Power cable termination structure

Abstract

To provide a termination structure for a power cable of which the insulation strength is improved, and a bushing.SOLUTION: The present invention relates to a termination structure for a power cable comprising: a terminal part of the power cable including a conductor, an insulation layer, an external semiconductor layer and a shield layer successively from the inside; a bushing covering a tip-side portion in the terminal part of the power cable; and a first metal fitting covering a root-side portion in the terminal part of the power cable. The bushing includes a plurality of end faces disposed to be directed to the root side. The plurality of end faces includes: a first face to which a tip portion of the first metal fitting is mounted; a second face to which a second metal fitting for fixing the bushing to a predetermined object is mounted; and a third face disposed between the first face and the second face in such a manner that the first metal fitting and the second metal fitting are disposed separately in a radial direction of the bushing. The third face is disposed closer to the root side than the first face and the second face.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a termination structure and a porcelain bushing for a power cable. [Background technology]

[0002] As a termination structure of a power cable, Fig. 11 of Patent Document 1 discloses a termination connection part that is directly connected to a gas insulated switchgear (GIS). Hereinafter, the termination connection part of the power cable shown in Fig. 11 of Patent Document 1 will be referred to as a conventional structure. The conventional structure includes a terminal part of the power cable, a stress cone, an insulating porcelain tube, and a cylindrical protective metal fitting.

[0003] The terminal portion of the power cable is step-stripped. Therefore, the end of the conductor, the end of the insulating layer, the end of the outer semiconducting layer, and the end of the shielding layer are partially exposed, in that order, from the tip side of the terminal portion of the power cable. The insulating porcelain tube described above covers the tip side portion and the stress cone of the terminal portion of the power cable. The protective metal fitting described above covers the base side portion of the terminal portion of the power cable. The tip side is the conductor side. The base side is the shielding layer side.

[0004] The insulating porcelain tube is fixed to the GIS case by bolts via a circular plate-shaped mounting flange. The mounting flange is disposed in contact with a circular plate-shaped flange provided on the base side of the insulating porcelain tube. The protective metal fitting is electrically connected to the shielding layer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2005-006424 A Summary of the Invention [Problem to be solved by the invention]

[0006] It is desirable to improve the insulation strength of the power cable termination structure such as the conventional structure described above, particularly between the shielding layer of the terminal portion of the power cable and a fixing fitting such as a mounting flange disposed on the base side of the insulating pipe.

[0007] An object of the present disclosure is to provide a termination structure for a power cable having excellent insulation strength. Another object of the present disclosure is to provide a porcelain tube capable of constructing a termination structure for a power cable having excellent insulation strength. [Means for solving the problem]

[0008] A termination structure for a power cable according to one embodiment of the present disclosure includes a terminal portion of a power cable having a conductor, an insulating layer, an outer semiconducting layer, and a shielding layer in that order from the inside, a porcelain tube covering a tip end portion of the terminal portion of the power cable, and a first metal fitting covering a base end portion of the terminal portion of the power cable. The porcelain tube has a plurality of end faces arranged to face the base end. The plurality of end faces include a first surface to which the tip end portion of the first metal fitting is attached, a second surface to which a second metal fitting for fixing the porcelain tube to a predetermined object is attached, and a third surface arranged between the first surface and the second surface such that the first metal fitting and the second metal fitting are arranged apart in the radial direction of the porcelain tube. The third surface is arranged closer to the base end than the first surface and the second surface.

[0009] A porcelain tube according to one aspect of the present disclosure is used in a termination structure of a power cable, and includes a first end portion arranged on the tip side of a terminal portion of the power cable, a second end portion arranged on the base side of the terminal portion of the power cable, and a plurality of end faces arranged to face the second end side. The plurality of end faces include a first surface, a second surface arranged radially outward of the porcelain tube than the first surface, and a third surface arranged between the first surface and the second surface. The third surface is arranged on the second end side of the first surface and the second surface. Effect of the Invention

[0010] The termination structure of the power cable according to the present disclosure has excellent dielectric strength. The porcelain bushing according to the present disclosure can be used to construct a termination structure of the power cable having excellent dielectric strength. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a partial cross-sectional view showing a termination structure of a power cable according to a first embodiment. [Diagram 2] FIG. 2 is an enlarged view showing a portion on the second end side of the porcelain tube in the termination structure of the power cable according to the first embodiment shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] [Description of the embodiments of the present disclosure] In the above-mentioned conventional structure, the insulation distance between the shielding layer of the terminal portion of the power cable and the fixing metal fitting such as the above-mentioned mounting flange corresponds to the insulation distance between the above-mentioned protective metal fitting and the above-mentioned fixing metal fitting. In the following description, of the two ends of the above-mentioned insulating porcelain tube, the end located at the root side of the terminal portion of the power cable is called the lower end. The end face on the lower end side is called the lower end face. The flange of the above-mentioned insulating porcelain tube extends from the outer circumferential surface of the cylindrical portion constituting the lower end side portion of the insulating porcelain tube toward the outside in the radial direction of the insulating porcelain tube. The above-mentioned flange is provided so that the lower end face of the cylindrical portion is located on the lower end side of the lower end face of the flange. These two lower end faces are connected by the outer circumferential surface of the cylindrical portion. The above-mentioned protective metal fitting is attached to the lower end face of the cylindrical portion. The above-mentioned fixing metal fitting is attached to the lower end face of the flange of the insulating porcelain tube. Therefore, the insulation distance between the above-mentioned protective metal fitting and the above-mentioned fixing metal fitting is approximately equal to the distance along the longitudinal direction of the above-mentioned insulating porcelain tube on the outer circumferential surface of the cylindrical portion located between the above-mentioned two lower end faces. In other words, the insulation distance is equal to the length of a straight line that connects the two lower end surfaces along the longitudinal direction. Hereinafter, this insulation distance may be referred to as the insulation distance of the conventional structure. The present disclosure proposes a structure having an insulation distance longer than that of the conventional structure. First, the contents of the embodiments of the present disclosure will be listed and described.

