JP2024062001A - Cable connection structure, connecting power cable, and method for manufacturing cable connection structure - Google Patents

Abstract

To improve both electrical and mechanical properties of cable connection structures.SOLUTION: A cable connection structure has a pair of power cables each having a conductor, and a sleeve configured as a metal tube having a hollow section and connecting the conductors of the pair of power cables within the hollow section, the sleeve has a plurality of indents concave in the radial direction of the sleeve, and the space factor of the area occupied by the conductor to the cross-sectional area of the hollow section of the sleeve is 90% or more and less than 99% when looking at a cross-section perpendicular to the axial direction of the sleeve including at least one of a plurality of multiple indents.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to a cable connection structure, a connected power cable, and a method for manufacturing a cable connection structure.

When connecting a pair of power cables, the conductors may be connected by compressing a cylindrical sleeve (for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 11-41779

The objective of this disclosure is to improve both the electrical and mechanical properties of cable connection structures.

According to one aspect of the present disclosure,
a pair of power cables each having a conductor;
a sleeve configured as a metal tube having a hollow portion and connecting the conductors of the pair of power cables within the hollow portion;
having
The sleeve has a plurality of indentations recessed in a radial direction of the sleeve,
A cable connection structure is provided in which the space factor of the area occupied by the conductor relative to the cross-sectional area of the hollow portion of the sleeve is 90% or more and less than 99% when viewed in a cross section perpendicular to the axial direction of the sleeve including at least one of the multiple indentations.

The present disclosure makes it possible to improve both the electrical and mechanical properties of a cable connection structure.

FIG. 1 is a schematic cross-sectional view showing a power cable. FIG. 2 is a schematic cross-sectional view taken along the axial direction of a conductor, showing a cable connection structure according to an embodiment of the present disclosure. FIG. 3 illustrates a sleeve according to one embodiment of the present disclosure. FIG. 4 is an enlarged cross-sectional view of a portion of a sleeve according to one embodiment of the present disclosure. FIG. 5 is a flow chart illustrating a method for manufacturing a cable connection structure according to an embodiment of the present disclosure. FIG. 6 is a schematic diagram showing a part of a manufacturing method of a cable connection structure according to an embodiment of the present disclosure. FIG. 7 is a schematic diagram showing a part of a manufacturing method of a cable connection structure according to an embodiment of the present disclosure. FIG. 8 is a diagram showing a sleeve according to a first modified example of an embodiment of the present disclosure. FIG. 9 is a diagram showing a sleeve according to a second modified example of an embodiment of the present disclosure.

[Description of the embodiments of the present disclosure]
<Insights gained by the inventors>
First, the findings of the inventors will be described.

In recent years, the use of conductors containing aluminum has been increasing in order to reduce the weight and manufacturing costs of power cables. However, when connecting power cables having such aluminum conductors, an aluminum oxide coating is formed on the outer circumference of the conductor wires, and this oxide coating must be removed.

As mentioned above, when the conductor wires have an oxide coating, the following problems may occur when connecting power cables.

For example, in the method used with conventional copper conductors, where the sleeve is compressed so that its cross section is hexagonal, a longer sleeve length is required to reduce the contact resistance between the sleeve and the aluminum conductor.

For example, welding aluminum conductors can reduce the mechanical strength of the welded part and can lengthen the time required for welding.

To solve these problems, the inventors have investigated a method of forming an indentation in the radial direction of the sleeve. By forming such an indentation, the conductor can be crushed to a greater extent, and the oxide coating of the conductor wire can be broken. This increases the contact area between the sleeve and the conductor. As a result, the contact resistance between the sleeve and the conductor can be reduced. Furthermore, by increasing the contact area between the sleeve and the conductor, the tensile strength can be increased.

However, there were cases where the tensile strength of a pair of power cables connected by a sleeve decreased depending on the indent compression conditions. When a cross section of a sleeve with reduced tensile strength was observed, it was found that the indent had been pressed in too far, causing the thickness of the sleeve at the indent to become thinner. As a result, the sleeve itself broke at the thinner portion. This phenomenon made it difficult to achieve both electrical and mechanical properties in a cable connection structure.

The inventors therefore conducted extensive research into the compression mode of the sleeve and discovered that the electrical and mechanical properties of the cable connection structure depend on the space factor of the conductor within the sleeve. As a result, they discovered a configuration that can improve both the electrical and mechanical properties of the cable connection structure.

The following disclosure is based on the above findings made by the inventor.

<Embodiments of the present disclosure>
Next, embodiments of the present disclosure will be listed and described.

[1] A cable connection structure according to one aspect of the present disclosure includes:
a pair of power cables each having a conductor;
a sleeve configured as a metal tube having a hollow portion and connecting the conductors of the pair of power cables within the hollow portion;
having
The sleeve has a plurality of indentations recessed in a radial direction of the sleeve,
The space factor of the area occupied by the conductor relative to the cross-sectional area of the hollow portion of the sleeve is greater than or equal to 90% and less than 99% when viewed in a cross section perpendicular to the axial direction of the sleeve that includes at least one of the multiple indentations.
This configuration can improve both the electrical characteristics and the mechanical characteristics of the cable connection structure.

[2] In the cable connection structure described in [1] above,
The sleeve has a plurality of outer peripheral side surfaces compressed so that a cross section perpendicular to an axial direction of the sleeve is polygonal,
Each of the plurality of indentations is recessed from each of the plurality of outer circumferential side surfaces in a radial direction of the sleeve.
According to this configuration, it is possible to stably improve both the electrical characteristics and the mechanical characteristics of the cable connection structure while shortening the axial length of the sleeve.

[3] In the cable connection structure described in [2] above,
Two or more of the plurality of indentations are disposed at different positions in the axial direction of the sleeve and are provided on different outer circumferential side surfaces of the plurality of outer circumferential side surfaces.
According to this configuration, it is possible to stably reduce the contact resistance at the connection portion of the pair of conductors.

