Equipment-connected terminal and spacer
The equipment-connected terminal enhances insulation by using an overlapping semiconductive layer configuration to manage electric field stress, ensuring stable operation at high voltages and reducing terminal size.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SUMIDEN TRANSMISSION & DISTRIBUTION SYST PROD LTD
- Filing Date
- 2025-01-27
- Publication Date
- 2026-07-30
AI Technical Summary
Existing equipment-connected terminals face insulation degradation due to increased electric field stress as voltage applicability increases, leading to potential failure of cable insulating layers and spacers when larger power cables are used.
The equipment-connected terminal incorporates an insulating cylinder with a main-body internal semiconductive layer and a spacer with a spacer internal semiconductive layer, positioned to overlap and protrude from the main-body layer, effectively managing electric field distribution and stress.
This configuration stabilizes insulation by reducing electric field stress, preventing excessive stress on cable and spacer layers, allowing for improved insulation and reduced terminal size without increasing thickness, even at high voltages.
Smart Images
Figure JP2025002462_30072026_PF_FP_ABST
Abstract
Description
EQUIPMENT-CONNECTED TERMINAL AND SPACER
[0001] The present disclosure relates to an equipment-connected terminal and a spacer.
[0002] In order to connect a power cable to a predetermined equipment, an equipment-connected terminal may be provided (e.g., Patent Literature 1).
[0003] PTL. 1: Japanese Patent Laid-Open Publication No. H9-289049
[0004] According to an aspect of the present disclosure, there is provided an equipment-connected terminal, including: an internal terminal that is connected to a conductor of a power cable by compression and is configured to be connectable to a terminal of an equipment; an insulating cylinder that has a cable-insertion hole in which the power cable with the internal terminal connected thereto is inserted and is configured to maintain insulation outside the internal terminal and the power cable; and a spacer having a cylindrical shape, which is fitted to surround an outer circumference of the power cable and is interposed between an inner circumferential surface of the cable-insertion hole and an outer circumferential surface of the power cable, wherein the insulating cylinder includes a main-body internal semiconductive layer containing semiconductive rubber, the main-body internal semiconductive layer is provided to surround the outer circumferences of the internal terminal and the power cable inserted in the cable-insertion hole, the spacer includes a spacer internal semiconductive layer containing semiconductive rubber, and the spacer internal semiconductive layer is placed at a position overlapping the main-body internal semiconductive layer in a state where the power cable fitted with the spacer is inserted in the cable-insertion hole.
[0005] FIG. 1 is a schematic cross-sectional view of an equipment-connected terminal according to an embodiment of the present disclosure.FIG. 2 is a schematic cross-sectional view, illustrating an equipment-connected terminal according to a modified example 1 of an embodiment of the present disclosure.FIG. 3 is a schematic cross-sectional view, illustrating an equipment-connected terminal according to a modified example 2 of an embodiment of the present disclosure.FIG. 4 is a schematic cross-sectional view illustrating distribution of equipotential lines in an equipment-connected terminal according to a sample A.FIG. 5 is a diagram illustrating an electric field stress reduction rate at an end part of the main-body internal semiconductive layer, and an electric field stress increase rate at an end part of the spacer internal semiconductive layer.FIG. 6 is a schematic cross-sectional view illustrating distribution of equipotential lines in an equipment-connected terminal according to a sample B.Problem to be Solved by the Disclosure
[0006] An object of the present disclosure is to improve an insulation of an equipment-connected terminal. [Advantageous Effect of the Disclosure
[0007] According to the present disclosure, the insulation of the equipment-connected terminal can be improved.Description of Embodiment of the Disclosure
[0008] <Knowledges Obtained by the Inventors> First, the knowledges obtained by the inventors will be described.
[0009] In recent years, for example, an equipment-connected terminal may be provided to connect a power cable to a switchgear of a wind power generation facility. The output of the wind turbine of such a wind power generation facility has becoming higher. For this reason, the equipment-connected terminal needs to be configured to be applicable to high voltages according to the output of the wind turbine.
[0010] The present inventors investigated an equipment-connected terminal applicable to high voltages, and found that the following new problems arose.
[0011] Now, an equipment-connected terminal 90 of a comparative example will be described with reference to FIG. 6. The comparative example of FIG. 6 corresponds to a sample B in an example described later. In FIG. 6, the lower half of the configuration of the equipment-connected terminal 90 is omitted. The solid lines in the equipment-connected terminal 90 of the comparative example of FIG. 6 indicate equipotential lines.
[0012] As illustrated in FIG. 6, the equipment-connected terminal 90 of the comparative example includes, for example, an insulating cylinder 930 and a spacer 940. The insulating cylinder 930 includes a cable-insertion hole 931, and is configured to maintain the insulation outside a power cable 100. The insulating cylinder 930 includes, for example, a main-body internal semiconductive layer 932, a main-body insulating layer 934, and a main-body external semiconductive layer 936. The main-body internal semiconductive layer 932 is provided to surround the vicinity of a front end of a conductor 110 of the power cable 100 inserted in the cable-insertion hole 931.
[0013] The spacer 940 is fitted to surround the outer circumference of the power cable 100. The spacer 940 is interposed between an inner circumferential surface of the cable-insertion hole 931 and an outer circumferential surface of the power cable 100. The use of the spacer 940 enables the power cables 100 having various diameters to be applied to the equipment-connected terminal 90.
[0014] As the applicable voltage of the equipment-connected terminal 90 of the comparative example increases, the size (diameter) of the power cable 100 inserted in the cable-insertion hole 931 increases, and the thickness of the cable insulating layer 130 of the power cable 100 becomes thicker. Since the inner diameter of the cable-insertion hole 931 is larger, the thickness of the spacer 400 inserted in the cable-insertion hole 931 becomes thicker, even when the power cable 100 with a smaller diameter is used for the equipment-connected terminal 90. Therefore, when the power cable 100 fitted with the spacer 940 is inserted in the cable-insertion hole 931, the distance between the conductor 110 of the power cable 100 and the main-body internal semiconductive layer 932 of the insulating cylinder 930 becomes wider.
[0015] In this case, in the vicinity of a point TP, the equipotential lines curve and wrap around from an end part P1 of the main-body internal semiconductive layer 932 of the insulating cylinder 930 toward a region close to the front end of the conductor 110 of the power cable 100, as illustrated in FIG. 6. In other words, the electric fields wrap around toward the region close to the front end of the conductor 110 of the power cable 100. When electric fields wrap around toward such a region, the partially generated electric field stress may exceed the acceptable stress of at least one of the cable insulating layer 130 and the spacer 940. As a result, the insulation of the equipment-connected terminal 90 may be degraded.
