Cable Termination Connection

Abstract

To provide a cable end terminal connection part which is preferably as an air end terminal connection part of a power cable of an ultra high pressure.SOLUTION: A cable end terminal connection part comprises: a porcelain tube; an insulation unit that includes a small diameter part on a tip end side and a large diameter part on a rear end side, and is arranged in the porcelain tube; a magnetic field relaxation part that is attached to the outer peripheral surface of the small diameter part; a fixing metal fitting that is arranged on the rear end side of the porcelain tube; an insulation medium that is sealed between the porcelain tube and the insulation unit; and a cable terminal part that is connected to the rear end side of the large diameter part. The insulation unit includes: an inner conductor extended to a shaft direction; a hard type insulation cylinder arranged on the outer peripheral surface of the inner conductor; a shielding part that is formed on the outer peripheral surface of the insulation cylinder so that the tip end is connected to the conductive part of the magnetic field relaxation part. The inner conductor is electrically connected to a conductive leading rod projected to the outer part so as to penetrate an upper metal fitting of the porcelain tube. The shielding part is formed at an intermediate position of the small diameter part from the large diameter part of the insulation unit, and the large diameter part is projected from the end part on the rear end side of the porcelain tube.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a cable termination connection part, and in particular to a technique suitable for an outdoor termination connection part of an extra-high voltage power cable. [Background technology]

[0002] Conventionally, air termination connections that provide air insulation using a porcelain tube have been known as cable termination connections installed at the end of a power cable (see, for example, Patent Documents 1 to 4), and are mainly classified into prefabricated type, rubber block type, and direct mold type based on their configuration.

[0003] In the cable termination disclosed in Patent Document 1, a conductor lead rod exposed at the tip side of the porcelain tube is compressed and connected to the end of the cable conductor of the power cable in the porcelain tube. A stress cone (also called a pre-molded insulator) for electric field relaxation, which is manufactured in advance at a factory, is attached to the power cable at the construction site on the cable insulation exposed by step stripping, thereby realizing electric field relaxation near the end of the cable outer semiconductive layer. The stress cone is pressed and fixed by a compression device against an epoxy seat inserted and fixed at the bottom inside the porcelain tube. An air termination with such a structure is called a prefabricated type. In a prefabricated air termination, an insulating medium such as insulating oil (e.g., silicone oil) is generally filled in the porcelain tube.

[0004] In the cable terminations disclosed in Patent Documents 2 and 3, the conductor pull-out rod exposed at the tip of the porcelain tube is compressed and connected to the end of the cable conductor of the power cable. A cold-shrinkable rubber block manufactured in advance at a factory is attached to the power cable at the construction site on the cable insulation exposed by the step stripping, thereby realizing electric field relaxation near the end of the cable outer semiconductive layer. This type of air termination is called a rubber block type because it does not have a compression device for pressing the epoxy seat and stress cone in the porcelain tube as in the prefabricated air termination, but has a structure in which the cold-shrinkable rubber block is placed at a specific position in the porcelain tube to relax the electric field. The porcelain tube used in the rubber block type air termination may be either a porcelain tube (see Patent Document 3) or a polymer porcelain tube (also called a composite porcelain tube, see Patent Document 2), and generally, an insulating medium such as insulating oil (e.g., silicone oil) is filled in the porcelain tube.

[0005] The cable termination disclosed in Patent Document 4 has an inner conductor, insulating tube, and polymer jacket integrally formed, and does not use any oil or gas for insulation as in the prefabricated outdoor termination and rubber block outdoor termination described above. This type of completely dry, solid-insulated outdoor termination is called a direct mold type. The direct mold type outdoor termination described in Patent Document 4 has a plug-in structure in which a cable terminal with a connecting material such as a conductor connecting terminal attached is attached to a cable receiving section at the rear end of the insulating tube by plugging it in. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2000-261948 A [Patent Document 2] Patent No. 5804948 [Patent Document 3] Patent No. 4685908 [Patent Document 4] JP 2017-184458 A Summary of the Invention [Problem to be solved by the invention]

[0007] In the above-mentioned air termination where air insulation is performed using a porcelain tube, the effective insulation length (the length of the porcelain tube body where the cap portion is formed) is set so as to ensure insulation performance such as lightning impulse withstand voltage. Therefore, in order to accommodate ultra-high voltage power cables, the porcelain tube must be made longer. For example, in the case of a 275kV class ultra-high voltage cable, a porcelain tube with a length of 3500mm or more is required.

