JP7804485B2 - Partial discharge detection device and partial discharge detection method - Google Patents

Description

The present invention relates to a partial discharge detection device for detecting internal partial discharges in high-voltage equipment, and in particular to a partial discharge detection device and partial discharge detection method that uses a transient ground voltage sensor to detect internal partial discharges in high-voltage equipment.

High-voltage equipment such as distribution boards, switchgear, transformers, and switching devices are used for long periods after installation, and as a result, they undergo deterioration over time, including a decline in insulation performance. It is generally known that a decline in the insulation performance of power equipment can lead to internal partial discharges. Repeated discharges (hereinafter referred to as internal partial discharges) within the high-voltage equipment that makes up power equipment can lead to insulation breakdown, which could lead to disasters such as fires. Therefore, to operate power equipment safely, it is important to accurately detect internal partial discharges in high-voltage equipment.

For example, Japanese Patent Laid-Open Publication No. 09-68556 (Patent Document 1) discloses the following technology for detecting internal partial discharges. Specifically, in three-phase power equipment, the output signals of three antennas corresponding to each phase are switched using a channel selector, output to a tuning amplifier, measured as digital data via an A/D converter, and frequency analysis is performed to determine whether internal partial discharges have occurred. If the evaluation value (average, etc.) obtained from the measured values is specifically high for only one antenna, it is determined that an insulation abnormality has occurred.

Furthermore, Japanese Patent Laid-Open Publication No. 10-210647 (Patent Document 2) discloses the following technology for detecting internal partial discharges. Specifically, the output signals from three antennas (corresponding to each phase of a three-phase power facility) and a noise antenna are switched using a selector, and measured via an amplifier, tuner, and A/D converter. Frequency analysis is performed to determine whether internal partial discharges have occurred, and the frequency points at which the noise antenna output level does not exceed a threshold value are determined as the measurement range. After that, the outputs of the three antennas are measured within the measurement range, and the occurrence of internal partial discharges is determined based on the average level of the measured values.

Japanese Patent Application Publication No. 09-68556 Japanese Patent Application Publication No. 10-210647

In order to detect internal partial discharges in high-voltage equipment, it has been proposed to use a transient ground voltage sensor attached to the wall inside the high-voltage equipment, such as a distribution board. However, when using this transient ground voltage sensor to detect internal partial discharges, it is necessary to address the following issues:

Electromagnetic waves around high-voltage equipment are a mixture of electromagnetic waves caused by internal partial discharges emitted from the surface of insulators inside the equipment or from inside the insulators, as well as external noise such as electromagnetic waves caused by air discharges that occur in parts exposed to the air, such as bushings, and communication waves. Detecting internal partial discharges requires separating and detecting external noise.

In addition, monitoring devices that monitor the detection signals of transient earth voltage sensors are often configured as one unit with the control devices inside the panel, and the sampling period for internal partial discharges may be set low at a few kHz to suit the monitoring or control device. However, because the electromagnetic waves caused by internal partial discharges are short-duration signals at a few MHz, setting the sampling period low poses the problem of making it difficult to reliably detect internal partial discharges.

The object of the present invention is to provide a partial discharge detection device and partial discharge detection method that can separate internal partial discharges from external noise and reliably detect internal partial discharges in situations where external noise and internal partial discharges coexist.

The present invention features a partial discharge detection device comprising: a transient ground voltage sensor provided in a high-voltage device for measuring transient ground voltage; partial discharge detection signal selection means for selecting a partial discharge detection signal related to an internal partial discharge from among the detection signals output by the transient ground voltage sensor; partial discharge occurrence detection means for detecting a partial discharge occurrence signal indicating the occurrence of an internal partial discharge from the selected partial discharge detection signal; partial discharge occurrence signal holding means for holding the detected partial discharge occurrence signal; and sampling means for sampling the partial discharge occurrence signal held in the partial discharge occurrence signal holding means at each predetermined sampling period.

The present invention makes it possible to separate internal partial discharges from external noise in situations where both external noise and internal partial discharges coexist, while also reliably detecting internal partial discharges.