[0016] The present inventors have studied intensively to solve the above-mentioned new problem, and consequently conceived a configuration that can improve the insulation of the equipment-connected terminal even when the applicable voltage of the equipment-connected terminal increases.
[0017] The present disclosure described below is based on the above-described knowledges found by the present inventors.
[0018] <Embodiments of the Disclosure> Next, embodiments of the present disclosure will be listed and described.
[0019] [1] An equipment-connected terminal according to an aspect of the present disclosure includes: an internal terminal that is connected to a conductor of a power cable and is configured to be connectable to a terminal of an equipment; an insulating cylinder that has a cable-insertion hole in which the power cable with the internal terminal connected thereto is inserted and is configured to maintain insulation outside the internal terminal and the power cable; and a spacer having a cylindrical shape, which is fitted to surround an outer circumference of the power cable and is interposed between an inner circumferential surface of the cable-insertion hole and an outer circumferential surface of the power cable, wherein the insulating cylinder includes a main-body internal semiconductive layer containing semiconductive rubber, the main-body internal semiconductive layer is provided to surround the outer circumferences of the internal terminal and the power cable inserted in the cable-insertion hole, the spacer includes a spacer internal semiconductive layer containing semiconductive rubber, and the spacer internal semiconductive layer is placed at a position overlapping the main-body internal semiconductive layer in a state where the power cable fitted with the spacer is inserted in the cable-insertion hole. According to this configuration, the insulation of the equipment-connected terminal can be improved.
[0020] [2] In the equipment-connected terminal described above in [1], the spacer internal semiconductive layer is placed to protrude from the main-body internal semiconductive layer along the cable-insertion hole in a state where the power cable fitted with the spacer is inserted in the cable-insertion hole. According to this configuration, the insulation of the equipment-connected terminal can be stably improved.
[0021] [3] In the equipment-connected terminal described above in [2], the length of the spacer internal semiconductive layer protruding from the main-body internal semiconductive layer along the cable-insertion hole is more than 0 mm and 30 mm or less, in a state where the power cable fitted with the spacer is inserted in the cable-insertion hole. According to this configuration, the protrusion length of the spacer internal semiconductive layer is set to more than 0 mm, so that the electric field stress at the end part of the main-body internal semiconductive layer can be stably relieved. On the other hand, the protrusion length of the spacer internal semiconductive layer is set to 30 mm or less, so that the generation of excessive electric field stress at the end part of the spacer internal semiconductive layer due to the protrusion of the spacer internal semiconductive layer can be suppressed.
[0022] [4] In the equipment-connected terminal described above in any one of [1] to [3], the spacer internal semiconductive layer includes an end part opposite to a front end in the axial direction of the spacer, and the end part of the spacer internal semiconductive layer curves in an arc shape protruding in the axial direction of the spacer. According to this configuration, the equipotential lines can be smoothly distributed along the arc-shaped end part of the spacer internal semiconductive layer.
[0023] [5] In the equipment-connected terminal described above in any one of [1] to [4], the spacer includes the spacer internal semiconductive layer and a spacer insulating layer containing insulating rubber, the spacer internal semiconductive layer is provided in a region close to an inner circumferential surface of the spacer and is exposed on the inner circumferential surface of the spacer, and the spacer insulating layer is provided outside the spacer internal semiconductive layer and is exposed on an outer circumferential surface of the spacer. According to this configuration, the spacer can be stably produced by the mold method.
[0024] [6] In the equipment-connected terminal described above in any one of [1] to [4], the spacer includes the spacer internal semiconductive layer and a spacer insulating layer containing insulating rubber, the spacer internal semiconductive layer is provided in a region close to an outer circumferential surface of the spacer and is exposed on the outer circumferential surface of the spacer, and the spacer insulating layer is provided inside the spacer internal semiconductive layer and is exposed on an inner circumferential surface of the spacer. According to this configuration, the same state as the state where the main-body internal semiconductive layer is thickened can be attained.
[0025] [7] In the equipment-connected terminal described above in any one of [1] to [4], the spacer internal semiconductive layer is provided over an entire radial direction of the spacer and is exposed on both an inner circumferential surface of the spacer and an outer circumferential surface of the spacer. According to this configuration, the same state as the state where the main-body internal semiconductive layer is thickened can be attained.
[0026] [8] A spacer according to another aspect of the present disclosure is used for the equipment-connected terminal described above in any one of [1] to [7]. According to this configuration, the insulation of the equipment-connected terminal can be improved.Details of the Embodiment of the Disclosure
[0027] Next, embodiments of the present disclosure will be described below with reference to the drawings. The present disclosure is not limited to these illustrations, but intended to be indicated by claims and encompass all the changes which fall within the meaning and scope equivalent to claims.
[0028] <One Embodiment of the Disclosure> (1) Equipment-connected terminal The equipment-connected terminal 10 according to this embodiment will be explained with reference to FIG. 1.
[0029] In FIG. 1, the power cable 100 is shown in side view, not in cross-sectional view. In FIG. 1, a part of the cross-section is not hatched. In FIG. 1, a part of a bushing 820 and a part of an insulating plug 840 are omitted. In FIG. 1, a connection between the spacer internal semiconductive layer 420 described below and at least one of the conductor 110 and the internal terminal 200 is omitted.
[0030] In the following description, the "axial direction" of the power cable 100 refers to the direction of the central axis of the power cable 100. The "radial direction" of the power cable 100 refers to the direction from the central axis toward the outer circumference of the power cable 100. The same terms as those used for the power cable 100 may be used for each layer constituting the power cable 100 and for the spacer 400. A surface of the cable-insertion hole 311 having a cylindrical shape, facing radially inward, is referred to as an "inner circumferential surface". A surface of the power cable 100 facing radially outward is referred to as an "outer circumferential surface". In the spacer 400 having a cylindrical shape, a surface facing radially inward is referred to as an "inner circumferential surface", and a surface facing radially outward is referred to as an "outer circumferential surface".
[0031] As illustrated in FIG. 1, the equipment-connected terminal 10 of this embodiment is configured to connect the power cable 100 to a predetermined equipment. The equipment to be connected is, for example, a switchgear in a wind power generation facility.
