JP2009222537A - Partial discharge detecting method by electromagnetic wave measurement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily determine a partial discharge electromagnetic wave and a noise generated from an electronic device within a distribution panel, and accurately determine the partial discharge electromagnetic wave. <P>SOLUTION: The partial discharge electromagnetic wave signal and the external noise are detected by an antenna 13, amplified, converted into digital signals by an A/D converter 26, and supplied to an electromagnetic wave output signal detecting section 27. The electromagnetic wave output signal detecting section 27 detects and analyzes an electromagnetic wave output signal and an electromagnetic wave spectrum, and stores the detection signal in a first storage 28a. Then, the electromagnetic wave output signal detecting section 27 is connected to an external antenna 14, detects an electromagnetic wave signal, and stores the detection signal in a second storage 28b. Since the detection signals stored in the first and second storage 28a, 28b are the electromagnetic wave output signals inside and outside the distribution panel, a comparison section 29 compares strengths of the signals, and a determination section 30 determines the partial discharge electromagnetic wave and the noise. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for detecting a partial discharge generated from a high-voltage electrical facility or equipment installed in a metal-closed switchboard, and more particularly to a method for detecting a partial discharge by electromagnetic wave measurement.

  Examples of abnormal phenomena that occur in common in high-voltage electrical facilities and equipment include the occurrence of partial discharge due to the effects of manufacturing defects and aging deterioration. In general, if there are minute voids (voids) or peeling parts in the insulating material used for molding equipment, the electric field concentrates on the part during operation, and a weak discharge called partial discharge occurs. To do. Further, partial discharge may occur due to the influence of contamination on the surface of the mold insulator.

  In particular, in the latter case, partial discharge can be prevented by removing the fouling, but partial discharge in the former case cannot be prevented and is not recoverable. If the operation is continued in a state where the partial discharge has occurred, there is a risk that a void or a peeled state may be developed, and there is a risk of eventually resulting in dielectric breakdown.

  Examples of partial discharge generated in electrical equipment (specimen) include air discharge (corona) due to surface contamination of the high-voltage mold site, and discharge generated in defective parts such as cracks, voids, and peeling inside the mold equipment. . There are the following four methods as a partial discharge detection method.

(A) An electrical method (CC method) in which a coupling capacitor (CC) is directly connected to the main circuit of the specimen and the pulse voltage associated with the occurrence of partial discharge is measured.
(B) an electrical method (high frequency CT method) for attaching a high frequency CT to the ground wire (ground wire current method) and measuring a pulse current generated with the occurrence of partial discharge;
(C) a diagnostic measurement method for acoustically detecting elastic wave vibration and discharge sound accompanying partial discharge generation;
(D) The electromagnetic wave emitted with the occurrence of partial discharge is measured (electromagnetic wave detection method).

  The CC method of (a) above captures the charge amount Q due to partial discharge in the specimen TF as a voltage Vd generated at the detection impedance Z in the partial discharge calibration / measurement circuit diagram shown in FIG. When a partial discharge with a charge amount Q occurs in TF, the voltage Vd generated at both ends of the detection impedance Z is the capacitance Ca of the specimen TF, the capacitance of the coupling capacitor Ck, the detection impedance Z, and its frequency characteristics. It cannot be calculated by calculation.

  For this reason, in FIG. 6, a known charge amount Qcal is injected into the specimen TF to adjust the sensitivity of the measuring instrument MI (calibration). In the figure, Cb is a capacitance inserted in series with the defective portion of the specimen TF, and Cc is a capacitance of the defective portion of the specimen TF.

  The high-frequency CT method (b) is a very simple method in which the high-frequency CT is simply attached to the ground line, compared to the method (a) in which partial discharge is directly measured from the voltage of the main circuit. However, it is easily affected by noise mixed in the ground wire, and calibration as a measure of the measured discharge charge amount is difficult, and the partial discharge detection sensitivity is extremely lowered (see, for example, Patent Document 1).

  Furthermore, as a representative example of the above (c), one example is Acoustic Emission (hereinafter referred to as AE method: acoustic method). The AE method is mainly applied as a method of estimating a partial discharge occurrence value by detecting an elastic wave propagating in a solid such as a metal surface by performing a signal processing with a sensor using a piezoelectric element.

  In addition, there is also an acoustic method that uses a piezoelectric element as a sensor to directly capture the ultrasonic waves generated by the occurrence of partial discharge in a parabola, but the target is to detect the corona discharge because it targets the ultrasonic waves emitted into the air. It is said. This technique is applied as a technique for specifying a discharged sound by performing an FFT operation or the like on a collected signal through an amplifier circuit and various filters.

