Partial discharge determination device and partial discharge determination method

Abstract

To more accurately determine a cable where a partial discharge has occurred among a plurality of cables.SOLUTION: A partial discharge determination device that determines a cable where a partial discharge has occurred among a plurality of cables, comprises: an acquisition unit for acquiring a plurality of pieces of detection data of the same number as the number of the plurality of cables, the detection data indicating a relationship among the phase corresponding to the AC potential of commercial AC power of a partial discharge current flowing through the cable in a prescribed period from 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 a determination unit that determines the cable where the partial discharge has occurred among the plurality of cables on the basis of the plurality of pieces of detection data.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present disclosure relates to a partial discharge determination device and a partial discharge determination method.

Background Art

[0002] Conventionally, a technique has been proposed for detecting partial discharge in an underground cable and early detecting deterioration of an insulating layer based on the detection result of the partial discharge. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 8-152453) discloses the following partial discharge measurement method. That is, in the partial discharge measurement for detecting a partial discharge pulse signal from both sides of a metal shielding layer separated by an insulating cylinder of an electric power device, when the magnitude ratio of the peak height of the detection pulse of the measurement phase and the detection pulse of the other phase of the same line exceeds a predetermined set value, it is determined as partial discharge in the measurement phase.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Beyond the techniques described in Patent Documents 1 and 2, a technique capable of more accurately determining a cable in which partial discharge has occurred among a plurality of cables is desired.

[0005] The present disclosure has been made to solve the above-described problems, and an object thereof is to provide a partial discharge determination device and a partial discharge determination method capable of more accurately determining a cable in which partial discharge has occurred among a plurality of cables.

Means for Solving the Problems

[0006] The partial discharge determination device of the present disclosure is a partial discharge determination device that determines the cable in which partial discharge has occurred among a plurality of cables. The cable has 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, and the shielding layer is electrically cross-bonded to other cables. The partial discharge determination device includes 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 appearance of a combination of the phase and the charge amount. The partial discharge determination device includes an acquisition unit that acquires a plurality of pieces of the detection data equal in number to the number of the plurality of cables, and a determination unit that determines a partial discharge cable, which is the cable in which the partial discharge has occurred among the plurality of cables, 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 determination device including such a characteristic processing unit, but also as a program for causing a computer to execute 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 determination device, or can be realized as a system including the partial discharge determination device.

Advantages of the Invention

[0008] According to the present disclosure, it is possible to more accurately determine the cable in which partial discharge has occurred among a plurality of cables.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

DETAILED DESCRIPTION OF THE INVENTION

[0010] First, the contents of the embodiments of the present disclosure will be listed and described. (1) The partial discharge determination device according to an embodiment of the present disclosure is a partial discharge determination device that determines the cable in which partial discharge has occurred among a plurality of cables. The cable has 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 covering the periphery of the insulating layer, and the shielding layer is cross-bond connected to the shielding layers of the other cables. The partial discharge determination device includes 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 appearance of a combination of the phase and the charge amount. The partial discharge determination device further includes an acquisition unit that acquires a plurality of the detection data equal in number to the number of the plurality of cables, and a determination unit that determines a partial discharge cable, which is the cable in which the partial discharge has occurred among the plurality of cables, based on the plurality of detection data acquired by the acquisition unit.

[0011] In this way, 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 determining the partial discharge cable based on the detection data, it is possible to determine the partial discharge cable 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 determine the cable in which partial discharge has occurred among the plurality of cables.

[0012] (2) In the above (1), the determination unit may determine maximum detection data, which is the detection data having the maximum detection intensity of the charge amount among the plurality of detection data, and determine the partial discharge cable based on the determination result of the maximum detection data.

[0013] With such a configuration, since there is a difference in the intensity of the charge amount between the cable in which partial discharge has occurred and the other cables through which the partial discharge current has propagated via the cross-bond wire, it is possible to accurately determine the partial discharge cable.

[0014] (3) In the above (2), the determination unit may calculate, for each of the detection data, the maximum value of the absolute value of the charge amount in the detection data, and determine that the detection data having the largest maximum value among the plurality of detection data is the maximum detection data.

[0015] With such a configuration, the maximum detection data can be determined by simple processing.

[0016] (4) In the above (2), the determination unit may calculate, for each of the detection data, the maximum value of the absolute value of the charge amount corresponding to the phase at which the frequency is maximum in the detection data, and determine that the detection data having the largest maximum value among the plurality of detection data is the maximum detection data.

[0017] With such a configuration, the influence of sudden noise can be reduced, and the maximum detection data can be determined more accurately. Also, for example, compared with a configuration for determining the maximum detection data using a predetermined test pattern, the maximum detection data can be determined by simple processing.

[0018] (5) In the above (2), the determination unit may obtain a predetermined test pattern indicating the correspondence relationship between the phase, the charge amount, and the frequency, and the determination unit may calculate, for each of the detection data, the maximum value of the correlation coefficient between the detection data and the test pattern, and determine that the detection data having the largest maximum value among the plurality of detection data is the maximum detection data.

[0019] With such a configuration, for example, compared with a configuration for determining the maximum detection data based on the charge amount corresponding to the phase at which the frequency is maximum in the detection data, the influence of sudden noise can be further reduced, and the maximum detection data can be determined more accurately.

[0020] (6) In any one of (2) to (5) above, the acquisition unit may acquire, for each cable, the detection data indicating the correspondence relationship between the phase of the partial discharge current detected in the cable, the amount of charge, and the frequency, and the determination unit may determine that the cable corresponding to the maximum detection data is the partial discharge cable.

[0021] Thus, with a configuration in which detection data is acquired for each cable to determine the partial discharge cable, for example, compared with a configuration in which detection data is acquired for each cross bond wire to determine the partial discharge cable, the partial discharge cable can be determined more easily.

[0022] (7) In (6) above, the determination unit may further determine the occurrence side of partial discharge based on a reference to the connection portion between the conductors in the partial discharge cable, based on the comparison result between the amount of charge in the detection data corresponding to the partial discharge cable and the amount of charge in the detection data corresponding to the cable different from the partial discharge cable among the plurality of cables.

[0023] With such a configuration, the occurrence location of partial discharge in the cable can be determined in more detail, so that the maintenance cost of the cable can be further reduced.

