Terminal connection part for power cable

Abstract

In order to provide a terminal connection part which is for a power cable and which is capable of preventing a seal pipe provided around the power cable disposed in a vertical-type porcelain tube from being detached from the lower end of the porcelain tube, a terminal connection part 1 for a power cable comprises: a porcelain tube 3 through which a power cable 2 is inserted; a stress cone 5 attached to the power cable 2; a lower flange 6 that closes the lower end of the porcelain tube 3 and that has a through-hole 62 for passing the power cable 2 therethrough; a seal pipe 7 that surrounds an external semiconductor layer 23 of the power cable 2, that has an upper end sealed and fixed to the external semiconductor layer 23, and that is capable of moving upward or downward with respect to the lower flange 6 by following extension / contraction upward or downward of the power cable 2 while forming a sealed state between the outer circumferential surface of the lower end and the inner circumferential surface of the through-hole 62; a lower protection portion 8 that surrounds the power cable 2 and that is fixed to the lower side of the lower flange 6; and an anti-corrosion structure 9 that fixes the lower end of the lower protection portion 8 to the power cable 2. The seal pipe 7 and the lower protection portion 8 are separated from each other.

Description

Power cable termination

[0001] The present invention relates to a termination for a power cable.

[0002] A conventional power cable termination (hereinafter sometimes simply referred to as a termination) is one in which a power cable is placed in a vertically-positioned porcelain bushing, with the conductor, insulating layer, and other layers exposed, and a stress cone is attached to the outer semiconducting layer, etc. In such a termination, the internal space of the porcelain bushing is usually filled with an insulating fluid such as insulating oil.

[0003] In such a termination, when the current value of the power cable increases, the power cable elongates relatively significantly, particularly downward, due to heat generation in the conductor, which can cause large stresses to be applied to the stress cone and the insulating fluid seal. This stress can cause deformation or damage to the stress cone, and deformation of the insulating fluid seal can cause the insulating fluid inside the porcelain insulator tube to leak out.

[0004] 6, a conventional termination 100 is known in which a cylindrical seal pipe 102 is disposed around a metal shielding layer 24 below a stress cone (not shown) of a power cable 2 that is stripped and disposed in a porcelain tube 101 (see, for example, Patent Document 1). In this case, the upper end of the seal pipe 102 is fixed to the metal shielding layer 24 by an upper end fixing portion 103 or the like, and the lower end of the seal pipe 102 is fixed to the metal shielding layer 24 and the sheath layer 25 by a lower end fixing portion 104 or the like.

[0005] A through hole 105a is provided in the bottom plate portion 105 of the porcelain tube 101. A groove is formed in the inner peripheral surface of the through hole 105a in the circumferential direction, and a seal member 106 is fitted into the groove. When the large-diameter lower end portion of the seal pipe 102 is inserted into the through hole 105a, the seal member 106 comes into close contact with the lower end portion of the seal pipe 102. Therefore, the internal space of the porcelain tube 101 is sealed by the seal member 106, and insulating oil and the like filled in the porcelain tube 101 are prevented from leaking out of the through hole 105a.

[0006] Furthermore, when the power cable 2 expands and contracts as described above, the seal pipe 102 moves up and down in response to the expansion and contraction of the power cable 2, but during this time, the seal member 106 remains in close contact with the lower end portion of the seal pipe 102, so that the porcelain tube 101 is kept sealed by the seal member 106. Furthermore, in order to prevent the large-diameter lower end portion of the seal pipe 102 from slipping downward when the power cable 2 expands downward, a protruding member 107 that protrudes outward is provided at the large-diameter lower end portion of the seal pipe 102.

[0007] The conventional termination connection part 100 shown in Figure 6 is configured as described above, so that even if the power cable 2 is extended downward, the large-diameter lower end part of the seal pipe 102 is prevented from slipping downward and causing insulating oil and the like to leak from the through hole 105a.

[0008] Japanese Patent Application Laid-Open No. 2020-182270

[0009] However, in the structure of the conventional termination part 100 described above, stress due to the weight of the insulating oil inside the porcelain tube 101, stress due to expansion and contraction of the power cable 2, and stress due to the shrink-back phenomenon occurring in the sheath layer 25 of the power cable 2 are all applied to the seal pipe 102. Therefore, if the seal pipe 102 moves downward and the protruding member 107 abuts against the bottom plate portion 105 of the porcelain tube 101, and an even stronger downward stress is applied to the seal pipe 102, the protruding member 107 may be damaged, and the seal pipe 102 may slide downward.

[0010] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a terminal connection part for a power cable that can prevent a seal pipe provided around a power cable placed in a vertically placed porcelain tube from slipping downward from the bottom plate part at the lower end of the porcelain tube.

[0011] In order to solve the above problem, the invention of claim 1 provides an end connection part for a power cable having a conductor, an insulating layer, an outer semiconductive layer, a metal shielding layer, and a sheath layer, comprising: a porcelain tube into which the power cable, which has been stripped in stages to expose each layer, is inserted and an insulating fluid is filled between the porcelain tube and the power cable; a conductor fixing part that fixes the conductor, which is drawn out from the upper end of the porcelain tube to the porcelain tube; a stress cone attached to cover a part of the insulating layer and a part of the outer semiconductive layer; a lower flange connected to the lower end of the porcelain tube to close the porcelain tube and having a through hole for passing the power cable; a seal pipe that surrounds the outer semiconductive layer of the power cable, and whose upper end is sealed and fixed to the outer semiconductive layer, and which forms a sealed state between the outer peripheral surface of its lower end and the inner peripheral surface of the through hole and is movable in the vertical direction relative to the lower flange in response to the expansion and contraction of the power cable in the vertical direction; and a lower protection part that surrounds the power cable and is fixed to the underside of the lower flange. a corrosion prevention structure that fixes the lower end of the lower protection part to the metal shielding layer and the sheath layer of the power cable, wherein the seal pipe and the lower protection part are separated from each other.

