Insulating tubes, cable terminations and equipment bushings

Abstract

To provide a porcelain tube, a cable end connection and an apparatus bushing with high safety which can prevent a porcelain tube body from being damaged by sharp rise of inner pressure associated with evaporation of an insulation medium due to a ground fault, etc.SOLUTION: A porcelain tube comprises: a porcelain tube body with a shade part formed on an outer peripheral surface; an upper seal part which is arranged on the tip side of the porcelain tube body to seal the porcelain tube body; an upper metal fitting which covers the upper seal part; an insulation unit which is arranged in the porcelain tube body; and an insulation medium which is encapsulated between the porcelain tube body and the insulation unit. The upper seal part comprises: an upper flange which comprises a flange opening and is fluid-tightly attached to the porcelain tube body; a rapture plate with rapture pressure lower than that of the porcelain tube body, which is arranged to block the flange opening; and a pressure ring which comprises a ring opening and presses the rapture plate to fix the rapture plate to the upper flange.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a hollow insulator having an insulating medium sealed within its body, a cable terminal connection part, and a bushing for equipment. [Background technology]

[0002] 2. Description of the Related Art Conventionally, air terminal connections that provide air insulation using an insulating tube have been known as cable terminal connections provided at the end of a power cable (see, for example, Patent Documents 1 to 3).

[0003] In the cable termination disclosed in Patent Document 1, a conductor lead rod exposed at the tip of the hollow insulator is compressed and connected to the end of the cable conductor of the power cable. A stress cone (also called a premolded 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 hollow insulator. An air termination having 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 hollow insulator.

[0004] In the cable terminations disclosed in Patent Documents 2 and 3, the conductor pull-out rod exposed at the tip of the hollow insulator 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 does not have a compression device for pressing the epoxy seat and stress cone in the hollow insulator 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 hollow insulator to relax the electric field, and is called a rubber block type. The hollow insulator used in the rubber block type air termination may be either a ceramic hollow insulator (see Patent Document 3) or a polymer hollow insulator (also called a composite hollow insulator, see Patent Document 2), and generally, an insulating medium such as insulating oil (e.g., silicone oil) is filled in the hollow insulator. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2000-261948 A [Patent Document 2] Patent No. 5804948 [Patent Document 3] Patent No. 4685908 [Patent Document 4] Patent No. 5606252 [Non-patent literature]

[0006] [Non-Patent Document 1] Showa Electric Wire Review, "Development and Practical Application of 66 / 77kV Direct Molded Through Bushings", Vol. 56, No. 1 (2006) pp. 15-19 Summary of the Invention [Problem to be solved by the invention]

[0007] In a cable termination connection part where an insulating medium is enclosed in a hollow insulator, the insulating medium evaporates in the event of a ground fault, causing a sudden rise in internal pressure, and in some cases, the hollow insulator body may be damaged and the insulating medium may leak. In particular, in a cable termination connection part of an extra-high voltage power cable (e.g., 275 kV class), the risk of a ground fault is higher than in a cable termination connection part of a low voltage power cable, so measures must be taken to prevent damage to the hollow insulator body due to a sudden rise in internal pressure.

[0008] An object of the present invention is to provide a highly safe hollow insulator, a cable termination connection part, and an equipment bushing that can prevent the hollow insulator body from being damaged due to a sudden increase in internal pressure of the hollow insulator accompanying evaporation of an insulating medium due to a ground fault or the like. [Means for solving the problem]

[0009] The hollow insulator according to the present invention comprises: an insulator body having a cap portion formed on an outer circumferential surface; an upper sealing portion that is disposed on a tip side of the hollow insulator body and seals the hollow insulator body; An upper fitting covering the upper sealing portion; an insulating unit disposed in the insulator body; The hollow insulator body and The above an insulating medium sealed between the insulating unit and the insulating medium; The upper sealing portion is an upper flange having a flange opening and attached to the hollow insulator body in a liquid-tight manner; a rupture disk having a lower burst pressure than the hollow insulator body and disposed so as to close the flange opening; a pressing ring having a ring opening and pressing the rupture disc to fix it to the upper flange; death, The retaining ring has a drain groove on the surface that comes into contact with the rupture disc.

