Bushing

Abstract

To provide a bushing which can secure mechanical strength which can withstand use under high gas pressure without significantly changing the design.SOLUTION: A bushing includes: a bushing body formed of a resin material; an attachment flange which is formed integrally with the bushing body of a resin material and fastened to a device case by fixing bolts; and cylindrical embedded metal fittings each having a bolt through hole into which the fixing bolt is inserted. The attachment flange has: a flange body part whose planar view shape as seen in an axial direction is a regular hexagon and in which the embedded metal fittings are embedded near vertices of the regular hexagon; and a flange reinforcement part whose planar view shape as seen in the axial direction is a polygon including protruding parts and recessed parts formed alternately and having six-fold rotational symmetry and in which a bolt fixing surface for fastening the fixing bolts is formed protruding to the rear end side of the flange body part so as to be exposed from the recessed parts. A rounded portion having a curvature radius ranging 5 to 10 mm is provided at a connection portion between the bolt fixing surface and an outer peripheral surface of the flange reinforcement part.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to bushings.

Background Art

[0002] Conventionally, as cable terminal connections, gas-insulated terminal connections, oil-insulated terminal connections, air-insulated terminal connections, etc. are known. Generally, a cable terminal connection is formed by connecting a cable terminal portion to which a connection material is attached to a main body material (referred to as a "bushing") having a rigid insulator made of an epoxy resin or the like disposed on the outer periphery of an inner conductor and the inner conductor (for example, Patent Document 1).

[0003] The bushing described in Patent Document 1 is entirely formed of an epoxy resin and has a bushing main body and a mounting flange integrally formed with the bushing main body. The bushing is inserted into the equipment case of an electrical apparatus and attached to the equipment case by fixing fixing bolts inserted through the mounting flange to the equipment case.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, due to environmental concerns, dry gases are often used instead of sulfur hexafluoride gas (SF6 gas) as insulating gases inside equipment. Dry gases have lower insulating performance compared to SF6 gas, and it is necessary to set the gas pressure higher to obtain equivalent insulating performance. As a result, there is a concern that the equipment case may deform due to the gas pressure, and that external forces resulting from the deformation of the equipment case will act on the mounting flange of the bushing, causing damage to the mounting flange. In particular, in the bushing described in Patent Document 1, the mounting flange is made of epoxy resin and is prone to damage, so it is necessary to improve the structure of the mounting flange to have mechanical strength that can withstand external forces from the equipment case.

[0006] The purpose of this disclosure is to provide a bushing that can ensure mechanical strength sufficient for use under high gas pressure without requiring significant design changes. [Means for solving the problem]

[0007] The bushing relating to this disclosure is A bushing body made of resin material, A mounting flange, integrally formed from the resin material with the bushing body, is fastened to the equipment case by fixing bolts, The system comprises a cylindrical embedded fitting having a bolt through-hole through which the fixing bolt is inserted, The aforementioned mounting flange is The planar shape viewed from the axial direction is a regular hexagon. ru Flange body and The plan view shape as seen from the axial direction is a polygon with six rotational symmetry, in which convex and concave portions are formed alternately, and the flange reinforcing portion is formed protruding from the rear end side of the flange body such that the bolt fixing surface to which the fixing bolt is fixed is exposed from the concave portion, The aforementioned embedded fitting is embedded in the portion of the flange body corresponding to the bolt fixing surface, The connecting portion between the bolt fixing surface and the outer circumferential surface of the flange reinforcement is subjected to a radius of curvature of 5 to 10 mm. Occasionally, The flange reinforcement portion has a curved shape at the corner, which is the vertex of the plan view shape as seen from the axial direction. The bolt fixing surface has a washer housing portion that communicates with the bolt through hole and can accommodate a washer. The fixing bolt is inserted through the bolt through hole of the embedded fitting via the washer, The washer housing portion has an outer diameter larger than the outer diameter of the washer to the extent that it can accommodate the washer without the peripheral edge of the washer coming into contact with it. . [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide a bushing with high mechanical strength that can withstand use under high gas pressure without making significant design changes. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows a cable termination connection using a bushing according to an embodiment. [Figure 2] Figure 2 is a perspective view of the bushing from the rear end. [Figure 3] Figure 3 is a plan view of the bushing as seen from the rear end. [Figure 4] Figures 4A and 4B are enlarged views showing the fixing structure of the bushing. [Figure 5] Figure 5 shows the relationship between the radius of curvature at the corner of the flange reinforcement and the maximum stress generated in the mounting flange. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0011] Figure 1 is a cross-sectional view showing a cable termination connection 1 to which a bushing 10 according to an embodiment of this disclosure is applied. The cable termination connection 1 is a gas-filled termination connection applied to the connection portion of power equipment that requires airtightness, such as switchgear and transformers. The overall structure of the cable termination connection 1, other than the characteristic part of the mounting flange 12, is the same as that of a conventional cable termination connection, so it will be described briefly.

