JP2019045459A - Partial discharge detection device and partial discharge detection method - Google Patents

Abstract

To provide a partial discharge detection device that consists of a plurality of box bodies connected to various electric power supply systems and electric power equipment to superpose large noise, and that detects a partial discharge with high sensitivity to find partial discharge generation sources in box body units.SOLUTION: A partial discharge detection device comprises an extraction part and a determination part. The extraction part extracts a signal of first band (hundreds of MHz band) and a signal of second band (1-20 MHz band) from detection signals of respective surface potentials detected by a plurality of electrodes fixed to a plurality of box bodies accommodating power distribution circuits connected to a power supply system. The determination part detects generation timing of a partial discharge based upon a signal of first band (hundreds of MHz band) and a signal of second band (1-20 MHz band) of each electrode, and specifies a box body as a partial discharge generation source based upon a plurality of first band (hundreds of MHz band) detected by different electrodes.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a partial discharge detection device and a partial discharge detection method for detecting partial discharge generated in a power device with high sensitivity.

  There is a power device (hereinafter referred to as "switch gear") in which a circuit breaker or the like is housed in a metal box together with a protective relay in order to open / close a high voltage distribution line or protect it from an accident. Since this switchgear can not diagnose deterioration or failure of internal devices by visual inspection from the outside of the box, it is usually performed to detect partial discharge generated inside the box.

  2. Description of the Related Art Conventionally, as an electric power apparatus for storing a circuit breaker or the like in a box such as a switchgear, a plurality of partial discharge sensors are attached to the box to identify a position where partial discharge occurs. The partial discharge sensor detects a signal due to a partial discharge pulse propagating through a stray capacitance, and can also specify a three-dimensional position from the time difference until reaching it (see, for example, Patent Document 1).

  On the other hand, in a switchgear in which an electrical member such as a main circuit conductor is molded with an insulating material, a plurality of electrodes for detecting the surface potential are provided on the surface of the ground layer. It is known that the partial discharge is detected by subtracting the surface potential of the measurement electrode from the reference electrode to determine the potential difference (see, for example, Patent Document 2).

  In addition, a pair of electrodes for detecting the surface potential is prepared, one of the electrodes is attached to the surface of the ground layer, the other electrode is disposed in noncontact with the ground layer, and these outputs are differentially divided to obtain an S / N ratio. It is known to improve (see, for example, Patent Document 3).

  In these conventional partial discharge detection devices, a box or a mold member is attached to a single component to improve the specification of the generation position of partial discharge generated inside and the detection sensitivity.

  By the way, the switch gear as described above is often configured by arranging a plurality of box bodies in a row board (arranging and arranging) in order to configure a complicated power system. Since the switchgear in a row is connected to another power system or connected to a power device such as a power converter or motor, complex noise (BGN) is generated and intruded and superimposed on the power supply signal. Ru.

JP, 2011-149896, A JP 2012-220209 A JP 2012-220208 A

  In such a switchgear, that is, in a power device, there is a limit in removing noise with different frequency components and power, and partial discharge is detected in areas where noise is abundant and the location of partial discharge ( It is difficult to stop the box. For this reason, what can be detected with high sensitivity the partial discharge of the electric power apparatus by which the box body which complex noise tends to penetrate | invade were installed in a row is desired.

  The present invention has been made to solve such problems, and it is possible to increase partial discharge in a power device configured of a plurality of box bodies that are connected to a power supply system and accommodate a distribution circuit on which large noise is superimposed. An object of the present invention is to provide a partial discharge detection device and a partial discharge detection method capable of detecting sensitivity and stopping a partial discharge source per box unit.

  The partial discharge detection device of the present invention includes an extraction unit and a determination unit. The extraction unit is a first detection signal of surface potentials detected by a plurality of electrodes attached to each box body in an electric power apparatus in which a plurality of box bodies containing a plurality of boxes housing power distribution circuits connected to the power supply system are detected. The signal of the band and the signal of the second band are extracted. The determination unit detects the generation timing of the partial discharge based on the signal of the first band and the signal of the second band for each electrode, and the partial based on the plurality of signals of the first band extracted for each electrode Identify the discharge source box.

