oscilloscope 111 includes an analog-to-digital converter (ADC) 131, a memory 132, and a display unit 133 such as a liquid crystal display.

The A / D converter 131 converts the received signal of the antenna 110 into a digital signal. The sampling frequency fs of the A / D converter 131 is set so that the frequency range required for signal processing can be captured while satisfying the Nyquist condition. Specifically, the sampling frequency fs is set so that the frequency range required for signal processing is smaller than fs / 2, and the frequency region above fs / 2 is cut by a low-pass filter (not shown).

The digitized received signal after A / D conversion is stored in the memory 132 and displayed on the display unit 133. A dedicated signal processing circuit (not shown) may be provided in order to speed up both the processing of the storage in the memory 132 and the processing of the display in the display unit 133.

The computer 112 includes a processor 140, a memory 145, and a display unit 146 such as a liquid crystal display. In the case of the present embodiment, the processor 140 functions as the Fourier transform unit 141 and the determination unit 143 by executing the program stored in the memory 145. The Fourier transform unit 141 generates an amplitude spectrum by performing a discrete Fourier transform on the A / D-converted received signal. The determination unit 143 determines the presence or absence of partial discharge of the inspection object based on the amplitude of the portion of the generated amplitude spectrum corresponding to the specific frequency range.

In the above, an example in which the partial discharge detection device 200 is configured by using a general-purpose oscilloscope 111 and a general-purpose computer 112 is shown. Unlike this, the partial discharge detection device 200 may be integrally configured by a dedicated circuit.

In this embodiment, based on an experiment using a real oil-filled bushing, and further, based on the measurement of field noise in a substation equipped with a real device including the oil-filled bushing, the oil-filled bushing is in oil. A specific frequency range is defined so that the electromagnetic waves associated with the partial discharge in the above can be detected in a state where the S / N ratio is high. Specifically, the specific frequency range is 450 MHz or more and 460 MHz or less. Hereinafter, a method for determining a specific frequency range will be described in detail.

[Method of determining specific frequency range]
FIG. 2 is a flowchart showing a procedure for determining a specific frequency range for detecting an electromagnetic wave associated with a partial discharge. FIG. 3 is a diagram schematically showing step S100 of FIG.

With reference to FIGS. 2 and 3, in step S100, the radiated electromagnetic wave 103 when a partial discharge occurs in the oil of the oil-filled bushing 100, which is the inspection object 100A, is measured in the laboratory environment 105. As the oil-filled bushing 100, one that has been intentionally deteriorated by mixing water is used. The oil-filled bushing 100 is simulated by the power charging device 101. The amount of discharge charge when a partial discharge occurs is measured by the partial discharge measuring device 102. Further, the electromagnetic wave associated with the partial discharge is detected by the partial discharge detection device 200 described with reference to FIG.

FIG. 4 is a diagram showing the detection results of radiated electromagnetic waves associated with partial discharge in oil of an oil-filled bushing. In FIG. 4, the amplitude spectrum of the antenna reception voltage when a partial discharge of the discharge charge amount of 450 pC occurs, and the amplitude spectrum of the reception voltage of the background noise BGN in the laboratory environment 105 when the partial discharge does not occur. It is shown. The vertical axis of FIG. 4 shows a value obtained by converting the voltage amplitude [unit: V] in the 50Ω system into the electric power [unit: dBm].

As shown in FIG. 4, peaks occur in the voltage amplitude near 150 MHz, around 300 MHz, and around 450 MHz. Therefore, these frequency bands are listed as candidates for a specific frequency range.

FIG. 5 is a diagram showing an amplitude spectrum of an antenna reception voltage when a partial discharge occurs along the surface of an oil-filled bushing insulator. As shown in FIG. 5, in the case of partial discharge along the insulator surface, a peak occurs in the amplitude of the received voltage near 50 MHz, and a relatively large amplitude is detected from around 50 MHz to around 400 MHz. Therefore, it is considered difficult to distinguish between a partial discharge in oil and a partial discharge along the insulator surface in the vicinity of 150 MHz and around 300 MHz in the above candidate frequency ranges.

