Device-directly-connected terminal and spacer

Abstract

This device-directly-connected terminal comprises: an internal terminal that is connected to a conductor of a power cable and that is configured to be connectable to a terminal of a device; an insulation cylinder that has a cable insertion hole for inserting the power cable in a state of being connected to the internal terminal, and that is configured so as to maintain insulation of the outside of the power cable and the internal terminal; and a spacer that has a cylindrical shape and that is fitted to surround the outer circumference of the power cable and is interposed between the inner circumferential surface of the cable insertion hole and the outer circumferential surface of the power cable. The spacer has an outer diameter that gradually decreases toward the tip of the spacer in the axial direction such that the surface pressure applied to the spacer from the insulation cylinder gradually reduces toward the tip of the spacer.

Description

Machine-directly-connected terminal and spacer

[0001] The present disclosure relates to a machine-directly-connected terminal and a spacer.

[0002] A machine-directly-connected terminal may be provided for connecting a predetermined device and a power cable (for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 9-289049

[0004] According to one aspect of the present disclosure, an internal terminal connected to a conductor of a power cable and configured to be connectable to a terminal of a device, and a cable insertion hole into which the power cable in a state where the internal terminal is connected is inserted, and an insulating cylinder configured to maintain the insulation of the outside of the internal terminal and the power cable, and a spacer having a cylindrical shape, fitted so as to surround the outer periphery of the power cable, and interposed between the inner peripheral surface of the cable insertion hole and the outer peripheral surface of the power cable, are provided. The spacer has an outer diameter that gradually decreases toward the tip of the spacer so that the surface pressure applied to the spacer from the insulating cylinder gradually decreases toward the axial tip of the spacer. A machine-directly-connected terminal is provided.

[0005] FIG. 1 is a schematic cross-sectional view showing a machine-directly-connected terminal according to an embodiment of the present disclosure. FIG. 2 is a schematic cross-sectional view showing a spacer according to an embodiment of the present disclosure. FIG. 3 is a schematic cross-sectional view showing a spacer according to a modified example of an embodiment of the present disclosure.

[0006] [Problems to be Solved by the Present Disclosure] The object of the present disclosure is to manufacture a machine-directly-connected terminal easily and stably.

[0007] [Effects of the Present Disclosure] According to the present disclosure, a machine-directly-connected terminal can be manufactured easily and stably.

[0008] [Description of Embodiments of the Present Disclosure] <Findings Obtained by the Inventors> First, the findings obtained by the inventors will be described.

[0009] A direct-connection terminal for equipment may include, for example, an insulating tube and a spacer. The insulating tube has a cable insertion hole and is configured to maintain the insulation of the outside of the power cable. The spacer is fitted so as to surround the outer circumference of the power cable. The spacer is interposed between the inner surface of the cable insertion hole and the outer surface of the power cable. By using this spacer, power cables of various diameters can be applied to the direct-connection terminal for equipment.

[0010] The outer diameter of the spacer is sometimes designed to be slightly larger than the inner diameter of the cable insertion hole in the insulating tube. This design results in elastic stress (compressive stress) being applied to the spacer from the insulating tube.

[0011] However, if stress is applied from the insulating tube to the spacer over a long period of time, the rubber constituting the spacer will gradually deteriorate. As a result, the stress applied from the insulating tube to the spacer will ease, and the surface pressure applied from the insulating tube to the spacer will decrease over time. Consequently, if the spacer is not properly designed, the insulating properties may decrease in the areas where the surface pressure applied from the insulating tube to the spacer has decreased.

[0012] Conventionally, the outer diameter of the spacer was designed so that even if the rubber constituting the spacer deteriorated, the surface pressure applied from the insulating cylinder to the spacer would remain above a certain level. Furthermore, conventionally, from the viewpoint of maintaining the surface pressure applied from the insulating cylinder to the spacer, it was considered desirable for this surface pressure to be uniform in the axial direction of the power cable.

[0013] In recent years, direct-connection terminals with the above configuration are sometimes used, for example, to connect power cables to switchgear in wind power generation facilities. In such wind power generation facilities, the output of the wind turbines is increasing. Therefore, direct-connection terminals are required to be configured to be applicable to high voltages according to the output of the wind turbines.

[0014] However, when the inventors considered a direct-connection terminal for equipment applicable to high voltages, they found that the following new problems arose.

[0015] As the applied voltage of the equipment-connected terminal increases, the insulation layer of the insulating tube becomes thicker. As the insulation layer of the insulating tube becomes thicker, the surface pressure applied from the insulating tube to the spacer increases. As a result, the insertion load (hereinafter also referred to as "power cable insertion load") when inserting the power cable with the spacer fitted into the cable insertion hole of the insulating tube increases.