[0024] (8) In any one of (2) to (5) above, the plurality of cables may be constituted by three cables of a three-phase three-wire system, and the acquisition unit may acquire, for each line, the detection data indicating the correspondence relationship between the phase of the partial discharge current detected in the line connecting the shielding layers of each of the two cables, the amount of charge, and the frequency, and the determination unit may, based on the phase of the potential of the conductors of the two cables to which the shielding layer is connected via the line corresponding to the maximum detection data and the phase corresponding to the detection intensity of the amount of charge in the maximum detection data, determine that one of the two cables to which the shielding layer is connected via the line corresponding to the maximum detection data is the partial discharge cable.

[0025] With such a configuration, among the plurality of cables connected by cross bonding, the partial discharge cable can be more accurately determined.

[0026] (9) In the above (8), the determination unit may further determine the occurrence side of partial discharge based on the connection portion between the conductors in the partial discharge cable with reference to the determination result of the maximum detection data and the determination result of the partial discharge cable.

[0027] With such a configuration, the location where partial discharge occurs in the cable can be determined in more detail, so that the maintenance cost of the cable can be further reduced.

[0028] (10) The partial discharge determination method according to an embodiment of the present disclosure is a partial discharge determination method in a partial discharge determination device that determines the cable in which partial discharge has occurred among a plurality of cables. The cable has 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 the shielding layer is cross-bonded to the shielding layer of another cable. The partial discharge determination 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 AC potential of the commercial AC power, a charge amount of the partial discharge current, and a frequency, which is the appearance frequency of a combination of the phase and the charge amount; and determining, based on the plurality of obtained detection data, the partial discharge cable, which is the cable in which the partial discharge has occurred among the plurality of cables.

[0029] In this way, by obtaining detection data indicating the correspondence between the phase of the partial discharge current, the charge amount of the partial discharge current, and the frequency, and determining the partial discharge cable based on the detection data, it is possible to determine the partial discharge cable 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 determine the cable in which partial discharge has occurred among a plurality of cables.

[0030] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and their descriptions will not be repeated. Also, at least a part of the embodiments described below may be arbitrarily combined.

[0031] <First Embodiment> [Configuration and Basic Operation] FIG. 1 is a diagram showing the configuration of a power transmission system according to the 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 insulation 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.

[0032] 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.

[0033] The ground connection parts 43 and 44 are provided, for example, at the part where the underground cable 10 appears on the ground within a substation. The normal connection part 41 and the insulating connection part 42 are provided, for example, inside the manhole 31.

[0034] 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 for transmitting commercial AC power, an internal semiconductive layer 72, an insulator 73 made of cross-linked polyethylene which is an insulating layer, an external semiconductive layer 74 which is 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 which is a conductor covers the periphery of the external semiconductive layer 74, and the sheath 76 covers the periphery of the shielding layer 75.

[0035] The conductor 71 in the underground cable 10 is used for power transmission and a high voltage is applied thereto. For example, the phase of the potential of the conductor 71 in the underground cable 10B is 120° behind the phase of the potential of the conductor 71 in the underground cable 10A. Also, for example, the phase of the potential of the conductor 71 in the underground cable 10C is 120° behind the phase of the potential of the conductor 71 in the underground cable 10B. The shielding layer 75 is conductive while being grounded in the middle of the underground cable 10. Therefore, the voltage of the shielding layer 75 is lower than that of the conductor 71.

[0036] 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, three-phase underground cables 10A, 10B, and 10C are provided as the three-phase underground cables 10. Hereinafter, the configuration of each part will be described in a simplified manner.

[0037] Referring back to FIG. 1, in cable terminals 11A, 11B, 11C, the shielding layers 75 of each of the underground cables 10A, 10B, 10C are exposed. Terminals are respectively provided at the connection portions between these shielding layers 75 and the grounding cable 14 or the like.

[0038] The underground cables 10A, 10B, 10C are respectively connected to the grounding node 15 at the cable terminals 11A, 11B, 11C. More specifically, the terminals provided on each of the underground cables 10A, 10B, 10C are connected to the grounding node 15 via the grounding cable 14 or the like, whereby the shielding layer 75 of each underground cable 10 is grounded.

[0039] For example, the underground cable 10 is composed of a plurality of cables whose ends are connected at the normal connection portion 41 and the insulated connection portion 42. More specifically, the underground cable 10 is composed of a plurality of cables whose conductors 71 are electrically connected at the normal connection portion 41 and the insulated connection portion 42.

[0040] FIG. 3 is a diagram showing an example of a method for connecting underground cables in a normal connection portion used in the power transmission system according to the first embodiment of the present disclosure. In FIG. 3, for ease of explanation, mainly the conductor 71 and the shielding layer 75 of the underground cable 10A are shown. The content described below is the same for the underground cable 10B and the underground cable 10C.

[0041] Referring to FIG. 3, in the normal connection portion 41, the cables 20A1, 20A2 which are the cables 20 constituting the underground cable 10A are connected. Assume that the cable 20A1 is on the younger side, that is, the starting side in power transmission. Assume that the cable 20A2 is on the older side, that is, the ending side in power transmission.

[0042] In the ordinary 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 ordinary connection part 41, the shielding layer 75 of the cable 20A1 and the shielding layer 75 of the cable 20A2 are connected, for example, using a connection cable 12.

[0043] 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 a grounding cable 14, the shielding layer 75 of the underground cable 10A is grounded.

[0044] FIG. 4 is a diagram showing an example of a method for connecting an underground cable in an insulating connection part used in a power transmission system according to the first embodiment of the present disclosure. Referring to FIG. 4, in the insulating connection part 42, the cables 20A1 and 20A2 are connected, the cables 20B1 and 20B2, which are the cables 20 constituting the underground cable 10B, are connected, and the cables 20C1 and 20C2, which are the cables 20 constituting the underground cable 10C, are connected. The cables 20A1, 20B1, and 20C1 are assumed to be the younger side. The cables 20A2, 20B2, and 20C2 are assumed to be the older side.

[0045] In the insulating connection part 42, 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, the shielding layers 75 of the cables 20B1 and 20B2 are exposed at the connection part between the conductors 71 of the cables 20B1 and 20B2, the shielding layers 75 of the cables 20C1 and 20C2 are exposed at the connection part between the conductors 71 of the cables 20C1 and 20C2, and terminals 81 and the like are respectively provided at the exposed parts.

