JPH03251011A - Partial discharge detector - Google Patents

Abstract

PURPOSE:To detect partial discharge pulse with high precision without being influenced by external noise by arranging a floating electrode for detecting partial discharge and commercial frequency signal, a partial discharge detecting section, a main circuit voltage phase detecting section from the commercial frequency signal, and an arithmetic section for measuring the partial discharge of an arbitrary phase. CONSTITUTION:When partial discharge is generated in the internal section of the equipment of a gas insulating switchgear, then high frequency signal is superposed on commercial frequency, and the input to a detecting section 7a is provided. Then, by band-pass filters 13, 20 in the detecting section 7a, the signal of specific frequency including partial discharge pulse, and the commercial frequency are separated from each other. The output of the specific frequency signal including the partial discharge pulse is generated as light signal in an E/O converting circuit 18, and commercial frequency signal is shaped in a pulse shaping circuit 23 and is fed to signal receiving section 7b through an optical fiber 19. By an arithmetic section 29, a measuring start time and a measuring time interval are controlled, and by the output of an A/D converting section 28, partial discharge generation is discriminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a partial discharge detector used for detecting partial discharge generated inside a gas-insulated switchgear.

(Conventional technology) In recent years, due to the need to strengthen substation equipment due to the soaring cost of land and the increase in power supply in urban areas, SF6 gas, which has excellent insulation and arc extinguishing properties, has been used to So-called gas-insulated switchgears have become popular and in operation, in which substation equipment such as transformers are housed in a sealed container, and the volume is compact due to environmental resistance and installation per kV-A.

Although the gas-insulated switchgear described above has advantages such as being compact and eliminating exposed live parts in the grounded tank, it also has the disadvantages of making maintenance diagnosis difficult due to higher performance, increasing the time required for maintenance and repair work, etc. There is a drawback that reliability is significantly reduced when an abnormality occurs.

Therefore, in order to improve the reliability of gas-insulated switchgear as a whole, efforts have been made to appropriately design and manufacture the equipment. Confirmation and monitoring are necessary, and various effective means have been studied.

One such means is a partial discharge detector used to detect partial discharge occurring inside a gas insulated switchgear. FIG. 5 shows an example of a conventional partial discharge detector. That is, a typical closed gas switch is housed in a metal container 1, which is electrically divided by insulating spacers 2 and connected in the longitudinal direction. Further, inside the metal container 1, a center conductor 3, which is a high voltage charging part electrically connected to a power transmission line (not shown), is supported by the insulating spacer 2. Note that the metal container 1 is grounded by a grounding wire (not shown). Further, the insulating spacer 2 is provided with an electrode 4 for voltage detection, and a stray capacitance C2 exists between the electrode 4 and the metal container 1, and this stray capacitance C2 is shown as a capacitor 5. . A partial discharge detector 7 is connected to both terminals of the capacitor 5 via a signal lead-in line 6 . The partial discharge detection section 7 is configured by connecting a filter 8 to an amplifier circuit 9 to extract a signal of a specific frequency, and further connecting a peak detector and an integrating circuit/O. Further, a power source 11 is connected to these devices.

The conventional partial discharge detector configured in this manner operates as described below. That is, when a high voltage is applied to the center conductor 3, the stray capacitance C1 existing between the center conductor 3 and the electrode 4 and the capacitor 5 constitute a voltage divider, and a shared voltage is generated across the capacitor 5. When a partial discharge pulse (corona pulse) occurs in the switch, a high frequency component (signal) resulting from the discharge is superimposed on this shared voltage, and is input to the partial discharge detection section 7. In this partial discharge detection section 7, a signal of a specific frequency corresponding to a partial discharge pulse is extracted by a filter 8, amplified by an amplifier circuit 9, and then outputted to the outside via a peak detector and an integrating circuit/O. And with this output signal,
It is possible to detect that partial discharge has occurred inside the switch.

(Problems to be Solved by the Invention) However, in the conventional partial discharge detector as described above, there are problems to be solved as described below.

