Cable monitoring device, management device, cable monitoring system, and cable monitoring method

Abstract

The present invention is a cable monitoring device that monitors an underground cable having a line-shaped conductor that transmits power, an insulation layer that covers the periphery of the conductor, and a shielding layer that is a conductor that covers the periphery of the insulation layer, the cable monitoring device comprising: a signal detection unit that outputs an output signal corresponding to changes in the current flowing through the shielding layer, or to changes in the potential of the shielding layer; and an irregularity detection unit that detects partial discharge and insulation breakage in the underground cable on the basis of the output signal outputted from the signal detection unit.

Description

Technical Field

[0001] The present disclosure relates to a cable monitoring device, a management device, a cable monitoring system, and a cable monitoring method. This application claims priority based on Japanese Patent Application No. 2021-21530 filed on February 15, 2021, and incorporates all of its disclosures herein.

Background Art

[0002] Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2013-217870) discloses an accident point calibration device as follows. That is, the accident point calibration device is disposed so as to surround the inside of each terminal portion of the underground cable constituting the section, and a ground wire having one end connected to the terminal portion of the underground cable and the other end grounded is passed through. A plurality of opto-current sensors that detect and output the current generated at the accident point, and a commercial frequency component detection unit that extracts and outputs the accident current in the commercial frequency band by a low-pass filter from the output signals of the respective opto-current sensors input via an optical fiber transmission line. The accident section detection unit that detects the accident section based on a plurality of cycles of accident current extracted from the output signals of the opto-current sensors disposed inside both terminal portions of each section, and a high-pass filter from the output signals of the respective opto-current sensors input via the optical fiber transmission line. A surge current component detection unit that extracts and outputs a surge current having a frequency higher than the commercial frequency band, and based on the surge current extracted from the output signals of the opto-current sensors disposed inside both terminal portions of each section, the surge current component detection unit calculates the time difference when the surge current reaches each opto-current sensor, and an accident point calibration unit that calibrates the accident point distance, which is accident point information. An accident point detection unit is provided.

[0003] In addition, Patent Document 2 (International Publication No. 2016 / 079869) discloses a partial discharge position calibration device as follows. That is, the partial discharge position calibration device is a partial discharge position calibration device capable of calibrating the position of a partial discharge generated inside a gas-insulated device to which a power cable is connected or inside the power cable, and is attached to the gas-insulated device and capable of detecting a partial discharge signal. a first sensor, a second sensor attached to the power cable and capable of detecting the partial discharge signal, a time difference detection unit that detects a time difference that is the difference between the detection time of the partial discharge signal by the first sensor and the detection time of the partial discharge signal by the second sensor, and the time difference detected by the time difference detection unit, the propagation speed of the partial discharge signal in the gas-insulated device, and the propagation speed of the partial discharge signal in the power cable And a processing unit that calibrates the occurrence position of the partial discharge based on the above.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Means for Solving the Problems

[0005] The cable monitoring device of the present disclosure is a cable monitoring device that monitors a cable having a linear conductor that transmits power, an insulating layer that covers the periphery of the conductor, and a shielding layer that is a conductor that covers the periphery of the insulating layer, and passes through the shielding layer. a signal detection unit that outputs an output signal according to a change in current or a change in the potential of the shielding layer; and an abnormality detection unit that detects partial discharge and insulation breakdown in the cable based on the output signal output from the signal detection unit.

[0006] The management device of the present disclosure includes a plurality of cable monitoring devices installed at different positions for monitoring a cable having a linear conductor for transmitting power, an insulating layer covering the periphery of the conductor, and a shielding layer which is a conductor covering the periphery of the insulating layer. The management device includes an acquisition unit that acquires a plurality of first detection information respectively indicating the times when the plurality of cable monitoring devices detect partial discharge in the cable, and a plurality of second detection information respectively indicating the times when the plurality of cable monitoring devices detect insulation breakdown in the cable, a first calculation unit that calculates the occurrence position of the partial discharge in the cable based on each of the first detection information acquired by the acquisition unit, and a second calculation unit that calculates the occurrence position of the insulation breakdown in the cable based on each of the second detection information acquired by the acquisition unit.

[0007] The cable monitoring system of the present disclosure includes a plurality of cable monitoring devices installed at different positions for monitoring a cable having a linear conductor for transmitting power, an insulating layer covering the periphery of the conductor, and a shielding layer which is a conductor covering the periphery of the insulating layer, a management device that acquires a plurality of first detection information respectively indicating the times when the plurality of cable monitoring devices detect partial discharge in the cable, and a plurality of second detection information respectively indicating the times when the plurality of cable monitoring devices detect insulation breakdown in the cable. The management device calculates the occurrence position of the partial discharge in the cable based on each of the acquired first detection information, and calculates the occurrence position of the insulation breakdown in the cable based on each of the acquired second detection information.

[0008] The cable monitoring method of the present disclosure is a cable monitoring method in a cable monitoring system including a plurality of cable monitoring devices installed at different positions and a management device. The method includes steps of: the plurality of cable monitoring devices monitoring a cable having a linear conductor for transmitting power, an insulating layer covering the periphery of the conductor, and a shielding layer which is a conductor covering the periphery of the insulating layer; the management device obtaining a plurality of first detection information respectively indicating the times when the plurality of cable monitoring devices detect partial discharge in the cable; the management device obtaining a plurality of second detection information respectively indicating the times when the plurality of cable monitoring devices detect insulation breakdown in the cable; the management device calculating the occurrence position of the partial discharge in the cable based on each of the obtained first detection information; and the management device calculating the occurrence position of the insulation breakdown in the cable based on each of the obtained second detection information.

[0009] One aspect of the present disclosure can be realized not only as a cable monitoring device including such a characteristic processing unit, but also as a semiconductor integrated circuit realizing part or all of the cable monitoring device, as a method taking the processing in the cable monitoring device as steps, or as a program for causing a computer to execute the steps of the processing in the cable monitoring device. Further, one aspect of the present disclosure can be realized not only as a management device including such a characteristic processing unit, but also as a semiconductor integrated circuit realizing part or all of the management device, as a method taking the processing in the management device as steps, or as a program for causing a computer to execute the steps of the processing in the management device. Further, one aspect of the present disclosure can be realized not only as a cable monitoring system including such a characteristic processing unit, but also as a semiconductor integrated circuit realizing part or all of the cable monitoring system, or as a program for causing a computer to execute the steps of the processing in the cable monitoring system.

Brief Description of Drawings

[0010]

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[0011] Conventionally, techniques for monitoring cables and detecting abnormalities in cables have been proposed.

[0012] [Problems to be Solved by the Present Disclosure] In the technique described in Patent Document 1, partial discharge in a cable cannot be detected. Further, in the technique described in Patent Document 2, insulation breakdown in a cable cannot be detected.

[0013] A technique capable of realizing an excellent function for detecting partial discharge and insulation breakdown in a cable beyond the techniques described in Patent Documents 1 and 2 is desired.

[0014] The present disclosure has been made to solve the above-described problems, and an object thereof is to provide a cable monitoring device, a management device, a cable monitoring system, and a cable monitoring method capable of realizing an excellent function related to detection of partial discharge and insulation breakdown in a cable.

[0015] [Effects of the Present Disclosure] According to the present disclosure, an excellent function for detecting partial discharge and insulation breakdown in a cable can be realized.

[0016] [Description of Embodiments of the Present Disclosure] First, the content of the embodiments of the present disclosure will be listed and described.

[0017] (1) A cable monitoring device according to an embodiment of the present disclosure monitors a cable having a linear conductor for transmitting power, an insulating layer covering the periphery of the conductor, and a shielding layer that is a conductor covering the periphery of the insulating layer, and includes a signal detection unit that outputs an output signal according to a change in current flowing through the shielding layer or a change in the potential of the shielding layer, and an abnormality detection unit that detects partial discharge and insulation breakdown in the cable based on the output signal output from the signal detection unit.

[0018] In this way, by detecting both partial discharge and insulation breakdown in a cable based on a common output signal output from a common signal detection unit, partial discharge and insulation breakdown in the cable can be detected with a simple configuration. Therefore, an excellent function for detecting partial discharge and insulation breakdown in a cable can be realized.

[0019] (2) The abnormality detection unit may discriminate between the partial discharge and the insulation breakdown based on a comparison result between the level of the output signal and a predetermined threshold value.

[0020] With such a configuration, by paying attention to the difference in the levels of the output signal output from the signal detection unit when insulation breakdown occurs and the output signal output from the signal detection unit when partial discharge occurs, insulation breakdown and partial discharge can be more easily discriminated.

[0021] (3) The abnormality detection unit may discriminate between the partial discharge and the insulation breakdown based on the waveform of the output signal.

[0022] With such a configuration, by focusing on the difference in waveforms between the output signal output from the signal detection unit when an insulation breakdown occurs and the output signal output from the signal detection unit when a partial discharge occurs, it is possible to more accurately discriminate between an insulation breakdown and a partial discharge.

[0023] (4) The abnormality detection unit may detect the partial discharge based on the output signal that has passed through a high-pass filter that attenuates components below a predetermined frequency, and may detect the insulation breakdown based on the output signal before passing through the high-pass filter.

[0024] With such a configuration, it is possible to detect a partial discharge by removing low-frequency noise using a high-pass filter, and it is also possible to detect an insulation breakdown by extracting more low-frequency components caused by the insulation breakdown.

[0025] (5) The cable monitoring device may further be configured to include a notification unit that notifies other devices of the time when the abnormality detection unit detects the partial discharge.

[0026] With such a configuration, in other devices, it is possible to locate the occurrence position of the partial discharge in the cable by using the detection times of the partial discharges in a plurality of cable monitoring devices.

[0027] (6) The cable monitoring device may further be configured to include a notification unit that notifies other devices of the time when the abnormality detection unit detects the insulation breakdown.

[0028] With such a configuration, in other devices, it is possible to locate the occurrence position of the insulation breakdown in the cable by using the detection times of the insulation breakdowns in a plurality of cable monitoring devices.

[0029] (7) The cable monitoring device may further be configured to include a synchronization unit that performs processing for time synchronization with other cable monitoring devices that monitor the same cable through communication with the other cable monitoring devices.

[0030] With such a configuration, time synchronization of a plurality of cable monitoring devices can be achieved with a simple configuration, so that the occurrence positions of partial discharges and the occurrence positions of insulation breakdowns in the cable can be calibrated with a simple configuration.