[0046] For example, in the underground cable 10, at the insulating connection part 42, the shielding layer 75 is cross-bond connected 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-bond wire 16A, the shielding layer 75 of the cable 20A2 and the shielding layer 75 of the cable 20B1 are connected.

[0047] Also, by connecting the terminal 81 in the cable 20B2 and the terminal 81 in the cable 20C1 with the cross-bond wire 16B, the shielding layer 75 of the cable 20B2 and the shielding layer 75 of the cable 20C1 are connected.

[0048] Also, by connecting the terminal 81 in the cable 20C2 and the terminal 81 in the cable 20A1 with the cross-bond wire 16C, the shielding layer 75 of the cable 20C2 and the shielding layer 75 of the cable 20A1 are connected.

[0049] Hereinafter, each of the cross-bond wires 16A, 16B, and 16C is also referred to as the cross-bond wire 16. The cross-bond wire 16 is an example of a line connecting the shielding layer 75 of each of the two underground cables 10.

[0050] [Partial Discharge Judgment System] FIG. 5 is a diagram showing the configuration of a partial discharge detection system according to the first embodiment of the present disclosure. Referring to FIG. 5, the partial discharge detection system 501 includes a partial discharge judgment device 401. For example, the partial discharge judgment device 401 is provided corresponding to the insulating connection part 42. Note that the partial discharge detection system 501 may be configured to include a plurality of partial discharge judgment devices 401 provided corresponding to a plurality of insulating connection parts 42 respectively. The partial discharge detection system 501 is used in the power transmission system 511.

[0051] For example, a power supply coil Cpow (not shown) is attached to the underground cable 10. An induced current flows through the power supply coil Cpow due to the current flowing through the conductor 71 of the underground cable 10. As a result, the power supply coil Cpow can extract current. The partial discharge determination device 401 operates, for example, using the power obtained by the power supply coil Cpow.

[0052] The partial discharge determination device 401 determines the underground cable 10 in which partial discharge has occurred among the underground cables 10A, 10B, and 10C. Note that the partial discharge determination device 401 may be configured to determine the occurrence of partial discharge in cables other than the underground cable 10, such as cables laid on a bridge.

[0053] [Configuration of Partial Discharge Determination Device] FIG. 6 is a diagram showing the configuration of a partial discharge determination device according to the first embodiment of the present disclosure. Referring to FIG. 6, 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. The processing unit 131 is an example of an acquisition unit and also an example of a determination unit. Part or all of the detection unit 121 and the processing unit 131 are realized by, for example, a processing circuit (Circuitry) including one or more processors. The storage unit 141 is, for example, a non-volatile memory included in the above processing circuit.

[0054] (CT) The CT111 includes a ring core and a winding wound around the ring core. The number of turns of the winding in the ring core is, for example, from 1 to 7 turns. The windings in the CTs 111A, 111B, 111C are respectively connected to the detection units 121A, 121B, 121C. The CTs 111A, 111B, 111C are respectively attached such that the cross bond wires 16A, 16B, 16C in the insulation connection part 42 penetrate the ring core.

[0055] When current flows through the cross bond wire 16A that connects 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 the CT111A due to inductive coupling.

[0056] Also, when current flows through the cross bond wire 16B that connects 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 the CT111B due to inductive coupling.

[0057] Also, when current flows through the cross bond wire 16C that connects 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 the CT111C due to inductive coupling.

[0058] (Detection unit) The detection unit 121 monitors the current flowing through the shielding layer 75 of the underground cable 10 and the cross bond wire 16, and detects the occurrence of partial discharge in the underground cable 10.

[0059] More specifically, the detection unit 121A monitors the induced current flowing through the winding in the CT111A. Also, the detection unit 121B monitors the induced current flowing through the winding in the CT111B. Also, the detection unit 121C monitors the induced current flowing through the winding in the CT111C.

[0060] Based on the monitoring result of the induced current flowing through the winding in the corresponding CT111, 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 of the underground cable 10 and the cross bond wire 16 with respect to the AC potential of the commercial AC 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.

[0061] More specifically, the memory unit 141 stores a correspondence table Tb1 indicating the correspondence between the magnitude of the induced current flowing through the winding in CT111 and the charge amount Q of the current flowing through the shielding layer 75 and the cross bond wire 16.

[0062] Further, the processing unit 131 extracts the frequency component of the commercial alternating current 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 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 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.

[0063] 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 correspondence table Tb1 in the memory unit 141.

[0064] Further, 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 into the phase P based on the zero-crossing point ZpA. The detection unit 121B converts the sampling timing into the phase P based on the zero-crossing point ZpB. The detection unit 121C converts the sampling timing into the phase P based on the zero-crossing point ZpC.

[0065] The detection unit 121 generates detection data D, which is two-dimensional data representing the frequency count N of appearance for each of C sections S obtained by subdividing the value ranges of the converted phase P and the acquired charge amount Q at generation timings 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.

[0066] 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 count N of the section S in which the charge amount Q is included in a predetermined region near zero to a smaller value in the detection data D. The detection unit 121 may correct the frequency count N of the section S included in the predetermined region to zero, or may correct it to a value other than zero.

[0067] Note that the detection unit 121 is not limited to a configuration in which the phase P is calculated using the zero-crossing point Zp notified from the processing unit 131, and any configuration may be used as long as it can calculate 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 CT111, 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.

[0068] Figures 7 and 8 are diagrams showing an example of detection data D after preprocessing generated by a detection unit in a partial discharge determination device according to a first embodiment of the present disclosure. Figures 7 and 8 show detection data D represented in orthogonal coordinates with phase P and charge amount Q as coordinate axes. Figure 7 shows detection data Dx, which is detection data in a state where no partial discharge occurs in the underground cable 10. Figure 8 shows detection data Dy, which is detection data in a state where partial discharge has occurred in the underground cable 10.

[0069] In Figures 7 and 8, the horizontal axis represents phase P [degree], and the vertical axis represents charge amount Q [pC]. In Figures 7 and 8, in the two-dimensional coordinates of phase P and charge amount Q, a target area where phase P ranges from 0° to 360° and charge amount Q ranges from, for example, -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 Figures 7 and 8, for convenience, the section S with degree N equal to zero is displayed in white, and the section S with degree N of 1 or more is displayed in black. The same applies to the subsequent figures.