[0010] The cable termination according to the present invention comprises: A cable termination including the above-mentioned hollow insulator, The insulating unit includes at least an inner conductor and an insulating tube that is integrally provided on an outer periphery of the inner conductor, A cable terminal portion of a cable to be connected to the insulator pipe is connected to a rear end side of the insulating unit, The rear end side of the inner conductor and the cable conductor of the cable are electrically connected.

[0011] The bushing for an equipment according to the present invention comprises: A through bushing for equipment comprising the above hollow insulator, The insulating unit includes at least an inner conductor and an insulating tube that is integrally provided on an outer periphery of the inner conductor, a head portion disposed in the device and having a shape tapering toward the rear end side of the insulating unit; The internal conductor has a structure that penetrates and protrudes from the head portion. Effect of the Invention

[0012] According to the present invention, it is possible to prevent the hollow insulator body from being damaged due to a sudden increase in internal pressure accompanying evaporation of the insulating medium due to a ground fault or the like, thereby improving safety. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view showing a cable connection portion according to an embodiment of the present invention. [Diagram 2] 2A and 2B are enlarged views of the periphery of the upper sealing portion of the cable termination connection portion. [Diagram 3] FIG. 3 is an exploded perspective view of the top closure. [Figure 4] FIG. 4 is an enlarged cross-sectional view of the portion enclosed by the dashed line in FIG. 2A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0015] FIG. 1 is a cross-sectional view showing a cable connection termination 1 according to an embodiment of the present invention.

[0016] 1, the cable termination 1 includes an insulator 10, a fixing bracket 41, a terminal mounting bracket 42, a conductor pull-out rod 44, and a cable terminal 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 50 is attached is referred to as the "rear end side."

[0017] The hollow insulator 10 has a hollow insulator body 11 having a cap portion 11a (see FIG. 2A) formed on its outer peripheral surface, an upper metal fitting 12 arranged on the tip side of the hollow insulator body 11, an insulating unit 20, an electric field mitigation portion 30, and an insulating medium 43.

[0018] The hollow insulator body 11 may be, for example, a porcelain hollow insulator, or a polymer hollow insulator (also called a composite hollow insulator) 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 hollow insulator 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.

[0019] Furthermore, in this embodiment, an upper sealing portion 60 (see FIG. 2A) is provided on the tip side of the hollow insulator body 11. The upper sealing portion 60 is covered by the upper metal fitting 12. The structure of the upper sealing portion 60 will be described later.

[0020] The insulating unit 20 has an inner conductor 21 extending in the axial direction, an 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, 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 circumferential surface of the insulating tube 22.

[0021] The insulating unit 20 is divided into a small diameter section 20A formed in a straight barrel shape on the front end side, an inclined section 20B expanding in diameter from the small diameter section 20A toward the rear end side, and a large diameter section 20C formed in a straight barrel shape connected to the rear end side of the inclined section 20B. The large diameter section 20C has an outer diameter larger than that of the small diameter section 20A.

[0022] The insulating unit 20 is arranged so that the small diameter portion 20A is inside the hollow insulator body 11 and the large diameter portion 20C is outside the hollow insulator body 11. 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 hollow insulator body 11. In this embodiment, the tip side of the small diameter portion 20A has a shape that decreases in diameter toward the tip side. This makes it easier to insert the electric field mitigation portion 30, which is formed of a cylindrical elastic body described later, into the insulating unit 20.

[0023] 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.

[0024] 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.

[0025] 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 hollow insulator body 11, but may be larger than the inner diameter of the hollow insulator body 11. From the viewpoint of electric field design, it is advantageous for the large diameter portion 20C of the insulating unit 20 in which 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 hollow insulator body 11, it can be designed to have an outer diameter appropriate for electric field design without being limited by the inner diameter of the hollow insulator body 11.

[0026] 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.

[0027] The shielding portion 23 is formed on the outer circumferential 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 midway in 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.

[0028] 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.

[0029] 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.