[0031] (8) The management device according to an embodiment of the present disclosure monitors a cable having a linear conductor for transmitting power, an insulating layer covering the periphery of the conductor, and a shielding layer that is a conductor covering the periphery of the insulating layer. A plurality of first detection information respectively indicating the times when a plurality of cable monitoring devices installed at different positions detect partial discharges in the cable, and a plurality of second detection information respectively indicating the times when the plurality of cable monitoring devices detect insulation breakdowns in the cable. An acquisition unit that acquires the information, a first calculation unit that calculates the occurrence position of the partial discharge in the cable based on each of the first detection information acquired by the acquisition unit, and a second calculation unit that calculates the occurrence position of the insulation breakdown in the cable based on each of the second detection information acquired by the acquisition unit.

[0032] In this way, based on the detection times of partial discharges in a plurality of cable monitoring devices capable of detecting both partial discharges and insulation breakdowns, the occurrence position of the partial discharge is calculated, and based on the detection times of insulation breakdowns in the plurality of cable monitoring devices, the occurrence position of the insulation breakdown is calculated. With this configuration, both the occurrence position of the partial discharge and the occurrence position of the insulation breakdown can be calibrated with a simple system configuration. Therefore, an excellent function regarding the detection of partial discharges and insulation breakdowns in the cable can be realized.

[0033] (9) The cable monitoring system according to an embodiment of the present disclosure monitors a cable having a linear conductor for transmitting power, an insulating layer covering the periphery of the conductor, and a shielding layer that is a conductor covering the periphery of the insulating layer, and includes a plurality of cable monitoring devices installed at different positions, a plurality of first detection information respectively indicating the times when the plurality of cable monitoring devices detect partial discharge in the cable, and a plurality of second detection information respectively indicating the times when the plurality of cable monitoring devices detect insulation breakdown in the cable. The management device calculates the occurrence position of the partial discharge in the cable based on each of the acquired first detection information, and calculates the occurrence position of the insulation breakdown in the cable based on each of the acquired second detection information.

[0034] In this way, based on the detection times of partial discharge in a plurality of cable monitoring devices capable of detecting both partial discharge and insulation breakdown, the occurrence position of the partial discharge is calculated, and based on the detection times of insulation breakdown in the plurality of cable monitoring devices, the occurrence position of the insulation breakdown is calculated. With this configuration, both the occurrence position of the partial discharge and the occurrence position of the insulation breakdown can be calibrated with a simple configuration. Therefore, an excellent function regarding the detection of partial discharge and insulation breakdown in the cable can be realized.

[0035] (10) The cable monitoring method according to an embodiment of the present disclosure is a cable monitoring method in a cable monitoring system including a plurality of cable monitoring devices installed at different positions and a management device. The method includes: a step in which the plurality of cable monitoring devices monitor a cable having a linear conductor for transmitting power, an insulating layer covering the periphery of the conductor, and a shielding layer that is a conductor covering the periphery of the insulating layer; a step in which the management device acquires a plurality of first detection information respectively indicating the times when the plurality of cable monitoring devices detect partial discharge in the cable; a step in which the management device acquires a plurality of second detection information respectively indicating the times when the plurality of cable monitoring devices detect insulation breakdown in the cable; a step in which the management device calculates the occurrence position of the partial discharge in the cable based on each of the acquired first detection information; and a step in which the management device calculates the occurrence position of the insulation breakdown in the cable based on each of the acquired second detection information.

[0036] In this way, by calculating the occurrence position of partial discharge based on the detection time of partial discharge in a plurality of cable monitoring devices capable of detecting both partial discharge and insulation breakdown, and calculating the occurrence position of insulation breakdown based on the detection time of insulation breakdown in the plurality of cable monitoring devices, it is possible to demarcate both the occurrence position of partial discharge and the occurrence position of insulation breakdown in a simple manner. Therefore, an excellent function regarding the detection of partial discharge and insulation breakdown in a cable can be realized.

[0037] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and their description will not be repeated. Also, at least a part of the embodiments described below may be arbitrarily combined.

[0038] [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, the power transmission system 502 includes underground cables 10A, 10B, 10C, normal connection parts 41A, 41B, insulating connection parts 42A, 42B, 42C, and above-ground connection parts 43A, 43B. Hereinafter, each of the underground cables 10A, 10B, 10C is also referred to as the underground cable 10, each of the normal connection parts 41A, 41B is also referred to as the normal connection part 41, each of the insulating connection parts 42A, 42B, 42C is also referred to as the insulating connection part 42, and each of the above-ground connection parts 43A, 43B is also referred to as the above-ground connection part 43. At least a part of the power transmission system 502 is provided, for example, in the underground part of the power grid.

[0039] The above-ground connection part 43 includes cable terminals 11A, 11B, 11C. The underground cable 10 is connected to the cable terminals 11A, 11B, 11C at the above-ground connection part 43. More specifically, the underground cable 10A is connected to the cable terminal 11A, the underground cable 10B is connected to the cable terminal 11B, and the underground cable 10C is connected to the cable terminal 11C.

[0040] The above-ground connection part 43 is provided, for example, in a substation at a portion where the underground cable 10 appears on the ground. The normal connection part 41 and the insulating connection part 42 are provided inside the manhole 31.

[0041] FIG. 2 is a diagram showing an example of the 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 the underground cable 10. Referring to FIG. 2, the underground cable 10 includes, in order from the center, a linear conductor 71 that transmits power, an inner semiconductive layer 72 made of semiconductive ethylene propylene (EP) rubber, an insulator 73 made of EP rubber as an insulating layer, an outer semiconductive layer 74 that is a semiconductive tape, a conductive shielding layer 75, and a vinyl sheath 76. That is, the inner semiconductive layer 72 covers the periphery of the conductor 71, the insulator 73 covers the periphery of the inner semiconductive layer 72, the outer semiconductive layer 74 covers the periphery of the insulator 73, the shielding layer 75 as a conductor covers the periphery of the outer semiconductive layer 74, and the sheath 76 covers the periphery of the shielding layer 75.

[0042] In the underground cable 10, the conductor 71 is used for power transmission and a high-voltage is applied thereto. The shielding layer 75 is conductive while being grounded in the middle of the underground cable 10. Therefore, the voltage of the shielding layer 75 is lower than that of the conductor 71.

[0043] In the power transmission system 502, as an example, a three-phase three-wire system is used as the power distribution method. In the power transmission system 502, as three-phase underground cables 10, underground cables 10A, 10B, and 10C are provided.

[0044] Referring to FIG. 1 again, at the cable terminals 11A, 11B, and 11C, the shielding layers 75 of the respective underground cables 10A, 10B, and 10C are exposed. Terminals are provided at the exposed portions of these shielding layers 75, respectively.

[0045] The underground cables 10A, 10B, and 10C are respectively connected to the ground node 15 at the cable terminals 11A, 11B, and 11C. More specifically, the terminals provided in each of the underground cables 10A, 10B, and 10C are connected to the ground node 15 via a grounding cable 14 or the like, whereby the shielding layers 75 of the respective underground cables 10 are grounded.

[0046] For example, the underground cable 10 is composed of a plurality of cables whose ends are connected to each other at the normal connection portion 41 and the insulated connection portion 42.

[0047] FIG. 3 is a diagram showing an example of a method of connecting an underground cable in a normal connection portion used in a power transmission system according to an embodiment of the present disclosure. In FIG. 3, for ease of explanation, mainly the conductor 71 and the shielding layer 75 of the underground cable 10A are shown. The content described below is the same for the underground cable 10B and the underground cable 10C.

[0048] Referring to FIG. 3, in the normal connection portion 41, the underground cables 10A1 and 10A2 are connected. In the normal connection portion 41, for example, the shielding layers 75 of the underground cables 10A1 and 10A2 are exposed at the connection portion between the conductors 71 of the underground cables 10A1 and 10A2. In the normal 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, for example, a conductive wire 12.

[0049] And when the shielding layer 75 of the underground cable 10A1 and the shielding layer 75 of the underground cable 10A2 are connected, for example, a terminal 81 is provided at the exposed portion of the shielding layer 75 of the underground cable 10A2. Note that the terminal 81 may be provided at the exposed portion of the shielding layer 75 of the underground cable 10A1. And when the terminal 81 is connected to the ground node 13 via a cable or the like, the shielding layer 75 of the underground cable 10A is grounded.

[0050] FIG. 4 is a diagram showing an example of a method for connecting an underground cable in an insulating connection portion used in a power transmission system according to an embodiment of the present disclosure. In FIG. 4, for ease of explanation, mainly the conductor 71 and the shielding layer 75 in the configuration of the underground cable 10A are shown. The content described below is the same for the underground cable 10B and the underground cable 10C.

[0051] Referring to FIG. 4, in the insulating connection portion 42, the underground cables 10A1 and 10A2 are connected. In the insulating connection portion 42, for example, the shielding layers 75 of the underground cables 10A1 and 10A2 are exposed at the connection portion between the conductors 71 of the underground cables 10A1 and 10A2, and terminals 81 and the like are respectively provided at the exposed portions.

[0052] In the insulating connection portion 42, when the conductor 71 of the underground cable 10A1 and the conductor 71 of the underground cable 10A2 are connected, for example, the terminal 81 in the underground cable 10A1 and the terminal 81 in the underground cable 10A2 are connected using a wire 12, so that the shielding layer 75 of the underground cable 10A1 and the shielding layer 75 of the underground cable 10A2 are connected.

[0053] FIG. 5 is a diagram showing another example of a method for connecting underground cables in an insulating connection part used in a power transmission system according to an embodiment of the present disclosure. Referring to FIG. 5, in the insulating connection part 42, underground cables 10A1 and 10A2 are connected, underground cables 10B1 and 10B2 are connected, and underground cables 10C1 and 10C2 are connected. In the insulating connection part 42, for example, the shielding layers 75 of the underground cables 10A1 and 10A2 are exposed at the connection part between the conductors 71 of the underground cables 10A1 and 10A2, the shielding layers 75 of the underground cables 10B1 and 10B2 are exposed at the connection part between the conductors 71 of the underground cables 10B1 and 10B2, the shielding layers 75 of the underground cables 10C1 and 10C2 are exposed at the connection part between the conductors 71 of the underground cables 10C1 and 10C2, and terminals 81 and the like are respectively provided at the exposed parts.