  Furthermore, the above (d) is a method of detecting a partial discharge electromagnetic wave generally using an antenna and a spectrum analyzer, but the influence of environmental electromagnetic waves (hereinafter referred to as noise) such as broadcast waves becomes a problem. (For example, see Patent Documents 2 to 5.)

  In the CC method (a) above, it is necessary to connect a coupling capacitor directly to the specimen for measurement, and a power supply facility for applying the test voltage is required. There is a problem that is necessary.

  The partial discharge measurement by the high-frequency CT method in (b) above is a configuration in which the high-frequency CT is attached to the ground wire of the equipment, but each device and part housed in the switchboard etc. is basically common. Since it is grounded, when a partial discharge is detected, it is difficult to specify the generation position. In addition, since the pulse current added to the leakage current is measured, there is a problem that the partial discharge detection sensitivity is poor compared to the CC method described above.

  In the diagnostic measurement method (AE method) for acoustically detecting elastic wave vibration and discharge sound due to the occurrence of partial discharge in (c) above, the elastic wave due to the discharge phenomenon during operation is detected directly or indirectly. As an indirect detection method, there is a means for attaching the AE sensor 2 to the side wall 1a of the switchboard 1 shown in FIG. Reference numeral 3 denotes an instrument transformer (molded device).

  If the AE sensor 2 attached to the side wall surface 1a as shown in FIG. 7 is used, the elastic wave accompanying the discharge phenomenon inside the switchboard 1 can be detected, but the discharge phenomenon occurs in any part (or which phase) inside. It is difficult to identify whether Further, the influence of noise (white noise) is large, and it is also a problem to extract a signal accompanying a small discharge phenomenon from the noise.

  In particular, an instrument transformer has an iron core, and noise is generated from the iron core to reduce the accuracy of partial discharge detection. As a direct factor of the noise generation source, there are vibration due to the magnetic force acting between the joints and laminations of the iron core and vibration due to the magnetostriction phenomenon of the iron core.

  Further, secondary factors include a resonance phenomenon caused by a frame, an iron core tightening structure, and ambient conditions, and a structure vibration caused by a magnetic force and a magnetostriction phenomenon. Since these vibrations are generated in synchronization with the power supply voltage waveform, they are also mixed in the partial discharge measurement signal by the AE method generated in synchronization with the power supply voltage, and the measured signal is due to partial discharge or due to vibration noise. It is difficult to determine whether something is wrong.

  In addition, in the method of capturing the discharge phenomenon by sound, when applied to an instrument transformer housed in a switchboard, the measurement may be difficult due to a barrier placed in the panel, etc. If it is, opening a barrier or the like is required. In this method, air discharge (corona discharge) can be detected, but partial discharge generated in the mold apparatus cannot be detected. Similar to the AE method, it is also a problem to extract a small discharge sound from noise. Furthermore, it is difficult to clearly grasp from which three-phase transformer the partial discharge is generated from the measurement result.

  The electromagnetic wave detection method (partial discharge detection method) of (d) has an advantage that measurement can be performed in a non-contact manner on a diagnostic object. Further, it is advantageous that a partial discharge generated inside the molding apparatus can be detected from the outside unless it is completely shielded by a grounded iron plate or a metal mesh.

  However, FIG. 8 shows electromagnetic waves emitted by partial discharge generated in electrical equipment and equipment, corona discharge generated in the atmosphere and on the surface of the insulator, and partial discharge generated inside the insulator of the mold equipment. As shown, it generally appears in a band of several tens to several hundreds of MHz.

  FIG. 8 shows an example of a measurement result of electromagnetic waves emitted with corona discharge. For example, in FIG. 8, 30 to 50 MHz, 110 to 160 MHz, and 250 to 400 MHz are partial discharge electromagnetic waves, and 70 to 110 MHz, 170 to 230 MHz, 470 to 500 MHz, and the like are noises such as broadcast waves.

  In the measurement result of FIG. 8, noise due to broadcast waves or the like is also emitted in the same band, so that there is a problem that it is difficult to distinguish between noise and partial discharge electromagnetic waves depending on the field.

