JP2723902B2 - Spectrum subtraction type partial discharge monitoring system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a partial discharge monitoring system used for gas insulated equipment, and more particularly to a spectrum subtraction suitable for improving the accuracy of partial discharge determination and improving the reliability of abnormality diagnosis. System for partial discharge monitoring.

[Conventional technology]

As a conventional device, as described in JP-A-61-69312 and JP-A-61-147170, various detection frequency bands of a partial discharge detection device are selected to reduce the influence of external noise. Considerations have been made to avoid it.

On the other hand, it is very difficult to specify the external noise because the frequency band and the generated phase are not stable.

In the case of partial discharges, there are those that come from inside the gas-insulated equipment to be monitored, and those that occur in the atmosphere, such as the transmission lines or substation line entrances.It is also important to distinguish between these. It has become a challenge.

Recently, as described in JP-A-59-2518, a method has been proposed in which the frequency characteristic of a detection signal is examined using a spectrum analyzer to monitor partial discharge.
However, hitherto, sufficient consideration has not been given to discrimination of partial discharges generated from the outside and the inside of the device as described above, improvement of detection sensitivity, and further, points of location.

[Problems to be solved by the invention]

In the above prior art, sufficient consideration has not been given to the improvement of detection sensitivity and the method of discriminating external noise and internal partial discharge.
There was a problem in detecting a signal of a minute partial discharge from inside the device. In other words, the level of partial discharge generated inside gas-insulated equipment varies depending on the cause and location of the partial discharge. You.

In addition, the minute partial discharge described above must be detected separately from external noise from outside the device.

Furthermore, it is also important to improve the technology for determining whether the partial discharge is generated from the target device or from the surroundings.

An object of the present invention is to provide a partial discharge monitoring system having the above functions.

[Means for solving the problem]

The above object is to provide a gas-insulated device with a built-in detector to detect a partial discharge generated inside the device with high sensitivity, and to examine by subtracting a frequency spectrum of a partial discharge signal obtained from the detector. Is achieved.

That is, it was confirmed by experiments conducted under various conditions that the partial discharges generated in various conditions inside the gas insulated equipment exhibited a characteristic frequency spectrum having a high-frequency component exceeding several hundred MHz. Furthermore,
It has also been clarified that the partial discharge generated outside the gas-insulated device has a frequency spectrum in which a low-frequency component lower than the high-frequency band component of the partial discharge inside the device is emphasized.

The present invention focuses on the difference between the frequency spectrums of the external and internal partial discharges as described above, and discriminates the internal and external partial discharges from the pattern of the frequency spectrum of the detection signal obtained from the detector. It is.

The external partial discharge may show a frequency spectrum including a high-frequency component of several hundred MHz depending on the generation position and the generation level, and the internal and external discharges are simply obtained from the frequency spectrum of the detection signal obtained from the detector. It is difficult to determine the partial discharge.

As a solution for reliably determining such an external partial discharge and an internal partial discharge, the frequency spectrum of a detection signal obtained from a detector provided in each of the internal and external devices and each phase is subtracted from each other, In this method, only the high frequency component of the internal partial discharge is taken into the residual spectrum after the subtraction.

[Action]

Partial discharge generated inside gas insulated equipment is several hundred MHz
Because of the high-frequency characteristics of this product, it has characteristics that it easily propagates through the stray capacitance and is transmitted to the high-voltage conductor, the grounding tank, and the grounding line via the gas space in the equipment and the capacitance of the insulator. In addition, it has the characteristic of being radiated into the space outside the device as spatial electromagnetic waves. Therefore, the partial discharge of the gas-insulated equipment can be detected by various detectors provided inside and outside the equipment. In addition, in addition to the partial discharge generated inside the device, the partial discharges generated outside the device and various external noises enter all of these detectors.

Although the detection sensitivity of the above-mentioned signals differs depending on the detector, the built-in detector incorporated in the device has the advantage that high-frequency components peculiar to the partial discharge generated inside the device can be detected with high sensitivity. ing.

The frequency spectrum of the detection signal obtained from the built-in detector is obtained in three types of patterns shown in FIG. In other words, the partial discharge that occurs in the device is
In contrast to the almost peak-shaped spectrum pattern with the maximum value in the high-frequency band of 1500 MHz, the partial discharge generated outside the device is of the (II) or (III) type where the low-frequency component of 400 MHz or less is emphasized. Indicated by a pattern.

When the frequency spectrum of the detection signal is represented by a single pattern of [I] type or [II] type, it is possible to easily determine whether the detected partial discharge is generated inside or outside.