1 is a block diagram showing the configuration of a partial discharge detection device according to a first embodiment of the present invention. FIG. 2 is an explanatory diagram illustrating a partial discharge signal and an air discharge signal measured by a TEV sensor. 5A and 5B are explanatory diagrams illustrating signal waveforms of a TEV sensor before and after passing through a low-pass filter. FIG. 2 is a configuration diagram showing a configuration of a baseline fluctuation suppression circuit. FIG. 10 is an explanatory diagram illustrating a state in which baseline fluctuations are suppressed. 10A and 10B are explanatory diagrams showing input and output signals of an integrating circuit and explaining the extension state of the time width of a detection signal. FIG. 10 is an explanatory diagram for explaining the concept of timing for capturing a partial discharge occurrence signal. FIG. 10 is a configuration diagram showing the configuration of a partial discharge detection system for detecting partial discharge in a high-voltage device according to a second embodiment of the present invention. FIG. 4 is an explanatory diagram illustrating detection signals of a first TEV sensor and a second TEV sensor. FIG. 10 is a block diagram showing the configuration of a partial discharge detection device according to a second embodiment of the present invention.

Embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments, and various modifications and applications within the technical concept of the present invention are also included within its scope. Furthermore, in each drawing, identical components will be designated by the same reference numerals, and detailed descriptions of overlapping parts will be omitted.

Figure 1 shows the configuration of a partial discharge detection device according to a first embodiment of the present invention. This embodiment describes an example in which internal partial discharges in high-voltage devices such as power receiving panels and switching equipment are detected using a transient earth voltage sensor (hereinafter referred to as a TEV sensor).

In Figure 1, the TEV sensor 12 has the function of outputting, as a voltage signal, a surface current induced on the surface of the metal wall 11 of the housing that constitutes the power receiving panel, switching device, etc. to which the TEV sensor 12 is attached. Here, the metal wall 11 of the housing is grounded. A detection circuit 10 is connected downstream of the TEV sensor 12.

The upstream side of the detection circuit 10 is provided with a high-pass filter 13, which removes external noise components near commercial frequencies, and a low-pass filter 15, which removes external noise components caused by aerial discharges. A 1x gain amplifier 14 is provided between the high-pass filter 13 and low-pass filter 15 for the purpose of impedance separation. This eliminates interaction between the high-pass filter 13 and low-pass filter 15. In this way, the high-pass filter 13 to low-pass filter 15 have the function of removing external noise, allowing detection signals related to internal partial discharges to be sent to downstream circuit elements.

Resistive element R1, capacitor C1, and selector switches 16 and 17 are provided downstream of the low-pass filter 15 to suppress baseline fluctuations in the signal from the TEV sensor 12. These elements function to suppress baseline fluctuations. The selector switches 16 and 17 consist of an output switch 16 that outputs the input signal from the low-pass filter 15, and a ground switch 17.

The output switch 16 and ground switch 17 perform opposite operations when the appropriate timing arrives, and are operated by a switching signal from the monitoring device 23, which will be described later. When the output switch 16 is "on," the ground switch 17 is "off," and a partial discharge detection signal is output to the downstream comparator 18.

On the other hand, when the output switch 16 is in the "off" state, the ground switch 17 is "on" and the partial discharge detection signal is not output to the comparator 18. If the partial discharge detection signal is not output, the transient ground voltage sensor 12 is in a grounded state and the offset is "0 V."

The operation timing of these changeover switches 16 and 17 can be any cycle, but can also be determined in conjunction with the timing of reset switches 21 and 22, which will be described later. The timing of reset switches 21 and 22 is synchronized with the sampling cycle of monitoring device 23.

The components from the high-pass filter 13 to the selector switches 16 and 17 function as a "partial discharge detection signal selection means" that selects a partial discharge detection signal related to internal partial discharge from among the input signals input to the transient ground voltage sensor. Note that resistor R1, capacitor C1, and selector switches 16 and 17 can be omitted if not required.

A comparator 18 is provided downstream of the selector switches 16 and 17, and determines that a partial discharge detection signal that is equal to or greater than a predetermined threshold is a partial discharge occurrence signal. The comparator 18 functions as a "partial discharge occurrence detection means" that detects a partial discharge occurrence signal indicating the occurrence of an internal partial discharge from the selected partial discharge detection signal.

