Power transmission system, partial discharge detection method, and power transmission device

Abstract

To provide a power transmission system, a partial discharge detection method, and a power transmission device which can prevent generation of change in a potential distribution caused by a discharge detection conductor.SOLUTION: The power transmission system comprises: a power transmission device including a first conductor to which a positive voltage of direct current power is applied, a second conductor to which a negative voltage of direct current power is applied, and an insulating first spacer separating the first conductor and the second conductor and including a discharge detection conductor at an intermediate part between the first conductor and the second conductor; a resistor with an end connected to the discharge detection conductor; and a detector for detecting a current flowing in the resistor.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a power transmission system, a partial discharge detection method, and a power transmission device.

Background Art

[0002] Patent Document 1 describes the following wire protection device. That is, in the wire protection device described in Patent Document 1, it is detected whether an arc discharge has occurred based on the current flowing through a conductor thin film (metal thin film) covered with a resin insulating film including a thin film spacer inserted between a plurality of power line groups having the same potential in each group. Here, the plurality of power line groups are, for example, AC power line groups of each phase of a three-phase AC, and each wire group is bundled by a string-type tape. Further, the potential of the conductor thin film is the ground potential.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a thin film spacer that separates between a plurality of wire groups bundled with a tape, when the conductor thin film is not included, the potential in the thin film spacer becomes various levels according to the distance from the wire groups. On the other hand, when the conductor thin film is included, since the potential in the conductor thin film becomes the same, the potential in the thin film spacer will be different between the case where the conductor thin film is included and the case where it is not included. That is, when a conductor thin film is provided in the thin film spacer, there is a problem that a change occurs in the potential distribution, and in some cases, partial discharge is likely to occur due to the provision of the conductor thin film.

[0005] The present disclosure has been made to solve the above problems, and when a conductor for discharge detection is included in a spacer between conductors, it is possible to prevent a change in the potential distribution caused by the conductor for discharge detection. An object of the present disclosure is to provide a power transmission system, a partial discharge detection method, and a power transmission device.

Means for Solving the Problems

[0006] The power transmission system according to the present disclosure includes a first conductor to which a positive voltage of DC power is applied, a second conductor to which a negative voltage of the DC power is applied, and a first spacer of an insulator that separates the first conductor and the second conductor, and the first spacer includes a conductor for discharge detection at an intermediate portion between the first conductor and the second conductor, and a power transmission device including the same, a resistor having one end connected to the conductor for discharge detection, and a detector for detecting a current flowing through the resistor.

[0007] The partial discharge detection method according to the present disclosure uses a first conductor to which a positive voltage of DC power is applied, a second conductor to which a negative voltage of the DC power is applied, a first spacer of an insulator that separates the first conductor and the second conductor, and the first spacer includes a conductor for discharge detection at an intermediate portion between the first conductor and the second conductor, a power transmission device including the same, a resistor having one end connected to the conductor for discharge detection, and a detector for detecting a current flowing through the resistor, and detects partial discharge generated in the power transmission device.

[0008] The power transmission device according to the present disclosure includes a first conductor to which a positive voltage of DC power is applied, a second conductor to which a negative voltage of the DC power is applied, and a first spacer of an insulator that separates the first conductor and the second conductor, and the first spacer includes a conductor for discharge detection at an intermediate portion between the first conductor and the second conductor.

Effects of the Invention

[0009] According to the power transmission system, partial discharge detection method, and power transmission device of the present disclosure, it is possible to prevent a change in the potential distribution caused by the conductor for discharge detection.

Brief Description of the Drawings

[0010]

Figure 1

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Figure 11

Embodiments for Carrying Out the Invention

[0011] <First Embodiment> Referring to FIGS. 1 to 7, a power transmission system, a partial discharge detection method, and a power transmission device according to a first embodiment of the present disclosure will be described. FIG. 1 is a configuration diagram of the power transmission system according to the first embodiment of the present disclosure. FIG. 2 is a perspective view of the power transmission device according to the first embodiment of the present disclosure. FIG. 3 is a perspective view of a conductor and a spacer according to the first embodiment of the present disclosure. FIG. 4 is a block diagram of the power transmission system according to the first embodiment of the present disclosure. FIG. 5 is a configuration diagram of the power transmission system according to the first embodiment of the present disclosure. FIG. 6 is a diagram showing an example of the potential distribution of the power transmission device according to the first embodiment of the present disclosure. FIG. 7 is a diagram showing a comparative example of the potential distribution of the power transmission device according to the first embodiment of the present disclosure (when there is no discharge detection conductor). In each figure, the same or corresponding components are denoted by the same reference numerals, and the description thereof will be appropriately omitted. In addition, the terms "first", "second", and "third" used in this specification are interchangeably used to distinguish one component from another component.