FIG. 6 is a diagram schematically showing step S110 of FIG. With reference to FIGS. 2 and 4, in the next step S110, in the actual environment 125 (substation) in which the actual device 121 (transformer) incorporating the inspection object 120A (oil-filled bushing 120) is installed. , Communication wave 123 and field noise such as broadcast wave are measured. The field noise is measured using the same partial discharge detection device 200 as in step S100 of FIG. In this measurement, the oil-filled bushing 120 is charged with electricity from the main body of the device. However, since the oil-filled bushing 120 is hardly deteriorated, partial discharge does not occur in the oil-filled bushing 120.

In the next step S120, the amplitude spectrum of the antenna reception voltage associated with the partial discharge detected in step S100 and the amplitude spectrum of the antenna reception voltage of the field noise are compared. Thereby, a frequency range having a high S / N ratio suitable for detecting the occurrence of a partial discharge in the oil of the oil-filled bushing 120 is determined.

FIG. 7 is a diagram showing a detection result of radiated electromagnetic waves due to a partial discharge in oil of an oil-filled bushing and a detection result of field noise in a field environment. The amplitude spectrum of the received voltage of the electromagnetic wave accompanying the partial discharge of the discharge charge amount of 450 pC is shown by a solid line, and the field noise is shown by a broken line. The field noise is plotted as the maximum value for each frequency among the values measured at the five substations.

As shown in FIG. 7, the peak value of the received voltage of the radiated electromagnetic wave due to the partial discharge in the vicinity of 300 MHz is about the same as the value of the field noise. On the other hand, the peak value of the received voltage of the radiated electromagnetic wave due to the partial discharge in the vicinity of 150 MHz and the vicinity of 450 MHz is larger than the value of the field noise.

FIG. 8 is an enlarged view showing a portion of FIG. 7 from 100 MHz to 200 MHz. FIG. 9 is an enlarged view showing a portion of FIG. 7 from 400 MHz to 500 MHz.

As shown in FIG. 8, the reception voltage of the electromagnetic wave due to the partial discharge is larger than the reception voltage of the field noise at 144 MHz to 151 MHz. However, the difference is about 3 dBm. On the other hand, as shown in FIG. 9, the difference between the received voltage of the electromagnetic wave due to the partial discharge and the received voltage of the field noise in the range of 450 MH or more and 460 MHz or less is relatively large, about 10 dBm.

From the above examination, by selecting the range of 450 MH or more and 460 MHz or less as a specific frequency range, it becomes easy to distinguish between the partial discharge in the oil and the field noise of the oil-filled bushing 120, and the partial discharge in the oil. It is thought that it will be easier to distinguish between the and partial discharge along the insulator surface.

[Procedure for detecting partial discharge in oil of oil-filled bushing]
FIG. 10 is a flowchart showing a procedure for detecting a partial discharge in oil of an oil-filled bushing in the partial discharge detection device of the first embodiment. Hereinafter, with reference to FIGS. 2, 6, and 10, the procedure for detecting an electromagnetic wave associated with a partial discharge will be described by summarizing the explanations so far.

In step S200, the partial discharge detection device 200 receives the radiated electromagnetic wave coming from the direction of the oil-filled bushing 120, which is the inspection object 120A, by the antenna 110. However, in the case of the first embodiment, since the antenna 110 uses a wideband antenna, many field noises such as broadcast wave and communication wave 123 other than the electromagnetic wave 103 associated with the partial discharge of the inspection object 120A are also caused by the antenna 110. Received.

In the next step S210, the A / D converter 131 A / D converts the received signal of the antenna 110. In the next step S220, the Fourier transform unit 141 generates an amplitude spectrum by Fourier transforming the A / D-converted received signal.