[4] In the cable connection structure according to the above [2] or [3],
the sleeve is compressed so that the cross section is hexagonal;
The multiple indents are arranged with two-fold symmetry, three-fold symmetry, or six-fold symmetry around the central axis of the sleeve when multiple different cross sections including at least one indent are viewed stacked in the axial direction of the sleeve.
According to this configuration, the electrical characteristics and mechanical characteristics of the cable connection structure can be improved more stably.

Note that "n-fold symmetry" here means rotational symmetry in which an object overlaps with itself when rotated by (360/n) degrees around the central axis, where n is an integer equal to or greater than 2.

[5] In the cable connection structure according to any one of [2] to [4] above,
the sleeve is compressed so that the cross section is hexagonal;
The multiple indents are arranged with two-fold or three-fold symmetry around the central axis of the sleeve within the same cross section perpendicular to the axial direction of the sleeve.
This configuration is effective when it is desired to increase the space factor.

[6] In the cable connection structure according to any one of [1] to [5] above,
Each of the multiple outer peripheral side surfaces bulges outward in the radial direction of the sleeve from a flat surface parallel to the axial direction of the sleeve.
According to this configuration, an optimal space factor can be stably obtained.

[7] A connecting power cable according to another aspect of the present disclosure includes:
The present invention includes at least one cable connection structure according to any one of the above [1] to [6].
This configuration can improve both the electrical characteristics and the mechanical characteristics of the cable connection structure.

[8] A method for producing a cable connection structure according to yet another aspect of the present disclosure includes:
Providing a pair of power cables, each having a conductor;
connecting the conductors of the pair of power cables with a sleeve configured as a metal tube having a hollow portion;
having
The step of connecting the conductors includes:
forming a plurality of radial indentations in the sleeve;
In the step of forming the plurality of indentations,
The space factor of the area occupied by the conductor relative to the cross-sectional area of the hollow portion of the sleeve is 90% or more and less than 99% when viewed in a cross section perpendicular to the axial direction of the sleeve that includes at least one of the multiple indentations.
This configuration can improve both the electrical characteristics and the mechanical characteristics of the cable connection structure.

[Details of the embodiment of the present disclosure]
Next, an embodiment of the present disclosure will be described below with reference to the drawings. Note that the present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

<One embodiment of the present disclosure>
(1) Linking Power Cable and Cable Connection Structure A schematic configuration of a linking power cable 10 and a cable connection structure (cable connection portion) 20 according to an embodiment of the present disclosure will be described with reference to Figs. 1 and 2 .

Note that the lower half of the structure is omitted in Figure 2. In Figure 2, the side of the power cable is shown with the stripped sections in steps.

As shown in FIG. 2, the interconnected power cable 10 of this embodiment has, for example, a plurality of power cables 100 and at least one cable connection structure 20.

In the following, the "axial direction" of the power cable 100 refers to the direction along the central axis of the power cable 100. The "radial direction" of the power cable 100 refers to the direction from the central axis of the power cable 100 toward the outer periphery. The "circumferential direction" of the power cable 100 refers to the direction along the outer periphery of the power cable 100.

Note that the same terminology as for the power cable 100 can also be used for the cylindrical sleeve 200, etc.

[Power cable]
As shown in FIG. 1, the power cable 100 is configured as, for example, a solid insulated cable (CE cable or CV cable: crosslinked polyethylene (PE) insulated PE or PVC sheathed cable, also called an XLPE cable) which is a high-voltage power transmission cable.

The power cable 100 is configured as, for example, an underwater cable (submarine cable, undersea cable, etc.). The power cable 100 has, for example, a conductor 110, a cable inner semiconductive layer 120, a cable insulating layer 130, a cable outer semiconductive layer 140, a water absorption layer (not shown), a cable metal shielding layer 150, and a cable outer periphery structure 170, in this order from the central axis of the conductor 110 toward the outer periphery of the power cable 100. The cable outer periphery structure 170 in the underwater cable has, for example, a corrosion protection layer, a seat yarn layer, an iron wire exterior (armoring), and a yarn layer from the region close to the cable metal shielding layer 150 toward the outer periphery. The cable metal shielding layer 150 in the underwater cable is, for example, a metal sheath.

For the sake of simplicity, the following description will be given assuming that the outer side of the cable metal shielding layer 150 is the cable sheath 160.

The conductor 110 has, for example, a plurality of conductor wires 112. In each conductor wire layer 114, the plurality of conductor wires 112 are arranged, for example, twisted in a spiral shape along the outer peripheral surface of the inner layer.

The conductor wires 112 in at least one of the pair of power cables 100 have, for example, an oxide coating on the outer periphery. Specifically, in this embodiment, in both power cables 100, the conductor wires 112 contain, for example, aluminum or an aluminum alloy, and have an aluminum oxide coating on the outer periphery.

As shown in FIG. 2, the power cable 100 is stripped in stages (so-called "stage stripped") from the tip of the conductor 110 in the opposite direction. That is, the conductor 110, the cable inner semiconductive layer 120, the cable insulating layer 130, the cable outer semiconductive layer 140, the cable metal shielding layer 150, and the cable sheath 160 are exposed in this order from the tip of the conductor 110 in the opposite direction. Hereinafter, each stage-stripped portion may be referred to as an "exposed portion." With this configuration, the power cables 100 can be connected to each other in order from the central axis toward the outer periphery.

As shown in FIG. 2, a plurality of power cables 100 are provided. Of the plurality of power cables 100, a pair of power cables 100 are butted together with the axes of their conductors 110 aligned. In the following description, one of the pair of power cables 100 may be referred to as the "first power cable 100a" and the other power cable 100 may be referred to as the "second power cable 100b."