[0054] In the insulating connection part 42, for example, by connecting the terminal 81 in the underground cable 10A1 and the terminal 81 in the underground cable 10B2 using the wire 12, the shielding layer 75 of the underground cable 10A1 and the shielding layer 75 of the underground cable 10B2 are connected. By connecting the terminal 81 in the underground cable 10B1 and the terminal 81 in the underground cable 10C2 using the wire 12, the shielding layer 75 of the underground cable 10B1 and the shielding layer 75 of the underground cable 10C2 are connected. By connecting the terminal 81 in the underground cable 10C1 and the terminal 81 in the underground cable 10A2 using the wire 12, the shielding layer 75 of the underground cable 10C1 and the shielding layer 75 of the underground cable 10A2 are connected.

[0055] Thus, in the power transmission system 502, in the insulating connection part 42, the underground cables 10 may be cross-bond connected.

[0056] [Cable Monitoring System] FIG. 6 is a diagram showing the configuration of the cable monitoring system according to an embodiment of the present disclosure. In FIG. 6, for ease of explanation, mainly the underground cable 10A among the underground cables 10 is shown. The content described below is the same for the underground cable 10B and the underground cable 10C.

[0057] Referring to FIG. 6, the cable monitoring system 501 includes cable monitoring devices 500A, 500B, 500C, 500D and a management device 400. Hereinafter, each of the cable monitoring devices 500A, 500B, 500C, 500D is also referred to as a cable monitoring device 500. The cable monitoring system 501 is used in the power transmission system 502.

[0058] The cable monitoring devices 500 are installed at different positions. The cable monitoring devices 500 are provided corresponding to, for example, the insulation connection part 42 and the above-ground connection part 43. In the example shown in FIG. 6, the cable monitoring device 500A is provided corresponding to the insulation connection part 42A, the cable monitoring device 500B is provided corresponding to the insulation connection part 42B, the cable monitoring device 500C is provided corresponding to the insulation connection part 42C, and the cable monitoring device 500D is provided corresponding to the above-ground connection part 43A. Also, the management device 400 is connected to the cable monitoring device 500D.

[0059] The cable monitoring device 500 monitors the underground cable 10A, which is an example of the cable to be monitored. More specifically, the four cable monitoring devices 500 monitor the underground cable 10A in the vicinity of the installation position. The cable monitoring device 500 detects partial discharge and insulation breakdown in the underground cable 10A by monitoring the underground cable 10A. Note that the monitoring target of the cable monitoring device 500 is not limited to the underground cable, and may be a cable provided in a place other than underground.

[0060] The cable monitoring device 500 can communicate with each other via the underground cable 10A by inductive coupling with the shielding layer 75 in the underground cable 10A. The cable monitoring device 500 can perform communication up to a distance of several kilometers at a variable transmission speed of 20 kbps to 130 kbps, for example, using low-frequency PLC (Power Line Communication) used for communication such as smart meters. Alternatively, the cable monitoring device 500 can perform shorter-distance communication at a transmission speed of up to 200 Mbps using high-frequency PLC.

[0061] For example, the cable monitoring device 500 notifies the management device 400 of the detection result of partial discharge in the underground cable 10A. Also, for example, the cable monitoring device 500 notifies the management device 400 of the detection result of insulation breakdown in the underground cable 10A. The cable monitoring device 500 can relay the notification of the detection result from another cable monitoring device 500 to another cable monitoring device 500 or the management device 400. For example, the cable monitoring devices 500A, 500B, and 500C notify the management device 400 of the detection result via another cable monitoring device 500 including the cable monitoring device 500D. Also, for example, the cable monitoring device 500D directly notifies the management device 400 of the detection result.

[0062] Based on the detection result of partial discharge notified by the cable monitoring device 500, the management device 400 calculates the occurrence position of partial discharge in the underground cable 10A, that is, calibrates the occurrence position of partial discharge. Also, based on the detection result of insulation breakdown notified by the cable monitoring device 500, the management device 400 calculates the occurrence position of insulation breakdown in the underground cable 10A, that is, calibrates the occurrence position of insulation breakdown.

[0063] 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 through the power coil. Thereby, the power coil can extract current. The cable monitoring device 500 operates, for example, by the power obtained by the power coil.

[0064] [Cable Monitoring Device] FIG. 7 is a diagram showing the configuration of a cable monitoring device according to an embodiment of the present disclosure. Referring to FIG. 7, the cable monitoring device 500 includes a signal detection unit 100, an abnormality detection unit 200, an electromagnetic coupling unit 300, a communication unit 331, a synchronization unit 332, and a counter 333. The communication unit 331 is an example of a notification unit. The signal detection unit 100 includes a current transformer 110 and a signal output unit 120. The electromagnetic coupling unit 300 includes a current transformer 310 and a signal input / output unit 320. Hereinafter, the current transformer 110 is also referred to as CT110, and the current transformer 310 is also referred to as CT310.

[0065] The counter 333 counts, for example, clock pulses generated by an oscillation circuit using a crystal oscillator and holds time information indicating the counted value. This time information indicates, for example, the current time.

[0066] The signal detection unit 100 and the electromagnetic coupling unit 300 are electromagnetically coupled to the shielding layer 75 at, for example, the insulating connection part 42 which is the connection part of the underground cable 10A.

[0067] The signal detection unit 100 outputs an output signal corresponding to a change in the current flowing through the shielding layer 75 of the underground cable 10A. More specifically, the signal detection unit 100 outputs an output signal, which is an analog signal corresponding to the induced current of the current flowing through the shielding layer 75 of the underground cable 10, to the abnormality detection unit 200.

[0068] The abnormality detection unit 200 detects partial discharge and insulation breakdown in the underground cable 10A based on the output signal output from the signal detection unit 100. More specifically, the abnormality detection unit 200 performs a determination process of determining whether or not partial discharge and insulation breakdown have occurred in the underground cable 10A based on the output signal received from the signal detection unit 100. For example, when the abnormality detection unit 200 detects partial discharge in the underground cable 10A, the detection information DA including the detection time of the partial discharge and the ID of its own cable monitoring device 500 is output to the communication unit 331. Also, for example, when the abnormality detection unit 200 detects insulation breakdown in the underground cable 10A, the detection information DB including the detection time of the insulation breakdown and the ID of its own cable monitoring device 500 is output to the communication unit 331. The detection information DA is an example of the first detection information. The detection information DB is an example of the second detection information.

[0069] The communication unit 331 can transmit and receive communication information among other cable monitoring devices 500 by using the induced current flowing through the shielding layer 75 by electromagnetic coupling of the electromagnetic coupling unit 300. Also, the communication unit 331 in the cable monitoring device 500D is connected to the management device 400 via a communication line (not shown). The communication unit 331 in the cable monitoring device 500D relays the communication information received from other cable monitoring devices 500 to the management device 400 via the communication line. For example, the communication unit 331 in the cable monitoring device 500D is a master station in the PLC communication, and the communication units 331 in the cable monitoring devices 500A, 500B, 500C are slave stations in the PLC communication.

[0070] For example, when the abnormality detection unit 200 detects partial discharge, the communication unit 331 notifies other devices, for example, the management device 400, of the time at which the detection was made. Also, when the abnormality detection unit 200 detects insulation breakdown discharge, the communication unit 331 notifies other devices, for example, the management device 400, of the time at which the detection was made. More specifically, the communication unit 331 receives detection information DA from the abnormality detection unit 200, and transmits the received detection information DA to the management device 400 via the communication line or via other cable monitoring devices 500 including the cable monitoring device 500D and the communication line. Also, the communication unit 331 receives detection information DB from the abnormality detection unit 200, and transmits the received detection information DB to the management device 400 via the communication line or via other cable monitoring devices 500 including the cable monitoring device 500D and the communication line. The detection information DA and DB are examples of communication information.

[0071] <Signal detection unit and electromagnetic coupling unit> FIG. 8 is a diagram showing the configuration of the CT in the cable monitoring device according to an embodiment of the present disclosure. Referring to FIG. 8, the CT 110 includes a ring core 101 and a winding 102. The winding 102 is wound around the ring core 101. The winding 102 is connected to the signal output unit 120. The number of turns of the winding 102 in the ring core 101 is, for example, 3 to 7 turns.

[0072] CT110 is attached, for example, such that the conductive cable 53 penetrates the ring core 101. The conductive cable 53 is, for example, the wire 12 or the grounding cable 14. More specifically, referring again to FIGS. 4 and 6, the CT110 of the cable monitoring devices 500A, 500B, 500C at the insulation connection parts 42A, 42B, 42C is attached such that the wire 12 connecting the shielding layers 75 of the underground cable 10A1 and the underground cable 10A2 penetrates the ring core 101. Also, the CT110 of the cable monitoring device 500D at the above-ground connection part 43A is attached such that the grounding cable 14 penetrates the ring core 101. When current flows through the shielding layer 75 and the conductive cable 53, an induced current flows through the winding 102 by inductive coupling. The signal output part 120 outputs an output signal corresponding to the induced current flowing through the winding 102 to the abnormality detection part 200.

[0073] Also, CT310 includes a ring core 301 and a winding 302. The winding 302 is wound around the ring core 301. The winding 302 is connected to the signal input / output part 320. The number of turns of the winding 302 in the ring core 301 is, for example, 3 to 7 turns.

[0074] CT310 is attached, for example, such that the conductive cable 53 penetrates the ring core 301. More specifically, the CT310 of the cable monitoring devices 500A, 500B, 500C at the insulation connection parts 42A, 42B, 42C is attached such that the wire 12 connecting the shielding layers 75 of the underground cable 10A1 and the underground cable 10A2 penetrates the ring core 301. Also, the CT310 of the cable monitoring device 500D at the above-ground connection part 43A is attached such that the grounding cable 14 penetrates the ring core 301. Note that the sizes of CT110 and 310 may be the same or different.

[0075] The communication part 331 generates a transmission signal including communication information to be transmitted to another cable monitoring device 500 or the management device 400, and outputs the generated transmission signal to the electromagnetic coupling part 300.

[0076] The signal input / output unit 320 receives a transmission signal from the communication unit 331 and passes a current corresponding to the received transmission signal through the winding 302. When a current flows through the winding 302, an induced current flows through the conductive cable 53 and the shielding layer 75 by inductive coupling. Hereinafter, the induced current flowing through the shielding layer 75 when the signal input / output unit 320 passes a current through the winding 302 is also referred to as a communication induced current.

[0077] Also, when a communication induced current from another cable monitoring device 500 flows through the shielding layer 75 and the conductive cable 53, an induced current flows through the winding 102 by inductive coupling. The signal input / output unit 320 outputs a received signal, which is an analog signal corresponding to the induced current flowing through the winding 102, to the communication unit 331. The communication unit 331 acquires communication information from the other cable monitoring device 500 from the received signal received from the signal input / output unit 320.

