JP2009044864A - Heat shrinkage insulating tube with internal semiconductive layer, and power dc coaxial cable connecting section using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a connecting section of a power DC coaxial cable which has a small outside diameter increase in a connecting section, can be manufactured readily and has little defects. <P>SOLUTION: Two heat-shrinkage insulating tubes 11 with internal semiconductive layers are installed in series on the external side of exposure sections S of return conductors 5 so as to make them subjected to heat-shrinking. Internal semiconductive layers 12 and 12 of the tubes are connected and insulating layers 13 and 13 of the tubes are connected, in a part where the ends of the heat-shrinkable tubes 11 are confronted. The internal semiconductive layers 12 of the tubes and return internal semiconductive layers 6 of both cables are connected, and the insulating layers 13 of the tubes and return insulating layers 7 of both cables are connected, at a part where the ends of the heat-shrunk tubes 11 are confronted with the ends of the return internal semiconductive layers 6 and the return insulating layers 7 of the cables. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heat-shrinkable insulating tube with an internal semiconductive layer and a connecting portion of a power direct-current coaxial cable using the same.

  A DC coaxial cable for electric power generally has a structure as shown in FIG. That is, it has a main conductor 1 at the center and a main conductor semiconductive layer 2, a main insulating layer 3, and a main outer semiconductive layer 4 on the outer side of the return conductor (also called a neutral conductor or an outer conductor) 5 in this order. And a lead coating 9 is provided on the outer side through the return inner semiconductive layer 6, the return insulating layer 7, and the return outer semiconductive layer 8 in this order, and the anticorrosion layer 10 made of polyethylene or the like is provided on the outer side. (See Patent Document 1). When the power DC coaxial cable is used as a submarine cable, a floor, an iron wire armor, and a serving layer are further provided outside the anticorrosion layer 10.

  The return conductor 5 is formed by concentrically twisting a large number of return conductor strands 5a. The main insulating layer 3 is formed of crosslinked polyethylene, and the return insulating layer 7 is formed of non-crosslinked polyethylene. The return insulating layer 7 is thinner than the main insulating layer 3. The main inner semiconductive layer 2 and the main outer semiconductive layer 4 are formed by co-extrusion with the main insulating layer 3 or the like, and the return inner semiconductive layer 6 and the return outer semiconductive layer 8 are formed by semiconductive tape winding or the like. The

  Power DC coaxial cables are often used as long-distance submarine cables as interconnection lines. However, since the length of cables that can be manufactured continuously at the factory is limited, DC cables for long distances can be manufactured by manufacturing multiple cables that can be manufactured at the factory and connecting these cables. Is manufacturing. A connection between DC coaxial cables manufactured at a factory is generally called a factory joint. This factory joint is required to keep the outer diameter as small as possible (connect with an outer diameter close to the cable outer diameter) so that it can handle the bending that occurs when loading and unloading from the laying ship. The

  When connecting a DC coaxial cable, connect the main conductor at the center, then connect the main internal semiconductive layer, connect the main insulating layer, connect the main external semiconductive layer, connect the return conductor, and return the internal semiconductive Layer connection, return insulation layer connection, return external semiconductive layer connection, lead coat connection, and anticorrosion layer connection are sequentially performed. In order to keep the outer diameter of the connection portion small, the main conductors are connected by butt welding, and the return conductors are connected by strand butt welding, strand circumferential welding or strand split welding. Further, a normal CV cable connection technique can be applied to the formation of the main internal semiconductive layer, the main insulating layer, and the main external semiconductive layer in the connection portion. In addition, it has been proposed that the formation of the return inner semiconductive layer and the return insulating layer of the connecting portion is performed by the TJ method (insulating rubber tape winding insulation) or the TMJ method (polyethylene tape winding mold insulation) (Non-Patent Document 1, Non-patent document 2).