[0008] However, in the case of prefabricated or rubber block type outdoor terminations, it is necessary to perform cable end processing at the construction site to a length that is approximately the same as the porcelain tube, so as the porcelain tube becomes longer, the time required for cable end processing also becomes longer, and construction time becomes longer. Also, in the case of direct mold type outdoor terminations, the insulating tube, which is a cast product, becomes longer in order to meet the effective insulation length required for extra-high voltage, and residual stress generated in the insulating tube during the manufacturing process increases, and there is a risk of quality deterioration due to sink marks (molding defects such as distortions and dents on the surface). As such, it is difficult for conventional outdoor terminations to be used with extra-high voltage power cables.

[0009] An object of the present invention is to provide a cable termination suitable as an outdoor termination for an extra-high voltage power cable. [Means for solving the problem]

[0010] The cable termination according to the present invention comprises: a porcelain tube having a porcelain tube body having a cap portion formed on an outer peripheral surface thereof, an upper metal fitting disposed on a front end side of the porcelain tube body, and a lower metal fitting disposed on a rear end side of the porcelain tube body; an insulating unit disposed within the porcelain tube, the insulating unit having a small diameter portion formed in a straight barrel shape at a front end side, an inclined portion expanding in diameter from the small diameter portion toward a rear end side, and a large diameter portion connected to the rear end side of the inclined portion and having an outer diameter larger than that of the small diameter portion; an electric field mitigation portion made of an elastic body attached to an outer circumferential surface of the small diameter portion and integrally formed with an insulating portion and a conductive portion connected to a rear end side of the insulating portion; A fixing metal fitting disposed on a rear end side of the porcelain tube; an insulating medium sealed between the porcelain bushing and the insulating unit; a cable terminal portion connected to a rear end side of the large diameter portion, the insulating unit includes an inner conductor extending in an axial direction, a hard insulating tube disposed on an outer circumferential surface of the inner conductor, and a shielding portion formed on an outer circumferential surface of the insulating tube such that a tip of the shielding portion is connected to the conductive portion of the electric field mitigation portion, the inner conductor is electrically connected to a conductor lead rod that penetrates the upper metal fitting and protrudes from the inside to the outside of the porcelain tube, the shielding portion is formed across an intermediate position between the large diameter portion and the small diameter portion of the insulating unit, The large diameter portion protrudes from the rear end of the porcelain tube. Effect of the Invention

[0011] According to the present invention, there is provided a cable termination suitable as an outdoor termination for an extra-high voltage power cable. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view showing a cable connection portion according to an embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged view of the cable receiving portion and its periphery. [Diagram 3] FIG. 3 is a diagram showing the relationship between the position of the electric field mitigation portion and the lightning impulse withstand voltage. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0014] Fig. 1 is a cross-sectional view showing a cable connecting end 1 according to an embodiment of the present invention, Fig. 2 is an enlarged view of the periphery of a cable receiving portion 24 in the cable connecting end 1.

[0015] 1 and 2, the cable termination connection part 1 includes a porcelain tube 10, an insulating unit 20, an electric field mitigation part 30, a fixing metal fitting 41, a terminal mounting metal fitting 42, an insulating medium 43, a conductor pull-out rod 44, and a cable terminal part 50. In the following description, the side from which the conductor pull-out rod 44 is pulled out is referred to as the "front end side," and the side to which the cable terminal part 50 is attached is referred to as the "rear end side."

[0016] The porcelain tube 10 has a porcelain tube body 11 having a cap portion 11a formed on the outer circumferential surface, an upper metal fitting 12 disposed on the front end side of the porcelain tube body 11, and a lower metal fitting 13 disposed on the rear end side of the porcelain tube body 11. The porcelain tube body 11 may be, for example, a porcelain tube, or a polymer porcelain tube (also called a composite porcelain tube) in which a polymer coating made of a polymer insulating material such as silicone rubber is integrally formed on the outside of a cylindrical body made of fiber reinforced plastics (FRP). The length of the porcelain tube body 11, i.e., the effective insulation length, is set so as to satisfy the lightning impulse withstand voltage required for the cable termination connection part 1.