[0012] The invention described in claim 2 is characterized in that, in the terminal connection portion of the power cable described in claim 1, a stopper is provided to stop the movement of the seal pipe at a predetermined position relative to the lower flange when the seal pipe moves downward.

[0013] The invention described in claim 3 is the power cable terminal connection part described in claim 2, characterized in that the stopper is provided at a position above the lower flange of the seal pipe.

[0014] The invention described in claim 4 is characterized in that, in the terminal connection portion of the power cable described in claim 3, the stopper is provided so that a portion near the lower end of the seal pipe, which is located above the lower flange, protrudes outward from the seal pipe.

[0015] A fifth aspect of the present invention is the power cable terminal connection part according to the second aspect, wherein the stopper is provided at a position lower than the lower flange.

[0016] The invention described in claim 6 is characterized in that, in the termination connection portion of the power cable described in claim 5, the fastening portion provided at the upper end of the lower protective portion for fastening and fixing the lower protective portion to the lower flange is configured to abut against the lower end of the seal pipe when the seal pipe moves downward, thereby functioning as the stopper that stops the movement of the seal pipe.

[0017] The invention described in claim 7 is characterized in that, in the terminal connection portion of the power cable described in claim 6, the lower protection portion comprises a cylindrical cable protection tube portion that surrounds the metal shielding layer of the power cable, and the fastening portion that is provided so as to protrude outward from the upper end of the cable protection tube portion.

[0018] The invention described in claim 8 is characterized in that, in the terminal connection part of the power cable described in any one of claims 1 to 7, the seal pipe is grounded via the lower flange.

[0019] The invention described in claim 9 is characterized in that, in the terminal connection part of the power cable described in claim 8, the outer semiconductive layer of the power cable is grounded via the seal pipe and the lower flange.

[0020] The invention described in claim 10 is characterized in that, in the terminal connection part of the power cable described in any one of claims 1 to 9, the upper end of the seal pipe is tightened and fixed with a heat shrink tube.

[0021] The invention described in claim 11 is characterized in that, in the terminal connection part of the power cable described in any one of claims 1 to 10, the lower protection part is grounded via the lower flange.

[0022] The invention described in claim 12 is characterized in that, in the terminal connection part of the power cable described in claim 11, the metal shielding layer of the power cable is grounded via the lower protection part and the lower flange.

[0023] The invention described in claim 13 is characterized in that, in the terminal connection part of a power cable described in any one of claims 1 to 12, the corrosion protection structure is formed by a corrosion protection tape and an epoxy resin layer.

[0024] The invention described in claim 14 is characterized in that, in the terminal connection part of the power cable described in any one of claims 1 to 13, the corrosion prevention structure is fastened and fixed with a heat shrink tube.

[0025] According to the present invention, it is possible to prevent a seal pipe provided around a power cable arranged in a vertically-mounted porcelain tube from slipping downward from the bottom plate portion at the lower end of the porcelain tube.

[0026] Fig. 2 is a cross-sectional view showing the configuration of a termination connection part of a power cable according to the present embodiment. Fig. 3 is an enlarged view of a portion of the termination connection part of Fig. 1 including a seal pipe, a lower flange, and a lower protective part. Fig. 4 is an enlarged view showing a modified example of an upper seal structure of a seal pipe. Fig. 5 is a view showing a state in which an axial seal part of the seal pipe has slipped below a bottom plate part of a lower flange. Fig. 6 is a view showing an example of a stopper provided at a position above the lower flange of the seal pipe. Fig. 7 is a view showing an example of a stopper provided on the underside of a bottom plate part of a lower flange. Fig. 8 is a cross-sectional view showing an example of a termination connection part of a conventional power cable.

[0027] The following describes a power cable termination according to the present invention with reference to the drawings. Although the following embodiments are subject to various technical limitations that are desirable for implementing the present invention, the scope of the present invention is not limited to the following embodiments or illustrated examples.

[0028] Fig. 1 is a cross-sectional view showing the configuration of a termination connection part according to this embodiment, and Fig. 2 is an enlarged view of a portion of the termination connection part shown in Fig. 1, including the seal pipe, lower flange, and lower protective part. In this embodiment, the termination connection part 1 includes a power cable 2, a porcelain bushing 3, a conductor fixing part 4, a stress cone 5, a lower flange 6, a seal pipe 7, a lower protective part 8, and a corrosion protection structure 9.

[0029] The power cable 2 includes a conductor 21, an insulating layer 22 formed on the outer periphery of the conductor 21, an outer semiconductive layer 23 formed on the outer periphery of the insulating layer 22, a metal shielding layer 24 formed on the outer periphery of the outer semiconductive layer 23, and a sheath layer 25 covering the outer periphery of the metal shielding layer 24. The power cable 2 may be, for example, an XLPE (cross-linked polyethylene) cable in which the insulating layer 22 is made of rubber or plastic.

[0030] An extra-high voltage cable with a voltage class of 154 kV or more or 500 kV or more is used as the power cable 2, but a cable of 66 kV or more can also be used. The power cable 2 is inserted into the porcelain tube 3 with each layer exposed by step stripping, and is arranged so that the central axis faces in the vertical direction.