[0012] As shown in FIG. 1, the cable terminal connection portion 1 is constituted by mounting a cable terminal portion 20 on a bushing 10. Hereinafter, in the bushing 10, the side (the lower side in FIG. 1) where the cable terminal portion 20 is inserted will be referred to as the "rear end side", and the opposite side will be referred to as the "front end side".

[0013] The bushing 10 has a bushing body 11, a mounting flange 12, and an embedding fitting 33. The bushing body 11 and the mounting flange 12 are integrally formed of a hard plastic resin material with high mechanical strength (for example, epoxy resin, fiber reinforced plastic (FRP: Fiber Reinforced Plastics), etc.). In the embodiment, the bushing body 11 and the mounting flange 12 are formed of epoxy resin, and an internal conductor 13 is integrally embedded at the tip of the bushing 10, specifically, at the tip of the bushing body 11. The internal conductor 13 is embedded in the inner peripheral surface of the bushing body 11, for example, by mold molding.

[0014] The bushing body 11 has a hollow bell shape and houses the cable terminal portion 20 in the hollow portion 111. The bushing body 11 has an electric field relaxation portion 14 at the rear end. The electric field relaxation portion 14 functions as a shielding layer of the bushing 10, for example, by applying a conductive paint (not shown) to a predetermined position on the outer surface and electrically connecting the conductive paint to the equipment case 60.

[0015] The mounting flange 12 is integrally formed with the bushing body 11 by, for example, mold molding on the rear end side of the bushing body 11. The mounting flange 12 is a portion fastened to the rear end surface of the equipment case 60 by a fixing bolt 31. The mounting flange 12 has a flange main body portion 41 and a flange reinforcing portion 42.

[0016] The flange body portion 41 is formed so as to protrude radially outward from the bushing body 11 at the rear end side of the bushing body 11. The outer shape of the flange body portion 41 as viewed from the axial direction is larger than the inner shape of the opening 61 of the equipment case 60, so that the opening 61 of the equipment case 60 is closed by the flange body portion 41. Multiple cylindrical embedded fittings 33, which will be described later, for inserting fixing bolts 31 are embedded integrally with the flange body portion 41, for example by molding.

[0017] The flange reinforcement portion 42 is formed to protrude from the rear end side of the flange body portion 41. The structural design of the flange reinforcement portion 42 makes it possible to thin the flange body portion 41 while ensuring the mechanical strength required for the mounting flange 12.

[0018] The bushing 10 is inserted into the opening 61 of the equipment case 60 from the rear end, and the mounting flange 12 is bolted to the equipment case 60 via a sealing member 62 such as an O-ring, thereby airtightly attaching the bushing 10 to the equipment case 60. The bushing body 11 is located inside the equipment case 60 when the bushing 10 is attached to the equipment case 60. The flange body portion 41 of the mounting flange 12 closes the opening 61 of the equipment case 60. The detailed structure of the mounting flange 12 will be described later.

[0019] The internal conductor 13 is made of a conductive material suitable for electrical conduction, such as copper, aluminum, a copper alloy, or an aluminum alloy. The internal conductor 13 is positioned on the inner circumferential surface of the tip of the bushing body 11 and is drawn out towards the tip through the through hole of the bushing body 11.

[0020] The cable terminal section 20 is constructed by attaching connecting materials such as a conductor connection terminal 21, a stress cone 22, a compression device 23, a protective fitting 24, and a corrosion-resistant layer 25 to the tip of the power cable 50.

