JP7211468B2 - Power cable connection structure and power cable connection method - Google Patents

Description

The present invention relates to a power cable, a power cable manufacturing method, a power cable connection structure, and a power cable connection method.

In the field of high-voltage underground power transmission cables, crosslinked polyethylene insulated vinyl sheathed cables (CV cables: Crosslinked polyethylene insulated PVC sheathed cables) are the mainstream in place of conventionally used oil-filled insulated power cables (OF cables: Oil Filled Cables). is becoming

However, the amount of extension of the CV cable during energization was greater than the amount of extension of the OF cable. For this reason, for example, when there is a reason for renewal, such as changing the system of the existing line where the OF cable was used, responding to an accident of the OF cable, or discarding it over time, the extension amount of the CV cable can be adjusted to the existing manhole dimensions, etc. There was a case where there was not enough room to absorb it. In such a case, the existing OF cable could not be updated to the CV cable, and the existing OF cable had to be updated again with the OF cable. Therefore, a technique for reducing the extension amount of the CV cable has been desired.

Therefore, until now, in order to suppress the extension of the CV cable, a power cable has been proposed in which a conductor element wire constituting the conductor and an Invar wire having a small linear expansion coefficient are tightly stranded (for example, Patent document 1).

JP-A-57-172608

However, in the configuration of Patent Literature 1, it was not possible to sufficiently reduce the extension amount of the power cable. For this reason, until recently, a product in which the configuration of Patent Document 1 is adopted and the extension amount of the power cable is reduced has not been realized.

SUMMARY OF THE INVENTION An object of the present invention is to provide a technique capable of reducing the amount of extension of a power cable in the installation direction.

According to one aspect of the invention,
A power cable comprising a conductor and an insulating layer covering the outer periphery of the conductor,
A hollow portion extending in the axial direction of the conductor is provided at the center of the conductor,
A wire made of a material having a higher Young's modulus and a lower coefficient of linear expansion than the material forming the conductor is inserted into the hollow portion of the conductor along the axial direction of the conductor,
A power cable is provided in which the filling rate of the wire, which is the ratio of the cross-sectional area of the wire to the cross-sectional area of the hollow portion, in an arbitrary cross section perpendicular to the axial direction of the power cable is 20% or more and 90% or less. be.

According to another aspect of the invention,
A power cable comprising a conductor and an insulating layer covering the outer periphery of the conductor,
A hollow portion extending in the axial direction of the conductor is provided at the center of the conductor,
A wire made of a material having a higher Young's modulus and a lower coefficient of linear expansion than the material forming the conductor is inserted into the hollow portion of the conductor along the axial direction of the conductor,
The thermal stress generated in the power cable when the difference between the temperature of the conductor of the power cable and the base temperature is 65° C. is the buckling of the conductor when both ends of the power cable with a length of 6000 mm are fixed. A power cable is provided that is over load.

According to yet another aspect of the invention,
A power cable comprising a conductor and an insulating layer covering the outer periphery of the conductor,
A hollow portion extending in the axial direction of the conductor is provided at the center of the conductor,
A wire made of a material having a higher Young's modulus and a lower coefficient of linear expansion than the material forming the conductor is inserted into the hollow portion of the conductor along the axial direction of the conductor,
A power cable is provided in which the hollow portion is asymmetric with respect to the center of the conductor in at least some of the plurality of cross sections perpendicular to the axial direction of the power cable.

According to yet another aspect of the invention,
A power cable comprising a conductor and an insulating layer covering the outer periphery of the conductor,
A hollow portion extending in the axial direction of the conductor is provided at the center of the conductor,
A wire made of a material having a higher Young's modulus and a lower coefficient of linear expansion than the material forming the conductor is inserted into the hollow portion of the conductor along the axial direction of the conductor,
A power cable is provided in which the hollow portion is rotationally asymmetric in at least some of the plurality of cross sections perpendicular to the axial direction of the power cable.

According to yet another aspect of the invention,
A power cable comprising a conductor and an insulating layer covering the outer periphery of the conductor,
A hollow portion extending in the axial direction of the conductor is provided in the central portion of the conductor,
A wire made of a material having a higher Young's modulus and a lower coefficient of linear expansion than the material forming the conductor is inserted into the hollow portion of the conductor along the axial direction of the conductor,
In any first cross section perpendicular to the axial direction of the power cable, only a portion of the wire is in contact with the conductor,
In a second cross section different from the first cross section, only part of the wire is in contact with the conductor at a position different from the position where part of the wire is in contact with the conductor in the first cross section. is provided.

According to yet another aspect of the invention,
A method for manufacturing a power cable, comprising: forming a conductor; and forming an insulating layer so as to cover the outer periphery of the conductor,
In the step of forming the conductor,
While forming a hollow portion extending in the axial direction of the conductor at the center of the conductor,
inserting a wire made of a material having a higher Young's modulus and a lower coefficient of linear expansion than the material forming the conductor into the hollow portion of the conductor along the axial direction of the conductor;
A method for manufacturing a power cable in which the filling rate of the wire rod, which is the ratio of the cross-sectional area of the wire rod to the cross-sectional area of the hollow portion in an arbitrary cross section orthogonal to the axial direction of the power cable, is 20% or more and 90% or less. provided.

According to yet another aspect of the invention,
A conductor and an insulating layer covering the outer periphery of the conductor, a hollow portion extending in an axial direction of the conductor is provided at the center of the conductor, and the conductor is configured in the hollow portion of the conductor. a pair of power cables in which a wire made of a material having a higher Young's modulus and a lower coefficient of linear expansion than the material is inserted along the axial direction of the conductor;
a stopper fixed to the tip of the wire pulled out from the hollow portion of the conductor of each of the pair of power cables and restricting extension of the conductor in the axial direction;
a sleeve configured as a metal cylindrical body, inserted so that the ends of the conductors of each of the pair of power cables are opposed to each other with the stoppers fixed, and compressively connecting the pair of conductors;
A power cable connection structure is provided.

According to yet another aspect of the invention,
A conductor and an insulating layer covering the outer periphery of the conductor, a hollow portion extending in an axial direction of the conductor is provided at the center of the conductor, and the conductor is configured in the hollow portion of the conductor. A step of preparing a pair of power cables in which a wire composed of a material having a larger Young's modulus and a smaller linear expansion coefficient than the material is inserted along the axial direction of the conductor;
a step of pulling out the tip of the wire from the hollow portion of each of the conductors of the pair of power cables, and fixing a stopper to the tip of each of the wires for restricting extension of the conductor in the axial direction;
The ends of the conductors of each of the pair of power cables are inserted into a sleeve configured as a metal cylindrical body so as to face each other with the stopper fixed, and the sleeve is compressed from the outside. thereby compressively connecting the pair of conductors together;
There is provided a method for connecting a power cable comprising:

ADVANTAGE OF THE INVENTION According to this invention, the extension amount of the laying direction of a power cable can be made small.