[0031] The porcelain bushing 3 is a composite porcelain bushing in which a hollow housing 31 made of fiber reinforced plastics (FRP) is covered with a pleated outer jacket 32 ​​made of rubber or plastic, for example. The porcelain bushing 3 can also be made of porcelain, glass, or other materials with high insulating properties.

[0032] The porcelain tube 3 is a so-called vertically-mounted type, with its longitudinal direction facing up and down. An insulating fluid 30 is filled between the porcelain tube 3 and the power cable 2 inside. In this embodiment, the insulating fluid 30 is assumed to be an insulating oil containing silicone oil as its main component, but it may also be a gel, insulating gas, or the like.

[0033] A conductor fixing portion 4 for fixing the conductor 21 of the power cable 2 to the porcelain tube 3 is attached to the upper surface of the porcelain tube 3 via an O-ring or the like (not shown). A conductive conductor pull-out rod 211 is connected to the tip of the conductor 21 of the power cable 2, and the conductor fixing portion 4 fastens and holds the conductor pull-out rod 211, thereby fixing the conductor 21 of the power cable 2 to the porcelain tube 3. The conductor pull-out rod 211 connected to the conductor 21 penetrates the upper end of the porcelain tube 3, and its upper portion is exposed to the outside, so that it is pulled out from the upper end of the porcelain tube 3.

[0034] A stress cone 5 is attached to the outer surface of the power cable 2 at the boundary between the stepped insulating layer 22 and the outer semi-conductive layer 23 so as to cover part of the insulating layer 22 and part of the outer semi-conductive layer 23. The stress cone 5 is mainly composed of a conductive part 51 for electric field relaxation and an insulating part 52 made of insulating rubber, and the conductive part 51 is electrically connected to the outer semi-conductive layer 23 of the power cable 2.

[0035] The lower flange 6 has a bottom plate 61 connected to the lower end of the porcelain tube 3 so as to close the lower end portion of the porcelain tube 3. The bottom plate 61 is made of a conductive material such as aluminum, iron, or stainless steel. The lower flange 6 also has a through hole 62 in the center of the bottom plate 61 for passing the power cable 2 through.

[0036] A cylindrical shaft seal receiving portion 63, which forms a sealed state with a shaft seal portion 72 formed at the lower end portion of the seal pipe 7 (described later), is fixed to the inner peripheral surface of the through hole 62 of the lower flange 6 over the entire circumference of the inner peripheral surface of the through hole 62. The shaft seal receiving portion 63 also serves to guide the movement of the seal pipe 7 in the vertical direction while maintaining the sealed state with the shaft seal portion 72.

[0037] The vertical length of the axial seal receiving portion 63 is determined according to the distance (length) that the seal pipe 7 moves vertically in response to the vertical expansion and contraction of the power cable 2, as will be described later. In particular, it is determined based on the distance (length) that the seal pipe 7 can move downward in response to the downward extension of the power cable 2. In other words, the length is determined so that the axial seal portion 72 of the seal pipe 7, which will be described later, does not slip out downward.

[0038] Additionally, a plurality of support insulators 10 are attached to the underside of the peripheral edge portion of the lower flange 6, and the support insulators 10 are fixed to the upper surface of the frame 11. In this manner, the porcelain tube 3 and the lower flange 6 are connected to the frame 11 via the plurality of support insulators 10. As a result, the porcelain tube 3 is fixed in an upright state on the frame 11. The bottom plate portion 61 of the lower flange 6 is grounded via the support insulators 10.

[0039] The seal pipe 7 has a cylindrical portion 71 and a cylindrical axial seal portion 72 formed at its lower end. Both the cylindrical portion 71 and the axial seal portion 72 are made of a conductive material such as metal. The outer semiconductive layer 23 of the power cable 2 is mainly inserted into the cylindrical interior of the cylindrical portion 71 and the axial seal portion 72, so that the cylindrical portion 71 and the axial seal portion 72 of the seal pipe 7 surround the outer semiconductive layer 23 of the power cable 2. A gap is formed between the cylindrical portion 71 or the axial seal portion 72 and the outer semiconductive layer 23 of the power cable 2.

[0040] Furthermore, a self-fusing tape 731 is wound around the upper end portion of the cylindrical portion 71 of the seal pipe 7 and the outer semiconductive layer 23 of the power cable 2 above it, and is fastened and fixed from the outside with a heat-shrinkable tube 732. Hereinafter, the self-fusing tape 731, the heat-shrinkable tube 732, etc. will be collectively referred to as the upper seal structure 73. Furthermore, the upper seal structure 73 is formed at a position lower than the position of the power cable 2 where the stress cone 5 is attached.

[0041] In this way, the upper seal structure 73 fixes the upper end of the cylindrical portion 71 of the seal pipe 7 to the outer semiconductive layer 23 of the power cable 2, and also seals and fixes the upper end of the cylindrical portion 71 of the seal pipe 7 to the outer semiconductive layer 23 of the power cable 2. In other words, the gap between the cylindrical portion 71 and the outer semiconductive layer 23 is sealed at its upper end by the upper seal structure 73.

[0042] Therefore, when the power cable 2 expands and contracts in the vertical direction, the seal pipe 7 can move in the vertical direction relative to the lower flange 6 in response to the expansion and contraction of the power cable 2. In addition, the gap between the cylindrical portion 71 and the outer semiconductive layer 23 is sealed by the upper seal structure 73, so that the insulating fluid 30 in the porcelain tube 3 does not enter the gap.