In Patent Document 2 and Patent Document 4, two partial discharge detection antennas that detect electromagnetic waves generated when partial discharge occurs in the vicinity of the target electrical device and two noise detection antennas that measure only noise are provided. Is the method. In partial discharge detection by this method, first, a process of setting a plurality of frequency measurement points having a noise level equal to or lower than a specified value by a noise detection antenna is performed. Thereafter, the noise is removed by measuring the partial discharge with the detection antenna at each frequency measurement point determined in this process.
Japanese Patent Laid-Open No. 07-335445 JP 07-333288 A JP 09-113573 A Japanese Patent Laid-Open No. 10-210647 JP 2005-265684 A

  In Patent Documents 2 and 4, the noise detection antenna must be arranged at a position where partial discharge is not detected, but there is a problem that it is difficult to specify the position of the antenna. If the noise detection antenna is too close to the device, partial discharge may be detected. If the distance is too far, the noise output status differs from the position of the partial discharge detection antenna, and the workability is lowered.

  For this reason, when the operation of the target electrical device can be stopped, the device is stopped once, and after the noise is measured, the target electrical device is operated again to measure the partial discharge. In this case, work such as operation and stop of the electrical equipment is added, which takes time and effort, and may further reduce workability.

  In Patent Documents 2 and 4, in order to detect partial discharge, first, noise is measured with a noise detection antenna, and then the circuit is switched to measure partial discharge with the partial discharge detection antenna. For this reason, when there is a time lag between noise measurement and partial discharge measurement, and the noise changes over time, the noise cannot be completely removed, and there is a risk that the noise will be erroneously determined as partial discharge. .

  In addition, since the frequency measurement point where noise was generated is not subject to measurement of partial discharge electromagnetic waves, it cannot be measured no matter how large partial discharge electromagnetic waves are generated at this non-measurement frequency measurement point, There is also a problem that the measurement accuracy is significantly reduced.

  The object of the present invention has been made in view of the above circumstances, and is intended to improve the workability of partial discharge electromagnetic wave detection, facilitate discrimination between partial discharge electromagnetic waves and noise, and perform noise detection and partial discharge electromagnetic wave detection. It is an object of the present invention to provide a partial discharge detection method by electromagnetic wave measurement that can be performed simultaneously and can detect a partial discharge electromagnetic wave without generating a time lag.

In order to achieve the above object, according to a first aspect of the present invention, an electrical device subject to partial discharge detection is disposed on a metal closed type switchboard, a first antenna is installed in the vicinity of the electrical device, and the switchboard A second antenna is installed outside the antenna, and the first and second antennas detect the partial discharge electromagnetic wave from the electric device and the external noise from the outside of the switchboard with the electromagnetic wave output signal detection device, and the partial discharge electromagnetic wave and the external In a method of discriminating from noise,
After the partial discharge electromagnetic wave and the external noise detected by the first antenna are detected by the electromagnetic wave output signal detection unit of the electromagnetic wave output signal detection device and stored in the first storage unit, the electromagnetic wave output signal detection is detected by the second antenna. After the apparatus is connected and the partial discharge electromagnetic wave and the external noise are detected by the electromagnetic wave output signal detection unit, the partial discharge electromagnetic wave and the external noise are stored in the second storage unit and stored in the first and second storage units. Are compared, and when the detection output of the first antenna is larger than the detection output of the second antenna, it is determined that the intensity is a partial discharge electromagnetic wave.

  The invention according to claim 2 is the invention according to claim 1, wherein the difference in intensity between the partial discharge electromagnetic wave stored in the first and second storage units and the external noise is compared, and the difference is a preset threshold value. At this time, it is characterized in that it is a partial discharge electromagnetic wave.

According to a third aspect of the present invention, an electrical device subject to partial discharge detection is arranged on a metal closed type distribution board, a first antenna is installed in the vicinity of the electric equipment, and a second antenna is installed outside the distribution board. A method for determining a partial discharge electromagnetic wave and an external noise by installing and detecting a partial discharge electromagnetic wave from the electrical device and an external noise from the outside of the switchboard with an electromagnetic wave output signal detection device at the same time by the first and second antennas In
After detecting the partial discharge electromagnetic wave and the external noise simultaneously detected by the first antenna and the second antenna by the electromagnetic wave output signal detection unit of the electromagnetic wave output signal detection device separately connected to the first and second antennas, respectively. The intensity of the detected partial discharge electromagnetic wave and the external noise stored separately in the first and second storage units are compared, and the detection output at the first antenna is the second based on the comparison result. When the output is larger than the detection output of the antenna, it is determined that the electromagnetic wave is a partial discharge electromagnetic wave.