[0032] The equipment-connected terminal 10 of this embodiment includes, for example, an internal terminal 200, an insulating cylinder 300, a spacer 400, and a tape layer (insulating tape, anticorrosive layer, anticorrosive tape) 900.
[0033] (Power cable) As illustrated in FIG. 1, the power cable 100 is configured as a solid insulated cable which is a high-voltage power transmission cable. Examples of the power cable 100 include XLPE (Cross-Linked Polyethylene) cables. The base resin constituting the cable insulating layer 130 described below of the power cable 100 may be polypropylene as well as crosslinked polyethylene. The power cable 100 may be for AC or DC.
[0034] The applicable voltage of the power cable 100 is not limited. However, the power cable 100 may be configured to be applicable to 66 kV or more, for example.
[0035] The power cable 100 includes, for example, a conductor (cable conductor) 110, a cable internal semiconductive layer (not shown), a cable insulating layer 130, a cable external semiconductive layer 140, a cable shield layer (cable metal layer, not shown), and a cable sheath 160, in this order from the central axis of the conductor 110 toward the outer circumference of the power cable 100.
[0036] The power cable 100 is stripped stepwise from the front end toward the opposite in the axial direction of the conductor 110. That is, the conductor 110, the cable internal semiconductive layer, the cable insulating layer 130, the cable external semiconductive layer 140, the cable shield layer, and the cable sheath 160 are exposed in this order from the front end toward the opposite in the axial direction of the conductor 110.
[0037] (Internal terminal) The internal terminal 200 is not only connected to the conductor 110 of the power cable 100 but also configured to be connectable to the terminal of the equipment (not shown). Specifically, the internal terminal 200 is configured as a compression terminal, for example. The internal terminal 200 includes a cylindrical part 220 and a plate-like part 240, for example.
[0038] The cylindrical part 220 has an insertion hole 222 in which the conductor 110 of the power cable 100 is inserted. The cylindrical part 220 with the power cable 100 inserted therein is compressed in the radial direction. Thus, the cylindrical part 220 is configured to be connected to the conductor 110 of the power cable 100.
[0039] The plate-like part 240 is configured to be plate-like. The plate-like part 240 is connected to the opposite to the opening of the insertion hole 222 of the cylindrical part 220. The plate-like part 240 has a through hole 242 penetrating in the thickness direction of the plate-like part 240. A connecting terminal (numeral not shown) such as a stud bolt to be connected to, for example, a terminal of an equipment, is inserted in the through hole 242 of the plate-like part 240. A male thread part of the connecting terminal protrudes from the plate-like part 240 toward a plug fitting hole 316 described below. A nut (not shown) is provided on the opposite side to the connecting terminal across the plate-like part 240. The nut is tightened on the male thread part of the connecting terminal.
[0040] (Insulating cylinder (terminal main body, insulating unit, rubber unit)) The insulating cylinder 300 constitutes a main body of the equipment-connected terminal 10. The insulating cylinder 300 is configured to maintain the insulation outside the internal terminal 200 and the power cable 100.
[0041] The insulating cylinder 300 has, for example, a T-shaped outline and a T-shaped hole. Specifically, the insulating cylinder 300 has, for example, a cable-insertion hole 311, a bushing fitting hole 314, and a plug fitting hole 316. The cable-insertion hole 311, the bushing fitting hole 314, and the plug fitting hole 316 are connected to each other.
[0042] The cable-insertion hole 311 is formed, for example, linearly along a vertical part of the insulating cylinder 300 having a T shape, in the insulating cylinder 300. The power cable 100 in a state where the internal terminal 200 is connected thereto and a spacer 400 described later is fitted therewith is inserted in the cable-insertion hole 311. The plate-like part 240 of the internal terminal 200 is placed at the connection between the cable-insertion hole 311, the bushing fitting hole 314, and the plug fitting hole 316.
[0043] In this embodiment, the cable-insertion hole 311, for example, in a state where a power cable 100 fitted with a spacer 400 is not inserted, has a uniform inner diameter in the direction in which the power cable 100 is to be inserted in a portion where the power cable 100 fitted with spacer 400 is to be inserted. Thus, the cable-insertion hole 311 can be easily processed.
[0044] The bushing fitting hole 314 is formed, for example, in a cone shape (truncated cone shape) decreasing in diameter from a first end toward the center of the horizontal part of the insulating cylinder 300 having a T shape, in the insulating cylinder 300. The bushing fitting hole 314 is elastically fitted with the bushing 820 of the equipment. Thus, the terminal provided in the bushing 820 of the equipment is connected to the connecting terminal fixed to the plate-like part 240 of the internal terminal 200.
[0045] The plug fitting hole 316 is formed, for example, in a cone shape (truncated cone shape) decreasing in diameter from a second end, opposite to the first end, toward the center of the horizontal part of the insulating cylinder 300 having a T shape, in the insulating cylinder 300. The plug fitting hole 316 is elastically fitted with the insulating plug 840. The insulating plug 840 includes, for example, a female thread part from a center of a tapered front end toward a rear end. The female thread part of the insulating plug 840 is configured to threadedly engaged with the male thread part of the connecting terminal protruding from the plate-like part 240 of the internal terminal 200.
[0046] The insulating cylinder 300, for example, is divided into three parts with different electrical characteristics. Specifically, the insulating cylinder 300 includes, for example, a main-body internal semiconductive layer 320, a main-body insulating layer 340, and a main-body external semiconductive layer 360. The main-body internal semiconductive layer 320, the main-body insulating layer 340, and the main-body external semiconductive layer 360 are integrally molded.
[0047] The main-body internal semiconductive layer 320 contains, for example, semiconductive rubber (semiconductive resin). The semiconductive rubber contains a base polymer and a filler. Examples of the base polymer of the semiconductive rubber include ethylene propylene rubber and silicone rubber. Examples of the filler contained in the semiconductive rubber include carbon black.
[0048] The main-body internal semiconductive layer 320 is provided, for example, to surround the outer circumferences of the internal terminal 200 and the power cable 100 inserted in the cable-insertion hole 311. The main-body internal semiconductive layer 320 constitutes a part of the cable-insertion hole 311, that is, is exposed to the inside of the cable-insertion hole 311. The main-body internal semiconductive layer 320 can relieve the electric field around the internal terminal 200 and the conductor 110.
[0049] The main-body insulating layer 340 contains, for example, insulating rubber (insulating resin). Examples of the insulating rubber include ethylene propylene rubber and silicone rubber.