FIG. 1 is a diagram showing a schematic configuration of a partial discharge detection system according to one embodiment. It is a figure which shows the structure of the partial discharge detection apparatus of the partial discharge detection system of FIG. It is a figure which shows the structure of the signal processing part (1st Embodiment) of the partial discharge detection apparatus of FIG. It is a figure which shows the correspondence of the frequency of a surface potential detection signal, and a signal level. It is a figure which shows the high frequency signal and low frequency signal which are extracted from a detection signal for every box. It is a figure which shows a mode that partial discharge is specified from a detection signal. It is a figure which shows the other structural example (2nd Embodiment) of a signal processing part. It is a figure which shows the structure of the other structural example (3rd Embodiment) of a signal processing part.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
First Embodiment
The partial discharge detection system of the first embodiment will be described with reference to FIGS. 1 to 6. FIG. 1 is a view showing a schematic configuration of a partial discharge detection system according to the first embodiment, FIG. 2 is a view for explaining a configuration of a partial discharge detection device of the partial discharge detection system of FIG. FIG. 4 illustrates the configuration of the signal processing unit of the apparatus, FIG. 4 illustrates the correspondence between the signal level of the power supply signal and the frequency, and FIG. 5 illustrates high frequency signals and low frequency signals extracted from detection signals for each box. FIG. 6 is a view showing how a partial discharge is specified from a detection signal.

  As shown in FIG. 1, the partial discharge detection system according to the first embodiment includes a plurality of first to n-th box bodies 1 a to 1 n housing power distribution circuits such as circuit breakers and main circuit conductors. Switch gear 1 as the first to nth electrodes 2a to 2n as sensor electrodes attached to each of the box bodies 1a to 1n, and wiring to the first to nth electrodes 2a to 2n And a partial discharge detection device 3 connected via a coaxial cable or the like.

  The plurality of first to n-th box bodies 1a to 1n are arranged in a substantially straight line in a horizontal row with the opening / closing parts such as doors facing the front (also referred to as juxtaposition, row installation, etc.) A predetermined power supply system is configured by the accommodated power distribution circuit.

  In the first to n-th box bodies 1a to 1n, the case is composed of a front plate, a ceiling plate, a back plate, a floor plate, and a side plate, and any plate surface is provided with the first to n-th electrodes 2a to 2n. Is fixed in contact. For this reason, each of a front board, a ceiling board, a back board, a floor board, and a side board is called a composition board which constitutes an individual box. The component board is connected to a ground bus 5 connected (grounded) to a ground pole 6 (hereinafter referred to as “ground 6”). The ground bus bar 5 is disposed below the first to n-th box bodies 1a to 1n as wiring common to the respective box bodies.

  The first to n-th electrodes 2a to 2n detect the surface potential via floating capacitances formed between the first to n-th power distribution circuits respectively housed in the first to nth box bodies 1a to 1n. That is, the first to n-th electrodes 2a to 2n detect the surface potentials of the respective boxes 1a to 1n.

  The first to n-th electrodes 2a to 2n are attached to the switch gear 1 in which a plurality of boxes 1a to 1n accommodating power distribution circuits are accommodated in a row, each box 1a to 1n. The detection signals detected by the first to n-th electrodes 2a to 2n are input to the partial discharge detection device 3 that specifies the generation source of the partial discharge based on a weak signal obtained from the detection signals.