(a) is a schematic cross-sectional view orthogonal to the axial direction of a power cable according to an embodiment of the present invention, and (b) is a schematic cross-sectional view enlarging the central portion of the power cable shown in (a). . FIG. 2 is a schematic cross-sectional view along the axial direction of the power cable when the power cable according to one embodiment of the present invention is energized; 1 is a schematic cross-sectional view showing an installed state of a power cable according to one embodiment of the present invention; FIG. FIG. 4 is a schematic cross-sectional view along the axial direction of the power cables, showing the connecting portion of the pair of power cables; (a) is a schematic cross-sectional view enlarging the central portion of the power cable of Modification 1 of the embodiment of the present invention, and (b) is the center of the power cable of Modification 2 of the embodiment of the present invention; It is the schematic sectional drawing which expanded the part. (a) is a schematic cross-sectional view enlarging the central portion of the power cable of Modification 3 of the embodiment of the present invention, and (b) is the center of the power cable of Modification 4 of the embodiment of the present invention; It is the schematic sectional drawing which expanded the part. (a) is a schematic cross-sectional view enlarging the central portion of the power cable of Modification 5 of the embodiment of the present invention, and (b) is the center of the power cable of Modification 6 of the embodiment of the present invention. It is the schematic sectional drawing which expanded the part. It is the schematic which expanded the center part in the power cable of the modification 7 of one Embodiment of this invention. (a) is a schematic cross-sectional view enlarging the central portion of the power cables according to samples 1-5, and (b) is a schematic cross-sectional view enlarging the central portion of the power cables according to samples 6-8. 10 is a graph showing the thermal stress of power cables or the buckling load of conductors with respect to the filling factor of power cables according to samples 1-8.

<Knowledge acquired by the inventors, etc.>
First, the findings obtained by the inventors will be described.

When the conductors of the power cable are energized, the temperature of the power cable rises due to Joule heat. When the temperature of the power cable rises, the power cable expands and extends axially. At this time, the extension amount of the power cable depends on the thermal stress (stress during thermal behavior) generated in the power cable.

Here, the Young's modulus of the power cable is E, the cross-sectional area of the conductor is A, and the linear expansion coefficient of the power cable is α. Then, the thermal stress F occurring in the power cable is obtained by the following formula (1).
F=EAαt (1)

According to the formula (1), the thermal stress F generated in the power cable is proportional to the product Eα of the Young's modulus E of the power cable and the linear expansion coefficient α of the power cable.

The extension amount of the power cable depends on the above-described thermal stress F, the binding force (repellent force) of the power cable at the manhole, and the frictional force due to the weight of the power cable. In other words, since the amount of extension of the power cable depends on the thermal stress F, it depends on the Young's modulus E of the power cable and the linear expansion coefficient α of the power cable.

Next, the thermal stress F described above in the power cable of Patent Document 1 will be considered. In the power cable of Patent Literature 1, as described above, the conductor strands and the Invar wire that form the conductor are tightly twisted. The Invar wire has a coefficient of linear expansion that is smaller than that of the conductor strands that make up the conductor, and a Young's modulus that is larger (higher) than the Young's modulus of the conductor strands that make up the conductor. .

As in the power cable of Patent Document 1, when the conductor element wire and the Invar wire forming the conductor are in close contact, an excessive frictional force is generated between the conductor and the Invar wire, and the conductor and the Invar wire are separated. They will behave as one. When the conductor and the Invar wire are integrated in this way, the coefficient of linear expansion of the power cable approaches that of the Invar wire and decreases, but the Young's modulus of the power cable approaches that of the Invar wire. growing. Therefore, the product Eα of the Young's modulus E of the power cable and the linear expansion coefficient α of the power cable does not decrease, and the thermal stress F of the power cable may increase. As a result, in the power cable of Patent Literature 1, although the Invar wire having a small linear expansion coefficient is inserted into the conductor, there is a possibility that the amount of extension of the power cable cannot be reduced.

Therefore, in order to reduce the extension amount of the power cable, it is important how to adjust the coefficient of linear expansion of the power cable and the Young's modulus of the power cable to reduce the thermal stress of the power cable. The present invention is based on the above knowledge discovered by the inventor.

In the present specification, the term "extension amount of the power cable" means, in other words, the "extension length of the power cable". In addition, a large or small amount of extension of the power cable means, in other words, that the extension length of the power cable is long or short.

<One embodiment of the present invention>
A power cable according to one embodiment of the present invention will be described with reference to FIG. FIG. 1(a) is a schematic cross-sectional view orthogonal to the axial direction of the power cable according to the present embodiment, and FIG. 1(b) is a schematic cross-sectional view enlarging the central portion of the power cable shown in (a). be. Note that the central portion of power cable 10 refers to a portion including conductor 110 and wire 120 . In order to simplify the drawing, hatching outside the central portion of the power cable 10 is omitted.

In addition, hereinafter, the “axial direction” of the power cable 10 means the direction of the central axis of the power cable 10 , and can be rephrased as the longitudinal direction of the power cable 10 . Also, the “radial direction” of the power cable 10 refers to the direction perpendicular to the axial direction of the power cable 10 , and can be rephrased as the lateral direction of the power cable 10 in some cases. Moreover, the “circumferential direction” of the power cable 10 means the direction along the outer circumference of the power cable 10 . The "laying direction" of the power cable 10 refers to the direction in which the power cable 10 is laid along the pipeline, and can be rephrased as the axial direction of the pipeline. The definition of each direction of the members constituting the power cable 10 is the same as the definition of each direction of the power cable 10 described above.

In addition, in this specification, when simply saying “the amount of extension of the power cable 10”, it means the amount of extension of the power cable 10 in the axial direction regardless of whether the power cable 10 is bent or not. are doing. On the other hand, the term “the extension amount of the power cable 10 in the installation direction” means the component of the extension amount of the power cable 10 in the installation direction of the power cable 10 .

As shown in FIG. 1(a), the power cable 10 according to the present embodiment is configured as a so-called CV cable. , an insulating layer 150 , an outer semi-conductive layer 160 , a shielding layer 172 , a pressing tape 174 , a waterproof layer 176 , and a sheath (coating layer) 180 .

Conductor 110 is made of, for example, pure copper (Cu), a copper alloy, pure aluminum (Al), or an aluminum alloy. A wire rod 120 is combined with the conductor 110 . Details of the conductor 110 and the wire rod 120 will be described later.

As another configuration, for example, the binder 130 is made of metal tape and insulating paper such as kraft paper. The inner semi-conductive layer 140 is made of a semi-conductive resin composition containing ethylene-vinyl acetate copolymer and carbon black. The insulating layer 150 is made of a resin composition containing polyethylene as a main component. The outer semiconductive layer 160 is made of the same semiconductive resin composition as the inner semiconductive layer 140 . The shielding layer 172 is configured by combining annealed copper wires or the like. The pressing tape 174 is made of a non-woven fabric tape, a polyester tape, or the like when the waterproof layer 176 is not provided, and is made of a semiconductive tape or the like when the waterproof layer 176 is provided. The waterproof layer 176 is made of aluminum laminate tape or the like. The sheath 180 is made of vinyl chloride or the like.

(Composition of the central part of the power cable)
As shown in FIG. 1(b), the conductor 110 has a plurality of segments 110s formed by twisting a plurality of conductor strands made of pure Cu or the like, for example. Here, for example, the segment 110s is configured in a single layer with respect to the radial direction of the power cable 10, and five segments are provided.

In a cross section perpendicular to the axial direction of the power cable 10, each segment 110s has, for example, a substantially fan shape. Specifically, each segment 110s has an outer peripheral surface 112s, an inner surface 114s, and a pair of side surfaces 116s. In a cross section perpendicular to the axial direction of the power cable 10, the outer peripheral surface 112s has an arc shape that protrudes outward from the center of the segment 110s. The inner surface 114s forms a surface opposite to the outer peripheral surface 112s. In a cross section orthogonal to the axial direction of the power cable 10, the inner surface 114s is, for example, a straight line perpendicular to the center line passing through the center of the segment 110s and the center of the outer peripheral surface 112s. Each of the pair of side surfaces 116s is provided so as to connect the outer peripheral surface 112s and the inner surface 114s. In a cross section orthogonal to the axial direction of the power cable 10, each of the pair of side surfaces 116s is straight along the radial direction of the arc-shaped outer peripheral surface 112s.