[0012] As shown in FIG. 1, the power transmission system 100 according to the first embodiment of the present disclosure includes a power transmission device 1, a resistor 101, and a partial discharge detector 102. The power transmission system 100 is a system for detecting partial discharge generated in the power transmission device 1 that transmits DC power. Note that FIG. 1 shows the cross-sectional shape of the power transmission device 1.

[0013] As shown in FIGS. 1 to 3, the power transmission device 1 according to the first embodiment of the present disclosure includes a first conductor 11, a second conductor 12, a first spacer 13, a second spacer 14, an electric wire tube 15, and a discharge detection conductor 17 provided (embedded) in the first spacer 13.

[0014] The first conductor 11 and the second conductor are electric wires that constitute the main line of the DC power circuit. A positive voltage (positive electrode) of DC power is applied to the first conductor 11, and a negative voltage (negative electrode) of DC power is applied to the second conductor 12. In this embodiment, a conductor is a substance having a relatively high electrical conductivity, and can be composed of, for example, copper, aluminum, or other metals.

[0015] The first spacer 13 is an insulator that separates the first conductor 11 and the second conductor 12, and includes a discharge detection conductor 17 at an intermediate portion between the first conductor 11 and the second conductor 12. The discharge detection conductor 17 is, for example, a metal thin film and extends in the DC power transmission direction as shown in FIG. 2. In this embodiment, an insulator is an object in which electricity hardly flows. Further, the intermediate portion means a region that is equidistant (substantially equidistant) from the first conductor 11 and the second conductor 12.

[0016] The second spacer 14 has a hollow portion 141 and is an insulator that encloses the first conductor 11, the second conductor 12, and the first spacer 13 in the hollow portion 141. The second spacer 14 separates the first conductor 11 and the second conductor 12 from the electric wire pipe 15. The electric wire pipe 15 is a conductor that encloses the second spacer 14. The electric wire pipe 15 is formed of a metal such as aluminum, for example. The electric wire pipe 15 can also be referred to as a metal conduit or the like. A fluid 16 such as air at atmospheric pressure, a pressurized gas, or a pressurized fluid such as a liquid is introduced into the electric wire pipe 15. The fluid 16 forms an insulating layer and functions as a cooling medium for air-cooling or water-cooling the first conductor 11, the second conductor 12, and the like.

[0017] Note that the spaces between the first conductor 11 and the second conductor 12 and the first spacer 13, between the first conductor 11 and the second conductor 12 and the second spacer 14, and between the second spacer 14 and the electric wire pipe 15 are combined in a state allowing contact or a certain gap and are not fixed to each other. However, each component may be fixed as appropriate. For example, the contact state or gap between the first conductor 11 and the second conductor 12 and the first spacer 13, between the first conductor 11 and the second conductor 12 and the second spacer 14, and between the second spacer 14 and the electric wire pipe 15 changes depending on, for example, the temperature state or the magnitude of the repulsive force acting between the first conductor 11 and the second conductor 12 by electromagnetic force.

[0018] As shown in FIG. 3, the first conductor 11 has a first portion B11 that forms a plane, and the second conductor 12 has a second portion B12 that forms a plane facing the first portion B11. Further, the first spacer 13 has a flat plate shape having a plane portion 131 facing the first portion B11 and the second portion B12. Further, as shown in FIG. 2, the first conductor 11 includes one or a plurality of plate-like portions B21 that extend in the direction of the second spacer 14 with the first portion B11 as a base end portion. Further, the second conductor 12 includes one or a plurality of plate-like portions B22 that extend in the direction of the second spacer 14 with the second portion B12 as a base end portion. According to this configuration, it is possible to achieve a good balance between improving the cooling efficiency (increasing the surface area, decreasing the resistance value, etc.) and reducing the weight.