[0021] The power cable 50 is, for example, a 66 / 77kV class cable conductor 51 insulated with rubber or plastic, with a nominal cross-sectional area of ​​600 mm². 2 The above describes the power cable. In this embodiment, the power cable 50 is 66kV 2000mm 2 This is a power cable. The power cable 50 has, in order from the center outwards, a cable conductor 51, a cable insulator 52, an outer semiconducting cable layer 53, a cable shielding layer 54, and a cable sheath 55. At the cable terminal 20, each layer is exposed by stripping the power cable 50 in steps over a predetermined length from the tip.

[0022] The cable terminal 20 is assembled by stripping the tip of the power cable 50, attaching the protective fitting 24, compression device 23, and stress cone 22 to the power cable 50, and attaching the conductor connection terminal 21 to the cable conductor 51. The cable terminal 20 is attached to the bushing 10 by inserting the tip of the assembled cable terminal 20 into the receiving opening of the bushing 10 fixed to the equipment case 60 and securing it. Specifically, the compression device 23 is bolted to the rear end face of the mounting flange 12 of the bushing 10 while compressing the spring (no reference numerals) of the compression device 23, and the protective fitting 24 is bolted to the rear end face of the compression device 23. A corrosion-resistant layer 25 for waterproofing is placed at the rear end of the protective fitting 24.

[0023] With the cable end portion 20 attached to the bushing 10, the tip of the stress cone 22 is pressed against the inner wall surface of the hollow portion 111 of the bushing body 11. The conductor connection terminal 21 is electrically connected to the internal conductor 13 via a contact 15 (e.g., a tulip contact). The cable termination connector 1 can be assembled with relatively simple work using plug-in connections.

[0024] Figure 2 is a perspective view of the bushing 10 from the rear end. Figure 3 is a plan view of the bushing 10 from the rear end. Figures 4A and 4B are enlarged views showing the fixing structure of the bushing 10. Figure 4A shows the mounting flange 12 without fixing bolts 31 and washers 32, while Figure 4B shows the mounting flange 12 with fixing devices in place. In Figures 2 and 3, the connecting portion 43, which is one of the characteristic parts of the mounting flange 12, is shown with shading. Also, the lines showing the internal structure of the bushing 10 that appear inside the receiving opening of the bushing 10 on the rear end surface of the flange reinforcement portion 42 are omitted for the sake of explanation.

[0025] The structure of the mounting flange 12 will be described in detail with reference to Figures 2, 3, 4A, and 4B. As shown in Figures 2 and 3, the mounting flange 12 has a two-stage structure consisting of a flange body 41 and a flange reinforcing portion 42. The mounting flange 12 has a structure that is symmetrical six times with respect to the axial direction as the axis of rotation.

[0026] A fixing bolt 31 is secured to the bolt fixing surface 411 at the rear end of the flange body 41 via a washer 32. The bolt fixing surface 411 is formed at the rear end surface of the flange body 41. In Figure 4B of the embodiment, both a flat washer at the front end and a spring washer at the rear end are arranged on the washer 32. The bolt fixing surface 411 is the part where the flange reinforcement portion 42 is not formed and is exposed from the recess 423 of the flange reinforcement portion 42.

[0027] The flange body 41 has a regular hexagonal shape when viewed from the axial direction. The vertices of the hexagon are chamfered curved surfaces. The outer diameter R1 of the flange body 41 is, for example, 250 to 350 mm. The outer diameter R1 of the flange body 41 is the diameter of the circumscribed circle of the regular hexagon and is the same as the length of the diagonal of the regular hexagon that makes up the outer shape of the flange body 41. The thickness t of the flange body 41 is 30 to 50 mm.

[0028] Near the vertices of the regular hexagon of the flange body 41, bolt through-holes 412 through which fixing bolts 31 are inserted are located. The bolt through-holes 412 are formed by through-holes in cylindrical embedded fittings 33, which are arranged on the same circumference centered on the axial direction of the bushing 10. In this embodiment, a total of 12 bolt through-holes 412 are arranged, two on each of the six bolt fixing surfaces 411 of the flange body 41.