[0017] The insulating unit 20 has an inner conductor 21 extending in the axial direction, an insulating tube 22 disposed on the outer peripheral surface of the inner conductor 21, and a shielding portion 23 formed on the outer peripheral surface of the insulating tube 22, and functions as a reinforcing insulating portion of the cable termination connection portion 1. The inner conductor 21 and the insulating tube 22 are integrally formed by molding. The shielding portion 23 is formed, for example, by applying a conductive paint to the outer peripheral surface of the insulating tube 22. The shielding portion 23 formed by the conductive paint applied to the outer peripheral surface of the insulating tube 22 is represented by a thick line in FIG. 1 and by a dashed line in FIG. 2. In FIG. 2, in order to avoid overlapping with other lines and making it difficult to see, for convenience of explanation, the dashed line representing the shielding portion 23 (conductive paint) is shown inside the solid line representing the insulating tube 22.

[0018] The insulating unit 20 is divided into a small diameter portion 20A formed in a straight barrel shape at the front end side, an inclined portion 20B expanding in diameter from the small diameter portion 20A toward the rear end side, and a large diameter portion 20C formed in a straight barrel shape connected to the rear end side of the inclined portion 20B. The large diameter portion 20C has a larger outer diameter than the small diameter portion 20A. The insulating unit 20 is arranged so that the small diameter portion 20A is inside the porcelain tube 10 and the large diameter portion 20C is outside the porcelain tube 10. In this embodiment, the insulating unit 20 is arranged so that the rear end side of the inclined portion 20B is located at the rear end of the porcelain tube 10. In addition, in this embodiment, the front end side of the small diameter portion 20A has a shape that reduces in diameter toward the front end side. This makes it easier to insert the electric field mitigation portion 30 formed of a cylindrical elastic body described later into the insulating unit 20.

[0019] The inner conductor 21 is made of a conductive material suitable for electrical conduction, such as copper, aluminum, a copper alloy, or an aluminum alloy. The inner circumferential surface on the rear end side of the inner conductor 21 arranged in the large diameter portion 20C of the insulating unit 20 is exposed from the insulating tube 22, and is provided with a conductor insertion portion 21a for electrically connecting the cable conductor 511. The end on the front end side of the inner conductor 21 passes through the insulating tube 22 and is connected to the conductor lead rod 44.

[0020] The insulating tube 22 is made of a hard plastic resin material (e.g., epoxy resin or FRP) with high mechanical strength. A cone-shaped terminal insertion portion 22a that receives the cable terminal portion 50 is provided on the rear end side of the insulating tube 22 arranged in the large diameter portion 20C of the insulating unit 20. The terminal insertion portion 22a communicates with the conductor insertion portion 21a of the inner conductor 21. The conductor insertion portion 21a and the terminal insertion portion 22a form a cable receiving portion 24 to which the cable terminal portion 50 is attached.

[0021] In this embodiment, the outer diameter of the large diameter portion 20C of the insulating unit 20 (effectively the outer diameter of the rear end side of the insulating tube 22 located at the large diameter portion 20C, since the thickness of the shielding portion 23 is less than 1 mm) is set to be approximately the same as the inner diameter of the porcelain tube 10, but may be larger than the inner diameter of the porcelain tube 10. From the perspective of electric field design, it is advantageous for the large diameter portion 20C of the insulating unit 20, where the cable receiving portion 24 is formed, to have a larger outer diameter. Since the large diameter portion 20C of the insulating unit 20 is disposed outside the porcelain tube 10, it can be designed to have an outer diameter appropriate for electric field design without being limited by the inner diameter of the porcelain tube 10.

[0022] Furthermore, the insulating tube 22 is formed in an R-shape at the inclined portion 20B of the insulating unit 20 so as to gradually taper from the large diameter portion 20C toward the small diameter portion 20A. That is, the outer shape of the insulating tube 22 is a shape that does not have any electrical protrusions that induce electric field concentration. As a result, even if the shielding portion 23 is formed on the outer circumferential surface of the insulating tube 22 at the inclined portion 20B of the insulating unit 20, the electric field between the internal conductor 21 and the shielding portion 23 does not concentrate, and the internal electric field of the insulating tube 22 can be made uniform.

[0023] The shielding portion 23 is formed on the outer peripheral surface of the insulating tube 22, from the rear end of the large diameter portion 20C of the insulating unit 20 to the intermediate position of the small diameter portion 20A. The intermediate position is not particularly limited as long as it is a position halfway along the longitudinal direction of the small diameter portion 20A. By providing the shielding portion 23, the electric field is not concentrated between the internal conductor 21 and the shielding portion 23, and the electric field inside the insulating tube 22 is made uniform, thereby stabilizing the electrical characteristics.