  According to a fourth aspect of the present invention, in the third aspect, the difference in intensity between the partial discharge electromagnetic wave stored in the first and second storage units and the external noise is compared, and the difference is a preset threshold value. At this time, it is characterized in that it is a partial discharge electromagnetic wave.

  According to the present invention, since the noise detection antenna is not used, there is an advantage that the problem of specifying the antenna installation position does not occur, and the partial discharge can be measured without stopping the operation of the target electric device. There is an advantage that the operation time can be shortened because the operation such as the operation stop is not performed and the labor is not required. As a result, workability can be improved.

  Further, according to the present invention, it is possible to easily discriminate external noise by comparing the magnitude and difference of the electromagnetic wave detection output by utilizing the influence of metal shielding and distance attenuation in electromagnetic measurement of two points inside and outside the panel. Can do.

  Furthermore, according to the present invention, even at a frequency measurement point where noise has occurred, if the electromagnetic wave output due to the partial discharge is sufficiently large with respect to noise, the partial discharge can be detected also at this frequency measurement point. There is.

  In addition, according to the present invention, noise detection and partial discharge detection are measured at the same time, so there is no time lag, and therefore noise can be reliably detected even when the noise changes over time. There is also an advantage that more accurate measurement is possible.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram applied to the first and second embodiments of the present invention. In FIG. 1, reference numeral 11 denotes a metal closed-type switchboard. The device 12 is housed, and a partial discharge detection antenna 13 is installed in the vicinity of the electrical device 12. An antenna 14 is disposed outside the closed type switchboard 11.

FIG. 2 is a block configuration diagram showing an electromagnetic wave output signal detection device for describing the first and second embodiments of the present invention.
[Embodiment 1]
In FIG. 2, the low noise amplifier 23 is first connected to the antenna 13 among the antennas 13 (14) installed as shown in FIG. 1. The low noise amplifier 23 amplifies a partial discharge electromagnetic wave signal or external noise detected by the antenna 13 and supplies the amplified signal to an amplifier 25 via a band-pass filter (BPF) 24, where the signal is amplified again.

  The output of the amplifier 25 is converted into a digital signal by an analog signal / digital signal converter (A / D converter) 26 and supplied to the electromagnetic wave output signal detection unit 27, and the electromagnetic wave output signal is detected by the detection unit 27. At the same time, the electromagnetic spectrum is also detected and analyzed. The signal detected by the detection unit 27 is stored in the first storage unit 28a.

  Next, the electromagnetic wave output signal detection device shown in FIG. 2 is connected to the antenna 14 outside the closed type switchboard 11 and the electromagnetic wave signal is detected by the electromagnetic wave output signal detection unit 27 as described above. The detection signal at this time is stored in the second storage unit 28b.

  Since the detection signals stored in the first and second storage units 28a and 28b are electromagnetic wave output signals inside and outside the closed type switchboard 11, the intensity of the signals is different from the following. This is because the closed type switchboard 11 is made of metal, and the inside and outside of the panel are partitioned by a metal plate, and the closed type switchboard 11 has a through-hole such as a vent, so that the electromagnetic wave is completely transmitted. Can't shield. For this reason, electromagnetic waves are received with some attenuation between the inside and outside of the closed type switchboard 11.

FIGS. 4A and 4B are characteristic diagrams showing the intensity of the electromagnetic wave output signal inside and outside the closed type switchboard 11. As is clear from FIGS. 4A and 4B, the intensity of the external noise N from the outside of the closed type switchboard 11 is the same level as the intensity of the electromagnetic wave output signals inside and outside the panel. The inside is a little lower. As shown in the difference H _N.

On the other hand, the partial discharge electromagnetic wave generated from the electrical device 12 inside the panel is affected by both the shielding by the metal plate and the attenuation of the signal by moving away from the generation source. For this reason, the intensity of the partial discharge electromagnetic wave output signal from the inside of the panel is smaller in the partial discharge PD outside the panel than the intensity of the electromagnetic wave output signal inside and outside the panel. As shown in the figure, the difference _HPD is obtained.

  Therefore, by comparing the intensity of the electromagnetic wave output signal stored in the first and second storage units 28a and 28b shown in FIG. It becomes possible to do.

