Insulation wear detection system and insulation wear detection method

Abstract

This insulation deterioration detection system comprises: an antenna that is provided on power receiving and transforming equipment and that detects radio waves; a detection unit that is connected to the antenna and that detects radio wave signals received by the antenna; and a determination unit that detects discharge of the power receiving and transforming equipment on the basis of the relationship between radio wave signals detected by the detection unit and AC power supply of the power receiving and transforming equipment when detecting the radio wave signal. The antenna detects radio waves derived from partial discharge or spark discharge within at least a 180-800 MHz band.

Description

Insulation Degradation Detection System and Insulation Degradation Detection Method

[0001] The present disclosure relates to an insulation degradation detection system and an insulation degradation detection method, and particularly to the detection of partial discharge.

[0002] Due to aging, the insulation performance of the insulator on the surface or inside of the electrical equipment deteriorates. When the insulation performance deteriorates, partial discharge occurs at the deteriorated location. Furthermore, if the deterioration of the insulation performance progresses, insulation breakdown occurs. Insulation breakdown causes serious accidents such as ground fault accidents. Therefore, in the maintenance of electrical equipment, the work of detecting partial discharge is carried out (see Patent Documents 1 and 2).

[0003] Japanese Patent Application Laid-Open No. 2019-211431, Japanese Patent Application Laid-Open No. 2022-78825

[0004] In this regard, in the conventional method, a wide frequency band is used as the measurement range, and it may be difficult to distinguish between the electromagnetic waves of partial discharge and spark discharge and noise at some frequencies. Therefore, there are cases where discharge cannot be detected, and further improvement is required for highly accurate discharge detection.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide an insulation degradation detection system and an insulation degradation detection method capable of highly accurate discharge detection.

[0006] The insulation degradation detection system of the present disclosure is provided for the substation equipment, and includes an antenna for detecting radio waves, a detection unit connected to the antenna for detecting the radio wave signal received by the antenna, and a determination unit for detecting the discharge of the substation equipment based on the relationship between the radio wave signal detected by the detection unit and the AC power supply of the substation equipment when detecting the radio wave signal. The antenna detects radio waves derived from partial discharge or spark discharge in a band within at least 180 MHz to 800 MHz.

[0007] Preferably, the detection unit includes a peak hold circuit that holds the maximum value of the radio wave signal received by the antenna.

[0008] Preferably, the determination unit detects the discharge of the substation based on the radio wave signal detected by the detection unit and the phase relationship of the three-phase AC power supply of the substation at the time of detecting the radio wave signal.

[0009] Preferably, the determination unit detects a discharge of the substation when the detection unit detects a radio wave signal during the rising and falling phases of any phase of the three-phase AC power supply of the substation.

[0010] Preferably, the determination unit detects a discharge from the substation when the detection unit detects a radio wave signal at a period that is a constant multiple of the frequency of the AC power supply of the substation.

[0011] Preferably, the determination unit detects a discharge of the substation when the detection unit detects a radio wave signal two or more times during one cycle of the AC power supply of the substation.

[0012] Preferably, the determination unit detects another discharge of the substation when the detection unit detects two or more radio signals during one cycle of the AC power supply of the substation, and when it detects yet another radio signal at a position where the phase of the AC power supply is shifted by 60 degrees or 120 degrees relative to the detected radio signal.

[0013] Preferably, the radio signal has a specific distribution with respect to the phase of the AC power supply. Preferably, the specific distribution is a normal distribution.

[0014] Preferably, the determination unit detects a discharge in the substation based on whether the signal amplitude of the radio wave signal is greater than or equal to a threshold value and the relationship with the AC power supply of the substation when detecting the radio wave signal.

[0015] Preferably, the determination unit detects a spark discharge in the substation equipment based on whether the signal amplitude of the radio wave signal is greater than or equal to a first threshold and the relationship with the AC power supply of the substation equipment when detecting the radio wave signal, and the determination unit detects a partial discharge in the substation equipment based on whether the signal amplitude of the radio wave signal is greater than or equal to a second threshold and less than the first threshold and the relationship with the AC power supply of the substation equipment when detecting the radio wave signal.

[0016] Preferably, the antenna is positioned facing an insulator within the substation. Preferably, the antenna is positioned facing a busbar and cable that are close to or in contact with an insulator within the substation where partial discharge may occur.

[0017] Preferably, the insulator is epoxy resin or polyester resin. Preferably, the insulator is porcelain or ceramic.

[0018] Preferably, the power receiving and transforming equipment is provided with multiple antennas, further comprising multiple detection units corresponding to each of the multiple antennas, and further comprising a display unit that displays the detection results from the multiple detection units.

[0019] Preferably, the display unit displays a screen showing a comparison of the signal strength distributions of radio wave signals from multiple detection units.

[0020] Preferably, the system further includes a location identification unit that identifies the discharge location of the power receiving and transforming equipment based on the signal strength of radio wave signals from multiple detection units.

[0021] Preferably, the location identification unit identifies the discharge location of the power receiving and transforming equipment based on a comparison of the signal strength distributions of radio wave signals from multiple detection units, and the display unit displays the discharge location of the power receiving and transforming equipment identified by the location identification unit.

[0022] Preferably, the antenna is a monopole antenna including an inverted F antenna or an inverted L antenna, and the counterpoise of the monopole antenna is connected to a conductor that becomes the reference potential of the power receiving and transforming equipment.

[0023] Preferably, the antenna detects radio waves in the frequency band between 180 MHz and 800 MHz, specifically in the band where the difference in signal strength between the discharge-derived radio signal and the noise-derived radio signal when no discharge is occurring is the greatest.

[0024] The insulation degradation detection method of this disclosure comprises the steps of detecting a radio wave signal via an antenna provided for the power receiving and transforming equipment, and detecting a discharge of the power receiving and transforming equipment based on the relationship between the detected radio wave signal and the AC power supply of the power receiving and transforming equipment at the time of detecting the radio wave signal, wherein the detection step detects radio waves originating from a partial discharge or spark discharge in a band of at least 180 MHz to 800 MHz.

[0025] The insulation degradation detection system and insulation degradation detection method disclosed herein enable detection of weak discharges in the early stages of insulation degradation by increasing the detection sensitivity of electromagnetic waves originating from discharge and decreasing the detection sensitivity of electromagnetic waves other than those originating from discharge, and by reducing false detections caused by electromagnetic waves other than those originating from discharge, enabling highly accurate detection of discharges.