When it is determined that a partial discharge occurrence signal has occurred, this partial discharge occurrence signal is output to the downstream integration circuits 19 and 20 each time it occurs. The threshold setting of the comparator 18 can be changed via an external input. This threshold setting can be set in advance, for example, at the time of shipment, and in this embodiment it is set at the time of shipment. However, it can also be changed depending on the usage status and environmental conditions of the high-voltage device, etc.

Integration circuits 19 and 20 are connected downstream of the comparator 18. These integration circuits 19 and 20 are configured in a two-stage series connection, consisting of a first integration circuit 19 followed by a second integration circuit 20. The first integration circuit 19 has the function of extending the temporal signal width (time width) of the partial discharge occurrence signal, while the second integration circuit 20 has the function of storing charge based on the partial discharge occurrence signal. These integration circuits 10 and 20 function as "partial discharge occurrence signal holding means" that hold the partial discharge occurrence signal.

The first integrating circuit 19 is composed of resistors R2, R3, R4, and capacitor C2, with operational amplifier OP1 as its main element. The second integrating circuit 20 is composed of resistors R6, R7, and capacitor C3, with operational amplifier OP2 as its main element. Resistor R5 and capacitor C3 are interposed between the first integrating circuit 19 and second integrating circuit 20.

The second integration circuit 20 is further provided with a reset switch 21 arranged in parallel with resistor R6 and a reset switch 22 arranged in parallel with capacitor C3. The reset switches 21 and 22 are composed of photodiodes. The reset switches 21 and 22 discharge the charge accumulated in the second integration circuit 20, resetting it.

The amount of charge before this reset indicates the occurrence of an internal partial discharge and its intensity. The reset operation of reset switches 21 and 22 is synchronized with the sampling period of monitoring device 23, which detects the amount of charge at this time and determines whether an internal partial discharge has occurred. These function as "sampling means" that sample the partial discharge occurrence signal held in integration circuits 19 and 20.

Next, the operation of the detection circuit 10 shown in Figure 1 will be explained with reference to Figures 2 to 7. Figure 2 shows the partial discharge signal and air discharge signal of the high-voltage device output from the TEV sensor 12, Figure 3 shows the waveform of the detection signal from the TEV sensor 12 before and after passing through the low-pass filter, Figure 4 shows the configuration of the baseline fluctuation prevention circuit, Figure 5 shows the baseline fluctuation suppression state, Figure 6 shows a comparison of the time widths of the input and output signals by the integration circuit, and Figure 7 shows the concept of the detection timing of the detection device.

First, Figure 2 (A) shows the partial discharge detection signal inside the housing of the high-voltage device measured by the TEV sensor 12, and (B) shows the air discharge detection signal outside the housing of the high-voltage device. The high-frequency components are at the same frequency, 80 MHz for internal partial discharges and 90 MHz for air discharges, but the frequency components of the envelope components of the high-frequency vibrations are 4 MHz for internal partial discharges and 10 MHz for air discharges, a difference of approximately 2.5 times. Therefore, by distinguishing between the envelope frequency components, it is possible to select internal partial discharges.

In the case of an air discharge, the air discharge reaches the housing directly as electromagnetic waves, and the surface current induced on the surface of the housing is detected by the TEV sensor 12. In contrast, in the case of an internal partial discharge inside the housing, the electromagnetic waves of the internal partial discharge induce a surface current inside the housing, which leaks from bushings and other parts, propagating outside the housing and detected by the TEV sensor 12. In addition, a ground current component that flows into the housing via the housing's ground wire is also detected by the TEV sensor 12. This ground current component is a relatively low frequency component.

First, to remove external noise near commercial frequencies, the detection signal from the TEV sensor 12 is passed through a high-pass filter 13 with a cutoff frequency of several tens of kHz, thereby removing external noise components in the low-frequency band. Next, to separate internal partial discharges from air discharges, the signal is passed through a low-pass filter 15 with a cutoff frequency of 7 MHz to 9 MHz, thereby cutting out the envelope frequency components of air discharges and selecting and extracting the partial discharge detection signal.