In this embodiment, the cross-sectional shapes of the plurality of segments 110s are, for example, equal to each other. That is, the central angles of each segment 110s are equal to each other. This allows the same die to be used to form multiple segments 110s. As a result, the manufacturing cost of power cable 10 can be reduced.

Note that each segment 110s is formed by, for example, twisting a plurality of conductor strands having a circular cross section and passing them through a die. may be substantially arcuate rather than pointed.

The plurality of segments 110s constitute the conductor 110 by being bundled in a ring shape with the side surfaces 116s in contact with each other. An outer peripheral surface 112 s of each of the plurality of segments 110 s forms part of the outer peripheral surface (not shown) of the conductor 110 . In addition, side surfaces 116s of the plurality of segments 110s are arranged along the radial direction of the conductor 110 . In addition, an inner surface 114s of each of the plurality of segments 110s constitutes part of the inner wall 110i of the conductor 110. As shown in FIG.

The multiple segments 110 s are helically twisted in the axial direction of the power cable 10 . The twist direction of the plurality of segments 110s may be the same as or opposite to the twist direction of the conductor strands within each segment 110s.

A hollow portion 110w extending in the axial direction of the conductor 110 is provided at the center of the conductor 110, that is, at the center of the plurality of segments 110s. The hollow portion 110w is formed in a region surrounded by the inner surfaces 114s of the multiple segments 110s. A central axis of the hollow portion 110 w coincides with a central axis of the conductor 110 .

In the present embodiment, the hollow portion 110w is, for example, asymmetrical (point-symmetrical) with respect to the center of the conductor 110 in at least some of the plurality of cross sections orthogonal to the axial direction of the power cable 10. there is Here, for example, the hollow portion 110w is asymmetric with respect to the center of the conductor 110 by providing an odd number of segments 110s that constitute the conductor 110 . More specifically, for example, five segments 110s are provided as described above, and since the central angles of the respective segments 110s are equal to each other, the cross-sectional shape of the hollow portion 110w is a substantially regular pentagon.

In the present embodiment, the hollow portion 110w is, for example, rotationally symmetrical in at least some cross sections among the plurality of cross sections perpendicular to the axial direction of the power cable 10 . Here, for example, since the cross-sectional shape of the hollow portion 110w is a substantially regular pentagon, the hollow portion 110w is five times has rotational symmetry.

Further, in the present embodiment, the cross-sectional shape of the hollow portion 110w is, for example, uniform over the entire length of the power cable 10 in the axial direction. That is, the cross-sectional shape of the hollow portion 110w is asymmetric with respect to the center of the conductor 110 over the entire length of the power cable 10 in the axial direction. The cross-sectional shape of the hollow portion 110w is rotationally symmetrical over the entire length of the power cable 10 in the axial direction.

Note that the cross-sectional shape of the hollow portion 110w is not limited to being uniform over the entire length of the power cable 10 in the axial direction. For example, the cross-sectional shape of the hollow portion 110w in a portion of the cross section perpendicular to the axial direction of the power cable 10 may be different from the cross-sectional shape of the hollow portion 110w in the other portion of the cross section. For example, the cross-sectional shape of the hollow portion 110w may be symmetrical with respect to the center of the conductor 110 in another partial cross-section of the power cable 10 in the axial direction. Further, for example, the cross-sectional shape of the empty portion 110w may be non-rotationally symmetrical in other partial cross-sections in the axial direction of the power cable 10 .

A wire rod 120 is inserted in the hollow portion 110 w of the conductor 110 along the axial direction of the conductor 110 . The wire rod 120 is made of a material that has a Young's modulus larger and a linear expansion coefficient smaller than that of the material that forms the conductor 110 . Since the wire rod 120 is provided in the hollow portion 110w of the conductor 110, a predetermined frictional force is generated between the conductor 110 and the wire rod 120 when the power cable 10 is energized. The extension amount of 10 can be reduced.

The wire rod 120 contains, for example, iron (Fe) and nickel (Ni) at a predetermined ratio, and is preferably made of Invar having a composition ratio of Fe:Ni of 63.5:36.5.
Thereby, the Young's modulus and linear expansion coefficient of the wire rod 120 can be made smaller than the Young's modulus and linear expansion coefficient of the material forming the conductor 110 .

The Young's modulus and coefficient of linear expansion of each constituent material are as follows.
Young's modulus of Cu: 3×10 ³ kgf/mm ²
Coefficient of linear expansion of Cu: 20×10 ⁻⁶ /° C.
Young's modulus of Al: 3.0×10 ³ kgf/mm ²
Al linear expansion coefficient: 23×10 ⁻⁶ /° C.
Young's modulus of Invar: 16.5×10 ³ kgf/mm ²
Linear expansion coefficient of Invar: 3 × 10 ^-6 / ° C.

The wire 120 is formed by twisting a plurality of wires made of Invar and having a circular cross section, for example. The twisting direction of the wire 120 is, for example, the same as at least one of the twisting direction of the conductor wires in each segment 110s and the twisting direction of the plurality of segments 110s. Thereby, the contact area between the conductor 110 and the wire 120 can be increased, and a predetermined frictional force can be easily generated between the conductor 110 and the wire 120 . On the other hand, the twist direction of the wire 120 may be opposite to, for example, the twist direction of the conductor strands within each segment 110s or the twist direction of the plurality of segments 110s. As a result, the contact area between the conductor 110 and the wire rod 120 can be reduced while the conductor 110 and the wire rod 120 are in contact with each other (point contact can be achieved). The former configuration is effective when it is desired to increase the frictional force between the conductor 110 and the wire 120, while the latter configuration is effective when it is desired to suppress an increase in the frictional force between the conductor 110 and the wire 120. effective for Note that the wire 120 is not limited to being composed of a plurality of wires, and may be composed of a single wire.

Moreover, the wire 120 is configured by, for example, uncompressing a plurality of wires.
In other words, the cross-sectional shape of each wire element that constitutes the wire 120 is maintained in a substantially circular shape, and gaps are formed between the plurality of wire elements. Note that the wire 120 is not limited to being configured by uncompressing a plurality of wire materials, and the wire 120 may be configured by compressing a plurality of wire materials.

Moreover, in at least some of the cross sections perpendicular to the axial direction of the power cable 10, the wire rod 120 is in contact with at least one of the multiple segments 110s. In other words, at least part of the outer peripheral surface of the wire 120 is in contact with part of the inner surface 114s of at least one of the plurality of segments 110s.

In this embodiment, the wire 120 is in contact with, for example, a part of the segment 110s positioned vertically below the center of the conductor 110 by its own weight. Here, the wire rod 120 is in contact with, for example, part of one segment 110s that forms the base of the pentagonal hollow portion 110w.

Further, in the present embodiment, the wire rod 120 is in contact with a part of the predetermined segment 110s over the entire axial length of the power cable 10, for example. For example, the wire 120 may be in contact only with the same segment 110s over the entire length of the power cable 10 in the axial direction. On the other hand, since the plurality of segments 110s are twisted as described above, for example, the segment 110s that is in contact with the wire 120 in some cross sections perpendicular to the axial direction of the power cable 10 is in contact with the wire in some other cross sections. 120 may be different from the segment 110s it contacts.

Note that the wire 120 is not limited to being in contact with a portion of the predetermined segment 110s over the entire length of the power cable 10 in the axial direction. For example, in a partial cross section of the power cable 10 in the axial direction, there may be a portion where the wire rod 120 is not in contact with any segment 110s.

Moreover, the wire rod 120 is not limited to being in contact with one segment 110s. For example, wire 120 may be in contact with two or more segments 110 s, or may be in contact with all segments 110 s that make up conductor 110 . The point of contact between the wire 120 and the conductor 110 depends on the shape of the hollow portion 110w, the filling rate of the wire 120, which will be described later, and the like.