[0026] This is a diagram illustrating the power receiving and transforming equipment 1 according to Embodiment 1. This is a diagram illustrating the appearance of the switchboard 10B according to Embodiment 1. This is a diagram illustrating the insulation degradation detection system 100 according to Embodiment 1. This is a diagram showing experimental results illustrating the frequency characteristics of the radio wave signal received by the antenna 20 from a discharge generated in the epoxy resin insulator of the switchboard 10 according to Embodiment 1. This is a diagram showing experimental results illustrating the frequency characteristics of the radio wave signal received by the antenna 20 from a discharge generated in the polyester resin insulator of the switchboard 10 according to Embodiment 1. This is a diagram illustrating the phase relationship between the timing of receiving the radio wave signal and the AC power supply according to Embodiment 1. This is a diagram illustrating the phase relationship between the three-phase AC power supply and the radio wave signal according to Embodiment 1. This is a diagram illustrating the configuration of the detector 40 according to Embodiment 1. This is a diagram illustrating the signal processing of the detector 40 according to Embodiment 1. This is a diagram illustrating the data output from the PLC 80 to the PC 60 according to Embodiment 1. This is a flowchart illustrating the determination processing of the determination unit 62 according to Embodiment 1. This is a diagram illustrating a specific example of the detection time of a signal with high discharge intensity extracted by the determination unit 62 according to Embodiment 1. This is a diagram illustrating the display of the display unit 80 of the power receiving and transforming equipment 1 according to Embodiment 2. This is a diagram illustrating the display of the display unit 80 of the power receiving and transforming equipment 1 according to a modified example of Embodiment 2. This is a diagram illustrating another display of the display unit 80 of the power receiving and transforming equipment 1 according to a modified example of Embodiment 2. This is a diagram illustrating yet another display of the display unit 80 of the power receiving and transforming equipment 1 according to a modified example of Embodiment 2. insulation degradation detection system 110 according to Embodiment 3.

[0027] This embodiment will be described in detail with reference to the drawings. Note that identical or corresponding parts in the drawings are denoted by the same reference numerals, and their descriptions will not be repeated.

[0028] Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) Figure 1 is a diagram illustrating a power receiving and transforming equipment 1 according to Embodiment 1. Referring to Figure 1, the power receiving and transforming equipment 1 is provided with a plurality of distribution boards 10A to 10G (hereinafter collectively referred to as distribution boards 10). Various electrical devices are provided in each distribution board 10 according to its purpose. As an example, a wiring diagram of the power receiving and transforming equipment 1 is shown, illustrating a case in which various electrical devices are provided in relation to each distribution board 10.

[0029] Specifically, the diagram shows that the switchboard 10A is equipped with a surge arrester (SAR), a circuit breaker (VCB), a current transformer (CT), and an electric voltage transformer (EVT). Similarly, various electrical devices are installed in each of the switchboards 10B to 10G.

[0030] Figure 2 illustrates the external appearance of a switchboard 10B according to Embodiment 1. Referring to Figure 2(A), a case is shown where circuit breakers (VCBs) are provided above and below the busbar. In this example, it is also possible to provide additional circuit breakers (VCBs) to a single switchboard. For example, circuit breakers (VCBs) may be placed on the upper, middle, and lower sections, respectively.

[0031] Furthermore, this example shows the case where the antenna 20 is installed inside the door of the distribution panel 10B. By installing it inside the door, it is possible to increase the discharge detection sensitivity compared to when it is installed outside the door of the distribution panel 10B. Also, this example shows the case where the detector 40 is installed outside the distribution panel 10B, but the detector 40 may be installed inside the distribution panel 10B. In addition, an inverted F-type antenna or an inverted L-type antenna may be used for the antenna 20. As an example, the antenna 20 is installed inside the distribution panel 10B, and the antenna and detector are connected by a coaxial cable via a gap in the distribution panel, a through hole, or a dedicated coaxial connector. For maintenance and upkeep, it is desirable to measure the smallest possible discharge, so it is preferable to place the antenna 20 inside the distribution panel. However, if radio waves caused by the discharge leak outside the distribution panel, or if there is no space to install the antenna 20 inside the power receiving and transforming equipment, the antenna 20 may be placed outside the distribution panel.

[0032] Referring to Figure 2(B), a side view of the distribution panel 10B is shown. The antenna 20 is positioned opposite the insulator inside the distribution panel 10B. For example, it is positioned opposite the conductor support insulator 150 provided for the busbar. The conductor support insulator 150 is made of epoxy resin, polyester resin, porcelain, or ceramic. Epoxy resin or polyester resin is also used for insulators such as CT / PT cases and VCB cases. Porcelain and ceramic are sometimes used for bushings of transformers and power factor correction capacitors. Epoxy resin, polyester resin, porcelain, or ceramic may experience partial discharge due to surface contamination.

[0033] Signals originating from discharges generated in the insulators inside the power distribution panel are propagated to the busbars via conductors connected to the insulators. Therefore, by positioning the antenna 20 not only in front of the insulators that are expected to deteriorate, but also opposite the conductors that are close to or in contact with the insulators, i.e., the busbars and cables, it is possible to efficiently detect radio waves associated with discharges. This arrangement makes it possible to efficiently detect radio waves associated with discharges between the equipment connected to the insulators inside the power distribution panel. Furthermore, using a monopole antenna such as an inverted F-type antenna or an inverted L-type antenna for the antenna 20 is a desirable embodiment because it allows the dimensions of the antenna 20 to be reduced and it can be placed inside the device. Such antennas have a counterpoise, that is, a ground for the antenna (= a conductor that serves as the reference potential). However, in order to make the antenna smaller so that it can be placed inside the device, the counterpoise needs to be reduced, which can degrade the antenna's receiving performance. Therefore, connecting the counterpoise directly to the equipment's conductor or via a lead wire is desirable because it increases the counterpoise and stabilizes the reference potential for the antenna element of the monopole antenna, thereby improving the antenna's receiving sensitivity. Furthermore, connecting the counterpoise to the conductor of the equipment has the effect of preventing the counterpoise from becoming charged in strong electric and magnetic field environments.

[0034] Figure 3 is a diagram illustrating an insulation degradation detection system 100 according to Embodiment 1. Referring to Figure 3, the insulation degradation detection system 100 is provided corresponding to each of the multiple distribution boards 10A to 10G of the power receiving and transforming equipment 1, and includes an antenna 20 for detecting radio waves, a detector 40 connected to the antenna 20 via a coaxial cable 30, a PLC (Programmable Logic Controller) 80, a PC (Personal Computer) 60, and a display unit 80. In this example, the case where it is provided in distribution boards 10A and 10B is shown as an example. It may also be provided corresponding to one distribution board. The detector 40 detects the radio wave signal received by the antenna 20. The PLC 80 is connected to an AC power source correlated with the power receiving and transforming equipment 1, and acquires information on the phase relationship of the AC power source when detecting the radio wave signal detected by the detector 40, and outputs it to the PC 60. The PC 60 detects the discharge of the power receiving and transforming equipment 1 based on the information from the PLC 82. Specifically, the PC 60 includes a determination unit 62 and a screen generation unit 64.