[0070] Referring to Figures 7 and 8, compared with detection data Dx, detection data Dy has a larger ratio of sections S in which the charge amount Q is greater than or equal to a predetermined threshold Th1 or the charge amount Q is less than or equal to a predetermined threshold Th2 among the sections S with degree N of 1 or more. Here, the threshold Th1 is a value greater than zero, and the threshold Th2 is a value less than zero. Also, in detection data Dy, the absolute value of the charge amount Q increases in a cycle of 180°.

[0071] 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, it stores the detection data D showing 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 degree N in the storage unit 141.

[0072] More specifically, for example, in the generated detection data D, when in the section S where the charge amount Q is equal to or greater than the threshold Th1 and the number of sections S where the frequency N is equal to or greater than a predetermined value is equal to or greater than a predetermined number, and in the section S where the charge amount Q is equal to or less than the threshold Th2 and the number of sections S where the frequency N is equal to or greater than a predetermined value is equal to or greater than a predetermined number, it is determined whether the charge amount Q has a periodicity of 180°.

[0073] 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°, it is determined 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°, it is determined that the charge amount Q in the detection data D does not have a periodicity of 180°.

[0074] When the detection unit 121 determines that the charge amount Q in the detection data D has a periodicity of 180°, it is determined that partial discharge has occurred in the underground cable 10. In this case, the detection unit 121 stores the detection data D in which the occurrence of partial discharge has been detected in the storage unit 141.

[0075] On the other hand, 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 less than a predetermined number, or 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 less than a predetermined number, or when it is determined that the charge amount Q in the detection data D does not have a periodicity of 180°, it is determined 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.

[0076] (Processing unit) The processing unit 131 acquires a plurality of pieces of detection data D indicating the correspondence relationships among the phase P, charge amount Q, and frequency N 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, and the number of the plurality of pieces of detection data D is the same as the number of the underground cables 10. For example, the processing unit 131 acquires the detection data D for each cross-bonding wire 16.

[0077] More specifically, when partial discharge occurs in any of the underground cables 10A, 10B, and 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 partial discharge has occurred to other underground cables 10 via the cross-bonding wire 16.

[0078] Therefore, when partial discharge occurs in any of the underground cables 10A, 10B, and 10C, a plurality of detection units 121 may determine that partial discharge is occurring in the underground cable 10 and save the detection data D in which the occurrence of partial discharge has been detected in the storage unit 141. Hereinafter, the detection data D generated by the detection units 121A, 121B, and 121C are also referred to as detection data Da1, Db1, and Dc1, respectively.

[0079] When a plurality of pieces of detection data D are respectively stored in the storage unit 141 by a plurality of detection units 121, the processing unit 131 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, based on the plurality of pieces of detection data D.

[0080] FIGS. 9 to 11 are diagrams showing an example of the detection data D stored in the storage unit by the detection unit in the partial discharge determination device according to the first embodiment of the present disclosure. FIGS. 9 to 11 respectively show the detection data Da1, Db1, and Dc1.

[0081] Referring to FIGS. 9 to 11, when the 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.

[0082] Based on the acquired detection data Da1, Db1, and Dc1, the processing unit 131 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.

[0083] (1) Determination of the maximum detection data Dmax The processing unit 131 determines the maximum detection data Dmax, which is the detection data D with the highest detection intensity DI of the charge quantity Q among the detection data Da1, Db1, and Dc1. Based on the determination result of the maximum detection data Dmax, the processing unit 131 determines the partial discharge cable Cpd.

[0084] (1-1) First example of determining the maximum detection data Dmax The processing unit 131 calculates the maximum value Qm1 of the absolute value of the charge quantity Q represented by the section S where the frequency N is equal to or greater than a predetermined value in the detection data D. 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 D and determines that the detection data D with the largest maximum value Qm1 among the detection data Da1, Db1, and Dc1 is the maximum detection data Dmax.

[0085] In the example shown in FIGS. 9 to 11, the processing unit 131 determines that the detection data Da1 with the largest maximum value Qm1 among the detection data Da1, Db1, and Dc1 is the maximum detection data Dmax.

[0086] (1-2) Second example of determining the maximum detection data Dmax The processing unit 131 calculates the sum of the frequencies N for each phase P in the detection data D, and calculates the maximum value Qm2 of the absolute value of the charge quantity Q corresponding to the phase Pmax where 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 D and determines that the detection data D with the largest maximum value Qm2 among the detection data Da1, Db1, and Dc1 is the maximum detection data Dmax.

[0087] In the example shown in FIGS. 9 to 11, the processing unit 131 determines that the detection data Da1 with the largest maximum value Qm2 among the detection data Da1, Db1, and Dc1 is the maximum detection data Dmax.

[0088] (1-3) Example 3 of determination of maximum detection data Dmax FIG. 12 is a diagram showing an example of a test pattern TP stored in a storage unit in the partial discharge determination device according to the first embodiment of the present disclosure. FIG. 12 shows a test pattern TP represented in orthogonal coordinates with the phase P and the charge amount Q as coordinate axes. In FIG. 12, 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.

[0089] Referring to FIG. 12, 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 D when partial discharge occurs in the underground cable 10 and 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.

[0090] 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 D and the test pattern TP for each detection data D. The maximum value Cmax is an example of the detection intensity DI.

[0091] FIG. 13 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. 13 shows a method for calculating the correlation coefficient CC between the detection data Da1 and the test pattern TP.

[0092] Referring to FIG. 13, the processing unit 131 performs normalization processing on the detection data Da1, for example, 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.

[0093] The processing unit 131 calculates the correlation coefficient CC for each lag L while changing the lag L, which is the phase shift of the phase P of the test pattern TP with respect to the phase P of the detection data Da1, from 0° to 360°.

[0094] FIG. 14 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. 14, the horizontal axis is the lag L and the vertical axis is the correlation coefficient CC. FIG. 14 shows the calculation result of the correlation coefficient CC between the detection data Da1 and the test pattern TP.

[0095] Referring to FIG. 14, 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 acquires the maximum value Cmax of the correlation coefficient CC between the detection data Da1 and the test pattern TP.

[0096] 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 acquires the maximum value Cmax of the correlation coefficient CC between the detection data Db, Dc and the test pattern TP respectively.

[0097] Then, the processing unit 131 determines that the detection data D with the largest maximum value Cmax among the detection data Da1, Db1, Dc1 is the maximum detection data Dmax.