[0024] The electric field mitigation section 30 is formed of a cylindrical elastic body having an insulating section 31 on the tip side and a conductive section 32 on the rear end side. The insulating section 31 is concentrically connected to the conductive section 32 at the rear end side, and is formed into a cylindrical shape from an insulating rubber material such as ethylene propylene rubber (EP rubber). The conductive section 32 has a bell-mouth curved shape at the tip end side, gradually expanding in diameter from the inner periphery near the tip end side toward the tip side. The conductive section 32 is formed into a cylindrical shape from a semiconductive rubber material such as semiconductive EP rubber, and is connected to the insulating section 31 at the tip side part of the inner periphery and at the part from the tip side of the outer periphery to the rear end side. The inner periphery of the conductive section 32 is exposed as the inner periphery of the electric field mitigation section 30 except for the tip side part integrated with the insulating section 31, and is connected to the inner periphery of the insulating section 31. The insulating section 31 and the conductive section 32 are integrally formed by molding. In the embodiment shown in FIG. 1, the electric field mitigating portion 30 has a cylindrical shape with the rear end side of the conductive portion 32 exposed, but the outer shape is not particularly limited.

[0025] The electric field mitigation portion 30 is disposed on the outer peripheral surface of the small diameter portion 20A of the insulating unit 20. Specifically, the electric field mitigation portion 30 is disposed so that the inner peripheral surface of the conductive portion 32 and the shielding portion 23 are overlapped so as to be conductive with each other, and the tip of the shielding portion 23 does not protrude from the inner peripheral surface of the conductive portion 32. The electric field mitigation portion 30 suppresses electric field concentration at the tip of the shielding portion 23, and relieves electrical stress on the insulating tube 22.

[0026] Here, if the tip position of the conductive part 32 in the axial direction changes, the electric field appearing on the surface of the porcelain tube 10 changes, which affects the surface flashover, so the electric field mitigation part 30 needs to be disposed at an appropriate position. In this embodiment, the tip position of the conductive part 32 is set so that the distance from the end part on the rear end side of the porcelain tube body 11 is 10 to 27% of the effective insulation length of the porcelain tube body 11. As shown in FIG. 3, the lightning impulse withstand voltage changes depending on the tip position of the conductive part 32. Specifically, the lightning impulse withstand voltage when the distance from the end part on the rear end side of the porcelain tube body 11 to the tip position of the conductive part 32 is about 21% of the length of the porcelain tube body 11 is used as a reference, and the lightning impulse withstand voltage decreases as the distance from the end part on the rear end side of the porcelain tube body 11 to the tip position of the conductive part 32 increases or decreases. 3, it can be seen that the rate of decrease in the lightning impulse withstand voltage can be suppressed to 10% or less when the distance from the end of the rear end of the porcelain tube body 11 to the tip position of the conductive part 32 is 10 to 27% of the effective insulation length of the porcelain tube body 11. It can also be seen that the rate of decrease in the lightning impulse withstand voltage can be suppressed to 5% or less, which is more preferable, when the distance from the end of the rear end of the porcelain tube body 11 to the tip position of the conductive part 32 is 11 to 18% or 20 to 24% of the effective insulation length of the porcelain tube body 11. Specifically, it can be seen that the rate of decrease in the lightning impulse withstand voltage can be suppressed to between 1 and 5% when the distance from the end of the rear end of the porcelain tube body 11 to the tip position of the conductive part 32 is 11 to 18% of the effective insulation length of the porcelain tube body 11, and the rate of decrease in the lightning impulse withstand voltage can be suppressed to between 0 and 5% when the distance is 20 to 24% of the effective insulation length of the porcelain tube body 11. In this embodiment, the lightning impulse withstand voltage performance is best and most preferable when the distance from the rear end of the insulator body 11 to the tip position of the conductive part 32 is about 21% of the effective insulation length of the insulator body 11. The position of the tip side of the shielding part 23 is appropriately set within the above range while maintaining the overlap with the conductive part 32 of the electric field mitigation part 30.

[0027] The fixing bracket 41 is a flange-shaped member having an opening equivalent to the large diameter portion 20C of the insulation unit 20. The fixing bracket 41 is disposed on the rear end side of the porcelain tube 10, and is fastened to the lower metal fitting 13 of the porcelain tube 10, for example, by bolting. In addition, a support insulator 45 is disposed on the rear end side of the fixing bracket 41, and is fastened, for example, by bolting.

[0028] The terminal mounting bracket 42 is a cylindrical member with a bottom having an inner diameter equal to the large diameter portion 20C of the insulation unit 20. An opening 42b for inserting the cable terminal portion 50 is provided in the bottom portion 42a of the terminal mounting bracket 42. The terminal mounting bracket 42 is disposed on the rear end side of the fixing bracket 41, and is fastened to the fixing bracket 41 and the insulation unit 20 by, for example, bolting.