[0029] The bolt fixing surface 411 has a circular washer housing portion 413 recessed towards the tip, and a bolt through hole 412 is provided in this washer housing portion 413. The outer diameter of the washer housing portion 413 is larger than the outer diameter of the washer 32, allowing the washer 32 to be accommodated without its peripheral edge making contact. Since the washer 32 does not come into contact with the corners of the bolt fixing surface 411 (the open ends of the washer housing portion 413), no external force is applied during the fastening of the fixing bolt 31, thus preventing damage such as cracks or chips from occurring in the flange body portion 41 starting from the corners of the bolt fixing surface 411.

[0030] The bolt through-hole 412 is formed by the through-hole of the cylindrical embedded fitting 33 embedded in the flange body portion 41. The embedded fitting 33 is pre-molded and embedded such that its front end face is flush with the front end face of the flange body portion 41, and its rear end face is flush with the front end face of the washer housing portion 413.

[0031] On the bolt fixing surface 411, the two bolt through holes 412 are positioned symmetrically. Specifically, the distance from each of the two bolt through holes 412 to the adjacent protrusion 422 is the same. This equalizes the stress generated in the mounting flange 12 and suppresses the maximum stress, thereby improving the overall mechanical strength of the mounting flange 12.

[0032] The flange reinforcement portion 42 is formed projecting from the rear end side of the flange body portion 41. The flange reinforcement portion 42 has a substantially cylindrical body portion 421 and six protrusions 422 arranged at equal intervals in the circumferential direction on the outer surface of the body portion 421. That is, the flange reinforcement portion 42 has a plan view shape when viewed from the axial direction, which is a polygon with six rotational symmetry around the axial direction as the axis of rotation, with protrusions 422 and recesses 423 formed alternately. The protrusions 422 function as ribs, thereby increasing the mechanical strength of the mounting flange 12 without increasing the thickness of the flange body portion 41, and effectively preventing deformation such as warping and twisting.

[0033] The flange reinforcement portion 42 is inscribed within the flange body portion 41 in a plan view from the axial direction. In other words, the outer diameter R2 of the flange reinforcement portion 42 is the same as the diameter of the inscribed circle of the regular hexagon, which is the plan view shape of the flange body portion 41. If the outer diameter of the body portion 421 is R3, the protruding length of the convex portion 422 is expressed as (R2-R3) / 2. The protruding length of the convex portion 422 is not particularly limited, as long as there is enough space to secure the bolt fixing surface 411 of the flange body portion 41, even if the radius of curvature of the R processing described later is 5 to 10 mm.

[0034] Furthermore, the connecting portion 43 between the rear end surface of the flange body portion 41 (specifically, the bolt fixing surface 411 in this embodiment) and the outer circumferential surface of the flange reinforcement portion 42 is given an R-shape. The radius of curvature of the R-shape applied to the connecting portion 43 is 5 to 10 mm. By applying an R-shape with a radius of curvature of 5 to 10 mm to the connecting portion 43, stress concentration in the flange reinforcement portion 42 is significantly suppressed compared to when an R-shape of 2 mm is applied, and the overall mechanical strength of the mounting flange 12 is improved.

[0035] Generally, areas such as the connecting portion 43 tend to concentrate stress, so they are often given a rounded edge (R-shaped). In this embodiment, it has been found that by applying a rounded edge (R-shaped), not only is stress concentration in the connecting portion 43 suppressed, but by appropriately setting the radius of curvature, the maximum stress generated in the mounting flange 12 can be reduced, thereby improving the overall mechanical strength of the mounting flange 12. As a result, the radius of curvature is set to 5 to 10 mm. This makes it possible to ensure mechanical strength that can withstand use under high gas pressure without increasing the thickness of the flange body portion 41.

[0036] Furthermore, in this embodiment, when the radius of curvature of the connecting portion 43 is set to 5 to 10 mm, the corner portions 424 and 425, which are the vertices of the plan view shape of the flange reinforcement portion 42, are also formed in a curved shape in order to secure space for the bolt fixing surface 411. Note that the radius of curvature of the corner portions 424 and 425 does not have to be 5 to 10 mm.