[0013] (1) A termination structure for a power cable according to one embodiment of the present disclosure includes a terminal portion of a power cable having a conductor, an insulating layer, an outer semiconducting layer, and a shielding layer in this order from the inside, a porcelain tube covering a tip end portion of the terminal portion of the power cable, and a first metal fitting covering a base end portion of the terminal portion of the power cable. The porcelain tube has a plurality of end faces arranged to face the base end. The plurality of end faces include a first surface to which the tip portion of the first metal fitting is attached, a second surface to which a second metal fitting for fixing the porcelain tube to a predetermined object is attached, and a third surface arranged between the first surface and the second surface such that the first metal fitting and the second metal fitting are arranged apart from each other in the radial direction of the porcelain tube. The third surface is arranged closer to the base end than the first surface and the second surface.

[0014] In the power cable termination structure of the present disclosure, the insulation distance between the first metal fitting functioning as the protective metal fitting and the second metal fitting functioning as a fixing metal fitting for the mounting flange or the like is longer than the insulation distance in the conventional structure. The reason for this will be described later. The shielding layer of the power cable is electrically connected to the first metal fitting. Therefore, in the power cable termination structure of the present disclosure, the insulation distance between the shielding layer and the second metal fitting is longer than the insulation distance in the conventional structure. In this respect, the power cable termination structure of the present disclosure has superior insulation strength to the conventional structure.

[0015] Since the third surface is disposed closer to the root side of the terminal portion of the power cable than the first surface and the second surface, the porcelain tube has a tubular portion extending toward the root side than the first surface and the second surface. The third surface is an end surface of the tubular portion disposed so as to face the root side. The insulation distance between the first metal fitting disposed on the first surface and the second metal fitting disposed on the second surface is a length along the surface of the tubular portion including the third surface. For example, if the tubular portion is cylindrical, the insulation distance between the first metal fitting and the second metal fitting is the sum of the following three distances. The first distance is a distance along the longitudinal direction of the porcelain tube on the inner peripheral surface of the cylinder. The inner peripheral surface of the cylinder connects the first surface and the third surface. The second distance is a distance along the longitudinal direction on the outer peripheral surface of the cylinder. The outer peripheral surface of the cylinder connects the third surface and the second surface. The third distance is a distance along the radial direction of the porcelain tube on the third surface connecting the inner peripheral surface and the outer peripheral surface. In the above-mentioned conventional structure, the first surface and the third surface coincide, so to speak. Therefore, the insulation distance of the conventional structure is only the second distance, which is shorter than the total value.

[0016] (2) As an example of a termination structure of a power cable disclosed herein, the porcelain tube has a cylindrical tubular portion extending toward the root side beyond the first surface and the second surface, and the third surface is an end face of the tubular portion.

[0017] The tubular portion of the porcelain tube has a simple cylindrical shape. This porcelain tube is easy to mold, and is therefore easy to manufacture. As will be described later, the length of the tubular portion can be easily adjusted.

[0018] (3) As an example of the power cable termination structure of (2) above, the first surface and the second surface are disposed at the same position in the longitudinal direction of the porcelain tube.

[0019] In the above case, the above-mentioned insulation distance can be ensured to be longer than when the first surface and the second surface are misaligned in the longitudinal direction of the insulator tube. In this respect, the power cable termination structure of the above embodiment has even better insulation strength. Also, compared to when the first surface and the second surface are misaligned in the longitudinal direction, the internal space of the tubular portion of the insulator tube is larger. Therefore, the portion of the first fitting that is disposed inside the tubular portion is larger. In this respect, the tubular portion can easily protect the tip portion of the first fitting.

[0020] (4) An example of a termination structure of the power cable of (3) above includes a stress cone covering an end of the insulating layer exposed from the outer semiconductive layer, and a pressing fitting for pressing the stress cone from the root side toward the tip side, the first fitting being electrically connected to the shielding layer, and the portion of the pressing fitting arranged on the root side being arranged inside the tubular portion.

[0021] In the above case, the length of the pressing fitting can be made shorter than that of the conventional structure described above, as will be described later. In this respect, the length of the power cable termination structure of the above embodiment along the longitudinal direction can be made shorter than that of the conventional structure.

[0022] (5) A porcelain tube according to one aspect of the present disclosure is a porcelain tube used in a termination structure of a power cable, and includes a first end portion arranged on a tip side of a terminal portion of the power cable, a second end portion arranged on a base side of the terminal portion of the power cable, and a plurality of end faces arranged to face the second end side. The plurality of end faces include a first surface, a second surface arranged radially outward of the porcelain tube than the first surface, and a third surface arranged between the first surface and the second surface. The third surface is arranged on the second end side of the first surface and the second surface.

[0023] When constructing a termination structure for a power cable using the porcelain tube of the present disclosure, the first surface is the surface to which a first metal fitting, such as the protective metal fitting described above, is attached. The second surface is the surface to which a second metal fitting for fixing the porcelain tube to a predetermined object, such as a GIS case, is attached. In this way, the insulation distance between the first metal fitting and the second metal fitting is longer than the insulation distance of the conventional structure, as described above. Such a porcelain tube of the present disclosure can construct a termination structure for a power cable with excellent insulation strength.