[0029] The inner diameters of the fixing metal fitting 41 and the terminal mounting metal fitting 42 are formed to be approximately the same as the outer diameter of the large diameter portion 20C of the insulation unit 20, and a seal member 46 such as an O-ring is disposed between the fixing metal fitting 41 and the insulation unit 20. It is preferable that a plurality of seal members 46 are provided at predetermined intervals in the axial direction. This makes it possible to keep the inside of the porcelain tube 10 airtight or liquidtight to prevent leakage of the insulating medium 43, and also to reduce bending stress occurring in the porcelain tube 10.

[0030] The insulating medium 43 is filled in the space between the porcelain tube 10 and the insulating unit 20, and functions as the main insulating part of the cable termination connection part 1. The insulating medium 43 is formed of a liquid insulating medium such as silicone oil. Note that the insulating medium 43 only needs to have fluidity when injected into the porcelain tube 10, and may be an insulating material that hardens after injection, such as silicone gel or silicone rubber.

[0031] The insulating medium 43 is injected into the inside of the porcelain tube 10, for example, through a flow path 41a provided in the fixing bracket 41. In this case, it is preferable that a counterbore 41b is provided around the outlet of the flow path 41a in the fixing bracket 41. It is also preferable that the outer diameter of the insulating unit 20 in the vicinity of the outlet of the flow path 41a is sufficiently smaller than the inner diameter of the porcelain tube 10. This allows the insulating medium 43 to be injected into the inside of the porcelain tube 10 at a sufficient flow rate without impeding the flow of the insulating medium 43 injected through the flow path 41a.

[0032] The rear end of the conductor lead rod 44 is connected to the internal conductor 21 of the insulating unit 20, and the front end of the conductor lead rod 44 is drawn out through the upper metal fitting 12 of the porcelain tube 10. In other words, the internal conductor 21 is electrically connected to the conductor lead rod 44 that penetrates the upper metal fitting 12 and protrudes from the inside of the porcelain tube 10 to the outside. The conductor lead rod 44 is connected to the internal conductor 21 of the insulating unit 20, for example, via an appropriate conductor connecting member. The portion of the conductor lead rod 44 that is disposed inside the porcelain tube 10 may be a flexible conductor such as a cable. In this case, the front end side of the cable is connected to the rear end side of the conductor rod that is drawn out through the upper metal fitting 12, and the conductor lead rod 44 is formed by a plurality of members including the cable and the conductor rod that are disposed inside the porcelain tube 10. By configuring the portion of the conductor pull-out rod 44 that is placed inside the porcelain tube 10 with a cable, the bending stress generated in the porcelain tube 10 can be absorbed by the flexible cable, and excessive stress can be prevented from being generated in the internal insulation unit 20. In addition, by using a cable covered with an insulating coating, the electric field generated on the surface of the conductor pull-out rod 44 can be suppressed.

[0033] Here, "the internal conductor is electrically connected to the conductor lead-out rod that penetrates the upper fitting and protrudes from the inside to the outside of the porcelain tube" includes not only the case where the conductor lead-out rod 44 and the internal conductor 21 are formed of separate members as in this embodiment, but also the case where the conductor lead-out rod is formed of the same member by elongating the internal conductor. In other words, the internal conductor 21 may be formed to be elongated so that the internal conductor 21 is led out from the upper fitting 12. In this case, the internal conductor 21 and the conductor lead-out rod 44 are formed of the same member, and the conductor lead-out rod 44 as a separate member from the internal conductor 21 is not necessary, but the internal conductor also functions as a conductor lead-out rod.

[0034] The cable terminal portion 50 is configured by attaching connecting materials such as a conductor connecting terminal 52, a stress cone 53, and a compression device 54 to the tip portion of a power cable 51.

[0035] The power cable 51 is, for example, a 275 kV class extra-high voltage power cable insulated with rubber or plastic. The power cable 51 includes, in order from the center, a cable conductor 511, a cable insulator 512, a cable outer semiconductive layer 513, a cable shielding layer 514, and a cable sheath 515. At the cable terminal 50, each layer is exposed by step-stripping a predetermined length from the tip of the power cable 51.

