JP4897952B2 - DC coaxial cable connection for power - Google Patents

Description

  The present invention relates to a connecting portion of a power DC coaxial cable having a return conductor coaxially with a central main conductor, and more particularly to a connecting portion of a power DC coaxial cable having a different return conductor cross-sectional area.

  FIG. 6 shows an example of a direct current coaxial cable for power. This DC coaxial cable has a main conductor 1 in the center, and an outer side of the inner semiconductive layer 2, a main insulating layer 3, an outer semiconductive layer 4, a return conductor 5, a return inner semiconductive layer 6, and a return insulating layer. 7, a return external semiconductive layer 8, a lead coating 9, and an anticorrosion layer 10 are sequentially provided coaxially (see FIG. 1 of Patent Document 1).

  The return conductor 5 is formed by concentrically twisting a large number of return conductor strands (copper wires) around the outer periphery of the outer semiconductive layer 4. There are two ways of twisting the return conductor element: one-way twisting in which the twisting direction does not change and SZ twisting (see FIG. 2 of Patent Document 1) in which the twisting direction is reversed at a constant pitch.

  The cross-sectional area of the main conductor and return conductor of the DC coaxial cable for power is designed according to the environment where the cable is laid, and when the rated current is passed through the main conductor and return conductor, For example 90 ° C) and the maximum allowable temperature of the return conductor (eg 75 ° C).

  The connection part of the DC coaxial cable consists of a main conductor connection part at the center of the connection part, a reinforcing main insulator that connects the cable main insulation layers on the outside, a return conductor connection part on the outside, and a cable return insulation layer on the outside. It is composed of a reinforced return insulator to be connected, a metal jacket connecting portion on the outside thereof, and the like.

JP 11-1111071 A

  The reinforcing main insulator and the reinforcing return insulator of the connection part are formed thicker than the main insulating layer and the return insulating layer of the cable part, respectively. For this reason, the thermal resistance in the radial direction at the DC coaxial cable connecting portion is larger than the thermal resistance in the radial direction at the cable portion. For example, a factory joint (FJ) in which DC coaxial cables are finished to have the same diameter (quasi-same diameter) as that of the cable part has almost the same structure as the cable part, but it is still in the radial direction of the connection part. The thermal resistance is larger than that of the cable portion.

  Further, when a metal or plastic connection pipe (or protective pipe) is provided on the outside of the DC coaxial cable connection portion, it is usually used for waterproofing between the cable return insulation layer and the reinforced return insulation and the connection pipe ( Or an insulating compound). In the connection portion having such a configuration, the thermal resistance in the radial direction is further increased.

  In DC coaxial cables, the rated current flows in the return conductor in addition to the main conductor, so both the main conductor and the return conductor serve as heat sources, and the increase in radial thermal resistance at the DC coaxial cable connection is It becomes the factor which raises the temperature rise of.

  Furthermore, in the connection of the DC coaxial cable, there is a case where a DC coaxial cable having a different structure is connected in addition to the case where the DC coaxial cable having the same structure is connected as in the connection part in the factory. For example, a submarine DC coaxial cable laid on the seabed and a land DC coaxial cable laid on land have different installation environments, and therefore have different main conductor cross-sectional areas and return conductor cross-sectional areas. When such a submarine DC coaxial cable and a land-use DC coaxial cable are connected (usually called a dredging connection because they are connected by dredging), the amount of heat generated by the main conductor and the return conductor in the connecting portion is in the longitudinal direction of the connection. However, the amount of heat generated is larger on the cable side having the smaller main conductor cross-sectional area and return conductor cross-sectional area. For this reason, there is a concern that an increase in the thermal resistance in the radial direction at the DC coaxial cable connecting portion may cause a significant temperature increase in the connecting portion.

  An object of the present invention is to suppress a temperature rise at a connection portion of a power DC coaxial cable, and particularly to suppress a temperature rise at a connection portion of a power DC coaxial cable having a different cross-sectional area of a return conductor. .

  To achieve this object, according to the present invention, in the connecting portion of the power DC coaxial cable having a different cross-sectional area of the return conductor, the return conductor of the cable having the larger return conductor cross-sectional area extends around the outer periphery of the reinforcing main insulator of the connecting portion. The connecting portions of the return conductors of both cables are positioned on the outer periphery of the outer semiconductive layer of the cable having the smaller return conductor cross-sectional area.