[0098] In the example shown in FIGS. 9 to 11, among the detection data Da1, Db1, and Dc1, the detection data D for which the maximum value Cmax is the largest is the detection data Da1. The processing unit 131 determines that the detection data Da1 for which the maximum value Cmax among the detection data Da1, Db1, and Dc1 is the largest is the maximum detection data Dmax.

[0099] (2) Determination of the partial discharge cable Cpd FIG. 15 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. 15 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.

[0100] Referring to FIG. 15, 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.

[0101] 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 respect to the zero crossing point ZpA, 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 respect to the zero crossing point ZpA, 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.

[0102] 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.

[0103] For example, the processing unit 131 determines that one of the underground cables 10A and 10B is the 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-bond 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.

[0104] 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.

[0105] 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 generation 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.

[0106] (3) Determination of the occurrence side Sd of partial discharge Referring to FIG. 5 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.

[0107] For example, as the occurrence side Sd of partial discharge, the processing unit 131 determines the occurrence cable 20pd, which is the cable 20 in which 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.

[0108] 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, it determines that the cable 20A2, which constitutes the underground cable 10A, among the cable 20A2 and the cable 20B1 connected using the cross bond line 16A corresponding to the detection data Da1, is the occurrence cable 20pd.

[0109] 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 that constitutes the underground cable 10B among the cables 20A2 and 20B1 that are connected using the cross bond wire 16A corresponding to the detection data Da1 is the generated cable 20pd.

[0110] 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 that constitutes the partial discharge cable Cpd among the two cables 20 that are connected using the cross bond wire 16 corresponding to the maximum detection data Dmax is the generated cable 20pd.

[0111] For example, the processing unit 131 notifies the determination result of the partial discharge cable Cpd to a server (not shown) using PLC (Power Line Communication). More specifically, 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 D determined to be the maximum detection data Dmax, and the ID of the partial discharge determination device 401. The processing unit 131 notifies the created detection information to the server using PLC.

[0112] [Flow of operation] FIG. 16 is a flowchart defining an example of an operation procedure when the partial discharge determination according to the first embodiment of the present disclosure performs the determination of the partial discharge cable Cpd.

[0113] Referring to FIG. 16, 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).

[0114] 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 pre-processing on the generated detection data Da1, Db1, Dc1 (step S13).

[0115] Next, the partial discharge determination device 401 determines whether or not partial discharge has occurred in the underground cable 10 based on the detection data Da1, Db1, Dc1 after pre-processing (step S14).

[0116] 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).

[0117] 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).

[0118] 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).

[0119] 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).

[0120] Next, the partial discharge determination device 401 notifies the server of the determination result of the partial discharge cable Cpd (step S19).

[0121] Next, the partial discharge determination device 401 waits for a new generation timing according to the generation period T1 (NO in step S12).

[0122] Note that in the partial discharge determination device 401 according to the first embodiment of the present disclosure, although the detection unit 121 is configured to perform preprocessing of the detection data D, the present disclosure is not limited thereto. The detection unit 121 may be configured not to perform preprocessing of the detection data D.

[0123] Also, although the partial discharge determination device 401 according to the first embodiment of the present disclosure is configured to include the CT111 and the detection unit 121, the present disclosure is not limited thereto. The partial discharge determination device 401 may be configured not to include the CT111 and the detection unit 121. In this case, the processing unit 131 acquires detection data D indicating the correspondence relationship between the phase P, the charge amount Q, and the frequency N of the partial discharge current flowing through the underground cable 10 due to the occurrence of partial discharge from a device outside the partial discharge determination device 401.

[0124] Also, although the partial discharge determination device 401 according to the first embodiment of the present disclosure is configured to include the CT111, the present disclosure 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 CT111.

[0125] 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 notify the server of the determination result of the partial discharge cable Cpd (not shown), the present disclosure is not limited thereto. Instead of notifying the server of the determination result, the processing unit 131 may be configured to save the determination result in a storage device, such as a USB (Universal Serial Bus) memory, that is insertable into the partial discharge determination device 401.

[0126] Further, 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 the plurality of detection units 121, the present disclosure is not limited thereto. The processing unit 131 may be configured to perform correction processing for scaling the charge amount Q in each detection data D based on a predetermined correction parameter created in advance for each CT111, and determine the partial discharge cable Cpd based on the plurality of detection data D after the correction processing. 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 when a calibration current of a predetermined level is passed through the cross bond wire 16. Thereby, the influence of the individual variations of CT111 and the detection unit 121 in the detection data D can be reduced. Note that, instead of the processing unit 131 performing the correction processing, the detection unit 121 may be configured to generate the detection data D using the corresponding table Tb1 corrected using the correction parameter.

[0127] Further, 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, the present disclosure is not limited thereto. The processing unit 131 may be configured not to determine the occurrence side Sd of the partial discharge while determining the partial discharge cable Cpd.

[0128] 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 determining the underground cable 10 in which partial discharge has occurred among the plurality of underground cables 10 is desired.

[0129] More specifically, in the techniques described in Patent Documents 1 and 2, the underground cable 10 in which partial discharge has occurred is determined based on the intensity of a single partial discharge pulse. However, in the techniques described in Patent Documents 1 and 2, it may not be possible to accurately determine the underground cable 10 in which partial discharge has occurred due to the influence of variations in the intensity of the partial discharge pulse and the influence of noise.

[0130] In contrast, in the partial discharge determination device 401 according to the first embodiment of the present disclosure, the processing unit 131 obtains detection data D showing 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 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 number of pieces of detection data D is the same as the number of the plurality of underground cables 10. The processing unit 131 determines a partial discharge cable Cpd, which is the underground cable 10 in which partial discharge has occurred among the plurality of underground cables 10, based on the plurality of pieces of obtained detection data D.

[0131] In this way, by obtaining the detection data D showing the correspondence relationship between the phase P, the charge amount Q, and the frequency N, and determining the partial discharge cable based on the detection data D, it is possible to determine the partial discharge cable while reducing the influence of noise based on the detection data D in which the characteristics of partial discharge are statistically represented. Therefore, it is possible to more accurately determine the underground cable 10 in which partial discharge has occurred among the plurality of underground cables 10.

[0132] Next, other embodiments 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 their descriptions will not be repeated.

[0133] <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. It is the same as the partial discharge detection system 501 according to the first embodiment except for the content described below.

