JP2023014017A - Partial discharge detection device and partial discharge detection method - Google Patents

Abstract

To detect partial discharge in a cable in simple processing with a simple configuration.SOLUTION: A partial discharge detection device for detecting partial discharge in a cable having a linear conductor that transmits commercial AC power, an insulation layer that covers the periphery of the conductor and a shielding layer being a conductor that covers the periphery of the insulation layer, comprises: a current detection unit which detects the current flowing through the shielding layer; a generation unit which generates data indicating the correspondence between a phase to the AC voltage of the commercial AC power of the current detected by the current detection unit and the electric charge amount of the current; and a discharge detection unit which determines the periodicity of the electric charge amount in the data generated by the generation unit and detects the partial discharge on the basis of the determination result.SELECTED DRAWING: Figure 11

Description

The present disclosure relates to a partial discharge detection device and a partial discharge detection method.

Conventionally, techniques have been proposed for detecting partial discharges in underground cables and discovering deterioration of insulating layers at an early stage based on the detection results of partial discharges.

For example, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2008-45977) discloses the following insulation diagnosis device. That is, the insulation diagnosis device includes a receiving section that is connected to a partial discharge detection sensor for detecting partial discharge and receives a detection signal from the partial discharge detection sensor; Insulation that determines partial discharge by sampling the signal level for each frequency and comparing the signal level determined to be at the peak of the commercial voltage and the signal level determined to be asynchronous with the commercial voltage for each frequency to be diagnosed a diagnostic unit;

Further, for example, Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2001-249156) discloses the following insulation diagnosis device. That is, the insulation diagnosis device has a partial discharge sensor, a noise sensor, and an insulation diagnosis unit connected to each of the sensors. For two cycles of the power supply, the partial discharge signal and the noise signal obtained by the sampling are each acquired as one waveform data, and the acquisition of each waveform data is repeated a predetermined number of times every second, and the waveform data obtained by the predetermined number of times is obtained. obtaining an averaged waveform for each of the partial discharge signal and the noise signal; differentially calculating the averaged waveform of the partial discharge signal and the averaged waveform of the noise signal; The data obtained by extracting and grouping burst points with periodicity from the waveform is divided into cycles, and the AND of each cycle is obtained to obtain a data area with periodicity, its data area and 1/4 cycle. By determining the point of deviation and comparing the data value in the data area in the differential waveform with the data value around the point that is shifted by 1/4 cycle, it is possible to determine whether partial discharge has occurred. judge.

JP-A-2008-45977 JP-A-2001-249156

Beyond the techniques described in Patent Documents 1 and 2, a technique capable of detecting partial discharge in a cable with simple processing and configuration is desired.

The present disclosure has been made to solve the above problems, and its object is to provide a partial discharge detection device and a partial discharge detection method capable of detecting partial discharge in a cable with simple processing and configuration. That is.

The partial discharge detection device of the present disclosure is a partial discharge in a cable having a linear conductor that transmits commercial AC power, an insulating layer that surrounds the conductor, and a shielding layer that is a conductor that surrounds the insulating layer. A partial discharge detection device that detects a current, a current detection unit that detects the current flowing through the shielding layer, a phase of the current detected by the current detection unit with respect to the AC voltage of the commercial AC power, and the current a generation unit for generating data indicating a correspondence relationship between the charge amount and a discharge detection unit for determining the periodicity of the charge amount in the data generated by the generation unit and detecting the partial discharge based on the determination result and a part.

One aspect of the present disclosure can be implemented not only as a partial discharge detection device including such a characteristic processing unit, but also as a semiconductor integrated circuit that implements part or all of the partial discharge detection device, It can be implemented as a detection system that includes a partial discharge detection device.

According to the present disclosure, partial discharge in a cable can be detected with simple processing and configuration.

FIG. 1 is a diagram showing the configuration of a power transmission system according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating an example of a configuration of an underground cable used in a power transmission system according to an embodiment of the present disclosure; FIG. 3 is a diagram illustrating an example of a connection method of an underground cable in a normal connection section used in the power transmission system according to the embodiment of the present disclosure. FIG. 4 is a diagram illustrating an example of a connection method of an underground cable at an insulated joint used in the power transmission system according to the embodiment of the present disclosure. FIG. 5 is a diagram illustrating another example of a connection method of an underground cable at an insulated joint used in the power transmission system according to the embodiment of the present disclosure. FIG. 6 is a diagram showing the configuration of a partial discharge detection system according to an embodiment of the present disclosure. FIG. 7 is a diagram showing the configuration of the partial discharge detection device according to the embodiment of the present disclosure. FIG. 8 is a diagram showing the configuration of CT in the partial discharge detection device according to the embodiment of the present disclosure. FIG. 9 is a diagram showing the configuration of a partial discharge detection device according to a modification of the embodiment of the present disclosure. FIG. 10 is a diagram showing an example of attachment of metal foil electrodes in the partial discharge detection device according to the embodiment of the present disclosure. FIG. 11 is a diagram showing the configuration of the processing unit in the partial discharge detection device according to the embodiment of the present disclosure. FIG. 12 is a diagram showing an example of data Dt generated by the generator in the partial discharge detection device according to the embodiment of the present disclosure. FIG. 13 is a diagram showing an example of data Dt generated by the generator in the partial discharge detection device according to the embodiment of the present disclosure. FIG. 14 is a diagram showing an example of data Dt generated by the generator in the partial discharge detection device according to the embodiment of the present disclosure. FIG. 15 is a diagram showing an example of extraction processing by the discharge detection unit in the partial discharge detection device according to the embodiment of the present disclosure. FIG. 16 is a diagram showing an example of extraction processing by the discharge detection unit in the partial discharge detection device according to the embodiment of the present disclosure. FIG. 17 is a diagram showing an example of data Dtr generated by the discharge detection unit in the partial discharge detection device according to the embodiment of the present disclosure. FIG. 18 is a diagram showing an example of data Dtr generated by the discharge detection unit in the partial discharge detection device according to the embodiment of the present disclosure. FIG. 19 is a diagram showing an example of data Dtr generated by the discharge detection unit in the partial discharge detection device according to the embodiment of the present disclosure. FIG. 20 is a diagram showing an example of data Dtr generated by the discharge detection unit in the partial discharge detection device according to the embodiment of the present disclosure. FIG. 21 is a diagram showing an example of correlation coefficient calculation by the discharge detection unit in the partial discharge detection device according to the embodiment of the present disclosure. FIG. 22 is a diagram showing an example of correlation data generated by the discharge detector in the partial discharge detection device according to the embodiment of the present disclosure; FIG. 23 is a diagram showing an example of correlation data generated by the discharge detector in the partial discharge detection device according to the embodiment of the present disclosure; FIG. 24 is a diagram showing an example of data Dt generated by the generator in the partial discharge detection device according to the modification of the embodiment of the present disclosure. FIG. 25 is a diagram showing an example of the maximum charge amount Qmax specified by the discharge detection unit in the partial discharge detection device according to the modification of the embodiment of the present disclosure. FIG. 26 is a diagram showing an example of data Dtr generated by the discharge detection unit in the partial discharge detection device according to the modification of the embodiment of the present disclosure. FIG. 27 is a diagram showing an example of data Dt generated by the generator in the partial discharge detection device according to the modification of the embodiment of the present disclosure. FIG. 28 is a diagram showing an example of data Dtr generated by the discharge detection unit in the partial discharge detection device according to the modification of the embodiment of the present disclosure. FIG. 29 is a diagram showing an example of a histogram Hq generated by the generator in the partial discharge detection device according to the modification of the embodiment of the present disclosure. FIG. 30 is a flow chart defining an example of an operation procedure when the partial discharge detection device according to the embodiment of the present disclosure detects partial discharge.

First, the contents of the embodiments of the present disclosure will be listed and described.

(1) A partial discharge device according to an embodiment of the present disclosure includes a linear conductor that transmits commercial AC power, an insulating layer that surrounds the conductor, and a shielding layer that is a conductor that surrounds the insulating layer. A partial discharge detection device for detecting partial discharge in a cable comprising: a current detection unit for detecting a current flowing through the shielding layer; and an alternating current of the commercial AC power of the current detected by the current detection unit. a generation unit for generating data indicating a correspondence relationship between a phase with respect to voltage and the charge amount of the current; determining periodicity of the charge amount in the data generated by the generation unit; and a discharge detector for detecting partial discharge.

The charge amount of the current flowing through the shield layer corresponds to the charge amount of the partial discharge. A configuration that detects partial discharge based on the sex determination result makes it possible to detect partial discharge in a cable with simple processing and configuration, compared to a configuration that detects partial discharge using, for example, AI (Artificial Intelligence). .

(2) In (1) above, the generating unit may generate multi-cycle data, which is the data indicating the correspondence relationship between the phase and the charge amount in each of a plurality of cycles of the AC voltage, The discharge detection unit may determine the periodicity of the charge amount using a statistical value of the charge amount for each phase in the multiple period data.

With such a configuration, the influence of variations in current detection results can be reduced, and partial discharge in the cable can be detected more accurately.

(3) In (2) above, the discharge detection unit extracts a portion of the multiple-cycle data using a threshold value set based on the statistical value, and extracts the The periodicity of the amount of charge may be determined.

With such a configuration, it is possible to reduce the influence of noise that is constantly included in the detected current, so that partial discharge in the cable can be detected more accurately.