  As shown in FIG. 2, the partial discharge detection device 3 includes terminals 3 a to 3 n, an extraction unit 31, a signal processing unit 40, and the like. The terminals 3a to 3n are connected to the first to nth electrodes 2a to 2n. A plurality of sensor electrodes 2a to 2n are attached to each of the boxes 1a to 1n in the switch gear 1 in which a plurality of boxes 1a to 1n housing power distribution circuits connected to a power supply system are arranged in rows in the terminals 3a to 3n. Detection signals of the respective surface potentials detected by

  The extraction unit 31 is connected to the terminals 3a to 3n. In the extraction unit 31, the signal lines from the terminals 3a to 3n are branched into two, and one of the signal lines is a high pass filter 32 for extracting high frequency signals of the outputs of the first to n-th electrodes 2a to 2n It is connected to the signal processing unit 40 via “HPF 32”. The HPF 32 passes high frequency signals derived from electromagnetic waves having a main component in the several hundred MHz band from the detection signal. Therefore, signal components in the frequency band lower than several hundred MHz are cut. The signals input from the one signal line to the signal processing unit 40 via the HPF 32 are referred to as 2a (H) to 2n (H).

  The other signal line is connected to the signal processing unit 40 as it is. In the other signal line, various noises enter the ground bus 5 from the ground 6 and are input to the signal processing unit 40 as low frequency signals derived from the ground current having a main component in the several MHz to several 10 MHz band. Note that noise that enters the ground bus 5 from the ground 6 is referred to as "ground noise". Signals that are input from the other signal line to the signal processing unit 40 as they are are referred to as 2a (L) to 2n (L). Although a low pass filter for passing a frequency band of 1 MHz to 20 MHz band may be provided on the other signal line, the signal as it is has no influence in this band.

  The extraction unit 31 detects signals of surface potentials detected by a plurality of electrodes such as the first to n-th electrodes 2a to 2n in a first band (100 MHz or more (for example, several hundred MHz band)). The signal S1 and the signal S2 including the second band (band of 1 MHz to 20 MHz) are extracted. That is, the extraction unit 31 may separate at least the signal S1 from the detection signal, and may input the separated signals S1 and S2 to the signal processing unit 40.

  As shown in FIG. 3, the signal processing unit 40 includes a subtraction unit 41, a specifying unit 42, and a display unit 43. The high frequency signals 2a (H) to 2n (H) from the first to nth electrodes 2a to 2n through the HPF 32 are input to the subtraction unit 41.

  The signal processing unit 40 detects the generation timing of the partial discharge based on the signal S1 and the signal S2 for each of the first to n-th electrodes 2a to 2n, and detects the high frequency signal 2a (H) detected by the different electrodes 2a to 2n. The box (one of the boxes 1a to 1n) from which the partial discharge is generated is specified based on .about.2n (H).

  The subtractor 41 subtracts the plurality of signals 2a (H) to 2n (H) in the first band (several hundreds of MHz band) from each other to obtain the potential difference of each signal. In the identification unit 42, detection signals (low frequency signals 2a (L) to 2n (L)) of the first to nth electrodes 2a to 2n and high frequency signals 2a (H) to 2n (H) The potential differences of the respective signals obtained by subtracting one from the other are input.

  The specifying unit 42 generates a plurality of partial discharges based on the signal S1 of the first band (several hundreds MH band) and the signal S2 of the second band (1 MHz to 20 MHz bands) for each of the electrodes 2a to 2n. Among the signals 2a (H) to 2n (H) of the first band (several hundreds of MHz band), the box 1a in which the signal satisfying the condition of the preset potential difference is detected is specified as the partial discharge generation source.

  The signal satisfying the condition of the potential difference is, for example, one having the largest peak value exceeding the threshold value of the preset signal level. Besides, as the condition of the potential difference, for example, a duration in which the potential difference exceeding the threshold value is maintained, an occurrence frequency of exceeding the threshold value, or the like may be used. Thus, at least one of the peak value, the duration, and the frequency of occurrence is used as the condition of the potential difference.