[0134] [Partial Discharge Determination System] FIG. 17 is a diagram showing the configuration of a partial discharge detection system according to a second embodiment of the present disclosure. Referring to FIG. 17, the partial discharge detection system 502 includes a partial discharge determination device 402 instead of the partial discharge determination device 401 as compared with the partial discharge detection system 501. For example, the partial discharge determination device 402 is provided in the insulation connection portion 42. Note that the partial discharge detection system 501 may be configured to include a plurality of partial discharge determination devices 402 provided corresponding to a plurality of insulation connection portions 42, respectively. The partial discharge detection system 501 is used in the power transmission system 511.

[0135] [Configuration of Partial Discharge Determination Device] FIG. 18 is a diagram showing the configuration of a partial discharge determination device according to a second embodiment of the present disclosure. Referring to FIG. 18, the partial discharge determination device 402 includes antennas 112A, 112B, 112C instead of CTs 111A, 111B, 111C, detection units 122A, 122B, 122C instead of detection units 121A, 121B, 121C, a processing unit 132 instead of the processing unit 131, and a storage unit 142 instead of the storage unit 141 as compared with the partial discharge determination device 401. Hereinafter, each of the antennas 112A, 112B, 112C is also referred to as an antenna 112, and each of the detection units 122A, 122B, 122C is also referred to as a detection unit 122. The processing unit 132 is an example of an acquisition unit and also an example of a determination unit. Part or all of the detection unit 122 and the processing unit 132 are realized by, for example, a processing circuit including one or more processors. The storage unit 142 is, for example, a non-volatile memory included in the above processing circuit.

[0136] (Antenna) The antenna 112 is, for example, a UHF (Ultra High Frequency) antenna. The antennas 112A, 112B, 112C are respectively connected to the detection units 122A, 122B, 122C. For example, the antennas 112A, 112B, 112C are respectively attached in the vicinity of the underground cables 10A, 10B, 10C on the old side of the insulation connection portion 42.

[0137] Antenna 112A detects the current flowing through conductor 71 in underground cable 10A, and outputs an analog signal corresponding to the detected current to detector 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 detector 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 detector 122C.

[0138] (Detector) Detector 122 monitors the current flowing through underground cable 10, and detects the occurrence of partial discharge in underground cable 10.

[0139] For example, detector 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 which is the appearance frequency of the combination of phase P and charge amount Q, based on the analog signal received from the corresponding antenna 112.

[0140] More specifically, storage unit 141 stores 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.

[0141] Detector 122 generates a digital detection signal by sampling the analog signal received from the corresponding antenna 112.

[0142] Detector 122 calculates the sampling timing of each sample value of the detection signal as phase P with reference to the zero-crossing point Zp. Also, detector 122 acquires the charge amount Q corresponding to the sample value of the detection signal from correspondence table Tb2 in storage unit 142. Note that detector 122 may be configured to calculate phase P with reference to an arbitrary point in time synchronized with the AC potential of commercial AC power instead of the zero-crossing point Zp.

[0143] At the generation timing according to the generation period T1, the detection unit 122 generates detection data D, which is two-dimensional data representing the frequency count N as the frequency of occurrence for each of the C sections S obtained by subdividing the value ranges of the phase P and the charge amount Q.

[0144] When the detection unit 122 generates the detection data D, it performs preprocessing to remove background noise in the generated detection data D.

[0145] Based on the detection data D after preprocessing, the detection unit 122 detects the occurrence of partial discharge in the underground cable 10. When the detection unit 122 detects the occurrence of partial discharge in the underground cable 10, it stores in the storage unit 142 the detection data D indicating the correspondence relationship among 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 count N.

[0146] 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. When it is determined that partial discharge is occurring in the underground cable 10, it stores in the storage unit 142 the detection data D in which the occurrence of partial discharge has been detected.

[0147] (Processing unit) The processing unit 132 acquires a plurality of detection data D, which is the detection data D indicating the correspondence relationship among the phase P of the partial discharge current, which is the current flowing through the underground cable 10 due to the occurrence of partial discharge, the charge amount Q, and the frequency count N, and the number of detection data D is the same as the number of underground cables 10. For example, the processing unit 131 acquires the detection data D for each underground cable 10.

[0148] 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 in which partial discharge has occurred to other underground cables 10 via the cross-bonding wire 16.

[0149] Therefore, when partial discharge occurs in any of the underground cables 10A, 10B, 10C, the detection units 122A, 122B, 122C determine that partial discharge is occurring in the underground cable 10, and store the detection data D in which the occurrence of partial discharge has been detected in the storage unit 142. Hereinafter, the detection data D generated by the detection units 122A, 122B, 122C are also referred to as detection data Da2, Db2, Dc2, respectively.

[0150] FIGS. 19 to 21 are diagrams showing an example of detection data D stored in a storage unit by a detection unit in a partial discharge determination device according to a second embodiment of the present disclosure. FIGS. 19 to 21 show detection data Da2, Db2, Dc2, respectively.

[0151] Referring to FIGS. 19 to 21, when the detection data Da2, Db2, Dc2 are stored in the storage unit 142 by the detection units 122A, 122B, 122C, the processing unit 132 acquires the detection data Da2, Db2, Dc2 from the storage unit 142.

[0152] Based on the acquired detection data Da2, Db2, Dc2, the processing unit 132 determines a partial discharge cable Cpd that is the underground cable 10 in which partial discharge has occurred among the underground cables 10A, 10B, 10C.

[0153] (1) Determination of maximum detection data Dmax The processing unit 132 determines a maximum detection data Dmax that is the detection data D having the maximum detection intensity DI of the charge amount Q among the detection data Da2, Db2, 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 in the same manner as the processing unit 131. For example, in the example shown in FIGS. 19 to 21, the processing unit 132 determines that the detection data Da2 is the maximum detection data Dmax.

[0154] (2) Determination of partial discharge cable Cpd The processing unit 132 determines the partial discharge cable Cpd based on the determination result of the maximum detected data Dmax. More specifically, the processing unit 132 determines that the underground cable 10A corresponding to the detected data Da2 determined to be the maximum detected data Dmax is the partial discharge cable Cpd.

[0155] (3) Determination of the occurrence side Sd of partial discharge Referring to FIG. 17 again, the processing unit 132 further determines the occurrence side Sd of partial discharge with respect to the insulation connection portion 42 based on the determination result of the partial discharge cable Cpd.