[0019] As shown in FIG. 4, in the power transmission system 100 of the present embodiment, for example, a positive voltage of the DC power output from the converter 51 is applied to the first conductor 11 of the power transmission device 1, and a negative voltage of the DC power output from the converter 51 is applied to the first conductor 11. Further, the electric wire pipe 15 is connected to the neutral point N of the DC power output from the converter 51. The converter 51 inputs an AC output of a generator 22 such as a three-phase AC generator, converts it into DC power, and outputs it. Further, in the example shown in FIG. 4, two capacitors C are connected in series between the positive and negative output terminals of the converter 51, and the connection point of the two capacitors C is set as the neutral point N and the ground potential. However, the neutral point N of the DC power may be, for example, the neutral point of the generator 22. The electric wire pipe 15 of the power transmission device 1 is connected to the neutral point N (ground potential). The DC power output from the converter 51 is supplied to the DC load 23 through the power transmission device 1.

[0020] One end of the resistor 101 is connected to the discharge detection conductor 17, and the other end is connected to the neutral point N (ground potential). The partial discharge detector 102 includes, for example, a clamp-type current detector 1021 and a detection circuit 1022, and detects that a current equal to or greater than a predetermined value has flowed through the resistor 101.

[0021] In the power transmission system 100 of the present embodiment, as shown in FIG. 5, a discharge detection conductor 17 is embedded, for example, as a conductive film inside a first spacer 13 between a first conductor 11 and a second conductor 12 that constitute positive and negative transmission lines. The occurrence of partial discharge is detected by detecting, with an external partial discharge detector 102 as a discharge current, the charges induced in the conductive film due to the partial discharge generated between the transmission lines. FIG. 5 indicates a plurality of locations where the possibility of partial discharge occurrence is relatively high with star marks 50 (hereinafter also referred to as occurrence locations 50). The discharge detection conductor 17 can preferably detect the partial discharge within the region DB surrounded by the broken line among them.

[0022] Note that since the discharge detection conductor 17 is provided at the intermediate portion between the first conductor 11 and the second conductor 12, in the steady state (a state where DC power is being transmitted and no partial discharge is occurring), the neutral point potential (0 V (including almost 0 V)) of the DC power transmitted by the power transmission device 1 is applied. Also, in the present embodiment, the first spacer 13 has a flat plate shape facing a first portion B11 that forms a plane with the first conductor 11 and a second portion B12 that forms a plane with the second conductor 12. Therefore, the potential of the discharge detection conductor 17 can be set to 0 V in the steady state over almost the entire area of the first spacer 13.

[0023] Also, when the discharge detection conductor 17 is arranged, there is a concern about electrical disturbance inside the power transmission device 1 (such as the occurrence of partial discharge due to the conductive film). However, as shown in FIG. 6, if it is inserted in the middle of the transmission line, the internal potential distribution does not change (it is the same as the potential distribution when there is no discharge detection conductor 17 shown in FIG. 7). Therefore, according to the power transmission system 100 of the present embodiment, partial discharge can be detected without causing electrical disturbance due to the conductive film.

[0024] As described above, according to the power transmission system, partial discharge detection method, and power transmission device of the present embodiment, it is possible to prevent a change in the potential distribution caused by the discharge detection conductor.

[0025] In the above description, an example in which the first spacer 13 includes one discharge detection conductor 17 has been shown. However, there may be a plurality of discharge detection conductors 17. Alternatively, one power transmission device 1 may include a plurality of first spacers 13 each including one or a plurality of discharge detection conductors 17 in the power transmission direction. In this case, the position where the partial discharge occurs can be specified by specifying the position of the discharge detection conductor 17 that has detected the current due to the partial discharge.

[0026] <Second Embodiment> Next, with reference to FIGS. 8 to 10, a power transmission system, a partial discharge detection method, and a power transmission device according to a second embodiment of the present disclosure will be described. The power transmission system 100A according to the second embodiment of the present disclosure includes the power transmission device 1A shown in FIG. 8, a resistor 101, and a partial discharge detector 102, and also includes at least one of the partial discharge detector 103 shown in FIG. 9 or the partial discharge detector 104 shown in FIG. 10. As shown in FIG. 8, the power transmission device 1A includes one or more optical fibers 30 in the hollow portion 141. Each optical fiber 30 has one or a plurality of light receiving portions (or light receiving surfaces) 31, and receives and transmits the generation due to the partial discharge generated in the light receiving direction 32 indicated by the arrow by the light receiving portion 31. The light receiving portion 31 can be, for example, a portion where the coating of the coated optical fiber is removed, or a portion where an optical component such as an optical fiber is coupled to that portion. The light receiving direction 32 is determined so that the location 50 where the partial discharge occurs is within the field of view of the light receiving portion 31.