First, conventional partial discharge detectors detect a signal of a specific frequency corresponding to a partial discharge pulse at a predetermined timing, then integrate it over an arbitrary time width and output it, so it is difficult to determine the phase of partial discharge occurrence. Can not. However, the form of partial discharge pulses that occur due to abnormalities on the main equipment side has a close relationship with the main circuit voltage waveform (phase) depending on the type of abnormality, as shown in Figure 6 for example. On the other hand, external noise that interferes with partial discharge measurements is
It often occurs randomly, regardless of the main circuit voltage phase. Therefore, even if you simply extract a signal at a specific frequency from a partial discharge detector like in the past, it may contain external noise, making it difficult to perform highly accurate partial discharge detection. there were. In addition, even if only the presence or absence of a signal of a specific frequency is detected regardless of the main circuit voltage phase, it is not possible to determine the relationship between the phase and the discharge pulse as shown in Figure 7 above, so it is not possible to determine the cause of partial discharge. It was impossible to guess.

In addition, conventional partial discharge detectors directly transmit the detected partial discharge pulse using an optical cable, but since the actual partial discharge pulse has a pulse width of several ns/Ons or less, the signal cannot be stabilized. It is difficult to transmit light. In other words, although it is technically possible to convert such high-speed pulses into optical signals, if corona pulses are simply converted into optical signals and transmitted in an analog manner, attenuation due to the length of the optical cable, optical connectors, etc. The influence becomes large, and it is necessary to make on-site adjustments for each sensor.Furthermore, each time the optical connector is attached or detached, the amount of attenuation in the connector section changes, making it impossible to make accurate measurements.

The present invention has been made in view of the above-mentioned prior art, and its first purpose is to be able to detect partial discharge pulses with high precision without being affected by external noise, and to detect the cause of partial discharge occurrence. The purpose is to submit a partial discharge detector that can be used to investigate the situation.

A second object of the present invention is that even when optically transmitting a detected partial discharge signal, it is possible to eliminate the effects of attenuation due to the length of the optical cable, fluctuations in attenuation due to the optical connector, etc., and to accurately transmit the detected partial discharge signal. It is an object of the present invention to provide a partial discharge detector capable of detecting partial discharge.

[Structure of the Invention (Means for Solving the Problem) In order to achieve the above object, the invention of claim 1 provides an insulating spacer section or a grounded metal container provided in an insulated state from the grounded metal container. a floating electrode that detects both the partial discharge signal and the commercial frequency signal, and a partial discharge detection section that is connected to the floating electrode and separates and detects the partial discharge signal from both the partial discharge signal and the commercial frequency signal. , a main circuit voltage phase detection unit connected to the floating electrode, which separates the commercial frequency signal from both the partial discharge signal and the commercial frequency signal, and detects a main circuit voltage phase signal from the commercial frequency signal; The present invention is characterized in that it includes a partial discharge detection section and a calculation section that measures partial discharge of an arbitrary phase based on the partial discharge signal from the main circuit voltage phase detection section and the main circuit voltage phase signal.

Further, the invention of claim 2 provides that the partial discharge detection unit and the main circuit voltage phase detection unit in the invention of claim 1 include a bandpass filter that detects a signal in a specific frequency band from the partial discharge signal and the commercial frequency signal; A peak-hold circuit or an integrating circuit converts the output signal from this band-pass filter into a pulse signal with an arbitrary time width, and a voltage converter that frequency-modulates the output signal of this peak-hold circuit or integrating circuit and outputs it as an optical signal. F converter and E/
The device is characterized in that it is equipped with an O converter.

(Function) According to the invention of claim 1 having the above configuration, a partial discharge signal and a commercial frequency signal are detected from the same floating electrode, and a reference corresponding to the main circuit voltage phase created from the commercial frequency signal is detected. By measuring partial discharges at arbitrary phases based on pulses, it is possible to distinguish between external noise and partial discharge pulses, and also to determine what pattern partial discharges occur in relation to the main circuit voltage phase. You can know.

In addition, in order to measure the partial discharge pulse in correspondence with the phase of the main circuit commercial frequency voltage, it is necessary to
//Since pulse resolution of about O0 is sufficient,
According to the second aspect of the invention, the pulse signal for optical transmission is obtained by peak-holding or integrating the partial discharge pulse within such a time width.
Since it is possible to perform E/O conversion after F conversion and transmit it to the receiver side in a form close to a digital signal, the effects of attenuation due to the optical cable length and fluctuations in attenuation due to the optical connector described above are eliminated. be able to.

(Example) Hereinafter, an example of the present invention will be specifically described with reference to FIGS. 1 to 3.