[0016] As the applied voltage of the equipment-directly connected terminal increases, the axial length of the spacer inserted into the cable insertion hole of the insulating cylinder (hereinafter also referred to as the "spacer insertion length") increases. As the spacer insertion length increases, the insertion load of the power cable increases. In the design described above, where the surface pressure is uniform in the axial direction of the power cable, the insertion load of the power cable tends to increase linearly with respect to the spacer insertion length.

[0017] As described above, in the conventional configuration, the insertion load of the power cable becomes large, making it difficult to insert the power cable with the spacer fitted into the cable insertion hole of the insulating cylinder at the point of connection to the equipment. As a result, it was difficult to reliably manufacture equipment direct connection terminals.

[0018] In order to solve the above-mentioned novel problems, the inventors have diligently studied and found a configuration that allows for the easy and stable manufacture of equipment-direct connection terminals, even when the applicable voltage of the equipment-direct connection terminal is high.

[0019] The following disclosure is based on the above-mentioned findings discovered by the inventors.

[0020] <Embodiments of the Disclosure> Next, embodiments of the Disclosure will be described by listing them.

[0021] [1] A device direct connection terminal according to one aspect of the present disclosure comprises: an internal terminal connected to a conductor of a power cable and configured to be connectable to a terminal of a device; an insulating cylinder having a cable insertion hole into which the power cable with the internal terminal connected is inserted, and configured to maintain insulation on the outside of the internal terminal and the power cable; and a cylindrical spacer fitted so as to surround the outer circumference of the power cable and interposed between the inner circumferential surface of the cable insertion hole and the outer circumferential surface of the power cable, wherein the spacer has an outer diameter that gradually decreases toward the tip of the spacer such that the surface pressure applied to the spacer from the insulating cylinder gradually decreases toward the axial tip of the spacer. With this configuration, a device direct connection terminal can be manufactured easily and stably.

[0022] [2] In the equipment direct connection terminal described in [1] above, the insulating cylinder has an internal semiconducting layer containing semiconducting rubber, the internal semiconducting layer is provided so as to surround the internal terminal inserted into the cable insertion hole and the outer circumference of the power cable, the internal semiconducting layer has an end at a position in contact with the outer circumference of the spacer, and the outer diameter of the spacer is set such that the surface pressure applied to the spacer from the end of the internal semiconducting layer is 0.05 MPa or more. With this configuration, insulation can be maintained at the interface between the insulating cylinder and the spacer.

[0023] [3] In the equipment direct connection terminal described in [1] or [2] above, the spacer has an inclined surface inclined with respect to the axial direction of the spacer such that the outer diameter of the spacer gradually decreases toward the tip of the spacer, and the inclination angle of the inclined surface with respect to the axial direction of the spacer is 0.1° or more and 1° or less. With this configuration, by setting the inclination angle θ to 0.1° or more, the insertion load of the power cable 100 can be stably reduced. On the other hand, by setting the inclination angle θ to 1° or less, insulation can be stably maintained at the interface between the insulating cylinder 300 and the spacer 400.

[0024] [4] In the equipment direct connection terminal described in any one of [1] to [3] above, the cable insertion hole has a uniform inner diameter in the direction in which the power cable is inserted, in the portion into which the power cable with the spacer fitted is inserted. With this configuration, the cable insertion hole can be easily manufactured.

[0025] [5] In the equipment direct connection terminal described in any one of [1] to [4] above, the spacer comprises: an equal-diameter portion having a first outer diameter uniform in the axial direction of the spacer when the spacer is not fitted onto the power cable; and a reduced-diameter portion provided between the equal-diameter portion and the tip of the spacer, having a second outer diameter that gradually decreases from the equal-diameter portion toward the tip of the spacer. This configuration makes it possible to stably reduce the insertion load of the power cable and to stably maintain insulation between the insulating cylinder and the spacer.

[0026] [6] In the equipment direct connection terminal described in any one of [1] to [4] above, the outer diameter of the spacer gradually decreases from the rear end to the front end in the axial direction of the spacer over the entire axial direction of the spacer. With this configuration, the spacer can be easily molded.

[0027] [7] Spacers according to other embodiments of the present disclosure are used in the equipment direct connection terminal described in any one of [1] to [6] above. According to this provision, the equipment direct connection terminal can be manufactured easily and stably.

[0028] [Details of Embodiments of the Disclosure] Embodiments of the Disclosure will now be described below with reference to the drawings. However, the Disclosure is not limited to these examples and is intended to include all modifications within the meaning and scope of the claims, as indicated by the claims.

[0029] <One Embodiment of the Present Disclosure> (1) Device Direct Connection Terminal The device direct connection terminal 10 according to this embodiment will be described with reference to Figure 1.

[0030] Note that in Figure 1, the power cable 100 is shown in a side view, not a cross-section. In Figure 1, some hatching of the cross-section has been omitted. In Figure 1, some parts of the bushing 820 and insulating plug 840 have been omitted.