[Cable connection structure]
2 , the cable connection structure 20 is configured to connect, for example, a pair of power cables 100. Specifically, the cable connection structure 20 has, for example, the above-mentioned pair of power cables 100, a sleeve (conductor connection tube) 200, a sleeve cover 290, an insulating tube (rubber connection tube, rubber unit, insulating unit) 300, a protective tube (metal tube) 400, and a filler 480.

(sleeve)
The sleeve 200 is provided, for example, to surround a connection point between the conductors 110 so as to connect the conductors 110 of a pair of power cables 100. The "connection point (connection portion)" here means a point (part, location) where the pair of conductors 110 butt their axes together and the tips of the pair of conductors 110 are close to each other.

In this embodiment, the sleeve 200 has, for example, a number of indentations 240. The sleeve 200 will be described in more detail below.

(Sleeve cover)
The sleeve cover 290 is, for example, cylindrical and is provided to surround the outer periphery of the sleeve 200. The sleeve cover 290 has a locking portion 292 that protrudes in the radial direction of the sleeve cover 290 at an axial end of the sleeve cover 290. The locking portion 292 bites into the exposed cable insulation layer 130 of each of the pair of power cables 100. This makes it possible to suppress shrink-back of the cable insulation layer 130 in the pair of power cables 100.

(insulating tube)
The insulating tube 300 is configured, for example, as an insulating tubular member, and is provided so as to cover the outer periphery of the sleeve 200 (the outer periphery of the sleeve cover 290 ) and a portion of the outer periphery of each of the pair of power cables 100 .

The insulating tube 300 is configured, for example, as a so-called cold shrink type. That is, the insulating tube 300 has an elastic material molded as a single unit, and is designed to elastically shrink at room temperature to fit closely to the connection portion of the power cable 100.

The insulating tube 300 is configured, for example, to reduce the electric field around the sleeve 200 while maintaining the insulation around the sleeve 200. Specifically, the insulating tube 300 has, for example, an inner semiconductive layer 320, an insulating layer 340, a stress cone portion 360, and an outer semiconductive layer 380.

The internal semiconductive layer 320 is configured in a cylindrical shape so as to cover the outer circumference of the sleeve 200. The internal semiconductive layer 320 contains, for example, rubber having semiconductivity. The internal semiconductive layer 320 is at the same potential as the sleeve 200.

The insulating layer 340 is provided to cover the outer periphery of the internal semiconducting layer 320. The insulating layer 340 contains, for example, rubber having insulating properties.

The stress cone portion 360 contains semiconductive rubber. The stress cone portion 360 is provided in a region close to each of the axial ends of the insulating layer 340, and has a conical inner surface that expands toward the center of the insulating layer 340 in the axial direction. A portion of the inner surface of the stress cone portion 360 is in contact with the cable outer semiconductive layer 140 of the stepped stripped power cable 100.

The outer semiconductive layer 380 is provided to cover the outer periphery of the insulating layer 340. The outer semiconductive layer 380 contains rubber that has semiconductivity.

This configuration of the insulating tube 300 can reduce the electric field around the sleeve 200.

(Protection tube)
The protective tube 400 is configured to cover and protect the outer periphery of the insulating tube 300 and a part of the outer periphery of each of the pair of power cables 100. The protective tube 400 is made of, for example, a metal. Examples of the metal constituting the protective tube 400 include copper and lead.

The gap between each of the axial ends of the protective tube 400 and the power cable 100 is sealed with a predetermined sealing material (not shown).

(Filling material)
The filler 480 is filled between the insulating tube 300 and the protective tube 400 inside the protective tube 400. For example, a so-called waterproof compound can be used as the filler 480. This can prevent moisture from entering the protective tube 400.

(2) Sleeve Next, a sleeve 200 according to an embodiment of the present disclosure will be described with reference to FIGS. 3 and 4. FIG.

Figure 3 includes a side view, a front view, a cross-sectional view along line X-X', a cross-sectional view along line Y-Y', and a cross-sectional view along line Z-Z'. Conductor 110 is omitted in Figures 3 and 4.

As shown in FIG. 3, the sleeve 200 is configured, for example, as a metal tube having a hollow portion 210. The exposed portions of a pair of conductors 110 including connection points are inserted into the hollow portion 210 of the sleeve 200, and the pair of conductors 110 are connected. An example of the metal of the sleeve 200 is aluminum.

The sleeve 200 may have a partition wall that closes the hollow portion 210, for example, at the center of the axial direction of the sleeve 200. This makes it possible to suppress the propagation of water through the conductor 110.

The sleeve 200 of this embodiment has, for example, a plurality of indentations 240 that are recessed in the radial direction of the sleeve 200. That is, the indentations 240, for example, locally compress the conductor 110 in the radial direction of the sleeve 200.

The indent 240 forms a convex surface 242 that protrudes toward the central axis of the sleeve 200 on the inner circumference of the sleeve 200. The hole shape of the indent 240 when viewed from the outer circumference of the sleeve 200 is, for example, circular. The convex surface 242 of the indent 240 on the inner circumference of the sleeve 200 is curved in a convex spherical shape toward the central axis of the sleeve 200.

In such a configuration, the convex surface 242 of the indent 240 compresses the conductor wire 112, or multiple conductor wires 112 compress each other, thereby breaking at least a portion of the oxide coating on each conductor wire 112.

In this embodiment, the space factor of the conductor 110 within the sleeve 200 is optimized.

Specifically, the space factor B/A of the area B occupied by the conductor 110 relative to the cross-sectional area A of the hollow portion 210 of the sleeve 200 is, for example, 90% or more and less than 99% when viewed in a cross section perpendicular to the axial direction of the sleeve 200 that includes at least one of the multiple indentations 240.