As a result, the signal waveform of the TEV sensor 12 retains the envelope component of the partial discharge signal, as shown in Figure 3. The upper part of Figure 3 shows the partial discharge signal inside the housing of the high-voltage device measured by the TEV sensor 12, and the lower part shows the envelope component signal that has passed through the low-pass filter 15. The cutoff frequencies of the high-pass filter 13 and low-pass filter 15 vary depending on the usage situation and environmental conditions in which the high-voltage device is installed. It is preferable to use filters with variable cutoff frequencies. This makes it possible to change the cutoff frequencies as needed and improve detection accuracy.

In addition, in this embodiment, to prevent fluctuations in the baseline of the partial discharge detection signal, a baseline voltage fluctuation suppression circuit 24 consisting of resistor R1, capacitor C1, and selector switches 16 and 17, as shown in Figure 4, is provided downstream of the low-pass filter 15. This baseline suppression circuit 24 has the function of suppressing baseline voltage fluctuations.

The output switch 16, which outputs a partial discharge detection signal, and the ground switch 17 are selector switches. When the output switch 16 is in the "on" state, the ground switch 17 is "off" at the timing when the partial discharge detection signal is to be output. When the output switch 16 is in the "off" state and the partial discharge detection signal is not to be output, the ground switch 17 is "on". As a result, the TEV sensor 12 is in a grounded state, and the offset is "0V".

Figure 5 shows the operation of the baseline voltage fluctuation suppression circuit 24, which suppresses baseline fluctuations. Figure 5 (A) shows the partial discharge detection signal on the input side (a) of resistor R1 before passing through the baseline suppression circuit 24, indicating the influence of baseline voltage fluctuations.

Figure 5 (B) shows the partial discharge detection signal on the output side (b) of the output switch 16 after passing through the baseline voltage fluctuation suppression circuit 24, suppressing the effects of baseline voltage fluctuations. (C) shows the timing of the ground switch 17; when the ground switch is "off" (and conversely, the output switch 16 is "on"), the partial discharge detection signal is input to the downstream comparator 18.

The comparator 18 compares the partial discharge detection signal with a predetermined threshold value. The predetermined threshold value is used to determine whether an internal partial discharge has occurred, and if this threshold value is exceeded, it is deemed that an internal partial discharge has occurred. The partial discharge occurrence detection signal that the comparator 18 recognizes as indicating an internal partial discharge is then input to the first integration circuit 19. Here, the strength of the partial discharge signal to be determined may change depending on the usage status of the high-voltage device, environmental conditions, etc.; therefore, it is preferable that the threshold setting of the comparator 18 be adjustable.

The partial discharge occurrence signal output by the comparator 18 is input to the downstream integrator circuits 19 and 20, which expand the temporal signal width (time width). As mentioned above, the integrator circuits 19 and 20 are configured in two stages connected in series.

Then, the first-stage integration circuit 19 expands the time width of the partial discharge occurrence signal. The values of resistors R2, R3, and R4 and capacitor C2 connected to operational amplifier OP1 are set so that this time width can be sampled within the sampling period and bandwidth of the monitoring device 23.

Figure 6 shows the results of the simulation. For example, when an input signal with a time width of 125 ns was input to the input side of the integrator circuit 19, an output signal with a time width of 400 μs was output from the output side after passing through the integrator circuit 19. As such, it can be seen that the time width of the partial discharge occurrence signal from the comparator 18 is expanded to correspond to the sampling period.

Next, the second-stage integration circuit 20 accumulates charge due to the partial discharge occurrence signal. The intensity of the internal partial discharge can be determined based on the amount of this accumulated charge. The monitoring device 23 then captures the amount of accumulated charge as an output value of the internal partial discharge. The monitoring device 23 determines the intensity of the internal partial discharge based on the magnitude of this captured output value.

After the output value is captured, a reset signal is input from the monitoring device 23 to the second integration circuit 20, turning on the reset switches 12 and 13 and discharging the charge. In this way, by synchronizing the reset signal period with the sampling period of the monitoring device 23, detection accuracy can be improved.

Figure 7 explains the timing of capturing the charge accumulated by the integrating circuits 19 and 20.

When the reset signal from the monitoring device 23 falls, the output switch 16 is turned "on" and the ground switch 17 is turned "off," inputting a partial discharge occurrence signal to the integrating circuits 19 and 20. A signal acquisition period is then set for a predetermined time, and this state is maintained to accumulate charge based on the partial discharge occurrence signal. When the signal acquisition period ends, the output switch 16 is changed to "off" and the grounding switch 17 to "on." At this time, the charge accumulated in the second integrating circuit 20 is retained.