[0035] The determination unit 62 detects the discharge of the power receiving and transforming equipment 1 based on the relationship between the radio wave signal detected by the detector 40 and the AC power supply of the power receiving and transforming equipment 1 at the time the radio wave signal is detected. Specifically, the determination unit 62 detects the discharge of the power receiving and transforming equipment 1 based on the phase relationship of the three-phase AC power supply of the power receiving and transforming equipment 1 at the time the radio wave signal is detected by the detector 40. The determination unit 62 detects the discharge of the power receiving and transforming equipment 1 when the detector 40 detects a radio wave signal at the rising and falling ends of any phase of the three-phase AC power supply of the power receiving and transforming equipment 1. The screen generation unit 64 generates a screen to be displayed on the display unit 80 based on the detection results of the determination unit 62.

[0036] The PC 60 has at least one CPU (Central Processing Unit) and memory, and various functions are realized by the CPU executing programs stored in the memory. Specifically, it realizes the functions of the determination unit 62 and the screen generation unit 64. In this example, a configuration in which the PLC 80 and PC 60 are provided separately is described, but they may also be realized in a single device. It is also possible to include the detector 40 in a single device. Furthermore, the functions of the PLC 80 and PC 60 may be realized using an external server via a network. In addition, in this example, a configuration in which the antenna 20 and the detector 40 are connected using a coaxial cable 30 is described, but for example, they may be connected wirelessly instead of wired.

[0037] Figure 4 is a diagram illustrating the experimental results explaining the frequency characteristics of a radio wave signal received by antenna 20 from a discharge occurring in the epoxy resin insulator of a power distribution panel 10 according to Embodiment 1. Referring to Figure 4(A), this example shows the relationship between the signal strength and frequency characteristics of the radio wave signal when a partial discharge occurs in the epoxy resin insulator. Here, the insulator of the power distribution panel 10 includes conductor support insulators, CT / PT cases, VCB cases, etc., but the frequency characteristics when epoxy is used are shown. Noise refers to dark noise when no discharge is occurring, and includes radio waves from equipment inside the device, external noise entering as radio waves through gaps in the device, or radio waves generated by current radiated inside the device from cables propagating from outside to inside the device. As an example, it is shown that when a partial discharge occurs, a signal strength of the radio wave signal is obtained in the frequency band of 180 MHz to 800 MHz compared to the dark noise. For example, it is possible to determine a partial discharge when a radio wave signal exceeding a predetermined threshold Vth1 (-30 dB) is detected in that frequency band. The threshold can be freely determined depending on the environment, frequency, and antenna used. However, reducing the difference with the background noise increases false detections, while increasing the difference increases the likelihood of undetected discharges. Therefore, in Figure 4(A), the threshold is set to -30 dBm, which is approximately 10 dB higher than the background noise. In particular, in Figure 4(A), the difference between the radio wave component of background noise and the radio wave component due to partial discharge is significant in the 200 MHz to 400 MHz frequency band. Therefore, within the 180 MHz to 800 MHz frequency band, it may be possible to determine partial discharge using frequency bands where the intensity of the difference between the radio wave component of background noise and the radio wave component due to partial discharge is greater than or equal to a predetermined value. Doing so can reduce the possibility of false detections.

[0038] Referring to Figure 4(B), the relationship between the signal strength and frequency characteristics of a radio wave signal when a spark discharge occurs in the epoxy resin insulator of the distribution panel 10 is shown. Here, the frequency characteristics are shown when epoxy resin is used as the insulator of the distribution panel 10. As an example, it is shown that when a spark discharge occurs, a signal strength of a radio wave signal higher than that of noise can be obtained in the frequency band of 180 MHz to 800 MHz. For example, it is possible to determine a spark discharge when a radio wave signal exceeding a predetermined threshold Vth2 (-20 dBm) is detected in that frequency band.

[0039] Note that the threshold value is just an example and can be changed as appropriate depending on the type and condition of the insulating material. Furthermore, it may be used to determine between partial discharge and spark discharge based on the difference in intensity.

[0040] Figure 5 is a diagram illustrating the experimental results explaining the frequency characteristics of a radio wave signal received by antenna 20 from a discharge occurring in the polyester resin insulator of a power distribution panel 10 according to Embodiment 1. Referring to Figure 5(A), this example shows the relationship between the signal strength and frequency characteristics of the radio wave signal when a partial discharge occurs in the polyester resin insulator. As an example, it is shown that when a partial discharge occurs, a higher signal strength of the radio wave signal can be obtained compared to the background noise in the frequency band of 180 MHz to 800 MHz. For example, it is possible to determine a partial discharge when a radio wave signal exceeding a predetermined threshold Vth1 (-30 dBm) is detected in that frequency band. The threshold can be freely determined according to the environment, frequency, and antenna used, but if the difference with the background noise is small, false detections increase, and if the difference is large, the number of undetected discharges increases. Therefore, in Figure 5(A), it is set to -30 dBm, which is about 10 dB larger than the background noise.

[0041] Referring to FIG. 5(B), the relationship between the signal intensity and the frequency characteristics of the radio wave signal when spark discharge occurs in the polyester resin insulator of the switchboard 10 is shown here. As an example, it is shown that when spark discharge occurs, a high signal intensity of the radio wave signal can be obtained compared with the noise in the frequency band of 180 MHz to 800 MHz. For example, it is possible to determine spark discharge when a radio wave signal exceeding a predetermined threshold value Vth2 (-20 dBm) is detected in the frequency band.

[0042] Note that the threshold value is an example and can be appropriately changed according to the type and situation of the insulator material. Furthermore, it may be used to determine partial discharge and spark discharge based on the difference in intensity.

[0043] On the other hand, since the noise state also changes depending on the environment and state of the switchboard 10, there is a possibility that a radio wave signal with a high signal intensity may be detected instantaneously.

[0044] Therefore, in this example, in order to avoid this situation, the discharge generated in the power receiving and transforming equipment 1 is detected based on the phase relationship of the AC power supply of the power receiving and transforming equipment 1 when detecting the radio wave signal.

[0045] FIG. 6 is a diagram for explaining the timing of receiving the radio wave signal according to the first embodiment and the phase relationship of the AC power supply. Referring to FIG. 6, in this example, it is shown that a radio wave signal with a high signal intensity is received at positions where the phase is shifted by 60° and 240° with reference to the R phase of the RST phases of the three-phase AC power supply. That is, the experimental results of detecting discharge at 60° when the T phase rises and at 240° which is the rising time with a 180° phase delay from the falling time when the R phase of the three-phase AC power supply is used as a reference are shown.

[0046] FIG. 7 is a diagram for explaining the phase relationship between a three-phase AC power supply and a radio wave signal according to Embodiment 1. Referring to FIG. 7, a case where the horizontal axis is the time axis and the vertical axis is the amplitude dBm is shown. The AC power supply waveforms of the RST phases of the three-phase AC power supply according to Embodiment 1 and the discharge timing will be described. As shown in FIG. 7, the R phase, S phase, and T phase are shown, and a case where the phases are shifted by 120 degrees each is shown. In this example, a case where discharge occurs near the zero cross when the T phase is falling and rising with respect to the R phase as a reference is shown.