[0031] In the following explanation, "axial direction" of the power cable 100 refers to the direction of the central axis of the power cable 100. "Radial direction" of the power cable 100 refers to the direction from the central axis of the power cable 100 toward the outer circumference. The same terms as those used for the power cable 100 may also be used for each layer constituting the power cable 100 and the spacer 400. In the following, "surface pressure" refers to the load per unit area.

[0032] As shown in Figure 1, the equipment direct connection terminal 10 of this embodiment is configured to connect a predetermined piece of equipment to a power cable 100. The equipment to be connected is, for example, a switchgear within a wind power generation facility.

[0033] The equipment direct connection terminal 10 of this embodiment includes, for example, an internal terminal 200, an insulating tube 300, a spacer 400, and insulating tape (corrosion-resistant layer, corrosion-resistant tape) 900.

[0034] (Power Cable) As shown in Figure 1, the power cable 100 is configured as a solid-insulated cable that is a high-voltage power transmission cable. Examples of power cables 100 include XLPE (Cross-Linked Polyethylene) cables. The base resin that constitutes the cable insulation layer 130 of the power cable 100, which will be described later, may be polypropylene as well as cross-linked polyethylene. The power cable 100 may be for AC or DC.

[0035] The applicable voltage of the power cable 100 is not limited. However, the power cable 100 may be configured to be applicable to voltages of 66 kV or higher, for example.

[0036] The power cable 100 has, for example, a conductor (cable conductor) 110, an internal semiconducting layer (not shown), a cable insulation layer 130, an external semiconducting layer 140, a cable shielding 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.

[0037] The power cable 100 is stripped in stages from the axial end of the conductor 110 toward the opposite side (so-called "step stripping"). That is, the conductor 110, the internal semiconducting layer of the cable, the cable insulation layer 130, the external semiconducting layer 140, the cable shielding layer, and the cable sheath 160 are exposed in this order from the axial end of the conductor 110 toward the opposite side.

[0038] (Internal Terminal) The internal terminal 200 is connected to the conductor 110 of the power cable 100 and is also configured to be connectable to a terminal (not shown) of the equipment. Specifically, the internal terminal 200 is configured as, for example, a compression terminal. The internal terminal 200 has, for example, a cylindrical portion 220 and a plate-shaped portion 240.

[0039] The cylindrical portion 220 has an insertion hole 222 into which the conductor 110 of the power cable 100 is inserted. The cylindrical portion 220 is compressed radially when the power cable 100 is inserted. As a result, the cylindrical portion 220 is configured to connect to the conductor 110 of the power cable 100.

[0040] The plate-shaped portion 240 is configured as a flat plate. The plate-shaped portion 240 is connected to the cylindrical portion 220 opposite to the opening of the insertion hole 222. The plate-shaped portion 240 has a through hole 242 that penetrates in the thickness direction of the plate-shaped portion 240. A connection terminal (not shown), such as a stud bolt connected to the terminal of a device, is inserted into the through hole 242 of the plate-shaped portion 240. The male threaded portion of the connection terminal protrudes from the plate-shaped portion 240 toward the plug fitting hole 316, which will be described later. A nut (not shown) is provided on the opposite side of the plate-shaped portion 240 from the connection terminal. The nut is tightened onto the male threaded portion of the connection terminal.

[0041] (Insulating Cylinder (Terminal Body, Insulating Unit, Rubber Unit)) The insulating cylinder 300 constitutes the main body of the directly-connected terminal 10 of the device. The insulating cylinder 300 is configured to maintain the insulation of the internal terminal 200 and the outside of the power cable 100.

[0042] The insulating cylinder 300 has, for example, a T-shaped outer shape 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.

[0043] The cable insertion hole 311 is, for example, linearly opened along the vertical part of the T-shaped insulating cylinder 300 inside the insulating cylinder 300. The power cable 100 in a state where the internal terminal 200 is connected and the spacer 400 described later is fitted is inserted into the cable insertion hole 311. The plate-like part 240 of the internal terminal 200 is disposed at the connection portion of the cable insertion hole 311, the bushing fitting hole 314, and the plug fitting hole 316.

[0044] In the present embodiment, the cable insertion hole 311 has a uniform inner diameter in the direction in which the power cable 100 is inserted in a portion where the power cable 100 with the spacer 400 fitted is inserted in a state where the power cable 100 with the spacer 400 fitted is not inserted. Thereby, the cable insertion hole 311 can be easily processed. In FIG. 1, a state is shown in which the cable insertion hole 311 is elastically deformed following the outer shape of the spacer 400 described later. The relationship between the outer diameter of the spacer 400 with respect to the cable insertion hole 311 will be described later.