  That is, the specifying unit 42 specifies the generation timing of the partial discharge from the high frequency signal S1 and the low frequency signal S2, and at the specified timing, the plurality of signals 2a (H) obtained by subtraction by the subtracting unit 41 The partial discharge generation source is identified based on the potential difference of 2n (H) (from the magnitude relationship of the potential difference), and the information on the specified partial discharge generation source is displayed on the display unit 43.

  In addition, a signal of a high frequency component (several hundreds MHz band component) included in a detection signal S (see FIG. 6) detected by one box (for example, box 1a) is referred to as S1 so that signals can be easily identified. A signal of low frequency components (1 MHz to 20 MHz band components) is referred to as S2, and a plurality of high frequency signals extracted respectively by a plurality of boxes are referred to as 2a (H) to 2n (H), and a plurality of low frequency signals are 2a (L) to 2n (L).

  Specifically, the specifying unit 42 sets a predetermined or more at the same timing based on the signal S1 of the first band (several 100 MHz band) and the signal S2 of the second band (1 MHz to 20 MHz band) for each of the electrodes 2a to 2n. A timing at which a level signal is generated is detected, and a box of a partial discharge generation source based on a plurality of signals 2a (H) to 2n (H) of the first band (several hundreds MHz band) extracted for each of the electrodes 2a to 2n The body (for example, the box 1a among the boxes 1a to 1n) is identified.

Next, a partial discharge identification (determination) operation will be described with reference to FIGS. 4 to 6.
As shown in FIG. 4, when a partial discharge occurs, a low frequency signal S1 derived from the ground current having a main component in a frequency band of several MHz to several 10 MHz for each of the electrodes 2a to 2n and a frequency band of 100 MHz or more An electromagnetic wave-derived high frequency signal S2 having a main component is simultaneously detected.

  Here, the low frequency signal S2 derived from the ground current is propagated through the ground bus 5 (conductor) and has low detection sensitivity because it competes with background noise in the ground field. On the other hand, the high frequency signal S1 has high detection sensitivity to the background noise of the ground field. Furthermore, since the high frequency signal S1 is a signal obtained by detecting a radiated electromagnetic wave (airwave) of partial discharge, the signal level becomes smaller as the distance from the part (box) where partial discharge is generated.

  For example, when partial discharge occurs in the first box 1a, the signal processing unit 4 displays two signals (shown schematically in the upper and lower sides in the box 1a as shown in FIG. 5) The high frequency signal 2a (H) derived from electromagnetic waves is input to the upper side, and the low frequency signal 2a (L) derived from the ground current to which noise is superimposed is input to the lower side.

  The amplitude of the high frequency signal 2a (H) changes significantly (oscillates) at the timing of discharge generation, and the time when the amplitude becomes large is, for example, about 50 nsec to 100 nsec. In addition, the low frequency signal 2a (L) vibrates randomly at regular intervals of, for example, about 1 μsec to 5 μsec under the influence of noise.

  On the other hand, even if the detection signal detected by another box in which partial discharge is not generated, for example, the second box 1b of FIG. Since the amplitude of H) is located adjacent to the partial discharge generation location (the first box 1a) by one box, the amplitude decreases in accordance with the distance (see the waveform in the box 1b on the right in FIG. 5). Therefore, by comparing the magnitudes of the signal levels, it is possible to specify the occurrence location of a large amplitude where the signal level is equal to or greater than a predetermined value. Even with a large amplitude, this alone can not identify that it is a partial discharge. Further, the low frequency signal 2b (L) of the partial discharge signal and the ground noise are detected to have the same size.

Therefore, the signal processing unit 40 identifies the partial discharge signal and the generation timing thereof by the following operation.
The subtraction unit 41 of the signal processing unit 40 mutually subtracts the high frequency signals 2a (H) to 2n (H) input from the respective electrodes (first to nth electrodes 2a to 2n), and the subtraction result ( The potential difference is output to the identification unit 42.