[0047] In this example, after a radio wave signal with a high signal intensity is first detected, the occurrence of discharge is determined based on whether a radio wave signal with a high signal intensity is detected again at a position where the phase is shifted by 180°. When a radio wave signal with a high signal intensity is detected twice at a timing where the phase is shifted by 180° correlated with the AC power supply waveform, it is determined as a discharge. In this example, discharge is detected in the T phase, but it is also possible to make the same determination in the R phase and S phase.

[0048] When the AC power supply is set to 60 Hz in this way, two discharges occur, one at the rising edge from the zero cross and the other at the falling edge from the zero cross within one cycle. Therefore, the discharge detection signal has a frequency characteristic of 120 Hz, which is twice the frequency of the AC power supply of 60 Hz. Utilizing this characteristic, when the frequency characteristic of the discharge detection signal is twice the frequency of the AC power supply, it is determined as a discharge. Furthermore, in order to reduce false detection, it may be determined as a discharge when a discharge detection signal with a frequency twice that of the AC power supply is repeatedly detected.

[0049] Also, due to the characteristics of the discharge, the amplitude due to the discharge may fluctuate when the position of the discharge is shifted, or the discharge location may be different between the rising and falling edges from the zero cross. Therefore, it may be determined that a radio wave signal that appears with a period twice that of the AC power supply and has different amplitudes for each is a radio wave signal originating from the discharge, or a radio wave signal with fluctuations in amplitude and waveform in repeated measurements may be determined as a radio wave signal originating from the discharge.

[0050] By combining one or more of these characteristics, false detections can be prevented. This is because antennas can sometimes misinterpret radio signals such as marine radio, airport radio, TV broadcasts, and mobile phone signals as background noise. However, these signals are unrelated to the AC power cycle and therefore do not occur at constant multiples of the cycle (e.g., 120 Hz). Even if a 120 Hz signal is misinterpreted, repeated measurements can eliminate the element of chance.

[0051] Furthermore, radio signals generated from electronic devices inside a device are highly likely to be synchronized with the AC power supply, which is one of the causes of false detection. However, typical electronic devices operate at a 60 Hz cycle, and rarely at a 120 Hz cycle, so false detection can be reduced by measuring at twice the cycle. Also, even if there is an electronic device inside the device that generates radio signals at a 120 Hz cycle, the electronic device usually operates in a stable, repetitive state, so the generated radio signals do not change much in amplitude or frequency.

[0052] On the other hand, radio waves originating from electrical discharges are likely to have different amplitudes and waveforms with each repeated measurement. Therefore, it may be possible to distinguish between radio waves from electronic devices and those originating from electrical discharges based on whether the radio wave is stable or has large fluctuating components. Furthermore, while radio waves from typical electronic devices are generated intermittently, radio waves originating from electrical discharges are intermittent electromagnetic waves that occur at a frequency of once every few minutes, or in some cases, once every few days. Therefore, information on the frequency of radio wave detection may be used to distinguish between radio waves from electronic devices and those originating from electrical discharges.

[0053] Furthermore, as shown in Figure 6, when detecting radio wave signals originating from two or more discharges and plotting the measurement results as points with phase on the horizontal axis and radio wave intensity on the vertical axis, it may be determined that a radio wave signal originating from a partial discharge has a specific distribution. For example, a specific distribution refers to a probability distribution that includes a normal distribution (Gaussian distribution). In addition, to obtain an accurate distribution, it may be necessary to use the results of 10 or more measurements, or to increase the number of measurements taken when a discharge occurs.

[0054] The above explanation describes a case where, in order to obtain the period of the AC power supply and the period of discharge, a sensor is placed on the AC power supply to detect the AC current, and an antenna is placed near the power supply to detect the radio wave signal originating from the discharge, and the discharge is determined by combining the two signals.

[0055] In this regard, in order to synchronize the rising and falling timings of the AC power supply from zero crossing with the discharge timing, the electrical length from the sensor attached to the AC power supply to the detector and the electrical length from the power supply through the antenna to the detector may be measured, and the two signals may be synchronized by correcting the electrical length in post-processing. The electrical length correction may be performed taking into account differences such as the position of the antenna and the length of the cable for each measurement target.

[0056] Furthermore, although Figure 7 shows a discharge at zero crossing, the phase of the discharge and the AC power supply do not necessarily need to be synchronized; a discharge can be determined when a 120 Hz antenna received a signal. Since the frequency of the AC power supply that operates the equipment is known, by determining that the radio signal generated at twice the frequency of the AC power supply is a radio signal originating from the discharge, not only are sensors and detectors for the AC power supply unnecessary, but electrical length correction is also unnecessary. As a result, detecting a radio signal with twice the frequency of the AC power supply makes it possible to detect discharges with fewer false detections, regardless of the equipment being measured, simply by attaching an antenna to the equipment.

[0057] Furthermore, in cases where discharge occurs simultaneously in two or more locations, such as when discharge occurs at the same timing in both the T-phase and R-phase, the discharge detection signal has frequency characteristics of 240Hz and 360Hz, which are constant multiples of 120Hz. Therefore, by detecting these, it is possible to handle multiple power sources. If the horizontal axis is phase, the 120Hz signal is a signal with a phase shift of 180 degrees, and the 240Hz signal appears at a position where the phase is shifted by 60 degrees or 120 degrees relative to this signal. Also, the 360Hz signal appears at a position where the phase is shifted by 60 degrees and 120 degrees relative to the 120Hz signal.

[0058] However, while discharges around adjacent T, R, and S phases can be considered to generate radio waves at a constant multiple of 120 Hz, discharges from insulators at different locations will not strictly be a constant multiple due to differences in propagation distance between the power source and the antenna. Therefore, if two signals with a period of 120 Hz are present, it may be determined that there are two power sources, or the number of power sources may be determined by the difference in amplitude and frequency, as the amplitude and frequency of the discharge differ depending on the degree of deterioration of the insulator.

[0059] Furthermore, the amplitude and frequency of the discharge during the rising edge from zero crossing are not necessarily the same as those of the discharge during the falling edge from zero crossing. In particular, radio signals originating from partial discharges are weak and, due to the measurement limits of the measuring instrument, it may be possible to detect only the discharge during the falling edge from zero crossing, for example. Therefore, it may be possible to detect the signal as a partial discharge using a period equal to the frequency of the AC power supply, for example, 60 Hz. In this case, the reliability may be lower compared to, for example, detection at twice the frequency, 120 Hz, so it may be possible to improve reliability by increasing the number of detections, or by combining this with discharge-specific information that is not present in surrounding electronic equipment or external noise sources, such as a change of a few percent to several tens of percent in amplitude with each measurement, or a change of about 0.01% to 1% in peak frequency (maximum value in the set frequency band), in order to determine that it is a radio signal originating from a discharge.

[0060] Although amplitude and frequency were explained as distinct concepts, if amplitudes can be obtained at multiple frequencies, they may be considered as frequency characteristics.

[0061] Figure 8 is a diagram illustrating the configuration of a detector 40 according to Embodiment 1. Referring to Figure 8, the detector 40 includes a bandpass filter 41, an amplification and absolute value conversion circuit 42, a peak hold circuit 43, an A / D conversion circuit 44, a zero-value invalidation processing circuit 45, a D / A conversion circuit 46, and a reset signal generator 47.