[0045] The bushing fitting hole 314 is, for example, opened in a conical shape (truncated cone shape) whose diameter decreases from the first end to the center of the horizontal part of the T-shaped insulating cylinder 300 inside the insulating cylinder 300. The bushing 820 of the device elastically fits into the bushing fitting hole 314. Thereby, the terminal provided in the bushing 820 of the device is connected to the connection terminal fixed to the plate-like part 240 of the internal terminal 200.

[0046] The plug fitting hole 316 is formed, for example, in the insulating cylinder 300 in a conical shape (frustum of a cone shape) with a reduced diameter from the second end opposite to the first end of the horizontal portion of the T-shaped insulating cylinder 300 toward the center. An insulating plug 840 elastically fits into the plug fitting hole 316. The insulating plug 840 has, for example, a female screw portion from the center of the reduced diameter tip toward the rear end. The female screw portion of the insulating plug 840 is configured to be screwed onto the male screw portion of the connection terminal protruding from the plate-like portion 240 of the internal terminal 200.

[0047] The insulating cylinder 300 is divided into, for example, three parts with different electrical characteristics. Specifically, the insulating cylinder 300 has, 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.

[0048] The main body internal semiconductive layer 320 contains, for example, a 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. An example of the filler contained in the semiconductive rubber is carbon black.

[0049] The main body internal semiconductive layer 320 is provided, for example, so as to surround the outer periphery of the internal terminal 200 inserted into the cable insertion hole 311 and the power cable 100. The main body internal semiconductive layer 320 forms a part of the cable insertion hole 311, that is, it is exposed inside the cable insertion hole 311. The main body internal semiconductive layer 320 can relax the electric field around the internal terminal 200 and the conductor 110.

[0050] The main body internal semiconductive layer 320 has an end portion, for example, at a position in contact with the outer periphery of the spacer 400 described later.

[0051] The main body insulating layer 340 contains, for example, an insulating rubber (insulating resin). Examples of the insulating rubber include ethylene propylene rubber and silicone rubber.

[0052] The main body insulating layer 340 is provided, for example, to cover the outer circumference of the internal semiconducting layer 320 of the main body, and constitutes the main part of the insulating cylinder 300. The main body insulating layer 340, for example, together with the internal semiconducting layer 320 of the main body, constitutes a part of the cable insertion hole 311.

[0053] The external semiconducting layer 360 of the main body includes, for example, semiconducting rubber. The semiconducting rubber of the external semiconducting layer 360 of the main body is, for example, the same as the semiconducting rubber of the internal semiconducting layer 320 of the main body.

[0054] The external semiconducting layer 360 of the main body is provided, for example, so as 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 external semiconducting layer 360 of the main body is grounded.

[0055] (Spacer (adapter)) The spacer 400 is, for example, cylindrical in shape and fitted around the outer circumference of the power cable 100. The spacer 400 is configured to be interposed between, for example, the inner surface of the cable insertion hole 311 and the outer surface of the power cable 100.

[0056] The spacer 400 has, for example, an axial end and a rear end opposite to the end. When the spacer 400 is fitted onto the power cable 100, the conductor 110 of the power cable 100 is exposed from the axial end of the spacer 400.

[0057] The spacer 400 has, for example, a claw portion 410 at its axial end. The claw portion 410 protrudes radially inward from the spacer 400 and has an inner diameter smaller than the portion into which the power cable 100 is inserted. As a result, the claw portion 410 of the spacer 400 is configured to lock onto the end of the exposed cable insulation layer 130 in the power cable 100 into which the spacer 400 is fitted. Consequently, when the power cable 100 into which the spacer 400 is fitted is inserted into the cable insertion hole 311, the position of the spacer 400 within the cable insertion hole 311 can be determined, and displacement of the spacer 400 can be suppressed.

[0058] The spacer 400 is divided into two parts with different electrical properties, for example. Specifically, the spacer 400 in this embodiment has, for example, a spacer insulating layer 440 and a spacer external semiconducting layer 460. The spacer insulating layer 440 and the spacer external semiconducting layer 460 are molded together as a single cylindrical structure. The spacer insulating layer 440 and the spacer external semiconducting layer 460 are provided in this order from the axial front end to the rear end of the spacer 400.

[0059] The spacer insulating layer 440 includes, for example, an insulating rubber. Examples of insulating rubber include ethylene propylene rubber and silicone rubber.

[0060] The spacer insulating layer 440 is provided in the region including the tip of the spacer 400. The spacer insulating layer 440 is positioned to cover the outer circumference of the exposed cable insulating layer 130 when the spacer 400 is fitted onto the power cable 100. Furthermore, the spacer insulating layer 440 is positioned to contact a part of the main insulating layer 340 when the power cable 100 with the spacer 400 fitted onto it is inserted into the cable insertion hole 311. This makes it possible to maintain insulation between the main insulating layer 340 and the exposed cable insulating layer 130.