[0050] The main-body insulating layer 340 is provided, for example, to cover the outer circumference of the main-body internal semiconductive layer 320, and constitutes the main part of the insulating cylinder 300. The main-body insulating layer 340, for example, together with the main-body internal semiconductive layer 320, constitutes a part of the cable-insertion hole 311.
[0051] The main-body external semiconductive layer 360 contains, for example, semiconductive rubber. The semiconductive rubber of the main-body external semiconductive layer 360 is similar to the semiconductive rubber of the main-body internal semiconductive layer 320, for example.
[0052] The main-body external semiconductive layer 360 is provided, for example, to cover the main-body insulating layer 340, and constitutes at least a part of the outer circumferential surface of the insulating cylinder 300. The main-body external semiconductive layer 360 is grounded.
[0053] (Spacer (adapter)) The spacer 400 has, for example, a cylindrical shape and is fitted to surround the outer circumference of the power cable 100. The spacer 400 is configured, for example, to be interposed between an inner circumferential surface of the cable-insertion hole 311 and an outer circumferential surface of the power cable 100.
[0054] The outer diameter of the spacer 400 is set to be equal to the inner diameter of the cable-insertion hole 311 of the insulating cylinder 300 or slightly larger than the inner diameter of the cable-insertion hole 311. The inner diameter of the spacer 400 is set to be slightly smaller than the outer diameter of the cable insulating layer 130 of the power cable 100. As a result, when the power cable 100 fitted with the spacer 400 is inserted in the cable-insertion hole 311, an appropriate surface pressure can be applied to the power cable 100 from the insulating cylinder 300 through the spacer 400, depending on the size (diameter) of the power cable 100.
[0055] In this embodiment, the outer diameter of the spacer 400 is uniform in the axial direction of the spacer 400, for example, in a state where the spacer 400 is not fitted with the power cable 100. In other words, the outer circumferential surface of the spacer 400 is straight when viewed in a cross-section along the axial direction of the spacer 400. Thus, the spacer 400 can be easily molded.
[0056] The spacer 400 has, for example, a front end in the axial direction of the spacer 400 and a rear end, opposite to the front end, of the spacer 400. When the spacer 400 is fitted with the power cable 100, the conductor 110 of the power cable 100 is exposed from the front end in the axial direction of the spacer 400.
[0057] The spacer 400 has, for example, a claw part 410 at the front end in the axial direction of the spacer 400. The claw part 410 protrudes inward in the radial direction of the spacer 400 and has an inner diameter smaller than that of the portion in which the power cable 100 is inserted. Thus, the claw part 410 of the spacer 400 is configured to engage the front end of the cable insulating layer 130, for the power cable 100 fitted with the spacer 400. As a result, when the power cable 100 fitted with the spacer 400 is inserted in the cable-insertion hole 311, the spacer 400 can be positioned in the cable-insertion hole 311 and misalignment of the spacer 400 can be suppressed.
[0058] The spacer 400 of this embodiment, for example, is divided into three parts with different electrical characteristics. This point will be described in more detail below.
[0059] (Tape layer) The equipment-connected terminal 10 may include, for example, a tape layer 900 having insulation which protects the exposed part of the equipment-connected terminal 10. Specifically, the tape layer 900 may be provided to cover a region including a part of the insulating cylinder 300, a rear end of the spacer 400 exposed outside the cable-insertion hole 311, and a front end of the cable sheath 160 of the power cable 100.
[0060] (2) Configuration of spacer With reference to FIG. 1, the configuration of the spacer 400 of this embodiment will be described in detail.
[0061] The spacer 400 of this embodiment includes, for example, the spacer internal semiconductive layer 420, the spacer insulating layer 440, and the spacer external semiconductive layer 460. The spacer internal semiconductive layer 420, the spacer insulating layer 440, and the spacer external semiconductive layer 460 are integrally molded into a cylindrical shape. The spacer internal semiconductive layer 420, the spacer insulating layer 440, and the spacer external semiconductive layer 460 are provided in this order from the front end toward the rear end in the axial direction of the spacer 400.
[0062] (Spacer internal semiconductive layer) The spacer internal semiconductive layer 420 contains, for example, semiconductive rubber (semiconductive resin). The semiconductive rubber contains a base polymer and a filler. Examples of the base polymer of the semiconductive rubber include ethylene propylene rubber and silicone rubber. Examples of the filler contained in the semiconductive rubber include carbon black.
[0063] The spacer internal semiconductive layer 420 is provided in a region close to the front end in the axial direction of the spacer 400, as mentioned above. The spacer internal semiconductive layer 420 is electrically connected to, for example, at least one of the conductor 110 and the internal terminal 200. The spacer internal semiconductive layer 420 and at least one of the conductor 110 and the internal terminal 200 are connected by at least any one of semiconductive rubber, semiconductive tape, and a metal component, for example.
[0064] In this embodiment, the spacer internal semiconductive layer 420 is placed, for example, at the position overlapping the main-body internal semiconductive layer 320 in a state where the spacer 400 is inserted in the cable-insertion hole 311. The phrase, "overlapping the main-body internal semiconductive layer 320" used herein means "overlapping the main-body internal semiconductive layer 320 when viewed from the outer circumference of the spacer 400", and does not necessarily have to be in contact with the main-body internal semiconductive layer 320. The above-mentioned arrangement of the spacer internal semiconductive layer 420 makes it possible to suppress the wraparound of the electric field from the end part P1 of the main-body internal semiconductive layer 320 of the insulating cylinder 300 toward the region close to the front end of the conductor 110 of the power cable 100.
[0065] In this embodiment, the spacer internal semiconductive layer 420 is provided, for example, in a region close to the inner circumferential surface of the spacer 400 and is exposed on the inner circumferential surface of the spacer 400. That is, the spacer internal semiconductive layer 420 is placed in contact with the outer circumference of the power cable 100, for example, in a state where the power cable 100 fitted with the spacer 400 is inserted in the cable-insertion hole 311. Thus, the spacer internal semiconductive layer 420 can relieve the electric field at the position close to the conductor 110 of the power cable 100.
[0066] On the other hand, the spacer internal semiconductive layer 420 is not exposed, for example, on the outer circumferential surface of the spacer 400. That is, the spacer internal semiconductive layer 420 is placed separated from the main-body internal semiconductive layer 320 across the spacer insulating layer 440 in the radial direction of the spacer 400, for example, in a state where the power cable 100 fitted with the spacer 400 is inserted in the cable-insertion hole 311. Since the spacer 400 has such a configuration, the spacer 400 can be stably produced by the mold method.