[0043] It is also possible to configure the seal pipe 7 so that it is fixed to the power cable 2 at the axial seal portion 72 using a self-fusing tape, a heat-shrinkable tube, or the like. However, as in the present embodiment, if the seal pipe 7 is configured to be fixed to the outer semiconductive layer 23 of the power cable 2 by the upper seal structure 73 and not fixed to the power cable 2 at the axial seal portion 72 (i.e., the portion below the seal pipe 7), it is possible to prevent the power cable 2 from bending inside the seal pipe 7 when the power cable 2 is elongated.

[0044] That is, if the seal pipe 7 is fixed to the power cable 2 on both the upper and lower sides, there is a possibility that the power cable 2 will bend inside the seal pipe 7 when the power cable 2 is stretched. However, by fixing the seal pipe 7 to the power cable 2 only on the upper side (upper seal structure 73) as in the present embodiment, the power cable 2 can move relative to the seal pipe 7 below the seal pipe 7 even when the power cable 2 is stretched, so that bending of the power cable 2 inside the seal pipe 7 can be suppressed.

[0045] Furthermore, as shown in Figure 2, by configuring the self-fusing tape 731 etc. of the upper seal structure 73 formed at the upper end of the seal pipe 7 to be tightened and fixed from the outside with a heat-shrink tube 732, it becomes possible to firmly fix the seal pipe 7 to the outer semiconductive layer 23 of the power cable 2 with the upper seal structure 73 by tightening the heat-shrink tube 732.

[0046] Additionally, a conductive metal tape layer 74 is formed on the outer surface of the upper seal structure 73, extending from the outer semiconductive layer 23 of the power cable 2 to the cylindrical portion 71 of the seal pipe 7. The metal tape layer 74 can be formed, for example, by wrapping a metal mesh tape or metal foil around the outer surface of the upper seal structure 73. The metal tape layer 74 electrically connects the outer semiconductive layer 23 of the power cable 2 and the seal pipe 7.

[0047] On the other hand, the shaft seal portion 72 of the seal pipe 7 has an inner diameter that is approximately the same as the inner diameter of the cylindrical portion 71, and an outer diameter that is larger than the outer diameter of the cylindrical portion 71. One or more grooves are formed in the outer peripheral surface of the shaft seal portion 72 in the circumferential direction, and an O-ring 75 is fitted in each groove.

[0048] When the axial seal portion 72 of the seal pipe 7 is inserted into the through hole 62 of the lower flange 6, the O-ring 75 comes into close contact with the axial seal receiving portion 63 of the lower flange 6. As a result, a sealed state is formed between the outer circumferential surface of the axial seal portion 72 at the lower end of the seal pipe 7 and the inner circumferential surface of the through hole 62 (i.e., the inner circumferential surface of the axial seal receiving portion 63). Therefore, the sealing by the O-ring 75 prevents the insulating fluid 30 in the porcelain bushing 3 from leaking out from the through hole 62 of the lower flange 6. At the same time, even if the seal pipe 7 moves up and down relative to the lower flange 6 in response to the expansion and contraction of the power cable 2 in the up and down direction as described above, the above-mentioned sealed state is maintained.

[0049] In this embodiment, the axial seal portion 72 of the seal pipe 7 and the bottom plate portion 61 of the lower flange 6 are electrically connected by a grounding conductor 76. Therefore, the outer semiconductive layer 23 of the power cable 2 is electrically connected to the bottom plate portion 61 of the lower flange 6 via the metal tape layer 74, the seal pipe 7 (the cylindrical portion 71 and the axial seal portion 72), and the grounding conductor 76.

[0050] In this embodiment, since the bottom plate portion 61 of the lower flange 6 is grounded via the support insulator 10 as described above, the seal pipe 7 is grounded via the bottom plate portion 61 of the lower flange 6, and the outer semiconductive layer 23 of the power cable 2 is grounded via the seal pipe 7 and the bottom plate portion 61 of the lower flange 6. The ground conductor 76 may be composed of one or more conductors, or may be composed of a flat braided copper wire or the like. Furthermore, if the length of the ground conductor 76 is made longer than the amount of vertical movement of the seal pipe 7, it is possible to prevent the ground conductor 76 from breaking or interfering with the vertical movement of the seal pipe 7.

[0051] Incidentally, the upper seal structure 73 of the seal pipe 7 can also be configured as shown in FIG.

[0052] Specifically, a self-fusing tape 731a is wrapped around the upper end of the cylindrical portion 71 of the seal pipe 7 and the outer semiconducting layer 23 of the power cable 2 above it, and then a heat-shrinkable tube 732a is tightened and fixed from the outside. It is also possible to further tighten and fix the upper seal structure 73 by alternately stacking self-fusing tapes 731b and 731c and heat-shrinkable tubes 732b and 732c on the outside of the self-fusing tape 731a. By forming the upper seal structure 73 in this way as a multilayer structure of the self-fusing tape 731 and the heat-shrinkable tube 732, the static friction force at the upper seal structure 73 is increased, making it possible to prevent the seal pipe 7 from shifting downward relative to the power cable 2 even when pressure is applied from the insulating fluid 30 inside the porcelain tube 3.

[0053] Furthermore, instead of or in addition to forming the conductive metal tape layer 74 on the outer surface of the upper seal structure 73, it is also possible to wrap a conductive tape 77 around the outer semiconductive layer 23 of the power cable 2 and fill the gap between the seal pipe 7 and the outer semiconductive layer 23 of the power cable 2 with the conductive tape 77. With this configuration, the outer semiconductive layer 23 of the power cable 2 and the seal pipe 7 can be electrically connected by the conductive tape 77, and the outer semiconductive layer 23 of the power cable 2 can be grounded via the seal pipe 7 or the like.