Japanese Patent Laid-Open No. 11-12083 Paper-EC-00-21 "Development of DC coaxial cable" published in 2000 Cable Technology Research Group Papers published in 2002-139, Annual Conference of the Institute of Electrical Engineers of Japan “Small Capacity DC Coaxial XLPE Cable and Factory Joint”

  However, when the required performance of the DC coaxial cable for power becomes high, in the TJ system, when the high insulation performance is required, the return insulation layer of the connection portion becomes thick due to the insulation performance. The outer diameter becomes considerably larger than the outer diameter of the cable return insulation layer, and it is difficult to keep the outer diameter of the cable connection portion small.

  Further, when the return insulating layer of the connection portion is formed by the TMJ method, the outer diameter of the connection portion can be reduced because the insulation performance is superior to that of the TJ method, but there are the following problems. That is, since the connection of the return conductor of the power DC coaxial cable is performed after the main outer semiconductive layers of the cables are connected to each other, the section where the return conductor is exposed becomes long. As a result, in the case of the TMJ method, the semiconductive tape and the insulating tape are wound over a wide range (for example, 1.6 m), and each is pressed and heated to be molded, so it is difficult to control the temperature during heating. In addition, it is difficult to suppress the generation of defects (protrusions / deformation, foreign matter, voids) and stabilize the quality throughout the molded product.

  An object of the present invention is to provide a heat-shrinkable insulating tube with an internal semiconductive layer suitable for connecting a return internal semiconductive layer and a return insulating layer of a direct current coaxial cable for power, and a small increase in the outer diameter of a connecting portion using the same. An object of the present invention is to provide a power direct current coaxial cable connection that is easy to manufacture and has few defects.

  The heat-shrinkable insulating tube with an internal semiconductive layer according to the present invention includes an internal semiconductive layer that is heat-shrinkable in the radial direction by wrapping a uniaxially stretched semiconductive film or tape in multiple layers so that the extending direction is in the circumferential direction. It is formed to a required thickness, and a uniaxially stretched insulating film or tape is wound in multiple layers so that the extending direction thereof is in the circumferential direction, and an insulating layer capable of heat shrinking in the radial direction is formed to the required thickness. It is what.

The connecting portion of the power direct-current coaxial cable according to the present invention has a main conductor at the center, a main inner semiconductive layer, a main insulating layer, and a main outer semiconductive layer in order on the outer side, and on the outer side. It has a return conductor formed by concentrically twisting a number of return conductor strands, and is a connection part between the DC coaxial cables for power having a return inner semiconductive layer and a return insulating layer in order on the outside thereof,
After connecting the main conductors of both cables, the main inner semiconductive layers, the main insulating layers, the main outer semiconductive layers, and the return conductors,
A heat-shrinkable insulating tube with an inner semiconductive layer according to claim 1 is placed on the outside of the return conductor exposed section to heat-shrink,
At the part where the end of the heat-shrinkable tube and the end of the cable return inner semiconductive layer and the end of the return insulation layer meet, the inner semiconductive layer of the tube and the cable return inner semiconductive layer are connected. And connecting the insulating layer of the tube and the return insulating layer of the cable,
It is characterized by this.

In addition, the connecting portion of the above-described power direct-current coaxial cable according to the present invention is:
Both ends of the heat-shrinkable tube and the ends of the return inner semiconductive layer and the return insulating layer of both cables are formed in a tapered shape in which the outer diameter gradually decreases,
The connection portion between the inner semiconductive layer of the tube and the return inner semiconductive layer of the cable and the connection portion between the insulating layer of the tube and the return insulating layer of the cable each fill a V-shaped recess between the tapered shapes. Thus, it is preferably formed by a tape winding mold.