[0067] In this embodiment, the spacer internal semiconductive layer 420 is placed to protrude from the main-body internal semiconductive layer 320 along the cable-insertion hole 311, for example, in a state where the power cable 100 fitted with the spacer 400 is inserted in the cable-insertion hole 311. In other words, the spacer internal semiconductive layer 420 is placed to protrude from the end part P1 of the main-body internal semiconductive layer 320, from the front end toward the opposite in the axial direction of the spacer 400, for example, in a state where the power cable 100 fitted with the spacer 400 is inserted in the cable-insertion hole 311. As a result, it is possible to stably suppress the wraparound of the electric field from the end part P1 of the main-body internal semiconductive layer 320 of the insulating cylinder 300 toward the region close to the front end of the conductor 110 of the power cable 100.
[0068] In this embodiment, there is no limitation on the length L of the spacer internal semiconductive layer 420 protruding from the main-body internal semiconductive layer 320 along the cable-insertion hole 311 (hereinafter, also referred to as "protrusion length L of the spacer internal semiconductive layer 420") in a state where the power cable 100 fitted with the spacer 400 is inserted in the cable-insertion hole 311. However, the protrusion length L of the spacer internal semiconductive layer 420 may be, for example, more than 0 mm and 30 mm or less, or 5 mm or more and 20 mm or less. By setting the protrusion length L of the spacer internal semiconductive layer 420 to more than 0 mm, or to 5 mm or more, it is possible to stably suppress the wraparound of the electric field from the end part P1 of the main-body internal semiconductive layer 320 of the insulating cylinder 300 toward the region close to the front end of the conductor 110 of the power cable 100. On the other hand, by setting the protrusion length L of the spacer internal semiconductive layer 420 to 30 mm or less, or to 20 mm or less, it is possible to prevent equipotential lines from becoming excessively dense between the spacer internal semiconductive layer 420 and the spacer external semiconductive layer 460.
[0069] In this embodiment, the spacer internal semiconductive layer 420 has an end part P2 opposite to the front end in the axial direction of the spacer 400. The end part P2 of the spacer internal semiconductive layer 420, for example, curves in an arc shape protruding in the axial direction of the spacer 400 (toward the rear end in the axial direction of the spacer 400). Thus, the electric field in the vicinity of the end part P2 of the spacer internal semiconductive layer 420 can be relieved.
[0070] The thickness of the spacer internal semiconductive layer 420 in the radial direction of the spacer 400 is not particularly limited. However, in the radial direction of the spacer 400, the ratio of the thickness of the spacer internal semiconductive layer 420 to the total thickness of the spacer 400 (hereinafter also referred to as "thickness ratio of the spacer internal semiconductive layer 420") is not particularly limited, but may be 1 / 2 or more, for example. Thus, the radius of curvature at the end part P2 of the spacer internal semiconductive layer 420 can be prevented from becoming excessively small. As a result, the electric field concentration at the end part P2 of the spacer internal semiconductive layer 420 can be stably suppressed. The ratio of the thickness of the spacer internal semiconductive layer 420 to the total thickness of the spacer 400 is not particularly limited, but may be 1 or less, or 3 / 4 or less, for example.
[0071] (Spacer insulating layer) The spacer insulating layer 440 contains, for example, insulating rubber. Examples of the insulating rubber include ethylene propylene rubber and silicone rubber.
[0072] The spacer insulating layer 440 is in contact with the spacer internal semiconductive layer 420. The spacer insulating layer 440 constitutes a middle part of the spacer 400.
[0073] In this embodiment, the spacer insulating layer 440 is provided, for example, outside the spacer internal semiconductive layer 420 and exposed on the outer circumferential surface of the spacer 400. That is, the spacer insulating layer 440 is placed between the main-body internal semiconductive layer 320 and the spacer internal semiconductive layer 420, for example, in a state where the power cable 100 fitted with the spacer 400 is inserted in the cable-insertion hole 311. Thus, the spacer 400 can be stably produced by the mold method.
[0074] The spacer insulating layer 440 is placed in contact with both the main-body insulating layer 340 and the cable insulating layer 130 that is exposed, for example, in a state where the power cable 100 fitted with the spacer 400 is inserted in the cable-insertion hole 311. Thus, the insulation between the main-body insulating layer 340 and the cable insulating layer 130 that is exposed can be maintained.
[0075] (Spacer external semiconductive layer) The spacer external semiconductive layer 460 contains, for example, semiconductive rubber. The semiconductive rubber of the spacer external semiconductive layer 460 is similar to the semiconductive rubber of the spacer internal semiconductive layer 420, for example.
[0076] The spacer external semiconductive layer 460 is provided in a region close to the rear end in the axial direction of the spacer 400, as mentioned above. That is, the spacer external semiconductive layer 460 is placed separated from the spacer internal semiconductive layer 420 across the spacer insulating layer 440 in the radial direction of the spacer 400.
[0077] The spacer external semiconductive layer 460 has, for example, a cone shape. That is, the spacer external semiconductive layer 460 has an inner diameter gradually increasing from the rear end in the axial direction of the spacer 400 toward the front end of the spacer 400. With this configuration, the spacer external semiconductive layer 460 forms a so-called stress cone.
[0078] The spacer external semiconductive layer 460 is placed in contact with the outer circumferential surface of the cable external semiconductive layer 140 of the power cable 100, for example, in a state where the power cable 100 fitted with the spacer 400 is inserted in the cable-insertion hole 311. With this configuration, equipotential lines can be evenly distributed along the spacer external semiconductive layer 460 having a cone shape, around the cable external semiconductive layer 140 that is exposed where relatively high electric fields occur. As a result, the electric field concentration can be suppressed around the cable external semiconductive layer 140 that is exposed.
[0079] (3) Summary of this embodiment According to this embodiment, one or more effects described below are achieved.
[0080] (a) In this embodiment, the spacer internal semiconductive layer 420 is placed at the position overlapping the main-body internal semiconductive layer 320 in a state where the spacer 400 is inserted in the cable-insertion hole 311. Thus, the spacer internal semiconductive layer 420 having semiconductivity is placed between the conductor 110 of the power cable 100 and the main-body internal semiconductive layer 320 of the insulating cylinder 300.
[0081] The above-mentioned arrangement of the spacer internal semiconductive layer 420 makes it possible to suppress the wraparound of the electric field from the end part P1 of the main-body internal semiconductive layer 320 of the insulating cylinder 300 toward the region close to the front end of the conductor 110 of the power cable 100. Thus, the electric field stress can be prevented from exceeding the acceptable stress of at least one of the cable insulating layer 130 and the spacer 400 in that region.