Next, discrimination by “large / small” comparison of detection outputs by the antennas 13 and 14 and discrimination by “difference” will be described.
[Distinction by comparison of magnitude of detection output by antenna]
In the first embodiment, the magnitude of the output of the electromagnetic wave signal received by the antenna 13 and the electromagnetic wave signal received by the antenna 14 is compared, and if the output of the antenna 13> the output of the antenna 14, it is determined that it is a partial discharge electromagnetic wave signal. Thus, the output value of the antenna 13 remains. If the output of the antenna 13 <= the output of the antenna 14, it is determined that the noise is external noise, and the detection output of the antenna 13 is deleted. By sequentially performing this at the measured frequency, the partial discharge electromagnetic wave and the external noise can be distinguished.

  Actually, considering the influence of non-simultaneous measurement inside and outside the panel, measurement error, etc., the margin value “K1” is set, and the output of the antenna 13> the output of the antenna 14 + the margin value “K1” is set as the partial discharge electromagnetic wave. The output of the antenna 13 <= the output of the antenna 14 + the margin value “K1” is determined as the external noise. By sequentially performing this at the measured frequency, the partial discharge electromagnetic wave and the external noise can be distinguished.

By performing the operation as described above, the external noise is eliminated and the partial discharge electromagnetic wave remains. The presence or absence of partial discharge is determined from the remaining electromagnetic spectrum.
[Distinction based on difference in detection output by antenna]
Advance the threshold value "K2" is set smaller than the panel inner and outer difference H _PD of large partial discharge electromagnetic wave from the panel inner and outer difference H _N external noise. The difference between the output of the antenna 13 and the output of the antenna 14 is calculated, and if this value is equal to or greater than the set threshold “K2”, it is determined as a partial discharge electromagnetic wave, and the output value of the antenna 13 is left. If it is equal to or less than the set threshold “K2”, it is determined as external noise and the output of the antenna 13 is deleted. By sequentially performing this at the measured frequency, the partial discharge electromagnetic wave and the external noise are discriminated.

  By performing the operation as described above, the external noise is eliminated and the partial discharge electromagnetic wave remains. The presence or absence of partial discharge is determined from the remaining electromagnetic spectrum.

The operation and analysis as described above may be performed by a computer.
[Embodiment 2]
Next, a second embodiment of the present invention will be described. In the second embodiment, electromagnetic waves are simultaneously detected and compared between the inside and outside of the closed type switchboard 11 shown in FIG.

  FIG. 3 is a block diagram showing the second embodiment of the present invention, and the same parts as those in FIG.

  In FIG. 3, an antenna 13 installed in the vicinity of the target electrical device 12 inside the panel and an antenna 14 installed outside the panel include low noise amplifiers 23 and 23 ′, bandpass filters 24 and 24 ′, and amplifiers 25 and 25. 'Analog signal / digital signal converters 26, 26' and electromagnetic wave output signal detectors 27, 27 'are connected separately.

  The detection outputs of the electromagnetic wave output signal detection units 27 and 27 'are input to and stored in the A storage unit 28 and the B storage unit 28'. The outputs of both storage units 28.28 'are compared with the magnitude of the output or the difference between the outputs via the comparison unit 29 and supplied to the determination unit 30 to determine the presence or absence of partial discharge.

  According to the second embodiment, electromagnetic waves inside and outside the panel are detected at the same time. Therefore, signals detected by the antenna 13 and the antenna 14 are simultaneously analyzed, and whether or not partial discharge has occurred is determined from the analysis result.

  Here, a method for determining whether or not partial discharge has occurred from the above analysis results will be described with reference to FIGS. 5 (a) and 5 (b) show spectrum analyzers in the first embodiment, in which a display is connected to the output of the electromagnetic wave output signal detection unit 27, or in place of the A / D converter 26 and the electromagnetic wave output signal detection unit 27. Is a characteristic diagram in which the electromagnetic waves inside and outside the closed type switchboard 11 are measured, FIG. 5 (a) is an electromagnetic wave characteristic diagram of the antenna 13 installed inside the panel, and FIG. 5 (b) is installed outside the panel. It is the electromagnetic wave characteristic figure in the antenna 14 which did.

  As described with reference to FIGS. 4A and 4B, the intensity of the external noise is almost the same between the inside and outside of the board, or slightly lower inside the board. Further, the partial discharge electromagnetic waves generated inside the panel are considerably attenuated outside the panel.

  From the above, comparing FIGS. 5 (a) and 5 (b) with the magnitude of the detection output, the result is that, as shown in FIG. 5 (c), the external noise from the outside of the panel disappears and the electrical Since the partial discharge electromagnetic wave generated from the device remains, the partial discharge electromagnetic wave can be determined.