  The identifying unit 42 first receives the signal of the subtraction result input from the subtracting unit 41, that is, the high frequency signals 2a (H) to 2n (H) and the low frequency signals 2a (L) to 2n (L) for each of the electrodes 2a to 2n. The timing of occurrence of partial discharge is detected based on

  Specifically, when a partial discharge occurs in the first box 1a, as shown in FIG. 6, the identifying unit 42 outputs a signal of 100 MHz band separated from the detection signal S detected by the first electrode 2a. S1 and the signal S2 in the 1 MHz to 20 MHz band are matched, and at the same timing, the portion where the potential difference more than the threshold of each signal is generated (a part of the amplitude waveform) is the generation point of partial discharge, that is, partial discharge occurrence Identify (determine) the timing.

  Subsequently, the specifying unit 42 subtracts the result (potential difference) of the plurality of signals 2a (H) to 2n (H) input from the subtracting unit 41 in the manner shown in FIG. By comparing any of the signals 2a (H) to 2n (H) with the largest potential difference as the signal Sx of the partial discharge, and an electrode (for example, the electrode 2a) that detects the signal is attached. The first box 1a which is located is specified as a partial discharge source.

  Since the circuits accommodated in the first to n-th box bodies 1a to 1n are connected to the ground bus bar 5, noise from the ground bus bar 5 is detected in all components in the same degree, The partial discharge is largely detected only by the box.

  These processings are performed among the first to n-th electrodes 2a to 2n, and when the potential difference exceeding the preset threshold is detected, the identifying unit 42 detects a box (a part of a detection source of the signal) The discharge place is identified and displayed on the display unit 43. In order to specify the box, identification information of the first to n-th electrodes 2a to 2n and identification information of the boxes 1a to 1n are associated with each other and stored in advance in a memory or the like.

  As for the display method, for example, among the drawings of the row board displayed on the screen, it is possible to color only the target box, change the color, or display the ID of the target box in the dialog box instead of the drawing. And so on.

  In addition, thresholds such as the peak value, duration, and occurrence frequency of the potential difference are set in advance in a memory or the like, and the identifying unit 42 exceeds the threshold of the memory for any item by comparing the detected value with the threshold. It may be determined that partial discharge has occurred.

  Moreover, you may use what calculated discharge energy by multiplying these peak value, duration, and occurrence frequency as a threshold value. Furthermore, since partial discharges have many intermittent discharges, the number of partial discharges exceeding the threshold is counted in the memory, and the number of times detected as partial discharges is counted more than a certain number of times (detection of threshold or more multiple times Subsequently, if it is determined that the partial discharge has occurred, it is possible to prevent noise that is accidentally overlapped as a partial discharge from being erroneously detected.

  As described above, according to the partial discharge detection system of the first embodiment, in the switch gear 1 in which the first to n-th box bodies 1a to 1n are arranged in a row, generation of partial discharge is performed with high accuracy in box units. It can be detected.

  In switch gear 1, other power systems and power devices that easily generate noise are connected, and complex and large noises with different frequency components and powers are superimposed on the main circuit, but the high frequency components of the partial discharge signal have different signal strengths, And the low frequency noise superimposed on the first to nth box bodies 1a to 1n can be ignored.

  In addition, when the generation box body of partial discharge is specified, it separates from other box bodies, finds out the generation part using a general partial discharge measuring instrument, and performs maintenance according to the situation of the generation part I assume. Specifically, parts replacement, replacement of the entire box, etc. are performed.

  That is, according to the first embodiment, the first to nth electrodes 2a to 2n are contact-fixed to the constituent plates of the plurality of first to nth box bodies 1a to 1n arranged in a row, respectively. Since a plurality of detection signals having high frequency components are subtracted by the subtraction unit 41 of the signal processing unit 40 and the low frequency noise superimposed on the main circuit is cancelled, even complex noises with different frequency components and power are reliably removed, A partial discharge occurring in any of the plurality of first to n-th boxes 1a to 1n arranged in a row (row) is detected with high sensitivity after specifying the box in which the partial discharge has occurred it can.