In the next step S230, the determination unit 143 determines the presence or absence of partial discharge in the oil of the oil-filled bushing based on the amplitude of the portion of the generated amplitude spectrum corresponding to the specific frequency range of 450 MHz or more and 460 MHz or less. judge. More specifically, by comparing the signal amplitude of the above-mentioned specific frequency range obtained at the time of inspection with the signal amplitude of the specific frequency range obtained in advance when partial discharge has not occurred, the oil at the time of inspection The presence or absence of partial discharge in the oil of the incoming bushing is determined.

[effect]
As described above, in the partial discharge detection device 200 of the first embodiment, the partial discharge is generated based on the presence or absence of the amplitude based on the amplitude of the portion corresponding to the specific frequency range of 450 MHz or more and 460 MHz or less in the amplitude spectrum of the received signal. The presence or absence of is determined. Thereby, the electromagnetic wave accompanying the partial discharge in the oil of the oil-filled bushing can be detected in a state where the S / N ratio is high.

Embodiment 2.
In the second embodiment, a component corresponding to a specific frequency range of 450 MHz or more and 460 MHz or less is extracted from the analog signal received by the antenna by using a bandpass filter. Therefore, it is not necessary to perform the Fourier transform after the A / D transform. Further, by performing the A / D conversion by the undersampling method, the components in the specific frequency range of the received signal are automatically down-converted to the low frequency signal.

Further, in combination with the above, the antenna may be a narrow band directional antenna. In this case, the bandwidth of the antenna (also referred to as the bandwidth) is set to include the above-mentioned specific frequency range. Hereinafter, a specific description will be given with reference to the drawings.

[Configuration of partial discharge detector]
FIG. 11 is a diagram schematically showing how the partial discharge detection device 201 according to the second embodiment detects the partial discharge of the oil-filled bushing 120 in oil.

With reference to FIG. 11, whether or not a partial discharge has occurred in the oil of the oil-filled bushing 120, which is the inspection object 120A, in the actual environment 125 (substation) in which the actual equipment 121 including the inspection object 120A is installed. Is detected by the partial discharge detection device 201. The oil-filled bushing 120 is attached to the device main body 122 (for example, a transformer) of the actual device 121.

A narrow band directional antenna 150 may be used as the antenna of the partial discharge detection device 201. In this case, the bandwidth of the directional antenna 150 includes the above specific frequency range. As the directional antenna 150, a Yagi-Uda antenna, a horn antenna, or the like can be used.

Further, the partial discharge detection device 201 may further include a telescope 151 that directs the field of view in the directional direction of the directional antenna 150. In this case, the directional direction of the directional antenna 150 can be directed toward the oil-filled bushing 120 by capturing the oil-filled bushing 120, which is the inspection object 120A, using the telescope 151.

FIG. 12 is a block diagram showing a configuration example of the partial discharge detection device 201 according to the second embodiment. The block diagram of FIG. 12 corresponds to the block diagram of FIG. 1 of the first embodiment.

Specifically, the partial discharge detection device 201 of FIG. 12 is different from the partial discharge detection device 200 of FIG. 1 in that a narrow band directional antenna 150 is provided instead of the wide band antenna 110. As a result, the central beam direction of the directional antenna 150 can be directed to the oil-filled bushing 120, which is the inspection object 120A, so that the reception rate of field noise is reduced and the electromagnetic wave accompanying the partial discharge of the inspection object 120A is more reliable. Can be detected.

The narrow-band directional antenna 150 can also be applied to the partial discharge detection device 200 of the first embodiment. Conversely, the wideband antenna 110 can also be used in the partial discharge detection device 201 of the second embodiment.

The partial discharge detection device 201 of FIG. 12 is different from the partial discharge detection device 200 of FIG. 1 in that a bandpass filter 152 is further provided between the directional antenna 150 and the A / D converter 131. The bandpass filter 152 is for extracting an antenna reception signal in a specific frequency range of 450 MHz or more and 460 MHz or less. Therefore, the center frequency fc of the bandpass filter 152 is 455 MHz, and the bandwidth fb of the bandpass filter 152 is 10 MHz. By providing the bandpass filter 152 through which the received signal in the specific frequency range is passed, the need for the Fourier transform unit 141 is eliminated.