[0030] The fixing metal fitting 41 is a flange-shaped member having an opening equivalent to the large diameter portion 20C of the insulating unit 20. The fixing metal fitting 41 is disposed on the rear end side of the hollow insulator body 11, and is fastened, for example, by bolting, to the lower metal fitting 13 that is integrally provided on the rear end of the hollow insulator body 11. In addition, a support insulator 45 is disposed on the rear end side of the fixing metal fitting 41, and is fastened, for example, by bolting.

[0031] 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.

[0032] 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 insulating unit 20, and a seal member 46 such as an O-ring is disposed between the fixing metal fitting 41 and the insulating 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 hollow insulator body 11 airtight or liquidtight to prevent the insulating medium 43 from leaking, and also to relieve bending stress occurring in the hollow insulator body 11.

[0033] The insulating medium 43 is filled in the space between the hollow insulator body 11 and the insulating unit 20, and functions as the main insulating part of the cable termination connection part 1. The insulating medium 43 is made of an insulating oil such as silicone oil. Note that the insulating medium 43 only needs to have fluidity when injected into the inside of the hollow insulator 10 (inside the hollow insulator body 11), and may be an insulating material that hardens after injection, such as silicone gel or silicone rubber. However, when the insulating medium 43 is an insulating oil, the problem of a sudden rise in internal pressure due to evaporation becomes prominent.

[0034] The insulating medium 43 is injected into the hollow insulator 10 (inside the hollow insulator body 11) through, for example, a flow path (not shown) provided in the fixing metal fitting 41. The insulating medium 43 evaporates with an increase in ambient temperature due to a ground fault or the like. In the hollow insulator 10, the gap between the conductor lead rod 44 penetrating the upper flange 61 and the upper flange 61 is sealed by a sealing member such as an O-ring, and further, the hollow insulator body 11 is sealed by the upper sealing portion 60, so that the evaporation of the insulating medium 43 causes a sudden increase in internal pressure. The upper sealing portion 60 is provided with measures to prevent damage to the hollow insulator body 11 due to an increase in internal pressure.

[0035] 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 hollow insulator 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 hollow insulator 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 in the hollow insulator body 11 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 penetrates the upper metal fitting 12 and is drawn out to the outside, and the conductor lead rod 44 is formed by a plurality of members including the cable and the conductor rod that are disposed in the hollow insulator body 11. By configuring the portion of the conductor pull-out rod 44 that is placed inside the hollow insulator body 11 with a cable, the bending stress generated in the hollow insulator body 11 can be absorbed by the flexible cable, and excessive stress can be prevented from being generated in the internal insulating 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.

[0036] 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 hollow insulator" 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 2A and 2B are enlarged views of the periphery of the upper sealing portion 60 in the cable termination connection portion 1. Fig. 3 is an exploded perspective view of the upper sealing portion 60. Fig. 4 is an enlarged cross-sectional view of the portion surrounded by the dashed line in Fig. 2A. Fig. 2A is a cross-sectional view of the upper sealing portion 60 taken along line AA in Fig. 2B. Fig. 2B is a plan view of the upper sealing portion 60 seen from the tip side without the upper fitting 12, and is shown diagrammatically with detailed structure appropriately omitted.

[0046] 2A etc., the upper sealing part 60 has an upper flange 61, a rupture disc 62, and a retaining ring 63. The upper flange 61, the rupture disc 62, and the retaining ring 63 are arranged such that a flange opening 611 of the upper flange 61, a recess 623 of the rupture disc 62, and a ring opening 631 of the retaining ring 63 are concentric.

[0047] The upper flange 61 is attached liquid-tightly to the tip side of the hollow insulator body 11 via a seal member 64 such as an O-ring. The upper flange 61 has a draw-out port 612 through which the conductor draw-out rod 44 is inserted in the center. A plurality of flange openings 611 having a circular cross section are formed in the upper flange 61 so as to surround the draw-out port 612 (see FIG. 4). For example, as shown in FIG. 2B, four flange openings 611 are provided around the draw-out port 612 through which the conductor draw-out rod 44 passes, at positions that are rotationally symmetric by 90° about the center of the upper flange 61 (which is also the center of the draw-out port 612). The number of flange openings 611 is not particularly limited, but it is preferable that they are provided evenly at positions that are rotationally symmetric about the center of the upper flange 61 (which is also the center of the draw-out port 612). Note that a first slit 621 and a second slit 622, which will be described later, are formed on the tip surface of the rupture disc 62 after it is attached to the four flange openings 611, respectively. 622 It is not necessary for the orientation of the upper flange 61 to be rotationally symmetrical about the center of the upper flange 61.