On the other hand, the spectrum when the partial discharge is superimposed on the internal partial discharge and the external partial discharge is shown by a pattern in which the low frequency component of [II] or [III] type and the high frequency component of [I] type coexist. Here, the level of partial discharge is small inside,
If the high-frequency component of type [I] results in a pattern that appears at a low level, it becomes difficult to distinguish it from the pattern of type [III], which includes only high-frequency components and separate external discharges. This is a factor in reducing the accuracy of discriminating discharges.

As means for reliably determining the internal partial discharge from such a spectrum pattern, a frequency spectrum of a detection signal obtained from an external detector provided outside the device and a detection signal obtained from the above-described built-in detector are used. Are subtracted from each other, and the high frequency component of the internal partial discharge is left in the remaining spectrum after the subtraction.

In the phase-separated three-phase device, a built-in detector having the same configuration and the same characteristics is provided for each phase, and the frequency spectrum of a detection signal obtained from the detector for each phase is subtracted. Here, an external detector arranged outside the device, for example, an antenna for detecting a spatial electromagnetic wave, has a detection level equal to or higher than that of the built-in detector for a partial discharge generated from the outside of the device. However, since the high-frequency component of the internal partial discharge is attenuated when radiated to the outside of the tank, the detection level is always lower than that of the built-in detector.

Therefore, even if the frequency spectrum from the external detector is subtracted from the frequency spectrum from the built-in detector, the high frequency component of the internal partial discharge remains.

In addition, since the frequency spectrum of the external partial discharge obtained from each built-in detector provided for each of the three phases is almost the same as its pattern and detection level, by subtracting the spectrum of each phase from each other, In the remaining spectrum, the frequency component of the external partial discharge is removed, and a pattern is obtained in which only the high frequency component of the partial discharge inside the device remains.

According to the above-described method, it is possible to accurately determine the external and internal partial discharges.

〔Example〕

FIG. 1 shows an embodiment of a spectrum subtraction type partial discharge monitoring system according to the present invention. A part of one phase of a three-phase gas-insulated bus at a line entrance of a gas-insulated substation, in which a high-voltage conductor 3 insulated and supported by an insulating spacer 2 is inserted into a grounding tank 1, and SF ₆ gas or the like is inserted. Is a gas insulated device 4 in which an insulating medium is enclosed, and is provided with a power feeding bushing 6 from a power transmission line 5.

As means for detecting such partial discharge of the gas insulated equipment, a coupling electrode 8 is provided inside the terminal plate 7 at the end of the bus bar.
And a built-in detector 11 configured to insulate and support the insulating member 9 and to lead the potential of the coupling electrode 8 to the outside of the apparatus via an insulating terminal 10. 4 is provided with an antenna-type external detector 12 in the vicinity of the outside.

The detection signals obtained from the detectors 11 and 12 are taken into a partial discharge determination device 13 of a spectrum subtraction type.

The partial discharge determination device 13 includes a broadband amplifier 14 that amplifies the signals obtained from the detectors 11 and 12 in a wide band, a frequency spectrum analyzer 15 that analyzes the frequency spectrum of the output signal, and a spectrum analyzer that analyzes the frequency spectrum of the two signals. Frequency spectrum subtraction unit 16 to be subtracted, residual spectrum determination unit 17 that determines the residual spectrum after spectrum subtraction, fetches information after the residual spectrum determination,
A monitoring display unit 19 for comparing and judging with preset information of the comparing and judging unit 18 to monitor the partial discharge and for displaying the result.
It is composed of

FIG. 3 shows an actual measurement example of a frequency spectrum of a detection signal obtained from the built-in detector 11. FIG. 3 (a) shows a case where a partial discharge is generated outside the power line 5 by 400 pe.
(B) shows a spectrum pattern when a partial discharge is generated from the surface of the high-voltage conductor 3 inside the device to the inside of 8 pc, and (c) shows a spectrum pattern when the above-mentioned external and internal partial discharges are simultaneously generated. ing. Than like, external people minute discharge whereas illustrates a spectrum pattern of about 400MHz less low frequency component _(L component) is enhanced, the high-frequency component _(L component of the partial discharge hundreds MHz generated inside the equipment ) Has a maximum value in the so-called high frequency band of 500 MHz to 1500 MHz, and its envelope is represented by a characteristic spectrum pattern indicated by a substantially mountain shape.