[0062] The detector 40 receives a signal SA, which is a discharge waveform (input), via an antenna 20 connected to a coaxial cable 30.

[0063] The bandpass filter 41 is a circuit that passes a signal SA in a predetermined frequency band that is input to the device, and removes signals in other bands. In this example, the predetermined frequency band is set to pass signals from 180 MHz to 800 MHz, and removes signals in other bands. This makes it possible to receive only radio signals caused by electrical discharges.

[0064] The amplification and absolute value conversion circuit 42 amplifies and absolute values ​​the signal to adjust the waveform so that the characteristics of the radio wave signal can be easily detected. The adjusted signal SB is input to the peak hold circuit 43.

[0065] The reset signal generator 47 generates a reset signal at a predetermined interval. In this example, a reset signal is generated every 30 μs. Specifically, the reset signal generator 47 outputs a reset signal with a reset period of 1 μs after 29 μs.

[0066] The peak hold circuit 43 resets according to the reset signal and then holds the peak value of the adjusted signal SB, which is an analog signal.

[0067] The A / D conversion circuit 44 converts the analog signal from the peak hold circuit 43 into a digital signal and outputs it to the zero-value invalidation processing circuit 45.

[0068] The zero-value invalidation processing circuit 45 holds the maximum data output from the A / D conversion circuit 44 for a predetermined period in accordance with the reset signal. Specifically, the predetermined period is 30 μs.

[0069] The D / A conversion circuit 46 outputs a signal SE, which is an analog signal obtained by converting the digital signal from the zero-value invalidation processing circuit 45, to the external PLC 80.

[0070] Figure 9 is a diagram illustrating the signal processing of the detector 40 according to Embodiment 1. Referring to Figure 9, at time T0, a radio wave signal of the discharge waveform is input to the detector 40 via the antenna 20. The amplification and absolute value conversion circuit 42 adjusts the waveform of the radio wave signal of the discharge waveform. The peak hold circuit 43 holds the peak value of the radio wave signal. The A / D conversion circuit 44 converts the radio wave signal into a digital value and outputs it to the zero-value invalidation processing circuit 45. The zero-value invalidation processing circuit 45 holds the peak value held by the peak hold circuit 43 via the A / D conversion circuit 44 for a predetermined period of time according to the input of a reset signal. The D / A conversion circuit 46 outputs the peak value held by the peak hold circuit 43 as an analog signal.

[0071] Similarly, the same signal processing is performed at times T1, T2, T3, etc. The zero-value invalidation processing circuit 45 can hold the peak value held by the peak hold circuit 43 via the A / D conversion circuit 44 for a predetermined period (30 μs). Therefore, for example, if only the peak hold circuit 43 is provided in the detector 40, there is a possibility of missing the discharge waveform when outputting data to the PLC 80 during the period when the data is reset by the reset signal. However, since the peak value is held and output for a predetermined period regardless of the reset period, it is possible to reliably output data to the PLC and detect the discharge.

[0072] Figure 10 is a diagram illustrating the data output from the PLC 80 to the PC 60 according to Embodiment 1. Referring to Figure 10, the PLC 80 receives data (discharge intensity data) from the detector 40 according to a predetermined period and outputs it to the PC 60 in association with the phase information (time) of the AC power supply at the time of receipt.

[0073] In this example, a case is shown where data from the detector 40 is received in a time series and associated with phase information (time). Specifically, the PLC 80 receives data from the detector 40 at predetermined intervals of 30 μs. For example, a case is shown where the R phase of the AC power supply is used as the reference. As an example, a case is shown where, at time 0, the voltage of the R phase AC power supply is 0, and a signal indicating the discharge intensity is received from the detector 40 at 30 μs intervals.

[0074] For example, data numbers "1" through "8" show a relationship between time (ms) and discharge intensity. It is possible to calculate the phase of the AC power supply based on this time.

[0075] Subsequently, the PLC 80 outputs the discharge intensity detected by the detector 40 to the PC 60, associating it with the phase information (time).

[0076] Figure 11 is a flowchart illustrating the determination process of the determination unit 62 according to Embodiment 1. Referring to Figure 11, the determination unit 62 acquires data (step S2). For example, in the format shown in Figure 10, the determination unit 62 acquires data of the phase information (time) of the AC power supply associated with the discharge intensity detected by the detector 40 from the PLC 80. Next, the determination unit 62 extracts the detection time of signals with a discharge intensity of a threshold or higher from the acquired data (step S4). For example, as explained in Figure 4, it determines whether there is a signal with a discharge intensity of Vth1 or higher and extracts the phase information (time) of the signal with high discharge intensity.

[0077] Figure 12 illustrates a specific example of the detection time of a signal with high discharge intensity extracted by the determination unit 62 according to Embodiment 1. Referring to Figure 12, an example is shown where a discharge occurs in the T phase of an AC power supply. Specifically, it shows cases where a signal with discharge intensity above a threshold is detected at 60° (time "0.002777"), 240° (time "0.011111"), 420° (time "0.019444"), 600° (time "0.027777"), ... with respect to 0° of the R phase of the AC power supply.

[0078] Referring again to Figure 11, the determination unit 62 determines whether or not there is a signal with a discharge intensity above the threshold at a position shifted by 180° in phase (step S8). For example, if the AC power supply is 60 Hz, the position shifted by 180° in phase is 0.008333 s after elapsed. By comparing the time at which the first signal with a discharge intensity above the threshold is detected with the time at which the next signal with a discharge intensity above the threshold is detected, it is possible to determine whether or not the position is shifted by 180° in phase (time "0.008333").

[0079] In step S8, if the determination unit 62 determines that there is no signal with a discharge intensity above the threshold at a position shifted by 180° in phase (NO in step S8), it determines that there is no discharge and terminates the process (end).

[0080] On the other hand, in step S8, if the determination unit 62 determines that there is a signal with a discharge intensity of 180° or more at a position shifted in phase (YES in step S8), it detects the discharge (step S10). Then, it terminates the process (end).

[0081] In this example, we will describe the case in step S8 where it is determined whether there is a signal with a discharge intensity above the threshold at a position shifted by 180° in phase. However, it is not necessary for the phase to be shifted by exactly 180°; if there is a signal with a discharge intensity above the threshold at a position near that point, it may be detected as a discharge.

[0082] Furthermore, while the flowchart in Figure 11 describes a case where a discharge is detected when a signal with a discharge intensity above a threshold occurs once consecutively at a position shifted by 180°, the system may also determine that a discharge has been detected when multiple consecutive occurrences occur. This enables highly accurate discharge detection.

[0083] Furthermore, the determination unit 62 can also detect discharge according to a method other than the flow described above.

[0084] Specifically, the determination unit 62 can detect discharge based on the detection time data for a predetermined period extracted in Figure 12.