[0082] As described above, according to this embodiment, the insulation of the equipment-connected terminal 10 can be improved.
[0083] (b) In this embodiment, since the above-mentioned arrangement of the spacer internal semiconductive layer 420 suppresses the wraparound of the electric field, the length of the region of the main-body internal semiconductive layer 320 of the insulating cylinder 300 overlapping the cable insulating layer 130 of the power cable 100 can be shortened. Accordingly, the axial length of the spacer 400 can be shortened as well.
[0084] Further, since the above-mentioned arrangement of the spacer internal semiconductive layer 420 relieves the electric field stress, it is not necessary to excessively increase the thickness of the main-body insulating layer 340 of the insulating cylinder 300 even when the equipment-connected terminal 10 is applicable to a high voltage.
[0085] As a result, it is possible to reduce the size of the equipment-connected terminal 10 of this embodiment while improving the insulation of the equipment-connected terminal 10.
[0086] (c) In this embodiment, the spacer internal semiconductive layer 420 is placed to protrude from the main-body internal semiconductive layer 320 along the cable-insertion hole 311 in a state where the power cable 100 fitted with the spacer 400 is inserted in the cable-insertion hole 311. Thus, the equipotential lines can be smoothly distributed from the main-body internal semiconductive layer 320 toward the spacer internal semiconductive layer 420. The smooth distribution of the equipotential lines can stably suppress the wraparound of the electric field from the end part P1 of the main-body internal semiconductive layer 320 of the insulating cylinder 300 toward the region close to the front end of the conductor 110 of the power cable 100. For example, generation of excessive electric field stress at the end part P1 of the main-body internal semiconductive layer 320 can be suppressed. As a result, the insulation of the equipment-connected terminal 10 can be stably improved.
[0087] (d) In this embodiment, the length L of the spacer internal semiconductive layer 420 protruding from the main-body internal semiconductive layer 320 along the cable-insertion hole 311 may be more than 0 mm and 30 mm or less, or 5 mm or more and 20 mm or less, in a state where the power cable 100 fitted with the spacer 400 is inserted in the cable-insertion hole 311. By setting the protrusion length L of the spacer internal semiconductive layer 420 to more than 0 mm, or to 5 mm or more, it is possible to stably suppress the wraparound of the electric field from the end part P1 of the main-body internal semiconductive layer 320 of the insulating cylinder 300 toward the region close to the front end of the conductor 110 of the power cable 100. Thus, the electric field stress at the end part P1 of the main-body internal semiconductive layer 320 can be stably relieved. On the other hand, by setting the protrusion length L of the spacer internal semiconductive layer 420 to 30 mm or less, or to 20 mm or less, it is possible to prevent equipotential lines from becoming excessively dense between the spacer internal semiconductive layer 420 and the spacer external semiconductive layer 460. Thus, generation of excessive electric field stress at the end part P2 of the spacer internal semiconductive layer 420 due to the protrusion of the spacer internal semiconductive layer 420 can be suppressed.
[0088] (e) In this embodiment, the spacer internal semiconductive layer 420 has an end part P2 opposite to the front end in the axial direction of the spacer 400. The end part P2 of the spacer internal semiconductive layer 420 curves in an arc shape protruding in the axial direction of the spacer 400. Accordingly, the equipotential lines can be smoothly distributed along the end part P2 having an arc shape of the spacer internal semiconductive layer 420. As a result, the electric field in the vicinity of the end part P2 of the spacer internal semiconductive layer 420 can be relieved.
[0089] (4) Modified example of the embodiment The above-mentioned embodiment can be modified where appropriate, as in the following modified examples. Hereinafter, only elements different from the above-mentioned embodiment will be described, and elements substantially the same as those described in the above-mentioned embodiment will be designated by the same reference numerals and their description will be omitted.
[0090] <Modified Example 1> Now, an equipment-connected terminal 10 of a modified example 1 will be described with reference to FIG. 2.
[0091] In the modified example 1, the spacer internal semiconductive layer 420 is provided, for example, in a region close to the outer circumferential surface of the spacer 400 and is exposed on the outer circumferential surface of the spacer 400, as illustrated in FIG. 2. On the other hand, the spacer insulating layer 440 is provided, for example, inside the spacer internal semiconductive layer 420 and exposed on the inner circumferential surface of the spacer 400.
[0092] That is, in the modified example 1, the spacer internal semiconductive layer 420 is placed in contact with the main-body internal semiconductive layer 320, and the spacer insulating layer 440 is placed between the spacer internal semiconductive layer 420 and the outer circumference of the power cable 100, for example, in a state where the power cable 100 fitted with the spacer 400 is inserted in the cable-insertion hole 311.
[0093] According to the modified example 1, the spacer internal semiconductive layer 420 is placed in contact with the main-body internal semiconductive layer 320, so that the configuration is equivalent to a state where the main-body internal semiconductive layer 320 is thickened. As a result, it is possible to more stably suppress the wraparound of the electric field from the end part P1 of the main-body internal semiconductive layer 320 of the insulating cylinder 300 toward the region close to the front end of the conductor 110 of the power cable 100.
[0094] <Modified Example 2> Now, an equipment-connected terminal 10 of a modified example 2 will be described with reference to FIG. 3.
[0095] In the modified example 2, the spacer internal semiconductive layer 420 is provided, for example, over the entire radial direction of the spacer 400 and is exposed on both the inner circumferential surface of the spacer 400 and the outer circumferential surface of the spacer 400, as illustrated in FIG. 3.
[0096] That is, in the modified example 2, the spacer internal semiconductive layer 420 is placed in contact with both the main-body internal semiconductive layer 320 and the outer circumference of the power cable 100, for example, in a state where the power cable 100 fitted with the spacer 400 is inserted in the cable-insertion hole 311.
[0097] According to the modified example 2, since the spacer internal semiconductive layer 420 is placed in contact with both the main-body internal semiconductive layer 320 and the outer circumference of the power cable 100, the configuration is equivalent to a state where the main-body internal semiconductive layer 320 is thickened to contact with the outer circumference of the power cable 100. As a result, it is possible to more stably suppress the wraparound of the electric field from the end part P1 of the main-body internal semiconductive layer 320 of the insulating cylinder 300 toward the region close to the front end of the conductor 110 of the power cable 100.