[0156] For example, the processing unit 132 determines, as the occurrence side Sd of partial discharge, the occurrence cable 20pd which is the cable 20 in which 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.

[0157] For example, the processing unit 132 determines the occurrence cable 20pd based on the comparison result between the charge amount Q in the detected data Da2 corresponding to the underground cable 10A which is the partial discharge cable Cpd and the charge amounts Q in the detected data Db2 and Dc2 corresponding to the underground cables 10B and 10C different from the underground cable 10A.

[0158] More specifically, in the underground cable 10A, when partial discharge occurs in the old-side cable 20A1 on the same side as the attachment position of the antenna 112A with respect to the insulation connection portion 42, the partial discharge current in the conductor 71 of the underground cable 10A propagates from the old-side cable 20A1 to the young-side cable 20A2, and the partial discharge current flows through the conductor 71 of the cable 20A2, so that the induced current Ic1 flows through the shielding layer 75 of the cable 20A2. Then, the induced current Ic1 propagates through the cross bond wire 16A to the shielding layer 75 in the underground cable 10B, and the partial discharge current Ax which is the current obtained by shunting the induced current Ic1 flows through the shielding layer 75 of the old-side cable 20B1 in the underground cable 10B. The antenna 112B detects the partial discharge current Ax.

[0159] Also, in the underground cable 10A, when partial discharge occurs in the cable 20A1 on the older side with respect to the insulation connection portion 42, an induced current Ic2 flows through the shielding layer 75 of the cable 20A1. Then, the induced current Ic2 propagates to the shielding layer 75 in the underground cable 10C through the cross bond wire 16C, and 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 younger side in the underground cable 10C. The antenna 112C detects the partial discharge current Ay that has propagated from the younger side to the older side in the conductor 71 of the underground cable 10C.

[0160] On the other hand, in the underground cable 10A, when partial discharge occurs in the cable 20A2 on the younger side, which is the side opposite to the attachment position of the antenna 112A with respect to the insulation connection portion 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 through the cross bond wire 16A. The antenna 112B detects the partial discharge current Az.

[0161] Here, the partial discharge currents Ax and Ay are currents generated by induction between the conductor 71 and the shielding layer 75, and are smaller than the partial discharge current Az due to the influence of current attenuation in the insulation connection portion 42. Therefore, when partial discharge occurs in the cable 20A1 on the older side with respect to the insulation connection portion 42 in the underground cable 10A, 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 when partial discharge occurs in the cable 20A2 on the younger side.

[0162] 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, which is the detection data 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 cable 20pd where the partial discharge has occurred.

[0163] 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 a predetermined value, the processing unit 132 determines that the younger cable 20A2 among the cables 20A1 and 20A2 constituting the underground cable 10A is the generated cable 20pd.

[0164] 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 generated cable 20pd based on the calculated ratio Rd.

[0165] [Operation flow] FIG. 22 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.

[0166] Referring to FIG. 22, first, the partial discharge determination device 402 starts monitoring the current flowing through the underground cable 10 (step S21).

[0167] Next, the partial discharge determination device 402 waits for the generation timing according to the generation period T1 (NO in step S22), and at the generation timing according to the generation period T1 (YES in step S22), generates the detection data Da2, Db2, and Dc2, and performs preprocessing on the generated detection data Da2, Db2, and Dc2 (step S23).

[0168] 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, and Dc2 (step S24).

[0169] Next, when the partial discharge determination device 402 determines that no partial discharge has occurred in the underground cable 10 (NO in step S25), it discards the detection data Da2, Db2, and Dc2 and waits for a new generation timing according to the generation cycle T1 (NO in step S22).

[0170] 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 S25), it determines the maximum detection data Dmax, which is the detection data D with the highest detection intensity DI of the charge quantity Q among the detection data Da2, Db2, and Dc2, according to the 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 402 determines that the detection data Da2 is the maximum detection data Dmax (step S26).

[0171] 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 S27).

[0172] Next, the partial discharge determination device 402 determines the occurrence side Sd of partial discharge with respect to the insulating connection part 42 based on the comparison result between the detection intensity DI of the charge quantity Q in the detection data Da2 corresponding to the underground cable 10A that is the partial discharge cable Cpd and the detection intensity DI of the charge quantity Q in the detection data Da2 and Db2 (step S28).

[0173] Next, the partial discharge determination device 402 notifies the server of the determination result of the partial discharge cable Cpd (step S29).

[0174] Next, the partial discharge determination device 402 waits for a new generation timing according to the generation cycle T1 (NO in step S22).

[0175] 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 generation side Sd of the partial discharge, but the present disclosure is not limited thereto. The processing unit 132 may be configured to determine the partial discharge cable Cpd without determining the generation side Sd of the partial discharge.

[0176] Further, the partial discharge determination device 402 according to the second embodiment of the present disclosure is configured to include the antenna 112, but the present disclosure is not limited thereto. Instead of the antenna 112, the partial discharge determination device 402 may be configured to include another sensor for detecting a 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.

[0177] For example, when the partial discharge determination device 402 includes a metal foil electrode, the processing unit 132 may be configured to determine the generation side Sd based on the time difference of voltage pulses detected at a plurality of metal foil electrodes instead of the comparison result between the charge amount Q in the detection data D corresponding to the partial discharge cable Cpd and the charge amount Q in the detection data D corresponding to the other underground cable 10.

[0178] 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 the plurality of detection units 122, the present disclosure is not limited thereto. The processing unit 132 may perform correction processing for 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 processing. The correction parameter is created in advance based on the charge amount Q of the detection data D generated by the corresponding detection unit 122 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 can be reduced. Note that, instead of the processing unit 132 performing the correction processing, the detection unit 122 may be configured to generate the detection data D using the corresponding table Tb2 corrected using the correction parameter.

[0179] The above embodiments should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims be included.

[0180] Each process (each function) of the above-described embodiment is realized by a processing circuit including one or more processors. The 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 programs (instructions) for causing the one or more processors to execute the respective processes. The one or more processors may execute the respective processes according to the programs read from the one or more memories, or may execute the respective processes according to a logic circuit designed in advance to execute the respective 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 the respective 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 the respective 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.