  In the first embodiment, the switch gear 1 has been described as including the plurality of first to n-th box bodies 1a to 1n, but other than this, for example, the electric device such as a vacuum valve or a main circuit conductor is insulated The first to n-th electrodes 2a to 2n are attached to the ground layer of each mold member of a switch gear which is molded with a material and a plurality of these mold members are connected, and high frequency signals of respective detection signals are extracted. The partial discharge can be measured with high detection sensitivity by mutually subtracting the unit of the mold member by the subtraction unit 41.

Second Embodiment
Next, another configuration example (second embodiment) of the signal processing unit 40 of the partial discharge detection device will be described with reference to FIG. 7. FIG. 7 is a diagram showing a circuit configuration of the signal processing unit of the second embodiment. In the second embodiment, the same components as those of the signal processing unit (FIG. 3) of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

  As shown in FIG. 7, the signal processing unit 40 of the second embodiment has an averaging unit 44 at the front stage of the subtracting unit. The averaging unit 44 adds each of the high-frequency signals 2a (H) to 2n (H) input from the extraction unit 31 to the voltage levels of the previous signals and averages them, and inputs the averaged result to the subtraction unit 41 Do. That is, the averaging unit 44 averages the levels of the signals 2a (H) to 2n (H) of the first band (several hundreds of MHz band) extracted from the detection signals detected by the plurality of electrodes 2a to 2n. And outputs the result to the subtraction unit 41.

  In the second embodiment, since the averaging unit 44 averages each high frequency signal and uses the result of the averaging process to identify the presence or the location of the partial discharge, the detection by the sudden signal is suppressed. And the accuracy (detection sensitivity) of partial discharge detection can be improved.

  As described above, according to the second embodiment, in addition to the effects of the first embodiment being obtained, the detection with the signal generated suddenly due to the provision of the averaging unit 44 is excluded, and partial discharge detection can be performed. Accuracy (detection sensitivity) can be improved.

Third Embodiment
Next, another configuration example (third embodiment) of the signal processing unit 40 of the partial discharge detection device will be described with reference to FIG. FIG. 8 is a diagram showing a circuit configuration of a signal processing unit of the third embodiment. In the third embodiment, the same components as those of the signal processing unit (FIG. 7) of the second embodiment are designated by the same reference numerals, and the description thereof will be omitted.

  As shown in FIG. 8, the signal processing unit 40 of the third embodiment has a wavelet transform unit 45 at the front stage of the identification unit 42.

  The wavelet transform unit 45 performs wavelet transform on the detection signal S including the signal S1 of the first band (several 100 MHz band) and the signal S2 of the second band (1 MHz to 20 MHz band) for each of the electrodes 2a to 2n Output to the part 42.

  In the third embodiment, the wavelet transformation unit 45 is provided in the front stage of the identification unit 42, and a portion from the insulator is detected when a high result of 1 MHz to 20 MHz is detected at the timing when the high frequency signal S1 is generated. Determined as discharge.

  As described above, according to the partial discharge detection device of the third embodiment, in addition to the effects of the second embodiment being obtained, the wavelet transform unit 45 carries out the wavelet transform of the mixed signal, thereby including a lot of noise. The partial discharge can be raised from among the signals, and the partial discharge can be detected more reliably.

  According to the embodiment described above, the electrodes 2a to 2n for detecting the surface potential are attached to the constituent plates of the plurality of boxed bodies 1a to 1n arranged in a row, and the detection signals of these electrodes 2a to 2n are high frequency signals The signals are divided into other signals and input to the signal processing unit 40. The signal processing unit 40 detects the generation timing of the partial discharge based on the high frequency signal S1 and the low frequency signal S2 for each of the electrodes 2a to 2n, and detects the partial discharge at the detected timing. Since the partial discharge source box (for example, the box 1a) is specified from the magnitude relationship of the signal levels of the plurality of high frequency signals 2a (H) to 2n (H) extracted for each of the electrodes 2a to 2n, various types of In the case where a plurality of boxes 1a to 1n connected to a power supply system or a power device and large noises are superimposed are arranged in a row, the generation source of the partial discharge can be stopped per box.