Therefore, by monitoring whether or not the above-described _H component pattern exists in the frequency spectrum of the detection signal, it is possible to determine the internal abnormality.

Also, the _L component and _H in the spectrum of (c)
Since the components are shown in a pattern similar to the individual spectra shown in (a) and (b), the spectrum of (b) is left by subtracting the spectrum of (a) from the spectrum of (c). It is possible to do.

The partial discharge determination device 13, which is a system of the present invention, shows a basic configuration built on the basis of the above experimental facts. Hereinafter, the basic operation of the present system will be described based on actual measurement examples.

The detection signals obtained from the detectors 11 and 12 are taken into the partial discharge judging device 13, and the frequency spectrum analysis unit 15 analyzes the frequency spectrum of each detection signal.
The spectrums (a) and (b) shown in the figure are obtained.
Further, both the spectra are taken into the frequency spectrum subtracting section 16 and the (b) spectrum is subtracted from the (a) spectrum. The remaining spectrum after the subtraction is judged by the remaining spectrum judging section 18 whether or not there is an _H component. In the case of the present embodiment, since the spectrum pattern in which the _H component remains in the remaining spectrum shown in FIG. 4C is shown, the comparison and judgment section 18 judges that there is an abnormality inside the device, and the monitor and display section 19 shows A display indicating an abnormality is performed.

According to the present embodiment, since it is easy to distinguish between an external partial discharge and an internal partial discharge, there is an effect that an abnormality in the device can be accurately detected. Further, an effect that a standing wave generated in a field, an external noise generated irregularly, and the like can be removed by a subtraction process is added.

Next, an application example in which functions are added to the basic system of FIG. 1 will be described with reference to FIG.

Fig. 5 shows a part of the three-phase bus (U-phase, V-phase, W-phase) at the line entrance of the gas insulated substation, and each bus has a built-in type detection as shown in Fig. 1. In addition to the configuration including the detectors 11U, 11V, and 11W, the partial discharge determination device 13A in which the detection signal from each detector is incorporated is further provided with the basic partial discharge determination device 13 shown in FIG. Unit 20, spectrum type comparison unit 21, _L and _H component level determination unit 22, peak value comparison operation unit 23, threshold value determination unit
It has a system configuration with 24,25. Hereinafter, the operation of this system will be described with reference to the flowchart of FIG. When the system is driven, an analysis of the frequency spectrum of each detection signal first taken from each detector is performed. Here, the spectrums of the detection signals obtained from the detectors 11U, 11V, and 11W are divided into five patterns as shown in FIG.
Is obtained. That is, when no partial discharge occurs inside and outside, a pattern having only the background noise (BGN) level indicated by the type is obtained. Also,
The type is a pattern in which only an external partial discharge is generated. Since no _H component is contained, the pattern indicates that no partial discharge is generated inside the device. The type indicates a pattern in which the internal partial discharge is emphasized, indicating that some abnormality has occurred inside the device. The type is a pattern in which a relatively large level of an internal partial discharge is superimposed on a small level of an external partial discharge or a minute level _L component having an internal partial discharge is manifested. If this is done, it is determined that an abnormality has occurred inside. Further, the type is a pattern obtained when an external partial discharge having an _H component or a large level external partial discharge and a small level internal partial discharge are superimposed, and it is not possible to determine an internal abnormality from this pattern. Difficult.

Therefore, a method of discriminating and classifying detection signals at the time of spectrum analysis based on the five types of patterns as described above is adopted. for type level comparison of the level h ₁ level h ₂ and _H components of the _L component is performed, in the case of the type pattern h _1> h ₂ is determined that there is abnormality in the interior. In addition, since it is not possible to determine whether the pattern is inside or outside from a pattern of the type where h ₁ <h ₂ , the pattern is further led to the next determination route.

In the next step, first, the level S ₁ of _H-component contained in the type is to compare determined threshold value K ₁ set whether exceeds a detrimental level equipment beforehand. That is, as shown in FIG.
The band is set as the monitoring range, and if S ₁ <K ₁ , it is determined that there is no abnormality without determining whether the inside or outside is inside. In addition, as shown in the figure S ₁
> For K _1, further guided to the next discrimination route.

Note that so far has been determined in the course of determination route inside there is an abnormality, also in type, and comparison and determination the _H component levels S ₁ and the threshold K _1, S ₁ <When the K ₁ is no abnormality, when the S _1> K ₁ is determined there is an abnormality.

It is assumed that the above determination flow is individually performed for detection signals obtained from the detectors provided for each phase.