[0078] For example, the band of the communication induced current used by the communication unit 331 for transmitting and receiving communication information is different from the band of the output signal used by the abnormality detection unit 200 for detecting partial discharge and insulation breakdown. Therefore, the communication unit 331 and the abnormality detection unit 200 can perform the transmission of communication information and the detection of partial discharge and insulation breakdown in parallel. Also, even when an insulation breakdown occurs in the underground cable 10A, the communication unit 331 can transmit communication information, for example, in a state where the shielding layer 75 is not completely cut.

[0079] FIG. 9 is a diagram showing the configuration of a cable monitoring device according to a modification of the embodiment of the present disclosure. Referring to FIG. 9, the cable monitoring device 510 includes a signal detection unit 100A, an abnormality detection unit 200, an electromagnetic coupling unit 300, a communication unit 331, a synchronization unit 332, and a counter 333. The cable monitoring system 501 may be configured to include the cable monitoring device 510 instead of the cable monitoring device 500.

[0080] The signal detection unit 100A outputs an output signal corresponding to a change in the potential of the shielding layer 75 of the underground cable 10. More specifically, the signal detection unit 100A includes metal foil electrodes 105 and 106, and a signal output unit 120A. The signal detection unit 100A is electrostatically coupled to the shielding layer 75, for example, at the insulation connection part 42 which is a connection part of the underground cable 10.

[0081] FIG. 10 is a diagram showing an example of attachment of the metal foil electrodes in the cable monitoring device according to the embodiment of the present disclosure. Referring to FIGS. 9 and 10, the metal foil electrodes 105 and 106 are connected to the signal output unit 120A.

[0082] The metal foil electrodes 105 and 106 are attached to the surface of the sheath 76 of the underground cable 10 on opposite sides via, for example, the insulating cylinder 77 in the insulation connection part 42. More specifically, for example, in the insulation connection part 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 10A2. Note that the metal foil electrodes 105 and 106 may be attached so as to cover the outer periphery of the sheath 76 of the underground cable 10A2. Also, the position where 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.

[0083] When the potentials of the shielding layer 75 and the conductive cable 53 change, a current flows through the metal foil electrodes 105 and 106 due to electric field coupling. The signal output unit 120A outputs an output signal, which is an analog signal corresponding to the change in the potential of the shielding layer 75 based on the current, to the abnormality detection unit 200.

[0084] <Synchronization unit> Referring again to FIGS. 7 and 9, the synchronization unit 332 performs a process for time synchronization with another cable monitoring device 500 by communicating with the other cable monitoring device 500 that monitors the underground cable 10A. More specifically, the synchronization unit 332 performs a synchronization process, which is a process for, for example, periodically matching the time information of the counter 333 with the other cable monitoring device 500.

[0085] For example, the cable monitoring device 500D functions as a master device. The synchronization unit 332 in the cable monitoring device 500D acquires the time information of the counter 333 at the synchronization processing timing according to a predetermined period, and outputs the acquired time information to the communication unit 331. The communication unit 331 in the cable monitoring device 500D receives the time information from the synchronization unit 332, and transmits the received time information to the cable monitoring device 500A. The time information is an example of communication information.

[0086] In the cable monitoring device 500A, the communication unit 331 receives the time information from the communication unit 331 in the cable monitoring device 500D via the electromagnetic coupling unit 300, and outputs the received time information to the synchronization unit 332. The synchronization unit 332 updates the time information of the counter 333 with the time information received from the communication unit 331. Further, the synchronization unit 332 acquires the updated time information of the counter 333, and outputs the acquired time information to the communication unit 331. The communication unit 331 receives the time information from the synchronization unit 332, and transmits the received time information to the cable monitoring devices 500D and 500B.

[0087] In the cable monitoring device 500B, the communication unit 331 receives the time information from the communication unit 331 in the cable monitoring device 500A via the electromagnetic coupling unit 300, and outputs the received time information to the synchronization unit 332. The synchronization unit 332 updates the time information of the counter 333 with the time information received from the communication unit 331. Further, the synchronization unit 332 acquires the updated time information of the counter 333, and outputs the acquired time information to the communication unit 331. The communication unit 331 receives the time information from the synchronization unit 332, and transmits the received time information to the cable monitoring devices 500A and 500C.

[0088] In the cable monitoring device 500C, the communication unit 331 receives time information from the communication unit 331 in the cable monitoring device 500B via the electromagnetic coupling unit 300, and outputs the received time information to the synchronization unit 332. The synchronization unit 332 updates the time information of the counter 333 with the time information received from the communication unit 331. Further, the synchronization unit 332 acquires the updated time information of the counter 333, and outputs the acquired time information to the communication unit 331. The communication unit 331 receives the time information from the synchronization unit 332, and transmits the received time information to the cable monitoring device 500B.

[0089] The communication unit 331 in the cable monitoring device 500D receives time information from the communication unit 331 in the cable monitoring device 500A via the electromagnetic coupling unit 300, and calculates 1 / 2 of the difference between the received time information and the current time information of the counter 333. The difference indicates the round-trip transmission delay time between the cable monitoring device 500D and the cable monitoring device 500A, and 1 / 2 of the difference indicates the transmission delay time between the cable monitoring device 500D and the cable monitoring device 500A. The communication unit 331 in the cable monitoring device 500D transmits delay time information D1 indicating the calculated transmission delay time to the management device 400.

[0090] In addition, the communication unit 331 in the cable monitoring device 500A receives time information from the communication unit 331 in the cable monitoring device 500B via the electromagnetic coupling unit 300, and calculates 1 / 2 of the difference between the received time information and the current time information of the counter 333. The difference indicates the round-trip transmission delay time between the cable monitoring device 500A and the cable monitoring device 500B, and 1 / 2 of the difference indicates the transmission delay time between the cable monitoring device 500A and the cable monitoring device 500B. The communication unit 331 in the cable monitoring device 500A transmits delay time information D2 indicating the calculated transmission delay time to the management device 400 via the cable monitoring device 500D.

[0091] Further, the communication unit 331 in the cable monitoring device 500B receives time information from the communication unit 331 in the cable monitoring device 500C via the electromagnetic coupling unit 300, and calculates half of the difference between the received time information and the current time information of the counter 333. The difference indicates the round-trip transmission delay time between the cable monitoring device 500B and the cable monitoring device 500C, and half of the difference indicates the transmission delay time between the cable monitoring device 500B and the cable monitoring device 500C. The communication unit 331 in the cable monitoring device 500B transmits delay time information D3 indicating the calculated transmission delay time to the management device 400 via the cable monitoring devices 500A and 500D.

[0092] In this way, since the communication unit 331 in each cable monitoring device 500 transmits time information via the electromagnetic coupling unit 300, there is no need to separately provide a signal line for transmitting time information, so synchronization processing can be performed with a simple configuration.

[0093] <Abnormality detection unit> FIG. 11 is a diagram showing an example of the configuration of an abnormality detection unit in a cable monitoring device according to an embodiment of the present disclosure. Referring to FIG. 11, the abnormality detection unit 200 includes an HPF (High Pass Filter) 210, an LNA (Low Noise Amplifier) 220, an ADC (Analog Digital Converer) 230, a detection unit 240, a detection unit 250, a storage unit 270, and a determination unit 280. The detection unit 240 and the detection unit 250 are configured by, for example, an FPGA (Field-Programmable Gate Array). The determination unit 280 is realized by, for example, a processor such as a CPU (Central Processing Unit) and a DSP (Digital Signal Processor). The storage unit 270 is, for example, a non-volatile memory and is included in the FPGA.

[0094] The HPF210 attenuates components with a frequency of a predetermined frequency or less among the frequency components of the output signals received from the signal output units 120 and 120A. The output signals received from the signal output units 120 and 120A contain a lot of 50 Hz or 60 Hz noise corresponding to the frequency of the power transmitted by the underground cable 10. The HPF210 removes the noise contained in the output signals received from the signal output units 120 and 120A, for example, by attenuating the frequency components of less than 60 Hz.

[0095] The LNA220 amplifies the output signal that has passed through the HPF210 and outputs the amplified output signal to the ADC230.

[0096] The ADC230 converts the output signal received from the LNA220 into a digital signal and outputs it to the detection unit 240 and the detection unit 250. More specifically, the ADC230 generates a digital signal by sampling the output signal received from the LNA220 at a sampling frequency of, for example, 100 MHz, and outputs the generated digital signal to the detection unit 240 and the detection unit 250.

[0097] For example, the abnormality detection unit 200 discriminates between insulation breakdown and partial discharge based on the comparison result between the level of the output signal and a predetermined threshold value.

[0098] More specifically, the storage unit 270 stores a threshold value ThA and a threshold value ThB as predetermined threshold values regarding the values of the digital signals generated by the ADC230. Here, it is assumed that the threshold value ThB is larger than the threshold value ThA.

[0099] The detection unit 240 performs a comparison process of comparing the digital signal received from the ADC230 with the threshold values ThA and ThB in the storage unit 270. More specifically, the detection unit 240 performs the comparison process for each sample of the digital signal from the ADC230. That is, the detection unit 240 performs the comparison process at a comparison timing according to a 10 nanosecond cycle corresponding to the sampling frequency in the ADC230.

[0100] When the value of the digital signal received from the ADC 230 by the detector unit 240 is greater than the threshold ThA and less than the threshold ThB, the detector unit 240 acquires the time information of the counter 333, and stores the acquired time information and the detection information da including the value of the digital signal in the storage unit 270. Further, when the value of the digital signal received from the ADC 230 is greater than the threshold ThA and less than the threshold ThB as a result of the comparison process at the comparison timing, the detector unit 240 temporarily stops the comparison process until a predetermined time, for example, 5 microseconds, elapses from the comparison timing, and resumes the comparison process at the comparison timing after the predetermined time has elapsed. On the other hand, when the value of the digital signal received from the ADC 230 is less than or equal to the threshold ThA or greater than or equal to the threshold ThB, the detector unit 240 does not generate or store the detection information da.