[0024] [Details of the embodiment of the present disclosure] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same objects. Note that the present invention is not limited to these examples, but is indicated by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0025] [Embodiment 1] (overview) The power cable termination structure and the porcelain tube of the first embodiment will be described with reference to Figs. 1 and 2. The right side of Fig. 1 shows a cross section of the right half of the termination structure of a power cable of the first embodiment, cut along a plane parallel to the longitudinal direction of the power cable. However, the power cable is shown in its external appearance, not in its cross section. Some of the members constituting the termination structure of the power cable, such as bolts 52, 62, and 85 described below, are also shown in their external appearance, not in their cross section. The left side of Fig. 1 shows the external appearance of the left half of the termination structure of a power cable of the first embodiment. Fig. 2 shows an enlarged view of a portion of the cross section shown in Fig. 1. Note that the longitudinal direction of the power cable corresponds to the up-down direction in Figs. 1 and 2. For convenience of explanation, the sizes and size ratios of the members in Figs. 1 and 2 may differ from the actual sizes.

[0026] The power cable termination structure 1 of the first embodiment is provided at a terminal portion 2 of a power cable in order to connect the power cable to an external object (not shown). The object is, for example, a power device installed in a power facility such as a substation facility or a power receiving facility. The power device is, for example, a switchgear or a transformer. The switchgear is, for example, a gas-insulated switchgear (GIS).

[0027] The power cable termination structure 1 of the first embodiment is directly connected to a gas insulated switchgear (GIS). The basic configuration of the power cable termination structure 1 of the first embodiment can refer to a known termination connection part directly connected to a GIS. The basic configuration will be described below.

[0028] The power cable termination structure 1 of the first embodiment includes a terminal portion 2 of the power cable, a porcelain tube 3, a stress cone 4, a first fitting 5, and a pressing fitting 8. The terminal portion 2 of the power cable is step-stripped. The stress cone 4 is disposed on an insulating layer 21 in the terminal portion 2 of the power cable. The porcelain tube 3 covers the tip side portion of the terminal portion 2 of the power cable and also covers the stress cone 4. The first fitting 5 is a fitting having the function of a protective fitting in the above-mentioned conventional structure. The first fitting 5 includes a cylindrical main body portion 51. The main body portion 51 covers the root side portion of the terminal portion 2 of the power cable. The first fitting 5 is electrically connected to the shielding layer 23 of the terminal portion 2 of the power cable. The pressing fitting 8 presses the stress cone 4 from the root side toward the tip side of the terminal portion 2 of the power cable.

[0029] The tip side of the terminal portion 2 of the power cable is the conductor 20 side. The root side of the terminal portion 2 of the power cable is the opposite side to the tip side, and is the shielding layer 23 side. Hereinafter, the same side of each component in the power cable termination structure 1 on which the end of the conductor 20 is arranged may be referred to as the tip side. Also, the same side of each component in the power cable termination structure 1 on which the end of the shielding layer 23 is arranged may be referred to as the root side. The tip side is the upper side in Figures 1 and 2. The root side is the lower side in Figures 1 and 2. The tip portion of each component is the end portion arranged on the tip side of each component.

[0030] The porcelain pipe 3 has a first end 34 and a second end 35. The first end 34 is disposed at the tip side of the terminal portion 2 of the power cable. The second end 35 is disposed at the base side of the terminal portion 2 of the power cable. The porcelain pipe 3 has a plurality of end faces at the second end 35 arranged to face the base side of the terminal portion 2 of the power cable. The plurality of end faces have a first surface 31 and a second surface 32. The second surface 32 is disposed radially outward of the porcelain pipe 3 from the first surface 31. The tip of the first metal fitting 5 is attached to the first surface 31. The second metal fitting 6 for fixing the porcelain pipe 3 to a predetermined object is attached to the second surface 32. The predetermined object in this example is a GIS case 9. The second metal fitting 6 is a metal fitting having the function of a fixing metal fitting such as a mounting flange in the above-mentioned conventional structure. The radial direction of the porcelain pipe 3 corresponds to the left-right direction in FIG. 1 and FIG. 2. Moreover, the radial direction of the porcelain pipe 3 corresponds to the radial direction of the terminal portion 2 of the power cable.

[0031] In particular, the power cable termination structure 1 of the first embodiment includes the porcelain tube 3 of the first embodiment. The porcelain tube 3 of the first embodiment includes a third surface 33 in addition to the first surface 31 and the second surface 32 as an end face arranged on the root side of the terminal portion 2 of the power cable. The third surface 33 is arranged between the first surface 31 and the second surface 32. Due to the third surface 33, the first fitting 5 and the second fitting 6 are arranged apart in the radial direction of the porcelain tube 3. Furthermore, the third surface 33 is arranged closer to the root side of the terminal portion 2 of the power cable than the first surface 31 and the second surface 32. Due to the third surface 33, the insulation distance between the first fitting 5 functioning as the protective fitting and the second fitting 6 functioning as the mounting flange becomes longer than the insulation distance of the conventional structure described above.

[0032] The components constituting the power cable termination structure 1 will be described below in order. (Components) <Power cable> The power cable has, in this order from the inside, a conductor 20, an insulating layer 21, an outer semiconductive layer 22, a shielding layer 23, and a sheath 24. The power cable further has an inner semiconductive layer (not shown) inside the insulating layer 21. A representative example of such a power cable is a cross-linked polyethylene insulated vinyl sheath cable (CV cable). Known materials can be used as the constituent materials of the above-mentioned members that make up the power cable.

[0033] The power cable of this embodiment is a high-voltage cable for use with a voltage of, for example, 66 kV to 500 kV The conductor cross-sectional area, the thickness of the insulating layer 21, and the like are set according to the voltage used.

[0034] By performing the step stripping as described above, the ends of the above-mentioned components constituting the power cable are exposed. The terminal portion 2 of the power cable includes an end of the shielding layer 23 exposed from the sheath 24, an end of the outer semiconductive layer 22 exposed from the shielding layer 23, an end of the insulating layer 21 exposed from the outer semiconductive layer 22, and an end of the conductor 20 exposed from the insulating layer 21. A shielding layer wound with tape is provided between the outer semiconductive layer 22 and the shielding layer 23. For example, a metal tape such as copper mesh tape, or an insulating tape such as polyvinyl chloride (PVC) tape is used for this shielding layer wound with tape.