Next, when a pattern of a type having an _H component satisfying S ₁ <K ₁ is obtained in the three-phase detection signals, a subtraction process of each phase spectrum is performed in the next step.
Further, it is determined whether or not the _H component S ₂ exceeds the threshold value K ₂ present in ninth the comparing and monitoring frequency bands of the residual spectrum after subtraction processed as shown in the figure, when S ₂ <K ₂ is When there is no abnormality, and when S ₂ > K ₂ , it is determined that there is an abnormality.

As a method of subtracting the spectrum, one of the three phases is set as a reference phase, and the remaining spectrum is obtained by subtracting the frequency spectrum of the other phase from that of the reference phase. If a large phase is judged abnormal,
Alternatively, the three-phase spectra may be subtracted from each other, and the phase having the largest absolute value of the remaining spectrum may be determined to be abnormal. In addition, their absolute values are based on the threshold values described above.
By the comparison and determination of the K ₂ is connexion processing.

According to the present embodiment, there is an effect that a partial discharge generated inside and outside the device and the device can be reliably determined, and an abnormal phase can be accurately located.

Further, another embodiment will be described. If the frequency spectrum patterns of the detection signals obtained from the three-phase detectors are both of the type and the _H component exceeding the threshold is shown at the same level, the remaining spectrum after the subtraction processing cannot leave the _H component. Therefore, it may not be possible to determine the presence or absence of an internal abnormality. In consideration of such a situation, the system is provided with an external detector as shown in FIG. 1, and the detection signal from the external detector is incorporated into the system 13A. When the type of the condition appears, the detection signal spectrum from the external detector is subtracted from the detection signal spectrum from the built-in detector provided for each phase. That is,
As shown in FIG. 10, _H generated by the internal partial discharge
The component detection sensitivity differs between the built-in detector and the external detector, and the former detection level is always higher than the latter detection level. On the other hand, the detection sensitivity of the _H component generated by the external partial discharge has a characteristic that the external detector is larger than the built-in detector. Therefore, the remaining spectrum obtained by subtracting the spectrum of the external detector from the spectrum of the built-in detector has a spectrum in which the _H component remains when there is an abnormality inside.
On the other hand, _{the H} component in the residual spectrum For _H component contained in the external partial discharge does not remain.

According to this embodiment, it is possible to further improve the accuracy of discriminating between external and internal partial discharges, and to further improve the reliability of the present system.

The number of external detectors may be one. However, in order to determine the abnormal state of each phase with higher accuracy, it is desirable to provide a configuration provided near each phase.

Further, as another embodiment, frequency spectra in a steady state under various conditions in a normal operation state are preliminarily captured, subtracted from each other according to the conditions at the time of capturing a detection signal, and the remaining spectrum exceeds a threshold value.
_{If the H} component remains, it can be determined that there is an abnormality in the device. According to the present embodiment, since it is possible to make a determination in response to a change in the surrounding conditions, there is an effect that the accuracy of determining an internal abnormality can be further improved.

〔The invention's effect〕

According to the present invention, by using a built-in detector,
In addition to being able to detect minute partial discharges in equipment with high sensitivity,
By analyzing the frequency spectrum of the detection signal and pattern-recognizing whether or not a high frequency component is included in the 500 MHz to 1500 MHz band of the frequency spectrum, it is possible to determine an abnormal situation inside the device. In addition, by subtracting the frequency spectrum of the detection signals obtained from a plurality of detectors from each other, broadcast waves and communication waves, extraneous noise that enters irregularly, and partial discharge generated outside the device can be used to reduce the This has the effect that the state of occurrence of internal and external discharges can be accurately determined.

Further, since the present partial discharge monitoring system is configured using a computer, automatic monitoring is possible.

By introducing this system to a gas-insulated substation,
Since an abnormality sign inside the device can be quickly predicted, there is an effect that an accident of the device can be prevented beforehand.

[Brief description of the drawings]

FIG. 1 is a block diagram of a basic partial discharge monitoring system applied to a gas insulated device showing one embodiment of the present invention, FIG. 2 is a diagram showing a typical type of spectrum obtained from a built-in detector, and FIG. Is a measured spectrum diagram of the internal and external split discharge, FIG. 4 is a diagram showing a measured example of the spectrum subtraction process,
FIG. 5 is a block diagram of a system when the present invention is applied to a phase separation type gas insulated equipment, FIG. 6 is a flowchart showing an operation procedure of the system configuration shown in FIG. 5, and FIG. 7 is a built-in detector. FIGS. 8 and 9 show examples of discrimination with a threshold, and FIG.
FIG. 10 is a diagram showing a detection level ratio between the built-in type detector and the external type detector. 1 ... ground tank, 2 ... insulating spacer, 3 ... high voltage conductor, 4 ... gas insulated equipment, 11,11U, 11V, 11W ... internal detector, 12 ... external detector, 13, 13A ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. Display unit, 20: spectrum pattern determination unit, 21: spectrum type comparison unit, 22: _L and _H component level determination unit, 23: peak value comparison calculation unit, 24, 25: threshold value determination unit .