The connecting portion of the power direct-current coaxial cable according to the present invention has a main conductor at the center, a main inner semiconductive layer, a main insulating layer, and a main outer semiconductive layer in order on the outer side, and on the outer side. It has a return conductor formed by concentrically twisting a number of return conductor strands, and is a connection part between the DC coaxial cables for power having a return inner semiconductive layer and a return insulating layer in order on the outside thereof,
After connecting the main conductors of both cables, the main inner semiconductive layers, the main insulating layers, the main outer semiconductive layers, and the return conductors,
On the outside of the return conductor exposed section, a plurality of heat-shrinkable insulating tubes with internal semiconductive layers according to claim 1 having a length shorter than the section are covered in series, and each is heat-shrinked,
At the part where the end and end of the heat-shrinkable tube meet, connecting the inner semiconductive layers of the tube, and connecting the insulating layers of the tube,
At the part where the end of the heat-shrinkable tube and the end of the cable return inner semiconductive layer and the end of the return insulation layer meet, the tube inner semiconductive layer and the cable return inner semiconductive layer are connected. And connecting the insulating layer of the tube and the return insulating layer of the cable,
It is preferable that it is characterized by this.

In addition, the connecting portion of the above-described power direct-current coaxial cable according to the present invention is:
Both ends of the heat-shrinkable tube and the ends of the return inner semiconductive layer and the return insulating layer of both cables are formed in a tapered shape in which the outer diameter gradually decreases,
The connecting portion between the inner semiconductive layers of the tube and the connecting portion between the insulating layers are each formed by a tape winding mold so as to fill a V-shaped recess between the tapered shapes,
The connection portion between the inner semiconductive layer of the tube and the return inner semiconductive layer of the cable and the connection portion between the insulating layer of the tube and the return insulating layer of the cable each fill a V-shaped recess between the tapered shapes. Thus, it is preferably formed by a tape winding mold.

  In addition, the connecting portion of each of the power DC coaxial cables according to the present invention is provided with a semiconductive tape winding layer outside the return conductor exposed section, and then heats the heat-shrinkable insulating tube with the internal semiconductive layer. A contracted configuration is preferable.

  In the heat-shrinkable insulating tube with an inner semiconductive layer provided by the invention of claim 1, the heat-shrinkable inner semiconductive layer is integrally provided on the inner side of the heat-shrinkable insulating tube. It is possible to form the return inner semiconductive layer and the return insulating layer of the connecting portion only by heating and shrinking. Therefore, compared to the case where the internal semiconductive layer and the insulating layer are formed by a tape winding mold method, the connection portion formation can be greatly simplified, the temperature control during heating is easy, and defects (projections / deformations, foreign matter, The generation factor of voids is small, and the quality of the connection portion can be stabilized.

  According to the invention of claim 2, since most of the return inner semiconductive layer and the return insulating layer of the connection portion are formed by the heat shrinkable insulating tube with the inner semiconductive layer thermally contracted, the return inner semiconductive in the TJ method. Compared with the case where the layer and the return insulation layer are formed, the thickness of the return insulation layer of the connection portion can be reduced, and an increase in the outer diameter of the connection portion can be suppressed. In addition, compared with the case where the return inner semiconductive layer and the return insulating layer are formed by the TMJ method, the formation of the connection portion can be greatly simplified, the temperature control during heating is easy, and defects (projections / deformations, foreign matters, The generation factor of voids is small, and the quality of the connection portion can be stabilized.

  According to the invention of claim 3, the connection between the inner semiconductive layer of the heat-shrinkable insulating tube with the heat-shrinkable inner semiconductive layer and the return inner semiconductive layer of the cable, and the insulation layer of the tube and the return insulation layer of the cable Can be connected easily and reliably in a short section. Therefore, the connection portion forming operation can be simplified.