[0054] 2 , in this embodiment, the lower protection part 8 includes a cylindrical cable protection tube part 81 that surrounds the metal shielding layer 24 of the power cable 2, and a fastening part 82 that protrudes outward in a flange-like shape from the upper end of the cable protection tube part 81. The lower protection part 8 is fixed to the underside of the bottom plate part 61 of the lower flange 6 via the fastening part 82.

[0055] An O-ring 83 is disposed between the fastening portion 82 of the lower protective portion 8 and the bottom plate portion 61 of the lower flange 6, and the lower protective portion 8 is hermetically fixed to the lower flange 6 by fastening the fastening portion 82 of the lower protective portion 8 to the underside of the bottom plate portion 61 of the lower flange 6. The lower protective portion 8 is fixed to a position below the lower flange 6 where the cylindrical shape of the cable protection tube portion 81 is concentric with the circular shape of the through-hole 62 of the lower flange 6 and the cylindrical shape of the seal pipe 7.

[0056] The lower protective part 8 is made of a conductive material such as metal, and therefore, by fastening the lower protective part 8 to the bottom plate part 61 of the lower flange 6, the lower protective part 8 is grounded via the bottom plate part 61 of the lower flange 6.

[0057] The metal shielding layer 24 of the power cable 2 is mainly inserted inside the lower protective part 8, and the lower protective part 8 surrounds the metal shielding layer 24 of the power cable 2. A gap is formed between the lower protective part 8 and the metal shielding layer 24 of the power cable 2. This gap is connected to the gap between the power cable 2 and the seal pipe 7 and the gap between the power cable 2 and the through-hole 62 of the lower flange 6, and forms a single gap as a whole.

[0058] As shown in Figures 1 and 2, the outer semiconductive layer 23 may be exposed from the lower protective portion 8 through the through hole 62 in the lower flange 6 to the seal pipe 7 in the gap extending from the top of the seal pipe 7 to the bottom of the lower protective portion 8. When the power cable 2 is wound around a drum or the like before installation, the power cable 2 may have a tendency to bend. In such cases, the presence of a layer (e.g., a metal shielding layer 24) outside the outer semiconductive layer 23 tends to make the bend more likely to remain. Therefore, by removing the outer layer so that the outer semiconductive layer 23 is exposed within the above range, the bending of the power cable 2 can be easily corrected and the power cable 2 can be adjusted to pass more centrally through the through hole 62. This suppresses uneven contact pressure around the axial seal portion 72 due to uneven contact of the power cable 2 against the seal pipe 7, allowing the axial seal portion 72 to be in uniform contact with the inner wall of the through hole 62 in the lower flange 6.

[0059] This also makes it possible to reduce the inner diameter of the seal pipe 7 and bring it closer to the outer diameter of the outer semiconductive layer 23, thereby further reducing the diameters of the central holes of the cable protection tubular portion 81 and the fastening portion 82 and downsizing the lower protection portion 8. Furthermore, by making the diameter of the cable insertion hole formed by the central holes of the cable protection tubular portion 81 and the fastening portion 82 (the smaller of the inner diameter of the cable protection tubular portion 81 and the inner diameter of the fastening portion 82) larger than the inner diameter of the seal pipe 7 and smaller than the inner diameter of the through hole 62, even when the seal pipe 7 and the axial seal portion 72 descend to their lower limits due to elongation of the power cable 2 and bring the upper surface of the fastening portion 82 and the lower surface of the axial seal portion 72 into contact with each other, the contact area can be sufficiently secured to function as a stopper.

[0060] Furthermore, for example, after satisfying the relationship between the inner diameters of the above-mentioned parts (the diameter of the cable insertion hole is larger than the inner diameter of the seal pipe 7 and smaller than the inner diameter of the through hole 62), the outer diameter of the cable protection cylindrical part 81 may be made smaller than the outer diameter of the corrosion prevention structure 9, thereby making the cylindrical part 71 and the axial seal part 72 of the seal pipe 7 themselves smaller and reducing the downward force that the seal pipe 7 receives from the insulating fluid 30.

[0061] The seal pipe 7 and the lower protective part 8 are separated from each other vertically. When assembling the termination 1, the seal pipe 7 (the lower end portion of the shaft seal part 72) is assembled in a state separated from the lower protective part 8 (the upper surface of the fastening part 82), and as described above, the seal pipe 7 is configured to be able to move vertically relative to the lower flange 6 in response to the vertical expansion and contraction of the power cable 2. Note that, because the lower protective part 8 is fixed to the lower flange 6 as described above, it does not move relative to the lower flange 6.

[0062] The lower end of the lower protective part 8 is fixed to the metal shielding layer 24 and the sheath layer 25 of the power cable 2 by a corrosion protection structure 9. In addition, the corrosion protection structure 9 seals the gap between the lower protective part 8 and the metal shielding layer 24 of the power cable 2.

[0063] The corrosion protection structure 9 can be formed, for example, by wrapping a corrosion protection tape 91 from the lower portion of the lower protective part 8 to the metal shielding layer 24 and sheath layer 25 of the power cable 2, and then applying an epoxy resin layer 92 to the outside of the tape. With this configuration, the corrosion protection structure 9 can reliably fix the lower protective part 8 to the metal shielding layer 24 and sheath layer 25 of the power cable 2, and can reliably prevent the metal shielding layer 24 of the power cable 2 from being corroded by rainwater, etc. In this case, for example, glass tape or the like may be impregnated with epoxy resin and then wrapped around the tape.