[0036] A conductor connection terminal 52 is connected to the tip of the cable conductor 511 by compression. The conductor connection terminal 52 is made of a conductive material suitable for current flow, such as copper, aluminum, a copper alloy, or an aluminum alloy. A stress cone 53 is attached to the outer circumferential surface ranging from the cable insulator 512 to the tip of the cable outer semiconductive layer 513.

[0037] The stress cone 53 is formed in a spindle shape, and has an insulating portion (reference number omitted) at the tip end side and a conductive portion (reference number omitted) at the rear end side, similar to the electric field mitigation portion 30. The insulating portion is formed in a cylindrical shape from an insulating rubber material such as EP rubber, and the conductive portion is formed in a cylindrical shape from a semiconductive rubber material such as semiconductive EP rubber. The insulating portion and the conductive portion are integrally formed by molding.

[0038] The rear end (semiconductive portion) of the stress cone 53 is connected to the cable external semiconductive layer 513 of the power cable 51. "Connected to the cable external semiconductive layer 513 of the power cable 51" means either a direct connection to the cable external semiconductive layer 513 or a connection to the end of the cable external semiconductive layer 513 via an end of an external semiconductive layer reproduced with a mold or conductive paint, as long as the stress cone has a predetermined performance as a cable termination connection portion. The tip (insulating portion) of the stress cone 53 has a shape corresponding to the cable receiving portion 24 of the insulating unit 20. A compression device 54 and a protective metal fitting 55 are attached to the rear end side of the stress cone 53.

[0039] The compression device 54 has a pressing fitting (symbol omitted) that abuts against the stress cone 53, a coil spring (symbol omitted) that urges the pressing fitting toward the stress cone 53, and a pressing fitting flange (symbol omitted) that supports the pressing fitting and the coil spring.

[0040] After the tip of the power cable 51 is stripped in stages, the protective fitting 55, the compression device 54, and the stress cone 53 are inserted into the power cable 51, and the conductor connection terminal 52 is attached to the cable conductor 511. Then, the tip of the cable terminal portion 50 is inserted into the cable receiving portion 24 of the insulation unit 20, and while compressing the coil spring of the compression device 54, the pressing fitting flange is bolted to the bottom portion 42a of the terminal mounting fitting 42, and the protective fitting 55 is bolted to the pressing fitting flange, thereby mounting the cable terminal portion 50 to the cable receiving portion 24. The tip of the stress cone 53 is pressed against the inner surface of the insulating tube 22, and the conductor connection terminal 52 is electrically connected to the conductor insertion portion 21a of the inner conductor 21. In addition, a corrosion-resistant layer (reference number omitted) for waterproofing is disposed on the rear end of the protective metal fitting 55. In this manner, the cable termination connection portion 1 can be assembled with a relatively simple operation by plug-in connection.

[0041] In this manner, the cable termination connection portion 1 comprises: a porcelain tube 10 having a porcelain tube body 11 with a cap portion 11a formed on its outer peripheral surface, an upper metal fitting 12 arranged on the tip side of the porcelain tube body 11, and a lower metal fitting 13 arranged on the rear end side of the porcelain tube body 11; an insulating unit 20 arranged within the porcelain tube 10, the insulating unit 20 having a small diameter portion 20A formed in a straight barrel shape on the tip side, an inclined portion 20B expanding in diameter from the small diameter portion 20A toward the rear end side, and a large diameter portion 20C connected to the rear end side of the inclined portion 20B and having an outer diameter larger than that of the small diameter portion 20A; an electric field mitigation portion 30 attached to the outer peripheral surface of the small diameter portion 20A and made of an elastic body in which an insulating portion 31 and a conductive portion 32 connected to the rear end side of the insulating portion 31 are integrally formed; a fixing metal fitting 41 arranged on the rear end side of the porcelain tube 10; an insulating medium 43 sealed between the porcelain tube 10 and the insulating unit 20; and a cable terminal portion 50 connected to the rear end side of the large diameter portion 20C. The insulating unit 20 has an inner conductor 21 extending in the axial direction, a hard insulating tube 22 arranged on the outer circumferential surface of the inner conductor 21, and a shielding portion 23 formed on the outer circumferential surface of the insulating tube 22 so that its tip is connected to the conductive portion 32 of the electric field mitigation portion 30. The inner conductor 21 is electrically connected to a conductor lead rod 44 that penetrates the upper metal fitting 12 and protrudes from the inside to the outside of the porcelain tube 10. The shielding portion 23 is formed from the large diameter portion 20C to the intermediate position of the small diameter portion 20A of the insulating unit 20, and the large diameter portion 20C protrudes from the end portion on the rear end side of the porcelain tube 10.