  According to the invention of claim 4, a plurality of heat-shrinkable insulating tubes with internal semiconductive layers shorter in length than the return conductor exposed section are placed in series on the outside of the return conductor exposed section to heat-shrink each, Since the contracted tubes are connected to each other to cover the return conductor exposed section, the length of one heat-shrinkable insulating tube with an internal semiconductive layer can be shortened. Since the return conductor exposed section is considerably long as described above (for example, 1.6 m), if this section is covered with a single heat-shrinkable insulating tube with an inner semiconductive layer, a considerably long inner semiconductive layer is formed. A heat shrinkable insulation tube is required. However, from the viewpoint of manufacturing equipment and quality control of heat-shrinkable insulation tube with internal semiconductive layer, if the return conductor exposed section is long, cover the whole area with multiple heat-shrinkable insulation tubes with internal semiconductive layer Is one way. The effects other than the above are the same as in the invention of claim 2.

  Further, according to the invention of claim 5, the connection between the inner semiconductive layers and the connection between the insulating layers of the heat-shrinkable heat-shrinkable insulating tube with the inner semiconductive layer can be easily and reliably performed in a short section. it can. The effects other than the above are the same as those of the invention of claim 3.

  According to the invention of claim 6, since the inner semiconductive layer of the heat-shrinkable tube can be prevented from falling into the gap between the return conductor strands, the interface between the inner semiconductive layer and the insulating layer of the tube can be smoothed. And the quality of the connecting portion can be stabilized.

Embodiment 1 FIG. 1 shows an embodiment of a heat shrinkable insulating tube with an internal semiconductive layer according to the present invention. In this heat-shrinkable insulating tube 11 with an inner semiconductive layer, a cylindrical insulating layer 13 that can be heat-shrinkable in the radial direction is integrally formed on a cylindrical inner semiconductive layer 12 that is heat-shrinkable in the radial direction. Is.

  Such a heat-shrinkable insulating tube 11 with an internal semiconductive layer can be manufactured as shown in FIG. That is, a uniaxially stretched film (uniaxially stretched semiconductive film) made of a semiconductive material is wound on the mandrel 14 in a multilayer manner so that the stretch direction is in the circumferential direction, and heat shrinkable in the radial direction of the required thickness. The internal semiconductive layer 12 is formed, and a uniaxially stretched film (uniaxially stretched insulating film) 13a made of an insulating material is wound on the inner semiconductive layer 12 in a multilayered manner so that the stretching direction is in the circumferential direction. After the shrinkable insulating layer 13 is formed, the mandrel 14 can be drawn out. The widths of the uniaxially stretched semiconductive film and the uniaxially stretched insulating film are the same as the length of the heat-shrinkable insulating tube 11 with an internal semiconductive layer to be manufactured. The material of the uniaxially stretched semiconductive film and the material of the uniaxially stretched insulating film are, for example, polyolefin materials.

<Embodiment 2> FIG. 3 shows one embodiment of a power direct-current coaxial cable connecting portion according to the present invention using the heat-shrinkable insulating tube 11 with an inner semiconductive layer. Each of the DC coaxial cables 20A and 20B to be connected has a main conductor 1 at the center, and a main inner semiconductive layer 2, a main insulating layer 3, and a main outer semiconductive layer 4 are sequentially provided on the outer side, and a large number on the outer side. The return conductor 5 is formed by concentrically twisting the return conductor strand 5a, and the return inner semiconductive layer 6, the return insulating layer 7, the return outer semiconductive layer 8, the lead coating 9, and the anticorrosion layer 10 are sequentially provided on the outer side. It is a thing.

  The ends of both cables 20A and 20B are stripped, and the main conductors 1 and 1 are connected to each other by butt welding in order to suppress an increase in outer diameter. 21 is the welding connection part. Further, the main internal semiconductive layers 2 and 2 of both cables are connected by forming a connection main internal semiconductive layer 22 so as to straddle the ends of both cables, and the main insulating layers 3 and 3 are connected to the ends of both. The connection portion main insulating layer (reinforcing insulator) 23 is formed so as to straddle the portion, and the main outer semiconductive layers 4, 4 are connected to the connection portion outer semiconductive layer 24 so as to straddle both ends. Connected by forming. A well-known CV cable connection technique is applied as it is to the formation of the main inner semiconductive layer 22, the main insulating layer 23, and the main outer semiconductive layer 24 in the connection portion.