[0035] A compression sleeve 200 is attached to the end of the conductor 20. The compression sleeve 200 is fitted into a first electrode portion 38, which will be described later. A conductor lead (not shown) is connected to the first electrode portion 38. The power cable and the GIS are electrically connected via the first electrode portion 38 and the conductor lead.

[0036] Stress Cone The stress cone 4 is a cylindrical member for relieving electrical stress acting on the cut end of the outer semiconductive layer 22. In this example, the stress cone 4 has a spindle-shaped outer shape. The stress cone 4 has an insulating cylindrical portion 41 and a semiconductive portion 42. The insulating cylindrical portion 41 covers the end of the insulating layer 21 described above. The semiconductive portion 42 is provided on the root side and inner peripheral side of the insulating cylindrical portion 41. The semiconductive portion 42 is arranged in contact with the end of the outer semiconductive layer 22 described above.

[0037] The constituent material of the stress cone 4 may be any known material. The constituent material of the insulating tubular portion 41 is, for example, electrically insulating rubber. The constituent material of the semiconductive portion 42 is a semiconductive material. The semiconductive material is, for example, a rubber composition containing electrically insulating rubber and a conductive material such as carbon. When the above constituent materials contain rubber, the insulating tubular portion 41 can be in close contact with the end of the insulating layer 21 described above. The semiconductive portion 42 can be in close contact with the end of the outer semiconductive layer 22. The stress cone 4 in this example is a molded body in which the insulating tubular portion 41 and the semiconductive portion 42 are integrated together.

[0038] <Press fitting> The pressing fitting 8 will be described mainly with reference to Fig. 2. The pressing fitting 8 of this embodiment uses the biasing force of a spring 83 as a pressing force. A known configuration can be referenced for the basic configuration of such a pressing fitting 8.

[0039] The pressing fitting 8 comprises a ring portion 81, a shaft fitting 82, and a spring 83. The ring portion 81 is a member that comes into contact with the stress cone 4 and directly presses the stress cone 4 as shown in Fig. 1. The shaft fitting 82 is a member for adjusting the pressing force, typically a bolt. The spring 83 is a member for generating the pressing force, typically a compression spring.

[0040] The tip of the shaft fitting 82 is fastened to a circular plate-shaped flange fitting 50, which will be described later. In this example, a stud bolt 820 is attached to the shaft fitting 82. The tip of the stud bolt 820 is also fastened to the flange fitting 50. The middle part of the shaft fitting 82 is fastened to a circular plate-shaped flange fitting 80. The flange fitting 80 is arranged closer to the root of the terminal part 2 of the power cable than the flange fitting 50. A nut is fastened to the end of the shaft fitting 82 arranged closer to the root than the flange fitting 80. When this nut is tightened or loosened, the flange fitting 80 moves along the longitudinal direction of the power cable using the shaft fitting 82 as a guide. The spring 83 is arranged between the ring part 81 and the flange fitting 80 as shown in FIG. 1. Therefore, when the flange fitting 80 moves as described above, the distance between the ring part 81 and the flange fitting 80 changes. The amount of compression of the spring 83 changes due to this change. The pressing force changes according to the amount of compression of the spring 83. Therefore, the pressure is adjusted by adjusting the distance.

[0041] In this example, a guide rod 84 is disposed inside the spring 83. The spring 83 expands and contracts along the guide rod 84. A bolt 85 is inserted inside the guide rod 84. The tip of the bolt 85 is fastened to the ring portion 81. The pressing force of the spring 83 is reliably transmitted to the ring portion 81 by this bolt 85.

[0042] 1 and 2 show only one of each of the shaft fitting 82, spring 83, guide rod 84, and bolt 85, but in reality there are multiple of each. The multiple springs 83, etc. are arranged at predetermined intervals in the circumferential direction of the power cable so as to surround the outer periphery of the power cable. Therefore, a pressing force from the multiple springs 83 acts on the stress cone 4.

[0043] The flange fitting 80 is provided with a plurality of first holes and a plurality of second holes (not shown). The plurality of first holes are arranged at predetermined intervals in the circumferential direction of the flange fitting 80 so as to draw a circle. The plurality of second holes are arranged at predetermined intervals in the circumferential direction so as to draw a circle that is located on the outer periphery side of the flange fitting 80 than the circle drawn by the plurality of first holes. A guide rod 84 is inserted into each of the first holes. A spring 83 is arranged on the outer periphery of each guide rod 84. A shaft fitting 82 is inserted into each of the second holes. The spring 83, the guide rod 84, the bolt 85, and the shaft fitting 82 are attached to the flange fitting 80 so that their longitudinal directions are parallel to the longitudinal direction of the power cable. The spring 83, the guide rod 84, and the bolt 85 are arranged so as to pass through the inner peripheral hole of the flange fitting 50. To enable this arrangement, the position of the flange fitting 80 with respect to the flange fitting 50 is adjusted as follows. The portion of the flange fitting 80 where the guide rod 84 is arranged, i.e., the portion where the first hole is formed, is arranged inside the inner peripheral hole of the flange fitting 50. The portion of the flange fitting 80 where the shaft fitting 82 is arranged, i.e., the portion where the second hole is formed, is arranged so as to overlap the inner circumferential side portion of the flange fitting 50.

[0044] <Insulator> As shown in Fig. 1, the porcelain tube 3 is a cylindrical insulating member. The basic structure of the porcelain tube 3 of this example is similar to the insulating porcelain tube provided in the above-mentioned conventional structure. The basic structure of the porcelain tube 3 will be described below.