[0042] According to the cable end connection part 1, the insulating medium 43 as the main insulating part and the insulating unit 20 as the reinforcing insulating part ensure the insulating performance at the cable end, and the porcelain pipe 10 can be lengthened without changing the size of the insulating unit 20, so that the quality of the insulating tube 22, which is a cast product, does not deteriorate with the lengthening of the porcelain pipe 10. In addition, since the insulating unit 20 is manufactured in a factory, the construction time at the site can be shortened. Furthermore, since the connection position between the cable terminal part 50 and the insulating unit 20 is provided at a position protruding from the end part on the rear end side of the porcelain pipe 10, even if the porcelain pipe 10 is lengthened, there is no need to increase the length of the terminal processing of the power cable 51. Therefore, the cable end connection part 1 can easily accommodate the extra-high voltage of the power cable 51, and is suitable as an air termination connection part for extra-high voltage power cables.

[0043] In the cable connection termination 1, the cable terminal portion 50 is attached by plug-in connection to the cable receiving portion 24 provided on the rear end side of the large diameter portion 20C. By configuring the cable terminal portion 50 to be connected to the insulating unit 20 by a plug-in connection, the insulating medium 43 can be pre-injected into the porcelain pipe 10 at the factory, and it is only necessary to adjust the amount of insulating medium 43 to a predetermined amount on-site. This eliminates the need to inject the insulating medium 43 from scratch on-site, significantly reducing the construction time on-site.

[0044] Moreover, in the cable termination 1, the electric field mitigating portion 30 is disposed at a position where the distance from the rear end of the porcelain tube body 11 to the tip position of the conductive portion 32 is 10 to 27% of the length (effective insulation length) of the porcelain tube body 11. Preferably, the electric field mitigating portion 30 is disposed at a position where the distance from the rear end of the porcelain tube body 11 to the tip position of the conductive portion 32 is 11 to 18% or 20 to 24% of the length of the porcelain tube body 11. As a result, when the length of the porcelain tube 10 is designed to satisfy the lightning impulse withstand voltage required for the cable termination connection portion 1, a significant decrease in the lightning impulse withstand voltage characteristics due to the tip position of the conductive portion 32 of the electric field mitigation portion 30 can be prevented, and the desired insulation performance can be ensured.

[0045] Furthermore, a seal member 46 is interposed between the fixing metal fitting 41 and the large diameter portion 20C in the cable connecting termination 1. Specifically, a plurality of seal members 46 are arranged along the axial direction. This makes it possible to keep the inside of the porcelain tube 10 airtight or liquidtight to prevent leakage of the insulating medium 43, and also to absorb bending stress occurring in the porcelain tube 10.

[0046] In the cable connection termination 1, at least a part of the conductor pull-out rod 44 that is disposed within the porcelain tube 10 is formed of a cable. This allows the flexible cable to absorb bending stress generated in the porcelain tube 10, preventing excessive stress from being generated in the internal insulation unit 20. In addition, by using a cable covered with an insulating coating, the electric field generated on the surface of the conductor lead rod 44 can be suppressed.

[0047] Moreover, in the cable termination 1, the fixing metal fitting 41 has a flow path 41a through which the insulating medium 43 can be injected into the porcelain tube 10. Specifically, the flow path 41a has an outlet communicating with the inside of the porcelain tube 10 at a position corresponding to the inclined portion 20B of the insulating unit 20, and in this embodiment, is provided so as to be located near the rear end side of the inclined portion 20B, in other words, near the transition portion from the large diameter portion 20C toward the small diameter portion 20A. This allows the insulating medium 43 to be injected into the porcelain pipe 10 via the flow path 41a, and also allows the insulating medium 43 to be injected in advance at a factory and then an appropriate amount to be removed at the construction site to set the desired amount. If the flow path 41a is not provided in the fixing bracket 41, the insulating medium 43 is injected from the top of the porcelain pipe 10, which requires a member to ensure a foothold for high-altitude work at the construction site, causing problems in terms of construction and safety. By providing the flow path 41a in the fixing bracket 41, the insulating medium 43 can be set to an appropriate amount at the construction site with the cable termination connection part 1 installed easily and safely.

[0048] In addition, in the cable connecting end 1, a counterbore 41b is formed around the outlet of the fixing metal fitting 41. This allows the insulating medium 43 to be injected into the porcelain tube 10 at a sufficient flow rate without impeding the flow of the insulating medium 43 injected through the flow passage 41a.