[0101] The detector unit 250 performs a comparison process of comparing the digital signal received from the ADC 230 with the threshold ThB in the storage unit 270. More specifically, the detector unit 250 performs the comparison process for each sample of the digital signal from the ADC 230. That is, the detector unit 250 performs the comparison process at the above-mentioned comparison timing. When the value of the digital signal received from the ADC 230 by the detector unit 250 is greater than the threshold ThB, the detector unit 250 acquires the time information of the counter 333, and generates the detection information db including the acquired time information and the value of the digital signal. On the other hand, when the value of the digital signal received from the ADC 230 is less than or equal to the threshold ThB, the detector unit 250 does not generate the detection information db. After generating the detection information db, the detector unit 250 continues the comparison process at the comparison timing, and counts the number of digital signals exceeding the threshold ThB until the value of the digital signal received from the ADC 230 becomes less than or equal to the threshold ThB. When the value of the digital signal received from the ADC 230 becomes less than or equal to the threshold ThB after generating the detection information db, the detector unit 250 stores the generated detection information db in the storage unit 270 including the count number indicating the number of digital signals counted in the generated detection information db.

[0102] The determination unit 280 performs a determination process based on the detection information da and db stored in the storage unit 270 by the detection units 240 and 250.

[0103] More specifically, when the detection information da is stored in the storage unit 270 by the detection unit 240, the determination unit 280 determines that partial discharge has occurred in the underground cable 10A. Then, the determination unit 280 acquires the detection information da and the ID of its own cable monitoring device 500 from the storage unit 270, generates detection information DA including the acquired detection information da and ID, and outputs the generated detection information DA to the communication unit 331. The communication unit 331 receives the detection information DA from the determination unit 280 and transmits the received detection information DA to the management device 400 via the electromagnetic coupling unit 300.

[0104] Also, when the detection information db is stored in the storage unit 270 by the detection unit 240, the determination unit 280 determines whether or not insulation breakdown has occurred in the underground cable 10A based on the count number included in the detection information db. More specifically, when the count number included in the detection information db is a predetermined number, for example, 5,000,000 or more, that is, when the value of the digital signal is continuously greater than the threshold ThB in a period of 50 milliseconds (5,000,000 times × 10 nanosecond cycle) or more in the comparison process by the detection unit 250, the determination unit 280 determines that insulation breakdown has occurred in the underground cable 10A. Then, the determination unit 280 acquires the plurality of detection information db and the ID of its own cable monitoring device 500 from the storage unit 270, generates detection information DB including the acquired detection information db and ID, and outputs the generated detection information DB to the communication unit 331. The communication unit 331 receives the detection information DB from the determination unit 280 and transmits the received detection information DB to the management device 400 via the electromagnetic coupling unit 300. On the other hand, when the count number included in the detection information db is less than the predetermined number, the determination unit 280 does not generate the detection information DB.

[0105] In this way, since the communication unit 331 in each cable monitoring device 500 transmits the detection information DA and DB to the management device 400 via the electromagnetic coupling unit 300, there is no need to separately provide a signal line for transmitting the detection information DA and DB to the management device 400. Therefore, the detection information DA and DB can be transmitted to the management device 400 with a simple configuration.

[0106] Here, the level of the output signal output from the signal detection unit 100 when an insulation breakdown occurs in the underground cable 10A is greater than the level of the output signal output from the signal detection unit 100 when partial discharge occurs in the underground cable 10A. In the cable monitoring device 500 according to the present embodiment, the abnormality detection unit 200 discriminates between insulation breakdown and partial discharge based on the comparison result between the level of the output signal, that is, the value of the digital signal generated by the ADC 230 and the threshold ThB. Thus, insulation breakdown and partial discharge can be discriminated with a simple configuration and process.

[0107] Also, the period during which the change due to the insulation breakdown continues in the output signal output from the signal detection unit 100 when an insulation breakdown occurs in the underground cable 10A is longer than the period during which the change due to the partial discharge continues in the output signal output from the signal detection unit 100 when the partial discharge occurs in the underground cable 10A. In the cable monitoring device 500 according to the present embodiment, the determination unit 280 in the abnormality detection unit 200 determines that an insulation breakdown has occurred in the underground cable 10A when the number of counts included in the detection wave information db stored in the storage unit 270 is equal to or more than a predetermined number. Thus, the insulation breakdown in the underground cable 10A can be detected separately from the switching surge. That is, the determination unit 280 determines that an insulation breakdown has occurred in the underground cable 10A when the state where the level of the output signal is equal to or more than a predetermined value continues for a predetermined period, while determining that a switching surge has occurred in the underground cable 10A when the state where the level of the output signal is equal to or more than a predetermined value does not continue for a predetermined period.

[0108] [Management Device] FIG. 12 is a diagram showing the configuration of the management device according to the embodiment of the present disclosure. Referring to FIG. 12, the management device 400 includes an acquisition unit 420, a partial discharge calculation unit 430, a breakdown calculation unit 440, and a storage unit 450. The partial discharge calculation unit 430 is an example of a first calculation unit. The breakdown calculation unit 440 is an example of a second calculation unit. The acquisition unit 420, the partial discharge calculation unit 430, and the breakdown calculation unit 440 are realized by a processor such as a CPU and a DSP, for example. The storage unit 450 is a non-volatile memory, for example.

[0109] The acquisition unit 420 acquires a plurality of pieces of detection information DA respectively indicating the times when a plurality of cable monitoring devices 500 detect partial discharge in the underground cable 10A, and a plurality of pieces of detection information DB respectively indicating the times when the plurality of cable monitoring devices 500 detect breakdown in the underground cable 10A.

[0110] More specifically, the acquisition unit 420 is connected to the communication unit 331 in the cable monitoring device 500D via the above-described communication line. The acquisition unit 420 receives the detection information DA of the plurality of cable monitoring devices 500 from the cable monitoring device 500D via the communication line respectively. When the acquisition unit 420 receives the detection information DA, it stores the received detection information DA in the storage unit 450. Further, the acquisition unit 420 receives the detection information DB of the plurality of cable monitoring devices 500 from the cable monitoring device 500D via the communication line respectively. When the acquisition unit 420 receives the detection information DB, it stores the received detection information DB in the storage unit 450.

[0111] In addition, the acquisition unit 420 acquires delay time information indicating the transmission delay time between the cable monitoring devices 500. More specifically, the acquisition unit 420 receives the delay time information D1, D2, D3 from the cable monitoring device 500D via the communication line. When the acquisition unit 420 receives the delay time information D1, D2, D3, it stores the received delay time information D1, D2, D3 in the storage unit 450.

[0112] The partial discharge calculation unit 430 calculates the occurrence position of partial discharge in the underground cable 10A based on each detection information DA received by the acquisition unit 420. Further, the insulation breakdown calculation unit 440 calculates the occurrence position of insulation breakdown in the underground cable 10A based on each detection information DB received by the acquisition unit 420.

[0113] FIG. 13 is a diagram showing an example of the occurrence position of partial discharge in the power transmission system according to the embodiment of the present disclosure. Referring to FIG. 13, when partial discharge occurs in the underground cable 10A, the current flowing through the underground cable 10A due to the occurrence of the partial discharge propagates in the directions of the insulation connection part 42B and the insulation connection part 42C, respectively.

[0114] For example, when partial discharge occurs at an intermediate point P1 between the insulation connection part 42B, which is the monitoring position of the cable monitoring device 500B, and the insulation connection part 42C, which is the monitoring position of the cable monitoring device 500C, in the underground cable 10A, the partial discharge is detected simultaneously by the cable monitoring devices 500B and 500C. On the other hand, for example, when partial discharge occurs at a point P2 on the insulation connection part 42B side of the intermediate point P1 in the underground cable 10A, the partial discharge is detected by the cable monitoring device 500B before the cable monitoring device 500C. Therefore, the partial discharge calculation unit 430 can calibrate the occurrence position of the partial discharge based on the detection time of the partial discharge in the two cable monitoring devices 500 and the like. Similarly, the insulation breakdown calculation unit 440 can calibrate the occurrence position of the insulation breakdown based on the detection time of the insulation breakdown in the two cable monitoring devices 500 and the like.

[0115] More specifically, the memory unit 450 stores distance information indicating the distances between the monitoring positions of the respective cable monitoring devices 500 in the underground cable 10A, and speed information indicating the propagation speed of the current in the underground cable 10A. The underground cable 10A is, for example, a CV (Cross-linked polyethylene insulated Vinyl sheath) cable or an OF (Oil-Filled) cable. The propagation speed of the current in the CV cable is, for example, 172 m / μs, and the propagation speed of the current in the OF cable is, for example, 158 m / μs.

[0116] The partial discharge calculation unit 430 corrects the detection time indicated by the detection information DA stored in the storage unit 450 using some or all of the delay time information D1, D2, and D3 according to the transmission path of the detection information DA. More specifically, the partial discharge calculation unit 430 corrects the detection time indicated by the detection information DA including the ID of the cable monitoring device 500A using the delay time information D1, corrects the detection time indicated by the detection information DA including the ID of the cable monitoring device 500B using the delay time information D1 and D2, and corrects the detection time indicated by the detection information DA including the ID of the cable monitoring device 500C using the delay time information D1, D2, and D3. For example, the partial discharge calculation unit 430 corrects the detection time by adding the transmission delay time indicated by the delay time information D1 to the detection time indicated by the detection information DA including the ID of the cable monitoring device 500A. Also, for example, the partial discharge calculation unit 430 corrects the detection time by adding each transmission delay time indicated by the delay time information D1 and D2 to the detection time indicated by the detection information DA including the ID of the cable monitoring device 500B. Also, for example, the partial discharge calculation unit 430 corrects the detection time by adding each transmission delay time indicated by the delay time information D1, D2, and D3 to the detection time indicated by the detection information DA including the ID of the cable monitoring device 500C. Hereinafter, the detection time indicated by the detection information DA shall refer to the corrected detection time. Similarly, the insulation breakdown calculation unit 440 corrects the detection time indicated by the detection information DB stored in the storage unit 450 using some or all of the delay time information D1, D2, and D3 according to the transmission path of the detection information DB. Hereinafter, the detection time indicated by the detection information DB shall refer to the corrected detection time.

[0117] The partial discharge calculation unit 430 calculates the time difference between the two earliest detection times among the detection times indicated by a plurality of pieces of detection information DA regarding the same partial discharge including different IDs, which are stored in the storage unit 450. Then, based on the calculated time difference, the distance information, and the speed information in the storage unit 450, the partial discharge calculation unit 430 calculates the occurrence position of the partial discharge in the underground cable 10A. As an example, the partial discharge calculation unit 430 calculates the time difference between the detection time indicated by the detection information DA including the ID of the cable monitoring device 500A and the detection time indicated by the detection information DA including the ID of the cable monitoring device 500B as "0.26 μs". Here, it is assumed that the detection time indicated by the detection information DA including the ID of the cable monitoring device 500A is earlier than the detection time indicated by the detection information DA including the ID of the cable monitoring device 500B. Also, it is assumed that the distance between the monitoring position of the cable monitoring device 500A and the monitoring position of the cable monitoring device 500B indicated by the distance information in the storage unit 450 is "300 m". Further, it is assumed that the propagation speed indicated by the speed information in the storage unit 450 is "172 m / μs". In this case, the partial discharge calculation unit 430 determines the occurrence position of the partial discharge in the underground cable 10A to be a point 22.36 m ((0.26 μs) × (172 m / μs) / 2) closer to the cable monitoring device 500A side from the midpoint between the monitoring position of the cable monitoring device 500A and the monitoring position of the cable monitoring device 500B, that is, a point 127.64 m (150 m - 22.36 m) closer to the cable monitoring device 500B side from the monitoring position of the cable monitoring device 500A.