[0061] The outer semiconducting layer 460 of the spacer includes, for example, semiconducting rubber. The semiconducting rubber includes a base polymer and a filler. Examples of the base polymer of the semiconducting rubber include ethylene propylene rubber and silicone rubber. An example of the filler included in the semiconducting rubber is carbon black.

[0062] The outer semiconducting layer 460 of the spacer is, for example, in contact with the spacer insulating layer 440 and is provided in a region close to the axial rear end of the spacer 400.

[0063] The outer semiconducting layer 460 of the spacer has, for example, a cone shape. That is, the outer semiconducting layer 460 of the spacer has an inner diameter that gradually increases from the axial rear end of the spacer 400 toward the front end of the spacer 400. With this configuration, the outer semiconducting layer 460 of the spacer forms a so-called stress cone.

[0064] The spacer outer semiconducting layer 460 is positioned, for example, so as to contact the outer surface of the exposed cable outer semiconducting layer 140 of the power cable 100 when the power cable 100 with the spacer 400 fitted is inserted into the cable insertion hole 311. With this configuration, equipotential lines can be evenly distributed along the cone-shaped spacer outer semiconducting layer 460 around the exposed cable outer semiconducting layer 140 where a relatively high electric field is generated. As a result, electric field concentration can be suppressed around the exposed cable outer semiconducting layer 140.

[0065] The inner and outer diameters of the spacer 400 in this embodiment will be described in detail later.

[0066] (Tape layer) The equipment direct connection terminal 10 may have, for example, an insulating tape layer 900 to protect the exposed portion of the equipment direct connection terminal 10. Specifically, the tape layer 900 may be provided to cover an area including a part of the insulating cylinder 300, the rear end of the spacer 400 exposed outside the cable insertion hole 311, and the tip of the cable sheath 160 of the power cable 100.

[0067] (2) The configuration of the spacer 400 in this embodiment will be described with reference to Figures 1 and 2. Figure 2 shows the spacer 400 in a state where it is not fitted onto the power cable 100 and is not inserted into the cable insertion hole 311 of the insulating cylinder 300.

[0068] As shown in Figures 1 and 2, the inner shape of the spacer 400 (the inner shape of the part other than the claw portion 410) is, for example, cylindrical. The inner diameter of the spacer 400 is set to be slightly smaller than the outer diameter of the cable insulation layer 130 of the power cable 100. As a result, the inner circumferential surface of the spacer 400 is in close contact with the outer circumferential surface of the power cable 100.

[0069] On the other hand, in this embodiment, the outer shape of the spacer 400, at least near its tip, is, for example, frustoconical.

[0070] Specifically, the spacer 400 in this embodiment has an outer diameter that gradually decreases toward the axial end of the spacer 400, such that the surface pressure applied to the spacer 400 from the insulating cylinder 300 gradually decreases toward the axial end of the spacer 400. This makes it possible to reduce the insertion load required to insert the power cable 100 with the spacer 400 fitted into it into the cable insertion hole 311 of the insulating cylinder 300.

[0071] In this embodiment, the outer diameter of the spacer 400 is set such that, for example, at the position where the end of the internal semiconducting layer 320 of the main body contacts the outer circumference of the spacer 400, the surface pressure applied to the spacer 400 from the end of the internal semiconducting layer 320 of the main body is 0.05 MPa or more. As a result, even if the spacer 400 has the aforementioned frustoconical shape, insulation can be maintained at the interface between the insulating cylinder 300 and the spacer 400. The "surface pressure" referred to here is calculated based on, for example, the Young's modulus (longitudinal elastic modulus) and Poisson's ratio of the spacer 400, the outer diameter of the spacer 400, the Young's modulus (longitudinal elastic modulus) and Poisson's ratio of the insulating cylinder 300, and the inner diameter of the cable insertion hole 311 of the insulating cylinder 300.

[0072] In this embodiment, the outer diameter of the axial tip of the spacer 400 is greater than or equal to the inner diameter of the cable insertion hole 311, for example, when the spacer 400 is not inserted into the cable insertion hole 311. This ensures that even if the spacer 400 has the aforementioned frustoconical shape, the axial tip of the spacer 400 remains in elastic contact with the inner circumferential surface of the cable insertion hole 311 of the insulating cylinder 300. As a result, surface pressure can be guaranteed at the axial tip of the spacer 400, where the outer diameter is smallest.

[0073] In this embodiment, the spacer 400 is divided into two parts with different outer diameters, for example. Specifically, the spacer 400 has, for example, a portion with equal diameter 406 and a portion with reduced diameter 404.