By setting the space factor B/A to 90% or more, the oxide film of the conductor wire 112 can be broken. On the other hand, by setting the space factor B/A to less than 99%, breakage of the sleeve 200 due to excessive compression of the sleeve 200 can be suppressed. As a result, both the electrical characteristics and the mechanical characteristics of the cable connection structure 20 can be improved.

In this embodiment, the sleeve 200 is subjected to, for example, both so-called polygonal compression and indent compression in order to achieve the above-mentioned space factor B/A.

That is, the sleeve 200 has, for example, multiple outer peripheral side surfaces 220 compressed so that a cross section perpendicular to the axial direction of the sleeve 200 is polygonal. The "outer peripheral side surface 220" here means a side surface that constitutes one side of a polygon when viewed in a cross section perpendicular to the axial direction of the sleeve 200. Each of the multiple indents 240 is, for example, recessed in the radial direction of the sleeve 200 from each of the multiple outer peripheral side surfaces 220. This makes it possible to stably improve both the electrical characteristics and the mechanical characteristics of the cable connection structure 20.

In this embodiment, the sleeve 200 is compressed so that the cross section perpendicular to the axial direction of the sleeve 200 is hexagonal. This allows each outer peripheral side surface 220 to be compressed in a balanced manner. As a result, the conductor 110 can be crushed uniformly toward the central axis.

In this embodiment, the two or more indents 240 are arranged at different positions in the axial direction of the sleeve 200 and are provided on different outer peripheral side surfaces 220. This allows sufficient unevenness to be formed between the two or more adjacent indents 240.

In this embodiment, the multiple indents 240 are arranged in three-fold symmetry around the central axis of the sleeve 200 when multiple different cross sections including at least one indent 240 are viewed overlapping in the axial direction of the sleeve 200. This allows the multiple indents 240 to be distributed in a balanced manner throughout the entire axial direction of the sleeve 200.

In this embodiment, the multiple indentations 240, for example, compress different conductor wires 112 from each other. This makes it possible to simultaneously reduce contact resistance and improve mechanical strength.

More specifically, the sleeve 200 has, for example, a first outer peripheral side surface 220a, a second outer peripheral side surface 220b, a third outer peripheral side surface 220c, a fourth outer peripheral side surface 220d, a fifth outer peripheral side surface 220e, and a sixth outer peripheral side surface 220f around the central axis.

The sleeve 200 has, for example, a first indent 240a, a second indent 240b, and a third indent 240c.

The first indent 240a is disposed at a position centered on the X-X' line cross section. The first indent 240a is provided, for example, on the first outer peripheral side surface 220a. For example, only one first indent 240a is provided within the X-X' line cross section.

The second indent 240b is disposed at a different position from the first indent 240a in the axial direction of the sleeve 200. The second indent 240b is disposed, for example, at a position centered on the Y-Y' line cross section. The second indent 240b is provided, for example, on the third outer peripheral side surface 220c. For example, only one second indent 240b is provided within the Y-Y' line cross section.

The third indent 240c is disposed at a different position in the axial direction of the sleeve 200 from the first indent 240a and the second indent 240b. The third indent 240c is disposed, for example, at a position centered on the Z-Z' line cross section. The third indent 240c is provided, for example, on the fifth outer peripheral side surface 220e. For example, only one third indent 240c is provided within the Z-Z' line cross section.

The first indent 240a, the second indent 240b and the third indent 240c are evenly spaced in the axial direction of the sleeve 200.

The size (hole diameter, recess depth) of the first indent 240a, the size of the second indent 240b, and the size of the third indent 240c are equal to each other.

For example, two sets including the first indent 240a, the second indent 240b, and the third indent 240c are provided. The two sets are arranged symmetrically with respect to the center of the sleeve 200 in the axial direction.

Furthermore, in this embodiment, as shown in FIG. 4, each of the multiple outer peripheral side surfaces 220 bulges outward in the radial direction of the sleeve 200 from a flat surface FP parallel to the axial direction of the sleeve 200. This allows the above-mentioned space factor B/A to be stably obtained.

The above-described configuration makes it possible to stably improve both the electrical and mechanical characteristics of the cable connection structure 20.

(3) Manufacturing method of cable connection structure (manufacturing method of connected power cable, cable connection method)
Next, a method for manufacturing a cable connection structure according to the present embodiment will be described with reference to Figures 1 to 7. Note that the conductor 110 is omitted in Figure 6.

As shown in FIG. 5, the manufacturing method of the cable connection structure 20 of this embodiment includes, for example, a preparation process S10, a conductor connection process S20, an insulating tube arrangement process S30, a protective tube arrangement process S40, and a filling process S50.

(S10: Preparation process)
First, the pair of power cables 100, the sleeve 200, the sleeve cover 290, the insulating tube 300 and the protective tube 400 that constitute the cable connection structure 20 are prepared.

For example, a half-split pipe (not shown) is inserted into the hollow portion of the insulating tube 300 in advance at the factory. This expands the diameter of the insulating tube 300.

Next, for example, at the installation site of the power cables 100, the pair of power cables 100 are gradually stripped in the axial direction from one end of each. This exposes the conductor 110, the cable insulating layer 130, the cable outer semiconductive layer 140, and the cable sheath 160 in this order from the tip of the power cable 100.

After preparing each component that constitutes the cable connection structure 20, pass each of the insulating tube 300 and the protective tube 400 through the power cable 100, and then move each of the insulating tube 300 and the protective tube 400 to a predetermined position away from the tip of the power cable 100.

(S20: Conductor connection process)
When the preparation step S10 is completed, the pair of power cables 100 are butted together with the axes of the conductors 110 aligned within the sleeve 200. After the pair of power cables 100 are butted together, the sleeve 200 is compressed to connect the conductors 110 of the pair of power cables 100.

In this embodiment, multiple indents 240 are formed in the radial direction of the sleeve 200. At this time, the space factor B/A of the conductor 110 in the sleeve 200 is set to 90% or more and less than 99% when viewed in a cross section perpendicular to the axial direction of the sleeve 200 that includes at least one of the multiple indents 240.