  Connection of the return conductors 5 and 5 of both the cables 20A and 20B is performed, for example, by butt welding the strands 5a in order to suppress an increase in outer diameter. Reference numeral 25 denotes the weld connection. Since the connection of the return conductors 5 and 5 is performed after the connection part external semiconductive layer 24 straddling the ends of the main external semiconductive layers 4 and 4 of the cable is formed, the exposed section S of the return conductors 5 and 5 is considerably large. become longer.

  In the present invention, in order to form the return inner semiconductive layer and the return insulating layer outside the long return conductor exposed section S, the heat shrinkable insulating tube 11 with the inner semiconductive layer shown in FIG. 1 is used. Point inner semiconducting layer with a thermally shrinkable insulating tube 11 it should be placed in the outside of the advance either cable 20A or 20B before performing the connection of the main body 1, 1, the end of the connection return conductor 5,5 To return to the return conductor exposed section S. In this way, the heat-shrinkable insulating tube 11 with the inner semiconductive layer placed on the outside of the return conductor exposed section S is heated and thermally contracted onto the return conductors 5 and 5. In this embodiment, the heat-shrinkable insulating tube 11 with the inner semiconductive layer has a length that covers almost the entire length of the return conductor exposed section S.

  At both ends of the heat-shrinkable tube 11, the inner semiconductive layer 12 of the tube 11 and the return inner semiconductive layer 6 of both cables 20A, 20B are connected, and the insulating layer 13 of the tube 11 and both cables 20A, 20B are connected. To the return insulating layer 7. These connections are made as follows. That is, both ends of the heat-shrinkable tube 11 and the ends of the return inner semiconductive layer 6 and the return insulating layer 7 of both cables 20A and 20B are respectively formed in a tapered shape whose outer diameter gradually decreases in advance. The semiconductive layer 12 and the return inner semiconductive layer 6 of the cable are connected by a semiconductive layer connecting portion 26 formed by tape winding so as to fill the bottom of the V-shaped recess between the tapered shapes, and the tube The insulating layer 13 of the cable and the return insulating layer 7 of the cable are connected by an insulating layer connecting portion 27 formed by tape winding so as to fill the V-shaped recess.

  Thus, when the connection between the return inner semiconductive layers 6 and 6 of both cables and the connection between the return insulation layers 7 and 7 are performed, compared to the case where the tape winding mold is applied to the entire length of the return conductor exposed section S, It is possible to stabilize the quality with few occurrences of defects, to suppress an increase in the outer diameter of the connection portion, and to shorten the connection time.

  Thereafter, the ends of the return external semiconductive layers 8 and 8 of both cables 20A and 20B are connected by forming the semiconductive tape winding layer 28, and the ends of the lead sheaths 9 and 9 are connected by the lead tube 29. The end portions of the anticorrosion layers 10 and 10 are connected by a heat shrinkable anticorrosion sleeve 30. These points are the same as before.

<Third Embodiment> FIG. 4 shows another embodiment of the power DC coaxial cable connecting portion according to the present invention. This embodiment is different from the second embodiment in that the return conductor exposed section S is covered with two heat-shrinkable insulating tubes 11 with an internal semiconductive layer having a length approximately half that of the section S in series. The heat shrinkage.

  Both ends of the heat-shrinkable tube 11 and the ends of the return inner semiconductive layer 6 and the return insulating layer 7 of both cables 20A and 20B are formed in a tapered shape with the outer diameter gradually decreasing. The inner semiconductive layers 12 of the two tubes 11 are connected to each other by an inner semiconductive layer connecting portion 31 formed by tape winding so as to fill the bottom of the V-shaped recess between the tapered shapes. The insulating layers 13 and 13 are connected to each other by an insulating layer connecting portion 32 formed by tape winding so as to fill the V-shaped concave portion.