[0048] The rupture disc 62 is a plate member having a strength sufficient not to break under pressure during normal operation (e.g., 0.3 MPa). The rupture disc 62 is made of, for example, stainless steel, copper, aluminum, or an alloy thereof. From the viewpoint of corrosion resistance, the rupture disc 62 is preferably made of a stainless steel material.

[0049] The rupture disc 62 is disposed on the first step 613 so as to close the flange opening 611 of the upper flange 61 via a seal member 65 such as an O-ring. In this embodiment, the first step 613 is formed by a recess provided on the tip surface of the upper flange 61. The outer diameter of the recess formed by the first step 613 is set to the inner diameter of the seal receiving groove 612 as described later. 615 and is larger than the outer diameter of the rupture disc 62. In order to prevent the position of the rupture disc 62 from shifting when pressed by a press ring 63 described later, the difference between the outer diameter of the first step 613 and the outer diameter of the rupture disc 62 is preferably 3 mm or less.

[0050] The seal member 65 is accommodated in a ring-shaped seal accommodating groove 615 provided on the tip surface of the upper flange 61, specifically, in this embodiment, on the rear end surface (bottom surface) of the recess of the first step portion 613. The seal accommodating groove 615 is formed concentrically with the flange opening 611, and the outer diameter φC of the center thereof is larger than the outer diameter φB of the flange opening 611.

[0051] In addition, the rupture disc 62 is formed so as to have a lower rupture pressure than the hollow insulator body 11. When the internal pressure of the hollow insulator body 11 rises, the rupture disc 62 ruptures before the hollow insulator body 11 does, and therefore the evaporated insulating medium 43 can be discharged to the outside, thereby preventing the destruction of the hollow insulator body 11.

[0052] Specifically, the rupture disc 62 has a plurality of first slits 621 extending radially in the central portion 62a. In this embodiment, four first slits 621 are formed in the tip surface of the rupture disc 62 so as to extend in all directions from the center point of the rupture disc 62. The first slits 621 are grooves that do not penetrate the rupture disc 62. For example, the grooves of the first slits 621 are formed to have a V-shaped cross section (not shown). When the internal pressure of the hollow insulator body 11 increases and exceeds the rupture pressure of the rupture disc 62, the first slits 621 are ruptured and the central portion 62a of the rupture disc 62 is rolled up toward the tip side, and an outlet for the evaporated insulating medium 43 is formed at the rolled up location. The rupture pressure of the rupture disc 62 can be adjusted by the number, slit width, and slit depth of the first slits 621.

[0053] The first slits 621 are formed extending radially, and the tip portions on the opposite side from the center point are spaced apart from each other, so even if the first slits 621 break due to an increase in internal pressure and the central portion 62a is rolled up, it will not easily separate from the peripheral portion 62b. Even if the central portion 62a is rolled up and separated from the peripheral portion 62b, the separated pieces will not fly out because it is covered by the upper metal fitting 12, and safety is ensured.

[0054] In addition, the rupture disc 62 has a second slit 622, which is a non-penetrating groove, between the tips of the adjacent first slits 621. For example, the groove of the second slit 622 is formed to have a V-shaped cross section (not shown). The second slit 622 has a structure that assists the deformation of the rupture disc 62 by becoming a fold when the first slit 621 is ruptured, and is formed, for example, so as to connect the parts near the tips of the adjacent first slits 621 and not to communicate with the groove of the first slit 621. By providing the second slit 622, the deformation (rolling up) of the center part 62a after the first slit 621 is ruptured is promoted, and a discharge port for the insulating medium 43 is easily formed.