On the other hand, in at least some cross sections among the plurality of cross sections orthogonal to the axial direction of the power cable 10, the hollow portion 110w is, for example, between at least one of the plurality of segments 110s and the wire rod 120. It has an air gap 110v. In other words, the wire rod 120 is separated from at least one of the plurality of segments 110s in at least some of the plurality of cross sections perpendicular to the axial direction of the power cable 10, for example. Further, for example, the center of the wire rod 120 is shifted from the center of the conductor 110 in at least some of the cross sections perpendicular to the axial direction of the power cable 10 .

In the present embodiment, the hollow portion 110w has a gap 110v between the wire 120 and four segments 110s other than the one segment 110s with which the wire 120 contacts, for example. In addition, the gap 110v is larger on the side opposite to the segment 110s with which the wire 120 is in contact, with the wire 120 interposed therebetween. In the present embodiment, the hollow portion 110w has the air gap 110v over the entire axial length of the power cable 10, for example.

It should be noted that the hollow portion 110w is not limited to having the void 110v over the entire length of the power cable 10 in the axial direction. For example, the hollow portion 110w may not have the void 110v in a partial cross section of the power cable 10 in the axial direction.

Moreover, the hollow portion 110w is not limited to the case where the void 110v is provided between the wire 120 and the four segments 110s other than the one segment 110s with which the wire 120 contacts.
For example, wire 120 may be in contact with two or more segments 110s, and hollow portion 110w may have gaps 110v between three or less segments 110s and wire 120. FIG. Alternatively, for example, wire 120 may be in contact with all segments 110s, and hollow portion 110w may have gap 110v between a portion of each segment 110s and wire 120. FIG. The size and location of the void 110v depend on the shape of the hollow portion 110w, the filling rate of the wires 120, which will be described later, and the like.

In this embodiment, the plurality of segments 110s that constitute the conductor 110 are, for example, uncompressed. Thereby, the hollow portion 110w can be easily formed in the center of the conductor 110, and the gap 110v can be easily formed between the predetermined segment 110s and the wire rod 120. FIG. In addition, as long as the hollow portion 110w can be formed in the center of the conductor 110, the plurality of segments 110s may be compressed.

Here, in any cross section perpendicular to the axial direction of the power cable 10 of the present embodiment, the filling rate of the wire 120, which is the ratio of the cross-sectional area of the wire 120 to the cross-sectional area of the hollow portion 110w, is, for example, 20% or more and 90%. % or less.

When the filling rate of wire 120 is less than 20%, gap 110v between conductor 110 and wire 120 increases. For this reason, it becomes difficult for friction to occur between the conductor 110 and the wire rod 120, and there is a possibility that the coefficient of linear expansion of the power cable 10 will not be sufficiently reduced. Moreover, if the filling rate of the wire rod 120 is less than 20%, the rigidity of the conductor 110 increases, which may increase the Young's modulus of the power cable 10 . For these reasons, the thermal stress generated in power cable 10 may increase when power cable 10 is energized. As a result, the extension amount of the power cable may increase. Moreover, if the filling rate of the wire 120 is less than 20%, the outer diameter of the conductor 110 becomes large, and the buckling load that causes the conductor 110 to buckle becomes excessively large. Therefore, even if the thermal stress of the power cable 10 tends to increase when the power cable 10 is energized as the filling rate of the wire rod 120 decreases to less than 20%, the thermal stress causes buckling of the conductor 110. There may be cases where it becomes less than the load. That is, it becomes difficult for the conductor 110 to buckle due to the thermal stress of the power cable 10 , and only the conductor 110 becomes difficult to bend with respect to the wire rod 120 . As a result, the amount of extension of the power cable in the installation direction may increase.

Note that if the filling rate of the wire 120 is less than 20%, the outer diameter of the conductor 110 is increased, and the outer diameter of the power cable 10 is increased. For this reason, it becomes difficult to bend the power cable 10, and it may become difficult to insert the power cable 10 into the bent pipeline.

On the other hand, by setting the filling rate of the wire 120 to 20% or more, it is possible to suppress the gap 110v between the conductor 110 and the wire 120 from becoming excessively large. Thereby, a predetermined frictional force can be generated between the conductor 110 and the wire rod 120, and the coefficient of linear expansion of the power cable 10 can be reduced. Further, by setting the filling rate of the wire 120 to 20% or more, the rigidity of the conductor 110 can be optimized. Thereby, an increase in the Young's modulus of power cable 10 can be suppressed. These can reduce the thermal stress generated in the power cable 10 when the power cable 10 is energized. As a result, the amount of extension of the power cable in the laying direction can be sufficiently reduced. Moreover, by setting the filling rate of the wire 120 to 20% or more, the outer diameter of the conductor 110 can be reduced, and the buckling load of the conductor 110 can be reduced. As a result, even if the thermal stress of the power cable 10 tends to decrease when the power cable 10 is energized as the filling rate of the wire rod 120 increases to 20% or more, the thermal stress is reduced by the buckling of the conductor 110 . It can be more than load. That is, the conductor 110 can be buckled by the thermal stress of the power cable 10 , and only the conductor 110 can be bent with respect to the wire rod 120 . As a result, the amount of extension of the power cable in the laying direction can be sufficiently reduced.

Moreover, by setting the filling rate of the wire 120 to 20% or more, the outer diameter of the conductor 110 can be reduced, and an increase in the outer diameter of the power cable 10 can be suppressed. Thereby, the power cable 10 can be easily bent, and the power cable 10 can be easily inserted into the bent pipeline.

On the other hand, when the filling rate of the wire 120 is more than 90%, the gap 110v between the conductor 110 and the wire 120 becomes small, and the conductor 110 is brought into close contact with the wire 120 as in Patent Document 1 described above. get closer. Therefore, when power cable 10 is energized, an excessive frictional force is generated between conductor 110 and wire 120, and conductor 110 and wire 120 behave as one. When the conductor 110 and the wire 120 are integrated in this way, the coefficient of linear expansion of the power cable 10 approaches the coefficient of linear expansion of the wire 120 and becomes smaller, but the Young's modulus of the power cable 10 is equal to that of the wire 120. becomes larger as it approaches . Therefore, the thermal stress generated in power cable 10 may increase when power cable 10 is energized. As a result, the extension amount of the power cable may increase. Further, when the filling rate of the wire 120 is more than 90%, the rigidity of the conductor 110 increases as the Young's modulus of the power cable 10 increases as described above, and the buckling load of the conductor 110 becomes excessive. growing. Therefore, even if the thermal stress of the power cable 10 tends to increase when the power cable 10 is energized as the filling rate of the wire 120 increases to over 90%, the thermal stress is It becomes less than the bending load. That is, it becomes difficult for the conductor 110 to buckle due to the thermal stress of the power cable 10 , and only the conductor 110 becomes difficult to bend with respect to the wire rod 120 . As a result, the amount of extension of the power cable in the installation direction may increase.