[0118] Further, the insulation breakdown calculation unit 440 calculates the time difference between the two earliest detection times among the detection times indicated by a plurality of pieces of detection information DB regarding the same partial discharge including different IDs, which are stored in the storage unit 450. Then, based on the calculated time difference, the distance information, and the speed information in the storage unit 450, the insulation breakdown calculation unit 440 calculates the occurrence position of the insulation breakdown in the underground cable 10A.

[0119] For example, the partial discharge calculation unit 430 and the insulation breakdown calculation unit 440 perform a process of notifying the calculated occurrence position to the administrator of the cable monitoring system 501.

[0120] Here, referring again to FIGS. 1 and 6, for example, when the cable monitoring device 500 corresponding to the ground connection portion 43B is not provided, if partial discharge occurs in the underground cable 10A in the section between the insulation connection portion 42C and the ground connection portion 43B, it is difficult to calculate the exact occurrence position of the partial discharge. Specifically, when partial discharge occurs in the underground cable 10A in the section between the insulation connection portion 42C and the ground connection portion 43B, the two earliest detection times among the plurality of detection times regarding the partial discharge are the detection times indicated by the detection information DA from the cable monitoring device 500B and the detection times indicated by the detection information DA from the cable monitoring device 500C. However, the partial discharge calculation unit 430 cannot determine at which position in the section between the insulation connection portion 42C and the ground connection portion 43B the partial discharge has occurred from the time difference between the two detection times. The same applies to the occurrence position of insulation breakdown. To solve such problems, the cable monitoring device 500 is preferably installed throughout the cable section of the underground cable 10. Specifically, the cable monitoring system 501 preferably includes the cable monitoring device 500 provided corresponding to the ground connection portion 43B shown in FIG. 1. Thereby, in the management device 400, it becomes possible to calculate the occurrence positions of partial discharge and insulation breakdown in all cable sections.

[0121] [Modification Example] FIG. 14 is a diagram showing the configuration of an abnormality detection unit according to a modification example of the embodiment of the present disclosure. Referring to FIG. 14, the abnormality detection unit 201 further includes an LNA 221 and an ADC 231 as compared with the abnormality detection unit 200. The cable monitoring device 500 may be configured to include the abnormality detection unit 201 instead of the abnormality detection unit 200.

[0122] The ADC 230 converts the output signal received from the LNA 220 into a digital signal and outputs it to the detection unit 240. That is, the ADC 230 converts the output signal that has passed through the HPF 210 into a digital signal and outputs it to the detection unit 240.

[0123] The LNA 221 amplifies the output signals received from the signal output units 120 and 120A, and outputs the amplified output signals to the ADC 231.

[0124] The ADC 231 converts the output signal received from the LNA 221 into a digital signal and outputs it to the detection unit 250. That is, the ADC 230 converts the output signal that has not passed through the HPF 210 into a digital signal and outputs it to the detection unit 250. More specifically, the ADC 231 generates a digital signal by sampling the output signal received from the LNA 221 at a sampling frequency of, for example, 100 MHz, and outputs the generated digital signal to the detection unit 250.

[0125] For example, the abnormality detection unit 201 detects partial discharge based on the output signal that has passed through the HPF 210, and detects insulation breakdown based on the output signal before passing through the HPF 210.

[0126] The detection unit 240 performs a comparison process of comparing the digital signal received from the ADC 230 with the threshold value ThA in the storage unit 270, and stores the detection information da in the storage unit 270 according to the comparison result.

[0127] The detection unit 250 performs a comparison process of comparing the digital signal received from the ADC 231 with the threshold value ThB in the storage unit 270, and stores the detection information db in the storage unit 270 according to the comparison result.

[0128] When the detection information da is stored in the storage unit 270 by the detection unit 240, the determination unit 280 determines that partial discharge has occurred in the underground cable 10A. Then, the determination unit 280 acquires the detection information da and the ID of its own cable monitoring device 500 from the storage unit 270, generates detection information DA including the acquired detection information da and ID, and outputs the generated detection information DA to the communication unit 331.

[0129] Further, when a plurality of detection information dbs corresponding to a plurality of consecutive comparison timings CTB are stored in the storage unit 270 by the detection unit 240, the determination unit 280 determines that an insulation breakdown has occurred in the underground cable 10A. Then, the determination unit 280 acquires the plurality of detection information dbs and the ID of its own cable monitoring device 500 from the storage unit 270, generates a detection information DB including each acquired detection information db and ID, and outputs the generated detection information DB to the communication unit 331.

[0130] Here, the output signal output from the signal detection unit 100 when an insulation breakdown occurs in the underground cable 10A is a signal including a low-frequency component. With a configuration that detects an insulation breakdown based on the output signal before passing through the HPF 210, like the abnormality detection unit 201 according to this modification example, the insulation breakdown can be detected more accurately.

[0131] FIG. 15 is a diagram showing the configuration of an abnormality detection unit according to a modification example of the embodiment of the present disclosure. Referring to FIG. 15, the abnormality detection unit 202 includes a storage processing unit 290 instead of the detection unit 240 and the detection unit 250, and includes a determination unit 281 instead of the determination unit 280, as compared with the abnormality detection unit 200. The cable monitoring device 500 may be configured to include the abnormality detection unit 202 instead of the abnormality detection unit 200.

[0132] For example, the abnormality detection unit 202 discriminates between insulation breakdown and partial discharge based on the waveform of the output signal.

[0133] FIGS. 16 and 17 are diagrams showing an example of an output signal received by the ADC in the cable monitoring device according to the embodiment of the present disclosure. FIG. 16 shows the output signal output from the LNA 220 in the cable monitoring device 500 when partial discharge occurs in the underground cable 10A. FIG. 17 shows the output signal output from the LNA 220 in the cable monitoring device 500 when an insulation breakdown occurs in the underground cable 10A.

[0134] Referring to FIG. 16, when partial discharge occurs in the underground cable 10A, the waveform of the output signal output from the LNA 220 is, for example, an oscillating waveform that oscillates within a period of less than 1 microsecond. Referring to FIG. 17, when insulation breakdown occurs in the underground cable 10A, the output signal output from the LNA 220 takes a saturated value over a period of, for example, 1 microsecond or more. This is because an output signal shaped to a value below a predetermined value is input to the LNA 220 by a protection circuit (not shown) arranged in front of the LNA 220.

[0135] The storage unit 270 stores a digital signal SA composed of K samples for a predetermined time generated by the ADC 230 when partial discharge occurs in the underground cable 10A, and a digital signal SB composed of K samples for a predetermined time generated by the ADC 230 when insulation breakdown occurs in the underground cable 10A. Here, K is an integer of 2 or more. The digital signal SA corresponds to the waveform of the output signal output from the LNA 220 when partial discharge occurs in the underground cable 10A, and the digital signal SB corresponds to the waveform of the output signal output from the LNA 220 when insulation breakdown occurs in the underground cable 10A.

[0136] The storage processing unit 290 receives a digital signal from the ADC 230 and acquires the time information of the counter 333. The storage processing unit 290 performs a process of attaching a timestamp indicating the time information to the digital signal received from the ADC 230 and storing the digital signal with the timestamp attached in the storage unit 270. The storage unit 270 is constituted by, for example, a ring buffer and is overwritten from the old digital signal.

[0137] The determination unit 281 detects insulation breakdown and partial discharge based on the correlation between the value of the digital signal composed of K samples stored in the storage unit 270 by the storage processing unit 290 and the digital signals SA and SB in the storage unit 270.

[0138] More specifically, at a calculation timing T1 according to a predetermined calculation period, the determination unit 281 calculates a correlation value CA between the values of a digital signal composed of K samples that are temporally continuous and stored in the storage unit 270 by the storage processing unit 290, and the value of the digital signal SA. Specifically, each time one sample of the digital signal is stored in the storage unit 270 by the storage processing unit 290, the determination unit 281 calculates a correlation value CA between the value of the digital signal composed of the most recent K samples including the sample and the value of the digital signal SA. That is, the calculation timing T1 is the timing according to the period in which the storage processing unit 290 stores the digital signal in the storage unit 270. When the calculated correlation value CA is equal to or greater than a predetermined threshold value, the determination unit 281 determines that partial discharge has occurred in the underground cable 10A. For example, the determination unit 281 generates correlation data indicating the temporal change of the correlation value CA for each calculation timing T1. When the determination unit 281 determines that partial discharge has occurred in the underground cable 10A, it generates detection information DA including, for example, the earliest time among the timestamps assigned to the digital signal composed of the K samples used for calculating the correlation value CA at the peak point in the correlation data, and outputs the generated detection information DA to the communication unit 331. Also, at a calculation timing T2 according to a predetermined calculation period, the determination unit 281 calculates a correlation value CB between the values of a digital signal composed of K samples that are temporally continuous and stored in the storage unit 270 by the storage processing unit 290, and the value of the digital signal SB. Specifically, each time one sample of the digital signal is stored in the storage unit 270 by the storage processing unit 290, the determination unit 281 calculates a correlation value CB between the value of the digital signal composed of the most recent K samples including the sample and the value of the digital signal SB. That is, the calculation timing T2 is the timing according to the period in which the storage processing unit 290 stores the digital signal in the storage unit 270. When the calculated correlation value CB is equal to or greater than a predetermined threshold value, the determination unit 281 determines that insulation breakdown has occurred in the underground cable 10A. For example, the determination unit 281 generates correlation data indicating the temporal change of the correlation value CB for each calculation timing T2.When the determination unit 281 determines that an insulation breakdown has occurred in the underground cable 10A, it generates detection information DB including, for example, the earliest time among the timestamps assigned to the digital signals composed of K samples used for calculating the correlation value CB at the peak point in the correlation data, and outputs the generated detection information DB to the communication unit 331.