(4) In (3) above, the periodicity of the amount of charge of the current determined to deviate from the steady state of the current may be determined based on the statistical value.

With such a configuration, for example, by periodically determining the steady state, it is possible to detect seasonal variations in noise intensity, time-of-day variations in noise intensity, and underground cable fluctuations. Stationary noise can be removed from the data indicating the correspondence between the phase and the charge amount, taking into consideration the fluctuations in the magnitude of the noise that accompany changes in the surrounding environment.

(5) In any one of (2) to (4) above, the partial discharge detection device further includes the A determination unit may be provided for specifying a maximum amount of charge, which is the maximum value of the amount of charge, and determining a minimum value among the specified maximum amounts of charge as a threshold value, wherein the discharge detection unit A portion of the multi-cycle data may be extracted using the threshold value determined by and the periodicity of the charge amount in the extracted multi-cycle data may be determined.

With such a configuration, the charge amount of noise is determined as a threshold value without requiring the user's knowledge and skill to distinguish partial discharge from noise, and the determined threshold value is used to more accurately detect noise from data. can be removed.

(6) In any one of (1) to (5) above, the generation unit may generate the data at generation timing according to a predetermined generation cycle, and the discharge detection unit may generate the data at the first generation timing. when the number of pairs of the phase and the amount of charge included in the first data extracted from the data generated in is less than a predetermined value, the extracted first data and the first generation The periodicity of the charge amount may be determined based on the second data extracted from the data generated at the second generation timing different from the timing.

With such a configuration, it is possible to determine the periodicity of the amount of electric charge based on a plurality of extracted data, so that weak partial discharge can be detected more accurately.

(7) In any one of (1) to (6) above, the discharge detection unit may obtain the partial discharge detection result by providing the data to a learning model.

With such a configuration, it is possible to more accurately detect partial discharge using machine learning methods.

(8) In any one of (1) to (7) above, the discharge detection unit determines the periodicity of the charge amount based on a correlation between the data and the phase-shifted data. good too.

With such a configuration, the periodicity of the charge amount can be determined more accurately based on the peak position of the charge amount in the data indicating the correspondence between the phase and the charge amount. In addition, for example, in a 3-phase 3-wire cable, even if the generated data includes a peak derived from partial discharge in a cable other than the cable to be detected, the periodicity of the charge amount can be accurately determined. can judge.

(9) In any one of the above (1) to (8), the discharge detection unit calculates the sum of the charge amount in each of a plurality of intervals obtained by dividing one cycle of the AC voltage into a plurality of phase ranges. Further, the periodicity of the sum in the plurality of sections may be determined as the periodicity of the charge amount.

With such a configuration, it is possible to emphasize the peak of the charge amount based on the partial discharge in the data indicating the correspondence between the phase and the charge amount, so that the periodicity of the charge amount can be determined more accurately.

(10) In (9) above, the phase range may be set such that a phase difference of 180° of the total sum for each section can be determined.

When partial discharge occurs in the cable, the charge amount of the current flowing through the shielding layer has two peaks with a phase difference of 180°. ° periodicity can be determined more accurately.

(11) In any one of (1) to (10) above, the generation unit generates polarity information indicating the polarity of the charge amount, and the discharge detection unit controls the polarity information generated by the generation unit. The partial discharge may be detected further based on.

Since the partial discharge has periodicity according to the polarity of the AC voltage, such a configuration can suppress erroneous detection based on the non-periodic charge amount that is not caused by the partial discharge.

(12) In any one of (1) to (11) above, the partial discharge detection device further includes a plurality of bandpasses having different passbands for receiving signals based on the current detected by the current detection unit. A filter may be provided, and the discharge detection unit may select one of the plurality of bandpass filters based on the data generated by the generation unit, The generator may generate the data based on the output signal of the bandpass filter selected by the discharge detector.

With such a configuration, noise other than stationary noise, such as low-frequency noise derived from the inverter, can be reduced.

(13) A partial discharge detection method according to an embodiment of the present disclosure includes a linear conductor that transmits commercial AC power, an insulating layer that surrounds the conductor, and a shield that is a conductor that surrounds the insulating layer. a partial discharge detection method for detecting partial discharge in a cable having a layer comprising: detecting a current flowing through the shielding layer; a phase of the detected current with respect to the AC voltage of the commercial AC power; and determining the periodicity of the charge amount in the generated data, and detecting the partial discharge based on the determination result.

The charge amount of the current flowing through the shield layer corresponds to the charge amount of the partial discharge. The method of detecting partial discharge based on the sex determination result can detect partial discharge in the cable with simple processing and configuration compared to the method of detecting partial discharge using AI, for example.

Embodiments of the present disclosure will be described below with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated. Moreover, at least part of the embodiments described below may be combined arbitrarily.

[Configuration and basic operation]
FIG. 1 is a diagram showing the configuration of a power transmission system according to an embodiment of the present disclosure. Referring to FIG. 1, a power transmission system 502 includes underground cables 10A, 10B, 10C, normal connections 41A, 41B, insulated connections 42A, 42B, and ground connections 43A, 43B. In each connection, three connections are actually provided corresponding to each of the three-phase underground cables 10A, 10B, and 10C, but FIG. 1 shows one connection for simplification. there is Hereinafter, each of the underground cables 10A, 10B, and 10C is also referred to as the underground cable 10, each of the normal connection portions 41A and 41B is also referred to as the normal connection portion 41, and each of the insulated connection portions 42A and 42B is also referred to as the insulated connection portion 42. Each of the ground connection portions 43A and 43B is also referred to as a ground connection portion 43. At least a portion of transmission system 502 is provided, for example, in an underground portion of the power system.

Ground connection section 43 includes cable terminals 11A, 11B, and 11C. The underground cable 10 is connected to the cable terminals 11A, 11B and 11C at the ground connection portion 43 . More specifically, underground cable 10A is connected to cable terminal 11A, underground cable 10B is connected to cable terminal 11B, and underground cable 10C is connected to cable terminal 11C.

The ground connection portion 43 is provided, for example, in a substation where the underground cable 10 appears above the ground. The normal connection portion 41 and the insulated connection portion 42 are provided inside the manhole 31 .

FIG. 2 is a diagram illustrating an example of a configuration of an underground cable used in a power transmission system according to an embodiment of the present disclosure; FIG. 2 shows a cross-sectional view of underground cable 10 . Referring to FIG. 2, underground cable 10 includes, in order from the center, a linear conductor 71 that transmits commercial AC power, an internal semiconductive layer 72, and an insulator 73 made of crosslinked polyethylene that is an insulating layer. , an outer semiconducting layer 74 which is a semiconducting tape, a conductive shielding layer 75, and a sheath 76 made of vinyl. That is, the inner semiconducting layer 72 surrounds the conductor 71, the insulator 73 surrounds the inner semiconducting layer 72, the outer semiconducting layer 74 surrounds the insulator 73, and the shielding layer 75 which is a conductor Surrounding the outer semi-conducting layer 74 is a sheath 76 surrounding the shielding layer 75 .

A conductor 71 in the underground cable 10 is used for power transmission and is applied with a high voltage. The shielding layer 75 is electrically conductive while being grounded in the middle of the underground cable 10 . Therefore, the voltage on shield layer 75 is lower than on conductor 71 .

In the power transmission system 502, as an example, a three-phase three-wire system is used as a power distribution system. In power transmission system 502, underground cables 10A, 10B, and 10C are provided as three-phase underground cables 10. FIG. In the following, since the connection method at each connection portion of the underground cable 10 is complicated, the configuration of each portion will be simplified for the sake of simplicity.

Referring again to FIG. 1, the shielding layer 75 of each of the underground cables 10A, 10B, 10C is exposed at the cable terminals 11A, 11B, 11C. Terminals are provided at connection portions between the shielding layer 75 and the grounding cable 14 and the like.

Underground cables 10A, 10B, 10C are connected to ground node 15 at cable terminals 11A, 11B, 11C, respectively. More specifically, the shielding layer 75 of each underground cable 10 is grounded by connecting the terminal provided to each of the underground cables 10A, 10B, 10C to the ground node 15 via the grounding cable 14 or the like. be.

For example, the underground cable 10 is composed of a plurality of cables whose ends are connected at normal connection portions 41 and insulated connection portions 42 .

FIG. 3 is a diagram illustrating an example of a connection method of an underground cable in a normal connection section used in the power transmission system according to the embodiment of the present disclosure. FIG. 3 mainly shows the conductor 71 and the shielding layer 75 of the underground cable 10A for ease of explanation. The contents described below are the same for the underground cable 10B and the underground cable 10C.

Referring to FIG. 3, underground cables 10A1 and 10A2 are connected at normal connection portion 41 . In the normal connection portion 41, for example, the shielding layer 75 of the underground cables 10A1 and 10A2 is exposed at the connection portion between the conductors 71 of the underground cables 10A1 and 10A2. In the ordinary connection portion 41, the shielding layer 75 of the underground cable 10A1 and the shielding layer 75 of the underground cable 10A2 are connected using the connecting cable 12, for example.

When shielding layer 75 of underground cable 10A1 and shielding layer 75 of underground cable 10A2 are connected, terminal 81 is provided at an exposed portion of shielding layer 75 of underground cable 10A2, for example. Note that the terminal 81 may be provided at an exposed portion of the shielding layer 75 of the underground cable 10A1. By connecting the terminal 81 to the ground node 13 via the ground cable 14, the shield layer 75 of the underground cable 10A is grounded.