[0085] The determination unit 62 may analyze the frequency characteristics as the data characteristics of the detection time in Figure 12 and determine that a discharge has been detected if it is 120 Hz. In other words, the determination unit 62 detects a discharge in the power receiving and transforming equipment when it detects a radio wave signal with a discharge intensity of a threshold or higher at a period that is a constant multiple of the frequency of the AC power supply (for example, 60 Hz).

[0086] Furthermore, the determination unit 62 may determine that a discharge has occurred in the substation 1 if it detects a radio wave signal with a discharge intensity equal to or greater than a threshold value during the rising and falling times of any phase of the three-phase AC power supply of the substation 1.

[0087] Furthermore, as explained in Figure 6, the determination unit 62 may detect radio wave signals originating from two or more discharges, and when the measurement results are plotted as points with phase on the horizontal axis and radio wave intensity on the vertical axis, it may determine that the distribution of the measurement results has a specific distribution as a radio wave signal originating from a partial discharge.

[0088] Furthermore, as explained in Figure 7, the determination unit 62 can also detect which of the R, S, or T phases the discharge occurred in. The determination unit 62 detects two or more radio signals with a discharge intensity above the threshold during one cycle of the AC power supply, and detects another radio signal with a discharge intensity above the threshold at a position where the AC power supply is shifted 60 or 120 degrees in phase with respect to the detected radio signals, as another discharge in the power receiving and transforming equipment.

[0089] In this example, we have described the case of determining whether or not the signal has a discharge intensity of threshold Vth1 or higher. However, it is also possible to detect whether or not a spark discharge has occurred by determining whether or not the signal has a discharge intensity of threshold Vth2 or higher.

[0090] (Embodiment 2) Embodiment 2 describes a case in which information regarding the location where a discharge occurred is displayed to the user.

[0091] Specifically, the screen generation unit 64 of the PC 60 displays the level of discharge intensity of the power receiving and transforming equipment 1 on the display unit 80 based on the signal strength of the radio wave signal from the detector 40.

[0092] Figure 13 is a diagram illustrating the display of the display unit 80 of the power receiving and transforming equipment 1 according to Embodiment 2. Referring to Figure 13(A), this example shows a case in which antennas 20A to 20G are provided corresponding to each of the distribution boards 10A to 10G.

[0093] The detector 40 is connected to each of the antennas 20A to 20G and detects the radio wave signals received by each of the antennas 20A to 20G. The PLC 80 is connected to an AC power supply that is correlated with the power receiving and transforming equipment 1 and to multiple antennas. The PLC 80 acquires information on the phase relationship between the power supply and the AC power supply when detecting the radio wave signals detected by the detector 40 and outputs it to the PC 60. The PC 60 detects the discharge of the power receiving and transforming equipment 1 based on the information from the PLC 82 according to the method described in Embodiment 1 above.

[0094] Referring to Figure 13(B), when the determination unit 62 detects a discharge, the screen generation unit 64 displays a graph on the display unit 80 corresponding to the signal strength of the radio wave signals detected by the multiple antennas 20A to 20G.

[0095] As an example, the screen generation unit 64 displays a graph on the display unit 80 that shows the highest discharge intensity corresponding to the position of the antenna 20D, which has the highest discharge intensity among the multiple antennas 20A to 20G.

[0096] Based on the signal strength distribution comparison displayed on the display unit 80, the user can identify the location corresponding to the antenna 20 with the highest discharge intensity as the discharge point.

[0097] This method not only detects the occurrence of a discharge, but also allows the user to confirm the location of the discharge.

[0098] Figure 14 is a diagram illustrating the display of the display unit 80 of the power receiving and transforming equipment 1 according to a modified example of Embodiment 2. Referring to Figure 14(A), this example shows a case in which multiple antennas 20P to 20R at different positions are provided for one distribution board 10.

[0099] The detector 40 is connected to each of the antennas 20P to 20R and detects the radio wave signals received by each of the antennas 20P to 20R. The PLC 80 is connected to an AC power source correlated with the power receiving and transforming equipment 1 and acquires information on the phase relationship between the power source and the AC power source when detecting the radio wave signals detected by the detector 40, and outputs it to the PC 60. The PC 60 detects the discharge of the power receiving and transforming equipment 1 based on the information from the PLC 82 in accordance with the method described in Embodiment 1 above.

[0100] Referring to Figure 14(B), when the determination unit 62 detects a discharge, the screen generation unit 64 displays a graph on the display unit 80 corresponding to the signal strength of the radio wave signals detected by the multiple antennas 20P to 20R.

[0101] As an example, the screen generation unit 64 displays a graph on the display unit 80 that shows the highest discharge intensity corresponding to the position of the antenna 20P, which has the highest discharge intensity among the multiple antennas 20P to 20R.

[0102] The user can identify the location corresponding to the antenna 20 with the highest discharge intensity as the discharge point based on the signal intensity distribution comparison displayed on the display unit 80. In this example, the user can identify the location corresponding to the antenna 20P with the highest discharge intensity among the multiple antennas 20P to 20R as the discharge point.

[0103] Figure 15 illustrates another display of the display unit 80 of the power receiving and transforming equipment 1 according to a modified example of Embodiment 2. Referring to Figure 15(A), this example shows a case in which multiple antennas 20P to 20R at different positions are provided for one distribution board 10.

[0104] The detector 40 is connected to each of the antennas 20P to 20R and detects the radio wave signals received by each of the antennas 20P to 20R. The PLC 80 is connected to an AC power source correlated with the power receiving and transforming equipment 1 and acquires information on the phase relationship between the power source and the AC power source when detecting the radio wave signals detected by the detector 40, and outputs it to the PC 60. The PC 60 detects the discharge of the power receiving and transforming equipment 1 based on the information from the PLC 82 in accordance with the method described in Embodiment 1 above.

[0105] Referring to Figure 15(B), when the determination unit 62 detects a discharge, the screen generation unit 64 displays a graph on the display unit 80 corresponding to the signal strength of the radio wave signals detected by the multiple antennas 20P to 20R.

[0106] As an example, the screen generation unit 64 displays a graph on the display unit 80 that shows the highest discharge intensity corresponding to the position of the antenna 20Q, which has the highest discharge intensity among the multiple antennas 20P to 20R.

[0107] The user can identify the location corresponding to the antenna 20 with the highest discharge intensity as the discharge point based on the signal intensity distribution comparison displayed on the display unit 80. In this example, the user can identify the location corresponding to the antenna 20Q with the highest discharge intensity among the multiple antennas 20P to 20R as the discharge point.

[0108] Figure 16 illustrates yet another display of the display unit 80 of the power receiving and transforming equipment 1 according to a modified example of Embodiment 2. Referring to Figure 16(A), this example shows a case in which multiple antennas 20P to 20R at different positions are provided for one distribution board 10.