  Further, when FIGS. 5A and 5B are discriminated based on the difference between the detection outputs, the result is almost the same as the comparison based on the magnitude of the detection outputs as shown in FIG. 5D.

  Although some external noise has changed over time, the external noise remains. However, if simultaneous detection of electromagnetic waves inside and outside the panel in the second embodiment is performed, this influence is reduced, and more The discrimination can be made with high accuracy. From this result, the first and second embodiments are effective in removing external noise and determining whether or not partial discharge has occurred.

The schematic block diagram applied to Embodiment 1, 2 of this invention. 1 is a block configuration diagram showing Embodiment 1 of the present invention. The block block diagram which shows Embodiment 2 of this invention. (A), (b) is a characteristic view which shows the intensity | strength of the electromagnetic wave output signal inside the panel of a closed type switchboard, and the exterior. (A)-(d) is the characteristic view which measured the electromagnetic wave inside the panel of a closed type switchboard, and the exterior. Partial discharge calibration and measurement circuit diagram. The partial discharge measurement block diagram by an AE sensor. The characteristic figure of the frequency spectrum of the electromagnetic wave measurement result emitted with the corona discharge.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Metal closed type switchboard 12 ... Target electric equipment 13, 14 ... Antenna 23 ... Low noise amplifier 24 ... Band-pass filter (BPF)
25 ... Amplifier 26 ... Analog signal / digital signal conversion unit 27 ... Electromagnetic wave output signal detection unit 28a ... First storage unit
28b ... 2nd memory | storage part 29 ... Comparison part 30 ... Determination part

Claims (4)

An electric device subject to partial discharge detection is arranged on a metal closed type distribution board, a first antenna is installed in the vicinity of the electric equipment, a second antenna is installed outside the distribution board, and the first and second antennas are arranged. In the method of detecting the partial discharge electromagnetic wave from the electrical equipment and the external noise from the outside of the switchboard with an electromagnetic wave output signal detection device, and discriminating between the partial discharge electromagnetic wave and the external noise,
After the partial discharge electromagnetic wave and the external noise detected by the first antenna are detected by the electromagnetic wave output signal detection unit of the electromagnetic wave output signal detection device and stored in the first storage unit,
The electromagnetic wave output signal detection device is connected to the second antenna, and the partial discharge electromagnetic wave and the external noise are detected by the electromagnetic wave output signal detection unit, and then stored in the second storage unit,
When the magnitudes of the intensity of the partial discharge electromagnetic wave stored in the first and second storage units and the intensity of the external noise are compared, and the detection output at the first antenna is larger than the detection output at the second antenna, the partial discharge A partial discharge detection method based on electromagnetic wave measurement, characterized in that it is an electromagnetic wave. In the partial discharge detection method by the electromagnetic wave measurement of Claim 1,
Comparing the difference in intensity between the partial discharge electromagnetic wave stored in the first and second storage units and the external noise, and determining that the difference is equal to or greater than a preset threshold value, the partial discharge electromagnetic wave is a partial discharge electromagnetic wave. A partial discharge detection method by electromagnetic wave measurement. An electric device subject to partial discharge detection is arranged on a metal closed type distribution board, a first antenna is installed in the vicinity of the electric equipment, a second antenna is installed outside the distribution board, and the first and second antennas are arranged. In the method of simultaneously detecting the partial discharge electromagnetic wave from the electrical equipment and the external noise from the outside of the switchboard with an electromagnetic wave output signal detection device, and discriminating between the partial discharge electromagnetic wave and the external noise,
After detecting the partial discharge electromagnetic wave and the external noise simultaneously detected by the first antenna and the second antenna by the electromagnetic wave output signal detection unit of the electromagnetic wave output signal detection device separately connected to the first and second antennas, respectively. , Separately stored in the first and second storage units,
When the detected partial discharge electromagnetic wave stored separately and the magnitude of the intensity of the external noise are compared, and when the detection output at the first antenna is larger than the detection output at the second antenna, the partial discharge electromagnetic wave is A partial discharge detection method by electromagnetic wave measurement, characterized in that it is present. In the partial discharge detection method by electromagnetic wave measurement of Claim 3,
Comparing the difference in intensity between the partial discharge electromagnetic wave stored in the first and second storage units and the external noise, and determining that the difference is equal to or greater than a preset threshold value, the partial discharge electromagnetic wave is a partial discharge electromagnetic wave. A partial discharge detection method by electromagnetic wave measurement.

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