FIG. 4 is a diagram illustrating an example of a connection method of an underground cable at an insulated joint used in the power transmission system according to the embodiment of the present disclosure. FIG. 4 mainly shows the conductor 71 and the shielding layer 75 of the construction of the underground cable 10A for ease of explanation. The contents described below are the same for the underground cable 10B and the underground cable 10C.

Referring to FIG. 4 , underground cables 10A 1 and 10A 2 are connected at insulating connection portion 42 . In the insulated connection portion 42, for example, the shielding layers 75 of the underground cables 10A1 and 10A2 are exposed at the connecting portions between the conductors 71 of the underground cables 10A1 and 10A2, and the terminals 81 and the like are provided at the exposed portions.

When the conductor 71 of the underground cable 10A1 and the conductor 71 of the underground cable 10A2 are connected at the insulated connection portion 42, for example, the terminal 81 of the underground cable 10A1 and the terminal 81 of the underground cable 10A2 are connected using the cable 12. By connecting the wires, the shielding layer 75 of the underground cable 10A1 and the shielding layer 75 of the underground cable 10A2 are connected, and thus have the same function as the ordinary connection portion 41 .

FIG. 5 is a diagram illustrating another example of a connection method of an underground cable at an insulated joint used in the power transmission system according to the embodiment of the present disclosure. Referring to FIG. 5 , underground cables 10A1 and 10A2 are connected, underground cables 10B1 and 10B2 are connected, and underground cables 10C1 and 10C2 are connected at insulating connection portion 42 . In the insulated connection portion 42, for example, the shielding layer 75 of the underground cables 10A1 and 10A2 is exposed at the connection portion between the conductors 71 of the underground cables 10A1 and 10A2, and at the connection portion between the conductors 71 of the underground cables 10B1 and 10B2 The shielding layers 75 of the underground cables 10B1 and 10B2 are exposed, the shielding layers 75 of the underground cables 10C1 and 10C2 are exposed at the connecting portions between the conductors 71 of the underground cables 10C1 and 10C2, and the terminals 81 and the like are provided at the exposed portions. be provided.

In the insulating connection portion 42, for example, by connecting the terminal 81 of the underground cable 10A1 and the terminal 81 of the underground cable 10B2 using the cable 12, the shielding layer 75 of the underground cable 10A1 and the shielding of the underground cable 10B2 are connected. Layer 75 is connected, and by connecting terminal 81 of underground cable 10B1 and terminal 81 of underground cable 10C2 using cable 12, shielding layer 75 of underground cable 10B1 and shielding layer 75 of underground cable 10C2 are connected. are connected, and by connecting the terminal 81 of the underground cable 10C1 and the terminal 81 of the underground cable 10A2 using the cable 12, the shielding layer 75 of the underground cable 10C1 and the shielding layer 75 of the underground cable 10A2 are Connected.

Thus, in power transmission system 502 , underground cable 10 may be cross-bonded at insulated connection 42 .

[Partial discharge detector]
FIG. 6 is a diagram showing the configuration of a partial discharge detection system according to an embodiment of the present disclosure. FIG. 6 mainly shows an underground cable 10A of the underground cables 10 for ease of explanation. The contents described below are the same for the underground cable 10B and the underground cable 10C.

Referring to FIG. 6, partial discharge detection system 501 includes partial discharge detection devices 500A, 500B, and 500C. Hereinafter, each of partial discharge detection devices 500A, 500B, and 500C is also referred to as partial discharge detection device 500. FIG. Partial discharge detection system 501 is used in power transmission system 502 .

Partial discharge detection device 500 is provided corresponding to normal connection portion 41 , insulated connection portion 42 and ground connection portion 43 , for example. In the example shown in FIG. 6, the partial discharge detection device 500A is provided corresponding to the normal connection portion 41A, and the partial discharge detection device 500B is provided corresponding to the insulated connection portion 42B. The device 500C is provided corresponding to the ground connection portion 43A.

For example, a power coil is attached to the underground cable 10A. An induced current due to the current flowing through the conductor 71 of the underground cable 10 flows in the power supply coil. This allows the power coil to draw current. Partial discharge detection device 500 operates with electric power obtained, for example, from a power supply coil.

The partial discharge detection device 500 detects partial discharge in the underground cable 10A. Partial discharge detection device 500 may be configured to detect partial discharge in cables other than underground cables, such as cables laid on bridges.

[Configuration of partial discharge detection device]
FIG. 7 is a diagram showing the configuration of the partial discharge detection device according to the embodiment of the present disclosure. Referring to FIG. 7 , partial discharge detection device 500 includes signal detection section 100 and processing section 200 . Signal detector 100 is an example of a current detector. Signal detection section 100 includes a current transformer 110 and a signal output section 120 . Hereinafter, the current transformer 110 is also referred to as CT110.

The signal detector 100 detects current flowing through the shielding layer 75 of the underground cable 10A. More specifically, the signal detection section 100 is electromagnetically coupled to the shielding layer 75 at, for example, the normal connection section 41, the insulation connection section 42, or the ground connection section 43 of the underground cable 10A. The signal detection unit 100 outputs to the processing unit 200 a detection signal, which is an analog signal corresponding to the induced current of the current flowing through the shielding layer 75 of the underground cable 10A.

Based on the detection signal received from the signal detection unit 100, the processing unit 200 detects partial discharge in the underground cable 10A. Note that, when the underground cable 10 is cross-bonded at the insulating connection portion 42, the processing unit 200 detects the underground cable based on the detection signal corresponding to the induced current of the current flowing through the shield layer 75 of the underground cable 10A. It may be configured to detect partial discharge in at least one of the cable 10B and the underground cable 10C.

[Signal detector]
FIG. 8 is a diagram showing the configuration of CT in the partial discharge detection device according to the embodiment of the present disclosure. Referring to FIG. 8, CT 110 includes ring core 101 and winding 102 . A winding 102 is wound around the ring core 101 . Winding 102 is connected to signal output section 120 . The number of turns of winding 102 in ring core 101 is, for example, 1 to 7 turns.

CT 110 is attached, for example, such that conductive cable 53 passes through ring core 101 . Conductive cable 53 is, for example, cable 12 or grounding cable 14 . More specifically, referring to FIGS. 4 and 6 again, the CT 110 of the partial discharge detection device 500A in the normal connection portion 41A is attached so that the grounding cable 14 penetrates the ring core 101. As shown in FIG. The CT 110 of the partial discharge detection device 500B in the insulating connection portion 42B is attached so that the cable 12 connecting the shielding layer 75 of the underground cable 10A1 and the shielding layer 75 of the underground cable 10A2 passes through the ring core 101. Further, the CT 110 of the partial discharge detection device 500C in the ground connection portion 43A is attached so that the grounding cable 14 penetrates the ring core 101. As shown in FIG. When current flows through shield layer 75 and conductive cable 53 , inductive coupling causes an induced current to flow through winding 102 . The signal output section 120 outputs a detection signal corresponding to the induced current flowing through the winding 102 to the processing section 200 . The signal output unit 120 may be configured to include an amplifier, amplify the detection signal by the amplifier, and output the amplified signal to the processing unit 200 .

Note that the signal detection unit 100 may be configured to include an electromagnetic wave sensor that detects electromagnetic waves generated by current flowing through the shielding layer 75 instead of the CT 110 . In this case, the signal output section 120 outputs to the processing section 200 a detection signal corresponding to the electromagnetic waves detected by the electromagnetic wave sensor.

Alternatively, the signal detection unit 100 may be configured to include a sound wave sensor that detects sound waves generated by current flowing through the shielding layer 75 instead of the CT 110 . In this case, the signal output section 120 outputs a detection signal corresponding to the sound wave detected by the sound wave sensor to the processing section 200 .

FIG. 9 is a diagram showing the configuration of a partial discharge detection device according to a modification of the embodiment of the present disclosure. Referring to FIG. 9 , partial discharge detection device 510 includes signal detection section 100A and processing section 200 . The signal detection section 100A includes metal foil electrodes 105 and 106 and a signal output section 120A. The partial discharge detection system 501 may be configured to include a partial discharge detection device 510 instead of the partial discharge detection device 500 .

The signal detection unit 100A detects changes in potential of the shield layer 75 of the underground cable 10 . More specifically, the signal detection section 100A is electrostatically coupled to the shielding layer 75 at the insulating connection section 42, which is the connection section of the underground cable 10, for example.

FIG. 10 is a diagram showing an example of attachment of metal foil electrodes in the partial discharge detection device according to the embodiment of the present disclosure. 9 and 10, metal foil electrodes 105 and 106 are connected to signal output section 120A.

The metal foil electrodes 105 and 106 are, for example, attached to the surface of the sheath 76 of the underground cable 10 on opposite sides of the insulating connection portion 42 via the insulating tube 77 . More specifically, for example, at the insulating connection portion 42 to which the underground cables 10A1 and 10A2 are connected, the metal foil electrode 105 is attached to the surface of the sheath 76 of the underground cable 10A1, and the metal foil electrode 106 is attached to the surface of the sheath 76 of the underground cable 10A1. It is attached to the surface of the sheath 76 of the cable 10A2. Note that the metal foil electrodes 105 and 106 may be attached so as to cover the outer circumference of the sheath 76 of the underground cable 10A2. Moreover, the position to which each metal foil electrode is attached and the number of metal foil electrodes are not limited, and three or more metal foil electrodes may be attached.