As shown in Figures 5 to 7, in this embodiment, the conductor connection process S20 includes, for example, a polygon compression process S22 and an indent compression process S24 in order to achieve the space factor B/A as described above.

In this embodiment, the indent compression process S24 is performed, for example, after the polygon compression process S22. This makes it possible to avoid demolding problems. In the indent compression process S24 of this embodiment, the compressor for the polygon compression process S22 is used, and either the lower die 820 or the upper die 840 is replaced with the indent die 860 depending on the situation, as described below.

(S22: Polygon compression process)
6, in a polygonal compression step S22, the sleeve 200 is compressed so that a cross section perpendicular to the axial direction of the sleeve 200 has a polygonal shape. As a result, a plurality of outer peripheral side surfaces 220 are formed.

Specifically, the cylindrical sleeve 200 is placed between a lower die 820 arranged vertically below and an upper die 840 arranged vertically above. The lower die 820 and the upper die 840 have inner peripheral surfaces that form the outer peripheral side surface 220 of the polygonal sleeve 200. Once the sleeve 200 is placed between them, the lower die 820 and the upper die 840 compress the sleeve 200 so that its cross section becomes hexagonal.

(S24: Indentation compression process)
After the polygonal compression step S22 is completed, the upper die 840 is replaced with an indentation die 860 as shown in the center of Fig. 6. The indentation die 860 has, for example, a protrusion 862 at the center of the inner circumference for forming the indent 240. The indentation die 860 is configured so that the portion other than the protrusion 862 does not come into contact with the sleeve 200.

Once the replacement with the indentation die 860 is complete, as shown in the right diagram of Figure 6, in the indentation compression process S24, the lower die 820 and the indentation die 860 are used to recess the first indent 240a from the first outer peripheral side surface 220a in the radial direction of the sleeve 200.

At this time, the sleeve 200, whose cross section is already hexagonal, is fixed to the inner peripheral surface of the lower die 820. This makes it possible to suppress circumferential rotational deviation of the sleeve 200 when the indent 240 is compressed.

When the compression of the first indent 240a is complete, as shown in the left diagram of Figure 7, the upper die 840 is returned to its original position, and the lower die 820 is replaced with the indentation die 860. At this time, between the upper die 840 and the indentation die 860, the sleeve 200 is moved a predetermined distance in the axial direction without rotating in the circumferential direction.

Furthermore, as shown in the center diagram of FIG. 7, the compressor is rotated 60° around the central axis of the sleeve 200. This causes the protrusion 862 of the indentation die 860 to face the third outer peripheral side surface 220c. By rotating the compressor while replacing the indentation die 860 in this way, the angle at which the heavy compressor is rotated can be reduced.

Next, as shown in the right diagram of FIG. 7, the upper die 840 and the indentation die 860 are used to recess the second indent 240b from the third outer peripheral side surface 220c in the radial direction of the sleeve 200.

When compression of the second indent 240b is complete, the compressor is rotated 120° around the central axis of the sleeve 200 (not shown). Between the upper die 840 and the indentation die 860, the sleeve 200 is moved a predetermined distance in the axial direction without rotating in the circumferential direction. In this state, the third indent 240c is recessed in the radial direction of the sleeve 200 from the fifth outer peripheral side surface 220e.

In this way, a first set including the first indent 240a, the second indent 240b, and the third indent 240c is formed. The indent compression process in the second set, which is arranged symmetrically around the axial center of the sleeve 200, may be performed in the same manner as that of the first set described above.

By the above-mentioned indent compression process S24, two or more of the multiple indents 240 are arranged at different positions in the axial direction of the sleeve 200, and are formed on different outer peripheral side surfaces 220 of the multiple outer peripheral side surfaces 220.

When multiple different cross sections including at least one indent 240 are viewed stacked in the axial direction of the sleeve 200, the multiple indents 240 are arranged in a three-fold symmetry around the central axis of the sleeve 200.

As described above, by performing the indentation compression process S24 after the polygonal compression process S22, each of the multiple outer peripheral side surfaces 220 bulges outward in the radial direction of the sleeve 200 beyond the flat surface FP parallel to the axial direction of the sleeve 200.

After the polygon compression process S22 and the indent compression process S24 are completed, the sleeve cover 290 is placed over the outer periphery of the sleeve 200. The recess of the indent 240 may be filled with a conductive filler (not shown).

(S30: Insulating tube arrangement process)
When the conductor connecting step S20 is completed, the insulating tube 300 is arranged so as to cover the outer periphery of the sleeve 200 and a part of the outer periphery of each of the pair of power cables 100. Specifically, the insulating tube 300, the diameter of which has been expanded by the inner core, is moved to a position where it overlaps with the sleeve 200. After the insulating tube 300 is arranged in a predetermined position, the half-split pipe is gradually pulled out, and the insulating tube 300 is gradually reduced in diameter in the axial direction.

(S40: Protective tube arrangement process)
After the insulating tube 300 is placed, the protective tube 400 is placed so as to cover the outer periphery of the insulating tube 300 and a portion of the outer periphery of each of the pair of power cables 100. After the protective tube 400 is placed, both ends of the protective tube 400 in the axial direction are sealed.

(S50: Filler filling step)
When the protective tube arrangement step S40 is completed, the filler 480 is injected into the protective tube 400 from the injection port of the protective tube 400, and the filler 480 is filled between the insulating cylinder 300 and the protective tube 400. After the filler 480 is filled, the filler 480 is hardened under predetermined conditions.

This completes the manufacture of the cable connection structure 20 of this embodiment.

(4) Summary of the Present Invention According to the present invention, one or more of the following advantages can be obtained.