[0055] In the rupture disc 62, the thickness of the peripheral portion 62b that comes into contact with the upper flange 61 is greater than the thickness of the central portion 62a that covers the flange opening 611 of the upper flange 61. In this embodiment, a recess 623 having an outer diameter φA and a circular cross section is provided on the surface of the rear end side of the central portion 62a, so that the central portion 62a (the portion of φA corresponding to the recess 623) is made thinner than the peripheral portion 62b. For example, the thickness of the central portion 62a is 1 to 1.5 mm, whereas the thickness of the peripheral portion 62b is 3 to 5 mm.

[0056] Also, the inner peripheral edge of the peripheral portion 62b of the rupture disc 62 protrudes inward from the peripheral edge of the flange opening 611 of the upper flange 61. That is, in the example of Fig. 4, the outer diameter φB of the flange opening 611 of the upper flange 61 is larger than the outer diameter φA of the recess 623 of the rupture disc 62. φA and φB may be formed to be the same dimension. Since the peripheral portion 62b is formed to be thick and further, the inner peripheral edge of the peripheral portion 62b protrudes inward from the peripheral edge of the flange opening 611 of the upper flange 61, the rupture disc 62 does not easily deform or float up from the upper flange 61 even when subjected to pressure during normal operation.

[0057] The retaining ring 63 has a ring opening 631 having a circular cross section corresponding to the center of the rupture disc 62. In the example of Fig. 4, the outer diameter φD of the ring opening 631 of the retaining ring 63 is larger than the outer diameter φB of the flange opening 611 of the upper flange 61 and is smaller than the outer diameter φC of the center of the seal accommodating groove 615.

[0058] The retaining ring 63 is disposed on the tip side of the rupture disc 62 and is fastened to the upper flange 61 by, for example, bolts V, thereby retaining and fixing the peripheral edge portion 62b of the rupture disc 62. The retaining ring 63 is formed of, for example, a metal material such as brass.

[0059] The outer diameter of the retaining ring 63 is larger than the outer diameter of the rupture disc 62 and larger than the outer diameter of the first step 613. In this embodiment, the screw holes into which the bolts V are screwed are located on the outer side of the first step 613 in the upper flange 61. A second step 614 is provided at a position on the tip side of the upper flange 61 facing the rear end face of the retaining ring 63.

[0060] In the embodiment, the second step 614 is formed by a recess provided in the tip surface of the upper flange 61. A first recess 613 is further formed on the center side of the recess formed by the second step 614. In other words, in the upper flange 61, the thickness between the rear end surface (bottom surface) of the recess formed by the second step 614 and the rear end surface of the upper flange 61 is greater than the thickness between the rear end surface (bottom surface) of the recess formed by the first step 613 and the rear end surface of the upper flange 61.

[0061] Moreover, the outer diameter of the second step 614 is larger than the outer diameter of the pressing ring 63. This allows the pressing ring 63 to reliably fix the rupture disc 62 to the upper flange 61 in an air-tight or liquid-tight manner.

[0062] The retaining ring 63 has drain grooves 632 that connect from ring openings 631 to the outer periphery on the contact surface with the rupture disc 62. In the example of Fig. 3, three drain grooves are provided on the circumference so as to extend radially from the center of the rupture disc 62. Water that has entered the inside of the upper fitting 12 is discharged through the drain grooves 632 and does not accumulate on the contact surface between the rupture disc 62 and the retaining ring 63.

[0063] The outer diameter φB of the flange opening 611 of the upper flange 61 is formed to be equal to or larger than the outer diameter φA of the recess 623 of the rupture disc 62, and the outer diameter φD of the ring opening 631 of the pressing ring 63 (the inner diameter of the pressing ring 63) is formed to be larger than the outer diameter φA of the recess 623 of the rupture disc 62 and smaller than the outer diameter φC of the center of the seal accommodating groove 615 in the upper flange 65. That is, there is a relationship of φB≧φA and φA<φD<φC. This makes it possible to stably maintain the airtight or liquidtight performance of the upper sealed portion 60 of the hollow insulator 10 during normal operation.

[0064] As described above, the hollow insulator 10 applied to the cable connecting terminal 1 according to the present embodiment has the following characteristics either alone or in appropriate combination.