When the potential of shield layer 75 and conductive cable 53 changes, electric field coupling causes a change in potential at metal foil electrodes 105 and 106 . The signal output unit 120A outputs to the processing unit 200 a detection signal corresponding to the potential change of the shielding layer 75 based on the potential change.

[Processing part]
FIG. 11 is a diagram showing the configuration of the processing unit in the partial discharge detection device according to the embodiment of the present disclosure. Referring to FIG. 11 , processing unit 200 includes a filtering unit 210 , an amplifying unit 220 , an ADC (Analog Digital Converter) 230 , a generating unit 250 , a discharge detecting unit 260 and a storage unit 280 . Storage unit 280 is, for example, a non-volatile memory.

The storage unit 280 stores a correspondence table Tb1 that indicates the correspondence between the sample value of the digital signal output from the ADC 230 and the charge amount Q of the current flowing through the shield layer 75 .

The filter processing unit 210 has an analog switch 211 and bandpass filters (BPF) 212A, 212B, and 212C. Each of the BPFs 212A, 212B, and 212C is hereinafter also referred to as the BPF 212 . The three BPFs 212 have different passbands. For example, the passband of BPF 212A is 5 MHz or more and less than 10 MHz, the passband of BPF 212B is 10 MHz or more and less than 20 MHz, and the passband of BPF 212C is 20 MHz or more and less than 30 MHz. Note that the filter processing section 210 may be configured to have four or more BPFs 212 having different passbands.

The BPF 212 receives a signal based on the current flowing through the shielding layer 75 detected by the signal detector 100, ie, a detection signal.

More specifically, analog switch 211 outputs the detection signal received from signal output section 120 or 120A to one of three BPFs 212 . As will be described later, the analog switch 211 receives a switch control signal from the discharge detection unit 260 and switches the BPF 212 to which the detection signal is output according to the received switch control signal.

Receiving the detection signal from the analog switch 211 , the BPF 212 attenuates the components outside its own passband among the frequency components of the received detection signal and outputs the detection signal to the amplifying section 220 .

Amplifying section 220 amplifies the detection signal received from BPF 212 and outputs it to ADC 230 .

ADC 230 converts the detection signal received from amplifying section 220 into a digital signal and outputs the digital signal to generating section 250 .

<Generation unit>
The generation unit 250 generates data indicating the correspondence relationship between the phase Φ of the current detected by the signal detection unit 100 or 100A with respect to the AC voltage of the commercial AC power and the charge amount Q of the current.

More specifically, generating section 250 receives the detection signal from signal output section 120 or 120A, extracts the frequency component of the commercial AC power from the received detection signal, and extracts the frequency component of the commercial AC power based on the extracted detection signal. A zero-crossing point, which is the timing at which the AC voltage becomes zero volts, is detected.

The generation unit 250 calculates the sampling timing of each sample value of the digital signal received from the ADC 230 as the phase Φ with reference to the detected zero-crossing point. The generation unit 250 also compares each sample value with a trigger level, which is a predetermined threshold value, and extracts sample values exceeding the trigger level from the sample values of the received digital signal. For example, the trigger level is set in advance so that the number of sample values exceeding the trigger level per cycle of commercial AC power falls within a predetermined range. Note that the generation unit 250 divides one cycle of the commercial AC power into a plurality of times of a predetermined length that can ensure sufficient phase accuracy, and extracts the sample value that takes the maximum value at each divided time. There may be.

The generation unit 250 sets the charge amount Q corresponding to the sample value that does not exceed the trigger level to zero, and acquires the charge amount Q corresponding to the extracted sample value from the correspondence table Tb1 in the storage unit 280. Data indicating the correspondence between Φ and the absolute value of the amount of charge Q is generated. Note that instead of acquiring the charge amount Q corresponding to the sample value from the correspondence table Tb1 in the storage unit 280, the generation unit 250 uses the absolute value of the sample value exceeding the trigger level as the charge amount Q to generate the data may be configured to generate Hereinafter, the term "charge amount Q" means the absolute value of the charge amount of the current flowing through the shielding layer 75, unless otherwise specified.

For example, generation unit 250 generates data Dt indicating the correspondence relationship between phase Φ and charge amount Q in each of a plurality of cycles of AC voltage of commercial AC power. Data Dt is an example of multi-cycle data.

More specifically, the data Dt representing the correspondence relationship between the phase Φ and the charge amount Q in the generation cycle T1 is generated for each generation cycle T1 that is at least twice the cycle of the AC voltage of the commercial AC power. The generation cycle T1 is, for example, 1 second.

12 to 14 are diagrams showing an example of data Dt generated by the generator in the partial discharge detection device according to the embodiment of the present disclosure. 12 to 14, the horizontal axis indicates the phase Φ [degree], and the vertical axis indicates the absolute value of the charge amount Q [pC]. FIG. 12 shows data Dt generated by the generator 250 in a state where no partial discharge occurs in the underground cable 10A. FIG. 13 shows data Dt generated by the generator 250 when partial discharge occurs in the underground cable 10A. FIG. 14 shows the data Dt generated by the generation unit 250 in a state where partial discharge is not occurring in the underground cable 10A and sudden noise different from stationary noise is occurring. showing. Sudden noise is, for example, low-frequency noise originating from an inverter.

Generation unit 250 generates data Dt at a generation timing according to generation cycle T<b>1 and outputs generated data Dt to discharge detection unit 260 .

For example, generating section 250 sets the trigger level or the amplification factor of amplifying section 220 so that the number of sample values exceeding the trigger level among the sample values of the digital signal received from ADC 230 per unit time is less than a predetermined number. adjust. Specifically, when the number of sample values exceeding the trigger level among the sample values of the digital signal received from the ADC 230 per unit time is greater than or equal to a predetermined value, the generation unit 250 raises the trigger level or raises the trigger level. By outputting the adjustment signal to 220, the amplification factor of the amplifier 220 is lowered. When the amplification factor of the amplification part 220 is adjusted, the generation part 250 updates the correspondence table Tb1 in the storage part 280 according to the adjustment amount of the amplification factor. In addition, when the amplification factor of the amplification part 220 is adjusted, the generation part 250 may be configured to multiply the charge amount Q by a coefficient corresponding to the adjustment amount of the amplification factor instead of updating the correspondence table Tb1.

For example, the generator 250 generates polarity information indicating the polarity of the charge amount Q. FIG. More specifically, generation unit 250 generates polarity information that enables recognition of the polarity of charge amount Q in data Dt, and outputs the generated polarity information to discharge detection unit 260 together with data Dt. Note that the generation unit 250 may be configured to generate data Dt in which the polarity of the charge amount Q is maintained and output to the discharge detection unit 260 .

<Discharge detector>
Discharge detection unit 260 selects one of three BPFs 212 based on data Dt generated by generation unit 250 . More specifically, when discharge detection unit 260 receives data Dt from generation unit 250 and determines that sudden noise occurs in the received data Dt as shown in FIG. A BPF 212 that does not include the frequency of noise in the passband is selected. By outputting the switch control signal to the analog switch 211 , the discharge detection unit 260 switches the output destination of the analog signal from the analog switch 211 to the selected BPF 212 .

For example, generation unit 250 generates data Dt based on the output signal of BPF 212 selected by discharge detection unit 260 . More specifically, generation unit 250 receives from ADC 230 a digital signal based on the detection signal output from BPF 212 selected by discharge detection unit 260, and generates data Dt based on the received digital signal. Data Dt is output to discharge detection unit 260 . For example, generation unit 250 multiplies charge amount Q by a coefficient corresponding to BPF 212 selected by discharge detection unit 260 to generate data Dt.

The discharge detection unit 260 determines the periodicity of the charge amount Q in the data Dt generated by the generation unit 250, and detects partial discharge in the underground cable 10A based on the determination result.

For example, the discharge detection unit 260 receives the data Dt from the generation unit 250 and determines the periodicity of the charge amount Q using the statistical value of the charge amount Q for each phase Φ in the received data Dt. More specifically, the discharge detection unit 260 uses the data Dt received from the generation unit 250 to determine the periodicity of the charge amount Q using the frequency N of the charge amount Q for each phase Φ in the generation cycle T1. Frequency N is an example of a statistic.

(Extraction processing)
The discharge detection unit 260 performs an extraction process of extracting a part of the data Dt using the upper limit value Th1 of the charge amount Q, which is set based on the calculated frequency N of the charge amount Q. FIG.

For example, the discharge detection unit 260 determines the upper limit value Th1 of the charge amount Q in the steady state based on the calculated frequency N of the charge amount Q. As shown in FIG. More specifically, the discharge detection unit 260 determines the upper limit value Th1 of the charge amount Q in a steady state based on the distribution of the charge amount Q in a predetermined period when no partial discharge occurs in the underground cable 10A. do. The amount of charge Q in the steady state is widely distributed without occurring at a specific phase Φ, and its frequency N also appears frequently. Discharge detection unit 260 determines upper limit value Th1 using a statistical method based on the distribution of charge amount Q in a predetermined period.