A general closed type gas switch is housed in a metal container 1,
This metal container 1 is electrically divided by insulating spacers 2 and connected in the longitudinal direction. Further, inside the metal container 1, a center conductor 3, which is a high voltage charging part electrically connected to a power transmission line (not shown), is placed between the insulating spacer 2
Supported by Note that the metal container 1 is grounded by a grounding wire (not shown). Further, the insulating spacer 2 is provided with a floating electrode 4 for partial discharge detection, and a stray capacitance C2 exists between the floating electrode 4 and the metal container 1, and this stray capacitance C2 is shown as a capacitor 5. has been done. A detection unit 7a is connected to both terminals of the capacitor 5 via a signal lead-in line 6. This detection section 7a is composed of a partial discharge detection section and a main circuit voltage phase detection section, and the signal is transmitted from the same floating electrode 4.
It has a configuration that provides better results.

First, the partial discharge detection section is connected to a transformer 12 for separating a high frequency signal component from the signal detected by the floating electrode 4 and sending it to the subsequent electronic circuit section, and is connected to this transformer 12, A bandpass filter 13 is provided for extracting a signal in a specific frequency band corresponding to a discharge pulse (which may include a partial discharge pulse and noise). Connected to this bandpass filter 13 are an amplifier 14 and a detection circuit 15 that process the signal of the specific frequency, and an integrating circuit or peak hold circuit 16 that converts the signal of the specific frequency into a constant pulse width. Further, this integration circuit or peak hold circuit 16 includes a V/F conversion circuit 17 that modulates the pulse signal of a specific frequency obtained as described above, and an E/O that converts this modulated signal into an optical signal. The conversion circuit 18 transfers this optical signal to the receiving section 7.
An optical fiber 19 is provided for transmitting data to b.

On the other hand, the main circuit voltage phase detection section, like the partial discharge detection section, includes a transformer 12 for separating a high frequency signal component from the signal detected by the floating electrode 4 and sending it to the subsequent electronic circuit section;
A bandpass filter 20 is connected to the transformer 12 and extracts only the commercial frequency from the high frequency signal. This bandpass filter 20 includes an amplifier 21, a comparator 22 that detects a specific phase of the commercial frequency as a pulse,
A pulse shaping circuit 23 for shaping the detected pulse is connected. Furthermore, this pulse shaping circuit 23 includes a V/F conversion circuit 17 that modulates the voltage phase pulse signal obtained by the pulse shaping circuit 23, similar to the partial discharge detection section.
, an E/O conversion circuit 18 that converts this modulated signal into an optical signal, and an optical fiber 19 that transmits this optical signal to the receiving section 7b.

In addition, in the figure, 31 is a converter that converts the supplied power into an arbitrary voltage.

The receiving section 7b includes an O/E section 2 that converts a signal of a specific frequency sent from the partial discharge detection section of the inspection section 7a into an electrical signal.
4 and an F/V conversion circuit 25 are provided, and these circuits are connected via an amplifier 26 to an integration circuit 27, an A/D conversion section 28,
and is connected to the arithmetic unit 29. In addition, the receiving section 7b
is provided with an O/E section 24 and an F/V conversion circuit 25 to convert the voltage phase pulse signal from the main circuit voltage phase detection section into an electrical signal, and these circuits convert the amplifier 26 and the waveform shaping circuit 30 into electrical signals. It is connected to the arithmetic unit 29 via.

The partial discharge detector of this embodiment having such a configuration is as follows:
It works as follows.

When a partial discharge occurs inside a gas-insulated switchgear, a high-frequency signal containing all frequency components is superimposed on the commercial frequency as shown in FIG.
is input. This signal is separated by bandpass filters 13 and 20 provided in the detection unit 7a into a signal of a specific frequency including the partial discharge pulse and a commercial frequency. Among these, signals of specific frequencies that may include partial discharge pulses and their noise are measured in real time, amplified and detected by an amplifier 14 and a detection circuit 15, and then phased by an integrating circuit or a peak hold circuit 16. Time width that can be measured by resolution, for example, from /0 minutes to /00 minutes of one cycle
The peak is held below, and then V/F conversion circuit 1
7, the signal is outputted as an optical signal by the E/O conversion circuit 18, and sent to the receiving section 7b through the optical fiber 19.

