JP2009300289A - Partial discharge detection method by electromagnetic wave measurement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve discrimination accuracy between an environmental electromagnetic wave such as a broadcast wave and a partial discharge electromagnetic wave generated in an apparatus or the like. <P>SOLUTION: An antenna 12 detects the partial discharge electromagnetic wave in an apparatus body 11, and the detection signal is amplified by an amplifier 13, and converted into a digital signal by an analog signal-digital signal converter 16 via a band-pass filter 14. The conversion signal is input to a frequency spectrum analysis part 17 using FFT, and the frequency spectrum analysis part 17 measures the signal by changing the measurement time. Firstly, it is the short-time measurement data measured in a short time. Secondly, it is the long-time measurement data measured in a comparatively long time. The short-time measurement data and the long-time measurement data output from the frequency spectrum analysis part 17 are temporarily stored in first and second storage parts 18a, 18b. Thereafter, the frequency spectra of both the data are compared by a comparison part 19. The comparison result of the frequency spectra by the comparison part 19 is input to and determined by a determination part 20. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a partial discharge detection method in an electric facility or equipment operation state, and more particularly to a partial discharge detection method by electromagnetic wave measurement.

  Examples of abnormal phenomena that commonly occur in high-voltage electric facilities and equipment include the occurrence of partial discharge (hereinafter referred to as PD) due to the effects of defects during manufacturing and aging. In general, if there are minute voids (voids) or delaminations in the insulation (material) used in molding equipment, etc., the electric field concentrates on those parts during operation, and a weak discharge called PD Will occur. PD may also occur due to the influence of contamination on the surface of the mold insulator.

  In particular, in the latter case, PD can be prevented by removing contamination, but the PD in the former case cannot be prevented and is not recoverable. If the operation is continued in a state where PD is generated, there is a risk that a void or a peeled state may be developed, and there is a risk of eventually leading to dielectric breakdown.

  Examples of PD generated in an electric device (specimen) include air discharge (corona) due to surface contamination of a high-voltage mold site, and discharge generated in a defective portion such as a crack, void, or peeling inside the mold device. There are the following four methods as a PD 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 PD generation is measured.
(B) An electrical method (high frequency CT method) for attaching a high frequency CT to the grounding wire (grounding wire current method) and measuring a pulse current generated with the occurrence of PD,
(C) a diagnostic measurement method for acoustically detecting elastic wave vibration and discharge sound accompanying PD generation;
(D) The electromagnetic wave emitted with PD generation is measured (electromagnetic wave detection method).

  The CC method of (a) above captures the charge amount Q due to the PD in the specimen TF as the voltage Vd generated in the detection impedance Z in the PD calibration / measurement circuit diagram shown in FIG. When a PD having a charge amount Q is generated, the voltage Vd generated at both ends of the detection impedance Z is calculated from the capacitance Ca of the specimen TF, the capacitance of the coupling capacitor Ck, the detection impedance Z and its frequency characteristics, etc. Then you can not ask.

  For this reason, in FIG. 9, the sensitivity adjustment (calibration) of the measuring instrument MI is performed by injecting a known charge amount Qcal into the specimen TF. 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 grounding wire, and it is difficult to perform calibration as a measure of the measured discharge charge amount, and the PD 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 a sensor using a piezoelectric element, and is applied as a method of estimating a PD generation value by detecting an elastic wave propagating in a solid such as a metal surface and performing signal processing.

  In addition, there is also an acoustic method that directly captures ultrasonic waves generated by PD generation with a parabola using a piezoelectric element as a sensor. However, in order to target ultrasonic waves emitted into the air, corona discharge is targeted for detection. Yes. 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 such as broadcast waves becomes a problem (for example, Patent Document 2). To 5).
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 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.

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

  In the diagnostic measurement method (AE method) for acoustically detecting elastic wave vibration and discharge sound due to PD generation in (c) above, the elastic wave due to the discharge phenomenon during operation is detected directly or indirectly. In the housed mold apparatus, as an indirect detection method, there is means for performing measurement by attaching the AE sensor 2 to the side wall 1a of the switchboard 1 shown in FIG. Reference numeral 3 denotes a molding device.

  If the AE sensor 2 attached to the side wall surface 1a as shown in FIG. 10 is used, it is possible to detect the elastic wave accompanying the discharge phenomenon inside the switchboard 1, 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, the transformer has an iron core, noise is generated from the iron core, and the detection accuracy of PD is lowered. 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 separate things.