[0098] <Other Embodiments of the Disclosure> Although the embodiment of the present disclosure has been specifically described, the present disclosure is not limited to the embodiment mentioned above, and various modifications can be made without departing from the gist of the present disclosure.
[0099] The embodiment mentioned above describes a case where the internal terminal 200 is a compression terminal, but the present disclosure is not limited to this case. The internal terminal 200 may be configured as a so-called shear bolt sleeve in which the conductor 110 in its cylindrical part 220 is tightened and fixed by a bolt inserted in the radial direction of the cylindrical part 220.
[0100] In the embodiment mentioned above, the insulating cylinder 300 is illustrated as not having a stress cone part, but the present disclosure is not limited to this case. As necessary, the insulating cylinder 300 may further include a cone-shaped semiconductive part (stress cone part) close to the opening of the cable-insertion hole 311, gradually increasing in the inner diameter from the opening of the cable-insertion hole 311 toward the opposite side.
[0101] Next, examples according to the present disclosure will be described. These examples are illustrative of the present disclosure, and the present disclosure is not limited by these examples. In the following examples, the elements that are substantially the same as the elements described in the above-mentioned embodiments and modified examples are represented by the same reference numerals and explained.
[0102] (1) Simulation of equipment-connected terminal The distribution of equipotential lines and the electric field stress in the equipment-connected terminal when a voltage of 130 kV was applied between the conductor 110 and the shield under the following conditions were determined by simulation.
[0103] <Sample A> The equipment-connected terminal 10 of the above-mentioned embodiment was set as a sample A.
[0104] (Power cable 100) Cross-section area of conductor 110: 1200 mm2 Thickness of cable insulating layer 130: 13 mm It was assumed that there was no cable internal semiconductive layer or cable external semiconductive layer.
[0105] (Insulating cylinder 300) Inner diameter of cable-insertion hole 311: 70 mm Thickness of insulating cylinder 300 in radial direction of cable-insertion hole 311: 20 mm
[0106] (Spacer 400) Axial length of portion of spacer 400 inserted in cable-insertion hole 311 of insulating cylinder 300: 250 mm Overall thickness of spacer 400 in radial direction: 15 mm Length L of spacer internal semiconductive layer 420 protruding from main-body internal semiconductive layer 320 along cable-insertion hole 311: 0 mm or more and 30 mm or less Thickness of spacer internal semiconductive layer 420 in radial direction of spacer 400: 1 / 2 overall thickness in radial direction of spacer 400 Distance from front end in axial direction of spacer 400 toward front end of spacer external semiconductive layer 460: 60 mm
[0107] <Sample B> The sample B corresponds to the comparative example described in <Knowledges Obtained by the Inventors>. The equipment-connected terminal 90 having the same configuration as that of the sample A except that the spacer internal semiconductive layer 420 was not included was set as the sample B.
[0108] (2) Results The simulation results for the samples A and B will be described with reference to FIG. 4 to FIG. 6. The solid lines in the equipment-connected terminal 10 of FIG. 4 indicate equipotential lines.
[0109] <Sample B> As illustrated in FIG. 6, in the vicinity of a point TP in the sample B, the equipotential lines curved and wrapped around from an end part P1 of the main-body internal semiconductive layer 932 of the insulating cylinder 930 toward a region close to the front end of the conductor 110 of the power cable 100. In other words, the electric field wrapped around toward the region close to the front end of the conductor 110 of the power cable 100. For this reason, the partially generated electric field stress increased in the vicinity of the end part P1 of the main-body internal semiconductive layer 932.
[0110] <Sample A> In contrast, as illustrated in FIG. 4, in the sample A, since the spacer internal semiconductive layer 420 was placed at the position overlapping the main-body internal semiconductive layer 320, the wraparound of the equipotential lines from an end part P1 of the main-body internal semiconductive layer 320 of the insulating cylinder 300 toward a region close to the front end of the conductor 110 of the power cable 100 was suppressed. In other words, the wraparound of the electric field toward the region close to the front end of the conductor 110 of the power cable 100 was suppressed. Thus, the electric field stress at the end part P1 of the main-body internal semiconductive layer 320 was relieved.
[0111] Now, the electric field stress reduction rate RP1 at the end part P1 of the main-body internal semiconductive layer 320, and the electric field stress increase rate RP2 at the end part P2 of the spacer internal semiconductive layer 420 will be described with reference to FIG. 5.
[0112] The electric field stress reduction rate RP1 (%) at the end part P1 of the main-body internal semiconductive layer 320 can be determined by the following formula (1): RP1 = {(Ea - Eb) / Eb} × 100 ・・・(1) wherein Ea is an electric field stress, expressed in kV / mm, generated at the end part P1 of the main-body internal semiconductive layer 320 when a voltage of 130 kV is applied between the conductor 110 and the shield in the sample A; and Eb is an electric field stress, expressed in kV / mm, generated at the end part P1 of the main-body internal semiconductive layer 320 when a voltage of 130 kV is applied between the conductor 110 and the shield in the sample B.
[0113] The electric field stress increase rate RP2 (%) at the end part P2 of the spacer internal semiconductive layer 420 is determined by the following formula (2): RP2 = {(Ex - E0) / E0} × 100 ・・・(2) wherein Ex is an electric field stress, expressed in kV / mm, generated at the end part P2 of the spacer internal semiconductive layer 420 when a voltage of 130 kV is applied between the conductor 110 and the shield in the sample A in which the protrusion length L of the spacer internal semiconductive layer 420 is a predetermined length; and E0 is an electric field stress, expressed in kV / mm, generated at the end part P2 of the spacer internal semiconductive layer 420 when a voltage of 130 kV is applied between the conductor 110 and the shield in the sample A in which the protrusion length L of the spacer internal semiconductive layer 420 is 0 mm.
[0114] As illustrated in FIG. 5, in the sample A, the electric field stress reduction rate RP1 was - 4% or less at the end part P1 of the main-body internal semiconductive layer 320, when the protrusion length L of the spacer internal semiconductive layer 420 was 0 mm or more. Therefore, in the sample A, since the spacer internal semiconductive layer 420 was placed at the position overlapping the main-body internal semiconductive layer 320, it was clearly confirmed that the electric field stress at the end part P1 of the main-body internal semiconductive layer 320 was relieved compared to the sample B.