  In the above invention, it is preferable to provide a thermal buffer layer between the outer semiconductive layer of the cable having the smaller return conductor cross-sectional area and the connection portion of the return conductors of both cables.

  In order to achieve the above object, the present invention provides a return conductor and a return path of a cable having a smaller return conductor cross-sectional area (hereinafter referred to as a first cable) in a connecting portion of a power DC coaxial cable having a different return conductor cross-sectional area. A return conductor of a cable having a larger conductor cross-sectional area (hereinafter referred to as a second cable) is connected via a relay conductor having a cross-sectional area equal to or larger than the return conductor cross-sectional area of the second cable. The connecting portion is disposed so as to pass through the outer periphery of the reinforcing main insulator, and the connecting portion between the return conductor and the relay conductor of the first cable is located on the outer periphery of the outer semiconductive layer of the first cable, A connection portion between the return conductor and the intermediate conductor of the cable may be located on the outer periphery of the outer semiconductive layer of the second cable.

  In the above invention, a thermal buffer layer is provided between the connection between the return conductor and the relay conductor of the first cable and the outer semiconductive layer of the first cable, and the return conductor and the relay of the second cable are provided. Preferably, a thermal buffer layer is provided between the connection with the conductor and the outer semiconductive layer of the second cable.

  According to the present invention, since the cross-sectional area of the return conductor is large (the return conductor resistance is small) in most of the longitudinal direction of the DC coaxial cable connection portion, the amount of heat generated by energization of the return conductor in the connection portion is reduced. And the temperature rise of a connection part can be suppressed. In addition, when the said thermal buffer layer is provided, it can prevent that the external semiconductive layer and main insulation layer of a cable are damaged by the heat | fever at the time of welding a conductor, and the mistake at the time of a connection operation.

  [Embodiment 1] FIG. 1 shows an embodiment of a DC power cable connecting portion for power according to the present invention. The direct current coaxial cables A and B to be connected are respectively stripped of the anticorrosion layer 10, the lead sheath 9, and the return insulation layer 7 (the inner and outer semiconductive layers are not shown) in order to expose the return conductor 5, and further to the outside The semiconductive layer 4, the main insulating layer 3, and the internal semiconductive layer (not shown) are sequentially stripped to expose the main conductor 1 at the tip. The cross-sectional area of the return conductor 5 of one DC coaxial cable A is smaller than the cross-sectional area of the return conductor 5 of the other DC coaxial cable B. Hereinafter, the DC coaxial cable A having a smaller cross-sectional area of the return conductor 5 is referred to as a first cable A, and the DC coaxial cable B having a larger cross-sectional area is referred to as a second cable B.

  The main conductor 1 of the first cable A and the main conductor 1 of the second cable B are compression-connected by a different diameter conductor connecting sleeve 21. Reference numeral 22 denotes a reinforcing main insulator formed so as to straddle the sleeve 21 and the main insulating layers 3 and 3 of the cables A and B on both sides thereof, and 23 denotes heat provided on the outer semiconductive layer 4 of the first cable A. Buffer layer.

  The return conductor 5 of the second cable B passes through the outer periphery of the reinforcing main insulator 22 and reaches the thermal buffer layer 23, and is welded to the return conductor 5 of the first cable A on the thermal buffer layer 23. It is connected. Reference numeral 24 denotes the weld connection.

  The thermal buffer layer 23 prevents the outer semiconductive layer 4 and the main insulating layer 3 of the first cable A from being damaged by the heat generated during the return conductor welding. The thermal buffer layer 23 is formed by winding up the semiconductive cushion tape from the external semiconductive layer 4 to the external semiconductive layer (not shown) of the connecting portion so that the outer diameter is substantially the same as that of the reinforcing main insulator. It is preferable to form. The thermal buffer layer 23 is also useful for preventing the outer semiconductive layer 4 and the main insulating layer 3 of the first cable A from being damaged during the return conductor welding operation.