[0065] That is, the hollow insulator 10 includes a hollow insulator body 11 having a cap portion 11a formed on its outer circumferential surface, an upper sealing portion 60 arranged on the tip side of the hollow insulator body 11 and sealing the hollow insulator body 11, an upper metal fitting 12 covering the upper sealing portion 60, an insulating unit 20 arranged in the hollow insulator body 11, and an insulating medium 43 sealed between the hollow insulator body 11 and the insulating unit 20. The upper sealing portion 60 includes an upper flange 61 having a flange opening 611 and attached liquid-tightly to the hollow insulator body 11, a rupture disk 62 having a lower burst pressure than the hollow insulator body 11 and arranged so as to close the flange opening 611, and a retaining ring 63 having a ring opening 631 and retaining the rupture disk 62 to fix it to the upper flange 61.

[0066] According to the hollow insulator 10, when the insulating medium 43 evaporates due to a ground fault or the like and the internal pressure rises suddenly, the rupture plate 62 ruptures before the hollow insulator body 11 does, forming an outlet for the evaporated insulating medium 43. Therefore, it is possible to prevent the hollow insulator 10 (hollow insulator body 11) from being damaged by a sudden rise in internal pressure accompanying evaporation of the insulating medium 43 due to a ground fault or the like, and the safety of the cable termination 1 to which the hollow insulator 10 is applied is improved.

[0067] In addition, the upper sealing portion 60 has an extremely simple structure and is smaller and lower in height than typical safety devices that release excess pressure when it occurs, such as rupture disks, safety valves, or explosion vents, so that the upper sealing portion 60 can be installed without increasing the internal space of the upper fitting 12.

[0068] In addition, in the hollow insulator 10, the thickness of the peripheral edge portion 62b of the rupture disc 62 that comes into contact with the upper flange 61 is greater than the thickness of the central portion 62a that covers the flange opening 611. This makes it possible to prevent the rupture disc 62 from floating up due to pressure during normal operation, thereby preventing the sealed state of the hollow insulator 10 from being lost.

[0069] In addition, in the hollow insulator 10, the flange opening 611 and the ring opening 631 have a circular cross section, the upper flange 61 has a seal accommodating groove 615 formed concentrically with the flange opening 611, the rupture disc 62 has a recess 623 formed in a rear end face and having a circular cross section, and the upper flange 61, the rupture disc 62, and the holding ring 63 are arranged so that the flange opening 611, the recess 623, and the ring opening 631 are concentric. When the outer diameter of the recess 623 is φA, the outer diameter of the flange opening 611 is φB, the outer diameter of the center of the seal accommodating groove 615 is φC, and the outer diameter of the ring opening 631 is φD, the relationship is φB≧φA and φA<φD<φC. This makes it possible to stably maintain the airtight or liquidtight performance of the upper sealed portion 60 of the hollow insulator 10 during normal operation.

[0070] In addition, in the hollow insulator 10, the rupture disc 62 has a plurality of first slits 621 extending radially and not penetrating at the tip end surface. This makes it possible to easily form a discharge port for the evaporated insulating medium 43 by rupturing the rupture disc 62 in an intended manner.

[0071] In the hollow insulator 10, the rupture disc 62 has second slits 622 on the tip surface, which are provided between the tip ends of the adjacent first slits 621 and are formed as non-penetrating grooves so as not to communicate with the first slits 621. This promotes deformation of the central portion 62a of the rupture disc 62, and makes it possible to easily form a release port for the insulating medium 43.

[0072] In addition, in the hollow insulator 10, the retaining ring 63 has a drain groove 632 on the surface that comes into contact with the rupture disc 62. Water that has infiltrated into the interior of the upper fitting 12 is drained through the drain groove 632, thereby making it possible to suppress corrosion of the rupture disc 62.

[0073] 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.

[0074] For example, in the present embodiment, the case where the cable terminal is plugged in 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 the present 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.

[0075] Furthermore, for example, it is sufficient that the rupture plate 62 has a lower rupture pressure than the hollow insulator body 11, and the configuration for achieving this is not limited to the first slits 621 and the like described in the embodiment.