On the other hand, the commercial frequency detected by the bandpass filter 20 is amplified by the amplifier 21, and then a certain phase, for example, the phase of the zero cross point, is detected by the comparator 22 as a voltage phase pulse, and this voltage phase pulse is The waveform is shaped by the shaping circuit 23. After that, this voltage phase pulse is modulated by the V/F conversion circuit 17, and then outputted as an optical signal by the E/O conversion circuit 18, and the optical fiber 1
9 to the receiving section 7b. In the receiver 7b, the optically transmitted pulses of a specific frequency including the partial discharge pulse and the voltage phase pulse are processed by the O/E section 24, the F/V conversion circuit 25, and the amplifier 26, respectively. The signal is inversely converted into an electrical signal that can be processed by the arithmetic unit 29.

From both pulse signals obtained as above, the computing unit 2
9 to detect partial discharge as shown in FIG. First, pulses of a specific frequency, including partial discharge pulses, are
In the integrating circuit 27 of the receiving section 7b, the signal is shaped into a rectangular wave pulse as shown at P3 in FIG. On the other hand, based on the voltage phase pulse output from the waveform shaping circuit 30 (in FIG. 3, the voltage phase pulse P1 is output for a certain period of time t1 at the zero crossing point), the calculation unit 29 outputs a measurement timing pulse P2. This measurement timing pulse P2 has a measurement start time t□ and a measurement time width t2 controlled by the arithmetic unit 29, and is the most of the phases of the main circuit voltage when viewed from the partial discharge pulse generation pattern shown in FIG. It is output in a range where partial discharge pulses may occur. Then, in the A/D converter 28, this measurement timing pulse P
Only while A2 is being output, a pulse signal of a specific frequency including a partial discharge pulse is converted to a digital value, and this A
Depending on the presence or absence of the output from the /D converter 28, it is determined whether a pulse signal of a specific frequency exists in the phase portion, in other words, whether a partial discharge has occurred.

That is, the signal of a specific frequency separated by the bandpass filter 13 of the detection unit 7a contains noise that becomes an obstacle in measuring partial discharge, and this is converted into a constant pulse signal by the peak hold circuit 16 or the like. However, the included noise will not be removed. However, performing the A/D converter on the pulse signal of a specific frequency only during the output of the measurement timing pulse P2 as described above is a problem in that the part of the main circuit voltage phase where partial discharge pulses are most likely to occur, that is, the noise This indicates that a pulse of a specific frequency exists in a phase part that is difficult to imagine. As a result, there is an extremely high probability that a pulse with this specific frequency can be determined to be a partial discharge pulse, and conventional partial discharge detectors, which were able to determine partial discharge simply by the presence or absence of a pulse with a specific frequency corresponding to a partial discharge pulse, The detection accuracy of partial discharge is significantly improved compared to the above.

Furthermore, since the generation pattern of the partial discharge pulse with respect to the main circuit voltage phase has the characteristics as shown in FIG. 6, the measurement timing pulse P2 can be changed by appropriately changing the measurement start time t1 and the measurement time width t2 By outputting a specific pattern to the range where partial discharge is expected to occur and detecting the presence or absence of pulses of the specific frequency in that part, it is possible to determine what pattern the partial discharge pulse is occurring in. The cause of the discharge occurrence can also be determined.

As explained above, in this embodiment, both a signal of a specific frequency including a partial discharge signal and a commercial frequency signal are detected from the same floating electrode embedded in an insulating spacer part, and a signal is generated from the commercial frequency signal. By measuring partial discharges at arbitrary phases based on the reference pulse corresponding to the main circuit voltage phase, phase analysis of partial discharges becomes possible, and a highly accurate and more reliable partial discharge detector can be provided. Further, in this embodiment, since the commercial frequency and the partial discharge signal are detected from the same electrode, there is an advantage that the detection section can be easily attached to the equipment.

(Other Embodiments) The present invention is not limited to the above-mentioned embodiments. For example, as shown in FIG. In addition, a plurality of floating electrodes 4 and partial discharge detectors may be provided, and each detector may be centrally connected to the receiver 7b via an optical fiber 19. In the embodiment shown in FIG. 4, which has such a configuration, it is possible to perform measurements at multiple locations in the main circuit at the same timing and perform differential processing on the data between each detection section, resulting in more reliable partial discharge detection. becomes possible.

Furthermore, in the embodiment shown in FIG. 1, E/O converters 18 with different optical frequencies are used, and the optical wave combiner is used to combine both optical signals, and the combined signals are transmitted through the same optical fiber. Transmit to receiver side, O/E on receiver side
It is also possible to provide an optical demultiplexer in front of the converter 24 to separate and process the respective signals. With this configuration, the partial discharge signal and the main circuit voltage phase signal can be transmitted using a single optical cable.