On the other hand, by setting the filling rate of the wires 120 to 90% or less, it is possible to suppress the gap 110v between the conductors 110 and the wires 120 from becoming excessively small. Accordingly, when power cable 10 is energized, conductor 110 and wire 120 can be deformed relative to each other while generating a predetermined frictional force between conductor 110 and wire 120 . As a result, the coefficient of linear expansion of power cable 10 can be reduced to approach the coefficient of linear expansion of wire 120, while the Young's modulus of power cable 10 can be suppressed from increasing to approach the Young's modulus of the wire. Thus, the thermal stress generated in power cable 10 when power cable 10 is energized can be reduced. As a result, the extension amount of the power cable can be sufficiently reduced. In addition, by setting the filling rate of the wire 120 to 90% or less, the increase in the Young's modulus of the power cable 10 can be suppressed as described above, and the rigidity of the conductor 110 can be reduced. Buckling load can be reduced. As a result, even if the thermal stress of the power cable 10 tends to decrease when the power cable 10 is energized as the filling rate of the wire rod 120 decreases to 90% or less, the thermal stress is reduced by the buckling of the conductor 110. It can be more than load. That is, the conductor 110 can be buckled by the thermal stress of the power cable 10 , and only the conductor 110 can be bent with respect to the wire rod 120 . As a result, the amount of extension of the power cable in the laying direction can be sufficiently reduced.

In addition, it is more preferable that the filling rate of the wire 120 is, for example, 30% or more and 85% or less. As a result, the amount of extension of the power cable (especially the amount of extension of the power cable 10 in the laying direction) can be stably reduced.

By setting the filling rate of the wire 120 to 20% or more and 90% or less as described above, for example, the thermal stress generated in the power cable 10 when the difference between the temperature of the conductor 110 of the power cable 10 and the base temperature is 65 ° C. is greater than or equal to the buckling load at which the conductor 110 buckles when both ends of the power cable 10 having a length of 6000 mm are fixed. Here, "when the difference between the temperature of the conductor 110 of the power cable 10 and the base temperature is 65°C" is when the continuous current flowing through the power cable 10 installed in the pipeline is the maximum allowable current. It is the difference between the permissible temperature of the conductor 110 of 90° C. and the base temperature (soil temperature) of 25° C., and corresponds to the temperature change width at which the amount of extension of the power cable 10 is maximized. Further, "when both ends of the power cable 10 having a length of 6000 mm are fixed" corresponds to the case where the power cable 10 is laid with both ends fixed in a pipeline having a joint distance of 6000 mm. In other words, by making the thermal stress of the power cable 10 equal to or greater than the buckling load of the conductor 110 under the above conditions, the conductor 110 can be flexed in at least one or more locations between the joints of the pipeline. As a result, it is possible to sufficiently reduce the amount of extension of the power cable 10 in the laying direction between the joints of the pipeline.

Next, a conventional power cable without the hollow portion 110w and the wire 120 is referred to as a "reference power cable". Compare thermal stress. The cross-sectional area of the conductor of the reference power cable is equal to the cross-sectional area of the conductor 110 of the power cable 10 of this embodiment, and other configurations are the same as those of the power cable 10 of this embodiment.

In this embodiment, the Young's modulus of the power cable 10 is E, the cross-sectional area of the conductor 110 is A, and the linear expansion coefficient of the power cable 10 is α. Assuming that the power cable 10 is energized and the temperature of the power cable 10 rises from normal temperature by the temperature difference t, the thermal stress F generated in the power cable 10 according to the present embodiment is expressed as F=EAαt by the above-described formula (1). Become.

On the other hand, regarding the reference power cable, the Young's modulus of the reference power cable is E ₀ , the cross-sectional area of the conductor is A ₀ , and the linear expansion coefficient of the reference power cable is α ₀ . Assuming that the temperature of the reference power cable rises from normal temperature by the temperature difference t, the thermal stress F0 occurring in the reference power cable is obtained by the following equation ( ₂ ).
F ₀ =E ₀ A ₀ α ₀ t (2)

A thermal stress ratio R, which is the ratio of the thermal stress F of the power cable 10 of the present embodiment to the thermal stress F0 of the reference power cable, is obtained by the following equation (3) from A _{= A0} .
R=F/F0 _{= Eα} / _E0α0 (3)

In this embodiment, for example, the thermal stress ratio R is less than ₁ because the thermal stress F of the power cable 10 is smaller than the thermal stress F0 of the reference power cable.

When the thermal stress ratio R is 1 or more, the extension amount of the power cable 10 becomes larger than the extension amount of the reference power cable. That is, in this state, the effect of restraining the extension of the power cable 10 by providing the wire rod 120 inside the conductor 110 of the power cable 10 cannot be obtained. On the other hand, by setting the thermal stress ratio R to less than 1, that is, by making the thermal stress of the power cable 10 smaller than the thermal stress of the reference power cable, the extension amount of the power cable 10 is equal to the extension of the reference power cable. can be smaller than the quantity. That is, it is possible to sufficiently obtain the effect of suppressing the extension of the power cable 10 by providing the wire 120 inside the conductor 110 of the power cable 10 .

Note that the lower the thermal stress ratio R, the smaller the amount of extension of the power cable 10, which is preferable. However, since the Young's modulus and coefficient of linear expansion are limited depending on the type of wire 120, the lower limit of the thermal stress ratio R may be, for example, about 0.8.

In the present embodiment, the linear expansion coefficient α of the power cable 10 can be made smaller than the linear expansion coefficient α ₀ of the reference power cable by setting the filling rate of the wire 120 to 20% or more and 90% or less. , the Young's modulus E of the power cable 10 can be ₁ to 1.2 times the Young's modulus E0 of the reference power cable. As a result, the thermal stress ratio R can be made less than one.

Since the coefficient of linear expansion α of the power cable 10 is never less than the coefficient of linear expansion of the wire 120 , the lower limit of the coefficient of linear expansion α of the power cable 10 is about the coefficient of linear expansion of the wire 120 .

Further, in the present embodiment, the ratio of the cross-sectional area of the wire 120 to the cross-sectional area A of the conductor 110 (hereinafter referred to as the cross-sectional area ratio of the wire 120) is, for example, 4% or more and 10% or less. If the cross-sectional area ratio of the wire 120 is less than 4%, the linear expansion coefficient α of the power cable 10 may not be sufficiently reduced. On the other hand, by setting the cross-sectional area ratio of the wire rod 120 to 4% or more, the linear expansion coefficient α of the power cable 10 can be brought close to the linear expansion coefficient of the wire rod 120 and sufficiently reduced. On the other hand, when the cross-sectional area ratio of wire 120 is more than 10%, Young's modulus E of power cable 10 approaches the Young's modulus of wire 120 and increases. On the other hand, by setting the cross-sectional area ratio of the wire rod 120 to 10% or less, it is possible to suppress the Young's modulus of the power cable 10 from approaching the Young's modulus of the wire rod. That is, an increase in Young's modulus of power cable 10 can be suppressed. In this way, by setting the cross-sectional area ratio of the wire 120 to 4% or more and 10% or less, the linear expansion coefficient α of the power cable 10 is made smaller than the linear expansion coefficient α ₀ of the reference power cable. The Young's modulus E can be ₁ to 1.2 times the Young's modulus E0 of the reference power cable.

(2) When Electric Power Cable is Energized Next, with reference to FIG. 2, the case when the electric power cable 10 of the present embodiment is energized will be described. FIG. 2 is a schematic cross-sectional view along the axial direction of the power cable when the power cable according to the present embodiment is energized. Note that FIG. 2 shows only the conductor 110 and the wire rod 120 .

When conductor 110 of power cable 10 is energized, the temperature of power cable 10 rises due to Joule heat. When the temperature of power cable 10 rises, power cable 10 expands and power cable 10 extends in the axial direction. At this time, since the coefficient of linear expansion of the conductor 110 is larger than that of the wire 120 , the amount of extension of the conductor 110 is larger than the amount of extension of the wire 120 .

Here, in the present embodiment, as described above, by setting the filling rate of the wire 120 to 20% or more and 90% or less, when the conductor 110 of the power cable 10 is energized, the conductor 110 and the wire 120 The conductor 110 and the wire rod 120 can be deformed relative to each other while generating a predetermined frictional force therebetween.