(a) In this embodiment, the space factor B/A of the conductor 110 within the sleeve 200 is 90% or more and less than 99% when viewed in a cross section perpendicular to the axial direction of the sleeve 200 that includes at least one of the multiple indents 240.

By setting the space factor B/A to 90% or more, the convex surface 242 of the indent 240 can compress the conductor wire 112, and the multiple conductor wires 112 can compress each other. This moderate compression can break at least a portion of the oxide coating on each conductor wire 112. As a result, the contact resistance at the connection between the pair of conductors 110 can be reduced.

On the other hand, by setting the space factor B/A to less than 99%, it is possible to prevent the thickness of the sleeve 200 from becoming excessively thin at the indent 240 due to excessive compression of the sleeve 200. This makes it possible to prevent the sleeve 200 from breaking when tensioned. As a result, it is possible to prevent a decrease in the tensile load in the cable connection structure 20 (the tensile load at which the sleeve 200 breaks).

In this way, according to this embodiment, the electrical and mechanical properties of the cable connection structure 20 can be improved.

(b) In this embodiment, the sleeve 200 has multiple outer peripheral side surfaces 220 that are compressed so that the cross section perpendicular to the axial direction of the sleeve 200 is polygonal. In this way, by compressing the entire sleeve 200 into a polygonal cross section, the multiple conductor wires 112 can be evenly and closely spaced within the sleeve 200.

In this state, each of the multiple indentations 240 is recessed radially from each of the multiple outer peripheral side surfaces 220 of the sleeve 200. This allows the oxide coating of the conductor wire 112 to be broken reliably even if the number of indentations 240 is reduced.

As a result, the above-mentioned optimal space factor B/A can be stably obtained while shortening the axial length of the sleeve 200. In other words, it is possible to stably improve both the electrical characteristics and the mechanical characteristics of the cable connection structure 20.

(c) In this embodiment, the two or more indents 240 are arranged at different positions in the axial direction of the sleeve 200 and are provided on different outer peripheral side surfaces 220. This makes it possible to prevent the two or more adjacent indents 240 from being excessively close to each other. The unevenness of the inner peripheral surface of the sleeve 200 can be sufficiently formed between these indents 240. In other words, it is possible to prevent a reduction in the contact area between the sleeve 200 and the conductor 110 caused by the continuous arrangement of the indents 240. As a result, it is possible to stably reduce the contact resistance at the connection portion of a pair of conductors 110.

(d) In this embodiment, the multiple indents 240 are arranged in three-fold symmetry around the central axis of the sleeve 200 when multiple different cross sections including at least one indent 240 are viewed overlapping in the axial direction of the sleeve 200. In other words, the multiple indents 240 arranged at different positions in the axial direction of the sleeve 200 can compress the conductor 110 in a balanced manner around the central axis of the sleeve 200.

This allows the conductive points between the sleeve 200 and the conductor 110 and the anchor points of the indent 240 to the conductor 110 to be distributed in a well-balanced manner throughout the entire axial direction of the sleeve 200. As a result, the electrical and mechanical properties of the cable connection structure 20 can be improved in a more stable manner.

(e) In this embodiment, the multiple indentations 240 compress different conductor wires 112 from each other. In other words, the multiple indentations 240 can break the oxide coatings of the different conductor wires 112 from each other. As a result, the contact resistance between the sleeve 200 and the conductor 110 can be stably reduced.

In addition, it is possible to form complex irregularities on the inner peripheral surface of the sleeve 200. This improves the retention force of the conductor 110 by the sleeve 200.

(f) In this embodiment, the indent compression process S24 is performed after the polygon compression process S22.

Here, when the indent compression step S24 is performed simultaneously with the polygon compression step S22, the outer shape of the sleeve 200 expands within the die due to compression of the indent 240. Therefore, the filling rate of the sleeve 200 becomes relatively high in the portion forming the corner of the polygon within the die. As a result, it becomes difficult to release the sleeve 200 from the die.

In contrast, in this embodiment, the indent compression step S24 is performed after the polygon compression step S22, so that the expansion of the outer shape of the sleeve 200 caused by the compression of the indent 240 can be tolerated. This makes it possible to avoid demolding problems.

In addition, in this embodiment, by using such a process sequence, each of the multiple outer peripheral side surfaces 220 can be expanded radially outward of the sleeve 200 from the flat surface FP parallel to the axial direction of the sleeve 200. In other words, excessive compressive stress on the conductor wire 112 due to the indent 240 can be released from the outer peripheral side surface 220 toward the radially outward of the sleeve 200. This makes it possible to stably obtain the above-mentioned optimal space factor B/A.

(g) In the indentation compression process S24 of this embodiment, the compressor used in the polygonal compression process S22 is used, and either the lower die 820 or the upper die 840 is replaced with the indentation die 860.

Here, when performing the indent compression process on a sleeve 200 with a circular cross section, a dedicated indent compression device according to the diameter of the sleeve 200 is required. When using such an indent compression device, a high level of skill is required in assembling, operating, and installing the device.

In contrast, in this embodiment, if the indentation die 860 is prepared, a commercially available compressor can be used for the polygon compression process S22. This eliminates the need for a dedicated indentation compression device, reducing costs. Furthermore, it also eliminates the need for advanced skills.

(h) In the indent compression process S24 of this embodiment, the sleeve 200, which already has a hexagonal cross section, is fixed to the inner peripheral surface of either the lower die 820 or the upper die 840, and the indent die 860 forms an indent 240 in the sleeve 200. This makes it possible to suppress circumferential rotational deviation of the sleeve 200 when compressing the indent 240. In other words, by simply determining the axial position of the sleeve 200 and the position of the outer peripheral side surface 220, the indent 240 can be stably compressed without causing positional deviation of the indent 240. This allows an experienced person familiar with the conventional hexagonal compression process to easily understand the process without the need for special training, and to perform the work reliably.