15 and 16 are diagrams showing an example of extraction processing by the discharge detection unit in the partial discharge detection device according to the embodiment of the present disclosure. 15 and 16, the horizontal axis indicates the phase Φ [degree], and the vertical axis indicates the absolute value of the charge amount Q [pC]. FIG. 15 shows the data Dt before extraction processing by the discharge detection unit 260. As shown in FIG. FIG. 16 shows the data Dtr extracted by the discharge detector 260. As shown in FIG.

15 and 16, discharge detection unit 260 generates data Dtr by performing an extraction process of extracting part of data Dt received from generation unit 250 based on data Dt in a steady state. . More specifically, discharge detection unit 260 generates data Dtr by extracting a combination of phase Φ and charge amount Q in data Dt received from generation unit 250 and having charge amount Q greater than upper limit Th1. . That is, the discharge detection unit 260 generates the noise-removed data Dtr by excluding, from among the sets of the phase Φ and the charge amount Q in the data Dt, the sets in which the charge amount Q is equal to or less than the upper limit value Th1. .

For example, discharge detection unit 260 periodically or irregularly updates upper limit value Th1 of charge amount Q in a steady state. The magnitude of the noise contained in the charge amount Q may fluctuate depending on the season, the time of day, and changes in the surrounding environment of the underground cable. By updating the upper limit value Th1, noise can be removed from the data Dt in consideration of, for example, seasonal fluctuations in the magnitude of noise. can be detected.

(Determination of periodicity)
Based on the frequency N, the discharge detection unit 260 determines the periodicity of the charge amount Q of the current determined to deviate from the steady state. More specifically, the discharge detection unit 260 determines the periodicity of the charge amount Q in the generated data Dtr.

17 to 20 are diagrams showing an example of data Dtr generated by the discharge detector in the partial discharge detection device according to the embodiment of the present disclosure. 17 to 20, the horizontal axis indicates the phase Φ [degree], and the vertical axis indicates the absolute value of the charge amount Q [pC]. FIGS. 17 to 20 show data Dtr in a state where partial discharge is occurring in the underground cable 10A, and data Dtr at different times.

17 to 20, even when partial discharge occurs, the pattern indicating the relationship between phase Φ and charge amount Q in data Dtr differs for each occurrence time. There is a demand for a technique for accurately detecting partial discharge, taking into consideration such seasonal pattern changes.

For example, the discharge detection unit 260 calculates the sum Qsum of the charge quantity Q in each of a plurality of phase intervals Φs obtained by dividing one cycle of the AC voltage of the commercial AC power into a plurality of phase ranges, and calculates the periodicity of the charge quantity Q , the periodicity of the sum Qsum in a plurality of phase intervals Φs is determined. For example, the phase range is set so that the phase difference of 180° in the total sum Qsum for each phase interval Φs can be determined. Two adjacent phase intervals Φs may partially overlap each other. As an example, the phase range is set to 30°.

More specifically, in the generated data Dtr, the discharge detection unit 260 increases the phase Φ1 at the lower end of the phase interval Φs by 5° from 0°, and By calculating the total sum Qsum of the charge amounts Q, section data Dts indicating the correspondence relationship between the 72 phase sections Φs and the total sum Qsum is generated. Specifically, the discharge detection unit 260 detects the phase interval Φs shifted by 5° from the phase interval Φs3 onward, such that the phase interval Φs1 is from 0° to 30° and the phase interval Φs2 is from 5° to 35°. , the sum Qsum is calculated. Note that the total sum Qsum is calculated from 330° to 360° in the phase section Φs67, and the value of the charge amount Q that is increased by 5° from zero is used again from the phase section Φs68 onwards.

Discharge detection unit 260 receives data Dt from generation unit 250 and generates section data Dts each time it generates data Dtr by extracting a portion of the received data Dt.

After generating the section data Dts, the discharge detection unit 260 compares the generated section data Dts with the reference section data Dref, and tentatively determines that partial discharge has occurred in the underground cable 10A based on the comparison result. The reference section data Dref may be section data Dts generated immediately before, or may be average section data generated by averaging a plurality of section data Dts generated in a certain period in the past.

More specifically, discharge detection unit 260 calculates the sum of the squares of the differences in total sum Qsum for each corresponding phase interval Φs between generated interval data Dts and reference interval data Dref, and the calculated sum is a predetermined value. If it is equal to or greater than the threshold, it is tentatively determined that partial discharge has occurred in the underground cable 10A.

When the discharge detection unit 260 tentatively determines that partial discharge has occurred based on the comparison result between the section data Dts and the reference section data Dref, the discharge detection unit 260 uses the section data Dts to determine the periodicity of the sum Qsum.

For example, discharge detection unit 260 determines the periodicity of sum Qsum based on the autocorrelation of section data Dts.

FIG. 21 is a diagram showing an example of correlation coefficient calculation by the discharge detection unit in the partial discharge detection device according to the embodiment of the present disclosure.

Referring to FIG. 21, discharge detection unit 260 generates correlation data R of section data Dts based on the correlation between section data Dts and section data Dts with phase Φ shifted. More specifically, discharge detection unit 260 generates shift interval data Dts, which is interval data Dts obtained by shifting phase interval Φs of interval data Dts, and compares shift amount n of phase interval Φs, interval data Dts, and the shift interval. Correlation data R indicating the correspondence between data Dts and correlation coefficient r(n) is generated. Discharge detection section 260 determines the periodicity of sum Qsum based on generated correlation data R. FIG.

22 and 23 are diagrams showing examples of correlation data generated by the discharge detector in the partial discharge detection device according to the embodiment of the present disclosure. 22 and 23, the horizontal axis indicates the shift amount n, and the vertical axis indicates the correlation coefficient r(n). FIG. 22 shows the correlation data R1 of the section data Dts generated based on the data Dtr generated by performing the extraction process on the data Dt shown in FIG. FIG. 23 shows the correlation data R2 of the section data Dts generated based on the data Dtr generated by performing the extraction process on the data Dt shown in FIG.

Referring to FIG. 22, correlation data R1 has a high correlation coefficient r(n) when the shift amount n is zero, 1, and 71, while the correlation coefficient r(n) is high when the shift amount n is 3 to 70. (n) is approximately zero.

Referring to FIG. 23, correlation data R2 has two minimum values and one maximum value except when the shift amount is zero and 71. In FIG. More specifically, the correlation data R1 has a correlation coefficient r(n) that decreases as the shift amount n increases from zero to about 18, and decreases as the shift amount n increases from about 19 to about 36. The correlation coefficient r(n) increases, decreases as the shift amount n increases from about 37 to about 55, and decreases as the shift amount n increases from about 56 to 71. , the correlation coefficient r(n) increases.

Two minimum values and one maximum value in the correlation data R2 correspond to two peaks of the charge quantity Q shown in FIG.

For example, when the correlation data R has one maximum value and the phase corresponding to the shift amount n of the maximum value is within a predetermined range, the discharge detection unit 260 determines that the sum Qsum has a periodicity of 180°. I judge.

As an example, discharge detection unit 260 uses correlation data R and threshold value ThA to determine whether sum Qsum has 180° periodicity.

That is, when the maximum value of correlation data R is greater than threshold value ThA and the phase corresponding to shift amount n of the maximum value is within the range of, for example, 170° to 190°, discharge detection unit 260 detects sum Qsum is determined to have 180° periodicity.

On the other hand, if the maximum value of correlation data R is equal to or less than threshold ThA, or if the phase corresponding to the shift amount n of the maximum value is outside the range of 170° to 190°, for example, discharge detection section 260 sums It is determined that Qsum does not have 180° periodicity.

For example, the discharge detector 260 detects partial discharge further based on the polarity information generated by the generator 250 . More specifically, the discharge detection unit 260 determines whether the polarity of the charge amount Q in the data Dtr alternates between positive polarity and negative polarity based on the polarity information received from the generation unit 250. .

When the discharge detection unit 260 determines that the sum Qsum has a periodicity of 180° and the polarity of the charge amount Q corresponding to the sum Qsum alternately transitions between positive and negative polarities, It is determined that partial discharge is occurring in the middle cable 10A.

On the other hand, when the discharge detection unit 260 determines that the sum Qsum does not have a periodicity of 180°, or determines that the charge amount Q corresponding to the sum Qsum does not alternate between positive and negative polarities. , it is determined that no partial discharge has occurred in the underground cable 10A.

For example, when the discharge detector 260 determines that partial discharge has occurred in the underground cable 10A, it notifies a server (not shown) of the determination result using PLC (Power Line Communication).

<Modification>
(Another example of determination of periodicity)
For example, discharge detection unit 260 determines that correlation data R has two minimum values and one maximum value, the phase difference corresponding to the difference in shift amount n between the two minimum values is within a predetermined range, and If the phase corresponding to the shift amount n of the maximum value is within a predetermined range, it is determined that the sum Qsum has 180° periodicity.

As an example, discharge detection unit 260 uses correlation data R and thresholds ThA and ThB to determine whether sum Qsum has 180° periodicity. Here, the threshold ThA is assumed to be greater than the threshold ThB.

That is, discharge detecting section 260 determines that the maximum value of correlation data R is greater than threshold ThA, the two minimum values of correlation data R are less than threshold ThB, and the amount of shift n between the two minimum values is n If the phase difference corresponding to the difference between is within the range of, for example, 170° to 190° and the phase corresponding to the shift amount n of the maximum value is within the range of, for example, 170° to 190°, the total sum Qsum is 180° It is determined that there is a periodicity of

On the other hand, discharge detection section 260 determines whether the maximum value of correlation data R is equal to or less than threshold ThA, whether the two minimum values of correlation data R are equal to or more than threshold ThB, or whether the shift between the two minimum values is equal to or greater than threshold ThB. If the phase difference corresponding to the difference in amount n is out of the range, say 170° to 190°, or the phase corresponding to the shift amount n of the maxima is out of the range, say 170° to 190°, then the sum Qsum is not 180° periodic.