Thereby, as shown in FIG. 2 , when the conductor 110 of the power cable 10 is energized, only the conductor 110 can be bent in a meandering manner with respect to the wire 120 . For example, only the conductor 110 can spirally meander with respect to the wire 120 . At this time, the insulating layer 150 and the like provided on the outer periphery of the conductor 110 may meander so as to follow the shape of the conductor 110, and the power cable 10 as a whole may meander.

In this way, by bending only the conductor 110 in a meandering manner with respect to the wire rod 120, the component in the direction orthogonal to the laying direction of the power cable 10, out of the extension amount of the conductor 110, is increased. The component in the installation direction of the power cable 10 can be reduced. In other words, part of the extension of the conductor 110 in the direction in which the power cable 10 is laid can be absorbed by the component in the direction orthogonal to the direction in which the power cable 10 is laid. As a result, the extension amount in the laying direction of the power cable 10 as a whole can be reduced.

At this time, in the present embodiment, the wire rod 120 is in contact with at least one of the plurality of segments 110s in at least some of the plurality of cross sections perpendicular to the axial direction of the power cable 10, for example. ing. Thereby, when the power cable 10 is energized, a predetermined frictional force can be generated between the wire 120 and the segment 110s with which the wire 120 is in contact.

On the other hand, at this time, in the present embodiment, at least one of the plurality of segments 110s is, for example, at least one of the plurality of segments 110s in at least some of the plurality of cross sections perpendicular to the axial direction of the power cable 10. There is a gap 110v between one and the wire rod 120 . Since the gap 110v is interposed between the predetermined segment 110s and the wire 120, the frictional force between the segment 110s and the wire 120 can be reduced when the power cable 10 is energized. As a result, it is possible to suppress the extension of the segment 110s in contact with the wire rod 120 as described above, while permitting the extension of the segment 110s with the gap 110v between the wire rod 120 and the wire rod 120 to extend. As a result, only the conductor 110 can be easily meandered with respect to the wire 120 .

Moreover, since the gap 110v is interposed between the predetermined segment 110s and the wire 120, only the conductor 110 can be bent with respect to the wire 120 so that the wire 120 enters toward the gap 110v. For example, only the conductor 110 is bent with respect to the wire 120 so that the wire 120 enters the gap 110v, which is larger on the side opposite to the segment 110s with which the wire 120 is in contact. be able to. Thus, the gap 110v between the wire 120 and the segment 110s can promote the bending of only the conductor 110 with respect to the wire 120. FIG.

At this time, in the present embodiment, the hollow portion 110w is, for example, asymmetrical with respect to the center of the conductor 110 in at least some of the plurality of cross sections perpendicular to the axial direction of the power cable 10 . Regardless of which of the segments 110 s the wire 120 is in contact with, the arrangement of contacts between the wire 120 and the segments 110 s is asymmetric with respect to the center of the conductor 110 . Thereby, when the power cable 10 is energized, a predetermined frictional force can be generated asymmetrically with respect to the center of the power cable 10 between the conductor 110 and the wire rod 120 . As a result, only the conductor 110 can be easily bent so as to meander with respect to the wire 120 .

Further, at this time, in the present embodiment, the hollow portion 110w is, for example, rotationally symmetrical in at least some cross sections among the plurality of cross sections perpendicular to the axial direction of the power cable 10 . Even if the wire 120 is in contact with any of the plurality of segments 110s, the points of contact between the conductor 110 and the wire 120 when viewed from the axial direction of the power cable 10 are distributed at predetermined angles in the circumferential direction of the conductor 110. be able to. Thereby, when the power cable 10 is energized, only the conductor 110 can be meandered regularly (for example, at a predetermined cycle) with respect to the wire 120 . As a result, the extension amount of the power cable 10 can be easily predicted.

It should be noted that the portion where only the conductor 110 is meanderingly bent with respect to the wire 120 does not have to extend over the entire length of the power cable 10 . For example, in at least a part of the power cable 10 in the axial direction, the stress between the conductor 110 with a large amount of extension and the wire 120 with a small amount of extension is balanced, and there is a portion where the wire 120 and the conductor 110 are not bent. may be

(3) Method for Manufacturing Power Cable Next, a method for manufacturing the power cable 10 according to the present embodiment will be described.

First, for example, a plurality of wires made of Invar and having a circular cross section are prepared. After preparing the plurality of wires, the wires 120 are formed by twisting the plurality of wires. At this time, the wires 120 are formed by making the plurality of wires uncompressed.

At this time, since the cross-sectional area of the conductor 110 is determined by the specifications of the power cable 10 to be manufactured, the cross-sectional area (thickness) of the wire 120 is adjusted according to the cross-sectional area of the conductor 110 .
Here, the wire rod 120 is formed so that the ratio of the cross-sectional area of the wire rod 120 to the cross-sectional area of the conductor 110 is, for example, 4% or more and 10% or less.

Also, a plurality of conductor strands made of Cu or the like are prepared. After preparing a plurality of conductor strands, a plurality of segments 110s constituting the conductor 110 are formed by passing the plurality of conductor strands through a die having a predetermined opening while twisting the plurality of conductor strands. At this time, the twisted conductor strands are gradually compressed with a die to be molded. Specifically, for example, 6 conductor strands are twisted on one conductor strand and compressed with a die, 12 conductor strands are twisted together and compressed with a die, and further 18 conductor strands are twisted thereon and compressed with a die. In this manner, the cross-sectional shape of each segment 110s is substantially fan-shaped.

The conductor 110 is then formed by twisting a plurality of segments 110s. At this time, a hollow portion 110w extending in the axial direction of the conductor 110 is formed at the center of the plurality of segments 110s that constitute the conductor 110, and a wire rod 120 is formed in the hollow portion 110w of the conductor 110 along the axial direction of the conductor 110. insert

At this time, the hollow portion 110 w is formed so as to be asymmetrical with respect to the center of the conductor 110 in at least a part of the plurality of cross sections orthogonal to the axial direction of the conductor 110 . In this embodiment, for example, by forming the conductor 110 with five segments 110s, the hollow portion 110w having a substantially regular pentagonal cross section is formed.

At this time, the wire rod 120 is brought into contact with at least one of the segments 110 s in at least some of the multiple cross sections perpendicular to the axial direction of the conductor 110 . In this embodiment, for example, the wire rod 120 is brought into contact with a portion of one segment 110s that forms the base of the pentagonal hollow portion 110w.

At this time, a gap 110v is interposed between at least one of the plurality of segments 110s and the wire rod 120 in at least some of the plurality of cross sections perpendicular to the axial direction of the conductor 110 . In this embodiment, for example, a gap 110v is interposed between the wire 120 and the four segments 110s other than the one segment 110s with which the wire 120 contacts.

Also, at this time, after each of the plurality of segments 110s is gradually compressed using each of the plurality of dies, when the plurality of segments 110s are twisted together, the combination of shapes of the plurality of segments 110s is made uniform in the axial direction. A die is used to twist a plurality of segments 110s together to form a set.

At this time, the conductor 110 is formed by uncompressing and twisting the plurality of segments 110s.

In this way, in an arbitrary cross section orthogonal to the axial direction of the power cable 10, the filling rate of the wire 120, which is the ratio of the cross-sectional area of the wire 120 to the cross-sectional area of the hollow portion 110w, is 20% or more and 90% or less. , a plurality of segments 110s are twisted together.

At this time, while forming the conductor 110 by twisting the plurality of segments 110 s, the binder 130 is wound so as to cover the outer periphery of the conductor 110 . Thereby, the plurality of segments 110 s are bundled with the binder 130 .