[0181] The above description includes the features appended below. [Appendix 1] A partial discharge determination device that determines the cable in which partial discharge has occurred among a plurality of cables, The cable has 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 covering the periphery of the insulating layer, and the shielding layer is electrically connected to other cables, The partial discharge determination device, Detection data indicating the correspondence between the phase of a 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 the combination of the phase and the charge amount, and an acquisition unit that acquires a plurality of the detection data equal in number to the plurality of cables, A determination unit that determines a partial discharge cable, which is the cable in which the partial discharge has occurred among the plurality of cables, based on the plurality of detection data acquired by the acquisition unit. The partial discharge determination device further includes, A detection unit that detects the occurrence of the partial discharge in the cable and provides the detection data in which the occurrence of the partial discharge is detected to the acquisition unit, the partial discharge determination device.

[0182] [Appendix 2] A partial discharge determination device that determines the cable in which partial discharge has occurred among a plurality of cables, The cable has 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 covering the periphery of the insulating layer, and the shielding layer is electrically connected to other cables, The partial discharge determination device, Comprises a processing circuit, The processing circuit, Detection data indicating the 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 the combination of the phase and the charge amount, and acquiring a plurality of the detection data equal in number to the number of the plurality of cables. A partial discharge determination device that determines a partial discharge cable, which is the cable in which the partial discharge has occurred among the plurality of cables, based on the plurality of acquired detection data.

Explanation of Signs

[0183] 10, 10A, 10B, 10C Underground Cable 11A, 11B, 11C Cable Terminal 12 Cable 13, 15 Grounding Node 14 Grounding Cable 16, 16A, 16B, 16C Cross Bonding Wire (Line) 20, 20A1, 20A2, 20B1, 20B2, 20C1, 20C2 Cable 31 Manhole 41 Normal Connection Part 42 Insulated Connection Part 43, 44 Above - ground Connection Part 71 Conductor 72 Inner Semiconductor Layer 73 Insulator 74 Outer Semiconductor Layer 75 Shielding Layer 76 Sheath 77 Insulating Tube 81 Terminal 111, 111A, 111B, 111C CT 112, 112A, 112B, 112C Antenna 121, 121A, 121B, 121C, 122, 122A, 122B, 122C Detection Unit 131, 132 Processing Unit (Acquisition Unit, Determination Unit) 141, 142 Storage Unit 401, 402 Partial Discharge Determination Device 501,502 Partial Discharge Detection System 511 Power Transmission System D, Dx, Dy, Da1, Db1, Dc1, Da2, Db2, Dc2 Detection Data Th1, Th2 Threshold Values Qm1, Qm2, Cmax Maximum Values Pmax Phase TP Test Pattern

Claims

1. A partial discharge determination device that determines the cable in which partial discharge has occurred among a plurality of cables, wherein the cable has 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, and the shielding layer is cross-bonded to the shielding layer of another one of the cables, the partial discharge determination device includes: an acquisition unit that acquires a plurality of pieces of detection data, which is 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 appearance of a combination of the phase and the charge amount, and the number of the plurality of pieces of detection data is the same as the number of the plurality of cables; and a determination unit that determines a partial discharge cable, which is the cable in which the partial discharge has occurred among the plurality of cables, based on the plurality of pieces of detection data acquired by the acquisition unit.

2. The determination unit determines maximum detection data, which is the detection data having the maximum detection intensity of the charge amount among the plurality of pieces of detection data, and determines the partial discharge cable based on a determination result of the maximum detection data. The partial discharge determination device according to claim 1.

3. The determination unit calculates, for each piece of detection data, a maximum value of an absolute value of the charge amount in the detection data as the detection intensity, and determines that the detection data having the largest maximum value among the plurality of pieces of detection data is the maximum detection data. The partial discharge determination device according to claim 2.

4. The determination unit calculates, for each piece of detection data, a maximum value of an absolute value of the charge amount corresponding to the phase at which the sum of the frequencies is maximum in the detection data as the detection intensity, and determines that the detection data having the largest maximum value among the plurality of pieces of detection data is the maximum detection data. The partial discharge determination device according to claim 2.

5. The determination unit calculates, for each piece of detection data, a maximum value of a correlation coefficient between a predetermined test pattern indicating a correspondence relationship between the phase, the charge amount, and the frequency and the detection data as the detection intensity, and determines that the detection data having the largest maximum value among the plurality of pieces of detection data is the maximum detection data. The partial discharge determination device according to claim 2.

6. The acquisition unit acquires, for each cable, the detection data indicating the correspondence relationship among the phase, the charge amount, and the frequency of the partial discharge current detected in the cable. The partial discharge determination device according to any one of claims 2 to 5, wherein the determination unit determines that the cable corresponding to the maximum detection data is the partial discharge cable.

7. The determination unit further determines the occurrence side of partial discharge based on a reference of a connection portion between the conductors in the partial discharge cable, based on a comparison result between the charge amount in the detection data corresponding to the partial discharge cable and the charge amount in the detection data corresponding to a cable different from the partial discharge cable among the plurality of cables. The partial discharge determination device according to claim 6.

8. The plurality of cables are composed of three cables of a three-phase three-wire system. The acquisition unit acquires, for each line, the detection data indicating the correspondence relationship among the phase, the charge amount, and the frequency of the partial discharge current detected in a line that cross-bond connects the shielding layers of each of the two cables. The partial discharge determination device according to any one of claims 2 to 5, wherein the determination unit determines that one of the two cables is the partial discharge cable based on the phase of the potential of the conductors of the two cables to which the shielding layer is connected via the line corresponding to the maximum detection data and the phase corresponding to the detection intensity of the charge amount in the maximum detection data.

9. The partial discharge determination device according to claim 8, wherein the determination unit further determines the occurrence side of partial discharge based on a reference of a connection portion between the conductors in the partial discharge cable, based on the determination result of the maximum detection data and the determination result of the partial discharge cable.

10. A partial discharge determination method in a partial discharge determination device that determines a cable in which partial discharge has occurred among a plurality of cables, The cable has 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 the shielding layer is cross-bond connected to the shielding layers of other cables. The partial discharge determination method includes Detection data indicating the 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 the combination of the phase and the charge amount, and acquiring a plurality of the detection data equal in number to the number of the plurality of cables. A partial discharge determination method including a step of determining a partial discharge cable, which is the cable in which the partial discharge has occurred among the plurality of cables, based on the plurality of acquired detection data.

Images