[0109] The detector 40 is connected to each of the antennas 20P to 20R and detects the radio wave signals received by each of the antennas 20P to 20R. The PLC 80 is connected to an AC power source correlated with the power receiving and transforming equipment 1 and acquires information on the phase relationship between the power source and the AC power source when detecting the radio wave signals detected by the detector 40, and outputs it to the PC 60. The PC 60 detects the discharge of the power receiving and transforming equipment 1 based on the information from the PLC 82 in accordance with the method described in Embodiment 1 above.

[0110] Referring to Figure 16(B), when the determination unit 62 detects a discharge, the screen generation unit 64 displays a graph on the display unit 80 corresponding to the signal strength of the radio wave signals detected by the multiple antennas 20P to 20R.

[0111] As an example, the screen generation unit 64 displays a graph on the display unit 80 that shows the highest discharge intensity corresponding to the position of the antenna 20R with the highest discharge intensity among the multiple antennas 20P to 20R.

[0112] The user can identify the location corresponding to the antenna 20 with the highest discharge intensity as the discharge point based on the signal intensity distribution comparison displayed on the display unit 80. In this example, the user can identify the location corresponding to the antenna 20R with the highest discharge intensity among the multiple antennas 20P to 20R as the discharge point.

[0113] This method allows for the detection of electrical discharges occurring within a single distribution panel 10 by installing multiple antennas within the panel, and also enables the user to pinpoint the location of the discharge.

[0114] Figure 17 is a diagram illustrating the display of the display unit 80 of the power receiving and transforming equipment 1 according to a modified example 2 of Embodiment 2. Referring to Figure 17(A), this example shows a case in which multiple antennas 20P and 20R at different positions are provided for one distribution board 10.

[0115] Compared to the configuration in Figure 14, the difference is that antenna 20Q has been removed, leaving only antennas 20P and 20R.

[0116] Referring to Figure 17(B), when the determination unit 62 detects a discharge, the screen generation unit 64 displays a graph on the display unit 80 corresponding to the signal strength of the radio wave signals detected by the multiple antennas 20P and 20R.

[0117] As an example, the screen generation unit 64 displays a graph on the display unit 80 corresponding to the position of the antenna with the highest discharge intensity among the multiple antennas 20P and 20R.

[0118] The user can identify the location corresponding to the antenna 20 with the highest discharge intensity based on the signal intensity distribution comparison displayed on the display unit 80. In this example, the user can identify the location corresponding to the antenna 20P with the highest discharge intensity among the multiple antennas 20P and 20R as the discharge location.

[0119] Figure 18 illustrates another display of the display unit 80 of the power receiving and transforming equipment 1 according to a modified example 2 of Embodiment 2. Referring to Figure 18(A), this example shows a case in which multiple antennas 20P and 20R at different positions are provided for one distribution board 10.

[0120] Referring to Figure 18(B), when the determination unit 62 detects a discharge, the screen generation unit 64 displays a graph on the display unit 80 corresponding to the signal strength of the radio wave signals detected by the multiple antennas 20P and 20R.

[0121] As an example, the screen generation unit 64 displays a graph on the display unit 80 corresponding to the position of the antenna with the highest discharge intensity among the multiple antennas 20P and 20R.

[0122] The user can identify the location corresponding to the antenna 20 with the highest discharge intensity based on the signal intensity distribution comparison displayed on the display unit 80. In this example, the discharge intensity of antennas 20P and 20R is shown to be at the same level.

[0123] In this case, the user can identify the discharge point as the location corresponding to the area between antennas 20P and 20R.

[0124] Figure 19 is a diagram illustrating yet another display of the display unit 80 of the power receiving and transforming equipment 1 according to a modified example 2 of Embodiment 2. Referring to Figure 19(A), this example shows a case in which multiple antennas 20P and 20R are provided at different positions for one switchboard 10.

[0125] Referring to Figure 19(B), when the determination unit 62 detects a discharge, the screen generation unit 64 displays a graph on the display unit 80 corresponding to the signal strength of the radio wave signals detected by the multiple antennas 20P and 20R.

[0126] As an example, the screen generation unit 64 displays a graph on the display unit 80 corresponding to the position of the antenna with the highest discharge intensity among the multiple antennas 20P and 20R.

[0127] The user can identify the location corresponding to the antenna 20 with the highest discharge intensity based on the signal intensity distribution comparison displayed on the display unit 80. In this example, the user can identify the location corresponding to the antenna 20R with the highest discharge intensity among the multiple antennas 20P and 20R as the discharge location.

[0128] For example, if radio waves are considered in the far field, the discharge intensity is inversely proportional to the distance. Therefore, the received intensity of antennas 20P and 20R can be converted into a ratio of distances, and the source of the discharge can be found from this information. Also, depending on the frequency of the object being measured and the dimensions of the distribution board, it may be in the near field (generally, anything less than one wavelength can be considered the near field, and at 300 MHz, one wavelength is 1 m). In this case, the discharge intensity is inversely proportional to the square or cube of the distance, so it is desirable to consider the characteristics of electromagnetic waves in these near fields when converting to a ratio of distances.

[0129] This method makes it possible to identify the location of a discharge by comparing the discharge intensities detected by multiple antennas, even when the number of antennas is reduced.

[0130] In this example, we have described how to identify the location of a discharge point when the number of antennas is reduced for a single distribution panel 10. However, this method can also be applied to configurations such as that shown in Figure 13. Specifically, we will describe the case where antennas 20B, 20D, and 20F are removed in a configuration like that shown in Figure 13. When the determination unit 62 detects a discharge, the screen generation unit 64 displays a graph of high discharge intensity corresponding to the position of the antenna 20 with the highest discharge intensity among the radio wave signals detected by multiple antennas 20A, 20C, 20E, and 20G.

[0131] Based on the signal strength distribution comparison displayed on the display unit 80, the user can identify the location corresponding to the antenna 20 with the highest discharge intensity as the discharge point.

[0132] This method allows for a reduction in the number of antennas while not only detecting the occurrence of electrical discharges but also identifying the location of the discharge.

[0133] (Embodiment 3) In Embodiment 3, a method for identifying the location where a discharge occurred will be described.

[0134] Figure 20 illustrates an insulation degradation detection system 110 according to Embodiment 3.

[0135] Referring to Figure 20, the insulation degradation detection system 110 differs from the insulation degradation detection system 100 described in Figure 3 in that PC60 has been replaced with PC61. PC61 differs from PC60 in that it is newly equipped with a location identification unit 66.

[0136] The location identification unit 66 identifies the discharge location based on the signal strength distribution comparison described in Embodiment 2 and displays it on the display unit 80. Specifically, the location identification unit 66 identifies the location corresponding to the antenna 20D with the highest discharge strength based on the signal strength distribution comparison described in Figure 13 as the discharge location, and displays information regarding the identified location on the display unit 80. This makes it easy for the user to understand the location of the discharge location. The same can be applied to the other examples in Figures 14 to 19.

[0137] (Other forms) In other forms, the determination process of the determination unit 62 may be configured to determine the detection of a discharge using machine learning.

[0138] Specifically, data relating discharge intensity and phase information when a discharge occurs is used as training data to generate a trained model for inferring discharge from an insulator.