(Other example 1 of extraction processing)
Although the discharge detection unit 260 is configured to determine the upper limit value Th1 based on the distribution of the amount of charge Q in a predetermined period in a state in which no partial discharge occurs in the underground cable 10A, the configuration is limited to this. is not. Since the magnitude of noise included in the data Dt generated by the generation unit 250 may vary for each data Dt, in the configuration for extracting a portion of the data Dt using the upper limit value Th1 of the charge amount Q in the steady state, Noise may not be accurately removed from data Dt. On the other hand, the discharge detection unit 260 is configured to determine the upper limit value Th2 of the charge amount Q based on the distribution of the charge amount Q in a predetermined period while partial discharge is occurring in the underground cable 10A. There may be.

Referring to FIG. 15 again, for example, discharge detection unit 260 detects the distribution of charge amount Q when phase Φ is from 0° to 30° and the charge amount when phase Φ is from 135° to 195° in data Dt. The upper limit value Th2 is determined using a statistical method based on the distribution of the amount of charge Q other than the peak value, such as the distribution of Q and the distribution of the amount of charge Q when the phase Φ is from 330° to 360°.

Then, discharge detection unit 260 generates data Dtr by extracting a combination of phase Φ and charge amount Q in data Dt received from generation unit 250 and having charge amount Q greater than upper limit Th2.

For example, every time the discharge detection unit 260 receives the data Dt from the generation unit 250, the discharge detection unit 260 determines the upper limit value Th2 based on the received data Dt. Data Dtr is generated by extracting sets whose quantity Q is greater than the upper limit value Th2. In this manner, the upper limit value Th2 is determined based on the data Dt, and a part of the data Dt is extracted using the determined upper limit value Th2. can be synchronized, noise can be more accurately removed from the data Dt, and weak partial discharge can be detected based on the generated data Dtr, so partial discharge can be detected earlier. be able to.

(Another example 2 of extraction processing)
FIG. 24 is a diagram showing an example of data Dt generated by the generator in the partial discharge detection device according to the modification of the embodiment of the present disclosure. In FIG. 24, the horizontal axis indicates the phase Φ [degree], and the vertical axis indicates the level of the charge quantity Q. In FIG. FIG. 24 shows data Dt with a phase Φ resolution of 5°.

Based on the data Dt, the discharge detection unit 260 specifies the maximum amount of charge Qmax, which is the maximum value of the amount of charge Q in each phase section Φr that divides one cycle of the AC voltage at predetermined intervals. Discharge detection unit 260 determines the minimum value among the specified maximum charge amounts Qmax as upper limit value Th3. The upper limit Th3 is an example of a threshold.

As an example, based on the data Dt received from the generation unit 250, the discharge detection unit 260 detects the maximum amount of electric charge in each of the phase intervals Φr1 to Φr36, which are obtained by dividing 360°, which is one cycle of the AC voltage, at intervals of 10°. Identify Qmax.

FIG. 25 is a diagram showing an example of the maximum charge amount Qmax specified by the discharge detection unit in the partial discharge detection device according to the modification of the embodiment of the present disclosure. In FIG. 25, the horizontal axis indicates the phase interval Φr, and the vertical axis indicates the level of the maximum charge amount Qmax.

Referring to FIG. 25, discharge detection unit 260 determines maximum charge amount Qmax36, which is the smallest value excluding zero among the specified maximum charge amounts Qmax, as upper limit value Th3. As described above, generation unit 250 sets the charge amount Q corresponding to the sample value that does not exceed the trigger level among the sample values of the digital signal received from ADC 230 to zero, Data Dt is generated by obtaining the amount of charge Q corresponding to the sample value exceeding the trigger level from . That is, the data Dt may include zero as the value of the charge amount Q. FIG. On the other hand, the discharge detection unit 260 removes noise by determining the maximum charge amount Qmax36, which is the smallest value excluding zero among the specified maximum charge amounts Qmax, as the upper limit value Th3. It is possible to determine an appropriate upper limit value Th3 for .

FIG. 26 is a diagram showing an example of data Dtr generated by the discharge detection unit in the partial discharge detection device according to the modification of the embodiment of the present disclosure. In FIG. 26, the horizontal axis indicates the phase Φ [degree], and the vertical axis indicates the level of the charge quantity Q. In FIG.

Referring to FIG. 26, discharge detection unit 260 extracts a portion of data Dt using determined upper limit value Th3, and determines the periodicity of charge amount Q in extracted data Dtr. More specifically, discharge detection unit 260 generates data Dtr by extracting a set in which charge amount Q is greater than upper limit value Th3 from among pairs of phase Φ and charge amount Q in data Dt, and generates data Dtr. Determine the periodicity of Q. The discharge detector 260 detects partial discharge in the underground cable 10A based on the periodicity determination result.

For example, every time the discharge detection unit 260 receives the data Dt from the generation unit 250, the discharge detection unit 260 determines the upper limit value Th3 based on the received data Dt. Data Dtr is generated by extracting sets whose quantity Q is greater than the upper limit value Th3. In this manner, the upper limit value Th3 is determined based on the data Dt, and a part of the data Dt is extracted using the determined upper limit value Th3. can be synchronized, noise can be more accurately removed from the data Dt, and weak partial discharge can be detected based on the generated data Dtr, so partial discharge can be detected earlier. be able to.

FIG. 27 is a diagram showing an example of data Dt generated by the generator in the partial discharge detection device according to the modification of the embodiment of the present disclosure. FIG. 27 shows the correspondence relationship between the phase Φ and the frequency N in the data Dt shown in FIG. 24 in a polar coordinate system. In FIG. 27, the argument indicates the phase Φ [degree], and the vector indicates the level of the charge amount Q. In FIG.

FIG. 28 is a diagram showing an example of data Dtr generated by the discharge detection unit in the partial discharge detection device according to the modification of the embodiment of the present disclosure. FIG. 28 shows the correspondence relationship between the phase Φ and the frequency N in the data Dtr shown in FIG. 26 in a polar coordinate system. In FIG. 28, the argument indicates the phase Φ [degree], and the vector indicates the level of the charge amount Q. In FIG.

Referring to FIGS. 27 and 28, data Dtr has the noise removed from data Dt, so that the 180° periodicity of the charge amount Q is easier to recognize than data Dt.

Discharge detection unit 260 is not limited to the configuration that specifies the maximum amount of charge Qmax in each of phase intervals Φr1 to Φr36, which are obtained by dividing one cycle of the AC voltage at intervals of 10°. It may be configured to specify the maximum amount of charge Qmax in each of a plurality of phase intervals Φr separated by intervals other than 10°. Here, if the interval is too small, data Dtr containing a lot of noise may be generated. On the other hand, if the interval is too large, data Dtr from which the charge amount Q component due to partial discharge is removed is generated. There is a possibility that it will be done. The optimum value of the interval differs according to the resolution of the phase Φ in the data Dt. For example, the discharge detection unit 260 determines the interval according to the resolution of the phase Φ in the data Dt, and specifies the maximum charge amount Qmax in each of a plurality of phase intervals Φr that divide one cycle of the AC voltage into the determined intervals. do.

(Other example 3 of extraction processing)
FIG. 29 is a diagram showing an example of a histogram Hq generated by the generator in the partial discharge detection device according to the modification of the embodiment of the present disclosure. In FIG. 29, the horizontal axis indicates the sum of frequencies N, and the vertical axis indicates the level of charge amount Q. In FIG. FIG. 29 is a histogram Hq showing the sum Sn of frequencies N in all phases Φ for each level of charge quantity Q in data Dt shown in FIG.

Referring to FIG. 29, discharge detection unit 260 generates a histogram Hq by aggregating sum Sn of frequency N in all phases Φ for each level of charge amount Q in data Dt received from generation unit 250. do. Here, when partial discharge occurs in the underground cable 10A, the histogram Hq is a frequency distribution Hq1 including a peak P1 derived from the partial discharge charge amount Q and a peak P2 derived from the noise charge amount Q. and Hq2. Here, the level of the charge amount Q1 at the peak P1 is higher than the level of the charge amount Q1 at the peak P2. Therefore, the discharge detection unit 260 determines the level of the charge amount Q corresponding to the change point of the total Sn between the peak P1 and the peak P2 in the histogram Hq as the threshold value used in the extraction process. As an example, the discharge detection unit 260 determines the sum of the average value of the level of the charge amount Q and the variance σ of the level of the charge amount Q in the frequency distribution Hq2 as the upper limit value Th4.

Discharge detection unit 260 generates data Dtr by extracting a set in which the charge amount Q is greater than the upper limit value Th4 from among the sets of the phase Φ and the charge amount Q in the data Dt. The discharge detection unit 260 determines the periodicity of the charge amount Q in the generated data Dtr, and detects partial discharge in the underground cable 10A based on the determination result.