[0074] The equal-diameter portion 406 has a uniform first outer diameter in the axial direction of the spacer 400 when the spacer 400 is not fitted onto the power cable 100. The equal-diameter portion 406 may have a first outer diameter that conforms to the outer diameter of the power cable 100 when the spacer 400 is fitted onto the power cable 100. That is, the equal-diameter portion 406 may be deformed to have slight irregularities that conform to the outer shape of the power cable 100 when the spacer 400 is fitted onto the power cable 100.

[0075] The reduced-diameter portion 404 is provided, for example, between the equal-diameter portion 406 and the axial end of the spacer 400. The reduced-diameter portion 404 has a second outer diameter that gradually decreases from the equal-diameter portion 406 toward the axial end of the spacer 400. The second outer diameter of the reduced-diameter portion 404 decreases linearly toward the axial end of the spacer 400.

[0076] In this embodiment, the spacer 400 has, for example, an inclined surface 402. In the spacer 400 of this embodiment, a conical inclined surface 402 is formed as the outer circumferential surface of the reduced diameter portion 404 described above. The inclined surface 402 is inclined with respect to the axial direction of the spacer 400, for example, such that the outer diameter of the spacer 400 gradually decreases toward the axial end of the spacer 400.

[0077] As shown in Figure 2, the inclination angle θ of the inclined surface 402 of the spacer 400 with respect to the axial direction is, for example, 0.1° or more and 1° or less, or 0.5° or more and 1° or less. By setting the inclination angle θ to 0.1° or more, or 0.5° or more, the surface pressure applied from the insulating cylinder 300 to the spacer 400 in the region near the axial tip of the spacer 400 can be stably reduced. On the other hand, by setting the inclination angle θ to 1° or less, it is possible to suppress the surface pressure applied from the insulating cylinder 300 to the spacer 400 from becoming excessively uneven along the inclined surface 402.

[0078] In this embodiment, the spacer 400 has, for example, an inflection point IP between the reduced-diameter portion 404 and the equal-diameter portion 406. Here, "inflection point IP" means a point where the inclination angle θ of the inclined surface 402 changes. The inflection point IP in this embodiment is provided around the entire circumference of the spacer 400, that is, the set of inflection points IP forms a circle centered on the central axis of the spacer 400.

[0079] In this embodiment, the inflection point IP may be positioned, for example, away from the end of the internal semiconducting layer 320 of the main body, with the power cable 100 fitted with the spacer 400 inserted into the cable insertion hole 311, and facing away from the axial end of the power cable 100. Here, the electric field tends to concentrate at the end of the internal semiconducting layer 320 of the main body. Therefore, by positioning the inflection point IP of the spacer 400 away from the end of the internal semiconducting layer 320 of the main body, the inflection point of the surface pressure can be moved away from the end of the internal semiconducting layer 320 where the electric field tends to concentrate. This makes it possible to stably maintain insulation between the insulating cylinder 300 and the frustoconical spacer 400.

[0080] In this embodiment, the inflection point IP may be located, for example, midway between the end of the internal semiconducting layer 320 and the end of the external semiconducting layer 460 of the spacer, when the power cable 100 with the spacer 400 fitted is inserted into the cable insertion hole 311. This allows the inflection point IP to be stably kept away from the ends of the internal semiconducting layer 320 and the external semiconducting layer 460 of the spacer, which are subject to high stress. From this viewpoint as well, the insulating properties can be stably maintained between the insulating cylinder 300 and the frustoconical spacer 400.

[0081] Because the spacer 400 of this embodiment has the above-described configuration, when the power cable 100 fitted with the spacer 400 is inserted into the cable insertion hole 311, an appropriate surface pressure can be applied to the power cable 100 from the insulating cylinder 300 via the spacer 400, according to the size (diameter) of the power cable 100.

[0082] (3) Summary of this embodiment This embodiment provides one or more of the following effects.

[0083] (a) In this embodiment, the spacer 400 has an outer diameter that gradually decreases toward the axial end of the spacer 400, such that the surface pressure applied to the spacer 400 from the insulating cylinder 300 gradually decreases toward the axial end of the spacer 400. This makes it possible to reduce the insertion load (hereinafter also referred to as "insertion load of the power cable 100" in this embodiment) when inserting the power cable 100 with the spacer 400 fitted into the cable insertion hole 311 of the insulating cylinder 300.

[0084] For example, even in the case of a direct-connection terminal 10 for high voltage applications, the power cable 100 fitted with the spacer 400 can be easily inserted into the cable insertion hole 311 of the insulating cylinder 300. As a result, it becomes possible to manufacture the direct-connection terminal 10 easily and stably.

[0085] (b) In this embodiment, the outer diameter of the spacer 400 is set such that the surface pressure applied to the spacer 400 from the end of the internal semiconducting layer 320 is 0.05 MPa or more at the position where the end of the internal semiconducting layer 320 contacts the outer circumference of the spacer 400.