[0037] Figure 5 shows the results of a simulation of the relationship between the radius of curvature of the connected section 43 and the maximum stress generated in the mounting flange 12.

[0038] As shown in Figure 5, increasing the radius of curvature of the connecting portion 43 can reduce the maximum stress generated in the mounting flange 12. When the radius of curvature of the connecting portion 43 is 5 mm or more, the maximum stress can be suppressed to 60% or less compared to when the radius of curvature is 2 mm. In particular, when the radius of curvature is 7 mm or more, the maximum stress can be suppressed to 50% or less compared to when the radius of curvature is 2 mm, which is more preferable.

[0039] As shown in Figure 5, when the radius of curvature is 7 mm or more, the effect of reducing the maximum stress is almost saturated. That is, the maximum stress generated in the mounting flange 12 does not decrease much further even when the radius of curvature is increased, and remains almost constant. However, when the radius of curvature of the connecting portion 43 is less than 5 mm, the effect of reducing the maximum stress generated in the mounting flange 12 is small, and the effect of suppressing damage to the epoxy resin forming the mounting flange 12 is small. Also, when the radius of curvature of the connecting portion 43 is greater than 10 mm, the protrusion 422 of the flange reinforcement portion 42 becomes small, and the effect of the protrusion 422 as a rib becomes small. Therefore, the radius of curvature of the connecting portion 43 is preferably 5 to 10 mm, and more preferably 7 to 10 mm. This makes it possible to increase the mechanical strength of the mounting flange 12.

[0040] As described above, the bushing 10 according to the embodiment is equipped with the following features individually or in appropriate combinations.

[0041] Specifically, it comprises a bushing body 11 made of resin material, a mounting flange 12 integrally formed with the bushing body 11 from the same resin material and fastened to the equipment case 60 by fixing bolts 31, and a cylindrical embedded fitting 33 having a bolt through hole 412 through which the fixing bolts 31 are inserted. The mounting flange 12 has a flange body portion 41 in which the shape of the plan view when viewed from the axial direction is a regular hexagon and the embedded fitting 33 is embedded near the vertices of the regular hexagon, and a flange reinforcing portion 42 in which the shape of the plan view when viewed from the axial direction is a polygon with six rotational symmetry in which convex portions 422 and concave portions 423 are formed alternately and the flange reinforcing portion 42 is formed protruding from the rear end side of the flange body portion 41 so that the bolt fixing surface 411 to which the fixing bolts 31 are fixed is exposed from the concave portion 423, and the connecting portion 43 between the bolt fixing surface 411 and the outer circumferential surface of the flange reinforcing portion 42 is given a radius of curvature of 5 to 10 mm. The radius of curvature of the connected portion 43 is preferably 7 to 10 mm.

[0042] The bushing 10 suppresses stress concentration in the flange reinforcement portion 42, improving the overall mechanical strength of the mounting flange 12. This makes it possible to ensure sufficient mechanical strength to withstand use under high gas pressure without requiring significant design changes such as increasing the thickness of the flange body portion 41.

[0043] Furthermore, in the bushing 10, a washer housing portion 413 is formed in a recess shape on the bolt fixing surface 411, communicating with the bolt through hole 412 and capable of accommodating a washer 32. The fixing bolt 31 is inserted through the bolt through hole 412 of the embedded fitting 33 via the washer 32. The washer 32 does not come into contact with the corner of the bolt fixing surface 411 (the open end of the washer housing portion 413), and no external force is applied during the fastening of the fixing bolt 31. This prevents damage such as cracks or chips from occurring in the flange body portion 41 starting from the corner of the bolt fixing surface 411, making it even more suitable for use under high gas pressure.

[0044] Furthermore, in the bushing 10, two bolt through holes 412 are positioned symmetrically on the bolt fixing surfaces 411 exposed from each recess 423. This equalizes the stress generated in the mounting flange 12 and suppresses the maximum stress, thereby improving the overall mechanical strength of the mounting flange 12.

[0045] Furthermore, in the bushing 10, the outer diameter of the flange body is 250 to 350 mm. This allows the connecting portion 43 to be given a radius of curvature of 5 to 10 mm without interfering with other components (for example, bolt through holes 412).