  In addition, at both outer ends of the two tubes 11 and 11, the inner semiconductive layer 12 of the tube and the return inner semiconductive layer 6 of the cable form the bottom of the V-shaped recess between the tapered shapes. Connected by a semiconductive layer connection portion 26 formed by tape winding mold so as to fill, and the tube insulating layer 13 and the cable return insulating layer 7 are formed by tape winding mold so as to fill the V-shaped recess. The insulating layer connecting portion 27 is connected. This is the same as in the second embodiment.

  Since the configuration other than the above is the same as that of the second embodiment (FIG. 3), the same portions are denoted by the same reference numerals and description thereof is omitted.

  According to this embodiment, since the length of one heat-shrinkable insulating tube 11 with an inner semiconductive layer is almost half that of the second embodiment, the manufacturing equipment and quality of the heat-shrinkable insulating tube 11 with an inner semiconductive layer are sufficient. When there is a length restriction in terms of management, this is an effective return insulating layer formation method. The other effects are the same as those of the second embodiment.

<Embodiment 4> FIG. 5: shows further another Embodiment of the direct-current coaxial cable connection part for electric power which concerns on this invention. This embodiment is different from the third embodiment in that the heat conductive shrinkable insulating tube 11 with the internal semiconductive layer is thermally contracted after the semiconductive tape winding layer 33 is provided outside the return conductor exposed section S. That is. Since the other configuration is the same as that of the third embodiment (FIG. 4), the same portions are denoted by the same reference numerals and description thereof is omitted.

  According to this embodiment, since the semiconductive tape winding layer 33 is provided outside the return conductor exposed section S, when the heat-shrinkable insulating tube 11 with the internal semiconductive layer is thermally contracted, the inner half of the tube is exposed. The conductive layer 12 does not fall into the gap between the return conductor wires 5a. For this reason, the smoothness of the interface between the inner semiconductive layer 12 and the insulating layer 13 is improved, and the insulating performance can be improved. In addition, since the semiconductive tape winding layer 33 is in contact with the inner semiconductive layer 12 of the tube 11 on the entire surface, it is not necessary to mold, and it is easy to provide the semiconductive tape winding layer itself.

1A and 1B show an embodiment of a heat-shrinkable insulating tube with an internal semiconductive layer according to the present invention, in which FIG. Explanatory drawing which shows the method of manufacturing the heat-shrinkable insulation tube with an internal semiconductive layer of FIG. The longitudinal section showing one embodiment of the direct-current coaxial cable connection part for electric power concerning the present invention. The longitudinal cross-sectional view which shows other embodiment of the direct-current coaxial cable connection part for electric power which concerns on this invention. The longitudinal cross-sectional view which shows further another embodiment of the direct-current coaxial cable connection part for electric power which concerns on this invention. The cross-sectional view which shows an example of the direct current | flow coaxial cable for electric power.

Explanation of symbols

1: Main conductor 2: Main inner semiconductive layer 3: Main insulating layer 4: Main outer semiconductive layer 5: Return conductor 5a: Wire 6: Return inner semiconductive layer 7: Return insulating layer 8: Return outer semiconductive layer 9: lead coating 10: anticorrosion layer 11: heat shrinkable insulation tube with internal semiconductive layer 12: internal semiconductive layer 13: insulating layers 20A, 20B: DC coaxial cable for power 21: main conductor welded connection 22: main connection Internal semiconductive layer 23: Connection portion main insulation layer 24: Connection portion main external semiconductive layer 25: Wire welding connection portion 26: Return internal semiconductive layer connection portion 27: Return insulation layer connection portion 31: Semiconductive layer connection portion 32: Insulating layer connection part 33: Semiconductive tape winding layer

Claims (6)