Next, the inner semiconductive layer 140, the insulating layer 150, and the outer semiconductive layer 160 are sequentially or simultaneously extruded outward from the center so as to cover the outer periphery of the conductor 110, thereby forming a cable core. (Power cable intermediate) is formed. Next, the polyethylene in the insulating layer 150 is cross-linked by putting the cable core into a heating furnace heated to a predetermined cross-linking temperature. Next, the shielding layer 172 is formed by covering the outer periphery of the outer semiconducting layer 160 with an annealed copper wire. Next, the pressing tape 174 is wrapped around the outer circumference of the shielding layer 172 . Next, a waterproof layer 176 is formed by winding an aluminum tape around the outer periphery of the pressing tape 174 . Next, a sheath 180 is further extruded around the perimeter of the impervious layer 176 .

As described above, the power cable 10 according to this embodiment is manufactured.

(4) Power cable connection method (installation method)
Next, a connection method (laying method) of the power cable 10 according to the present embodiment will be described with reference to FIGS. 3 and 4. FIG.

Here, as shown in FIG. 3, manholes (manholes) 940 are provided at predetermined intervals in the ground, and a pipeline 920 is provided between the pair of manholes 940 . Below, the case where the existing OF cable provided in the pipeline 920 and the manhole 940 is replaced with the power cable 10 of this embodiment, for example is demonstrated.

First, the power cable 10 according to the present embodiment is prepared by the manufacturing method described above.

Next, the existing OF cable (not shown) is removed from conduit 920 and manhole 940 .

Next, a pooling eye is attached to the tip of the power cable 10 of this embodiment. After attaching the pooling eye, a wire that has been passed through the conduit 920 in advance is connected to the tip of the pooling eye. After the wires are connected, the power cable 10 is passed through the conduit 920 by pulling the wires with a winch.

After inserting the power cable 10 into the conduit 920 , the offset portion 30 is formed by bending the power cable 10 in an S shape inside the manhole 940 . The power cable 10 is passed through the conduit 920 on the opposite side of the manhole 940 in the same manner as described above, and the offset portion 30 is formed.

After the power cable 10 is inserted into each of the pair of conduits 920 facing each other across the manhole 940 as described above, one of the pair of power cables 10 facing each other across the manhole 940 is extended by the inner core. An insulating cylinder 230 having a diameter is covered.

Next, the conductors 110 are exposed by stripping off the insulating layer 150 and the like at the ends of the pair of power cables 10 .

After the conductors 110 are exposed at the ends of the pair of power cables 10, the ends of the wires 120 are pulled out from the ends of the conductors 110, respectively. At this time, since the filling rate of the wire 120 is 20% or more and 90% or less, the tip of the wire 120 can be easily pulled out from the hollow portion 110w of the conductor 110 .

Here, as shown in FIG. 4, in each of the pair of power cables 10, when the wires 120 are pulled out by a predetermined length from the hollow portions 110w of the conductors 110, stoppers 220 are fixed to the ends of the wires 120, respectively. The stopper 220 is configured as, for example, a cylindrical member (ring-shaped member) made of metal, and is fixed to the tip of the wire 120 by being compressed while the tip of the wire 120 is inserted. ing. Also, the diameter of the stopper 220 is larger than the diameter of the hollow portion 110 w of the conductor 110 . In this way, by fixing the stopper 220 to the tip of the wire 120 in each of the pair of power cables 10, the extension of the conductor 110 in the axial direction with respect to the wire 120 is prevented when the power cable 10 is energized. can be regulated by

Next, a sleeve 210 configured as a metallic tubular body is prepared, and the tips of the conductors 110 of the pair of power cables 10 are placed in the sleeve 210 so as to face each other with the stoppers 220 fixed. insert into By compressing the sleeve 210 from the outside in this state, the pair of conductors 110 are compression-connected.

Next, the insulating cylinder 230 covering one of the pair of power cables 10 is moved to a position covering the connecting portion between the pair of conductors 110 . After the insulating cylinder 230 is moved to the predetermined position, the inner core that expands the insulating cylinder 230 is removed to reduce the diameter of the insulating cylinder 230 . Thereby, the insulating tube 230 is fixed to the connecting portion of the pair of power cables 10 .

As described above, the connection structure 20 for the power cable 10 according to the present embodiment is constructed.

(5) Effects According to the Present Embodiment According to the present embodiment, one or more of the following effects can be obtained.

(a) A wire rod 120 made of a material having a larger Young's modulus and a smaller linear expansion coefficient than the material forming the conductor 110 is inserted into a hollow portion 110w provided in the center of the conductor 110 . In an arbitrary cross section orthogonal to the axial direction of power cable 10, the filling rate of wire 120, which is the ratio of the cross-sectional area of wire 120 to the cross-sectional area of hollow portion 110w, is 20% or more and 90% or less. As a result, a predetermined frictional force is generated between the conductor 110 and the wire 120, and the coefficient of linear expansion of the power cable 10 can be made closer to the coefficient of linear expansion of the wire 120 to be smaller.
Also, by setting the filling rate of the wire 120 within the above range, an increase in the Young's modulus of the power cable 10 can be suppressed. As a result, the thermal stress of the power cable 10 when the power cable 10 is energized can be reduced, and the extension amount of the power cable 10 can be sufficiently reduced.

(b) By setting the filling rate of the wire 120 within the above range, the conductor 110 and the wire 120 can be deformed relative to each other while generating a predetermined frictional force between the conductor 110 and the wire 120. can. Thereby, when the conductor 110 of the power cable 10 is energized, only the conductor 110 can be bent so as to meander with respect to the wire rod 120 . By bending only the conductor 110 in a meandering manner with respect to the wire 120, the component in the direction perpendicular to the installation direction of the power cable 10 is increased in the amount of extension of the conductor 110, while the power cable 10 is increased. The component in the laying direction can be reduced. As a result, the extension amount in the laying direction of the power cable 10 as a whole can be reduced.

(c) By setting the filling rate of the wire 120 within the above range, the thermal stress generated in the power cable 10 when the difference between the temperature of the conductor 110 of the power cable 10 and the base temperature is 65 ° C. The buckling load that causes the conductors 110 to buckle when both ends of the power cable 10 are fixed can be made greater than or equal to the buckling load. In other words, the conductor 110 can be flexed in at least one or more locations between the joints of the pipeline. As a result, it is possible to sufficiently reduce the amount of extension of the power cable 10 in the laying direction between the joints of the pipeline.

(d) By setting the thermal stress ratio R obtained by R _{= Eα} /E0α0 to less than 1, that is, by making the thermal stress of the power cable 10 smaller than that of the reference power cable, The amount of extension can be made smaller than the amount of extension of the reference power cable.
That is, it is possible to sufficiently obtain the effect of suppressing the extension of the power cable 10 by providing the wire 120 inside the conductor 110 of the power cable 10 .

(e) By reducing the extension amount of the power cable 10, the extension amount of the power cable 10 from the conduit 920 to the manhole 940 can be reduced. Here, the extension of the power cable 10 from the conduit 920 can be absorbed by the deformation of the offset portion 30 . The bending radius of the offset portion 30 decreases as the amount of extension of the power cable 10 from the conduit 920 increases. The allowable bending radius of the offset portion 30 is set to, for example, 10D or more, where D is the outer diameter of the power cable 10 . In the present embodiment, by reducing the extension amount of the power cable 10 from the conduit 920 to the manhole 940, the bending radius of the offset portion 30 can be maintained at the allowable bending radius or more.

(f) By reducing the amount of extension of the power cable 10, it is possible to sufficiently ensure a region in which thermal expansion and contraction does not occur even if temperature changes occur, that is, a so-called dead region. This makes it difficult for the power cable 10 to slide down even when the pipeline 920 is inclined. Therefore, for example, it is not necessary to attach a slip prevention device or the like to the power cable 10 to prevent it from slipping down using a spring, weight, or the like in the manhole 940, and the power cable 10 can be laid even if the manhole 940 is small. It becomes possible.