In addition, in the embodiment shown in FIG. 1, the phase pulse of the main circuit voltage is detected by the detection section, but the commercial frequency voltage signal is directly V/
It is also possible to perform F and E/O conversion and generate a phase signal on the receiver side.

Furthermore, as the floating electrode 4, in addition to the floating electrode buried in the insulating spacer 2 as shown in FIG.
As described in the above publication, it is also possible to use a structure in which a floating electrode is insulated and mounted between the metal container 1 and the center conductor 3. Further, a floating electrode may be provided on the surface of the insulating spacer 2 so as to be stuck thereto.

[Effects of the Invention] As described above, in the invention of claim 1, a partial discharge signal and a commercial frequency signal are detected from the same floating electrode arranged in an insulated state in an insulating spacer part or a grounded metal container, and a commercial frequency signal is detected. By measuring partial discharge of arbitrary phase based on the reference pulse corresponding to the main circuit voltage phase created from the frequency signal,
It is possible to provide a highly reliable partial discharge detector that has high detection accuracy and allows investigation of the cause of partial discharge occurrence.

Further, according to the invention of claim 2, since the partial discharge pulse having an extremely short pulse width is processed by the peak hold circuit or the integrating circuit to obtain a pulse signal for optical transmission, it has a form close to a digital signal. This enables optical transmission to the receiver side, eliminates the effects of attenuation due to the length of the optical cable and fluctuations in attenuation due to the optical connector, and provides a highly reliable partial discharge detector. .

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the partial discharge detector of the present invention, Fig. 2 is a graph showing the input and output waveforms of the detection section in the present invention, and Fig. 3 is the main circuit voltage phase and each detection pulse. FIG. 4 is a circuit diagram showing another embodiment of the present invention, FIG. 5 is a circuit diagram showing an example of a conventional partial discharge detector, and FIG. 6 is a graph showing the causes of partial discharge and partial discharge. 3 is a graph showing a pulse generation pattern. DESCRIPTION OF SYMBOLS 1... Metal container, 2... Insulating spacer, 3... Center conductor, 4... Floating electrode, 5... Capacitor, 6...
...Signal lead-in line, 7...Partial discharge detector, 7a...
・Detection section, 7b... Receiving section, 8... Filter, 9.
...Amplification circuit, /O...Peak detector and integration circuit, 11...Power supply. 12...Transformer, 13...Band pass filter, 1
4... Amplifier, 15... Detection circuit, 16... Integrating circuit or peak hold circuit, 17... V/F conversion circuit, 18... E/O conversion circuit, 19... Optical fiber 20 ...Band pass filter, 21...Amplifier, 22...Comparator, 23...Pulse shaping circuit, 24...O/E conversion circuit, 25...F/V conversion circuit, 26...・Amplifier, 27...Integrator circuit, 28・
... A/D conversion unit, 29... Arithmetic unit, 30... Waveform shaping circuit, 31... Converter. Figure 3

Claims (2)

[Claims] (1) In a partial discharge detector for a gas-insulated switchgear, which consists of a high-voltage charging part supported by an insulating spacer and housed in a grounded metal container filled with insulating gas, the A floating electrode is provided insulated from the grounded metal container and detects both the partial discharge signal and the commercial frequency signal. a partial discharge detection unit that separates and detects a discharge signal; and a partial discharge detection unit connected to the floating electrode, which separates the commercial frequency signal from both the partial discharge signal and the commercial frequency signal, and extracts a main circuit voltage phase signal from the commercial frequency signal. A main circuit voltage phase detection section for detecting the partial discharge, and a calculation section for measuring the partial discharge of an arbitrary phase based on the partial discharge signal and the main circuit voltage phase signal from the partial discharge detection section and the main circuit voltage phase detection section. A partial discharge detector characterized by: (2) The partial discharge detection section and the main circuit voltage phase detection section include a bandpass filter that detects a signal in a specific frequency band from the partial discharge signal and the commercial frequency signal, and an output signal from this bandpass filter at an arbitrary time. A peak hold circuit or an integrating circuit that converts the output signal into a pulse signal with a width, a V/F converter and an E/F converter that frequency modulates the output signal of this peak hold circuit or integrating circuit and outputs it as an optical signal.
The partial discharge detector according to claim 1, further comprising an O converter.