[0046] Although the present invention has been specifically described above based on embodiments, the present invention is not limited to the above embodiments and can be modified without departing from its spirit.

[0047] The bushing according to the present invention can be widely applied not only to the gas termination connection of power equipment in the embodiment, but also to so-called prefabricated cable termination connections, such as air-based termination connections, gas-based termination connections, and oil-based termination connections. Furthermore, in the case of a cable termination connection using the bushing according to the present invention, it may be an outer cone type in which a rubber block insulator is attached to the outside of the bushing, rather than a so-called inner cone type in which a stress cone is inserted into the bushing as in the embodiment.

[0048] Furthermore, in the present invention, the term "bushing" includes not only the main body material of a cable termination connection as in the embodiment, but also bushings for power equipment that are not cable termination connections. In other words, the present invention can be applied to bushings in which the bushing body and the mounting flange are integrally formed from an insulating material (for example, a hard plastic resin material with high mechanical strength such as epoxy resin or FRP).

[0049] Furthermore, although the embodiments described the case in which the bushing according to the present invention is applied to a 66 / 77kV class cable termination connection, the voltage class used is not particularly limited, and it may be applied to cable termination connections of, for example, 110kV or 154kV or higher.

[0050] Furthermore, although the embodiment described the case in which the electric field mitigation section 14 is formed by applying conductive paint, it may also be formed by embedding a shielding fitting inside the bushing body 11. In addition, in the case of a cable termination connection using the bushing according to the present invention, the connection configuration between the cable conductor 51 and the internal conductor 13 is not limited to the tulip contact type as in the embodiment, but may be a multi-contact type, for example.

[0051] Furthermore, although the embodiment described the bushing 10 as being attached to the equipment case 60, it is not limited to this configuration, and may be attached to a sealed case. For example, it may be used as a so-called epoxy seat for an air-insulated terminal connection, or it may be attached to a test case.

[0052] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0053] 1. Cable termination connection 10 Bushings 11 Bushing body 12 Mounting flange 13. Inner conductor 31 Fixing bolts 32 Washer 33 Recessed mounting hardware 41 Flange body 42 Flange reinforcement section 43 Continuous part 60 Equipment Cases 411 Bolt fixing surface 412 Bolt through holes 422 Convex part 423 recess 424, 425 Corner section

Claims

1. A bushing body made of resin material, A mounting flange, integrally formed from the resin material with the bushing body, is fastened to the equipment case by fixing bolts, The system comprises a cylindrical embedded fitting having a bolt through-hole through which the fixing bolt is inserted, The aforementioned mounting flange is The flange body has a regular hexagonal shape when viewed from the axial direction in plan view, The plan view shape as seen from the axial direction is a polygon with six rotational symmetry, in which convex and concave portions are formed alternately, and the flange reinforcing portion is formed protruding from the rear end side of the flange body such that the bolt fixing surface to which the fixing bolt is fixed is exposed from the concave portion, The aforementioned embedded fitting is embedded in the portion of the flange body corresponding to the bolt fixing surface, The connecting portion between the bolt fixing surface and the outer circumferential surface of the flange reinforcement is given a radius of curvature of 5 to 10 mm. The flange reinforcement portion has a curved shape at the corner, which is the vertex of the plan view shape as seen from the axial direction. The bolt fixing surface has a washer housing portion that communicates with the bolt through hole and can accommodate a washer. The fixing bolt is inserted through the bolt through hole of the embedded fitting via the washer, The washer housing portion has an outer diameter larger than the outer diameter of the washer to the extent that it can accommodate the washer without the peripheral edge of the washer coming into contact with it. Bushing.

2. The radius of curvature is 7 to 10 mm. The bushing according to claim 1.

3. In the bolt fixing surface exposed from each of the recesses, two bolt through holes are arranged symmetrically with respect to the diagonal of the regular hexagon passing through the bolt fixing surface. The bushing according to claim 1.

4. The outer diameter of the flange body is 250 to 350 mm. The bushing according to claim 1.

5. The aforementioned resin material is an epoxy resin. The bushing according to claim 1.

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