  A uniaxially stretched semiconductive film or tape is wound in multiple layers so that the stretch direction is in the circumferential direction, and an internal semiconductive layer that can be thermally contracted in the radial direction is formed to a required thickness. A heat-shrinkable insulating tube with an internal semiconductive layer, wherein an insulating layer capable of heat-shrinking in a radial direction is formed in a required thickness by winding the tape in a multilayered manner so that the extending direction thereof is in the circumferential direction. It has a main conductor at the center, a main inner semiconductive layer, a main insulating layer, and a main outer semiconductive layer on the outside in that order, and a return conductor formed by concentrically twisting many return conductor wires on the outside. And a connecting portion between the DC coaxial cables for power having a return inner semiconductive layer and a return insulating layer sequentially on the outer side,
After connecting the main conductors of both cables, the main inner semiconductive layers, the main insulating layers, the main outer semiconductive layers, and the return conductors,
A heat-shrinkable insulating tube with an inner semiconductive layer according to claim 1 is placed on the outside of the return conductor exposed section to heat-shrink,
At the part where the end of the heat-shrinkable tube and the end of the cable return inner semiconductive layer and the end of the return insulation layer meet, the inner semiconductive layer of the tube and the cable return inner semiconductive layer are connected. And connecting the insulating layer of the tube and the return insulating layer of the cable,
The connection part of the direct current | flow coaxial cable for electric power characterized by the above-mentioned. Both ends of the heat-shrinkable tube and the ends of the return inner semiconductive layer and the return insulating layer of both cables are formed in a tapered shape in which the outer diameter gradually decreases,
The connection portion between the inner semiconductive layer of the tube and the return inner semiconductive layer of the cable and the connection portion between the insulating layer of the tube and the return insulating layer of the cable each fill a V-shaped recess between the tapered shapes. 3. The connecting portion of the power DC coaxial cable according to claim 2, wherein the connecting portion is formed by tape winding molding. It has a main conductor at the center, a main inner semiconductive layer, a main insulating layer, and a main outer semiconductive layer on the outside in that order, and a return conductor formed by concentrically twisting many return conductor wires on the outside. And a connecting portion between the DC coaxial cables for power having a return inner semiconductive layer and a return insulating layer sequentially on the outer side,
After connecting the main conductors of both cables, the main inner semiconductive layers, the main insulating layers, the main outer semiconductive layers, and the return conductors,
On the outside of the return conductor exposed section, a plurality of heat-shrinkable insulating tubes with internal semiconductive layers according to claim 1 having a length shorter than the section are covered in series, and each is heat-shrinked,
At the part where the end and end of the heat-shrinkable tube meet, connecting the inner semiconductive layers of the tube, and connecting the insulating layers of the tube,
At the part where the end of the heat-shrinkable tube and the end of the cable return inner semiconductive layer and the end of the return insulation layer meet, the tube inner semiconductive layer and the cable return inner semiconductive layer are connected. And connecting the insulating layer of the tube and the return insulating layer of the cable,
The connection part of the direct current | flow coaxial cable for electric power characterized by the above-mentioned. Both ends of the heat-shrinkable tube and the ends of the return inner semiconductive layer and the return insulating layer of both cables are formed in a tapered shape in which the outer diameter gradually decreases,
The connecting portion between the inner semiconductive layers of the tube and the connecting portion between the insulating layers are each formed by a tape winding mold so as to fill a V-shaped recess between the tapered shapes,
The connection portion between the inner semiconductive layer of the tube and the return inner semiconductive layer of the cable and the connection portion between the insulating layer of the tube and the return insulating layer of the cable each fill a V-shaped recess between the tapered shapes. Is formed by tape winding mold,
The connection part of the direct-current coaxial cable for electric power of Claim 4 characterized by the above-mentioned.   5. The heat-shrinkable insulating tube with an internal semiconductive layer is heat-shrinked after a semiconductive tape winding layer is provided outside the return conductor exposed section. Connection part of DC coaxial cable for electric power.

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