(Other example 4 of extraction processing)
Although the generation unit 250 is configured to generate the data Dt indicating the correspondence relationship between the phase Φ and the charge amount Q in each of a plurality of cycles of the AC voltage of the commercial AC power, the configuration is not limited to this. The generation unit 250 may be configured to generate data Dtx indicating the correspondence relationship between the phase Φ and the charge amount Q in one cycle of the AC voltage of the commercial AC power. After generating data Dtx, generation unit 250 outputs the generated data Dtx to discharge detection unit 260 .

For example, discharge detection unit 260 determines a value obtained by adding a predetermined value to the minimum value of charge amount Q in data Dtx received from generation unit 250 as upper limit value Th5. Discharge detection unit 260 generates data Dtxr by extracting a set in which the charge amount Q is greater than the upper limit value Th5 among the sets of the phase Φ and the charge amount Q in the data Dtx. The discharge detection unit 260 may be configured to determine the periodicity of the charge amount Q in the generated data Dtxr instead of the data Dtr.

Alternatively, discharge detection unit 260 generates an envelope of the maximum value of charge amount Q in data Dtx received from generation unit 250, and determines the minimum value of the generated envelope as upper limit value Th6. Discharge detection unit 260 generates data Dtxr by extracting a set in which the charge amount Q is greater than the upper limit value Th6 among the sets of the phase Φ and the charge amount Q in the data Dtx.

Alternatively, since the amount of charge Q generated by partial discharge has the shape of a normal distribution function in the data Dtx, the discharge detection unit 260 detects , the group corresponding to the shape of the charge amount Q generated by partial discharge is excluded, and the maximum value of the charge amount Q among the remaining groups is determined as the upper limit value Th7. Discharge detection unit 260 generates data Dtxr by extracting a set in which the charge amount Q is greater than the upper limit value Th7 among the sets of the phase Φ and the charge amount Q in the data Dtx.

(Another example 1 of determination of periodicity)
For example, if the number of pairs of phase Φ and charge amount Q included in data Dtr extracted from data Dt generated at the first generation timing is less than a predetermined value, discharge detection unit 260 detects that data Dtr and , and the data Dtr extracted from the data Dt generated at the second generation timing, the periodicity of the charge amount Q is determined.

More specifically, when the number of pairs of the phase Φ and the charge amount Q included in the generated data Dtr is equal to or greater than a predetermined value, the discharge detection unit 260 determines the periodicity of the charge amount Q in the data Dtr. .

On the other hand, when the number of pairs of the phase Φ and the charge amount Q included in the data Dtr1, which is the generated data Dtr, is less than a predetermined value, the discharge detection unit 260 suspends the determination of the periodicity of the charge amount Q, It waits for new data Dt from the generation unit 250 . Discharge detection unit 260 receives new data Dt from generation unit 250 and performs extraction processing on the received data Dt to generate data Dtr2, which is data Dtr. Then, the discharge detection unit 260 generates data Dtr12 including a set of the phase Φ and the charge amount Q included in the data Dtr1 and a set of the phase Φ and the charge amount Q included in the data Dtr2. The periodicity of the charge amount Q in Dtr12 is determined.

(Another example 2 of determination of periodicity)
Although the discharge detection unit 260 is configured to determine the periodicity of the sum Qsum based on the autocorrelation of the section data Dts and detect partial discharge based on the determination result, the configuration is not limited to this.

For example, the discharge detection unit 260 obtains the partial discharge detection result by giving the data Dtr to the learning model.

More specifically, the storage unit 280 stores a learning model that receives the data Dtr and outputs the determination result of the periodicity of the charge amount Q in the received data Dtr. The learning model is generated by subjecting the neural network to machine learning using the data Dtr as learning data so as to determine the presence or absence of partial discharge in the underground cable 10A.

After generating the data Dtr, the discharge detection unit 260 gives the generated data Dtr to the learning model in the storage unit 280, thereby obtaining a determination result as to whether or not partial discharge occurs in the underground cable 10A.

[Flow of operation]
FIG. 30 is a flow chart defining an example of an operation procedure when the partial discharge detection device according to the embodiment of the present disclosure detects partial discharge.

Referring to FIG. 30, first, partial discharge detection device 500 starts detecting current flowing through shield layer 75 of underground cable 10A. More specifically, the partial discharge detection device 500 starts generating detection signals based on the current flowing through the shielding layer 75 (step S102).

Next, partial discharge detection device 500 waits for the timing according to generation cycle T1 (NO in step S104), and at the timing according to generation cycle T1 (YES in step S104), based on the generated detection signal, detects the phase in generation cycle T1. Data Dt indicating the correspondence between Φ and the absolute value of the amount of charge Q is generated (step S106).

Next, the partial discharge detection device 500 performs extraction processing on the generated data Dt. More specifically, partial discharge detection device 500 generates data Dtr by extracting a set of charge amount Q greater than upper limit value Th1, out of the sets of phase Φ and charge amount Q in data Dt (step S108).

Next, based on the generated data Dtr, the partial discharge detection device 500 generates section data Dts indicating the correspondence between the 72 phase sections Φs and the total sum Qsum (step S110).

Next, the partial discharge detection device 500 compares the generated section data Dts with the reference section data Dref. More specifically, the partial discharge detection device 500 calculates the sum of the squares of the differences in the total sum Qsum for each corresponding phase interval Φs between the interval data Dts and the reference interval data Dref, and compares the calculated sum with the predetermined threshold. It compares with the threshold value (step S112).

Next, when the calculated sum is less than the threshold value (NO in step S114), partial discharge detection device 500 determines that no partial discharge is occurring in underground cable 10A, and determines that partial discharge is not occurring in underground cable 10A. (NO in step S104).

On the other hand, if the calculated sum is equal to or greater than the threshold value (YES in step S114), partial discharge detection device 500 tentatively determines that partial discharge is occurring in underground cable 10A, and correlates section data Dts. Data R is generated (step S116).

Next, based on the generated correlation data R, the partial discharge detection device 500 determines whether or not the sum Qsum has 180° periodicity (step S118).

Next, when the partial discharge detection device 500 determines that the sum Qsum does not have a periodicity of 180° (NO in step S120), it determines that the partial discharge does not occur in the underground cable 10A, and the generation period T1 (NO in step S104).

On the other hand, when the partial discharge detection device 500 determines that the sum Qsum has a periodicity of 180° (YES in step S120), it determines that partial discharge is occurring in the underground cable 10A, and sends the determination result to the server. (step S122).

Next, partial discharge detection device 500 waits for a new timing according to generation cycle T1 (NO in step S104).

In the partial discharge detection device 500 according to the embodiment of the present disclosure, the generation unit 250 in the processing unit 200 performs Although it is described that the data Dt indicating the correspondence between the phase Φ and the charge amount Q is generated, the present invention is not limited to this. The generation unit 250 may be configured to generate data Dt indicating the correspondence relationship between the phase Φ and the charge amount Q in each cycle of the AC voltage of the commercial AC power.

Also, in the partial discharge detection device 500 according to the embodiment of the present disclosure, the discharge detection unit 260 in the processing unit 200 is configured to perform the data Dt extraction process, but the configuration is not limited to this. The discharge detection unit 260 may be configured not to perform the data Dt extraction process.

Further, in the partial discharge detection device 500 according to the embodiment of the present disclosure, the discharge detection unit 260 in the processing unit 200 generates the section data Dts, and calculates the charge amount Q based on the autocorrelation of the generated section data Dts. As the periodicity, the periodicity of the sum Qsum is determined, but the present invention is not limited to this. The discharge detection unit 260 may be configured to determine the periodicity of the charge amount Q based on the autocorrelation of the data Dtr without generating the section data Dts.

Further, in the partial discharge detection device 500 according to the embodiment of the present disclosure, the discharge detection unit 260 in the processing unit 200 has a phase difference of 30° so that the phase difference of 180° of the total sum Qsum for each phase interval Φs can be determined. Although the configuration is such that the section data Dts in which the phase range is set is described, the configuration is not limited to this. Discharge detection section 260 may be configured to generate section data Dts in which any phase range other than 30° is set.

Further, in the partial discharge detection device 500 according to the embodiment of the present disclosure, the discharge detection unit 260 in the processing unit 200 indicates the correspondence relationship between the interval data Dts and the shift interval data Dts and the correlation coefficient r(n). Although the correlation data R is generated and the periodicity of the sum Qsum is determined based on the generated correlation data R, the present invention is not limited to this. Discharge detection unit 260 is configured to determine the periodicity of sum Qsum by analyzing section data Dts using, for example, a machine learning method without using shift section data Dts and correlation data R. good too.

In addition, in the partial discharge detection device 500 according to the embodiment of the present disclosure, the filter processing section 210 in the processing section 200 is configured to have three BPFs 212, but the configuration is not limited to this. The filter processing unit 210 may be configured to have two or less BPFs 212 or may be configured to have four or more BPFs 212 . Also, the filter processing unit 210 may be configured to have a high-pass filter instead of the analog switch 211 and the BPF 212 .

Moreover, although the processing unit 200 in the partial discharge detection device 500 according to the embodiment of the present disclosure is configured to include the discharge detection unit 260, the configuration is not limited to this. The processing unit 200 may be configured without the discharge detection unit 260 . In this case, the processing section 200 has a display processing section instead of the discharge detection section 260 . Similar to the discharge detection unit 260, the display processing unit generates data Dtr and performs processing for displaying the generated data Dtr on a display device (not shown).