  In addition, in the method of capturing the discharge phenomenon by sound, when applied to a transformer housed in a switchboard, the measurement may be difficult due to a barrier placed in the panel, and when it is completely sealed It is necessary to open a barrier. 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 PD 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 the 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, as shown in FIG. 11, the electromagnetic waves emitted by the PD generated in the electrical equipment and equipment, and the corona discharge generated in the atmosphere, the surface of the insulator, and the PD generated inside the insulator of the molding equipment are as shown in FIG. 11. In general, it appears in a band of several tens to several hundreds of MHz.

  FIG. 11 shows an example of a measurement result of electromagnetic waves emitted with corona discharge. For example, in FIG. 11, 30 to 50, 110 to 160, and 250 to 400 MHz are partial discharge electromagnetic waves, and 70 to 110, 170 to 230, 470 to 500 MHz, and the like are environmental electromagnetic waves such as broadcast waves.

  Note that the measurement results in FIG. 11 also have a problem that it is difficult to distinguish between environmental electromagnetic waves and partial discharge electromagnetic waves depending on the field because environmental electromagnetic waves such as broadcast waves are also emitted in the same band.

  An object of the present invention has been made in view of the above circumstances, and in particular, a partial discharge detection method by electromagnetic wave measurement that improves the discrimination accuracy between environmental electromagnetic waves such as broadcast waves and partial discharge electromagnetic waves generated in equipment and the like. It is an issue to provide.

In order to achieve the above-mentioned object, the invention according to claim 1 is configured to amplify and filter a signal of a partial discharge electromagnetic wave generated from an electric device main body after detecting it with an antenna disposed in the vicinity of the device main body. In the method of detecting,
The filtered signal is converted into an analog signal / digital signal, and the converted digital signal is analyzed by the frequency spectrum analyzer to measure the electromagnetic wave signal. After obtaining data by performing measurements twice, compare the measurement data results for both times, and if there is a difference in the intensity of each data spectrum frequency, the partial discharge electromagnetic wave is If it is determined that it is generated and there is no difference, it is determined that the generation of the partial discharge electromagnetic wave is not generated from the device body only by the environmental electromagnetic wave.

  The invention according to claim 2 is characterized in that, in claim 1, the set time for the short time measurement is set to 1 second or less, and the set time for the long time measurement is set to be longer.

  The invention according to claim 3 is the spectrum pattern according to claim 1 or 2, wherein the short-time measurement is performed a plurality of times to obtain a plurality of measurement data, and then an average for each frequency component of the measurement data is calculated; Compared with the spectrum pattern of the measurement data obtained by performing multiple measurements for a long time, depending on whether there is a difference between both spectrum patterns and whether the intensity of those frequency bands exceeds the set judgment threshold It is characterized by determining whether or not a discharge electromagnetic wave is generated.

  According to a fourth aspect of the present invention, in the first or second aspect, a plurality of antennas are installed at positions spaced apart from the electric device main body to obtain a plurality of short-time measurement data for each antenna, and the plurality of measurement data The spectrum pattern obtained by calculating the average for each frequency component and a plurality of the long-time measurement data obtained by the antenna installed in the vicinity of the main body of the electric device are compared, and the spectrum pattern of the measurement data is compared. And whether or not the partial discharge electromagnetic wave is generated is determined depending on whether or not the intensity of the frequency band exceeds a set determination threshold.

  The invention according to claim 5 is the electromagnetic wave signal according to any one of claims 1 to 4, wherein the power supply voltage waveform of the electric device body is taken into a frequency spectrum analysis unit and is synchronized with a specific phase of the UVW phase of the voltage waveform. And performing partial discharge electromagnetic wave measurement for each phase, determining the result, and determining from which phase the partial discharge electromagnetic wave is generated.

  According to the present invention, after measuring the frequency spectrum for a short time and a long time and changing the measurement time, and comparing the obtained measurement data, if there is a difference in the intensity for each frequency of both spectra, If it is determined that the discharge electromagnetic wave is generated and there is no difference, it is determined that the partial discharge electromagnetic wave is not generated only by the environmental electromagnetic wave, thereby improving the discrimination accuracy between the partial discharge electromagnetic wave and the environmental electromagnetic wave. Will be able to.