[0045] The porcelain tube 3 has two ends. Of the two ends, the first end 34 is an end located at the tip side of the terminal portion 2 of the power cable. Of the two ends, the second end 35 is an end located at the base side of the terminal portion 2 of the power cable. Usually, the second end 35 includes a portion having the maximum outer diameter of the porcelain tube 3. The portion having the maximum outer diameter is usually a flange portion 320 described later. A first electrode portion 38 is arranged on the first end 34 side. A second electrode portion 39 is arranged on the second end 35 side. The middle portion of the porcelain tube 3 has an inner peripheral surface that contacts the outer peripheral surface of the insulating tube portion 41 of the stress cone 4. A first metal fitting 5 and a second metal fitting 6 are attached to the second end 35 of the porcelain tube 3.

[0046] In particular, the porcelain tube 3 of the first embodiment has a specific shape of the second end 35. The second end 35 of the porcelain tube 3 has a portion that extends further toward the outer periphery of the porcelain tube 3 than the outer periphery of the portion of the porcelain tube 3 on the first end 34 side. The second end 35 of the porcelain tube 3 has a flange portion 320. The porcelain tube 3 has a portion that extends toward the second end 35 side beyond the flange portion 320 so that the end face arranged to face the second end 35 side of the porcelain tube 3 is composed of multiple faces rather than a single plane. Therefore, the porcelain tube 3 has multiple end faces arranged to face the second end 35 side.

[0047] The end faces include a first surface 31, a second surface 32, and a third surface 33. The first surface 31 and the second surface 32 are disposed at an interval in the radial direction of the insulator tube 3. The second surface 32 is disposed on the outer side of the first surface 31 in the radial direction. The third surface 33 is disposed between the first surface 31 and the second surface 32. However, the first surface 31, the second surface 32, and the third surface 33 are disposed shifted in the longitudinal direction of the insulator tube 3. The first surface 31 and the second surface 32 are disposed closer to the first end 34 than the third surface 33. In other words, the third surface 33 is disposed closer to the second end 35 than the first surface 31 and the second surface 32. The third surface 33 is disposed toward the opposite side to the first end 34 than the first surface 31 and the second surface 32. The insulator tube 3 having three end faces having such an arrangement relationship includes a tubular portion 330 extending toward the second end 35 than the first surface 31 and the second surface 32. The first surface 31 and the second surface 32 form an end surface that is disposed so as to face the second end 35 side of the flange portion 320. The third surface 33 forms an end surface of the cylindrical portion 330.

[0048] When the second end 35 of the insulator pipe 3 is viewed in a plane in the longitudinal direction of the insulator pipe 3, the first surface 31, the third surface 33, and the second surface 32 are arranged in this order from the inside in the radial direction of the insulator pipe 3. When the insulator pipe 3 and the terminal portion 2 of the power cable are viewed in a plane in the longitudinal direction, the first surface 31, the third surface 33, and the second surface 32 are arranged in this order from the side closer to the terminal portion 2 of the power cable. When the insulator pipe 3 and the terminal portion 2 of the power cable are viewed in a plane in the radial direction of the insulator pipe 3, the tubular portion 330 and the third surface 33 are arranged closer to the base of the terminal portion 2 of the power cable than the first surface 31 and the second surface 32.

[0049] In this example, the first surface 31, the second surface 32, and the third surface 33 are all planes parallel to the radial direction of the porcelain tube 3. In addition, the first surface 31, the second surface 32, and the third surface 33 are all annular surfaces. When the porcelain tube 3 is viewed in a plan view in the longitudinal direction of the porcelain tube 3, the first surface 31, the third surface 33, and the second surface 32 are arranged concentrically. The tube portion 330 is cylindrical. That is, the inner peripheral surface of the tube portion 330 connecting the first surface 31 and the third surface 33 is a cylindrical surface. The outer peripheral surface of the tube portion 330 connecting the second surface 32 and the third surface 33 is also a cylindrical surface. The shape of the second end portion 35 of the porcelain tube 3 is a simple shape.

[0050] In this example, the first surface 31 and the second surface 32 are disposed at the same position in the longitudinal direction of the porcelain tube 3. That is, the first surface 31 and the second surface 32 are disposed on the same virtual plane. In this case, as shown in FIG. 2, the protruding length L1 from the first surface 31 of the tubular portion 330 is equal to the protruding length L2 from the second surface 32 of the tubular portion 330. From this point of view, the shape of the second end portion 35 of the porcelain tube 3 is a simple shape. In addition, since the protruding length L1 and the protruding length L2 are equal, the length along the surface of the tubular portion 330 from the first surface 31 to the second surface 32 can be easily obtained. The above length is the sum of twice the protruding length L1 and the length L3 along the radial direction of the porcelain tube 3 at the third surface 33.

[0051] The protruding lengths L1, L2 can be appropriately selected. The longer the protruding lengths L1, L2, the longer the length along the surface of the tubular portion 330 from the first surface 31 to the second surface 32. In turn, the longer the insulation distance between the first metal fitting 5 arranged on the first surface 31 and the second metal fitting 6 arranged on the second surface 32.

[0052] The sizes of the first surface 31, the second surface 32, and the third surface 33 can be selected as appropriate. The size of the first surface 31 may be selected to correspond to the width of the flange fitting 50, which will be described later. The size of the second surface 32 may be selected to correspond to the width of the flange fitting 60, which will be described later. In this example, the first surface 31 is approximately equal to the width of the flange fitting 50.