[0139] Note that the abnormality detection unit 202 may be configured to discriminate between insulation breakdown and partial discharge based on the comparison result between the level of the output signal and the threshold values ThA and ThB. More specifically, the abnormality detection unit 202 further includes a detection unit 240 and a detection unit 250. Then, the determination unit 281 performs a determination process based on the detection information da and db stored in the storage unit 270 by the detection units 240 and 250, in the same manner as the determination unit 280 in the abnormality detection unit 200.

[0140] Further, the cable monitoring device 500 may be configured to include an integrated detection unit including at least any two of the abnormality detection unit 200, the abnormality detection unit 201, and the abnormality detection unit 202. The integrated detection unit is an example of the abnormality detection unit.

[0141] In this case, the integrated detection unit detects partial discharge and insulation breakdown in the underground cable 10A by comprehensively considering at least any two of the determination result by the abnormality detection unit 200, the determination result by the abnormality detection unit 201, and the determination result by the abnormality detection unit 202.

[0142] Alternatively, in the comprehensive detection unit including the abnormality detection units 200, 201, and 202, in a period TA, the abnormality detection unit 200 detects partial discharge and insulation breakdown in the underground cable 10A. In a period TB different from the period TA, the abnormality detection unit 201 detects partial discharge and insulation breakdown in the underground cable 10A. In a period TC different from the periods TA and TB, the abnormality detection unit 202 detects partial discharge and insulation breakdown in the underground cable 10A. That is, the abnormality detection unit 200 in the comprehensive detection unit discriminates between insulation breakdown and partial discharge based on the comparison result between the level of the output signal and a predetermined threshold value in the period TA. Also, the abnormality detection unit 201 in the comprehensive detection unit discriminates between insulation breakdown and partial discharge based on the waveform of the output signal in the period TB. Further, the abnormality detection unit 202 in the comprehensive detection unit detects partial discharge based on the output signal that has passed through the HPF 210 and detects insulation breakdown based on the output signal before passing through the HPF 210 in the period TC.

[0143] [Operation flow] Each device in the cable monitoring system according to the embodiment of the present disclosure includes a computer including a memory, and an arithmetic processing unit such as a CPU in the computer reads and executes a program including some or all of the steps of the following flowcharts and sequences from the memory. The programs of these multiple devices can each be installed from the outside. The programs of these multiple devices are each distributed in a state stored in a recording medium.

[0144] FIG. 18 is a flowchart defining an example of an operation procedure when the cable monitoring device according to the embodiment of the present disclosure detects partial discharge and insulation breakdown. Referring to FIG. 18, first, the cable monitoring device 500 generates an output signal corresponding to a change in the current flowing through the shielding layer 75 of the underground cable 10A or a change in the potential of the shielding layer 75 (step S102).

[0145] Next, when the cable monitoring device 500 generates detection information da, that is, when the digital signal obtained by digitally converting the output signal is greater than the threshold value ThA and less than the threshold value ThB (YES in step S104), it determines that partial discharge has occurred in the underground cable 10A, and transmits the detection information DA to the management device 400 (step S106). Next, the cable monitoring device 500 generates a new output signal (step S102).

[0146] On the other hand, when the cable monitoring device 500 generates detection information db, that is, when the digital signal obtained by digitally converting the output signal is greater than the threshold value ThB (NO in step S104 and YES in step S108), it determines whether the count number included in the detection information db is equal to or greater than a predetermined number, for example, 5,000,000 (step S110).

[0147] When the count number included in the detection information db is less than 5,000,000 (NO in step S110), the cable monitoring device 500 generates a new output signal (step S102).

[0148] On the other hand, when the count number included in the detection information db is equal to or greater than 5,000,000 (YES in step S110), the cable monitoring device 500 determines that insulation breakdown has occurred in the underground cable 10A, and transmits the detection information DB to the management device 400 (step S112). Next, the cable monitoring device 500 generates a new output signal (step S102).

[0149] On the other hand, when the cable monitoring device 500 does not generate the detection information da and db, that is, when the digital signal obtained by digitally converting the output signal is less than or equal to the threshold value ThA (NO in step S104 and NO in step S108), the cable monitoring device 500 generates a new output signal (step S102).

[0150] FIG. 19 is a diagram showing an example of a sequence of determination processing in the cable monitoring system according to the embodiment of the present disclosure. Referring to FIG. 19, the cable monitoring device 500 performs synchronization processing periodically. Specifically, the cable monitoring device 500D transmits time information to the cable monitoring device 500A at a synchronization processing timing according to a predetermined period (step S202).

[0151] Next, the cable monitoring device 500A updates the time information of the counter 333 with the time information received from the cable monitoring device 500D (step S204).

[0152] Next, the cable monitoring device 500A transmits the updated time information of the counter 333 to the cable monitoring device 500B (step S206). Also, the cable monitoring device 500A transmits time information to the cable monitoring device 500D (step S208).

[0153] Next, the cable monitoring device 500D calculates 1 / 2 of the difference between the time information received from the cable monitoring device 500A and the current time information of its own counter 333 as the transmission delay time between the cable monitoring device 500D and the cable monitoring device 500A, and transmits delay time information D1 indicating the calculated transmission delay time to the management device 400 (step S210).

[0154] Next, the cable monitoring device 500B updates the time information of the counter 333 with the time information received from the cable monitoring device 500A (step S212).

[0155] Next, the cable monitoring device 500B transmits the updated time information of the counter 333 to the cable monitoring device 500C (step S214). Also, the cable monitoring device 500B transmits time information to the cable monitoring device 500A (step S216).

[0156] Next, the cable monitoring device 500A calculates half of the difference between the time information received from the cable monitoring device 500B and the current time information of its own counter 333 as the transmission delay time between the cable monitoring device 500A and the cable monitoring device 500B, and transmits delay time information D2 indicating the calculated transmission delay time to the management device 400 via the cable monitoring device 500D (step S218).

[0157] Next, the cable monitoring device 500C updates the time information of the counter 333 with the time information received from the cable monitoring device 500B (step S220).

[0158] Next, the cable monitoring device 500C transmits the updated time information of the counter 333 to the cable monitoring device 500B (step S222).

[0159] Next, the cable monitoring device 500B calculates half of the difference between the time information received from the cable monitoring device 500C and the current time information of its own counter 333 as the transmission delay time between the cable monitoring device 500B and the cable monitoring device 500C, and transmits delay time information D3 indicating the calculated transmission delay time to the management device 400 via the cable monitoring devices 500A and 500D (step S224).

[0160] For example, when the cable monitoring devices 500B and 500C detect partial discharge in the underground cable 10A, they transmit detection information DA to the management device 400 (steps S226 and S228).

[0161] Next, the management device 400 corrects the detection time indicated by the detection information DA received from the cable monitoring device 500B using the delay time information D1 and D2, and corrects the detection time indicated by the detection information DA received from the cable monitoring device 500C using the delay time information D1, D2, and D3. Then, the management device 400 calculates the occurrence position of partial discharge in the underground cable 10A based on the corrected detection time indicated by each detection information DA, the distance information indicating the distance between the monitoring positions of the cable monitoring device 500B and the cable monitoring device 500C, and the speed information indicating the propagation speed of the current in the underground cable 10A (step S230).

[0162] Next, for example, when the cable monitoring devices 500B and 500C detect insulation breakdown in the underground cable 10A, they transmit the detection information DB to the management device 400 (steps S232 and S234).

[0163] Next, the management device 400 corrects the detection time indicated by the detection information DB received from the cable monitoring device 500B using the delay time information D1 and D2, and corrects the detection time indicated by the detection information DB received from the cable monitoring device 500C using the delay time information D1, D2, and D3. Then, the management device 400 calculates the occurrence position of insulation breakdown in the underground cable 10A based on the corrected detection time indicated by each detection information DB, the distance information indicating the distance between the monitoring positions of the cable monitoring device 500B and the cable monitoring device 500C, and the speed information indicating the propagation speed of the current in the underground cable 10A (step S236).

[0164] Note that, after the cable monitoring devices 500B and 500C detect partial discharge and transmit the detection information DA to the management device 400, an example in which insulation breakdown is detected and the detection information DB is transmitted to the management device 400 has been described. However, the cable monitoring device 500 is not limited to a configuration in which the detection information DA and the detection information DB are transmitted to the management device 400 in this order. If the cable monitoring device 500 detects insulation breakdown at a certain position in the underground cable 10A and transmits the detection information DB to the management device 400, and then detects insulation breakdown at another position in the underground cable 10A, the cable monitoring device 500 transmits the detection information DB to the management device 400 again. Also, if the cable monitoring device 500 detects insulation breakdown at a certain position in the underground cable 10A and transmits the detection information DB to the management device 400, and then detects partial discharge at another position in the underground cable 10A, the cable monitoring device 500 transmits the detection information DA to the management device 400.

[0165] Note that, although the cable monitoring system 501 according to the embodiment of the present disclosure is configured to include four cable monitoring devices 500, the present disclosure is not limited thereto. The cable monitoring system 501 may be configured to include two, three, or five or more cable monitoring devices 500. Also, the cable monitoring system 501 may be configured not to include the cable monitoring device 500D provided corresponding to the above-ground connection part 43A. Further, the cable monitoring system 501 may be configured to include a cable monitoring device 500 provided corresponding to the above-ground connection part 43B shown in FIG. 1 instead of or in addition to the cable monitoring device 500D.

[0166] Also, in the cable monitoring system 501 according to the embodiment of the present disclosure, the management device 400 is configured to be connected to the cable monitoring device 500D. However, the present disclosure is not limited thereto. The management device 400 may be connected to a cable monitoring device 500 other than the cable monitoring device 500D, or may be provided integrally with any one of the cable monitoring devices 500.

[0167] Further, in the management device 400 according to the embodiment of the present disclosure, although the acquisition unit 420 is configured to receive the detection information DA from each of the plurality of cable monitoring devices 500 via the electromagnetic coupling unit 410 and receive the detection information DB from each of the plurality of cable monitoring devices 500 via the electromagnetic coupling unit 410, the present disclosure is not limited thereto. The acquisition unit 420 may be configured to acquire the detection information DA and DB generated in each cable monitoring device 500 offline.

[0168] Further, in the cable monitoring device 500 according to the embodiment of the present disclosure, although the abnormality detection unit 200 is configured to include the detection unit 240 and the detection unit 250, the present disclosure is not limited thereto. The abnormality detection unit 200 may be configured to include a storage processing unit instead of the detection unit 240 and the detection unit 250. In this case, the storage processing unit performs a process of storing the digital signal received from the ADC 230 in the storage unit 270. The determination unit 280 performs the above-described comparison process and determination process on the digital signal stored in the storage unit 270 by the storage processing unit.