[0027] FIG. 9 shows a configuration example of the optical fiber 30 and the partial discharge detector 103. In the example shown in FIG. 9, each light receiving portion 31 of the plurality of optical fibers 30 is provided at a position different from each other with respect to the DC power transmission direction. The interval L1 can be, for example, about several tens of cm. However, the interval L1 is not limited to this example. The partial discharge detector 103 includes a photoelectric conversion unit 1031 that converts the light output from each optical fiber 30 into electricity, and a partial discharge detector 1032 that detects that an electrical signal corresponding to light having a predetermined intensity or more has been generated. The partial discharge detector 1032 can specify the occurrence position of the partial discharge by identifying the optical fiber 30 that has received light having a predetermined intensity or more. According to this configuration, the configuration of the partial discharge detector 103 can be simplified.

[0028] FIG. 10 shows a configuration example of the optical fiber 30 and the partial discharge detector 104. In the example shown in FIG. 10, one optical fiber 30 has a plurality of light receiving portions 31, and each light receiving portion 31 is provided at a position different from each other with respect to the DC power transmission direction. The interval L1 between each light receiving portion 31 may be equal or unequal. The partial discharge detector 104 includes a photoelectric conversion unit 1041 that converts the light output from one end of the optical fiber 30 into electricity, a photoelectric conversion unit 1042 that converts the light output from the other end of the optical fiber 30 into electricity, and detects that an electrical signal corresponding to light having a predetermined intensity or more has occurred, and a time difference detection and partial discharge detector 1043 that detects the time difference of the light arrival time (the time difference between the detection time by the photoelectric conversion unit 1041 and the detection time by the photoelectric conversion unit 1042). The time difference detection and partial discharge detector 1043 can specify the occurrence position of the partial discharge based on the time difference of the light arrival time when receiving light having a predetermined intensity or more. According to this configuration, the number of optical fibers 30 can be reduced, so that the cooling space in the power transmission device 1A can be increased.

[0029] Note that the configuration shown in FIG. 9 and the configuration shown in FIG. 10 can be appropriately combined.

[0030] According to this embodiment, partial discharges generated between the conductor 11 and the conductor 12 can be detected with high sensitivity by the partial discharge detector 102, and partial discharges generated between the conductor 11 or the conductor 12 and the wire conduit 15 can be detected with high sensitivity by the partial discharge detector 103 or the partial discharge detector 104.

[0031] <Third Embodiment> Next, with reference to FIG. 11, a power transmission system, a partial discharge detection method, and a power transmission device according to the third embodiment of the present disclosure will be described. The power transmission system 100B according to the third embodiment of the present disclosure includes a power transmission device 1B, a resistor 101, a partial discharge detector 102, and a partial discharge detector 105. As shown in FIG. 11, the power transmission device 1B includes one or more electromagnetic wave antennas 60 that are in close contact with the inner wall of the wire conduit 15 at a predetermined interval in the circumferential direction, or are provided in the vicinity of the inner wall. The electromagnetic wave antennas 60 may be intensively arranged in the vicinity of the partial discharge generation location 50. Considering the adhesion to the inner wall of the wire conduit 15, a thin and flexible structure is desirable for the electromagnetic wave antennas 60. As the electromagnetic wave antennas 60, for example, a structure in which a patch antenna is incorporated in a film such as PEN (polyethylene naphthalate) or PI (polyimide) is suitable.

[0032] The partial discharge detector 105 detects that each electromagnetic wave antenna 60 has received an electromagnetic wave having a predetermined intensity or more. Further, the partial discharge detector 105 can identify the position where the partial discharge occurs by identifying the electromagnetic wave antennas 60 that have received an electromagnetic wave having a predetermined intensity or more.

[0033] According to this embodiment, partial discharges generated between the conductor 11 and the conductor 12 can be detected with high sensitivity by the partial discharge detector 102, and partial discharges generated between the conductor 11 or the conductor 12 and the wire conduit 15 can be detected with high sensitivity by the partial discharge detector 105.