The accumulated charge is then captured in response to the arrival of a reset signal from the monitoring device 23. In this case, the accumulated charge is captured at the rising edge of the reset signal, and the accumulated charge is discharged at the falling edge, and this process is repeated. Through this operation, an output value based on the partial discharge occurrence signal is input to the monitoring device 23 at a sampling period of several kHz, making it possible to reliably detect the occurrence of internal partial discharge using a monitoring device installed in the high-voltage equipment, without the need for measuring equipment such as a high-speed oscilloscope.

Next, we will explain the second embodiment of the present invention. The second embodiment is characterized by the provision of a second TEV sensor that detects air discharge.

In Figure 8, the high-voltage device 25 is provided with electrodes 26 and 27, with an insulator 28 disposed between the electrodes for insulation. The housing of the high-voltage device 25 is provided with a first TEV sensor 12, which is connected to the monitoring device 23 via a transmission line 29. The high-voltage device 25 is connected to a power source 32 via a bushing 30 and an application line 31.

Furthermore, an external antenna 33 made of metal is provided around the periphery of the high-voltage device 25, to which a second TEV sensor 34 is attached. The second TEV sensor 34 is also connected to the monitoring device 23 via a transmission line 29. Note that electromagnetic waves Em1 due to internal partial discharges are emitted from the insulator 28, and electromagnetic waves EM2 due to air discharges are emitted from the bushing 30. Electromagnetic waves Em1 are measured by the first TEV sensor 12, and electromagnetic waves Em2 are measured by the second TEV sensor 34.

Figure 9 shows the detection signals of the first TEV sensor 12 and the second TEV sensor 34 when an internal partial discharge occurs. Figure 9 (A) shows the signal waveform of the first TEV sensor 12, and (B) shows the signal waveform of the second TEV sensor 34. When a small signal of, for example, about 20 pC is generated from the insulator 28 of the high-voltage device 25 due to an internal partial discharge, the first TEV sensor 12 detects a signal due to a surface current caused by electromagnetic waves reaching directly into the housing. On the other hand, the second TEV sensor 34 does not detect a signal due to an internal partial discharge. Therefore, the occurrence of an internal partial discharge can be detected from these behaviors.

Figure 10 shows the detection circuit of the second embodiment. The circuit configuration on the side of the first TEV sensor 12 is the same as that of the first embodiment, so a description will be omitted.

The detection device on the second TEV sensor 34 side has essentially the same circuit configuration as the first embodiment, from the high-pass filter 13 to before the comparator 18.

Specifically, a high-pass filter 35 is provided to remove external noise components near commercial frequencies, and a low-pass filter 37 is provided to remove external noise components. The low-pass filter 15 on the first TEV sensor 12 side has a cutoff frequency that passes the envelope components of the detection signal based on internal partial discharges and air discharges. The low-pass filter 37 on the second TEV sensor 34 side has a cutoff frequency that passes the envelope components of the detection signal based on air discharges.

In addition, a 1x gain amplifier 36 is provided between the high-pass filter 35 and the low-pass filter 37 for the purpose of impedance isolation. This eliminates interaction between the high-pass filter 35 and the low-pass filter 37.

Resistive element R1, capacitor C1, and selector switches 38 and 39 are provided downstream of the low-pass filter 37 to suppress baseline voltage fluctuations in the signal from the second TEV sensor 34. These circuit elements function to suppress baseline voltage fluctuations. The selector switches 38 and 39 consist of an output switch 38 that outputs the input signal from the low-pass filter 37, and a ground switch 39.

The output switch 38 and ground switch 37 perform opposite operations when the appropriate timing arrives, and are operated by a switching signal from the monitoring device 23, which will be described later. When the output switch 38 is "on," the ground switch 39 is "off," and an aerial discharge detection signal is output to the downstream comparator 18.

On the other hand, when the output switch 38 is in the "off" state, the ground switch 39 is "on" and the aerial discharge detection signal is not output to the comparator 18. If the aerial discharge detection signal is not output, the second TEV sensor 34 is in the grounded state and the offset is "0 V."