[0053] Since the first surface 31 has a predetermined size, the inner peripheral surface 332 of the tubular portion 330 of the insulator pipe 3 is disposed radially outward of the insulator pipe 3 relative to the following inner peripheral surface 352 of the insulator pipe 3. The inner peripheral surface 352 is the inner peripheral surface of a portion of the insulator pipe 3 disposed closer to the first end 34 than the first surface 31, and is a portion close to the first surface 31. A space corresponding to the size of the first surface 31 along the radial direction is provided inside the tubular portion 330. The internal space of the tubular portion 330 can be used as a space for accommodating the root side portion of the pressing fitting 8 described above and the tip end portion of the first fitting 5 described later. In this example, the root side portion of the pressing fitting 8 is disposed inside the tubular portion 330. The root side portion of the pressing fitting 8 is the spring 83, the guide rod 84, the root side end portion of the bolt 85, the flange fitting 80, and the shaft fitting 82.

[0054] In addition, it is preferable that the corners connecting the multiple faces at the second end 35 of the porcelain tube 3 are formed with curved surfaces. As shown in Fig. 2, the above-mentioned corners are corners between the inner circumferential surface 332 of the tubular portion 330 and the first surface 31 or the third surface 33, and corners between the outer circumferential surface of the tubular portion 330 and the second surface 32 or the third surface 33. Since the above-mentioned corners are curved surfaces, cracks are less likely to occur in the porcelain tube 3 during manufacturing.

[0055] The first electrode portion 38 is a cylindrical member with a bottom. The outer peripheral surface of the first electrode portion 38 contacts the inner peripheral surface of the first end portion 34. The first electrode portion 38 has a recess into which the compression sleeve 200 is fitted. By fitting the compression sleeve 200 into the recess, the first electrode portion 38 is electrically connected to the end of the conductor 20 described above.

[0056] The second electrode portion 39 is embedded inside the second end portion 35. The above-mentioned flange metal fitting 50 is attached to the second electrode portion 39 by a metal bolt shown by a dashed line in Fig. 2. The above-mentioned shielding layer 23 and the second electrode portion 39 are electrically connected by this bolt and the flange metal fitting 50.

[0057] An electrically insulating material can be used as the material for the porcelain tube 3. The material is, for example, a resin composition such as an epoxy resin.

[0058] The porcelain tube 3 can be manufactured by a known molding method of a resin composition. For example, the porcelain tube 3 is molded in a mold so that the second end 35 is disposed upward and the first end 34 is disposed downward. This molding method can easily mold the porcelain tube 3 having a long tubular portion 330. If the tubular portion 330 is long, the protruding lengths L1, L2 of the tubular portion 330 can be adjusted by cutting the tubular portion 330. As a result, the insulation distance between the first metal fitting 5 and the second metal fitting 6 can be easily adjusted. In this case, the third surface 33 is a cut surface.

[0059] The porcelain pipe 3 of this example is a molded product in which an insulating part made of the above-mentioned resin composition is integrated with a first electrode part 38 and a second electrode part 39. Such a molded product can be manufactured, for example, by filling a flowing resin composition into a mold in which the first electrode part 38 and the second electrode part 39 are arranged at predetermined positions in the mold.

[0060] <First fitting> The first metal fitting 5 is used to protect the base side portion of the terminal portion 2 of the power cable and to ground the above-mentioned shielding layer 23. In this example, the above-mentioned second electrode portion 39 is also electrically connected to the first metal fitting 5 and is thereby grounded.

[0061] As shown in Fig. 2, the first metal fitting 5 in this example comprises a flange fitting 50, a main body 51, and a bolt 52. The main body 51 is a cylindrical member. The main body 51 is arranged so as to cover the root side portion of the terminal portion 2 of the power cable. The flange fitting 50 is an annular plate-shaped member. The flange fitting 50 is arranged so as to contact the first surface 31 of the porcelain tube 3, and is attached to the end portion 390 of the second electrode portion 39 by the bolt described above. The main body 51 is fixed to the flange fitting 50 by the bolt 52, and thereby fixed to the porcelain tube 3.

[0062] The main body 51 in this example has a first portion having a first inner diameter and a second portion having a second inner diameter. The first inner diameter is larger than the second inner diameter and smaller than the inner diameter of the tubular portion 330 of the porcelain pipe 3. Therefore, the first portion can be disposed inside the tubular portion 330.

[0063] The first portion of the main body 51 is a portion on the tip side of the main body 51. The first portion covers an intermediate portion between the end of the outer semiconductive layer 22 and the end of the shielding layer 23. The first portion also covers a portion on the base side of the pressing fitting 8 that is disposed radially outward from the terminal portion 2 of the power cable. A flange portion is provided at the tip of the main body 51, extending radially outward from the outer circumferential surface of the main body 51. A bolt 52 is attached to this flange portion, so that the tip of the main body 51 is attached to the first surface 31 of the porcelain tube 3 via the flange fitting 50.

[0064] The second portion of the main body 51 is a portion on the root side of the main body 51. The second portion mainly covers the end portion of the above-mentioned shielding layer 23. The second portion is also electrically connected to the above-mentioned shielding layer 23. A waterproof layer 500 is provided on the outer periphery of the second portion.

[0065] The width of the flange fitting 50 is the size along the radial direction of the flange fitting 50, and is the difference between the outer diameter and the inner diameter of the flange fitting 50. In this example, the width of the flange fitting 50 is approximately equal to the size along the radial direction of the porcelain tube 3 at the first surface 31 of the porcelain tube 3. In detail, the inner diameter of the flange fitting 50 is approximately equal to the inner diameter of the circle described above by the inner circumferential surface 352 of the porcelain tube 3. The outer diameter of the flange fitting 50 is slightly smaller than the inner diameter of the tubular portion 330 of the porcelain tube 3. Therefore, the end face on the tip side of the flange fitting 50 can reliably come into contact with the first surface 31.

[0066] In addition, sealing materials are arranged between the first surface 31 and the flange fitting 50, and between the flange fitting 50 and the flange portion of the main body 51. The sealing materials keep the internal space of the porcelain tube 3 and the internal space of the first fitting 5 liquid-tight and air-tight.