[0034] (Operational Effects) In the above-described power transmission system, partial discharge detection method, and power transmission device, a first conductor 11 to which a positive voltage of DC power is applied, a second conductor 12 to which a negative voltage of DC power is applied, and a first spacer 13 of an insulator that separates the first conductor 11 and the second conductor 12, and the first conductor 11 and the second conductor 12 include a discharge detection conductor 17 in an intermediate portion thereof, a second spacer 14 of an insulator that has a hollow portion 141 and encloses the first conductor 11, the second conductor 12, and the first spacer 13 in the hollow portion 141, and an electric wire tube 15 of a conductor that encloses the second spacer 14 are used, and partial discharge is detected by detecting a current flowing through a resistor 101 having one end connected to the discharge detection conductor 17. According to this configuration, since the discharge detection conductor 17 is provided in the intermediate portion between the first conductor 11 and the second conductor 12 that is originally at a constant potential (0 V; neutral point potential) (when there is no discharge detection conductor 17), no change in the potential distribution due to the discharge detection conductor 17 occurs. Also, partial discharge does not easily occur due to the provision of the discharge detection conductor 17.

[0035] (Other Embodiments) As described above, the embodiments of the present disclosure have been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and design changes and the like within the scope not departing from the gist of the present disclosure are also included. In the above embodiment, a metal thin film is exemplified as the discharge detection conductor 17, but the shape is not limited. For example, it may be a single electric wire or a plurality of electric wires arranged, or a plurality of electric wires arranged in a mesh shape. Also, the configurations of the second embodiment and the third embodiment may be combined and used.

[0036] Note that the partial discharge detector 102 is an example of the "detector" according to the present disclosure, the partial discharge detectors 103 and 104 are examples of the "second detector" according to the present disclosure, and the partial discharge detector 105 is an example of the "third detector" according to the present disclosure.

[0037] <Supplementary Note> The power transmission systems 100, 100A, or 100B described in each embodiment are understood as follows, for example.

[0038] (1) The power transmission systems 100, 100A, and 100B according to the first aspect include a first conductor 11 to which a positive voltage of DC power is applied, a second conductor 12 to which a negative voltage of the DC power is applied, and a first spacer 13 of an insulator that separates the first conductor and the second conductor, the first spacer including a discharge detection conductor 17 at an intermediate portion between the first conductor and the second conductor, and a power transmission device 1, 1A, or 1B. The power transmission device is provided with a resistor 101 having one end connected to the discharge detection conductor, and a detector (partial discharge detector 102) that detects a current flowing through the resistor. According to this aspect and the following aspects, it is possible to prevent a change in the potential distribution caused by the discharge detection conductor.

[0039] (2) The power transmission systems 100, 100A, and 100B according to the second aspect are the power transmission systems of (1), wherein the first conductor has a first portion B11 that forms a plane, the second conductor has a second portion B12 that forms a plane facing the first portion, and the first spacer has a flat plate shape having a plane portion 131 facing the first portion and the second portion. According to this aspect, for example, the potential of a relatively wide area such as the entire area can be made constant, and for example, the area of the discharge detection conductor can be increased.

[0040] (3) The power transmission systems 100, 100A, and 100B according to the third aspect are the power transmission systems of (1), wherein the other end of the resistor 101 is connected to the neutral point of the DC power. According to this aspect, the potential of the discharge detection conductor can be stabilized at the neutral point potential (0V) of the DC power.

[0041] (4) The power transmission system 100A according to the fourth aspect is the power transmission system of (1) to (3), wherein the power transmission device 1A has a hollow portion 141, and further includes a second spacer 14 of an insulator that encloses the first conductor, the second conductor, and the first spacer in the hollow portion. The power transmission system 100A further includes one or more optical fibers 30 laid in the hollow portion 141, and a second detector (partial discharge detectors 103 and 104) that detects that the one or more optical fibers have received light in the hollow portion. According to this aspect, partial discharges occurring at locations where the detection sensitivity decreases in the detector (partial discharge detector 102) can be detected with higher sensitivity compared to the case where this configuration is not provided.