Further, the partial discharge detection device 201 of FIG. 12 is different from the partial discharge detection device 200 of FIG. 1 in that the A / D converter 131 performs A / D conversion of the undersampling method. Undersampling is to sample a band-limited high-frequency signal at a low-frequency sampling frequency fs. Thereby, the band-limited high-frequency signal can be converted into a low-frequency signal in the range of 0 to fs / 2.

FIG. 13 is a diagram for explaining the principle of A / D conversion of the undersampling method. In the following description, the center frequency of the bandpass filter 152 is fc, and the bandwidth is fb. Let the sampling frequency be fs.

With reference to FIG. 13, in the undersampling method, the frequency fs / 2, which is half the sampling frequency fs, is set to be larger than the bandwidth fb of the bandpass filter (preferably about twice the bandwidth fb). Further, the frequency that is an integral multiple (3 times in the case of FIG. 13) of the sampling frequency fs is set to be slightly smaller than the lower limit frequency of the band-limited high frequency signal. As a result, the frequency of the received signal is converted into the range of 0 to fs / 2 by aliasing. At this time, since the band of the received signal is limited by the bandpass filter, the signals folded back by the aliasing do not overlap each other. By using the A / D conversion of the undersampling method in this way, the configuration of the analog circuit can be simplified.

[Partial discharge detection procedure]
FIG. 14 is a flowchart showing a procedure for detecting a partial discharge in oil of an oil-filled bushing in the partial discharge detection device of the second embodiment. Hereinafter, with reference to FIGS. 11, 12, and 14, the procedure for detecting an electromagnetic wave associated with a partial discharge will be described by summarizing the explanations so far.

In step S300, the directional antenna 150 receives the radiated electromagnetic wave coming from the direction of the oil-filled bushing 120, which is the inspection object 120A. The telescope 151 is used to direct the directivity direction of the directional antenna 150 toward the oil-filled bushing 120 in advance.

In the next step S310, the bandpass filter 152 is used to extract a component in a specific frequency range of 450 MHz or more and 460 MHz or less from the received signal of the directional antenna 150.

In the next step S320, the A / D converter 131 converts the component in the specific frequency range into a low frequency signal by A / D conversion by the undersampling method.

In the next step S330, the determination unit 143 determines the presence or absence of partial discharge in the oil of the oil-filled bushing based on the amplitude of the low-frequency signal described above. More specifically, by comparing the amplitude of the above-mentioned low-frequency signal obtained at the time of inspection with the amplitude of the above-mentioned low-frequency signal obtained in advance when partial discharge has not occurred, the oil at the time of inspection The presence or absence of partial discharge in the oil of the incoming bushing is determined.

[effect]
As described above, according to the partial discharge detection device 201 of the second embodiment, the bandpass filter 152 for extracting the component of the specific frequency range of 450 MHz or more and 460 MHz or less of the antenna received signal is provided, and the band is limited as described above. The antenna reception signal is A / D converted by the undersampling method. This has the advantage that the configuration of the analog circuit can be simplified.

Further, by using the narrow band directional antenna for detecting the electromagnetic wave accompanying the partial discharge, the central beam direction of the directional antenna 150 can be directed to the oil-filled bushing 120 which is the inspection object 120A. As a result, the reception rate of field noise can be reduced, and the electromagnetic wave associated with the partial discharge of the inspection object 120A can be detected more reliably.

The embodiments disclosed this time should be considered to be exemplary and not restrictive in all respects. The scope of the present invention is shown by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope equivalent to the claims.