[0064] It is also possible to configure the corrosion protection structure 9 so that the corrosion protection tape 91, epoxy resin layer 92, etc. are fastened from the outside with a heat shrink tube 93. With this configuration, the corrosion protection structure 9 can more firmly fix the lower protection part 8 to the metal shielding layer 24 and sheath layer 25 of the power cable 2 by fastening the heat shrink tube 93. The corrosion protection structure 9 also seals any gap between the lower protection part 8 and the metal shielding layer 24 of the power cable 2.

[0065] Within the corrosion protection structure 9, the lower protective part 8 and the metal shielding layer 24 of the power cable 2 are electrically connected by a grounding conductor 94. The grounding conductor 94 may be a conductor, and may be made of a flat-braided copper wire or the like. The metal shielding layer 24 of the power cable 2 is electrically connected to the bottom plate part 61 of the lower flange 6 via the grounding conductor 94 and the lower protective part 8, so that the metal shielding layer 24 of the power cable 2 is grounded via the lower protective part 8 and the bottom plate part 61 of the lower flange 6.

[0066] Next, the operation of the power cable termination 1 according to this embodiment will be described. In the structure of the conventional termination 100 described above, all of the stresses caused by the weight of the insulating oil inside the porcelain tube 101, expansion and contraction of the power cable 2, and shrink-back occurring in the sheath layer 25 of the power cable 2, are applied to the seal pipe 102. Therefore, if a stronger downward stress is applied to the seal pipe 102 while the protruding member 107 of the seal pipe 102 is in contact with the bottom plate 105 of the porcelain tube 101, the protruding member 107 may be damaged, causing the seal pipe 102 to slide downward.

[0067] In contrast, in the termination 1 according to this embodiment, stress due to the weight of insulating fluid 30 such as insulating oil inside the porcelain tube 3 and the expansion and contraction of the power cable 2 is mainly applied to the seal pipe 7, but stress due to the shrink-back phenomenon occurring in the sheath layer 25 of the power cable 2 is applied to the lower protective part 8. Furthermore, since the seal pipe 7 and the lower protective part 8 are separated from each other, the stress is distributed between the seal pipe 7 and the lower protective part 8.

[0068] Therefore, even if the seal pipe 7 moves up and down relative to the lower flange 6 in response to the vertical expansion and contraction of the power cable 2, it is possible to prevent a strong stress from being applied to the seal pipe 7 that would cause the seal pipe 7 to slip downward from the bottom plate portion 61 of the lower flange 6. Therefore, the designed position of the seal pipe 7 with respect to the bottom plate portion 61 of the lower flange 6 is maintained, and even if the seal pipe 7 moves up and down in response to the vertical expansion and contraction of the power cable 2, the O-ring 75 of the shaft seal portion 72 of the seal pipe 7 is maintained in close contact with the shaft seal receiving portion 63 provided on the inner circumferential surface of the through hole 62 of the lower flange 6.

[0069] Even if the seal pipe 7 moves up and down, the sealed state formed between the outer peripheral surface of the shaft seal portion 72 at the lower end of the seal pipe 7 and the inner peripheral surface of the through hole 62 (i.e., the inner peripheral surface of the shaft seal receiving portion 63) is maintained. Therefore, even if the seal pipe 7 moves up and down in response to the expansion and contraction of the power cable 2 in the up and down direction, it is possible to prevent the insulating oil and the like in the porcelain tube 3 from leaking out from the through hole 62 part of the lower flange 6.

[0070] As described above, in the power cable termination 1 according to this embodiment, the member surrounding the power cable 2 at the lower flange 6 at the bottom of the vertically-installed porcelain tube 3 is separated into the seal pipe 7 and the lower protective portion 8. The lower protective portion 8 is fixed to the underside of the lower flange 6, and the lower end of the lower protective portion 8 is fixed to the metal shielding layer 24 and the sheath layer 25 of the power cable 2 via the corrosion protection structure 9. The seal pipe 7 is fixed to the outer semiconductive layer 23 of the power cable 2 below the stress cone, allowing it to move vertically relative to the lower flange 6 in response to the vertical expansion and contraction of the power cable 2, and the sealed state formed between the outer peripheral surface of the lower end of the seal pipe 7 and the inner peripheral surface of the through hole 62 provided in the lower flange 6 is maintained even when the seal pipe 7 moves vertically.

[0071] Therefore, at the power cable termination 1, it is possible to prevent the seal pipe 7 provided around the power cable 2 arranged in the vertically-placed porcelain tube 3 from slipping downward from the bottom plate portion 61 at the lower end of the porcelain tube 3. Therefore, even if the seal pipe 7 moves up and down in response to the vertical expansion and contraction of the power cable 2, it is possible to prevent the insulating fluid 30, such as insulating oil, inside the porcelain tube 3 from leaking out from the through hole 62 in the lower flange 6.

[0072] Furthermore, even if the power cable 2 expands and contracts in the vertical direction, the seal pipe 7 simply moves vertically relative to the bottom plate portion 61 of the lower flange 6 in response to this expansion and contraction. Therefore, even if the power cable expands relatively significantly downward due to heat generation in the conductor, it is possible to prevent the stress cone 5 from being deformed or damaged due to large stress being applied to the stress cone 5 or the axial seal portion 72 of the seal pipe 7, etc., and it is also possible to prevent the axial seal portion 72 of the seal pipe 7 from being deformed. This makes it possible to prevent a situation in which the axial seal portion 72 is deformed and the insulating fluid 30 inside the porcelain tube 3 leaks to the outside.

[0073] In such a termination, when the current value of the power cable increases, the power cable elongates relatively significantly, particularly downward, due to heat generation in the conductor, which can cause large stresses to be applied to the stress cone and the insulating fluid seal. This stress can cause deformation or damage to the stress cone, and deformation of the insulating fluid seal can cause the insulating fluid inside the porcelain insulator tube to leak out.