[0067] Known metallic materials can be used as the constituent materials of the first fitting 5 and the second fitting 6 described later. The constituent material of the main body 51 is, for example, copper, copper alloy, aluminum, aluminum alloy, etc. The constituent material of the flange fittings 50, 60 is, for example, a copper alloy, etc. The constituent material of the bolts 52, 62 is, for example, stainless steel, etc.

[0068] <Second metal fitting> The second fitting 6 is used to secure the porcelain tube 3 to the GIS case 9 as described above. The second fitting 6 in this example includes a flange fitting 60 as shown in FIG. 2. The flange fitting 60 is an annular plate-shaped member. The flange fitting 60 is disposed so as to contact the second surface 32 of the porcelain tube 3, and is secured to the GIS case 9 by bolts 62.

[0069] The width of the flange fitting 60 is the size along the radial direction of the flange fitting 60, and is the difference between the outer diameter and the inner diameter of the flange fitting 60. In this example, the width of the flange fitting 60 is larger than the size along the radial direction of the porcelain tube 3 at the second surface 32 of the porcelain tube 3. Therefore, the end face on the tip side of the flange fitting 60 can reliably come into contact with the second surface 32.

[0070] (Building procedure) The power cable termination structure 1 of the first embodiment can be constructed in the same manner as known procedures, and therefore a detailed description thereof will be omitted.

[0071] (Action and effect) In the power cable termination structure 1 of the first embodiment, the porcelain tube 3 has a specific third surface 33. Therefore, the insulation distance between the first metal fitting 5 and the second metal fitting 6 is the length along the surface of the tubular portion 330 of the porcelain tube 3. Specifically, the insulation distance is the total value of the protruding length L1, the protruding length L2, and the length L3. In contrast, the insulation distance of the conventional structure described above corresponds to only the protruding length L2. Therefore, the insulation distance in the power cable termination structure 1 of the first embodiment is longer than that of the conventional structure. In addition, the insulation distance between the shielding layer 23 electrically connected to the first metal fitting 5 and the second metal fitting 6 is longer than that of the conventional structure. In this respect, the power cable termination structure 1 including the porcelain tube 3 of the first embodiment has a higher insulation strength than the conventional structure. The porcelain tube 3 of the first embodiment has a specific third surface 33, so that the power cable termination structure 1 having a higher insulation strength than the conventional structure can be constructed as described above.

[0072] Furthermore, the power cable termination structure 1 of embodiment 1 and the porcelain tube 3 of embodiment 1 provide the following effects. (1) The shape of the porcelain tube 3 is simple. Therefore, the porcelain tube 3 is easy to manufacture. (2) The tubular portion 330 of the porcelain tube 3 is cylindrical and the third surface 33 is a flat surface. Therefore, by designing the length of the tubular portion 330 of the porcelain tube 3 to be somewhat long in advance during the manufacturing stage, the length of the tubular portion 330 can be easily adjusted. As a result, the insulation distance between the first metal fitting 5 and the second metal fitting 6 can be easily adjusted. (3) The tip end portion of the first fitting 5 is disposed inside the tubular portion 330 of the porcelain tube 3. Therefore, the tubular portion 330 protects the first fitting 5 mechanically and from the external environment. (4) The size of the first surface 31 and the second surface 32 of the porcelain tube 3 in the radial direction of the porcelain tube 3 is not too large. In this respect, the porcelain tube 3 and the power cable termination structure 1 can be easily made compact.

[0073] (5) The first surface 31 and the second surface 32 are disposed at the same position in the longitudinal direction of the porcelain tube 3, which provides the following effects. (5-1) As described above, the cylindrical portion 330 of the porcelain tube 3 can ensure a long insulation distance between the first metal fitting 5 and the second metal fitting 6. (5-2) Compared with the case where the first surface 31 and the second surface 32 are misaligned in the longitudinal direction, the following effects (a) to (c) are achieved. (a) The length of the tube portion 330 can be easily adjusted. (b) The portion of the first fitting 5 that is disposed on the inside, that is, the portion protected by the cylindrical portion 330, tends to become large. (c) A large internal space is ensured in the tubular portion 330. This allows the length of the pressing fitting 8 to be shortened. As a result, the length along the longitudinal direction of the power cable termination structure 1 can be made shorter than the length in the conventional structure described above. In this respect, the power cable termination structure 1 is compact. Furthermore, the short length of the pressing fitting 8 also reduces the manufacturing cost of the pressing fitting 8.

[0074] The effect (c) will be described in detail. The large internal space allows the portion of the pressing fitting 8 that is located on the root side of the terminal portion 2 of the power cable to be located inside the tubular portion 330. In this case, the length of the pressing fitting 8 can be made shorter than that of the pressing fitting provided in the conventional structure described above. In this example, the length of the shaft fitting 82, the length of the spring 83, the length of the guide rod 84, and the length of the bolt 85 can be made shorter. In this example, the use of the stud bolt 820 also allows the length of the shaft fitting 82 to be made shorter. In contrast, in the pressing fitting provided in the conventional structure described above, the shaft fitting and the like are located closer to the root side of the power cable than the insulating porcelain tube described above. Therefore, the length of the shaft fitting and the like in the conventional structure described above is likely to be longer than the above-mentioned length of the shaft fitting 82 and the like.