  In addition, according to the present invention, a plurality of antennas are installed around a specimen for detecting whether partial discharge has occurred, and the results obtained by measuring the signals detected by each antenna a plurality of times are averaged. By comparing with the results measured in the vicinity, the discrimination accuracy between the partial discharge electromagnetic wave and the environmental electromagnetic wave can be dramatically improved.

  Furthermore, according to the present invention, by determining the partial discharge electromagnetic wave measurement result for each phase of the power supply voltage waveform, it is possible to determine not only the occurrence of partial discharge but also from which phase the partial discharge has occurred. can do.

Embodiments of the present invention will be described below with reference to the drawings.
[Embodiment 1]
FIG. 1 is a block diagram showing the first embodiment of the present invention, and FIG. 1 particularly enables detection of partial discharge of a molded-type instrument transformer in a live state. In FIG. 1, reference numeral 11 denotes an electric equipment body including a molded instrument transformer, and reference numeral 12 denotes an antenna disposed in the vicinity of the electric equipment body 11. The antenna 12 detects a partial discharge electromagnetic wave or the like in the electric device main body 11, and the detected signal is amplified by a low noise amplifier 13.

  The signal amplified by the amplifier 13 is amplified again by the amplifier 15 through a band filter 14 that passes a frequency of 1 MHz to 500 MHz, for example, and the analog signal is converted into a digital signal by the analog signal / digital signal converter 16. .

  The converted digital signal is input to the frequency spectrum analysis unit 17 using FFT. In the frequency spectrum analyzer 17, the input digital signal is measured twice with different measurement times. The first measurement time is, for example, short-time measurement data obtained by measuring in a short time of 1 second, and the second measurement time is long-time measurement data obtained by measuring in a relatively long time of 20 seconds. is there.

  FIGS. 2A and 2B are frequency spectrum distribution characteristics diagrams of the short-time and long-time measurement data obtained as described above.

  The short-time and long-time measurement data analyzed by the frequency spectrum analysis unit 17 as described above are temporarily stored in the first and second storage units 18a and 18b, and then the frequency of both data is compared by the comparison unit 19. The spectra are compared. The comparison result by the comparison unit 19 is input to the determination unit 20, and environmental electromagnetic waves and partial discharge electromagnetic waves are determined.

  Normally, environmental electromagnetic waves such as broadcast waves are much stronger than partial discharge electromagnetic waves, so there is no significant difference in the measured frequency spectrum between short-time measurement and long-time measurement. Is unstable, and there is a difference in spectrum between short-time and long-time measurements. Therefore, the determination unit 20 determines as follows because there is this difference.

  If there is a difference in the intensity for each frequency of the spectrum from the determination result in the determination unit 20, it is determined that a partial discharge has occurred inside the electric equipment body 11, and if there is no difference, the broadcast It can be determined that there is no partial discharge with only environmental electromagnetic waves such as waves.

In the first embodiment, a spectrum analyzer may be used instead of the analog signal / digital signal converter 16 and the frequency spectrum analysis unit 17, or a digital signal processor may be used. Further, the first and second storage units 18a and 18b and the comparison unit 19 may be configured by a pattern analysis unit.
[Embodiment 2]
In the first embodiment, the frequency spectrum analysis in the frequency spectrum analysis unit 17 is a comparison of data only twice by short time measurement and long time measurement. However, the second embodiment of the present invention is shown in FIG. Using the block configuration diagram, as shown in the flowchart of FIG. 3, first, electromagnetic wave measurement data (frequency spectrum) is obtained in step S1.

  Next, data obtained by measuring a plurality of times in a short time in step S2 is obtained from the data obtained in step S1. The obtained data is calculated in step S3 as data (spectrum) obtained by averaging values (intensities) for each frequency component.

  In step S5, the data (spectrum) calculated in step S3 is compared with the data (spectrum) obtained by performing the long-time measurement with a longer measurement time a plurality of times in step S4 without averaging. From the comparison result of this data, when there is a difference between the two data (spectrum) patterns and when the intensity of those frequency bands exceeds the set judgment threshold, there is a possibility that partial discharge electromagnetic waves are generated. As a result, it is determined in step S5 and sent to step S6.