As shown in Figure 10, the inputs to the comparator 18 are the partial discharge detection signal from the first TEV sensor 12 and the air discharge detection signal from the second TEV sensor 34. If only the partial discharge detection signal from the first TEV sensor 12 exceeds the threshold, it is output to the downstream integration circuits 19 and 20 as an internal partial discharge.

On the other hand, in the case of an aerial discharge, the housing of the high-voltage device 25 also functions as an antenna, so if the aerial discharge detection signal from the first TEV sensor 12 and the aerial discharge detection signal from the second TEV sensor 34 simultaneously exceed the threshold, it is determined to be an aerial discharge and is not output to the downstream integration circuits 19 and 20. This makes it possible to distinguish between internal partial discharges and aerial discharges, and to confirm partial discharges using the monitoring device 23.

The features of the second embodiment shown in Figure 10 can be summarized as follows:

The device is characterized by comprising: a first transient ground voltage sensor provided in the high-voltage equipment for measuring transient ground voltage; high-voltage equipment-side discharge detection signal selection means for selecting discharge detection signals related to internal partial discharges and air discharges from among the detection signals output by the first transient ground voltage sensor; a second transient ground voltage sensor provided in an external antenna located outside the high-voltage equipment for detecting air discharges; external antenna-side discharge detection signal selection means for selecting discharge detection signals related to air discharges from among the detection signals output by the second transient ground voltage sensor; partial discharge occurrence detection means that receives as input the discharge detection signal from the external antenna-side discharge detection signal selection means and the discharge detection signal from the high-voltage equipment-side discharge detection signal selection means and detects the occurrence of an internal partial discharge from the combination of the discharge detection signal from the external antenna-side discharge detection signal selection means and the discharge detection signal from the high-voltage equipment-side discharge detection signal selection means; discharge occurrence signal holding means for holding the detected partial discharge occurrence signal; and sampling means for sampling the partial discharge occurrence signal held in the discharge occurrence signal holding means at each predetermined sampling period.

Furthermore, the detection circuits in the first and second embodiments can be implemented using an FPGA (Field Programmable Gate Array) and analog elements. This simplifies the process of changing circuit constants, etc., and allows circuit parameters to be set to suit the environment without changing elements on the board.

As described above, the present invention features a partial discharge detection device comprising: a transient ground voltage sensor provided in a high-voltage device for measuring transient ground voltage; partial discharge detection signal selection means for selecting a partial discharge detection signal related to an internal partial discharge from among the detection signals output by the transient ground voltage sensor; partial discharge occurrence detection means for detecting a partial discharge occurrence signal indicating the occurrence of an internal partial discharge from the selected partial discharge detection signal; partial discharge occurrence signal holding means for holding the detected partial discharge occurrence signal; and sampling means for sampling the partial discharge occurrence signal held in the partial discharge occurrence signal holding means at each predetermined sampling period.

This makes it possible to separate internal partial discharges from external noise in situations where external noise and internal partial discharges coexist, while also reliably detecting internal partial discharges.

The present invention is not limited to the several embodiments described above, and includes various modifications. The above embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the configurations described. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace other configurations with respect to the configuration of each embodiment.

10...Detection device, 11...Metal wall, 12...Transient ground voltage (TEV) sensor, 13...High-pass filter, 14...Amplifier, 15...Low-pass filter, 16...Output switch, 17...Ground switch, 18...Comparator, 19...First integrator circuit, 20...Second integrator circuit, 21...Reset switch, 22...Reset switch, 23...Monitoring device.

Claims (11)