[0076] In the above embodiment, the hollow insulator according to the present invention is applied to a cable termination connection portion, but the present invention is not limited to this, and may be applied to an air portion of an equipment bushing (also called an "equipment penetration bushing"). The equipment side of the equipment bushing has a known shape compatible with oil insulation and / or gas insulation, and can be used for transformers or GIS (gas insulated switchgear).

[0077] When applied to an equipment bushing, the rear end side of the insulating tube of the insulating unit arranged in the hollow insulator body 11 has a head portion that can withstand oil insulation and / or gas insulation in the equipment, rather than a cable receiving port structure like the receiving portion 24. The head portion is formed in a known shape including a portion that tapers in diameter from the front end side to the rear end side (in other words, tapers in diameter toward the inside of the equipment to which it is attached) (for example, see the equipment side shape of the through bushing in Figure 1 of Non-Patent Document 1 and the structure below the flange portion in Figure 1 of Patent Document 4).

[0078] That is, when the hollow insulator of the present invention is applied to an equipment bushing, the rear end of the inner conductor does not have a conductor insertion portion for connecting a cable conductor, and the rod-shaped inner conductor penetrates and protrudes from the head portion at the rear end of the insulating tube. The protruding rear end of the inner conductor may remain rod-shaped or may have a shield shape to prevent partial discharge. Also, a shielding metal fitting may be provided as appropriate to relieve the electric field at the head portion.

[0079] 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]

[0080] 1 Cable termination connection 10 Insulator 11 Insulator body 12 Upper bracket 20 Isolation Unit 43 Insulating Media 60 Upper sealing part 61 Upper flange 62 Rupture disc 63 Retaining ring 611 Flange opening 621 First Slit 622 Second Slit 623 Recess 631 Ring Opening

Claims

1. an insulator body having a cap portion formed on an outer circumferential surface; an upper sealing portion that is disposed on a tip side of the hollow insulator body and seals the hollow insulator body; An upper fitting covering the upper sealing portion; an insulating unit disposed in the insulator body; an insulating medium sealed between the hollow insulator body and the insulating unit, The upper sealing portion is an upper flange having a flange opening and attached to the hollow insulator body in a liquid-tight manner; a rupture disk having a lower burst pressure than the hollow insulator body and disposed so as to close the flange opening; a pressing ring having a ring opening and pressing the rupture disc to fix it to the upper flange; The retaining ring has a drain groove on a surface that contacts the rupture disc. Insulator pipe.

2. The rupture disc has a plurality of first slits formed by non-penetrating radially extending grooves on a tip surface. The hollow insulator according to claim 1 .

3. The rupture plate has a second slit on its tip surface, the second slit being provided between the tip ends of the adjacent first slits and formed so as not to communicate with the groove of the first slit by a non-penetrating groove. The hollow insulator according to claim 2 .

4. a thickness of a peripheral portion of the rupture disc that abuts against the upper flange is greater than a thickness of a central portion that covers the flange opening; The hollow insulator according to claim 1 .

5. the flange opening and the ring opening have a circular cross-sectional shape; The upper flange has a seal receiving groove formed concentrically with the flange opening, The rupture disc has a recess having a circular cross section formed on a rear end surface, the upper flange, the rupture disc, and the retaining ring are arranged so that the flange opening, the recess, and the ring opening are concentric, When the outer diameter of the recess is φA, the outer diameter of the flange opening is φB, the outer diameter of the center of the seal accommodating groove is φC, and the outer diameter of the ring opening is φD, The relationship is φB≧φA and φA<φD<φC. The hollow insulator according to claim 4.

6. A cable termination including the hollow insulator according to claim 1, The insulating unit includes at least an inner conductor and an insulating tube that is integrally provided on an outer periphery of the inner conductor, A cable terminal portion of a cable to be connected to the insulator pipe is connected to a rear end side of the insulating unit, a rear end side of the inner conductor and a cable conductor of the cable are electrically connected to each other; Cable termination connection.

7. A through bushing for equipment comprising the hollow insulator according to claim 1, The insulating unit includes at least an inner conductor and an insulating tube that is integrally provided on an outer periphery of the inner conductor, a head portion disposed in the device and having a shape tapering toward the rear end side of the insulating unit; The internal conductor has a structure penetrating and protruding from the head portion. Equipment bushings.

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