In this way, the comparison was made by comparing all the data measured several times in the vicinity of the main body of the electrical equipment with the individually averaged data (spectrum). For sudden data, noise (caused by factors other than partial discharge) By judging as environmental electromagnetic waves, etc., it was excluded from the evaluation target, and the determination accuracy was improved.
[Embodiment 3]
FIG. 4 is a flowchart showing the third embodiment of the present invention. In FIG. 4, in the same manner as in the second embodiment in step S11, in order to obtain electromagnetic wave measurement data in step S11, a plurality of positions away from the electrical equipment 11 are provided. Each antenna is arranged, and these antennas are switched by an antenna switch or the like to measure data (S12). The data measured in step S12 is measured for a short time as in the first and second embodiments, and a plurality of measurement data (spectrums) is obtained in step S13.

  The obtained plurality of measurement data is calculated in step S14 by averaging values (spectral intensities) for each frequency component in the same manner as in step S3 of the second embodiment.

  Next, step S15 is a step of measuring with an antenna disposed in the vicinity of the electric device main body 11, and the data measured in step S15 is obtained as long-time measurement data in step S16 by performing long-time measurement a plurality of times.

  In step S17, the data (spectrum) calculated in step S14 is compared with the data (spectrum) obtained in step S16, and both data (spectrum) are compared as in step S5 of the second embodiment. If there is a difference between the two data (spectrum) patterns from the comparison result, and if the intensity of those frequency bands exceeds the set judgment threshold, it is assumed that a partial discharge electromagnetic wave may be generated. The determination is made at S17 and the process is sent to step S18.

As in the third embodiment, the number of times of measurement of the environmental electromagnetic wave is performed, or antennas are installed at a plurality of locations, and the data measured at each location is averaged. Even if a partial discharge electromagnetic wave is mixed, the value can be smoothed, and the discrimination accuracy in comparison with the result of the electromagnetic wave measurement measured in the vicinity of the specimen targeted for diagnosis can be improved.
[Embodiment 4]
FIG. 5 is a block diagram showing a fifth embodiment of the present invention. In the fifth embodiment, the secondary of the electric device main body 11 is detected in order to detect a partial discharge generated for each phase of the electric device main body 11. The power supply voltage waveform capturing unit 51 is connected to the terminal. In order to determine the phase UVW of the voltage waveform from the power supply voltage waveform acquired from the acquisition unit 51, the voltage waveform phase determination unit 52 is input. The output of the phase UVW determined by the voltage waveform phase determination unit 52 is input to the frequency spectrum analysis unit 17 shown in FIG.

  The frequency spectrum analysis unit 17 analyzes the partial discharge generated in each phase of the phase UVW input from the phase determination unit 52. In general, the partial discharge generated in each phase often occurs at the voltage rising of each phase (generated phase band: 0 to 90 degrees and 180 to 270 degrees) as shown in FIG.

  The occurrence of partial discharge shown in FIG. 6 is related to the state of the power supply voltage. Generally, due to the increase in voltage, the withstand voltage of a defect (such as a void) in the molded product exceeds the limit, and the partial discharge occurs. Will cause a serious discharge. That is, the partial discharge generation phase appears in a fixed phase band (not completely coincident) with a change in the power supply voltage cycle.

  Basically, partial discharge often occurs as two large groups during one cycle of the power supply voltage. FIG. 6 shows a partial discharge occurrence state in a single-phase power cycle as an example. By grasping the characteristics of the generated phase, it is detected in which phase of the normal three-phase power supply line the partial discharge is generated. Specifying the partial discharge occurrence location is also a major issue, and the generation phase specification is important.

  Therefore, paying attention to the partial discharge generation phase band generated individually for each phase UVW, only the phase band is measured by the frequency spectrum analysis unit 17, and the partial discharge electromagnetic wave is analyzed using the flowchart shown in FIG.

  FIG. 7 is a flowchart for detecting the partial discharge electromagnetic wave by determining the phase. In step S21, a power supply voltage waveform is taken from the main body of the electric device, and phase determination of the phase UVW of the voltage waveform is performed in step S22.

  Thereafter, when each phase of the phase UVW is determined in step S23, signal capture is controlled as the set phase of the power supply voltage in step S24. In step S25, it is determined whether the captured phase is 0 to 90 degrees or 180 to 270 degrees of the partial discharge generation phase band. If “No”, the process proceeds to step S26, and the partial discharge electromagnetic wave measurement is not performed. Or invalidate the measurement data.