[0086] As described above, electric fields tend to concentrate at the edges of the internal semiconducting layer 320 of the main body. When the surface pressure applied from the edges of the internal semiconducting layer 320 to the spacer 400 is low, the surface pressure cannot be maintained as the stress applied from the insulating cylinder 300 to the spacer 400 eases over time. As a result, the insulating properties at the edges of the internal semiconducting layer 320 may decrease.

[0087] In contrast, in this embodiment, the outer diameter of the spacer 400 is set such that the surface pressure applied to the spacer 400 from the end of the internal semiconducting layer 320 of the main body is 0.05 MPa or more. This ensures that even if the stress applied from the insulating cylinder 300 to the spacer 400 eases over time, the surface pressure can be maintained at a constant level or higher. As a result, even if the spacer 400 has the aforementioned frustoconical shape, insulation can be maintained at the interface between the insulating cylinder 300 and the spacer 400. In particular, insulation can be maintained near the end of the internal semiconducting layer 320 of the main body, where electric fields tend to concentrate.

[0088] (c) In this embodiment, the inclination angle θ of the inclined surface 402 of the spacer 400 with respect to the axial direction is 0.1° or more and 1° or less, or 0.5° or more and 1° or less. By setting the inclination angle θ to 0.1° or more, or 0.5° or more, the surface pressure applied from the insulating cylinder 300 to the spacer 400 in the region near the axial tip of the spacer 400 can be stably reduced. This makes it possible to stably reduce the insertion load of the power cable 100.

[0089] On the other hand, by setting the inclination angle θ to 1° or less, it is possible to suppress the excessive and uneven surface pressure applied from the insulating cylinder 300 to the spacer 400 along the inclined surface 402. As a result, even if the spacer 400 has the aforementioned frustoconical shape, the insulating properties can be stably maintained at the interface between the insulating cylinder 300 and the spacer 400.

[0090] (d) In this embodiment, the cable insertion hole 311 has a uniform inner diameter in the direction in which the power cable 100, into which the spacer 400 is fitted, is inserted. This makes it easy to manufacture the cable insertion hole 311.

[0091] In this embodiment, the cable insertion hole 311 has a uniform inner diameter in the direction into which the power cable 100 is inserted, while the spacer 400 has an outer diameter that gradually decreases toward the axial end of the spacer 400. This allows the surface pressure applied from the insulating cylinder 300 to the spacer 400 to decrease monotonically toward the axial end of the spacer 400. As a result, it is possible to design the insertion load of the power cable 100 and to stably reduce the insertion load of the power cable 100.

[0092] Furthermore, by creating a distribution in which the surface pressure applied from the insulating cylinder 300 to the spacer 400 decreases monotonically, it is possible to suppress the decrease in insulation performance caused by uneven surface pressure.

[0093] (e) In this embodiment, the spacer 400 is divided into two parts with different outer diameters. Specifically, the spacer 400 has an equal-diameter section 406 and a reduced-diameter section 404. This makes it possible to easily adjust the inclination angle θ on the inclined surface 402 of the reduced-diameter section 404 to the above-mentioned optimal range without making the range of the outer diameter of the spacer 400 excessively wide. As a result, it is possible to stably reduce the insertion load of the power cable 100 and stably maintain the insulation between the insulating cylinder 300 and the spacer 400.

[0094] (4) Modification of one embodiment The above-described embodiment can be modified as necessary, as shown below. Hereinafter, only elements that differ from the above-described embodiment will be described, and elements that are substantially the same as those described in the above-described embodiment will be denoted by the same reference numerals and their descriptions will be omitted.

[0095] <Modified Example> Referring to Figure 3, the modified example of the device-connected terminal 10 will be explained.

[0096] As shown in Figure 3, in the modified device direct connection terminal 10, the outer diameter of the spacer 400 gradually decreases from the rear end to the front end in the axial direction of the spacer 400, for example, along the entire axial direction of the spacer 400. In other words, the modified spacer 400 as a whole has the reduced diameter portion 404 of the above embodiment and does not have the equal diameter portion 406 of the above embodiment. In the modified example, the outer diameter of the spacer 400 decreases linearly toward the front end in the axial direction of the spacer 400.

[0097] According to the modified example, the spacer 400 can be easily molded.

[0098] Furthermore, in the modified version, the spacer 400 does not have an inflection point where the inclination angle θ changes. This allows the surface pressure applied from the insulating cylinder 300 to the spacer 400 to decrease monotonically towards the axial end of the spacer 400. In other words, surface pressure irregularities caused by inflection points can be suppressed. As a result, the insertion load of the power cable 100 can be designed more easily, and the insertion load of the power cable 100 can be stably reduced.

[0099] <Other Embodiments of the Disclosure> Although embodiments of the Disclosure have been described in detail above, the Disclosure is not limited to the embodiments described above and can be modified in various ways without departing from its essence.