(5) Modifications of an embodiment The above-described embodiment can be modified as necessary as in the following modifications. Only elements different from the above-described embodiment will be described below, and elements substantially the same as those described in the above-described embodiment will be denoted by the same reference numerals and description thereof will be omitted.

<Modification 1>
As shown in FIG. 8 , in the first modified example, the multiple indents 240 are arranged, for example, in two-fold symmetry around the central axis of the sleeve 200 within the same cross section perpendicular to the axial direction of the sleeve 200 .

In variant 1, the multiple indents 240 are arranged with three-fold symmetry around the central axis of the sleeve 200 when, for example, multiple different cross sections including at least one indent 240 are viewed overlapping in the axial direction of the sleeve 200. In variant 1, the multiple indents 240 have the same cross-sectional shape, so the arrangement of the multiple indents 240 when viewed in the overlapping cross sections can also be considered to be two-fold symmetric or six-fold symmetric.

According to the first modification, the compressive stress due to the pair of indents 240 can be made to intersect at the central axis of the sleeve 200. This ensures that the conductor 110 in the portion sandwiched between the pair of indents 240 is compressed. In other words, the first modification is effective when it is desired to increase the space factor B/A more than in the above-mentioned embodiment. In the first modification, the conductor 110 is compressed more than in the above-mentioned embodiment, so that the crushing of the conductor 110 can be increased and the contact area between the sleeve 200 and the conductor 110 can be increased. As a result, the electrical and mechanical characteristics of the cable connection structure 20 can be stably improved.

<Modification 2>
As shown in FIG. 9 , in the second modification, the multiple indents 240 are arranged, for example, in three-fold symmetry around the central axis of the sleeve 200 within the same cross section perpendicular to the axial direction of the sleeve 200 .

In Modification 2, the multiple indents 240 are arranged with two-fold symmetry around the central axis of the sleeve 200 when, for example, multiple different cross sections including at least one indent 240 are viewed overlapping in the axial direction of the sleeve 200. Note that in Modification 2, since the multiple indents 240 have the same cross-sectional shape, the arrangement of the multiple indents 240 when viewed in the overlapping cross sections can also be considered to be three-fold symmetry or six-fold symmetry.

According to the second modification, the compressive stresses due to the three indentations 240 can be caused to intersect at the central axis of the sleeve 200. This ensures that the conductor 110 in the portion sandwiched between the three indentations 240 is compressed. In other words, the second modification is effective when it is desired to further increase the space factor B/A compared to the above-mentioned embodiment and the first modification. In the second modification, the conductor 110 is compressed further than in the first modification, so that the electrical and mechanical characteristics of the cable connection structure 20 can be improved more stably.

<Other embodiments of the present disclosure>
Although the embodiments of the present disclosure have been specifically described above, the present disclosure is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit and scope of the present disclosure.

In the above embodiment, the power cable 100 is configured as an underwater cable, but the power cable 100 may be configured as an onshore cable or an underground cable.

In the above embodiment, the conductor wire 112 contains aluminum or an aluminum alloy and has an aluminum oxide coating on the outer periphery. However, the conductor 110 may be configured as a so-called insulated wire conductor. That is, the conductor wire 112 may contain, for example, copper or a copper alloy and have an insulating coating on the outer periphery.

In the above embodiment, the conductor 110 is shown to have a cylindrical conductor wire layer 114, but the conductor 110 may be a so-called divided conductor. That is, the conductor wire layer 114 may be, for example, a layer of an irregular shape such as a fan shape.

In the above embodiment, the conductor wires 112 in both power cables 100 have an oxide coating or an insulating coating on their outer periphery, but the present disclosure is not limited to this case. It is sufficient that the conductor wires 112 in at least one of the pair of power cables 100 have an oxide coating or an insulating coating on their outer periphery.

In the above embodiment, the size (hole diameter, recess depth) of the first indent 240a, the size of the second indent 240b, and the size of the third indent 240c are equal to each other, but the present disclosure is not limited to this case. The sizes of the multiple indents 240 may be different from each other.

Although the above embodiment does not mention the application of a compound, a compound may be applied in the present disclosure. For example, when the conductor 110 and the sleeve 200 contain aluminum or an aluminum alloy, a compound containing a mineral may be provided between the inner peripheral surface of the sleeve 200 and the outer peripheral surface of the conductor 110. This makes it possible to suppress the intrusion of oxygen into the sleeve 200 and suppress the reformation of the aluminum oxide film. As a result, electrical resistance can be stably reduced.

In the above embodiment, the cable connection structure 20 has an insulating tube 300 made of rubber that is molded as a single unit, but the present disclosure is not limited to this case. The cable connection structure 20 may be configured as a so-called factory joint, and the inner semiconductive layer 320, insulating layer 340, stress cone portion 360, and outer semiconductive layer 380 may be configured separately.

In the above embodiment, the interconnecting power cable 10 has one cable connection structure 20, but the interconnecting power cable 10 may have multiple cable connection structures 20.

<Additional Notes>
The following additional aspects of the present disclosure.

(Appendix 1)
a pair of power cables each having a conductor;
a sleeve configured as a metal tube having a hollow portion and connecting the conductors of the pair of power cables within the hollow portion;
having
The sleeve has a plurality of indentations recessed in a radial direction of the sleeve,
A cable connection structure in which a space factor of an area occupied by the conductor relative to a cross-sectional area of the hollow portion of the sleeve is 90% or more and less than 99% when viewed in a cross section perpendicular to the axial direction of the sleeve and including at least one of the multiple indentations.

(Appendix 2)
The sleeve has a plurality of outer peripheral side surfaces compressed so that a cross section perpendicular to an axial direction of the sleeve is polygonal,
2. The cable connection structure described in claim 1, wherein each of the plurality of indentations is recessed in a radial direction of the sleeve from each of the plurality of outer circumferential side surfaces.