[0115] Further, in the sample A, the electric field stress reduction rate RP1 at the end part P1 of the main-body internal semiconductive layer 320 was monotonically reduced as the protrusion length L of the spacer internal semiconductive layer 420 increased. Therefore, in the sample A, it is confirmed that the electric field stress at the end part P1 of the main-body internal semiconductive layer 320 can be stably relieved by setting the protrusion length L of the spacer internal semiconductive layer 420 to more than 0 mm. Further, it is confirmed that the electric field stress at the end part P1 of the main-body internal semiconductive layer 320 in the sample A can be more stably relieved by setting the protrusion length L of the spacer internal semiconductive layer 420 to 5 mm or more.
[0116] On the other hand, in the sample A, the electric field stress increase rate RP2 at the end part P2 of the spacer internal semiconductive layer 420 was monotonically increased as the protrusion length L of the spacer internal semiconductive layer 420 increased. In the sample A, electric field stress increase rate RP2 at the end part P2 of the spacer internal semiconductive layer 420 tended to saturate as the protrusion length L of the spacer internal semiconductive layer 420 approached 35 mm. In a case where the protrusion length L of the spacer internal semiconductive layer 420 was 30 mm, the electric field stress at the end part P2 of the spacer internal semiconductive layer 420 was smaller than the electric field stress at the end part P1 of the main-body internal semiconductive layer 320 in the sample B.
[0117] Thus, it is confirmed that by setting the protrusion length L of the spacer internal semiconductive layer 420 to 30 mm or less, the generation of excessive electric field stress at the end part P2 of the spacer internal semiconductive layer 420 due to the protrusion of the spacer internal semiconductive layer 420 can be suppressed. Further, it is also confirmed that by setting the protrusion length L of the spacer internal semiconductive layer 420 to 20 mm or less, the generation of excessive electric field stress at the end part P2 of the spacer internal semiconductive layer 420 can be stably suppressed.
[0118] The equipment-connected terminal 10 configured so that the power cable is applicable to the voltage of 66 kV or more is observed to exhibit a tendency similar to that illustrated in FIG. 5, even when each dimension is different from that of the above-described sample A.
[0119] <Supplementary Description> Hereinafter, a supplementary description of the aspect of the present disclosure will be given. An aspect referenced by a number in brackets from which the following supplementary description depends corresponds to the aspect described in <Embodiments of the Present Disclosure>.
[0120] [9] The equipment-connected terminal described above in [2], wherein the length of the spacer internal semiconductive layer protruding from the main-body internal semiconductive layer along the cable-insertion hole is 5 mm or more and 20 mm or less, in a state where the power cable fitted with the spacer is inserted in the cable-insertion hole.
[0121] 10 Equipment-connected terminal 90 Equipment-connected terminal 100 Power cable 110 Conductor 130 Cable insulating layer 140 Cable external semiconductive layer 160 Cable sheath 200 Internal terminal 220 Cylindrical part 222 Insertion hole 240 Plate-like part 242 Through hole 300 Insulating cylinder 311 Cable-insertion hole 314 Bushing fitting hole 316 Plug fitting hole 320 Main-body internal semiconductive layer 340 Main-body insulating layer 360 Main-body external semiconductive layer 400 Spacer 410 Claw part 420 Spacer internal semiconductive layer 440 Spacer insulating layer 460 Spacer external semiconductive layer 820 Bushing 840 Insulating plug 900 Tape layer 930 Insulating cylinder 931 Cable-insertion hole 932 Main-body internal semiconductive layer 934 Main-body insulating layer 936 Main-body external semiconductive layer 940 Spacer P1 End part of main-body internal semiconductive layer P2 End part of spacer internal semiconductive layer
Claims
1. An equipment-connected terminal, comprising: an internal terminal that is connected to a conductor of a power cable and is configured to be connectable to a terminal of an equipment; an insulating cylinder that has a cable-insertion hole in which the power cable with the internal terminal connected thereto is inserted and is configured to maintain insulation outside the internal terminal and the power cable; and a spacer having a cylindrical shape, which is fitted to surround an outer circumference of the power cable and is interposed between an inner circumferential surface of the cable-insertion hole and an outer circumferential surface of the power cable, wherein the insulating cylinder includes a main-body internal semiconductive layer containing semiconductive rubber, the main-body internal semiconductive layer is provided to surround the outer circumferences of the internal terminal and the power cable inserted in the cable-insertion hole, the spacer includes a spacer internal semiconductive layer containing semiconductive rubber, and the spacer internal semiconductive layer is placed at a position overlapping the main-body internal semiconductive layer in a state where the power cable fitted with the spacer is inserted in the cable-insertion hole.
2. The equipment-connected terminal according to claim 1, wherein the spacer internal semiconductive layer is placed to protrude from the main-body internal semiconductive layer along the cable-insertion hole in a state where the power cable fitted with the spacer is inserted in the cable-insertion hole.
3. The equipment-connected terminal according to claim 2, wherein the length of the spacer internal semiconductive layer protruding from the main-body internal semiconductive layer along the cable-insertion hole is more than 0 mm and 30 mm or less, in a state where the power cable fitted with the spacer is inserted in the cable-insertion hole.
4. The equipment-connected terminal according to any one of claims 1 to 3, wherein the spacer internal semiconductive layer includes an end part opposite to a front end in the axial direction of the spacer, and the end part of the spacer internal semiconductive layer curves in an arc shape protruding in the axial direction of the spacer.
5. The equipment-connected terminal according to any one of claims 1 to 4, wherein the spacer includes the spacer internal semiconductive layer and a spacer insulating layer containing insulating rubber, the spacer internal semiconductive layer is provided in a region close to an inner circumferential surface of the spacer and is exposed on the inner circumferential surface of the spacer, and the spacer insulating layer is provided outside the spacer internal semiconductive layer and is exposed on an outer circumferential surface of the spacer.
6. The equipment-connected terminal according to any one of claims 1 to 4, wherein the spacer includes the spacer internal semiconductive layer and a spacer insulating layer containing insulating rubber, the spacer internal semiconductive layer is provided in a region close to an outer circumferential surface of the spacer and is exposed on the outer circumferential surface of the spacer, and the spacer insulating layer is provided inside the spacer internal semiconductive layer and is exposed on an inner circumferential surface of the spacer.
7. The equipment-connected terminal according to any one of claims 1 to 4, wherein the spacer internal semiconductive layer is provided over an entire radial direction of the spacer and is exposed on both an inner circumferential surface of the spacer and an outer circumferential surface of the spacer.
8. A spacer used for the equipment-connected terminal according to any one of claims 1 to 7.