For example, as shown in FIG. 28, the display processing unit performs processing for displaying a polar coordinate system that indicates the correspondence relationship between the phase Φ and the frequency N in the generated data Dt. The display processing unit may be configured to display a polar coordinate system indicating the correspondence relationship between the phase Φ and the charge amount Q in the data Dt, or the phase Φ and the charge amount Q in the data Dt and the frequency The configuration may be such that a process of displaying a polar coordinate system indicating a correspondence relationship with the product of N is performed. Further, the display processing unit may be configured to display a two-dimensional orthogonal coordinate system including the data Dtr, as shown in FIG. may be scaled and represented by plot shading or color. Further, the display processing unit displays a three-dimensional orthogonal coordinate system having the X-axis as the phase Φ, the Y-axis as the charge amount Q, and the Z-axis as the frequency N, and including the data Dtr. It may be configured to perform a process of performing.

The user of the partial discharge detection device 500 refers to the data Dtr displayed on the display device to determine the periodicity of the charge amount Q in the data Dtr, and based on the determination result, the partial discharge in the underground cable 10A is detected. determine whether it has occurred.

By the way, a technology capable of detecting partial discharge in a cable with simple processing and configuration is desired. More specifically, a technique for detecting partial discharge in a cable using AI is conventionally known. However, when partial discharge is detected using AI, a huge amount of teacher data for machine learning is required in order to accurately detect partial discharge. In addition, if partial discharge is to be accurately detected in consideration of changes in the pattern indicating the relationship between the phase Φ and the charge amount Q depending on the time of the year such as the season, an even greater amount of teaching data is required.

In contrast, in the partial discharge detection device 500 of the present disclosure, the signal detection section 100 or 100A detects current flowing through the shield layer 75 . The generation unit 250 generates data Dt indicating the correspondence relationship between the phase Φ of the current detected by the signal detection unit 100 or 100A with respect to the AC voltage of the commercial AC power and the charge amount Q of the current. The discharge detection unit 260 determines the periodicity of the charge amount Q in the data Dt generated by the generation unit 250, and detects partial discharge based on the determination result.

The charge amount Q of the current flowing through the shield layer 75 corresponds to the charge amount of the partial discharge. With the configuration that detects partial discharge based on the determination result of the periodicity of the charge amount Q, partial discharge in the cable can be detected with simple processing and configuration compared to the configuration that detects partial discharge using AI, for example. can.

The above-described embodiments should be considered as illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

Each process (each function) of the above-described embodiments is realized by a processing circuit (Circuitry) including one or more processors. The processing circuit may be configured by an integrated circuit or the like in which one or more memories, various analog circuits, and various digital circuits are combined in addition to the one or more processors. The one or more memories store programs (instructions) that cause the one or more processors to execute the processes. The one or more processors may execute the above processes according to the program read from the one or more memories, or execute the above processes according to a logic circuit designed in advance to execute the above processes. may be executed. The processor includes a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), and an ASIC (Application Specific Integrated Control), which is compatible with various computers such as processor. Note that the plurality of physically separated processors may cooperate with each other to execute the above processes. For example, the processors installed in each of a plurality of physically separated computers cooperate with each other via a network such as a LAN (Local Area Network), a WAN (Wide Area Network), and the Internet to perform the above processes. may be executed. The program may be installed in the memory from an external server device or the like via the network, and may be stored in CD-ROM (Compact Disc Read Only Memory), DVD-ROM (Digital Versatile Disk Read Only Memory), and semiconductor It may be distributed in a state stored in a recording medium such as an essential memory, and installed in the memory from the recording medium.

The above description includes the features appended below.
[Appendix 1]
A partial discharge detection device for detecting partial discharge in a cable having a linear conductor that transmits commercial AC power, an insulating layer that surrounds the conductor, and a shielding layer that is a conductor that surrounds the insulating layer. hand,
a current detection unit that detects a current flowing through the shielding layer;
a generation unit that generates data indicating a correspondence relationship between a phase of the current detected by the current detection unit with respect to the AC voltage of the commercial AC power and a charge amount of the current;
a discharge detection unit that determines the periodicity of the charge amount in the data generated by the generation unit and detects the partial discharge based on the determination result;
The discharge detection unit compares the data with reference data based on the data generated in the past by the generation unit, and tentatively determines whether the partial discharge has occurred based on the comparison result. ,
The partial discharge detection device, wherein the discharge detection unit determines whether or not the partial discharge is occurring based on the result of the provisional determination and the result of the determination.

10, 10A, 10A1, 10A2, 10B, 10B1, 10B2, 10C, 10C1, 10C2 Underground cable 11, 11A, 11B, 11C Cable terminal 12 Cable 13, 15 Grounding node 14 Grounding cable 31 Manhole 41, 41A, 41B Normal Connections 42, 42A, 42B Insulation connection 43, 43A, 43B Ground connection 53 Conductive cable 71 Conductor 72 Internal semiconducting layer 73 Insulator 74 External semiconducting layer 75 Shielding layer 76 Sheath 77 Insulating tube 81 Terminal 100, 100A Signal Detector 110 CT
120, 120A signal output section 101 ring core 102 winding 105, 106 metal foil electrode 200 processing section 210 filter processing section 211 analog switch 212, 212A, 212B, 212C BPF
220 amplifier 230 ADC
250 generation unit 260 discharge detection unit 280 storage unit 500, 500A, 500B, 500C, 510 partial discharge detection device 501 partial discharge detection system 502 power transmission system

Claims (13)

A partial discharge detection device for detecting partial discharge in a cable having a linear conductor that transmits commercial AC power, an insulating layer that surrounds the conductor, and a shielding layer that is a conductor that surrounds the insulating layer. hand,
a current detection unit that detects a current flowing through the shielding layer;
a generation unit that generates data indicating a correspondence relationship between a phase of the current detected by the current detection unit with respect to the AC voltage of the commercial AC power and a charge amount of the current;
A partial discharge detection device, comprising: a discharge detection unit that determines the periodicity of the amount of charge in the data generated by the generation unit, and detects the partial discharge based on the determination result. The generation unit generates multi-cycle data, which is the data indicating the correspondence relationship between the phase and the charge amount in each of a plurality of cycles of the AC voltage,
2. The partial discharge detection device according to claim 1, wherein said discharge detection unit determines the periodicity of said charge amount using a statistic value of said charge amount for each phase in said plurality of period data. The discharge detection unit extracts a portion of the multiple-cycle data using a threshold value set based on the statistical value, and determines the periodicity of the charge amount in the extracted multiple-cycle data. The partial discharge detection device according to claim 2. 4. The partial discharge detection device according to claim 3, wherein said discharge detection unit determines periodicity of said amount of charge of said current determined to deviate from a steady state of said current based on said statistical value. The partial discharge detection device further comprises
Based on the multiple-cycle data, a maximum charge amount that is the maximum value of the charge amount in each phase section in which one cycle of the AC voltage is divided at predetermined intervals is specified, and the minimum of the specified maximum charge amounts is specified. A determination unit that determines the value as a threshold,
The discharge detection unit extracts a portion of the multiple-cycle data using the threshold value determined by the determination unit, and determines the periodicity of the charge amount in the extracted multiple-cycle data. Item 3. The partial discharge detection device according to item 2. The generation unit generates the data at a generation timing according to a predetermined generation cycle,
When the number of pairs of the phase and the charge amount included in the first data extracted from the data generated at the first generation timing is less than a predetermined value, the discharge detection unit extracts The periodicity of the charge amount is determined based on the first data and the second data extracted from the data generated at the second generation timing different from the first generation timing. The partial discharge detection device according to any one of claims 1 to 5. The partial discharge detection device according to any one of claims 1 to 5, wherein the discharge detection unit obtains the detection result of the partial discharge by providing the data to a learning model. 6. The portion according to any one of claims 1 to 5, wherein the discharge detection unit determines the periodicity of the charge amount based on a correlation between the data and the phase-shifted data. Discharge detection device. The discharge detection unit calculates the sum of the amount of charge in each of a plurality of intervals obtained by dividing one cycle of the AC voltage into a plurality of phase ranges, and calculates the sum of the amount of charge in each of the intervals as the periodicity of the amount of charge. 6. The partial discharge detection device according to any one of claims 1 to 5, wherein the periodicity of summation is determined. 10. The partial discharge detection device according to claim 9, wherein said phase range is set such that a phase difference of 180[deg.] of said sum for each section can be discriminated. The generation unit generates polarity information indicating the polarity of the charge amount,
The partial discharge detection device according to any one of claims 1 to 5, wherein the discharge detection section detects the partial discharge further based on the polarity information generated by the generation section. The partial discharge detection device further comprises
a plurality of bandpass filters having different passbands for receiving signals based on the current detected by the current detection unit;
The discharge detection unit selects one of the plurality of bandpass filters based on the data generated by the generation unit,
The partial discharge detection device according to any one of claims 1 to 5, wherein the generation section generates the data based on the output signal of the bandpass filter selected by the discharge detection section. A partial discharge detection method for detecting partial discharge in a cable having a linear conductor that transmits commercial AC power, an insulating layer that surrounds the conductor, and a shielding layer that is a conductor that surrounds the insulating layer. hand,
detecting a current flowing through the shielding layer;
generating data indicating a correspondence relationship between a phase of the detected current with respect to the AC voltage of the commercial AC power and a charge amount of the current;
and determining the periodicity of the charge amount in the generated data, and detecting the partial discharge based on the determination result.

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