  When the return conductor 5 is connected by welding, the return conductor strands may be welded one by one, or a plurality of return conductor strands may be bundled and the bundles may be welded together. If the bundles are welded together, the number of times of welding can be reduced, and the welding operation can be performed efficiently.

  After the return conductor 5 is welded and connected as described above, the reinforced return insulator 25 is formed so as to straddle the return insulation layer 7 of both cables, and the lead coating 26 and the anticorrosion layer 27 may be provided. A return internal semiconductive layer of the connecting portion is provided inside the reinforced return insulator 25 so as to straddle the return internal semiconductive layer of both cables, and the return paths of both cables are provided outside the reinforced return insulator 25. A return external semiconductive layer of the connecting portion is provided so as to straddle the external semiconductive layer, but the illustration is omitted.

  In the connecting portion of the DC coaxial cable configured as described above, the cross-sectional area of the return conductor becomes large (the return conductor resistance becomes small) in most of the longitudinal direction of the connecting portion, so that the return conductor 5 in the connecting portion The amount of heat generated by energization can be suppressed to a low level, and therefore the temperature rise of the connecting portion can be suppressed.

A more specific configuration of the power direct-current coaxial cable connecting portion shown in FIG. 1 will be described as follows. The first cable A has, for example, a main conductor cross-sectional area of 400 mm ² and a return conductor cross-sectional area of 215 mm ² (copper strand φ2.6 mm × 55 concentric strands), and the second cable B has a main conductor cross-sectional area of 500 mm, for example. ^2. Return conductor cross-sectional area of 463 mm ² (copper element wire φ5.0 mm × 30 concentric strands). The main conductor 1 of both cables A and B is a copper twisted wire, the main insulating layer 3 is a crosslinked polyethylene, and the return insulating layer 7 is a non-crosslinked polyethylene. The reinforcing main insulator 22 is formed by heat molding after winding the insulating tape. The thermal buffer layer 23 is formed by winding a semiconductive cushion tape and has a thickness of about 13 mm. The return conductors 5 and 5 of both the cables A and B are butt welded for each of the plurality of return conductor strands, and the number of welded portions of the return conductor strands is 13. The configuration of the return conductor strand of the first cable A is 4 sets of φ2.6 mm × 5 bundles, 8 sets of φ2.6 mm × 4 bundles, and 1 set of φ2.6 mm × 3 bundles. The configuration of the return conductor strand bundle of the second cable B is 4 sets of φ5.0 mm × 3 bundles and 9 sets of φ5.0 mm × 2 bundles. The combinations of return conductor bundles to be welded are 4 combinations of φ2.6 mm × 5 bundles and φ5.0 mm × 3 bundles, and 8 combinations of φ2.6 mm × 4 bundles and φ5.0 mm × 2 bundles. The combination of the location, φ2.6 mm × 3 bundle and φ5.0 mm × 2 bundle is one location.

  In the above configuration, the connection portion of the return conductor is positioned on the outer periphery of the outer semiconductive layer of the first cable A (the embodiment of the present invention), and the outer periphery of the outer semiconductive layer of the second cable B. 2 (a) and 2 (b) show the results of calculating the main conductor temperature distribution and the return conductor temperature distribution when the main conductor and the return conductor are each energized with 700A for the case (comparative example). Show. According to this calculation result, the temperature reached by the main conductor in the DC coaxial cable connection portion was about 70 ° C. (FIG. 2a) in the example of the present invention, and about 80 ° C. (FIG. 2b) in the comparative example. As described above, according to the present invention, the amount of heat generated by energization of the return conductor in the connecting portion can be suppressed to a small value, so that it is understood that the main conductor temperature rise can be reduced by about 10 ° C.