100, 120 oil-filled bushing, 100A, 120A inspection object, 101 power supply device, 102 partial discharge measuring instrument, 103 electromagnetic wave, 105 laboratory environment, 110 antenna, 111 oscilloscope, 112 computer, 121 actual equipment, 122 equipment body, 123 communication wave, 125 field environment, 131 A / D converter, 140 processor, 141 Fourier transform unit, 143 judgment unit, 150 directional antenna, 151 telescope, 152 band path filter, 200, 201 partial discharge detector.

Claims (12)

A partial discharge detection device for detecting partial discharge in oil of an oil-filled bushing.
An antenna for detecting electromagnetic waves coming from the oil-filled bushing,
An A / D converter that A / D (Analog to Digital) converts the received signal of the antenna,
A Fourier transform unit that generates an amplitude spectrum by Fourier transforming the A / D-converted received signal,
A portion including a determination unit for determining the presence or absence of partial discharge in the oil of the oil-filled bushing based on the amplitude of the portion of the generated amplitude spectrum corresponding to a specific frequency range of 450 MHz or more and 460 MHz or less. Discharge detector. A partial discharge detection device for detecting partial discharge in oil of an oil-filled bushing.
An antenna for detecting electromagnetic waves coming from the oil-filled bushing,
A bandpass filter that extracts components in a specific frequency range of 450 MHz or more and 460 MHz or less from the received signal of the antenna.
An A / D converter that converts a component in the specific frequency range into a low-frequency signal by A / D conversion by an undersampling method.
A partial discharge detection device including a determination unit for determining the presence or absence of partial discharge in oil of the oil-filled bushing based on the amplitude of the low-frequency signal. The partial discharge detection device according to claim 1 or 2, wherein the bandwidth of the antenna includes the specific frequency range. The partial discharge detection device according to any one of claims 1 to 3, wherein the antenna has directivity. The partial discharge detection device according to claim 4, further comprising a telescope whose field of view is directed in the directivity direction of the antenna. The determination unit determines the presence or absence of partial discharge of the oil-filled bushing at the time of the inspection by comparing the amplitude obtained at the time of inspection with the amplitude obtained in advance when the partial discharge has not occurred. , The partial discharge detection device according to any one of claims 1 to 5. It is a partial discharge detection method for detecting a partial discharge in oil of an oil-filled bushing.
The step of detecting the electromagnetic wave coming from the oil-filled bushing with an antenna and
A step of A / D conversion of the received signal of the antenna,
A step of generating an amplitude spectrum by Fourier transforming the A / D-converted received signal, and
A partial discharge including a step of determining the presence or absence of a partial discharge in the oil of the oil-filled bushing based on the amplitude of the portion of the generated amplitude spectrum corresponding to a specific frequency range of 450 MHz or more and 460 MHz or less. Detection method. It is a partial discharge detection method for detecting a partial discharge in oil of an oil-filled bushing.
The step of detecting the electromagnetic wave coming from the oil-filled bushing with an antenna and
A step of extracting a component in a specific frequency range of 450 MHz or more and 460 MHz or less from the received signal of the antenna by a bandpass filter, and a step of extracting the component.
A step of converting a component in the specific frequency range into a low frequency signal by A / D conversion by an undersampling method, and
A method for detecting partial discharge, comprising: determining the presence or absence of partial discharge in oil of the oil-filled bushing based on the amplitude of the low-frequency signal. The partial discharge detection method according to claim 7 or 8, wherein the bandwidth of the antenna includes the specific frequency range. The partial discharge detection method according to any one of claims 7 to 9, wherein the antenna has directivity. 10. The partial discharge detection method further includes a step of directing the directivity direction of the antenna toward the oil-filled bushing by capturing the oil-filled bushing with a telescope whose field of view is directed in the directivity direction of the antenna. The partial discharge detection method according to. Any one of claims 7 to 11, wherein the step of determining the presence or absence of the partial discharge includes a step of comparing the amplitude obtained at the time of inspection with the amplitude obtained in advance when the partial discharge has not occurred. The partial discharge detection method according to the section.

Images