[0074] Incidentally, when the seal pipe 7 moves downward following the downward extension of the power cable 2 as described above, it is also possible to provide a stopper for stopping the movement at a predetermined position relative to the lower flange 6. That is, for example, as shown in Fig. 4A, if the axial seal portion 72 of the seal pipe 7 slides downward from the bottom plate portion 61 of the lower flange 6, the insulating fluid 30 in the porcelain bushing 3 will flow downward through the through hole 62 of the lower flange 6.

[0075] 4B , the stopper 12 can be provided on the seal pipe 7 at a position above the lower flange 6. Specifically, the stopper 12 can be provided in a portion near the lower end of the seal pipe 7 (the portion of the shaft seal portion 72) that is located above the bottom plate portion 61 of the lower flange 6 so as to protrude outward from the seal pipe 7.

[0076] With this configuration, when the seal pipe 7 moves downward following the downward extension of the power cable 2, the stopper 12 engages from above with the bottom plate portion 61 of the lower flange 6. Therefore, it is possible to stop the movement of the seal pipe 7 at a predetermined position relative to the lower flange 6, i.e., at a position where a sealed state is maintained between the outer circumferential surface of the axial seal portion 72 of the seal pipe 7 and the inner circumferential surface of the through hole 62 of the lower flange 6, and it is possible to prevent the axial seal portion 72 from slipping below the bottom plate portion 61 of the lower flange 6 and causing the insulating fluid 30 to flow downward through the through hole 62.

[0077] When the protruding member 107 (see FIG. 6 ) in the conventional termination 100 described above abuts against the bottom plate 105, all of the stresses caused by the weight of the insulating oil inside the porcelain tube 101, expansion and contraction of the power cable 2, and shrink-back occurring in the sheath layer 25 of the power cable 2, etc. are applied to the protruding member 107. In contrast, in this embodiment, because the seal pipe 7 and the lower protective part 8 are separated as described above, when the stopper 12 abuts against the bottom plate 61 of the lower flange 6, at least stress caused by shrink-back occurring in the sheath layer 25 of the power cable 2, etc. is not applied.

[0078] Therefore, as shown in Figure 4B, even if the seal pipe 7 moves downward in response to the downward extension of the power cable 2 and the stopper 12 abuts against the bottom plate portion 61 of the lower flange 6, it is possible to prevent the stopper 12 from being damaged and the axial seal portion 72 of the seal pipe 7 from slipping down below the bottom plate portion 61 of the lower flange 6.

[0079] On the other hand, the stopper 12 can also be provided at a position lower than the bottom plate portion 61 of the lower flange 6. For example, as shown in Fig. 5, the stopper 12 can be provided around the through hole 62 on the underside of the bottom plate portion 61 of the lower flange 6. In this case, the stopper 12 can be formed in the shape of a disk having a through hole with a diameter smaller than the inner diameter of the through hole 62, or can be formed from one or more hook-shaped members with an L-shaped cross section.

[0080] 2 , when a fastening portion 82 is provided at the upper end of the lower protective portion 8 to fasten the lower protective portion 8 to the bottom plate portion 61 of the lower flange 6, the fastening portion 82 can be configured to abut against the shaft seal portion 72 at the lower end of the seal pipe 7 when the seal pipe 7 moves downward, thereby functioning as a stopper 12 to stop the movement of the seal pipe 7. In other words, in this case, the inner diameter of the flange-shaped fastening portion 82, i.e., the inner diameter of the cylindrical cable protection tube portion 81 of the lower protective portion 8, is configured to be smaller than the inner diameter of the through hole 62 in the lower flange 6 (the inner diameter of the cylindrical shaft seal receiver 63 in FIG. 2 ).

[0081] With this configuration, when the seal pipe 7 moves downward following the downward extension of the power cable 2, the fastening portion 82 of the lower protective portion 8 comes into contact with the lower surface of the axial seal portion 72 of the seal pipe 7. Therefore, it is possible to make the fastening portion 82 of the lower protective portion 8 function as a stopper 12 that stops the movement of the seal pipe 7 at a predetermined position relative to the lower flange 6, that is, at a position where a sealed state is maintained between the outer peripheral surface of the axial seal portion 72 of the seal pipe 7 and the inner peripheral surface of the through hole 62 of the lower flange 6.

[0082] This makes it possible to prevent the shaft seal portion 72 of the seal pipe 7 from slipping downward from the bottom plate portion 61 of the lower flange 6 and causing the insulating fluid 30 to flow downward through the through hole 62. Another advantage is that the fastening portion 82 of the lower protective portion 8 can be used as the stopper 12, which eliminates the need to provide a new stopper 12.

[0083] Incidentally, when the inner diameter of the fastening portion 82, i.e., the inner diameter of the cylindrical cable protection tube portion 81 of the lower protection portion 8, is configured to be smaller than the inner diameter of the through-hole 62 of the lower flange 6 as described above, the cable protection tube portion 81 of the lower protection portion 8 becomes slightly thicker than the power cable 2 and is located very close to the power cable 2, as shown in Fig. 2. In other words, the cylindrical cable protection tube portion 81 of the lower protection portion 8 surrounds the power cable 2 at a position very close to the power cable 2.