[0042] (5) The power transmission system 100A according to the fifth aspect is the power transmission system of (4), wherein there are a plurality of the optical fibers, and each light receiving portion 31 of the plurality of optical fibers is provided at a position different from each other with respect to the transmission direction of the DC power. According to this aspect, the location where partial discharge occurs can be specified.

[0043] (6) The power transmission system 100A according to the sixth aspect is the power transmission system of (4) or (5), wherein at least one of the optical fibers has a plurality of light receiving portions 31 at positions different from each other with respect to the transmission direction of the DC power, and the second detector (partial discharge detector 104) further detects a time difference in the arrival times of the light received by the optical fiber at both ends of the optical fiber. According to this aspect, the location where partial discharge occurs can be specified with a small number of optical fibers.

[0044] (7) The power transmission system 100B according to the seventh aspect is the power transmission system of (1) to (6), wherein the power transmission device 1B has a hollow portion 141, and the second spacer 14 of the insulator that encloses the first conductor, the second conductor, and the first spacer in the hollow portion, and the wire pipe 15 of the conductor that encloses the second spacer are further provided, and one or more antennas 60 installed in the wire pipe, and a third detector (partial discharge detector 105) that detects that the one or more antennas have received electromagnetic waves generated in the wire pipe are further provided. According to this aspect, partial discharges occurring at locations where the detection sensitivity decreases with the detector (partial discharge detector 102) can be detected with better sensitivity compared to the case without this configuration.

Explanation of Signs

[0045] 1…Power transmission device 100, 100A, 100B…Power transmission systems 11…First conductor 12…Second conductor 13…First spacer 14…Second spacer 15…Wire pipe 16…Fluid 17…Conductor for discharge detection 101…Resistor 102~105…Partial discharge detectors 141…Hollow portion N…Neutral point

Claims

1. a first conductor to which a positive voltage of direct current power is applied; a second conductor to which a negative voltage of the direct current power is applied; a first spacer of an insulator that separates the first conductor and the second conductor, and includes a discharge detection conductor at an intermediate portion between the first conductor and the second conductor; a power transmission device comprising: a resistor having one end connected to the discharge detection conductor; a detector that detects a current flowing through the resistor a power transmission system comprising.

2. The first conductor has a first portion that forms a plane, The second conductor has a second portion that forms a plane facing the first portion, The first spacer has a flat plate shape having a plane portion facing the first portion and the second portion The power transmission system according to claim 1.

3. The other end of the resistor is connected to the neutral point of the direct current power The power transmission system according to claim 2.

4. The power transmission device further includes a second spacer of an insulator that has a hollow portion and encloses the first conductor, the second conductor, and the first spacer, one or more optical fibers laid in the hollow portion, a second detector that detects that the one or more optical fibers have received light in the hollow portion The power transmission system according to claim 3, further comprising.

5. There are a plurality of the optical fibers, Each light receiving portion of the plurality of optical fibers is provided at a position different from each other with respect to the transmission direction of the direct current power The power transmission system according to claim 4.

6. At least one of the optical fibers has a plurality of light receiving portions at positions different from each other with respect to the transmission direction of the direct current power, The second detector further detects a time difference in arrival times of the light received by the optical fiber at both ends of the optical fiber The power transmission system according to claim 4.

7. The power transmission device, has a hollow portion, a second spacer of an insulator that encloses the first conductor, the second conductor, and the first spacer, an electric wire pipe of a conductor that encloses the second spacer further comprising, one or more antennas installed in the electric wire pipe, a third detector that detects that the one or more antennas have received an electromagnetic wave generated in the electric wire pipe The power transmission system according to any one of claims 1 to 6, further comprising.

8. a first conductor to which a positive voltage of direct current power is applied; a second conductor to which a negative voltage of the direct current power is applied; A first spacer of an insulator that separates the first conductor and the second conductor, the first spacer including a discharge detection conductor at an intermediate portion between the first conductor and the second conductor, A power transmission device comprising: A resistor having one end connected to the discharge detection conductor, A detector that detects a current flowing through the resistor are used to detect partial discharge generated within the power transmission device Partial discharge detection method.

9. A first conductor to which a positive voltage of DC power is applied, A second conductor to which a negative voltage of the DC power is applied, A first spacer of an insulator that separates the first conductor and the second conductor, the first spacer including a discharge detection conductor at an intermediate portion between the first conductor and the second conductor, A power transmission device comprising:

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