(Appendix 3)
The cable connection structure described in Appendix 2, wherein two or more of the plurality of indents are arranged at different positions in the axial direction of the sleeve and are provided on different outer circumferential side surfaces of the plurality of outer circumferential side surfaces.

(Appendix 4)
the sleeve is compressed so that the cross section is hexagonal;
The cable connection structure described in Appendix 2 or Appendix 3, wherein the multiple indents are arranged with two-fold symmetry, three-fold symmetry, or six-fold symmetry around the central axis of the sleeve when multiple different cross sections including at least one indent are viewed overlapping in the axial direction of the sleeve.

(Appendix 5)
the sleeve is compressed so that the cross section is hexagonal;
The cable connection structure described in any one of Supplementary Note 2 to Supplementary Note 4, wherein the multiple indentations are arranged with two-fold symmetry or three-fold symmetry around the central axis of the sleeve within the same cross section perpendicular to the axial direction of the sleeve.

(Appendix 6)
The cable connection structure according to any one of Supplementary Note 2 to Supplementary Note 5, wherein each of the outer peripheral side surfaces bulges outward in the radial direction of the sleeve from a flat surface parallel to the axial direction of the sleeve.

(Appendix 7)
7. A connected power cable comprising at least one cable connection structure according to any one of claims 1 to 6.

(Appendix 8)
Providing a pair of power cables, each having a conductor;
connecting the conductors of the pair of power cables with a sleeve configured as a metal tube having a hollow portion;
having
The step of connecting the conductors includes:
forming a plurality of radial indentations in the sleeve;
In the step of forming the plurality of indentations,
A manufacturing method for a cable connection structure, in which a space factor of an area occupied by the conductor relative to a cross-sectional area of the hollow portion of the sleeve is 90% or more and less than 99% when viewed in a cross section perpendicular to the axial direction of the sleeve including at least one of the multiple indentations.

(Appendix 9)
The step of connecting the conductors includes:
The method includes a step of compressing the sleeve so that a cross section perpendicular to an axial direction of the sleeve has a polygonal shape, thereby forming a plurality of outer peripheral side surfaces;
In the step of forming the plurality of indentations,
The method for manufacturing a cable connection structure described in Appendix 8, wherein each of the plurality of indentations is recessed in a radial direction of the sleeve from each of the plurality of outer circumferential side surfaces.

(Appendix 10)
10. The method of claim 8 or 9, wherein the step of forming the plurality of indentations is performed after the step of compressing the sleeve to form the polygonal shape.

10 Connected power cable 20 Cable connection structure 100 Power cable 100a First power cable 100b Second power cable 110 Conductor 112 Conductor wire 114 Conductor wire layer 120 Cable inner semiconductive layer 130 Cable insulation layer 140 Cable outer semiconductive layer 150 Cable metal shielding layer 160 Cable sheath 170 Cable outer peripheral structure 200 Sleeve 210 Hollow portion 220 Outer peripheral side 220a First outer peripheral side 220b Second outer peripheral side 220c Third outer peripheral side 220d Fourth outer peripheral side 220e Fifth outer peripheral side 220f Sixth outer peripheral side 240 Indent 240a First indent 240b Second indent 240c Third indent 242 Convex surface 290 Sleeve cover 292 Locking portion 300 Insulating tube 320 Inner semiconductive layer 340 Insulating layer 360 Stress cone portion 380 Outer semiconducting layer 400 Protective tube 480 Filler 820 Lower die 840 Upper die 860 Indentation die 862 Protrusion

Claims (8)

a pair of power cables each having a conductor;
a sleeve configured as a metal tube having a hollow portion and connecting the conductors of the pair of power cables within the hollow portion;
having
The sleeve has a plurality of indentations recessed in a radial direction of the sleeve,
A cable connection structure in which a space factor of an area occupied by the conductor relative to a cross-sectional area of the hollow portion of the sleeve is 90% or more and less than 99% when viewed in a cross section perpendicular to the axial direction of the sleeve and including at least one of the multiple indentations. The sleeve has a plurality of outer peripheral side surfaces compressed so that a cross section perpendicular to an axial direction of the sleeve is polygonal,
The cable connection structure according to claim 1 , wherein each of the plurality of indentations is recessed from each of the plurality of outer circumferential side surfaces in a radial direction of the sleeve. The cable connection structure according to claim 2 , wherein two or more of the plurality of indents are arranged at different positions in the axial direction of the sleeve and are provided on different outer circumferential side surfaces of the plurality of outer circumferential side surfaces. the sleeve is compressed so that the cross section is hexagonal;
4. The cable connection structure according to claim 2, wherein the indentations are arranged with two-fold symmetry, three-fold symmetry, or six-fold symmetry around a central axis of the sleeve when a plurality of different cross sections including at least one indent are viewed overlapping in the axial direction of the sleeve. the sleeve is compressed so that the cross section is hexagonal;
The cable connection structure according to claim 2 or 3, wherein the plurality of indents are arranged with two-fold or three-fold symmetry around a central axis of the sleeve in the same cross section perpendicular to the axial direction of the sleeve. The cable connection structure according to claim 2 or 3, wherein each of the outer circumferential side surfaces bulges outward in the radial direction of the sleeve from a flat surface parallel to the axial direction of the sleeve. A connected power cable comprising at least one cable connection structure according to any one of claims 1 to 3. Providing a pair of power cables, each having a conductor;
connecting the conductors of the pair of power cables with a sleeve configured as a metal tube having a hollow portion;
having
The step of connecting the conductors includes:
forming a plurality of radial indentations in the sleeve;
In the step of forming the plurality of indentations,
A manufacturing method for a cable connection structure, in which a space factor of an area occupied by the conductor relative to a cross-sectional area of the hollow portion of the sleeve is 90% or more and less than 99% when viewed in a cross section perpendicular to the axial direction of the sleeve including at least one of the multiple indentations.

Images