[0139] The determination unit 62 uses the generated trained model to detect discharge from the insulator based on data that associates discharge intensity with phase information.

[0140] When generating a trained model, it is possible to use known learning algorithms such as supervised learning, unsupervised learning, and reinforcement learning. For example, one could apply the k-means clustering method, which is an unsupervised learning method, to detect discharges based on whether or not they belong to a cluster. Not limited to non-hierarchical clustering using the k-means method, other known clustering algorithms may be used. For example, hierarchical clustering methods such as the shortest distance method may be used. Furthermore, in supervised learning, the data can be processed in the same way as time series data by setting the horizontal axis to phase and the vertical axis to discharge intensity. Therefore, it is possible to use RNN (Recurrent Neural Network), which is one of the neural networks that can take time series data as input, gradient boosting, which is one of the decision trees, and autoregressive integrated moving average (ARIMA) models based on statistical methods. In addition, these outputs can be used for anomaly detection, which divides them into two values: normal (no discharge) and abnormal (discharge present), or for classification, which divides them into three values: normal (no discharge), partial discharge, and spark discharge, or for regression prediction, which predicts the discharge state several days to several years in the future. Furthermore, since discharge is highly dependent on temperature and humidity conditions, it is desirable to learn the tendencies of these changes over time and in the environment through reinforcement learning, as this can reduce false detections.

[0141] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope of the claims are intended to be included.

[0142] 1 Power receiving and transforming equipment, 10 Switchboard, 20 Antenna, 30 Coaxial cable, 40 Detector, 41 Bandpass filter, 42 Amplification and absolute value conversion circuit, 43 Peak hold circuit, 44 A / D conversion circuit, 46 D / A conversion circuit, 45 Zero value invalidation processing circuit, 47 Reset signal generator, 60, 61 PC, 62 Judgment unit, 64 Screen generation unit, 66 Location identification unit, 100, 110 Insulation degradation detection system.

Claims

1. An insulation degradation detection system comprising: an antenna provided for a power receiving and transforming equipment for detecting radio waves; a detection unit connected to the antenna for detecting radio wave signals received by the antenna; and a determination unit for detecting discharge of the power receiving and transforming equipment based on the relationship between the radio wave signal detected by the detection unit and the AC power supply of the power receiving and transforming equipment when detecting the radio wave signal, wherein the antenna detects radio waves originating from partial discharge or spark discharge in a band of at least 180 MHz to 800 MHz.

2. The insulation degradation detection system according to claim 1, wherein the detection unit includes a peak hold circuit that holds the maximum value of the radio wave signal received by the antenna.

3. The insulation degradation detection system according to claim 1, wherein the determination unit detects a discharge of the substation based on the radio wave signal detected by the detection unit and the phase relationship of the three-phase AC power supply of the substation when detecting the radio wave signal.

4. The insulation degradation detection system according to claim 3, wherein the determination unit detects a discharge of the substation when the detection unit detects a radio wave signal during the rising and falling of any phase of the three-phase AC power supply of the substation.

5. The insulation degradation detection system according to claim 1, wherein the determination unit detects a discharge of the substation when the detection unit detects the radio wave signal at a period that is a constant multiple of the frequency of the AC power supply of the substation.

6. The insulation degradation detection system according to claim 5, wherein the determination unit detects a discharge of the substation when the detection unit detects the radio wave signal two or more times during one cycle of the AC power supply of the substation.

7. The insulation degradation detection system according to claim 6, wherein the determination unit detects another discharge of the substation when the detection unit detects the radio wave signal two or more times during one cycle of the AC power supply of the substation, and detects yet another radio wave signal at a position where the phase of the AC power supply is shifted by 60 degrees or 120 degrees relative to the detected radio wave signal.

8. The insulation degradation detection system according to claim 1, wherein the radio wave signal has a specific distribution with respect to the phase of the AC power supply.

9. The insulation degradation detection system according to claim 8, wherein the specific distribution is a normal distribution.

10. The insulation degradation detection system according to claim 1, wherein the determination unit detects a discharge of the substation based on whether the signal amplitude of the radio wave signal is greater than or equal to a threshold value and the relationship with the AC power supply of the substation when detecting the radio wave signal.

11. The insulation degradation detection system according to claim 10, wherein the determination unit detects a spark discharge in the substation equipment when the signal amplitude of the radio wave signal is greater than or equal to a first threshold and based on the relationship with the AC power supply of the substation equipment when detecting the radio wave signal, and the determination unit detects a partial discharge in the substation equipment when the signal amplitude of the radio wave signal is greater than or equal to a second threshold and less than the first threshold and based on the relationship with the AC power supply of the substation equipment when detecting the radio wave signal.

12. The insulation degradation detection system according to claim 1, wherein the antenna is positioned facing an insulator within the substation equipment.

13. The insulation degradation detection system according to claim 12, wherein the antenna is positioned opposite a busbar and cable that are in close proximity to or in contact with an insulating material in the substation where partial discharge may occur.

14. The insulation degradation detection system according to claim 12, wherein the insulating material is an epoxy resin or a polyester resin.

15. The insulation degradation detection system according to claim 12, wherein the insulator is porcelain or ceramic.

16. The insulation degradation detection system according to claim 1, further comprising: a plurality of antennas provided in the substation equipment; a plurality of detection units provided corresponding to each of the plurality of antennas; and a display unit for displaying the detection results from the plurality of detection units.

17. The insulation degradation detection system according to claim 14, wherein the display unit displays a screen showing a comparison of the signal strength distributions of the radio wave signals from the plurality of detection units.

18. The insulation degradation detection system according to claim 14, further comprising a location identification unit that identifies the discharge location of the power receiving and transforming equipment based on the signal strength of the radio wave signals from the plurality of detection units.

19. The insulation degradation detection system according to claim 16, wherein the location identification unit identifies the discharge location of the power receiving and transforming equipment based on a comparison of the signal intensity distributions of the radio wave signals from the plurality of detection units, and the display unit displays the discharge location of the power receiving and transforming equipment identified by the location identification unit.

20. The insulation degradation detection system according to claim 1, wherein the antenna is a monopole antenna including an inverted F antenna or an inverted L antenna, and conduction is established between the counterpoise of the monopole antenna and a conductor that becomes the reference potential of the power receiving and transforming equipment.

21. The insulation degradation detection system according to claim 1, wherein the antenna detects radio waves in the frequency band between 180 MHz and 800 MHz where the difference in signal intensity between the radio wave signal originating from discharge and the radio wave signal originating from noise when no discharge is occurring is the largest.

22. An insulation degradation detection method comprising the steps of detecting a radio wave signal via an antenna provided for a power receiving and transforming equipment, and detecting a discharge of the power receiving and transforming equipment based on the relationship between the detected radio wave signal and the AC power supply of the power receiving and transforming equipment when detecting the radio wave signal, wherein the detection step detects radio waves originating from a partial discharge or spark discharge in a band of at least 180 MHz to 800 MHz.