  [Embodiment 2] FIG. 3 shows another embodiment of the present invention. In this DC coaxial cable connecting portion, the return conductor 5 of the first cable A having the smaller return conductor cross-sectional area and the return conductor 5 of the second cable B having the larger return conductor cross-sectional area are connected to the relay conductor 28. Connected through. The relay conductor 28 is made of a copper wire like the return conductor 5, and its cross-sectional area is set to be equal to or larger than the return conductor cross-sectional area of the second cable B. The relay conductor 28 is disposed so as to pass through the outer periphery of the reinforcing main insulator 22 of the connection portion, whereby the connection portion 24A between the return conductor 5 of the first cable A and the relay conductor 28 is connected to the first cable. A connection portion 24B between the return conductor 5 and the relay conductor 28 of the second cable B is positioned on the outer periphery of the outer semiconductive layer 4 of the second cable B. . A thermal buffer layer 23 is provided on each of the outer semiconductive layers 4 of the cables A and B, and the connection portions 24A and 24B of the return conductor 5 and the relay conductor 28 are located on these thermal buffer layers 23. is doing. As in the first embodiment, the return conductor and the relay conductor are preferably connected by bundling a plurality of conductor strands and butting the conductor strand bundles together.

  Since the configuration other than the above is the same as that of the first embodiment, the same portions are denoted by the same reference numerals and description thereof is omitted. Even with such a configuration, the same effect as in the first embodiment can be obtained. Further, if the cross-sectional area of the intermediate conductor 28 is made larger than the cross-sectional area of the return conductor 5 of the second cable B, the temperature rise of the connecting portion can be further suppressed to be lower than that of the first embodiment.

  [Third Embodiment] FIG. 4 shows still another embodiment of the present invention. The DC coaxial cable connection portion is different from the first embodiment in that the thermal buffer layer is omitted, and the weld connection portion 24 of the return conductor 5 of both cables A and B is connected to the outer semiconductive layer 4 of the first cable A. It is located above. If the return conductor 5 is welded carefully, such a configuration is possible. Since the other configuration is the same as that of the first embodiment, the same portions are denoted by the same reference numerals and the description thereof is omitted.

[ Related Art 1 ] FIG. 5 shows a related art of the present invention. This related technology is different from the second embodiment shown in FIG. 3 in that cables A having the same cross-sectional area of the return conductor 5 are connected to each other. The intermediate conductor 28 has a larger cross-sectional area than the return conductor 5. Since the other configuration is the same as that of the second embodiment, the same portions are denoted by the same reference numerals and the description thereof is omitted. According to this related technique , the temperature rise of the cable connecting portion can be suppressed as compared with the case where the return conductors 5 are connected.

1 shows an embodiment of a power direct-current coaxial cable connecting portion according to the present invention, (a) is a longitudinal sectional view, (b) is a partially cut plan view. (A) is a graph which shows the temperature distribution of the Example of this invention, (b) is a graph which shows the temperature distribution of the comparative example of this invention. The other embodiment of this invention is shown, (a) is a longitudinal cross-sectional view, (b) is a partially cutaway plan view. The longitudinal cross-sectional view which shows other embodiment of this invention. The longitudinal cross-sectional view which shows the related technique of this invention. The cross-sectional view which shows an example of the direct current | flow coaxial cable for electric power.

Explanation of symbols

A, B: DC coaxial cable for power 1: Main conductor 3: Main insulating layer 4: External semiconductive layer 5: Return conductor 7: Return insulating layer 21: Different diameter conductor connection sleeve 22: Reinforced main insulator 23: Heat Buffer layer 24, 24A, 24B: welded connection 25: reinforced return insulator 28: relay conductor

Claims (2)

  In the connection part of the DC coaxial cable for power with different return conductor cross-sectional areas, the return conductor of the cable with the larger return conductor cross-sectional area is arranged so that it passes through the outer periphery of the reinforcing main insulator of the connection part. The connection portion of the return DC conductor is located on the outer periphery of the outer semiconductive layer of the cable having the smaller return conductor cross-sectional area.   In the connection portion of the DC coaxial cable for power with different return conductor cross sections, the return conductor of the cable with the smaller return conductor cross section (hereinafter referred to as the first cable) and the cable with the larger return conductor cross section (hereinafter referred to as the first conductor) And a return conductor of the second cable) via a relay conductor having a cross-sectional area greater than or equal to the return conductor cross-sectional area of the second cable, and this relay conductor passes through the outer periphery of the reinforcing main insulator of the connecting portion. The connection portion between the return conductor and the relay conductor of the first cable is located on the outer periphery of the outer semiconductive layer of the first cable, and the connection portion between the return conductor and the relay conductor of the second cable. Is located on the outer periphery of the outer semiconductive layer of the second cable.

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