  If the result of determination in step S25 is “Yes”, processing in step S27 is performed. Step S27 is a flowchart shown in FIG. 3, and the process shown in FIG. 3 is performed to output the phase at which the partial discharge electromagnetic wave is generated (S28). After comparing in step S29, the partial discharge electromagnetic wave is output in step S30. Evaluation of discharge occurrence and identification of partial discharge occurrence phase. Step S31 also includes the flowchart shown in FIG.

  FIGS. 8A and 8B are explanatory diagrams for describing phase determination. FIG. 8A illustrates a case where it is determined that the measured PD signal is generated from the U phase. FIG. This is a case where it is determined that a PD signal is generated in a phase other than the phase, and this determination method is also performed for the V phase and the W phase to determine which phase is generated from the U, V, and W phases. .

1 is a block configuration diagram showing Embodiment 1 of the present invention. Frequency spectrum distribution characteristic diagram of data by short time and long time measurement. The flowchart which shows Embodiment 2 of this invention. The flowchart which shows Embodiment 3 of this invention. The block block diagram which shows Embodiment 4 of this invention. Explanatory drawing which shows a partial discharge generation | occurrence | production phase band. 10 is a flowchart for illustrating Embodiment 4; Explanatory drawing which describes a phase determination. 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

11 ... Molded instrument transformer (electrical equipment body)
DESCRIPTION OF SYMBOLS 12 ... Antenna 13 ... Low noise amplifier 14 ... Band filter 15 ... Amplifier 16 ... Analog signal digital signal converter 17 ... Frequency spectrum analysis part 18a, 18b ... 1st, 2nd memory | storage part 19 ... Comparison part 20 ... Determination Part

Claims (5)

In the method of detecting the signal of the partial discharge electromagnetic wave generated from the electric device main body with an antenna disposed in the vicinity of the device main body, then amplifying and filtering,
The filtered signal is converted into an analog signal / digital signal, and the converted digital signal is analyzed by the frequency spectrum analyzer to measure the electromagnetic wave signal. After obtaining the data by performing two measurements of the above, compare the measurement data results of both times, and if there is a difference in the intensity for each frequency of the spectrum of both data, the partial discharge electromagnetic wave If there is no difference, it is determined that the generation of the partial discharge electromagnetic wave only from the environmental electromagnetic wave is not generated from the device body. . In the partial discharge detection method by electromagnetic wave measurement of Claim 1,
The partial discharge detection method by electromagnetic wave measurement according to claim 1, wherein the set time for the short-time measurement is 1 second or less, and the set time for the long-time measurement is longer. In the partial discharge detection method by electromagnetic wave measurement of Claim 1 or 2,
After obtaining a plurality of measurement data by performing the short-time measurement a plurality of times, a spectrum pattern obtained by calculating an average for each frequency component of the measurement data and a spectrum pattern of the measurement data obtained by performing the long-time measurement a plurality of times The electromagnetic wave measurement is characterized by determining the presence or absence of partial discharge electromagnetic waves depending on whether there is a difference between the two spectral patterns and whether the intensity of those frequency bands exceeds the set threshold. Partial discharge detection method by. In the partial discharge detection method by electromagnetic wave measurement of Claim 1 or 2,
A plurality of antennas are installed at positions spaced apart from the electric device main body, a plurality of short-time measurement data for each antenna is obtained, and the spectrum pattern obtained by calculating the average for each frequency component of the plurality of measurement data, and the electric Obtain a plurality of the long-time measurement data from the antenna installed in the vicinity of the device body, compare the spectrum pattern of the measurement data, and if there is a difference between the two spectrum patterns, the intensity of those frequency bands is set A partial discharge detection method by electromagnetic wave measurement, characterized by determining whether or not partial discharge electromagnetic waves are generated depending on whether or not a threshold value is exceeded. In the partial discharge detection method by electromagnetic wave measurement of any one of Claim 1 to 4,
The power supply voltage waveform of the electrical device body is taken into the frequency spectrum analysis unit, the electromagnetic wave signal is analyzed in synchronization with the specific phase of the UVW phase of the voltage waveform, the partial discharge electromagnetic wave measurement is performed for each phase, and the result is determined. A method for detecting partial discharge by electromagnetic wave measurement, comprising determining from which phase a partial discharge electromagnetic wave is generated.

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