[0169] Further, in the cable monitoring device 500 according to the modification of the embodiment of the present disclosure, although the abnormality detection unit 201 is configured to include the detection unit 240 and the detection unit 250, the present disclosure is not limited thereto. The abnormality detection unit 201 may be configured to include a storage processing unit instead of the detection unit 240. In this case, the storage processing unit performs a process of storing the digital signal received from the ADC 230 in the storage unit 270. Further, the abnormality detection unit 201 may be configured to include a storage processing unit instead of the detection unit 250. In this case, the storage processing unit performs a process of storing the digital signal received from the ADC 231 in the storage unit 270. The determination unit 280 performs the above-described comparison process and determination process on the digital signal stored in the storage unit 270 by the storage processing unit.

[0170] Further, in the cable monitoring device 500 according to the embodiment of the present disclosure, although the communication unit 331 is configured to transmit the detection information DA and DB to the management device 400, the present disclosure is not limited thereto. The communication unit 331 may be configured not to transmit at least one of the detection information DA and DB to the management device 400. Further, the cable monitoring device 500 may be configured not to include the communication unit 331. In this case, the management device 400 acquires the detection information DA and DB generated in each cable monitoring device 500 offline as described above. More specifically, the determination unit 280 stores the generated detection information DA and DB in the storage unit 270. The administrator of the cable monitoring system 501 periodically or irregularly connects a recording medium such as a USB memory to the cable monitoring device 500 and copies the detection information DA and DB in the storage unit 270 to the recording medium. Then, the administrator connects the recording medium to which the detection information DA and DB are copied to the management device 400 and stores the detection information DA and DB in the storage unit 450 in the management device 400. The partial discharge calculation unit 430 and the insulation breakdown calculation unit 440 in the management device 400 calculate the occurrence positions of partial discharge and insulation breakdown based on the detection information DA and DB stored in the storage unit 450 by the administrator. Further, in this case, the cable monitoring device 500 receives, for example, a GPS (Global Positioning System) signal, acquires the current time based on the received GPS signal, and updates the time information of the counter 333.

[0171] Also, although the cable monitoring device 500 according to the embodiment of the present disclosure is configured to include the synchronization unit 332, the present disclosure is not limited thereto. The cable monitoring device 500 may be configured not to include the synchronization unit 332.

[0172] The above embodiment should be considered as illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of claims rather than the above description, and it is intended that all modifications within the meaning and scope equivalent to the scope of claims be included.

[0173] The above description includes the features appended below. [Appendix 1] A cable monitoring device for monitoring a cable having a linear conductor for transmitting electric power, an insulating layer covering the periphery of the conductor, and a shielding layer which is a conductor covering the periphery of the insulating layer, comprising: a signal detection unit that outputs an output signal according to a change in current flowing through the shielding layer or a change in potential of the shielding layer; an abnormality detection unit that detects partial discharge and insulation breakdown in the cable based on the output signal output from the signal detection unit; the abnormality detection unit detects the partial discharge based on the output signal that has passed through a high-pass filter that attenuates components below a predetermined frequency, and detects the insulation breakdown based on the output signal before passing through the high-pass filter; when a state where the level of the output signal is equal to or higher than a predetermined value continues for a predetermined period, the abnormality detection unit determines that insulation breakdown has occurred in the cable, and when the state where the level of the output signal is equal to or higher than the predetermined value does not continue for the predetermined period, the abnormality detection unit determines that an opening / closing surge has occurred in the cable. A cable monitoring device.

[0174] [Appendix 2] A plurality of cable monitoring devices installed at different positions for monitoring a cable having a linear conductor for transmitting electric power, an insulating layer covering the periphery of the conductor, and a shielding layer which is a conductor covering the periphery of the insulating layer, and a plurality of first detection information respectively indicating the times when the partial discharge in the cable is detected, and a plurality of second detection information respectively indicating the times when the insulation breakdown in the cable is detected by the plurality of cable monitoring devices, an acquisition unit that acquires; a first calculation unit that calculates the occurrence position of the partial discharge in the cable based on each of the first detection information acquired by the acquisition unit; a second calculation unit that calculates the occurrence position of the insulation breakdown in the cable based on each of the second detection information acquired by the acquisition unit, and the acquisition unit further acquires the transmission delay time between the plurality of cable monitoring devices, The first calculation unit corrects the time indicated by each piece of first detection information using the transmission delay time, and calculates the occurrence position of the partial discharge based on the corrected time of each piece of first detection information. The second calculation unit corrects the time indicated by each piece of second detection information using the transmission delay time, and calculates the occurrence position of the insulation breakdown based on the corrected time of each piece of second detection information, the management device.

Explanation of symbols

[0175] 10, 10A, 10A1, 10A2, 10B, 10B1, 10B2, 10C, 10C1, 10C2 Underground cable 11, 11A, 11B, 11C Cable terminal 12 Wire 13, 15 Grounding node 31 Manhole 41, 41A, 41B Normal connection part 42, 42A, 42B, 42C Insulated connection part 43, 43A, 43B Above-ground connection part 53 Conductive cable 71 Conductor 72 Inner semiconductive layer 73 Insulator 74 Outer semiconductive layer 75 Shielding layer 76 Sheath 77 Insulating cylinder 81 Terminal 100, 100A Signal detection unit 110, 310, 411 CT 120, 120A, 412 Signal output unit 101, 301 Ring core 102, 302 Winding 105, 106 Metal foil electrode 200, 201, 202 Abnormality detection unit 210 HPF 220, 221 LNA 230, 231 ADC 240, 250 Detection unit 270, 450 Storage unit 280, 281 Judgment unit 290 Save processing unit 300, 410 Electromagnetic coupling unit 320 Signal input / output unit 331 Communication unit 332 Synchronization unit 333 Counter 400 Management device 420 Acquisition unit 430 Partial discharge calculation unit 440 Insulation breakdown calculation unit 500, 500A, 500B, 500C Cable monitoring device 501 Cable monitoring system 502 Power transmission system

Claims

1. A cable monitoring device for monitoring a cable having a linear conductor for transmitting electricity, an insulating layer covering the periphery of the conductor, and a shielding layer that is a conductor covering the periphery of the insulating layer, a signal detection unit that outputs an output signal according to a change in current flowing through the shielding layer or a change in the potential of the shielding layer; and an abnormality detection unit that detects partial discharge and insulation breakdown in the cable based on the output signal output from the signal detection unit. A cable monitoring device.

2. The cable monitoring device according to claim 1, wherein the abnormality detection unit discriminates between the partial discharge and the insulation breakdown based on a comparison result between the level of the output signal and a predetermined threshold value.

3. When the level of the output signal is greater than a first threshold value that is the threshold value and less than a second threshold value that is the threshold value, the abnormality detection unit determines that the partial discharge has occurred, The cable monitoring device according to claim 2, wherein the abnormality detection unit determines that the insulation breakdown has occurred when a state in which the level of the output signal is equal to or greater than the second threshold value continues for a predetermined period.

4. The cable monitoring device according to any one of claims 1 to 3, wherein the abnormality detection unit discriminates between the partial discharge and the insulation breakdown based on the waveform of the output signal.

5. When the output signal is a vibration waveform that vibrates in a period less than a predetermined length, the abnormality detection unit determines that the partial discharge has occurred, The cable monitoring device according to claim 4, wherein the abnormality detection unit determines that the insulation breakdown has occurred when the output signal is a waveform saturated over a period equal to or longer than the predetermined length.

6. The abnormality detection unit detects the partial discharge based on the output signal that has passed through a high-pass filter that attenuates components below a predetermined frequency, and detects the insulation breakdown based on the output signal before passing through the high-pass filter. The cable monitoring device according to any one of claims 1 to 5.

7. The cable monitoring device further includes a notification unit that notifies other devices of the time when the abnormality detection unit detects the partial discharge. The cable monitoring device according to any one of claims 1 to 6.

8. The cable monitoring device further includes The cable monitoring device according to any one of claims 1 to 7, comprising a notification unit that notifies other devices of the time when the insulation breakdown is detected by the abnormality detection unit.

9. The cable monitoring device further comprises a synchronization unit that performs processing for time synchronization with other cable monitoring devices by communicating with the other cable monitoring devices that monitor the cable, according to any one of claims 1 to 8.

10. A plurality of cable monitoring devices installed at different positions for monitoring a cable having a linear conductor for transmitting power, an insulating layer covering the periphery of the conductor, and a shielding layer that is a conductor covering the periphery of the insulating layer, acquire a plurality of first detection information respectively indicating the times when partial discharge in the cable is detected, and a plurality of second detection information respectively indicating the times when insulation breakdown in the cable is detected by the plurality of cable monitoring devices; a first calculation unit that calculates the occurrence position of the partial discharge in the cable based on each of the first detection information acquired by the acquisition unit; a management device comprising a second calculation unit that calculates the occurrence position of the insulation breakdown in the cable based on each of the second detection information acquired by the acquisition unit.

11. A plurality of cable monitoring devices installed at different positions for monitoring a cable having a linear conductor for transmitting power, an insulating layer covering the periphery of the conductor, and a shielding layer that is a conductor covering the periphery of the insulating layer, and a management device that acquires a plurality of first detection information respectively indicating the times when the plurality of cable monitoring devices detect partial discharge in the cable, and a plurality of second detection information respectively indicating the times when the plurality of cable monitoring devices detect insulation breakdown in the cable, wherein the management device calculates the occurrence position of the partial discharge in the cable based on each of the acquired first detection information, and calculates the occurrence position of the insulation breakdown in the cable based on each of the acquired second detection information, a cable monitoring system.

12. A cable monitoring method in a cable monitoring system comprising a plurality of cable monitoring devices installed at different positions and a management device, comprising: a step in which the plurality of cable monitoring devices monitor a cable having a linear conductor for transmitting power, an insulating layer covering the periphery of the conductor, and a shielding layer that is a conductor covering the periphery of the insulating layer; The step in which the management device acquires a plurality of first detection information respectively indicating the times when the plurality of cable monitoring devices detect partial discharge in the cable; The step in which the management device acquires a plurality of second detection information respectively indicating the times when the plurality of cable monitoring devices detect insulation breakdown in the cable; The step in which the management device calculates the occurrence position of the partial discharge in the cable based on each of the acquired first detection information; A cable monitoring method including the step in which the management device calculates the occurrence position of the insulation breakdown in the cable based on each of the acquired second detection information.

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