[0100] In the embodiments described above, the case in which the internal terminal 200 is a compression terminal was described, but the disclosure is not limited to this case. The internal terminal 200 may be configured as a so-called shear bolt sleeve, in which a bolt inserted radially into the cylindrical portion 220 fastens and fixes the conductor 110 inside the cylindrical portion 220.

[0101] In the embodiments described above, the insulating cylinder 300 is shown as not having a so-called stress cone portion, but the disclosure is not limited to this case. If necessary, the insulating cylinder 300 may further have a cone-shaped semiconducting portion (stress cone portion) near the opening of the cable insertion hole 311, having an inner diameter that gradually widens away from the opening of the cable insertion hole 311.

[0102] <Note> The following are descriptions of the embodiments of this disclosure. The embodiments referred to by the numbers in brackets [] to which the following notes are dependent correspond to the embodiments described in <Embodiments of this Disclosure>.

[0103] [8] The outer diameter at the tip of the spacer is greater than or equal to the inner diameter of the cable insertion hole when the spacer is not inserted into the cable insertion hole. The device direct connection terminal according to any one of [1] to [6].

[0104] [9] The insulating cylinder has an internal semiconducting layer containing semiconducting rubber, the internal semiconducting layer is provided so as to surround the internal terminal inserted into the cable insertion hole and the outer circumference of the power cable, the internal semiconducting layer has an end at a position in contact with the outer circumference of the power cable, the spacer has an inflection point between the equal-diameter portion and the reduced-diameter portion, the inflection point is positioned away from the end of the internal semiconducting layer when the power cable with the spacer fitted is inserted into the cable insertion hole, and is directed away from the axial end of the power cable. The equipment direct connection terminal according to any one of [1] to [6] or [8].

[0105] 10 Direct connection terminal for equipment 100 Power cable 110 Conductor 130 Cable insulation layer 140 Cable outer semiconducting layer 160 Cable sheath 200 Internal terminal 220 Cylindrical part 222 Insertion hole 240 Plate-shaped part 242 Through hole 300 Insulating cylinder 311 Cable insertion hole 314 Bushing fitting hole 316 Plug fitting hole 320 Main body internal semiconducting layer 340 Main body insulation layer 360 Main body outer semiconducting layer 400 Spacer 402 Inclined surface 404 Reduced diameter part 406 Equal diameter part 410 Claw part 440 Spacer insulation layer 460 Spacer outer semiconducting layer 820 Bushing 840 Insulating plug 900 Tape layer IP Inflection point

Claims

1. A device direct connection terminal comprising: an internal terminal connected to a conductor of a power cable and configured to be connectable to a terminal of equipment; an insulating cylinder having a cable insertion hole into which the power cable with the internal terminal connected is inserted, and configured to maintain insulation of the internal terminal and the outside of the power cable; and a cylindrical spacer fitted so as to surround the outer circumference of the power cable and interposed between the inner surface of the cable insertion hole and the outer surface of the power cable, wherein the spacer has an outer diameter that gradually decreases toward the tip of the spacer so that the surface pressure applied to the spacer from the insulating cylinder gradually decreases toward the axial tip of the spacer.

2. The insulating cylinder has an internal semiconducting layer containing semiconducting rubber, the internal semiconducting layer is provided so as to surround the outer circumference of the internal terminal and the power cable inserted into the cable insertion hole, the internal semiconducting layer has an end at a position in contact with the outer circumference of the spacer, and the outer diameter of the spacer is set such that the surface pressure applied to the spacer from the end of the internal semiconducting layer is 0.05 MPa or more. The equipment direct connection terminal according to claim 1.

3. The equipment direct connection terminal according to claim 1 or claim 2, wherein the spacer has an inclined surface that is inclined with respect to the axial direction of the spacer such that the outer diameter of the spacer gradually decreases toward the tip of the spacer, and the inclination angle of the inclined surface with respect to the axial direction of the spacer is 0.1° or more and 1° or less.

4. The equipment direct connection terminal according to any one of claims 1 to 3, wherein the cable insertion hole has a uniform inner diameter in the direction in which the power cable into which the spacer is fitted is inserted.

5. The equipment direct connection terminal according to any one of claims 1 to 4, wherein the spacer comprises: an equal-diameter portion having a first uniform outer diameter in the axial direction of the spacer when the spacer is not fitted onto the power cable; and a reduced-diameter portion provided between the equal-diameter portion and the tip of the spacer, having a second outer diameter that gradually decreases from the equal-diameter portion toward the tip of the spacer.

6. The equipment direct connection terminal according to any one of claims 1 to 4, wherein the outer diameter of the spacer gradually decreases over the entire axial direction of the spacer from the rear end to the front end in the axial direction of the spacer.

7. A spacer used in a device direct connection terminal according to any one of claims 1 to 6.

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