  Further, since the high frequency signals of the respective boxes 1a to 1n are mutually subtracted to obtain the potential difference, it is possible to reliably remove large noises and compare the difference signals in units of boxes, and partial discharge of weak signals. It can be detected with high sensitivity.

  Although the embodiment of the present invention has been described, this embodiment is shown as an example, and can be implemented in other various forms, and within the scope of the present invention, You can omit, replace, or change.

  Further, each component of the partial discharge detection device 3 shown in the above embodiment may be realized by a program installed in a storage such as a hard disk drive of a computer, or the above program may be a computer readable electronic medium: The functions of the present invention may be realized by a computer by storing the program in electronic media and reading the program from an electronic medium by the computer. Examples of the electronic medium include a recording medium such as a CD-ROM, a flash memory, and a removable medium: removable media. Furthermore, the components may be distributed and stored in different computers connected via a network, and may be realized by communicating between the computers functioning the respective components.

  Reference Signs List 1 switch gear 1a-1n box body 2a-2n sensor electrode 3a-3n terminal 3 partial discharge detection device 5 ground bus bar 6 ground electrode 31 Extraction unit 32 High pass filter (HPF) 40 Signal processing unit 41 Subtraction unit 42 Specification unit 43 Display unit 44 Averaging unit 45 Wavelet transformation unit

Claims (7)

A signal of a first band is detected from a detection signal of each surface potential detected by a plurality of electrodes attached to each box body in a power device in which a plurality of boxes are provided with a plurality of boxes arranged in a box housing power distribution circuits connected to a power supply system An extraction unit which extracts a signal of a second band;
The partial discharge occurrence timing is detected based on the signal of the first band and the signal of the second band for each of the electrodes, and the partial based on a plurality of signals of the first band detected by different electrodes A partial discharge detection device comprising: a signal processing unit that specifies a discharge source box. The signal processing unit
A subtraction unit that subtracts a plurality of signals in the first band from one another to obtain a potential difference of the respective signals;
The partial discharge detection device according to claim 1, further comprising: a specification unit that specifies a partial discharge generation source based on a potential difference of each signal obtained by the subtraction by the subtraction unit. The identification unit is
At the generation timing of the partial discharge detected based on the signal of the first band and the signal of the second band for each of the electrodes, the condition of the potential difference preset among the plurality of signals of the first band is The partial discharge detection device according to claim 2, wherein the box in which the signal that has been filled is detected is identified as a partial discharge source.   The partial discharge detection device according to claim 3, wherein the condition of the potential difference is at least one of a peak value, a duration, and an occurrence frequency. The signal processing unit
The partial discharge according to any one of claims 1 to 4, further comprising an averaging unit that averages the level of each signal in the first band extracted from each detection signal detected by the plurality of electrodes. Detection device.   The wavelet transform unit according to any one of claims 1 to 5, further comprising: a wavelet transform unit configured to perform wavelet transform on a detection signal including the signal of the first band and the signal of the second band for each of the electrodes. The partial discharge detection device according to claim 1. A partial discharge detection method by a partial discharge detection device in which a plurality of electrodes attached to each box body are connected to an electric power device in which a plurality of boxes arranged in a plurality of boxes housing power distribution circuits connected to a power supply system,
A signal of a first band and a signal of a second band are extracted from detection signals of respective surface potentials detected by the plurality of electrodes,
The occurrence timing of the partial discharge is detected based on the signal of the first band and the signal of the second band for each of the electrodes,
A partial discharge detection method for specifying a partial discharge source box based on a plurality of signals in the first band detected by different electrodes.

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