[0075] [Variations] At least one of the following modifications is possible for the power cable termination structure 1 of the first embodiment and the porcelain tube 3 of the first embodiment. (Variation 1) (1) The tubular portion 330 of the porcelain tube 3 has a shape other than a cylindrical shape. For example, at least one of the inner peripheral surface and the outer peripheral surface of the cylindrical portion is not a cylindrical surface. As a specific example, the outer shape of the cylindrical portion is a frustum shape, and the cross-sectional shape of the cylindrical portion is a trapezoid rather than a rectangle. (2) The third surface 33 of the porcelain tube 3 is an inclined surface. Specifically, the third surface 33 is not a plane parallel to the radial direction of the porcelain tube 3 but is a plane provided so as to intersect with the radial direction. Alternatively, the third surface 33 is a curved surface. In the first modification, the insulation distance between the first metal fitting 5 and the second metal fitting 6 is longer than the insulation distance in the first embodiment. Therefore, the first modification has a better insulation strength than the first embodiment. To mold the porcelain tube in the first modification, (1) uses, for example, a plurality of split dies that can be split in the radial direction of the porcelain tube. In (2), for example, a die for molding the third surface is used.

[0076] (Variation 2) The first surface 31 and the second surface 32 of the porcelain tube 3 are arranged to be offset in the longitudinal direction of the porcelain tube 3. Also, the root side portion of the pressing fitting 8 is not arranged inside the tubular portion 330 of the porcelain tube 3, but is arranged closer to the root than the third surface 33 of the porcelain tube 3. For example, the first surface 31 or the second surface 32 is arranged lower in FIG. 2 than the position shown in FIG. 2. As a specific example, the first surface 31 is arranged between the second surface 32 and the third surface 33. In this arrangement, the root side portion of the pressing fitting 8 is arranged closer to the root than the third surface 33. In the second modification, although the shaft fitting is longer, the size of the porcelain tube 3 along the radial direction is likely to be smaller than that of the first embodiment.

[0077] [Test example] The insulation performance of the termination structure of the power cable having a porcelain insulator was evaluated by the following three tests. The power cable termination structure of Sample No. 1 includes the porcelain bushing 3 of the first embodiment described above. In the DC withstand voltage test, a DC voltage of 25 kV was applied to the shielding layer of the power cable for one minute, and an evaluation was made as to whether or not an abnormality occurred in the cylindrical portion 330 of the porcelain tube 3. In the lightning impulse withstand voltage test, a positive impulse voltage was applied 10 times to the power cable, and then a negative impulse voltage was applied 10 times to evaluate whether or not an abnormality occurred in the tubular portion 330. The applied voltage was ±72.5 kV. In the lightning impulse breakdown test, an impulse voltage was applied to the power cable, and the impulse voltage at which a flashover occurred on the surface of the shielding layer was measured.

[0078] As a result, no abnormalities were found in the DC withstand voltage test and the lightning impulse withstand voltage test for sample No. 1, and good results were obtained. In the lightning impulse breakdown test, the impulse voltage of sample No. 1 was large enough for practical use, and good results were obtained. These findings indicate that sample No. 1 has excellent insulation strength. [Explanation of symbols]

[0079] 1 Power cable termination structure, 2 Power cable terminal 3 porcelain tube, 4 stress cone, 5 first metal fitting, 6 second metal fitting 8 Press fitting, 9 GIS case 20 conductor, 21 insulating layer, 22 outer semiconductive layer 23 Shielding layer, 24 Sheath 31 first page, 32 second page, 33 third page 34 first end, 35 second end 38 first electrode section, 39 second electrode section 41 insulating tube portion, 42 semiconductive portion 50 flange bracket, 51 main body, 52 bolt 60 flange bracket, 62 bolt 80 flange fitting, 81 ring part, 82 shaft fitting, 83 spring 84 Guide rod, 85 Bolt 200 Compression Sleeve 320 flange portion, 330 tube portion, 332 inner peripheral surface 352 Inner surface, 390 End 500 waterproof layer 820 Stud bolt L1, L2 protrusion length, L3 length

Claims

1. an end portion of a power cable having a conductor, an insulating layer, an outer semiconducting layer, and a shielding layer in this order from the inside; a stress cone covering an end of the outer semiconductive layer exposed from the shielding layer and an end of the insulating layer exposed from the outer semiconductive layer; a porcelain tube covering a tip end portion of the terminal portion of the power cable and the stress cone; A first fitting for covering a base side portion of the terminal portion of the power cable; a second electrode portion embedded in a portion of the porcelain bushing disposed on the base side, The porcelain tube has a plurality of end faces arranged to face the base side, The plurality of end surfaces are A first surface to which a tip portion of the first fitting is attached; a second surface to which a second metal fitting for fixing the porcelain tube to a predetermined object is attached; and a third surface disposed between the first surface and the second surface such that the first fitting and the second fitting are disposed apart from each other in a radial direction of the porcelain tube, the third surface is disposed closer to the root side than the first surface and the second surface, the second electrode portion extends from the first surface toward the tip side and is electrically connected to the first metal fitting, The stress cone has an insulating cylindrical portion and a semiconducting portion integrally provided on the base side of the insulating cylindrical portion, The stress cone has a spindle-shaped outer shape, the insulating tube portion has an inner circumferential surface in contact with an end portion of the insulating layer and an outer circumferential surface including an inclined surface tapering toward the tip side, the semiconductive portion has a shape that spreads from the base side in contact with an end of the outer semiconductive layer toward the tip side, a tip end of the semiconductive portion is located on the inner peripheral side of the inclined surface, a tip of the second electrode portion is located closer to the base than a tip of the semiconductive portion; Power cable termination structure.

2. The porcelain tube includes a cylindrical tube portion extending toward the base side beyond the first surface and the second surface, The power cable termination structure according to claim 1 , wherein the third surface is an end surface of the tubular portion.

3. The power cable termination structure according to claim 2 , wherein the first surface and the second surface are disposed at the same position in a longitudinal direction of the porcelain tube.

4. A pressing tool for pressing the stress cone from the base side toward the tip side, The first metal fitting is electrically connected to the shielding layer, 4. The power cable termination structure according to claim 3, wherein the portion of the pressing fitting arranged on the base side is connected to the tip end of the first fitting and is arranged inside the tubular portion.

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