[0084] When the power cable 2 expands or contracts in the vertical direction due to heat generation or the like of the conductor 21, a force may act on the power cable 2 extending in the vertical direction within the porcelain insulator tube 3, bending it in the horizontal direction (i.e., for example, the left-right direction in FIG. 2 or a direction perpendicular to the paper surface). This causes the seal pipe 7 fixed to the power cable 2 by the upper seal structure 73 to tilt from the vertical direction and move in a direction tilted from the vertical direction in response to the movement of the power cable 2. This may result in excessive force being applied to the seal pipe 7, causing damage, or the axial seal portion 72 of the seal pipe 7 not completely sealing the through hole 62 in the lower flange 6, causing the insulating fluid 30 in the porcelain insulator tube 3 to leak out from the through hole 62 in the lower flange 6.

[0085] However, as in this embodiment, when the cylindrical cable protection tube portion 81 of the lower protection portion 8 is configured to surround the power cable 2 at a position very close to the power cable 2, the power cable 2 comes into contact with the cable protection tube portion 81 of the lower protection portion 8 as soon as the power cable 2 starts to bend horizontally. Therefore, the lower protection portion 8 prevents the power cable 2 from bending at least in the lower protection portion 8 and the portion of the seal pipe 7 nearby.

[0086] Therefore, the seal pipe 7 fixed to the power cable 2 by the upper seal structure 73 is prevented from being tilted from the vertical direction, and the seal pipe 7 moves in the vertical direction following the movement of the power cable 2. This makes it possible to prevent the seal pipe 7 from being damaged by excessive force and to prevent the insulating fluid 30 in the porcelain tube 3 from leaking out from the through-hole 62 of the lower flange 6.

[0087] It goes without saying that the present invention is not limited to the above-described embodiments, and can be modified as appropriate without departing from the spirit of the present invention.

[0088] The present invention has industrial applicability to the termination connection of power cables.

[0089] DESCRIPTION OF SYMBOLS 1 Termination connection part (power cable termination connection part jig) 2 Power cable 3 Porcelain tube 4 Conductor fixing part 5 Stress cone 6 Lower flange 7 Seal pipe 8 Lower protective part 9 Corrosion prevention structure 12 Stopper 21 Conductor 22 Insulating layer 23 Outer semiconducting layer 24 Metal shielding layer 25 Sheath layer 30 Insulating fluid 62 Through hole 72 Shaft seal part (lower end of seal pipe) 81 Cable protection tube part 82 Fastening part 91 Corrosion prevention tape 92 Epoxy resin layer 93 Heat shrink tube 732 Heat shrink tube

Claims

1. In a terminal connection part of a power cable having a conductor, an insulating layer, an outer semiconductive layer, a metal shielding layer, and a sheath layer, a porcelain bushing into which the power cable, which has been stripped to expose each layer, is inserted and into which an insulating fluid is filled between the power cable and the porcelain bushing; a conductor fixing portion that fixes the conductor drawn out from the upper end of the porcelain tube to the porcelain tube; a stress cone attached to cover a portion of the insulating layer and a portion of the outer semiconducting layer; a lower flange connected to a lower end of the porcelain bushing to close the porcelain bushing, the lower flange having a through hole for passing the power cable therethrough; a seal pipe that surrounds the outer semiconductive layer of the power cable, has an upper end sealed and fixed to the outer semiconductive layer, and forms a sealed state between an outer peripheral surface of a lower end of the seal pipe and an inner peripheral surface of the through hole, and is movable in the vertical direction relative to the lower flange in response to expansion and contraction of the power cable in the vertical direction; a lower protection part fixed to a lower side of the lower flange while surrounding the power cable; a corrosion prevention structure that fixes a lower end of the lower protection part to the metal shielding layer and the sheath layer of the power cable; Equipped with 10. A power cable termination, comprising: a seal pipe and a lower protection portion separated from each other;

2. 2. The power cable terminal connection part according to claim 1, further comprising a stopper for stopping the downward movement of the seal pipe at a predetermined position relative to the lower flange.

3. 3. The power cable terminal connection part according to claim 2, wherein the stopper is provided at a position above the lower flange of the seal pipe.

4. The power cable termination connection portion according to claim 3, characterized in that the stopper is provided so that a portion near the lower end of the seal pipe, which is located above the lower flange, protrudes outward from the seal pipe.

5. 3. The power cable terminal connection part according to claim 2, wherein the stopper is provided at a position lower than the lower flange.

6. The terminal connection portion of the power cable as described in claim 5, characterized in that the fastening portion provided at the upper end of the lower protective portion for fastening and fixing the lower protective portion to the lower flange is configured to abut against the lower end of the seal pipe when the seal pipe moves downward, thereby functioning as a stopper that stops the movement of the seal pipe.

7. 7. The power cable termination connection portion according to claim 6, wherein the lower protection portion comprises a cylindrical cable protection tube portion that surrounds the metal shielding layer of the power cable, and the fastening portion that is provided so as to protrude outward from an upper end of the cable protection tube portion.

8. 8. The power cable termination according to claim 1, wherein the seal pipe is grounded via the lower flange.

9. 9. The power cable termination according to claim 8, wherein the outer semiconductive layer of the power cable is grounded via the seal pipe and the lower flange.

10. 2. The power cable terminal connection part according to claim 1, wherein an upper end of the seal pipe is fastened and fixed with a heat shrinkable tube.

11. The power cable termination according to claim 1 , wherein the lower protection portion is grounded via the lower flange.

12. 12. The power cable termination according to claim 11, wherein the metallic shielding layer of the power cable is grounded via the lower protection portion and the lower flange.

13. 2. The power cable termination according to claim 1, wherein the anticorrosion structure is formed of an anticorrosion tape and an epoxy resin layer.

14. The power cable terminal connection part according to claim 13, wherein the corrosion prevention structure is fastened and fixed with a heat shrinkable tube.