[0049] The invention made by the inventor has been specifically described above based on an embodiment, but the present invention is not limited to the above embodiment and can be modified within the scope of the gist of the invention.

[0050] For example, in the present embodiment, the insulating medium 43 is a liquid insulating medium, but it may be an insulating gas, with the same effects as described above being obtained. In addition, in this embodiment, the case where the cable terminal is plugged in and connected using an inner cone type having a stress cone and a compression device, etc., has been described, but the cable terminal and the insulation unit may be connected using an outer cone type in which they are connected using a rubber block. In this case, the large diameter portion 20C is formed at a position corresponding to the fixing metal fitting 41 of the insulation unit 20 as in this embodiment, but a rubber block is connected to the rear end side of the insulation tube. Therefore, the rear end of the insulation tube is not a cable receiving port as in the inner cone type, but has a shape in which the insulation tube protrudes and the internal conductor protrudes from the rear end of the insulation tube.

[0051] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0052] 1 Cable termination connection 10 Pipe 11. Porcelain tube body 12 Upper bracket 13 Lower bracket 20 Isolation Unit 20A Small diameter section 20B Slope 20C Large diameter section 21 Inner conductor 22 Insulating tube 23 Shielding section 24 Cable Receptacle 30 Electric field mitigation section 31 Insulation section 32 Conductive part 41 Fixing bracket 42 Terminal mounting bracket 43 Insulating Media 44 Conductor pull rod 50 Cable terminal

Claims

1. a porcelain tube having a porcelain tube body having a cap portion formed on an outer peripheral surface thereof, an upper metal fitting disposed on a front end side of the porcelain tube body, and a lower metal fitting disposed on a rear end side of the porcelain tube body; an insulating unit disposed within the porcelain tube, the insulating unit having a small diameter portion formed in a straight barrel shape at a front end side, an inclined portion expanding in diameter from the small diameter portion toward a rear end side, and a large diameter portion connected to the rear end side of the inclined portion and having an outer diameter larger than that of the small diameter portion; an electric field mitigation portion made of an elastic body attached to an outer circumferential surface of the small diameter portion and integrally formed with an insulating portion and a conductive portion connected to a rear end side of the insulating portion; A fixing metal fitting disposed on a rear end side of the porcelain tube; an insulating medium sealed between the porcelain bushing and the insulating unit; a cable terminal portion connected to a rear end side of the large diameter portion, the insulating unit includes an inner conductor extending in an axial direction, a hard insulating tube disposed on an outer circumferential surface of the inner conductor, and a shielding portion formed on an outer circumferential surface of the insulating tube such that a tip of the shielding portion is connected to the conductive portion of the electric field mitigation portion, the inner conductor is electrically connected to a conductor lead rod that penetrates the upper metal fitting and protrudes from the inside to the outside of the porcelain tube, the shielding portion is formed across an intermediate position between the large diameter portion and the small diameter portion of the insulating unit, The large diameter portion protrudes from an end portion on a rear end side of the porcelain tube. Cable termination connection.

2. The cable terminal portion is attached to a cable receiving portion provided on a rear end side of the large diameter portion by plug-in connection.

2. A cable termination according to claim 1.

3. A seal member is interposed between the fixing metal fitting and the large diameter portion.

3. A cable termination according to claim 1 or 2.

4. The electric field mitigation portion is disposed at a position where a distance from an end portion on a rear end side of the porcelain tube body to a tip position of the conductive portion is 10 to 27% of a length of the porcelain tube body. A cable termination according to any one of claims 1 to 3.

5. the electric field mitigation portion is disposed at a position where a distance from an end portion on the rear end side of the porcelain tube body to a tip position of the conductive portion is 11 to 18% or 20 to 24% of a length of the porcelain tube body.

5. A cable termination according to claim 4.

6. At least a part of the conductor lead rod disposed in the porcelain tube is formed of a cable. A cable termination according to any one of the preceding claims.

7. The fixing metal fitting has a flow path inside the porcelain tube into which the insulating medium can be injected. A cable termination according to any one of the preceding claims.

8. The flow path is provided such that an outlet port to the inside of the porcelain tube is located on an outer periphery of the inclined portion.

8. A cable termination according to claim 7.

9. A countersink is formed around the outlet of the fixing metal fitting.

9. A cable termination according to claim 8.

10. The insulating unit is formed in an R-shape at the inclined portion so as to be gradually tapered from the large diameter portion toward the small diameter portion. A cable termination according to any one of the preceding claims.

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