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Keisho Endo 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Tokio Yamagoku 1-1-1, Kokubuncho, Hitachi City, Ibaraki Prefecture In the Kokubu Factory of Hitachi, Ltd. (56) References JP-A-55-86316 (JP, A) JP-A-59-2518 (JP, A) JP-A-61-147170 (JP, A) JP-A-59 −28832 (JP, A)

Claims (8)

(57) [Claims] 1. A gas insulated device in which a high-voltage conductor supported by an insulating spacer is disposed in a ground tank in which an insulating medium is sealed, and wherein a first detector for detecting a partial discharge installed in the ground tank is provided. A second detector for detecting a partial discharge grounded outside the grounding tank, a frequency spectrum analyzer for obtaining a frequency spectrum of a signal of the first and second detectors, A residual spectrum calculation unit for obtaining a residual spectrum by subtraction, a frequency band of the residual spectrum, including a determination unit for determining an internal partial discharge based on a peak value, wherein the residual spectrum has a peak in a high frequency band of 500 MHz to 1500 MHz. A spectrum subtraction type partial discharge monitoring system characterized in that a case where only a frequency band component remains is determined to be abnormal. 2. A gas insulated device in which a high-voltage conductor supported by an insulating spacer is disposed in a grounding tank in which an insulating medium is sealed, wherein the first detector detects partial discharge installed in the grounding tank. A second detector for detecting a partial discharge grounded outside the grounding tank, a frequency spectrum analyzer for obtaining a frequency spectrum of a signal of the first and second detectors, A residual spectrum calculation unit that obtains a residual spectrum by subtraction, a frequency band of the residual spectrum, including a determination unit that determines an internal partial discharge by a peak value, wherein the peak of a high frequency band component of 500 MHz to 1500 MHz is included in the residual spectrum. A spectrum subtraction method characterized in that a case where the peak is larger than a peak of a low frequency band component lower than a high frequency band component is determined to be abnormal. Type partial discharge monitoring system. 3. The method according to claim 1, wherein the remaining spectrum is 500 MHz to 1500 MHz.
3. A partial discharge monitoring system according to claim 1, wherein a subtraction process is performed when the peak of the high frequency band component exceeds a threshold value. 4. The partial discharge monitoring system according to claim 1, wherein the second detector is a detector provided near the outside of the gas insulated device and for detecting a spatial electromagnetic wave. 5. The spectrum subtraction method according to claim 1, wherein a first detector for detecting the spatial electromagnetic wave is provided for each phase and arithmetic processing is performed for each phase. Partial discharge monitoring system. 6. The apparatus according to claim 1, wherein when the frequency spectrum of the detection signal obtained from said detector is represented by only a low-frequency band component, it is determined that there is no abnormality without performing arithmetic processing. Or the spectrum subtraction type partial discharge monitoring system according to 2. 7. A three-phase detector for a gas-insulated apparatus in which high-voltage conductors supported by insulating spacers are arranged in a grounded tank in which an insulating medium is sealed, wherein the three-phase detector is provided. An abnormal phase is determined by subtracting the frequency spectrum of the detection signal of the detector of each phase from each other, and one of the three-phase gas-insulated devices is set as a reference phase, and the other phase is set as a reference phase. A spectrum subtraction type partial discharge monitoring system, characterized in that a phase having a large residual among the absolute values of a frequency spectrum and a frequency spectrum of a reference phase is determined to be abnormal. 8. A three-phase detector for a gas-insulated apparatus in which high-voltage conductors supported by insulating spacers are arranged in a ground tank in which an insulating medium is sealed. An abnormal phase is determined by subtracting the frequency spectrum of the detection signal of each phase detector from each other, and the frequency spectrum of the three-phase gas insulated equipment is subtracted from each other, and the absolute value of the residual spectrum is determined. A spectrum subtraction type partial discharge monitoring system wherein the largest phase is determined to be abnormal.