a transient ground voltage sensor provided in the high voltage device for measuring a transient ground voltage;
a partial discharge detection signal selection means for selecting a partial discharge detection signal relating to an internal partial discharge by removing external noise components near commercial frequencies and external noise components due to air discharge from the detection signals output from the transient ground voltage sensor;
a partial discharge occurrence detection means for detecting a partial discharge occurrence signal indicating the occurrence of an internal partial discharge from the selected partial discharge detection signal;
a partial discharge occurrence signal holding means having an extension function for integrating the detected partial discharge occurrence signal to extend the temporal signal width, and an accumulation function for integrating and accumulating charge based on the extended partial discharge occurrence signal, and for holding the accumulated charge amount as the partial discharge occurrence signal;
a sampling means for sampling the partial discharge occurrence signal held in the partial discharge occurrence signal holding means at each predetermined sampling period ,
The partial discharge detection signal selection means is composed of a filtering means, and the filtering means comprises:
a high-pass filter that removes external noise near the commercial frequency from the detection signal from the transient ground voltage sensor;
a low-pass filter connected to the high-pass filter and configured to remove external noise due to air discharge;
The low-pass filter has a cutoff frequency equal to the envelope component of the frequency components of the detection signal from the high-pass filter.
A partial discharge detection device characterized by: The partial discharge detection device according to claim 1,
An amplifier with a gain of 1 is disposed between the high-pass filter and the low-pass filter.
A partial discharge detection device characterized by: The partial discharge detection device according to claim 1,
The partial discharge occurrence detection means is a comparator, and the comparator comprises:
The partial discharge detection signal from the low-pass filter is compared with a predetermined threshold value, and when the partial discharge detection signal exceeds the threshold value, it is determined that an internal partial discharge has occurred, and the partial discharge occurrence signal is output.
A partial discharge detection device characterized by: The partial discharge detection device according to claim 3,
A baseline voltage fluctuation suppression circuit is provided between the low-pass filter and the comparator to suppress baseline voltage fluctuations.
A partial discharge detection device characterized by: The partial discharge detection device according to claim 3,
the partial discharge occurrence signal holding means is composed of a first integrating circuit and a second integrating circuit connected in series,
the first integration circuit is connected to the comparator and has an extension function for extending a temporal signal width of the partial discharge occurrence signal from the comparator;
The second integration circuit connected to the first integration circuit has the accumulation function of accumulating the charge based on the partial discharge occurrence signal.
A partial discharge detection device characterized by: 6. The partial discharge detection device according to claim 5,
the sampling means is a monitoring device that monitors the occurrence of partial discharge,
The monitoring device acquires the amount of charge accumulated in the second integration circuit in synchronization with the sampling period, and when the amount of charge is acquired, the monitoring device discharges the charge accumulated in the second integration circuit.
A partial discharge detection device characterized by: 7. The partial discharge detection device according to claim 6,
The second integration circuit includes a reset switch for discharging the accumulated charge, and the charge is discharged by the reset switch in accordance with the sampling period.
A partial discharge detection device characterized by: The partial discharge detection device according to claim 7,
The partial discharge detection device according to claim 1, wherein the reset switch of the second integration circuit is composed of a photodiode. The partial discharge detection device according to claim 3,
The threshold value of the comparator can be changed externally.
A partial discharge detection device characterized by: a first transient ground voltage sensor provided in the high voltage device for measuring a transient ground voltage;
a high-voltage device-side discharge detection signal selection means for passing envelope components of the detection signals output from the first transient ground voltage sensor that are based on internal partial discharges and air discharges, and selecting discharge detection signals related to internal partial discharges and air discharges;
a second transient ground voltage sensor provided on an external antenna located outside the high voltage device for detecting air discharge;
an external antenna side discharge detection signal selection means for passing an envelope component of the detection signal based on an aerial discharge among the detection signals output from the second transient ground voltage sensor, and selecting the discharge detection signal related to the aerial discharge;
partial discharge occurrence detection means, which receives the discharge detection signal from the external antenna side discharge detection signal selection means and the discharge detection signal from the high voltage device side discharge detection signal selection means, and detects the occurrence of an internal partial discharge as a partial discharge occurrence signal from a combination of the discharge detection signal from the external antenna side discharge detection signal selection means and the discharge detection signal from the high voltage device side discharge detection signal selection means;
a discharge occurrence signal holding means having an extension function for integrating the detected partial discharge occurrence signal to extend a temporal signal width, and an accumulation function for integrating and accumulating charge based on the extended partial discharge occurrence signal, and for holding the accumulated charge amount as the partial discharge occurrence signal;
a sampling means for sampling the partial discharge occurrence signal held in the discharge occurrence signal holding means at each predetermined sampling period;
A partial discharge detection device characterized by: The partial discharge detection device according to claim 10,
The partial discharge occurrence detection means determines that a partial discharge has occurred when only the partial discharge occurrence signal is detected.
A partial discharge detection device characterized by: