Partial discharge position estimation device, partial discharge position estimation system, and partial discharge position estimation method

Abstract

To more accurately estimate the occurrence position of a partial discharge in a cable.SOLUTION: A partial discharge position estimation device comprises: an acquisition unit for acquiring a plurality of pieces of detection data corresponding to a plurality of detection positions of a partial discharge in a cable, the detection data indicating a relationship among the phase relative to the AC potential of commercial AC power of a partial discharge current flowing through the cable due to the occurrence of the partial discharge, the charge amount of the partial discharge, and the frequency representing the occurrence frequency of a combination of the phase and the charge amount; and an estimation unit that estimates an occurrence source of the partial discharge in the cable on the basis of the plurality of pieces of detection data.SELECTED DRAWING: Figure 17

Description

Technical Field

[0001] The present disclosure relates to a partial discharge position estimation device, a partial discharge position estimation system, and a partial discharge position estimation method.

Background Art

[0002] Conventionally, techniques have been proposed for detecting partial discharges in underground cables and early detecting deterioration of the insulating layer based on the detection results of partial discharges. For example, Patent Document 1 (Japanese Patent Laid-Open No. 3-175374) discloses the following partial discharge position calibration method. That is, the partial discharge position calibration method measures the partial discharge pulse intensity at at least three detection positions on the power cable line, and determines the position where the maximum value of the partial discharge pulse intensity exists from the gradient of the increase or decrease in the partial discharge pulse intensity between the detection positions along the length direction of the line, and calibrates this position as the occurrence position of the partial discharge.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Beyond the technology described in Patent Document 1, a technology capable of more accurately estimating the source of partial discharges in cables is desired.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide a partial discharge position estimation device, a partial discharge position estimation system, and a partial discharge position estimation method capable of more accurately estimating the source of partial discharges in a cable.

Means for Solving the Problems

[0006] The partial discharge position estimation device of the present disclosure is a partial discharge position estimation device that estimates the source of partial discharge in a cable having a linear conductor that transmits commercial alternating current 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. The device includes an acquisition unit that acquires a plurality of pieces of detection data corresponding to a plurality of detection positions of the partial discharge current in the cable, the detection data indicating a correspondence relationship between the phase of the partial discharge current, which is the current flowing through the cable during a predetermined period due to the occurrence of the partial discharge, with respect to the alternating current potential of the commercial alternating current power, the charge amount of the partial discharge current, and the frequency of occurrence of a combination of the phase and the charge amount; and an estimation unit that performs an estimation process for estimating the source based on the plurality of pieces of detection data acquired by the acquisition unit.

[0007] One aspect of the present disclosure can be realized not only as a partial discharge position estimation device including such a characteristic processing unit, but also as a program for causing a computer to execute the steps of such characteristic processing. Further, one aspect of the present disclosure can be realized as a semiconductor integrated circuit that realizes part or all of the partial discharge position estimation device, or can be realized as a system including the partial discharge position estimation device.

Advantages of the Invention

[0008] According to the present disclosure, the source of partial discharge in a cable can be estimated more accurately.

Brief Description of the Drawings

[0009]

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DETAILED DESCRIPTION OF THE INVENTION

[0010] First, the contents of the embodiments of the present disclosure will be listed and described.

[0011] (1) A partial discharge position estimation device according to an embodiment of the present disclosure is a partial discharge position estimation device that estimates a partial discharge generation source in a cable having a linear conductor that transmits commercial AC 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 includes a phase of a partial discharge current, which is a current flowing through the cable during a predetermined period due to the occurrence of the partial discharge, with respect to an AC potential of the commercial AC power, a charge amount of the partial discharge current, and a detection data indicating a correspondence relationship with a frequency, which is a frequency of appearance of a combination of the phase and the charge amount, and an acquisition unit that acquires a plurality of the detection data respectively corresponding to a plurality of detection positions of the partial discharge current in the cable, and an estimation unit that performs an estimation process for estimating the generation source based on the plurality of detection data acquired by the acquisition unit.

[0012] As described above, by acquiring detection data indicating the correspondence relationship between the phase of the partial discharge current, the charge amount of the partial discharge current, and the frequency, and estimating the partial discharge generation source based on the detection data, it is possible to estimate the partial discharge generation source while reducing the influence of noise based on the detection data in which the characteristics of the partial discharge are statistically represented. Therefore, it is possible to more accurately estimate the partial discharge generation source in the cable.

[0013] (2) In the above (1), in the estimation process, the estimation unit may estimate, as the generation source, a generation section including the generation position of the partial discharge in the cable. The estimation unit may estimate, as the generation section, any one of a detection section that is a section between the plurality of detection positions, a first section that is a section between the detection position at the first end of the plurality of detection positions and the first end of the cable, and a second section that is a section between the detection position at the second end of the plurality of detection positions and the second end of the cable.

[0014] With such a configuration, the generation section of the partial discharge in the cable can be estimated in more detail based on a plurality of detection positions of the partial discharge current.

[0015] (3) In the above (2), the estimation unit may estimate, as the generation section, any one of the plurality of detection sections partitioned by three or more of the detection positions based on the polarity of the charge amount in each detection data.

[0016] With such a configuration, based on two detection data in which the polarities of the charge amounts are inverted from each other, two detection positions in which the flowing directions of the partial discharge current are different from each other can be specified, and the generation source of the partial discharge can be narrowed down to the detection section between the two detection positions.

[0017] (4) In the above (3), in the estimation process, the estimation unit may further estimate, as the generation source, a generation region including the generation position of the partial discharge in the generation section. The estimation unit may determine maximum feature amount data that is the detection data having the maximum feature amount of the charge amount among the plurality of detection data, and may estimate the generation region based on the determination result of the maximum feature amount data.

[0018] With such a configuration, based on the determination result of the maximum feature amount data, it is possible to specify the detection position closest to the partial discharge occurrence position among the plurality of detection positions. Therefore, in the detection section estimated to be the occurrence section, the partial discharge occurrence area can be estimated more finely and accurately.

[0019] (5) In the above (4), the estimation unit may obtain, for each detection data, the maximum value of the absolute value of the charge amount in the detection data as the feature amount, and determine that the detection data with the largest maximum value among the plurality of detection data is the maximum feature amount data.

[0020] With such a configuration, the maximum feature amount data can be determined by simple processing.

[0021] (6) In the above (4), the estimation unit may obtain, for each detection data, the maximum value of the absolute value of the charge amount corresponding to the phase with the maximum frequency in the detection data as the feature amount, and determine that the detection data with the largest maximum value among the plurality of detection data is the maximum feature amount data.

[0022] With such a configuration, the influence of sudden noise can be reduced, and the maximum feature amount data can be determined more accurately. Also, for example, compared with a configuration for determining the maximum feature amount data using a predetermined test pattern, the maximum feature amount data can be determined by simple processing.

[0023] (7) In the above (4), the estimation unit may obtain, for each detection data, the maximum value of the correlation coefficient between a predetermined test pattern indicating the correspondence relationship between the phase, the charge amount, and the frequency, and the detection data as the feature amount, and determine that the detection data with the largest maximum value among the plurality of detection data is the maximum feature amount data.

[0024] With such a configuration, for example, compared to a configuration in which the maximum feature amount data is determined based on the amount of charge corresponding to the phase with the highest frequency in the detection data, the influence of sudden noise can be further reduced, and the maximum feature amount data can be determined more accurately.

[0025] (8) In any of the above (1) to (7), the cable may be cross-bonded to other cables by the shielding layer, and the estimation unit may estimate the source of the partial discharge for each cable based on information indicating the correspondence between the cable and the detection data in the estimation process.

[0026] With such a configuration, when partial discharges occur in a plurality of different cables, the source of the partial discharge in each cable can be estimated.

[0027] (9) A partial discharge position estimation system according to an embodiment of the present disclosure is a partial discharge position estimation system for estimating a source of partial discharge in a cable having a linear conductor for transmitting commercial AC 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 detection devices and a partial discharge position estimation device. The plurality of detection devices detect a partial discharge current, which is a current flowing through the cable during a predetermined period due to the occurrence of the partial discharge, at different detection positions in the cable, and generate detection data indicating the correspondence between the phase of the detected partial discharge current with respect to the AC potential of the commercial AC power, the amount of charge of the partial discharge current, and the frequency of occurrence of a combination of the phase and the amount of charge. The partial discharge position estimation device performs an estimation process for estimating the source based on the plurality of detection data generated by each detection device.

[0028] In this way, by generating detection data indicating the correspondence relationship among the phase of the partial discharge current, the charge amount of the partial discharge current, and the frequency, and estimating the partial discharge generation source based on the detection data, it is possible to estimate the partial discharge generation source while reducing the influence of noise based on the detection data in which the characteristics of the partial discharge are statistically represented. Therefore, the partial discharge generation source in the cable can be estimated more accurately.

[0029] (10) In the above (9), the detection device may determine the occurrence side of the partial discharge with reference to the connection portion between the conductors in the cable based on the detection data, and the partial discharge position estimation device may estimate the generation source based on the determination result of the occurrence side by the detection device in the estimation process.

[0030] With such a configuration, compared with a configuration in which the partial discharge position estimation device performs an estimation process based on a plurality of detection data, the processing load on the partial discharge position estimation device can be reduced.

[0031] (11) In the above (8) or (9), the detection device may calculate a feature amount of the charge amount in the detection data, and the partial discharge position estimation device may estimate the generation source based on the feature amount calculated by the detection device in the estimation process.

[0032] With such a configuration, compared with a configuration in which the partial discharge position estimation device calculates a feature amount and performs an estimation process, the processing load on the partial discharge position estimation device can be reduced.

[0033] (12) The partial discharge position estimation method according to an embodiment of the present disclosure is a partial discharge position estimation method in a partial discharge position estimation device for estimating a partial discharge generation source in a cable having a linear conductor for transmitting commercial alternating current 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 method includes obtaining detection data indicating a correspondence relationship between a phase of a partial discharge current, which is a current flowing through the cable during a predetermined period due to the occurrence of the partial discharge, with respect to an alternating current potential of the commercial alternating current power, a charge amount of the partial discharge current, and a frequency, which is a frequency of occurrence of a combination of the phase and the charge amount, and obtaining a plurality of the detection data respectively corresponding to a plurality of detection positions of the partial discharge current in the cable, and performing an estimation process for estimating the generation source based on the obtained plurality of detection data.

[0034] In this way, by obtaining detection data indicating the correspondence relationship between the phase of the partial discharge current, the charge amount of the partial discharge current, and the frequency, and estimating the partial discharge generation source based on the detection data, it is possible to estimate the partial discharge generation source while reducing the influence of noise based on the detection data in which the characteristics of the partial discharge appear statistically. Therefore, the partial discharge generation source in the cable can be estimated more accurately.

[0035] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the same or corresponding parts in the drawings 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.

[0036] <First Embodiment> [Configuration and Basic Operation] FIG. 1 is a diagram showing the configuration of a power transmission system according to a first embodiment of the present disclosure. Referring to FIG. 1, the power transmission system 511 includes underground cables 10A, 10B, 10C, a plurality of ordinary connection parts 41, a plurality of insulated connection parts 42, and aboveground connection parts 43, 44. In each connection part, actually, three connection parts corresponding to each of the three-phase underground cables 10A, 10B, 10C are provided, but in FIG. 1, for simplicity, only one connection part is shown. Hereinafter, each of the underground cables 10A, 10B, 10C is also referred to as the underground cable 10. At least a part of the power transmission system 511 is provided, for example, in the underground part of the power grid.

[0037] The aboveground connection parts 43, 44 include cable terminals 11A, 11B, 11C. The underground cable 10 is connected to the cable terminals 11A, 11B, 11C at the aboveground connection parts 43, 44. 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.

[0038] The aboveground connection parts 43, 44 are provided, for example, in a substation at a portion where the underground cable 10 appears on the ground. The ordinary connection part 41 and the insulated connection part 42 are provided, for example, inside the manhole 31.

[0039] FIG. 2 is a diagram showing an example of the configuration of an underground cable used in the power transmission system according to the first 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 commercial AC power, an internal semiconductive layer 72, an insulator 73 made of cross-linked polyethylene as an insulating layer, an external semiconductive layer 74 as a semiconductive tape, a conductive shielding layer 75, and a vinyl sheath 76. That is, the internal semiconductive layer 72 covers the periphery of the conductor 71, the insulator 73 covers the periphery of the internal semiconductive layer 72, the external semiconductive layer 74 covers the periphery of the insulator 73, the shielding layer 75 as a conductor covers the periphery of the external semiconductive layer 74, and the sheath 76 covers the periphery of the shielding layer 75.

[0040] The conductor 71 in the underground cable 10 is used for power transmission and has a high-voltage applied thereto. For example, the phase of the potential of the conductor 71 in the underground cable 10B lags behind the phase of the potential of the conductor 71 in the underground cable 10A by 120°. Also, for example, the phase of the potential of the conductor 71 in the underground cable 10C lags behind the phase of the potential of the conductor 71 in the underground cable 10B by 120°. The shielding layer 75 is conductive while being grounded in the middle of the underground cable 10. For this reason, the voltage of the shielding layer 75 is lower than that of the conductor 71.

[0041] In the power transmission system 511, as an example, a three-phase three-wire system is used as the power distribution method. In the power transmission system 511, the three-phase underground cables 10 are provided as the underground cables 10A, 10B, and 10C. Hereinafter, the configuration of each part will be described in a simplified manner.

[0042] Referring to FIG. 1 again, at the cable terminals 11A, 11B, and 11C, the shielding layers 75 of the underground cables 10A, 10B, and 10C are exposed. Terminals are provided at the connection portions of these shielding layers 75 and the grounding cable 14 or the like.

[0043] The underground cables 10A, 10B, and 10C are respectively connected to the grounding node 15 at the cable terminals 11A, 11B, and 11C. More specifically, the shielding layers 75 of the respective underground cables 10 are grounded by connecting the terminals provided in the respective underground cables 10A, 10B, and 10C to the grounding node 15 via the grounding cable 14 or the like.

[0044] 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 insulating connection portion 42. More specifically, the underground cable 10 is composed of a plurality of cables in which the conductors 71 are electrically connected at the normal connection portion 41 and the insulating connection portion 42.

[0045] FIG. 3 is a diagram showing an example of a method for connecting an underground cable in a normal connection part used in a power transmission system according to the first embodiment of the present disclosure. In FIG. 3, for ease of explanation, the conductor 71 and the shielding layer 75 of the underground cable 10A are mainly shown. The content described below is the same for the underground cable 10B and the underground cable 10C.

[0046] Referring to FIG. 3, in the normal connection part 41, the cables 20A1 and 20A2, which are the cables 20 constituting the underground cable 10A, are connected. The cable 20A1 is assumed to be the younger side, that is, the starting side in power transmission. The cable 20A2 is assumed to be the older side, that is, the ending side in power transmission.

[0047] In the normal connection part 41, for example, the shielding layers 75 of the cables 20A1 and 20A2 are exposed at the connection part between the conductors 71 of the cables 20A1 and 20A2. In the normal connection part 41, the shielding layer 75 of the cable 20A1 and the shielding layer 75 of the cable 20A2 are connected using, for example, a connecting cable 12.

[0048] When the shielding layer 75 of the cable 20A1 and the shielding layer 75 of the cable 20A2 are connected, for example, a terminal 81 is provided at the exposed part of the shielding layer 75 of the cable 20A2. Note that the terminal 81 may be provided at the exposed part of the shielding layer 75 of the cable 20A1. Then, by connecting the terminal 81 to the ground node 13 via the grounding cable 14, the shielding layer 75 of the underground cable 10A is grounded.

[0049] FIG. 4 is a diagram showing an example of a method for connecting underground cables in an insulation connection part used in the power transmission system according to the first embodiment of the present disclosure. Referring to FIG. 4, in the insulation connection part 42, cables 20A1 and 20A2 are connected, cables 20B1 and 20B2 which are cables 20 constituting the underground cable 10B are connected, and cables 20C1 and 20C2 which are cables 20 constituting the underground cable 10C are connected. Cables 20A1, 20B1, and 20C1 are assumed to be the younger side. Cables 20A2, 20B2, and 20C2 are assumed to be the older side.

[0050] In the insulation connection part 42, for example, in the connection part between the conductors 71 of the cables 20A1 and 20A2, the shielding layers 75 of the cables 20A1 and 20A2 are exposed, in the connection part between the conductors 71 of the cables 20B1 and 20B2, the shielding layers 75 of the cables 20B1 and 20B2 are exposed, and in the connection part between the conductors 71 of the cables 20C1 and 20C2, the shielding layers 75 of the cables 20C1 and 20C2 are exposed, and terminals 81 etc. are respectively provided on the exposed parts.

[0051] For example, in the insulation connection part 42, the shielding layer 75 of the underground cable 10 is cross-bonded to the shielding layer 75 of another cable. More specifically, by connecting the terminal 81 in the cable 20A2 and the terminal 81 in the cable 20B1 with the cross-bonding wire 16A, the shielding layer 75 of the cable 20A2 and the shielding layer 75 of the cable 20B1 are connected.

[0052] Also, by connecting the terminal 81 in the cable 20B2 and the terminal 81 in the cable 20C1 with the cross-bonding wire 16B, the shielding layer 75 of the cable 20B2 and the shielding layer 75 of the cable 20C1 are connected.

[0053] Also, by connecting the terminal 81 in the cable 20C2 and the terminal 81 in the cable 20A1 with the cross-bonding wire 16C, the shielding layer 75 of the cable 20C2 and the shielding layer 75 of the cable 20A1 are connected.

[0054] Hereinafter, each of the cross bond lines 16A, 16B, and 16C is also referred to as a cross bond line 16. The cross bond line 16 is an example of a line connecting the shielding layers 75 of each of the two underground cables 10.

[0055] 〔Partial Discharge Detection System〕 FIGS. 5 and 6 are diagrams showing the configuration of a partial discharge detection system according to the first embodiment of the present disclosure. FIG. 5 is a diagram showing the overall configuration of the partial discharge detection system 501. FIG. 6 is an enlarged view of one insulation connection part 42 in the partial discharge detection system 501. Referring to FIGS. 5 and 6, the partial discharge detection system 501 includes partial discharge determination devices 401A, 401B, 401C, 401D, 401E, a communication device 411, and an estimation device 421. Hereinafter, each of the partial discharge determination devices 401A, 401B, 401C, 401D, 401E is also referred to as a partial discharge determination device 401. The partial discharge determination device 401 is an example of a detection device. The estimation device 421 is an example of a partial discharge position estimation device. The partial discharge detection system 501 is used in the power transmission system 511. Note that the partial discharge detection system 501 may be configured to include two, three, four, or six or more partial discharge determination devices 401.

[0056] For example, the communication device 411 is provided corresponding to the ground connection part 43. Also, for example, the partial discharge determination device 401 is provided corresponding to the insulation connection part 42. More specifically, the partial discharge determination devices 401A, 401B, 401C, 401D, 401E are respectively provided corresponding to the insulation connection parts 42A, 42B, 42C, 42D, 42E which are the insulation connection part 42. The insulation connection parts 42A, 42B, 42C, 42D, 42E are provided in this order from the ends of the underground cables 10 connected to the cable terminals 11A, 11B, 11C of the ground connection part 43. That is, the insulation connection parts 42A, 42B, 42C, 42D, 42E are provided in this order from the younger side.

[0057] For example, a plurality of power coils Cpow corresponding to a plurality of partial discharge determination devices 401 are attached to the underground cable 10. An induced current due to the current flowing through the conductor 71 of the underground cable 10 flows through the power coil Cpow. As a result, the power coil Cpow can extract the current. The partial discharge determination device 401 operates, for example, by the power obtained by the corresponding power coil Cpow.

[0058] The partial discharge determination device 401 and the communication device 411 can communicate with each other via the underground cable 10 by inductive coupling with the shielding layer 75 in the underground cable 10. The partial discharge determination device 401 and the communication device 411 can perform PLC 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 a smart meter. Alternatively, the partial discharge determination device 401 and the communication device 411 can perform PLC communication over a shorter distance at a transmission speed of up to 200 Mbps using high-frequency PLC.

[0059] The partial discharge determination device 401 detects the occurrence of partial discharge in the underground cable 10 at the corresponding insulating connection portion 42. Note that the partial discharge determination device 401 may be configured to detect the occurrence of partial discharge in a cable other than the underground cable 10, such as a cable laid on a bridge.

[0060] The partial discharge determination device 401 detects a partial discharge current, which is a current flowing through the underground cable 10 due to the occurrence of partial discharge, at different detection positions in the underground cable 10, and generates detection data Dpd indicating the correspondence relationship between the phase P of the detected partial discharge current with respect to the AC potential of commercial AC power, the charge amount Q of the partial discharge current, and the frequency N, which is the appearance frequency of the combination of the phase P and the charge amount Q. Based on the generated detection data Dpd, the partial discharge determination device 401 determines the partial discharge cable Cpd, which is the underground cable 10 in which partial discharge has occurred among the underground cables 10A, 10B, and 10C, and the occurrence side Sd of the partial discharge with respect to the insulation connection part 42. Then, the partial discharge determination device 401 transmits detection information including the cable ID of the underground cable 10 determined to be the partial discharge cable Cpd, the generated detection data Dpd, the determination result of the occurrence side Sd, and the ID of the partial discharge determination device 401 to the communication device 411 using PLC communication.

[0061] The communication device 411 receives the detection information from the partial discharge determination device 401 and transmits the received detection information to the estimation device 421 via the network 451.

[0062] The estimation device 421 estimates the partial discharge source in the underground cable 10 based on a plurality of pieces of detection information received from the communication device 411 via the network 451. More specifically, the estimation device 421 estimates the partial discharge source in the underground cable 10 based on a plurality of pieces of detection data Dpd generated by each partial discharge determination device 401.

[0063] 〔Configuration of Partial Discharge Determination Device〕 FIG. 7 is a diagram showing the configuration of a partial discharge determination device according to the first embodiment of the present disclosure. Referring to FIG. 7, the partial discharge determination device 401 includes current transformers (CTs) 111A, 111B, 111C, detection units 121A, 121B, 121C, a processing unit 131, and a storage unit 141. Hereinafter, each of the CTs 111A, 111B, 111C is also referred to as CT111, and each of the detection units 121A, 121B, 121C is also referred to as detection unit 121. Part or all of the detection unit 121 and the processing unit 131 are realized by, for example, a processing circuitry including one or more processors. The storage unit 141 is, for example, a non-volatile memory included in the above processing circuitry.

[0064] (CT) CT111 includes a ring core and a winding wound around the ring core. The windings in CTs 111A, 111B, 111C are respectively connected to detection units 121A, 121B, 121C. CTs 111A, 111B, 111C are respectively attached such that cross bond wires 16A, 16B, 16C in the insulation connection part 42 penetrate the ring core. For example, it is assumed that the winding directions of the windings of CT111 in each partial discharge determination device 401 are the same.

[0065] When current flows through the cross bond wire 16A connecting the shielding layer 75 of the underground cable 10A and the shielding layer 75 of the underground cable 10B, an induced current flows through the winding in CT111A due to inductive coupling.

[0066] Also, when current flows through the cross bond wire 16B connecting the shielding layer 75 of the underground cable 10B and the shielding layer 75 of the underground cable 10C, an induced current flows through the winding in CT111B due to inductive coupling.

[0067] Also, when current flows through the cross bond wire 16C connecting the shielding layer 75 of the underground cable 10C and the shielding layer 75 of the underground cable 10A, an induced current flows through the winding in CT111C due to inductive coupling.

[0068] (Detection unit) The detection unit 121 monitors the current flowing through the shielding layer 75 and the cross-bonding wire 16 of the underground cable 10, and detects the occurrence of partial discharge in the underground cable 10.

[0069] More specifically, the detection unit 121A monitors the induced current flowing through the winding in the CT 111A. Further, the detection unit 121B monitors the induced current flowing through the winding in the CT 111B. Further, the detection unit 121C monitors the induced current flowing through the winding in the CT 111C.

[0070] Based on the monitoring result of the induced current flowing through the winding in the corresponding CT 111, the detection unit 121 generates detection data D indicating the correspondence relationship between the phase P of the current flowing through the shielding layer 75 and the cross-bonding wire 16 in the underground cable 10 with respect to the alternating potential of the commercial alternating current power, the charge amount Q of the current, and the frequency N of the appearance frequency of the combination of the phase P and the charge amount Q.

[0071] More specifically, the storage unit 141 stores a correspondence table Tb1 indicating the correspondence relationship between the magnitude of the induced current flowing through the winding in the CT 111 and the charge amount Q of the current flowing through the shielding layer 75 and the cross-bonding wire 16.

[0072] Further, the processing unit 131 extracts the frequency component of the commercial alternating current power from the induced current flowing through the power supply coil Cpow attached to the underground cable 10A, for example, and detects the zero-crossing point ZpA based on the extracted frequency component. Further, the processing unit 131 determines the timing when the time corresponding to the 120° phase of the commercial alternating current power has elapsed from the zero-crossing point ZpA as the zero-crossing point ZpB. Further, the processing unit 131 determines the timing when the time corresponding to the 120° phase of the commercial alternating current power has elapsed from the zero-crossing point ZpB as the zero-crossing point ZpC. The processing unit 131 notifies the detected zero-crossing point ZpA and the determined zero-crossing points ZpB and ZpC to the detection units 121A, 121B, and 121C, respectively. Hereinafter, each of the zero-crossing points ZpA, ZpB, and ZpC is also referred to as the zero-crossing point Zp.

[0073] The detection unit 121 generates a digital detection signal by sampling the induced current flowing through the winding in the corresponding CT111. The detection unit 121 acquires the charge amount Q corresponding to the sample value of the generated detection signal from the corresponding table Tb1 in the storage unit 141.

[0074] Also, the detection unit 121 calculates the sampling timing of each sample value of the detection signal as the phase P based on the zero-crossing point Zp notified from the processing unit 131. More specifically, the detection unit 121A converts the sampling timing to the phase P based on the zero-crossing point ZpA. The detection unit 121B converts the sampling timing to the phase P based on the zero-crossing point ZpB. The detection unit 121C converts the sampling timing to the phase P based on the zero-crossing point ZpC.

[0075] The detection unit 121 generates detection data D, which is two-dimensional data representing the frequency N as the appearance frequency for each of the C sections S obtained by subdividing the value ranges of the converted phase P and the acquired charge amount Q at the generation timing according to a predetermined generation period T1. The generation period T1 is, for example, 10 seconds. Here, C is an integer of 2 or more.

[0076] When the detection unit 121 generates the detection data D, it performs preprocessing to remove background noise in the generated detection data D. More specifically, as preprocessing of the detection data D, the detection unit 121 corrects the frequency N of the section S in which the charge amount Q is included in a predetermined region near zero in the detection data D to a smaller value. The detection unit 121 may correct the frequency N of the section S included in the predetermined region to zero, or may correct it to a value other than zero.

[0077] Note that the detection unit 121 is not limited to a configuration that calculates the phase P using the zero-crossing point Zp notified from the processing unit 131, and any configuration may be used as long as it calculates the phase P associated with the potential of the conductor 71 of the underground cable 10 connected using the corresponding cross-bonding wire 16. Specifically, instead of calculating the phase P using the zero-crossing point Zp notified from the processing unit 131, the detection unit 121 may extract the frequency component of the commercial AC power from the induced current flowing through the winding in the corresponding CT 111, detect the zero-crossing point Zp based on the extracted frequency component, and calculate the phase P using the detected zero-crossing point Zp. Further, the detection unit 121 may be configured to receive a signal representing the zero-crossing point Zp from outside the partial discharge determination device 401 and calculate the phase P using the zero-crossing point Zp represented by the received signal.

[0078] FIG. 8 and FIG. 9 are diagrams showing an example of the detection data D after preprocessing generated by the detection unit in the partial discharge determination device according to the first embodiment of the present disclosure. FIGS. 8 and 9 show the detection data D represented in orthogonal coordinates with the phase P and the charge amount Q as the coordinate axes. FIG. 8 shows the detection data Dx, which is the detection data D in a state where no partial discharge occurs in the underground cable 10. FIG. 9 shows the detection data Dy, which is the detection data D in a state where partial discharge has occurred in the underground cable 10.

[0079] In FIGS. 8 and 9, the horizontal axis represents the phase P [degree], and the vertical axis represents the charge amount Q [pC]. In FIGS. 8 and 9, in the two-dimensional coordinates of the phase P and the charge amount Q, a target region where the phase P is from 0° to 360° and the charge amount Q is, for example, from -96 pC to 96 pC is divided into C sections S of A rows × B columns. Here, A and B are integers of 2 or more. As an example, A is 64, B is 72, and C is 4608. In FIGS. 8 and 9, for convenience, the section S with the degree N of zero is displayed in white, and the section S with the degree N of 1 or more is displayed in black. The same applies to the following figures.

[0080] Referring to FIGS. 8 and 9, the detection data Dy has a larger ratio of the section S where the frequency N is 1 or more and the charge amount Q is equal to or greater than a predetermined threshold Th1 or the charge amount Q is equal to or less than a predetermined threshold Th2 compared to the detection data Dx. Here, the threshold Th1 is a value greater than zero, and the threshold Th2 is a value less than zero. Also, in the detection data Dy, the absolute value of the charge amount Q increases with a period of 180°.

[0081] The detection unit 121 detects the occurrence of partial discharge in the underground cable 10 based on the detection data D after preprocessing. When the detection unit 121 detects the occurrence of partial discharge in the underground cable 10, the detection data Dpd, which is the detection data D indicating the correspondence relationship between the phase P of the current flowing through the underground cable 10 due to the occurrence of partial discharge, the charge amount Q, and the frequency N, is stored in the storage unit 141.

[0082] More specifically, for example, in the generated detection data D, when the number of sections S where the charge amount Q is equal to or greater than the threshold Th1 and the frequency N is equal to or greater than a predetermined value is equal to or greater than a predetermined number, and the number of sections S where the charge amount Q is equal to or less than the threshold Th2 and the frequency N is equal to or greater than a predetermined value is equal to or greater than a predetermined number, the detection unit 121 determines whether the charge amount Q has a periodicity of 180°.

[0083] Specifically, when the approximate curve of the maximum value of the absolute value of the charge amount Q for each phase P in the detection data D has two maximum values and the phase difference between the two maximum values is a value between, for example, 170° and 190°, the detection unit 121 determines that the charge amount Q in the detection data D has a periodicity of 180°. On the other hand, when the approximate curve of the maximum value of the absolute value of the charge amount Q for each phase P in the detection data D does not have two maximum values or the phase difference between the two maximum values is not a value between 170° and 190°, the detection unit 121 determines that the charge amount Q in the detection data D does not have a periodicity of 180°.

[0084] When the detection unit 121 determines that the charge amount Q in the detection data D has a periodicity of 180°, it determines that partial discharge has occurred in the underground cable 10. In this case, the detection unit 121 stores the detection data D as detection data Dpd in the storage unit 141.

[0085] On the other hand, in the generated detection data D, the detection unit 121 determines whether the number of sections S where the charge amount Q is equal to or greater than the threshold Th1 and the frequency N is equal to or greater than the predetermined value is less than the predetermined number, or whether the number of sections S where the charge amount Q is equal to or less than the threshold Th2 and the frequency N is equal to or greater than the predetermined value is less than the predetermined number, or determines that the charge amount Q in the detection data D does not have a periodicity of 180°. If so, the detection unit 121 determines that no partial discharge has occurred in the underground cable 10. In this case, the detection unit 121 discards the detection data D and waits for a new generation timing according to the generation period T1.

[0086] (Processing unit) The processing unit 131 acquires a plurality of detection data Dpd indicating the correspondence relationship between the phase P of the partial discharge current, which is the current flowing through the underground cable 10 during a predetermined period due to the occurrence of partial discharge, the charge amount Q, and the frequency N, and the number of detection data Dpd is the same as the number of underground cables 10. For example, the processing unit 131 acquires the detection data Dpd for each cross-bonding wire 16.

[0087] More specifically, when partial discharge occurs in any of the underground cables 10A, 10B, 10C, the partial discharge current flowing through the underground cable 10 due to the occurrence of partial discharge propagates from the underground cable 10 where the partial discharge has occurred to other underground cables 10 via the cross-bonding wire 16.

[0088] Therefore, when partial discharge occurs in any of the underground cables 10A, 10B, and 10C, the plurality of detection units 121 may determine that partial discharge is occurring in the underground cable 10, and may store the detection data Dpd in which the occurrence of partial discharge is detected in the storage unit 141. Hereinafter, the detection data Dpd generated by the detection units 121A, 121B, and 121C are also referred to as detection data Da1, Db1, and Dc1, respectively.

[0089] When a plurality of detection data Dpd are respectively stored in the storage unit 141 by the plurality of detection units 121, the processing unit 131 determines a partial discharge cable Cpd, which is the underground cable 10 in which partial discharge has occurred among the underground cables 10A, 10B, and 10C, based on the plurality of detection data Dpd.

[0090] FIGS. 10 to 12 are diagrams showing an example of detection data Dpd stored in a storage unit by a detection unit in a partial discharge determination device according to a first embodiment of the present disclosure. FIGS. 10 to 12 show detection data Da1, Db1, and Dc1, respectively.

[0091] Referring to FIGS. 10 to 12, when detection data Da1, Db1, and Dc1 are respectively stored in the storage unit 141 by the detection units 121A, 121B, and 121C, the processing unit 131 acquires the detection data Da1, Db1, and Dc1 from the storage unit 141.

[0092] The processing unit 131 determines a partial discharge cable Cpd, which is the underground cable 10 in which partial discharge has occurred among the underground cables 10A, 10B, and 10C, based on the acquired detection data Da1, Db1, and Dc1.

[0093] (1) Determination of maximum detection data Dmax The processing unit 131 determines a maximum detection data Dmax, which is the detection data Dpd having the maximum detection intensity DI of the charge amount Q among the detection data Da1, Db1, and Dc1. The processing unit 131 determines the partial discharge cable Cpd based on the determination result of the maximum detection data Dmax.

[0094] (1-1) Determination Example 1 of Maximum Detection Data Dmax The processing unit 131 calculates, in the detection data Dpd, the maximum value Qm1 of the absolute value of the charge amount Q represented by the section S in which the frequency N is equal to or greater than a predetermined value. The maximum value Qm1 is an example of the detection intensity DI. The processing unit 131 calculates the maximum value Qm1 for each detection data Dpd, and determines that the detection data Dpd for which the maximum value Qm1 among the detection data Da1, Db1, and Dc1 is the largest is the maximum detection data Dmax.

[0095] In the example shown in FIGS. 10 to 12, the processing unit 131 determines that the detection data Da1 for which the maximum value Qm1 among the detection data Da1, Db1, and Dc1 is the largest is the maximum detection data Dmax.

[0096] (1-2) Determination Example 2 of Maximum Detection Data Dmax The processing unit 131 calculates, in the detection data Dpd, the sum of the frequencies N for each phase P, and calculates the maximum value Qm2 of the absolute value of the charge amount Q corresponding to the phase Pmax which is the phase P at which the calculated sum is the largest. The maximum value Qm2 is an example of the detection intensity DI. The processing unit 131 calculates the maximum value Qm2 for each detection data Dpd, and determines that the detection data Dpd for which the maximum value Qm2 among the detection data Da1, Db1, and Dc1 is the largest is the maximum detection data Dmax.

[0097] In the example shown in FIGS. 10 to 12, the processing unit 131 determines that the detection data Da1 for which the maximum value Qm2 among the detection data Da1, Db1, and Dc1 is the largest is the maximum detection data Dmax.

[0098] (1-3) Determination Example 3 of Maximum Detection Data Dmax FIG. 13 is a diagram showing an example of a test pattern TP stored in a storage unit in a partial discharge determination device according to the first embodiment of the present disclosure. FIG. 13 shows a test pattern TP represented in orthogonal coordinates with the phase P and the charge amount Q as coordinate axes. In FIG. 13, in the two-dimensional coordinates of the phase P and the charge amount Q, the phase P is from 0° to 360°, and the target area is divided into C sections S of A rows × B columns, and each section S is displayed in black and white binary according to the frequency N of the test pattern TP.

[0099] Referring to FIG. 13, the storage unit 141 stores a predetermined test pattern TP indicating the correspondence relationship between the phase P, the charge amount Q, and the frequency N. In the test pattern TP, the frequency N of the section S where the charge amount Q is zero is zero. In FIG. 12, the section S where the frequency N is zero is displayed in white, and the section S where the frequency N is 1 or more is displayed in black. For example, the test pattern TP is generated in advance based on the simulation result of the detection data Dpd when partial discharge occurs in the underground cable 10 and is stored in the storage unit 141. Note that the frequency N in the test pattern TP may be a binary value of zero or 1.

[0100] The processing unit 131 acquires the test pattern TP from the storage unit 141 and calculates the maximum value Cmax of the correlation coefficient CC between the detection data Dpd and the test pattern TP for each detection data Dpd. The maximum value Cmax is an example of the detection intensity DI.

[0101] FIG. 14 is a diagram showing an example of a method for calculating the correlation coefficient CC by the processing unit in the partial discharge determination device according to the first embodiment of the present disclosure. FIG. 14 shows a method for calculating the correlation coefficient CC between the detection data Da1 and the test pattern TP.

[0102] Referring to FIG. 14, the processing unit 131 performs normalization processing on the detection data Da1, for example, by scaling the charge amount Q such that the maximum value of the absolute value of the charge amount Q of the detection data Da1 becomes 1 pc. The processing unit 131 arranges two pieces of the detection data Da1 after the normalization processing along the direction of the phase P, and calculates a correlation coefficient CC which is a convolution value of the two pieces of detection data Da1 and the test pattern TP. More specifically, the processing unit 131 calculates the product of the frequencies N for each section S of the two pieces of detection data Da1 and the test pattern TP, and calculates the sum Nsum of the calculated products as the correlation coefficient CC.

[0103] The processing unit 131 calculates the correlation coefficient CC for each lag L while changing the lag L, which is the phase P shift of the test pattern TP with respect to the phase P of the detection data Da1, from 0° to 360°.

[0104] FIG. 15 is a diagram showing an example of the calculation result of the correlation coefficient CC by the processing unit in the partial discharge determination device according to the first embodiment of the present disclosure. In FIG. 15, the horizontal axis is the lag L, and the vertical axis is the correlation coefficient CC. FIG. 15 shows the calculation result of the correlation coefficient CC between the detection data Da1 and the test pattern TP.

[0105] Referring to FIG. 15, when the processing unit 131 calculates the correlation coefficient CC for each lag L between the detection data Da1 and the test pattern TP, it obtains the maximum value Cmax of the correlation coefficient CC between the detection data Da1 and the test pattern TP.

[0106] Similarly, the processing unit 131 calculates the correlation coefficient CC for each lag L between the detection data Db, Dc and the test pattern TP, and obtains the maximum value Cmax of the correlation coefficient CC between the detection data Db, Dc and the test pattern TP, respectively.

[0107] Then, the processing unit 131 determines that the detection data Dpd with the largest maximum value Cmax among the detection data Da1, Db1, Dc1 is the maximum detection data Dmax.

[0108] In the example shown in FIGS. 10 to 12, the detection data Dpd with the largest maximum value Cmax among the detection data Da1, Db1, and Dc1 is the detection data Da1. The processing unit 131 determines that the detection data Da1 with the largest maximum value Cmax among the detection data Da1, Db1, and Dc1 is the maximum detection data Dmax.

[0109] (2) Determination of the partial discharge cable Cpd FIG. 16 is a diagram showing the potential of the conductor of the underground cable in the power transmission system according to the first embodiment of the present disclosure. FIG. 16 shows the potential Va of the conductor 71 of the underground cable 10A and the potential Vb of the conductor 71 of the underground cable 10B.

[0110] Referring to FIG. 16, partial discharge occurs in a phase region where the potential difference between the conductor 71 and the shielding layer 75 of the underground cable 10 increases, and in a phase region where the time change of the potential difference between the conductor 71 and the shielding layer 75 of the underground cable 10 is large. Here, the potential of the shielding layer 75 can be approximated to zero volts.

[0111] Therefore, in the underground cable 10A, the partial discharge that occurs in the phase range PR1, which is the phase range from 0° to 60° with the zero crossing point ZpA as a reference, generates a partial discharge current that travels from the partial discharge occurrence position in the shielding layer 75 of the underground cable 10A towards both ends of the underground cable 10A. On the other hand, in the underground cable 10A, the partial discharge that occurs in the phase range PR2, which is the phase range from 180° to 240° with the zero crossing point ZpA as a reference, generates a partial discharge current that is drawn from both ends of the underground cable 10A to the partial discharge occurrence position in the shielding layer 75 of the underground cable 10A.

[0112] Also, in the underground cable 10B, partial discharges occurring in the phase range PR3, which is the phase range from 120° to 180° with reference to the zero-crossing point ZpA, generate partial discharge currents that flow from the position of the partial discharge in the shielding layer 75 of the underground cable 10B towards both ends of the underground cable 10B. On the other hand, in the underground cable 10B, partial discharges occurring in the phase range PR4, which is the phase range from 300° to 360° with reference to the zero-crossing point ZpA, generate partial discharge currents that are drawn from both ends of the underground cable 10B to the position of the partial discharge in the shielding layer 75 of the underground cable 10B.

[0113] For example, the processing unit 131 determines that one of the underground cables 10A and 10B is a partial discharge cable Cpd based on the phase of the potential of the conductors 71 of the two underground cables 10A and 10B to which the shielding layer 75 is connected via the cross-bonding wire 16A corresponding to the maximum detection data Dmax, and the phase PX, which is the phase corresponding to the detection intensity DI of the charge amount Q in the maximum detection data Dmax. Here, the phase PX is the phase P corresponding to the maximum value Qm1 in the above-mentioned "Determination Example 1 of the Maximum Detection Data Dmax", the phase P corresponding to the maximum value Qm2 in the above-mentioned "Determination Example 2 of the Maximum Detection Data Dmax", or the phase P based on the lag L corresponding to the maximum value Cmax in the above-mentioned "Determination Example 3 of the Maximum Detection Data Dmax", that is, the sum of the lag L and the peak phase of the test pattern TP.

[0114] More specifically, the storage unit 141 stores occurrence phase information indicating the correspondence between the phase range PR corresponding to the detection intensity DI of the charge amount Q in the maximum detection data Dmax and the partial discharge cable Cpd. The phase range PR may be in the range of 60° or may be in the range of 90°. The occurrence phase information is created in advance based on the phase of the potential of the conductors 71 of each underground cable 10.

[0115] When the processing unit 131 determines that the detection data Da1 is the maximum detection data Dmax, it detects the phase PX corresponding to the detection intensity DI of the charge amount Q in the detection data Da1. Based on the detected phase PX and the generated phase information in the storage unit 141, the processing unit 131 determines that one of the underground cables 10A and 10B is the partial discharge cable Cpd. Specifically, when the detected phase PX is included in the phase range PR1 or the phase range PR2 at the maximum detection data Dmax, the processing unit 131 determines that the underground cable 10A is the partial discharge cable Cpd. On the other hand, when the detected phase PX is included in the phase range PR3 or the phase range PR4 at the maximum detection data Dmax, the processing unit 131 determines that the underground cable 10B is the partial discharge cable Cpd.

[0116] (3) Determination of the occurrence side Sd of partial discharge Referring to FIG. 6 again, the processing unit 131 further determines the occurrence side Sd of partial discharge with respect to the insulation connection portion 42 based on the determination result of the maximum detection data Dmax and the determination result of the partial discharge cable Cpd.

[0117] For example, as the occurrence side Sd of partial discharge, the processing unit 131 determines the occurrence cable 20pd, which is the cable 20 where partial discharge has occurred, among the cable 20 on the young side and the cable 20 on the old side with respect to the insulation connection portion 42.

[0118] More specifically, when the processing unit 131 determines that the detection data Da1 is the maximum detection data Dmax and determines that the underground cable 10A is the partial discharge cable Cpd, among the cable 20A2 and the cable 20B1 connected using the cross bond line 16A corresponding to the detection data Da1, the processing unit 131 determines that the cable 20A2 that constitutes the underground cable 10A is the occurrence cable 20pd.

[0119] Further, when the processing unit 131 determines that the detection data Da1 is the maximum detection data Dmax and determines that the underground cable 10B is the partial discharge cable Cpd, it determines that the cable 20B1 constituting the underground cable 10B among the cables 20A2 and 20B1 connected using the cross bond wire 16A corresponding to the detection data Da1 is the generated cable 20pd.

[0120] Further, when the processing unit 131 determines that the detection data Db1 or the detection data Dc1 is the maximum detection data Dmax, in the same manner as when it determines that the detection data Da1 is the maximum detection data Dmax, it determines that the cable 20 constituting the partial discharge cable Cpd among the two cables 20 connected using the cross bond wire 16 corresponding to the maximum detection data Dmax is the generated cable 20pd.

[0121] The processing unit 131 creates detection information including the cable ID of the underground cable 10 determined to be the partial discharge cable Cpd, the determination result of the generation side Sd, the detection data Dpd determined to be the maximum detection data Dmax, and the ID of the partial discharge determination device 401. The processing unit 131 transmits the created detection information to the communication device 411 using PLC communication.

[0122] Here, when partial discharge occurs in the underground cable 10, the partial discharge current flowing through the underground cable 10 due to the occurrence of the partial discharge propagates to each insulation connection part 42. Therefore, when partial discharge occurs in the underground cable 10, the processing unit 131 in each partial discharge determination device 401 creates detection information and transmits it to the communication device 411. Note that since the partial discharge current attenuates as it propagates, some of the partial discharge determination devices 401 in the partial discharge detection system 501 may not be able to detect the generated partial discharge and may not create detection information or transmit it to the communication device 411.

[0123] The communication device 411 receives the detection information from each partial discharge determination device 401 and transmits the received detection information to the estimation device 421 via the network 451.

[0124] 〔Configuration of Estimation Device〕 FIG. 17 is a diagram showing an example of the configuration of an estimation device according to the first embodiment of the present disclosure. Referring to FIG. 17, the estimation device 421 includes a communication unit 211, an estimation unit 221, and a storage unit 231. The communication unit 211 is an example of an acquisition unit. Part or all of the communication unit 211 and the estimation unit 221 are realized by, for example, a processing circuit including one or more processors. The storage unit 231 is, for example, a non-volatile memory included in the processing circuit.

[0125] The storage unit 231 stores connection position information indicating the correspondence between the ID of the partial discharge determination device 401 and the position of the insulation connection portion 42 where the partial discharge determination device 401 is provided. Further, the storage unit 231 stores the test pattern TP in the same manner as the storage unit 141 in the partial discharge determination device 401.

[0126] (Communication Unit) The communication unit 211 acquires a plurality of detection information respectively corresponding to a plurality of detection positions of the partial discharge current in the underground cable 10. That is, the communication unit 211 acquires a plurality of detection information respectively corresponding to a plurality of insulation connection portions 42. More specifically, the communication unit 211 receives detection information including detection data Dpd and generation side Sd from each partial discharge determination device 401 via the communication device 411. The communication unit 211 stores the received detection information in the storage unit 231.

[0127] For example, the communication unit 211 periodically or aperiodically transmits a synchronization signal for synchronizing the generation period T1 of each partial discharge determination device 401 to each partial discharge determination device 401 via the communication device 411. Each partial discharge determination device 401 receives the synchronization signal via the communication device 411 and performs processing for synchronizing the generation period T1 using the received synchronization signal.

[0128] (Estimation Unit) Based on a plurality of detection data Dpd acquired by the communication unit 211, the estimation unit 221 performs an estimation process to estimate the partial discharge source in the underground cable 10. More specifically, when a plurality of detection information is stored in the storage unit 231 by the communication unit 211, the estimation unit 221 acquires the plurality of detection information. The estimation unit 221 performs an estimation process to estimate the partial discharge source in the partial discharge cable Cpd based on the acquired plurality of detection information.

[0129] For example, in the estimation process, the estimation unit 221 estimates the partial discharge source for each underground cable 10 based on the detection information. More specifically, when the plurality of detection information generated in the same generation cycle T1 includes different cable IDs, it means that the plurality of underground cables 10 are partial discharge cables Cpd. The estimation unit 221 groups the plurality of detection information acquired from the storage unit 231 based on the cable ID and detection data Dpd included in the detection information, for each detection information including the same cable ID. The estimation unit 221 arranges the detection data Dpd included in each detection information belonging to the same group in the order of arrangement of the partial discharge determination devices 401 that are the generation sources of the detection data Dpd, based on the connection position information in the storage unit 231. Then, the estimation unit 221 generates alignment data Dln indicating the correspondence between the arranged detection data Dpd and the position of the insulating connection portion 42 for each group of detection information. The estimation unit 221 estimates the partial discharge source for each partial discharge cable Cpd based on the created alignment data Dln.

[0130] For example, in the estimation process, the estimation unit 221 estimates a generation section Prg including the generation position Ppd of partial discharge in the partial discharge cable Cpd as the generation source of the partial discharge. The estimation unit 221 estimates any one of a detection section Rd between a plurality of detection positions of the partial discharge current in the partial discharge cable Cpd, a section R1 between the detection position at the first end among the plurality of detection positions and the first end of the partial discharge cable Cpd, and a section R2 between the detection position at the second end among the plurality of detection positions and the second end of the partial discharge cable Cpd as the generation section Prg in the partial discharge cable Cpd. More specifically, in the estimation process, the estimation unit 221 estimates any one of a detection section Rd between a plurality of insulation connection parts 42, a section R1 on the younger side than the insulation connection part 42A in the partial discharge cable Cpd, and a section R2 on the older side than the insulation connection part 42E as the generation section Prg. The section R1 is an example of a first section, and the section R2 is an example of a second section.

[0131] (Estimation Example 1) FIG. 18 is a diagram showing an example of an estimation process by an estimation unit in an estimation device according to the first embodiment of the present disclosure. FIG. 18 shows the correspondence between the positions of the insulation connection parts 42 and the detection data Dpd generated in the partial discharge determination device 401 provided corresponding to the insulation connection parts 42. Hereinafter, the detection data Dpd generated in the partial discharge determination devices 401A, 401D, 401C, 401D, 401E are also referred to as detection data DpdA, DpdB, DpdC, DpdD, DpdE, respectively. In FIG. 18, the horizontal axis represents the distance of the insulation connection part 42 from a predetermined reference point. The reference point is, for example, the ground connection part 43.

[0132] Referring to FIG. 18, the estimation unit 221 estimates the generation section Prg based on the polarity of the charge amount Q in each detection data Dpd. More specifically, the estimation unit 221 estimates that any one of the detection sections Rd1, Rd2, Rd3, Rd4 partitioned by the five insulation connection sections 42 is the generation section Prg based on the polarity of the charge amount Q in each detection data Dpd. The detection section Rd1 is a detection section Rd partitioned by the insulation connection sections 42A and 42B. The detection section Rd2 is a detection section Rd partitioned by the insulation connection sections 42B and 42C. The detection section Rd3 is a detection section Rd partitioned by the insulation connection sections 42C and 42D. The detection section Rd4 is a detection section Rd partitioned by the insulation connection sections 42D and 42E.

[0133] More specifically, when the polarities of the charge amounts Q in the detection data DpdB and DpdC corresponding to the adjacent insulation connection sections 42 refer to the alignment data Dln and are inverted from each other, the estimation unit 221 determines that the detection section Rd2 between the insulation connection section 42B where the partial discharge determination device 401B that is the source of the detection data DpdB is provided and the insulation connection section 42C where the partial discharge determination device 401C that is the source of the detection data DpdC is provided is the generation section Prg.

[0134] Note that when the winding directions of the windings of the CT111 in each partial discharge determination device 401 are not aligned, the estimation unit 221 performs an inversion process of inverting the positive and negative of the charge amount Q in the detection data Dpd based on the information indicating the winding directions of the windings of the CT111 in each partial discharge determination device 401 obtained in advance. Then, the estimation unit 221 estimates the generation section Prg based on the polarity of the charge amount Q in the detection data Dpd after the inversion process.

[0135] For example, the estimation unit 221 further estimates a generation region Rpd that includes a partial discharge generation position Ppd in the generation section Prg as a generation source of the partial discharge. The generation region Rpd is a region smaller than the generation section Prg. The estimation unit 221 determines the maximum feature amount data Dpdmax that is the detection data Dpd with the largest Q value among the five detection data Dpds, and estimates the generation region Rpd based on the determination result of the maximum feature amount data Dpdmax. The Q value is an example of a feature amount.

[0136] For example, as the Q value of the detection data Dpd, the estimation unit 221 calculates, for each detection data Dpd, the maximum value Qm1 of the absolute value of the charge amount Q in the same manner as the processing unit 131 in the partial discharge determination device 401. Then, the estimation unit 221 determines that the detection data Dpd with the largest maximum value Qm1 among the five detection data Dpds is the maximum feature amount data Dpdmax.

[0137] Alternatively, as the Q value of the detection data Dpd, the estimation unit 221 calculates, for each detection data Dpd, the maximum value Qm2 of the absolute value of the charge amount Q corresponding to the phase Pmax at which the total sum of the frequencies N is maximized in the same manner as the processing unit 131 in the partial discharge determination device 401. Then, the estimation unit 221 determines that the detection data Dpd with the largest maximum value Qm2 among the five detection data Dpds is the maximum feature amount data Dpdmax.

[0138] Alternatively, as the Q value of the detection data Dpd, the estimation unit 221 acquires the test pattern TP from the storage unit 231 in the same manner as the processing unit 131 in the partial discharge determination device 401, and calculates, for each detection data Dpd, the maximum value Cmax of the correlation coefficient CC between the detection data Dpd and the test pattern TP. Then, the estimation unit 221 determines that the detection data Dpd with the largest maximum value Cmax among the five detection data Dpds is the maximum feature amount data Dpdmax.

[0139] FIG. 19 is a diagram showing an example of the estimation process by the estimation unit in the estimation device according to the first embodiment of the present disclosure. FIG. 19 shows the correspondence between the position of the insulation connection part 42 and the detection data Dpd and Q values generated in the partial discharge determination device 401 provided corresponding to the insulation connection part 42. In FIG. 19, the horizontal axis represents the distance of the insulation connection part 42 from the reference point, and the vertical axis represents the Q value.

[0140] Referring to FIG. 19, for example, when the estimation unit 221 determines that the detection section Rd2 is the occurrence section Prg and determines that the detection data DpdB is the maximum feature amount data Dpdmax, referring to the alignment data Dln, the occurrence region Rpd is estimated to be the region between the intermediate position between the insulation connection parts 42B and 42C and the insulation connection part 42B in the partial discharge cable Cpd.

[0141] When the estimation unit 221 estimates the occurrence position Ppd, it performs a notification process of notifying the user of the estimation result of the occurrence position Ppd and the partial discharge cable Cpd of the estimation device 421.

[0142] Note that the estimation unit 221 may estimate the occurrence position Ppd of the partial discharge as the partial discharge generation source. In this case, for example, the estimation unit 221 estimates the internal division point of the detection section Rd2 calculated based on the ratio between the Q value of the detection data DpdB and the Q value of the detection data DpdC as the occurrence position Ppd. Alternatively, the estimation unit 221 calculates the maximum value of the approximate curve connecting the plots of the Q values and estimates the position corresponding to the calculated maximum value as the occurrence position Ppd.

[0143] (Estimation Example 2) FIG. 20 is a diagram showing an example of the estimation process by the estimation unit in the estimation device according to the first embodiment of the present disclosure. FIG. 20 shows the correspondence between the position of the insulation connection part 42 and the detection data Dpd generated in the partial discharge determination device 401 provided corresponding to the insulation connection part 42. In FIG. 20, the horizontal axis represents the distance of the insulation connection part 42 from the reference point.

[0144] Referring to FIG. 20, when the polarities of the charge amounts Q are the same in the five detection data Dpd, the estimation unit 221 estimates that either one of the intervals R1 and R2 is the generation interval Prg.

[0145] FIG. 21 is a diagram showing an example of an estimation process by an estimation unit in an estimation device according to the first embodiment of the present disclosure. FIG. 21 shows the correspondence between the position of the insulating connection portion 42 and the detection data Dpd and Q values generated in the partial discharge determination device 401 provided corresponding to the insulating connection portion 42. In FIG. 21, the horizontal axis is the distance of the insulating connection portion 42 from the reference point, and the vertical axis is the Q value.

[0146] Referring to FIG. 21, for example, when the estimation unit 221 determines that the detection data DpdA is the maximum feature amount data Dpdmax, it refers to the alignment data Dln and estimates that the interval R1 is the generation interval Prg.

[0147] For example, the estimation unit 221 further estimates at least one of the generation region Rpd and the generation position Ppd based on the ratio between the Q value of the detection data DpdA determined to be the maximum feature amount data Dpdmax and the Q values of the detection data Dpd other than the detection data DpdA.

[0148] When the estimation unit 221 estimates the partial discharge generation source, it performs a notification process of notifying the user of the estimation result of the generation source and the partial discharge cable Cpd of the estimation device 421.

[0149] [Operation flow] FIG. 22 is a flowchart defining an example of an operation procedure when the partial discharge determination according to the first embodiment of the present disclosure determines the partial discharge cable Cpd.

[0150] Referring to FIG. 22, first, the partial discharge determination device 401 starts monitoring the current flowing through the shielding layer 75 and the cross bond wire 16 of the underground cable 10 (step S11).

[0151] Next, the partial discharge determination device 401 waits for the generation timing according to the generation period T1 (NO in step S12), and at the generation timing according to the generation period T1 (YES in step S12), generates detection data Da1, Db1, Dc1, and performs preprocessing on the generated detection data Da1, Db1, Dc1 (step S13).

[0152] Next, the partial discharge determination device 401 determines whether partial discharge has occurred in the underground cable 10 based on the detection data Da1, Db1, Dc1 after preprocessing (step S14).

[0153] Next, when the partial discharge determination device 401 determines that no partial discharge has occurred in the underground cable 10 (NO in step S15), it discards the detection data Da1, Db1, Dc1 and waits for a new generation timing according to the generation period T1 (NO in step S12).

[0154] On the other hand, when the partial discharge determination device 401 determines that partial discharge has occurred in the underground cable 10 (YES in step S15), it determines the maximum detection data Dmax, which is the detection data D with the largest charge amount Q among the detection data Da1, Db1, Dc1, according to determination example 1, determination example 2, or determination example 3 of the maximum detection data Dmax described above. As an example, the partial discharge determination device 401 determines that the detection data Da1 is the maximum detection data Dmax (step S16).

[0155] Next, the partial discharge determination device 401 detects the phase PX corresponding to the detection intensity DI of the charge amount Q in the maximum detection data Dmax, and determines the partial discharge cable Cpd based on the detected phase PX and the phase information of occurrence (step S17).

[0156] Next, the partial discharge determination device 401 determines the occurrence side Sd of partial discharge with respect to the insulation connection portion 42 based on the determination result of the maximum detection data Dmax and the determination result of the partial discharge cable Cpd (step S18).

[0157] Next, the partial discharge determination device 401 transmits detection information including the cable ID of the underground cable 10 determined to be the partial discharge cable Cpd, the determination result of the occurrence side Sd, the detection data Dpd determined to be the maximum detection data Dmax, and the ID of the partial discharge determination device 401 to the communication device 411 using PLC communication (step S19).

[0158] Next, the partial discharge determination device 401 waits for a new generation timing according to the generation cycle T1 (NO in step S12).

[0159] FIG. 23 is a flowchart defining an example of an operation procedure when the estimation device according to the first embodiment of the present disclosure estimates the partial discharge source in the partial discharge cable Cpd.

[0160] Referring to FIG. 23, first, the estimation device 421 waits for the arrival of detection information (NO in step S21). When receiving a plurality of detection information from the communication device 411 (YES in step S21), based on the received detection information and the connection position information in the storage unit 231, the detection data Dpd included in each detection information is arranged according to the arrangement order of the partial discharge determination devices 401 that are the generation sources of the detection data Dpd, and alignment data Dln indicating the correspondence between the arranged detection data Dpd and the position of the insulation connection part 42 is generated (step S22).

[0161] Next, the estimation device 421 determines the maximum feature amount data Dpdmax among the plurality of detection data Dpd respectively included in the plurality of detection information (step S23).

[0162] Next, the estimation device 421 performs an estimation process of estimating the source of occurrence in the partial discharge cable Cpd based on the alignment data Dln, the polarities of the charge amounts Q in the respective detection data Dpd, and the determination result of the maximum feature amount data Dpdmax. For example, when the polarities of the charge amounts Q in the detection data DpdB and DpdC are inverted from each other, the estimation device 421 determines that the detection section Rd2 is the occurrence section Prg. Also, for example, when it is determined that the polarities of the charge amounts Q are the same in each detection data Dpd and the detection data DpdA is the maximum feature amount data Dpdmax, the estimation device 421 estimates that the section R1 is the occurrence section Prg (step S24).

[0163] Next, the estimation device 421 performs a notification process of notifying the user of the estimation result of the source of occurrence and the partial discharge cable Cpd to the estimation device 421 (step S25).

[0164] FIG. 24 is a diagram showing an example of a sequence of an estimation process of an occurrence position in a partial discharge detection system according to the first embodiment of the present disclosure.

[0165] Referring to FIG. 24, first, the partial discharge determination device 401 generates detection data D at a generation timing according to the generation period T1 and performs pre-processing of the generated detection data D (step S31).

[0166] Next, when the partial discharge determination device 401 determines that partial discharge has occurred in the underground cable 10 based on the detection data D after pre-processing, the partial discharge determination device 401 determines the partial discharge cable Cpd (step S32).

[0167] Next, the partial discharge determination device 401 transmits detection information including the cable ID of the underground cable 10 determined to be the partial discharge cable Cpd, the determination result of the occurrence side Sd, the detection data Dpd determined to be the maximum detection data Dmax, and the ID of the partial discharge determination device 401 to the communication device 411 using PLC communication (step S33).

[0168] Next, the communication device 411 receives detection information from each partial discharge determination device 401, and transmits the received detection information to the estimation device 421 via the network 451 (step S34).

[0169] Next, the estimation device 421 determines the maximum feature amount data Dpdmax among the plurality of detection data Dpd included in the plurality of received detection information respectively (step S35).

[0170] Next, the estimation device 421 performs an estimation process of estimating the partial discharge generation source in the partial discharge cable Cpd based on the alignment data Dln, the polarity of the charge amount Q in each detection data Dpd, and the determination result of the maximum feature amount data Dpdmax (step S36).

[0171] Next, the estimation device 421 performs a notification process of notifying the user of the estimation result of the partial discharge generation source and the partial discharge cable Cpd of the estimation device 421 (step S37).

[0172] Note that in the partial discharge determination device 401 according to the first embodiment of the present disclosure, the detection unit 121 is configured to perform preprocessing of the detection data D, but is not limited thereto. The detection unit 121 may be configured not to perform preprocessing of the detection data D.

[0173] Also, the partial discharge determination device 401 according to the first embodiment of the present disclosure is configured to include the CT 111 and the detection unit 121, but is not limited thereto. The partial discharge determination device 401 may be configured not to include the CT 111 and the detection unit 121. In this case, the processing unit 131 acquires detection data D indicating the correspondence relationship between the phase P of the partial discharge current flowing through the underground cable 10 due to the occurrence of partial discharge, the charge amount Q, and the frequency N from a device outside the partial discharge determination device 401.

[0174] Also, although the partial discharge determination device 401 according to the first embodiment of the present disclosure is configured to include the CT 111, it is not limited thereto. The partial discharge determination device 401 may be configured to include another sensor, such as an antenna, for detecting the current flowing through the cross bond wire 16 instead of the CT 111.

[0175] Also, in the partial discharge determination device 401 according to the first embodiment of the present disclosure, although the processing unit 131 is configured to transmit the detection information to the communication device 411 using PLC communication, it is not limited thereto. Instead of transmitting the detection information to the communication device 411, the processing unit 131 may be configured to save the detection information in a storage device, such as a USB (Universal Serial Bus) memory, that is insertable into the partial discharge determination device 401.

[0176] Also, in the partial discharge determination device 401 according to the first embodiment of the present disclosure, although the processing unit 131 is configured to determine the occurrence side Sd of the partial discharge, it is not limited thereto. The processing unit 131 may be configured to determine the partial discharge cable Cpd while not determining the occurrence side Sd of the partial discharge.

[0177] Also, in the estimation device 421 according to the first embodiment of the present disclosure, although the estimation unit 221 is configured to estimate that one of the detection section Rd and the sections R1, R2 is the occurrence section Prg, it is not limited thereto. For example, the estimation unit 221 may be configured to estimate the occurrence position Ppd based on each detection data Dpd without estimating the occurrence section Prg.

[0178] Also, in the estimation device 421 according to the first embodiment of the present disclosure, although the estimation unit 221 is configured to estimate the occurrence section Prg and the occurrence region Rpd based on the polarity of the charge amount Q in each detection data Dpd and the determination result of the maximum feature amount data Dpdmax, it is not limited thereto. The estimation unit 221 may be configured to estimate the occurrence section Prg while not estimating the occurrence region Rpd.

[0179] Also, in the estimation device 421 according to the first embodiment of the present disclosure, although the estimation unit 221 is configured to estimate the partial discharge generation source in the underground cable 10 based on a plurality of detection data Dpd generated by each partial discharge determination device 401, the present disclosure is not limited thereto. The estimation unit 221 may be configured to estimate the generation source based on the determination result of the generation side Sd included in the detection information instead of the detection data Dpd. More specifically, the estimation unit 221 estimates the generation section Prg by matching the determination results of the generation side Sd included in each detection information. In this case, since the polarity of the charge amount Q in the detection data Dpd may be arbitrary, the estimation unit 221 does not have to perform the above-described inversion process.

[0180] Also, in the estimation device 421 according to the first embodiment of the present disclosure, although the estimation unit 221 is configured to calculate the Q value of the detection data Dpd included in each detection information, the present disclosure is not limited thereto. For example, the processing unit 131 in each partial discharge determination device 401 may be configured to calculate the Q value according to a common calculation method and notify the calculated Q value to the estimation device 421. In this case, the estimation unit 221 in the estimation device 421 estimates the generation source based on the Q value calculated by each partial discharge determination device 401 in the estimation process. More specifically, the estimation unit 221 acquires the Q value calculated by each partial discharge determination device 401, determines the maximum feature amount data Dpdmax based on the acquired Q value, and performs estimation of the generation section Prg and the like based on the determination result of the maximum feature amount data Dpdmax.

[0181] Also, in the partial discharge determination device 401 according to the first embodiment of the present disclosure, although the processing unit 131 is configured to determine the partial discharge cable Cpd based on a plurality of detection data D respectively stored in the storage unit 141 by a plurality of detection units 121, the present disclosure is not limited thereto. The processing unit 131 may perform a correction process of scaling the charge amount Q in each detection data D based on a predetermined correction parameter created in advance for each CT111, and may be configured to determine the partial discharge cable Cpd based on the plurality of detection data D after the correction process. The correction parameter is created in advance based on the charge amount Q of the detection data D generated by the corresponding detection unit 121 in the corresponding partial discharge determination device 401 when a calibration current of a predetermined level is passed through the cross bond wire 16 in each insulation connection part 42. Thereby, the influence of the individual variations of CT111 and the detection unit 121 in the detection data D generated by each partial discharge determination device 401 is reduced, and the detection data D with the same Q value can be obtained for the partial discharge current flowing through the underground cable 10. Note that instead of the processing unit 131 performing the correction process, the detection unit 121 may be configured to generate the detection data D using the corresponding table Tb1 corrected using the correction parameter.

[0182] By the way, from the viewpoint of reducing the maintenance cost of the underground cable 10 and the like, a technique capable of more accurately estimating the occurrence position Ppd of partial discharge in the underground cable 10 is desired.

[0183] More specifically, in the technique described in Patent Document 1, the occurrence position of partial discharge in a power cable is calibrated based on the intensity of a single partial discharge pulse. However, in the technique described in Patent Document 1, there are cases where the occurrence position of partial discharge cannot be accurately estimated due to the influence of variations in the intensity of partial discharge pulses and the influence of noise.

[0184] In contrast, in the estimation device 421 according to the first embodiment of the present disclosure, the communication unit 211 obtains detection data Dpd indicating the correspondence relationship between the phase P of the partial discharge current, which is the current flowing through the underground cable 10 during a predetermined period due to the occurrence of partial discharge, with respect to the AC potential of the commercial AC power, the charge amount Q of the partial discharge current, and the frequency N of the appearance of the combination of the phase P and the charge amount Q. The detection data Dpd corresponds to a plurality of detection positions of the partial discharge current in the underground cable 10, and a plurality of detection data Dpd are obtained. The estimation unit 221 estimates the occurrence position Ppd of the partial discharge in the underground cable 10 based on the plurality of detection data Dpd obtained by the communication unit 211.

[0185] In this way, by acquiring the detection data Dpd indicating the correspondence relationship between the phase P, the charge amount Q, and the frequency N, and estimating the occurrence position Ppd of the partial discharge based on the detection data Dpd, the occurrence position Ppd of the partial discharge can be estimated while reducing the influence of noise based on the detection data Dpd in which the characteristics of the partial discharge appear statistically. Therefore, the occurrence positions Ppd of the partial discharge in the plurality of underground cables 10 can be estimated more accurately.

[0186] Next, another embodiment of the present disclosure will be described with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated.

[0187] <Second Embodiment> [Configuration and Basic Operation] This embodiment relates to a partial discharge detection system 502 that monitors the current flowing through the conductor 71 in the underground cable 10, as compared with the partial discharge detection system 501 according to the first embodiment. Except for the content described below, it is the same as the partial discharge detection system 501 according to the first embodiment.

[0188] FIG. 25 and FIG. 26 are diagrams showing the configuration of a partial discharge detection system according to a second embodiment of the present disclosure. FIG. 25 is a diagram showing the overall configuration of the partial discharge detection system 502. FIG. 26 is an enlarged view of one insulation connection part 42 in the partial discharge detection system 502. Referring to FIGS. 25 and 26, the partial discharge detection system 502 includes partial discharge determination devices 402A, 402B, 402C, 402D, and 402E instead of the partial discharge determination device 401 as compared with the partial discharge detection system 501. Hereinafter, each of the partial discharge determination devices 402A, 402B, 402C, 402D, and 402E is also referred to as the partial discharge determination device 402. The partial discharge detection system 502 is used in the power transmission system 511. Note that the partial discharge detection system 502 may be configured to include two, three, four, or six or more partial discharge determination devices 402.

[0189] For example, the partial discharge determination device 402 is provided corresponding to the insulation connection part 42. More specifically, the partial discharge determination devices 402A, 402B, 402C, 402D, and 402E are respectively provided corresponding to the insulation connection parts 42A, 42B, 42C, 42D, and 42E.

[0190] 〔Configuration of Partial Discharge Determination Device〕 FIG. 27 is a diagram showing the configuration of a partial discharge determination device according to a second embodiment of the present disclosure. Referring to FIG. 27, the partial discharge determination device 402 includes antennas 112A, 112B, and 112C instead of CTs 111A, 111B, and 111C, detection parts 122A, 122B, and 122C instead of the detection parts 121A, 121B, and 121C, a processing part 132 instead of the processing part 131, and a storage part 142 instead of the storage part 141 as compared with the partial discharge determination device 401. Hereinafter, each of the antennas 112A, 112B, and 112C is also referred to as the antenna 112, and each of the detection parts 122A, 122B, and 122C is also referred to as the detection part 122. Part or all of the detection part 122 and the processing part 132 are realized by, for example, a processing circuit including one or more processors. The storage part 142 is, for example, a non-volatile memory included in the above processing circuit.

[0191] (Antenna) Antenna 112 is, for example, a UHF (Ultra High Frequency) antenna. Antennas 112A, 112B, and 112C are respectively connected to detection units 122A, 122B, and 122C. For example, Antennas 112A, 112B, and 112C are respectively attached near underground cables 10A, 10B, and 10C on the old side of the insulation connection part 42.

[0192] Antenna 112A detects the current flowing through conductor 71 in underground cable 10A, and outputs an analog signal corresponding to the detected current to detection unit 122A. Also, Antenna 112B detects the current flowing through conductor 71 in underground cable 10B, and outputs an analog signal corresponding to the detected current to detection unit 122B. Also, Antenna 112C detects the current flowing through conductor 71 in underground cable 10C, and outputs an analog signal corresponding to the detected current to detection unit 122C.

[0193] (Detection Unit) Detection unit 122 monitors the current flowing through underground cable 10, and detects the occurrence of partial discharge in underground cable 10.

[0194] For example, detection unit 122 generates detection data D indicating the correspondence relationship between the phase P of the partial discharge current flowing through underground cable 10 with respect to the AC potential of commercial AC power, the charge amount Q of the current, and the frequency N of the appearance of the combination of phase P and charge amount Q, based on the analog signal received from the corresponding antenna 112.

[0195] More specifically, storage unit 141 stores a correspondence table Tb2 indicating the correspondence relationship between the level of the analog signal output from antenna 112 and the charge amount Q of the partial discharge current flowing through underground cable 10.

[0196] Detection unit 122 generates a digital detection signal by sampling the analog signal received from the corresponding antenna 112.

[0197] The detection unit 122 calculates the sampling timing of each sample value of the detection signal as the phase P with reference to the zero-crossing point Zp. Further, the detection unit 122 acquires the charge amount Q corresponding to the sample value of the detection signal from the correspondence table Tb2 in the storage unit 142. Note that the detection unit 122 may be configured to calculate the phase P based on an arbitrary point in time synchronized with the AC potential of commercial AC power instead of the zero-crossing point Zp.

[0198] The detection unit 122 generates detection data D, which is two-dimensional data representing the frequency count N as the appearance frequency, for each of the C sections S obtained by subdividing the value ranges of the phase P and the charge amount Q at the generation timing according to the generation period T1.

[0199] When the detection unit 122 generates the detection data D, it performs preprocessing to remove the background noise in the generated detection data D.

[0200] The detection unit 122 detects the occurrence of partial discharge in the underground cable 10 based on the detection data D after the preprocessing. When the detection unit 122 detects the occurrence of partial discharge in the underground cable 10, it stores the detection data Dpd indicating the correspondence relationship between the phase P of the current flowing through the underground cable 10 due to the occurrence of the partial discharge, the charge amount Q, and the frequency count N in the storage unit 142.

[0201] More specifically, for example, similar to the detection unit 121, the detection unit 122 determines whether partial discharge is occurring in the underground cable 10 based on the detection data D, and when it determines that partial discharge is occurring in the underground cable 10, it stores the detection data D as the detection data Dpd in the storage unit 142.

[0202] (Processing unit) The processing unit 132 acquires a plurality of detection data Dpd, which is the same number as the number of underground cables 10, indicating the correspondence relationship between the phase P, the charge amount Q, and the frequency N of the partial discharge current that flows through the underground cable 10 due to the occurrence of partial discharge. For example, the processing unit 131 acquires the detection data Dpd for each underground cable 10.

[0203] More specifically, when partial discharge occurs in any of the underground cables 10A, 10B, and 10C, the partial discharge current that flows through the underground cable 10 due to the occurrence of partial discharge propagates from the underground cable 10 where partial discharge has occurred to other underground cables 10 via the cross-bonding wire 16.

[0204] Therefore, when partial discharge occurs in any of the underground cables 10A, 10B, and 10C, the detection units 122A, 122B, and 122C determine that partial discharge is occurring in the underground cable 10, and store the detection data Dpd in which the occurrence of partial discharge has been detected in the storage unit 142. Hereinafter, the detection data Dpd generated by the detection units 122A, 122B, and 122C are also referred to as detection data Da2, Db2, and Dc2, respectively.

[0205] When the detection data Da2, Db2, and Dc2 are stored in the storage unit 142 by the detection units 122A, 122B, and 122C, the processing unit 132 acquires the detection data Da2, Db2, and Dc2 from the storage unit 142.

[0206] The processing unit 132 determines a partial discharge cable Cpd, which is the underground cable 10 in which partial discharge has occurred among the underground cables 10A, 10B, and 10C, based on the acquired detection data Da2, Db2, and Dc2.

[0207] (1) Determination of the maximum detection data Dmax The processing unit 132 determines the maximum detection data Dmax, which is the detection data Dpd with the highest detection intensity DI of the charge amount Q among the detection data Da2, Db2, and Dc2. More specifically, the processing unit 132 determines the maximum detection data Dmax according to the above-described determination example 1, determination example 2, or determination example 3, similar to the processing unit 131.

[0208] (2) Determination of the partial discharge cable Cpd The processing unit 132 determines the partial discharge cable Cpd based on the determination result of the maximum detection data Dmax. More specifically, the processing unit 132 determines that the underground cable 10 corresponding to the detection data Dpd determined to be the maximum detection data Dmax is the partial discharge cable Cpd. As an example, the processing unit 132 determines that the underground cable 10A corresponding to the detection data Da2 determined to be the maximum detection data Dmax is the partial discharge cable Cpd.

[0209] (3) Determination of the occurrence side Sd of the partial discharge Referring to FIG. 26 again, the processing unit 132 further determines the occurrence side Sd of the partial discharge with respect to the insulation connection portion 42 based on the determination result of the partial discharge cable Cpd.

[0210] For example, the processing unit 132 determines the occurrence cable 20pd, which is the cable 20 where the partial discharge has occurred, among the young-side cable 20 and the old-side cable 20 with respect to the insulation connection portion 42 as the occurrence side Sd of the partial discharge.

[0211] For example, the processing unit 132 determines the occurrence cable 20pd based on the comparison result between the charge amount Q in the detection data Da2 corresponding to the underground cable 10A, which is the partial discharge cable Cpd, and the charge amounts Q in the detection data Db2 and Dc2 corresponding to the underground cables 10B and 10C different from the underground cable 10A.

[0212] More specifically, in the underground cable 10A, when partial discharge occurs in the cable 20A1 on the old side, which is on the same side as the mounting position of the antenna 112A with respect to the insulation connection part 42, a partial discharge current propagates from the cable 20A1 on the old side to the cable 20A2 on the young side in the conductor 71 of the underground cable 10A, and when the partial discharge current flows through the conductor 71 of the cable 20A2, an induced current Ic1 flows through the shielding layer 75 of the cable 20A2. Then, when the induced current Ic1 propagates to the shielding layer 75 in the underground cable 10B via the cross bond wire 16A, a partial discharge current Ax, which is a current obtained by shunting the induced current Ic1, flows through the shielding layer 75 of the cable 20B1 on the old side in the underground cable 10B. The antenna 112B detects the partial discharge current Ax.

[0213] Also, in the underground cable 10A, when partial discharge occurs in the cable 20A1 on the old side with respect to the insulation connection part 42, an induced current Ic2 flows through the shielding layer 75 of the cable 20A1. Then, when the induced current Ic2 propagates to the shielding layer 75 in the underground cable 10C via the cross bond wire 16C, a partial discharge current Ay, which is a current induced by the induced current Ic2, flows through the conductor 71 of the cable 20C2 on the young side in the underground cable 10C. The antenna 112C detects the partial discharge current Ay that propagates from the young side to the old side in the conductor 71 of the underground cable 10C.

[0214] On the other hand, in the underground cable 10A, when partial discharge occurs in the cable 20A2 on the young side, which is on the opposite side of the mounting position of the antenna 112A with respect to the insulation connection part 42, a partial discharge current Az flows through the shielding layer 75 of the cable 20A2. Then, the partial discharge current Az propagates to the shielding layer 75 in the underground cable 10B via the cross bond wire 16A. The antenna 112B detects the partial discharge current Az.

[0215] Here, the partial discharge currents Ax and Ay are currents generated by induction between the conductor 71 and the shielding layer 75, and are also smaller than the partial discharge current Az due to the influence of the current attenuation in the insulating connection portion 42. Therefore, in the underground cable 10A, when partial discharge occurs in the cable 20A1 on the older side with respect to the insulating connection portion 42, the relative difference between the detection intensity DI of the charge amount Q in the detection data Da2 and the detection intensity DI of the charge amount Q in the detection data Db2 and Dc2 is large compared to the case where partial discharge occurs in the cable 20A2 on the younger side.

[0216] For example, when the absolute value of the difference Dd between the detection intensity DI of the charge amount Q in the detection data Da2 and the detection intensity DI in the detection data D with the larger detection intensity DI of the charge amount Q among the detection data Db2 and Dc2 is equal to or greater than a predetermined value, the processing unit 132 determines that the cable 20A1 on the older side among the cables 20A1 and 20A2 constituting the underground cable 10A is the occurrence cable 20pd.

[0217] On the other hand, when the absolute value of the difference Dd between the detection intensity DI of the charge amount Q in the detection data Da2 and the detection intensity DI in the detection data D with the larger detection intensity DI of the charge amount Q among the detection data Db2 and Dc2 is less than the predetermined value, the processing unit 132 determines that the cable 20A2 on the younger side among the cables 20A1 and 20A2 constituting the underground cable 10A is the occurrence cable 20pd.

[0218] Note that the processing unit 132 may calculate the ratio Rd between the detection intensity DI of the charge amount Q in the detection data Da2 and the detection intensity DI in the detection data D with the larger detection intensity DI of the charge amount Q among the detection data Db2 and Dc2 instead of the difference Dd, and determine the occurrence cable 20pd based on the calculated ratio Rd.

[0219] The processing unit 132 creates detection information including the cable ID of the underground cable 10 determined to be the partial discharge cable Cpd, the determination result of the occurrence side Sd, the detection data Dpd determined to be the maximum detection data Dmax, and the ID of the partial discharge determination device 402. The processing unit 132 transmits the created detection information to the communication device 411 using PLC communication.

[0220] The communication device 411 receives detection information from each partial discharge determination device 402 and transmits the received detection information to the estimation device 421 via the network 451.

[0221] The estimation device 421 performs an estimation process of estimating the partial discharge generation source in the underground cable 10 based on a plurality of detection information received from the communication device 411 via the network 451. More specifically, the estimation device 422 estimates the partial discharge generation source in the underground cable 10 based on a plurality of detection data Dpd generated by each partial discharge determination device 401. For example, the estimation device 422 estimates the occurrence section Prg by matching the determination results of the occurrence side Sd included in each received detection information. Also, for example, the estimation device 422 calculates the Q value of the detection data Dpd as described above, and adds a correction value taking into account the attenuation of the partial discharge current in the insulation connection part 42 to the Q value of the detection data Dpd included in the detection information according to the occurrence side Sd included in the detection information, and determines the maximum feature amount data Dpdmax based on the Q value added with the correction value. The correction value is determined for each partial discharge determination device 402 based on the detection data D generated by the detection unit 122 when a partial discharge current of a predetermined level flows through the conductor 71 in the underground cable 10 in advance. Then, the estimation device 421 further estimates at least one of the occurrence region Rpd and the occurrence position Ppd in the occurrence section Prg based on the determination results of the aligned data Dln and the maximum feature amount data Dpdmax.

[0222] [Operation flow] FIG. 28 is a flowchart defining an example of an operation procedure when the partial discharge determination according to the second embodiment of the present disclosure determines the partial discharge cable Cpd.

[0223] Referring to FIG. 28, first, the partial discharge determination device 402 starts monitoring the current flowing through the underground cable 10 (step S41).

[0224] Next, the partial discharge determination device 402 waits for the generation timing according to the generation period T1 (NO in step S42), and at the generation timing according to the generation period T1 (YES in step S42), generates detection data Da2, Db2, Dc2, and performs preprocessing on the generated detection data Da2, Db2, Dc2 (step S43).

[0225] Next, the partial discharge determination device 402 determines whether partial discharge has occurred in the underground cable 10 based on the preprocessed detection data Da2, Db2, Dc2 (step S44).

[0226] Next, when the partial discharge determination device 402 determines that no partial discharge has occurred in the underground cable 10 (NO in step S45), it discards the detection data Da2, Db2, Dc2 and waits for a new generation timing according to the generation period T1 (NO in step S42).

[0227] On the other hand, when the partial discharge determination device 402 determines that partial discharge has occurred in the underground cable 10 (YES in step S45), it determines the maximum detection data Dmax, which is the detection data D with the highest detection intensity DI of the charge amount Q among the detection data Da2, Db2, Dc2, according to the above-described determination example 1, determination example 2, or determination example 3 of the maximum detection data Dmax. As an example, the partial discharge determination device 402 determines that the detection data Da2 is the maximum detection data Dmax (step S46).

[0228] Next, the partial discharge determination device 402 determines that the underground cable 10A corresponding to the detection data Da2 determined to be the maximum detection data Dmax is the partial discharge cable Cpd (step S47).

[0229] Next, the partial discharge determination device 402 determines the occurrence side Sd of partial discharge with respect to the insulating connection portion 42 based on the comparison result between the detection intensity DI of the charge amount Q in the detection data Da2 corresponding to the underground cable 10A which is the partial discharge cable Cpd and the detection intensity DI of the charge amount Q in the detection data Da2 and Db2 (step S48).

[0230] Next, the partial discharge determination device 402 transmits detection information including the cable ID of the underground cable 10 determined to be the partial discharge cable Cpd, the determination result of the occurrence side Sd, the detection data Dpd determined to be the maximum detection data Dmax, and the ID of the partial discharge determination device 402 to the communication device 411 using PLC communication (step S49).

[0231] Next, the partial discharge determination device 402 waits for a new generation timing according to the generation period T1 (NO in step S42).

[0232] Note that in the partial discharge determination device 402 according to the second embodiment of the present disclosure, the processing unit 132 is configured to determine the occurrence side Sd of partial discharge, but is not limited thereto. The processing unit 132 may be configured not to determine the occurrence side Sd of partial discharge while determining the partial discharge cable Cpd.

[0233] Also, the partial discharge determination device 402 according to the second embodiment of the present disclosure is configured to include the antenna 112, but is not limited thereto. The partial discharge determination device 402 may be configured to include another sensor for detecting the current flowing through the conductor 71 in the underground cable 10, such as a TEV (Transient Earth Voltage) sensor, a flat capacitor, a Rogowski coil, and a metal foil electrode, instead of the antenna 112.

[0234] Also, in the partial discharge determination device 402 according to the second embodiment of the present disclosure, although the processing unit 132 is configured to determine the partial discharge cable Cpd based on a plurality of detection data D stored in the storage unit 142 by a plurality of detection units 122, the present disclosure is not limited thereto. The processing unit 132 may perform a correction process of scaling the charge amount Q in each detection data D based on a predetermined correction parameter created in advance for each antenna 112, and determine the partial discharge cable Cpd based on the plurality of detection data D after the correction process. The correction parameter is created in advance based on the charge amount Q of the detection data D generated by the detection unit 122 in each partial discharge determination device 401 when a predetermined level of calibration current is passed through the conductor 71 in the underground cable 10. Thereby, the influence of the individual variations of the antenna 112 and the detection unit 122 in the detection data D generated by each partial discharge determination device 401 can be reduced. Note that, instead of the processing unit 132 performing the correction process, the detection unit 122 may be configured to generate the detection data D using a correspondence table Tb2 corrected using the correction parameter.

[0235] Next, another embodiment 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.

[0236] <Third Embodiment> [Configuration and Basic Operation] This embodiment relates to a partial discharge detection system 503 that detects the occurrence of partial discharge in the normal connection part 41 as compared with the partial discharge detection system 501 according to the first embodiment. The partial discharge detection system 501 according to the first embodiment is the same as that described below except for the content described below.

[0237] FIG. 29 is a diagram showing the configuration of a power transmission system according to a third embodiment of the present disclosure. Referring to FIG. 29, the power transmission system 512 does not include the underground cables 10B and 10C and the insulation connection portion 42 as compared with the power transmission system 511. At least a part of the power transmission system 512 is provided, for example, in the underground portion of the power grid. In the power transmission system 512, as an example, a single-phase single-wire system is used as the power distribution method.

[0238] FIG. 30 is a diagram showing the configuration of a partial discharge detection system according to a third embodiment of the present disclosure. Referring to FIG. 30, the partial discharge detection system 503 includes partial discharge determination devices 403A, 403B, 403C, 403D, and 403E instead of the partial discharge determination device 401 as compared with the partial discharge detection system 501. Hereinafter, each of the partial discharge determination devices 403A, 403B, 403C, 403D, and 403E will also be referred to as the partial discharge determination device 403. Note that the partial discharge detection system 503 may be configured to include two, three, four, or six or more partial discharge determination devices 403. The partial discharge detection system 503 is used in the power transmission system 512.

[0239] The partial discharge determination device 403 is provided corresponding to the normal connection portion 41. More specifically, the partial discharge determination devices 403A, 403B, 403C, 403D, and 403E are respectively provided corresponding to the normal connection portions 41A, 41B, 41C, 41D, and 41E. The normal connection portions 41A, 41B, 41C, 41D, and 41E are provided in this order from the end of the underground cable 10A connected to the cable terminal 11A of the ground connection portion 43. That is, the normal connection portions 41A, 41B, 41C, 41D, and 41E are provided in this order from the younger side.

[0240] 〔Configuration of Partial Discharge Determination Device〕 FIG. 31 is a diagram showing an example of the configuration of a partial discharge determination device according to the third embodiment of the present disclosure. Referring to FIG. 31, the partial discharge determination device 403 includes a CT 113 instead of CTs 111A, 111B, and 111C, a detection unit 123 instead of detection units 121A, 121B, and 121C, a processing unit 133 instead of the processing unit 131, and a storage unit 143 instead of the storage unit 141, as compared with the partial discharge determination device 401. Part or all of the detection unit 123 and the processing unit 133 are realized by, for example, a processing circuit (Circuitry) including one or more processors. The storage unit 143 is, for example, a non-volatile memory included in the processing circuit.

[0241] (CT) CT 113 includes a ring core and a winding wound around the ring core. The winding in CT 113 is connected to the detection unit 123. CT 113 is attached so as to penetrate the underground cable 10A. For example, it is assumed that the winding directions of the windings of CT 113 in each partial discharge determination device 403 are the same.

[0242] When a current flows through the underground cable 10A, an induced current flows through the winding in CT 113 due to inductive coupling.

[0243] (Detection Unit) The detection unit 123 monitors the current flowing through the underground cable 10A and detects the occurrence of partial discharge in the underground cable 10A.

[0244] For example, the detection unit 123 generates detection data D indicating the correspondence relationship between the phase P of the current flowing through the underground cable 10A with respect to the alternating current potential of commercial alternating current power, the charge amount Q of the current, and the frequency N of the appearance of the combination of the phase P and the charge amount Q, based on the monitoring result of the induced current flowing through the winding in CT 113.

[0245] More specifically, the memory unit 143 stores a correspondence table Tb3 indicating the correspondence between the magnitude of the induced current flowing through the winding in CT113 and the charge amount Q of the current flowing through the underground cable 10A.

[0246] The detection unit 123 generates a digital detection signal by sampling the induced current flowing through the winding in CT113.

[0247] The detection unit 123 calculates the sampling timing of each sample value of the detection signal as the phase P with reference to the zero-crossing point Zp. Also, the detection unit 123 acquires the charge amount Q corresponding to the sample value of the detection signal from the correspondence table Tb3 in the memory unit 143. Note that the detection unit 123 may be configured to calculate the phase P based on an arbitrary point in time synchronized with the AC potential of commercial AC power instead of the zero-crossing point Zp.

[0248] At the generation timing according to the generation period T1, the detection unit 123 generates detection data D, which is two-dimensional data representing the frequency count N, for each of the C sections S obtained by subdividing the value ranges of the phase P and the charge amount Q.

[0249] When the detection unit 123 generates the detection data D, it performs preprocessing to remove the background noise in the generated detection data D.

[0250] The detection unit 123 detects the occurrence of partial discharge in the underground cable 10A based on the detection data D after preprocessing. When the detection unit 123 detects the occurrence of partial discharge in the underground cable 10A, it stores the detection data Dpd indicating the correspondence between the phase P, the charge amount Q, and the frequency count N of the current flowing through the underground cable 10A due to the occurrence of partial discharge in the memory unit 143.

[0251] More specifically, for example, similar to the detection unit 121, the detection unit 123 determines whether partial discharge has occurred in the underground cable 10A based on the detection data D. If it is determined that partial discharge has occurred in the underground cable 10A, the detection data D is stored in the storage unit 143 as the detection data Dpd.

[0252] (Processing unit) When the detection data Dpd is stored in the storage unit 143 by the detection unit 123, the processing unit 133 acquires the detection data Dpd from the storage unit 143.

[0253] The processing unit 133 creates detection information including the acquired detection data Dpd and the ID of the partial discharge determination device 403. The processing unit 133 transmits the created detection information to the communication device 411 using PLC communication.

[0254] The communication device 411 receives the detection information from each partial discharge determination device 403 and transmits the received detection information to the estimation device 421 via the network 451.

[0255] Based on the plurality of detection data Dpd generated by each partial discharge determination device 402, the estimation device 421 estimates the partial discharge source in the underground cable 10A. More specifically, the estimation device 422 estimates the occurrence section Prg and the like based on the detection information received from the communication device 411 via the network 451.

[0256] Note that although the partial discharge determination device 403 according to the third embodiment of the present disclosure is configured to include the CT113, it is not limited thereto. The partial discharge determination device 403 may be configured to include another sensor for detecting the current flowing through the shielding layer 75 and the ground wire 17, such as an antenna, instead of the CT113.

[0257] Further, the partial discharge determination device 403 may be configured to include an antenna for detecting the current flowing through the conductor 71 in the underground cable 10A, similar to the partial discharge determination device 402. The antenna is attached in the vicinity of the underground cable 10A on the older side or the younger side of the normal connection part 41.

[0258] Also, although the partial discharge detection system 503 according to the third embodiment of the present disclosure is configured to be used in the power transmission system 512, it is not limited thereto. The partial discharge detection system 503 may be used in the power transmission system 511. In this case, the partial discharge detection system 503 includes three partial discharge determination devices 403 corresponding to the three underground cables 10 for each normal connection part 41.

[0259] Also, in the partial discharge determination device 403 according to the third embodiment of the present disclosure, although CT113 is configured to be attached so as to penetrate the underground cable 10A, it is not limited thereto. CT113 may be attached such that the ground wire 17 in the normal connection part 41 of the underground cable 10A penetrates the ring core. In this case, the estimation device 421 estimates the occurrence position Ppd of partial discharge in the underground cable 10A based on the magnitude of the charge amount Q of the plurality of detection data Dpd generated by each partial discharge determination device 401.

[0260] It should be considered that the above embodiments are 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 are included.

[0261] Each process (each function) of the above-described embodiment is realized by a processing circuit including one or more processors. The above processing circuit may be configured by, in addition to the one or more processors, an integrated circuit in which one or more memories, various analog circuits, and various digital circuits are combined. The one or more memories store a program (instruction) for causing the one or more processors to execute each of the above processes. The one or more processors may execute each of the above processes according to the program read from the one or more memories, or may execute each of the above processes according to a logic circuit designed in advance to execute each of the above processes. The processor may be various processors suitable for controlling a computer, such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), and an ASIC (Application Specific Integrated Circuit). Note that the plurality of physically separated processors may cooperate with each other to execute each of the above processes. For example, the processors mounted on each of the plurality of physically separated computers may cooperate with each other via a network such as a LAN (Local Area Network), a WAN (Wide Area Network), and the Internet to execute each of the above processes. The program may be installed in the memory via the network from an external server device or the like, or may be distributed in a state stored in a recording medium such as a CD-ROM (Compact Disc Read Only Memory), a DVD-ROM (Digital Versatile Disk Read Only Memory), and a semiconductor memory, and may be installed in the memory from the recording medium.

Description of Reference Numerals

[0262] 10, 10A, 10A1, 10A2, 10B, 10B1, 10B2, 10C, 10C1, 10C2 underground cable Cable terminals 11A, 11B, 11C Cable 12 Grounding cable 14 Grounding nodes 13, 15 Grounding wire 17 Cross bond wires 16, 16A, 16B, 16C Manhole 31 Normal connection parts 41, 41A, 41B, 41C, 41D, 41E Insulated connection parts 42, 42A, 42B, 42C, 42D, 42E Above - ground connection parts 43, 44 Conductor 71 Internal semiconductive layer 72 Insulator 73 External semiconductive layer 74 Shielding layer 75 Sheath 76 Terminal 81 CTs 111, 111A, 111B, 111C, 113 Antennas 112, 112A, 112B, 112C Detection parts 121, 121A, 121B, 121C, 122, 122A, 122B, 122C, 123 Processing parts 131, 132, 133 Memory parts 141, 142, 143 Communication part (acquisition part) 211 Estimation part 221 Memory part 231 Partial discharge determination device (detection device) 401, 401A, 401B, 401C, 401D, 401E, 402, 402A, 402B, 402C, 402D, 402E, 403, 403A, 403B, 403C, 403D, 403E Communication device 411 Estimation device (partial discharge position estimation device) 421 Network 451 Partial discharge detection system 501, 502, 503 Power transmission system 511, 512 Detection data D, Dx, Dy, Dpd, Da1, Db1, Dc1, DpdA, DpdB, DpdC, DpdD, DpdE Th1, Th2 threshold Qm1, Qm2, Cmax maximum value Pmax phase TP test pattern R1, R2 interval Rd, Rd1, Rd2, Rd3, Rd4 detection interval

Claims

**Claim 1** A partial discharge position estimation device for estimating a partial discharge generation source in a cable having a linear conductor for transmitting commercial alternating current 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, comprising: Detection data showing a correspondence relationship between a phase of a partial discharge current, which is a current flowing through the cable during a predetermined period due to the occurrence of the partial discharge, with respect to an alternating current potential of the commercial alternating current power, a charge amount of the partial discharge current, and a frequency that is the appearance frequency of a combination of the phase and the charge amount, and an acquisition unit that acquires a plurality of the detection data respectively corresponding to a plurality of detection positions of the partial discharge current in the cable; A partial discharge position estimation device comprising an estimation unit that performs an estimation process for estimating the generation source based on the plurality of detection data acquired by the acquisition unit. **Claim 2** In the estimation process, the estimation unit estimates a generation section including a partial discharge generation position in the cable as the generation source. The estimation unit estimates any one of a detection section that is a section between the plurality of detection positions, a first section that is a section between the detection position at the first end among the plurality of detection positions and the first end of the cable, and a second section that is a section between the detection position at the second end among the plurality of detection positions and the second end of the cable as the generation section. The partial discharge position estimation device according to claim 1. **Claim 3** The estimation unit estimates any one of a plurality of the detection sections partitioned by three or more of the detection positions as the generation section based on the polarity of the charge amount in each of the detection data. The partial discharge position estimation device according to claim 2. **Claim 4** In the estimation process, the estimation unit further estimates a generation region including the partial discharge generation position in the generation section as the generation source. The estimation unit determines maximum feature amount data that is the detection data having the maximum feature amount of the charge amount among the plurality of detection data, and estimates the generation region based on a determination result of the maximum feature amount data. The partial discharge position estimation device according to claim 3. **Claim 5** The estimation unit acquires, for each of the detection data, the maximum value of the absolute value of the charge amount in the detection data as the feature amount, and determines that the detection data having the largest maximum value among the plurality of detection data is the maximum feature amount data. The partial discharge position estimation device according to claim 4.

6. The estimation unit acquires, for each of the detection data, the maximum value of the absolute value of the charge amount corresponding to the phase at which the total sum of the frequencies is maximum in the detection data as the feature amount, and determines that the detection data having the largest maximum value among the plurality of detection data is the maximum feature amount data. The partial discharge position estimation device according to claim 4.

7. The estimation unit acquires, for each of the detection data, the maximum value of the correlation coefficient between a predetermined test pattern indicating the correspondence relationship between the phase, the charge amount, and the frequency, and the detection data as the feature amount, and determines that the detection data having the largest maximum value among the plurality of detection data is the maximum feature amount data. The partial discharge position estimation device according to claim 4.

8. The cable has its shielding layer cross-bonded to other cables. The estimation unit estimates the source of the partial discharge for each cable based on information indicating the correspondence relationship between the cable and the detection data in the estimation process. The partial discharge position estimation device according to any one of claims 1 to 7.

9. A partial discharge position estimation system for estimating the source of partial discharge in a cable having a linear conductor for transmitting commercial alternating current 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 plurality of detection devices, and a partial discharge position estimation device, wherein the plurality of detection devices detect a partial discharge current, which is a current flowing through the cable during a predetermined period due to the occurrence of the partial discharge, at different detection positions in the cable, and generate detection data indicating the correspondence relationship between the phase of the detected partial discharge current with respect to the alternating current potential of the commercial alternating current power, the charge amount of the partial discharge current, and the frequency, which is the appearance frequency of the combination of the phase and the charge amount, and the partial discharge position estimation device performs an estimation process for estimating the source of the partial discharge based on the plurality of detection data generated by each of the detection devices. The partial discharge position estimation system.

10. The detection device determines the occurrence side of partial discharge with respect to the connection part between the conductors in the cable based on the detection data. The partial discharge position estimation system according to claim 9, wherein the partial discharge position estimation device estimates the generation source based on the determination result of the occurrence side by the detection device in the estimation process.

11. The detection device calculates a feature amount of the charge amount in the detection data. The partial discharge position estimation system according to claim 9 or claim 10, wherein the partial discharge position estimation device estimates the generation source based on the feature amount calculated by the detection device in the estimation process.

12. A partial discharge position estimation method in a partial discharge position estimation device for estimating a generation source of partial discharge in a cable having a linear conductor for transmitting commercial AC 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 step of acquiring a plurality of pieces of the detection data each corresponding to a plurality of detection positions of the partial discharge current in the cable, the detection data indicating a correspondence relationship between a phase of the partial discharge current, which is a current flowing through the cable during a predetermined period due to the occurrence of the partial discharge, with respect to an AC potential of the commercial AC power, a charge amount of the partial discharge current, and a frequency which is a frequency of appearance of a combination of the phase and the charge amount; a step of performing an estimation process of estimating the generation source based on the plurality of pieces of the acquired detection data.

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