(g) By reducing the extension amount of the power cable 10, the power cable 10 can be easily replaced with an existing OF cable.

Here, the extension amount of the conventional CV cable (reference power cable) is larger than that of the OF cable, as described above. Therefore, when a conventional CV cable is replaced with an existing OF cable, there is a possibility that the bending radius of the offset portion may become smaller than the allowable bending radius set for the existing line due to extension during energization. In addition, there is a possibility that slipping down in the inclined pipeline is more likely to occur. Therefore, when laying a conventional CV cable on a track, the manhole must be widened so that the bending radius of the offset portion when energized is greater than the allowable bending radius, and so that a slip prevention device can be installed. I had to. As described above, it was difficult to lay the conventional CV cable on the track where the OF cable was already installed.

On the other hand, in the present embodiment, the extension amount of the power cable 10 during energization can be equal to or less than the extension amount of the OF cable. Thereby, when the existing OF cable is replaced with the power cable 10 according to the present embodiment, the bending radius of the offset portion can be kept equal to or greater than the allowable bending radius set for the existing line. In addition, it is possible to suppress sliding down in the slanted pipeline 920 . Furthermore, there is no need to enlarge manhole 940 . As a result, the power cable 10 according to this embodiment can be easily replaced with an existing OF cable.

In addition, in the present embodiment, the power cable 10 can be replaced with an existing OF cable, so that the cross-sectional area of the conductor 110 of the power cable 10 can be reduced to include, for example, a hollow tube that serves as a path for oil in the OF cable. It can be enlarged to equal the cross-sectional area of the conductor.
Thereby, the power transmission capacity of the power cable 10 according to the present embodiment can be made larger than the power transmission capacity of the OF cable.

Furthermore, in this embodiment, since the power cable 10 can be replaced with the existing OF cable, it is possible to eliminate the lubricating facility attached to the OF cable from the track. That is, the maintenance cost of the power cable 10 can be reduced.

(h) In the power cable 10 of the present embodiment, the conductor 110 has a plurality of segments 110s formed by twisting a plurality of conductor strands, so that the wire rod 120 is inserted into the center of the plurality of segments 110s. The hollow portion 110w can be easily formed.

(i) Wire rod 120 is in contact with at least one of segments 110 s in at least some of the multiple cross sections perpendicular to the axial direction of power cable 10 . Thereby, when the power cable 10 is energized, a predetermined frictional force can be generated between the wire 120 and the segment 110s with which the wire 120 is in contact.

(j) In at least some cross sections among the plurality of cross sections perpendicular to the axial direction of the power cable 10, the hollow portion 110w has a gap 110v between at least one of the plurality of segments 110s and the wire rod 120. have. Since the gap 110v is interposed between the predetermined segment 110s and the wire 120, the frictional force between the segment 110s and the wire 120 can be reduced when the power cable 10 is energized. As a result, it is possible to suppress the extension of the segment 110s in contact with the wire rod 120 as described above, while permitting the extension of the segment 110s with the gap 110v between the wire rod 120 and the wire rod 120 to extend. As a result, only the conductor 110 can be easily meandered with respect to the wire 120 .

Moreover, since the gap 110v is interposed between the predetermined segment 110s and the wire 120, only the conductor 110 can be bent with respect to the wire 120 so that the wire 120 enters toward the gap 110v. That is, the gap 110v between the wire 120 and the segment 110s can promote the bending of the conductor 110 alone with respect to the wire 120. FIG.

(k) Hollow portion 110w is asymmetric with respect to the center of conductor 110 in at least some of the plurality of cross sections perpendicular to the axial direction of power cable 10 . Regardless of which of the segments 110 s the wire 120 is in contact with, the arrangement of contacts between the wire 120 and the segments 110 s is asymmetric with respect to the center of the conductor 110 . Thereby, when the power cable 10 is energized, a predetermined frictional force can be generated asymmetrically with respect to the center of the power cable 10 between the conductor 110 and the wire rod 120 . As a result, only the conductor 110 can be easily bent so as to meander with respect to the wire 120 .

(l) At the tip of the power cable 10, the wire rod 120 can be pulled out from the hollow portion 110w of the conductor 110 by a predetermined length. As a result, the ends of the wires 120 can be pulled out from the hollow portions 110w of the conductors 110 of the pair of power cables 10, and the stoppers 220 can be fixed to the ends of the wires 120. As shown in FIG. As a result, when the power cable 10 is energized, the extension of the conductor 110 in the axial direction with respect to the wire 120 can be restricted by the stopper 220 .

In particular, by setting the filling rate of the wire 120 to 90% or less, the wire 120 can be easily pulled out from the hollow portion 110w of the conductor 110 . Thereby, the workability at the installation site of the power cable 10 can be improved.

(6) Modifications of the present embodiment The present embodiment is not limited to the above aspect, and can be modified as in the following modifications. Hereinafter, only elements different from the above-described embodiment will be described, and elements that are substantially the same as those described in the above-described embodiment will be given the same reference numerals, and descriptions thereof will be omitted.

(Modification 1)
FIG. 5(a) is a schematic cross-sectional view enlarging the central portion of the power cable of Modification 1. FIG.
In Modification 1 shown in FIG. 5A, an even number of segments 110s are provided. Also, less than five segments 110s are provided. Specifically, four segments 110s are provided, for example.

In this modification, the hollow portion 110w is, for example, symmetrical with respect to the center of the conductor 110 in at least some of the plurality of cross sections perpendicular to the axial direction of the power cable 10 . Specifically, for example, the four segments 110s are provided as described above, and the central angles of the respective segments 110s are equal to each other, so the cross-sectional shape of the hollow portion 110w is substantially square.

In this modified example, the wire rod 120 is in contact with, for example, a part of each of a pair of segments 110s that are vertically adjacent to the center of the conductor 110 . In addition, the hollow portion 110w has a gap 110v between the wire 120 and two segments 110s other than the pair of segments 110s with which the wire 120 is in contact.

According to Modification 1, hollow portion 110 w is symmetrical with respect to the center of conductor 110 in at least some of the plurality of cross sections orthogonal to the axial direction of power cable 10 . Thereby, when the power cable 10 is energized, a predetermined frictional force can be generated between the conductor 110 and the wire rod 120 with good balance with respect to the center or the centerline of the conductor 110 . As a result, only the conductor 110 can be regularly bent with respect to the wire 120 . Therefore, this modification is effective, for example, when it is desired to limit the bending direction of the conductor 110 to only a predetermined direction among the directions perpendicular to the laying direction of the power cable 10 .

(Modification 2)
FIG. 5(b) is a schematic cross-sectional view enlarging the central portion of the power cable of Modification 2. As shown in FIG.
In modification 2 shown in FIG. 5(b), more than five segments 110s are provided. Specifically, six segments 110s are provided, for example.

In this modified example, for example, six segments 110s are provided as described above, and since the central angles of the respective segments 110s are equal to each other, the cross-sectional shape of the hollow portion 110w is a substantially regular hexagon.

In this modification, the wire 120 is in contact with, for example, part of one segment 110s that forms the base of the hexagonal hollow portion 110w. Further, the hollow portion 110w has a gap 110v between the wire 120 and five segments 110s other than the segment 110s with which the wire 120 contacts.

According to Modification 2, since more than five segments 110s are provided, the rigidity per segment 110s can be reduced. Thereby, when the power cable 10 is energized, each segment 110s can be easily deformed.
As a result, only the conductor 110 can be easily bent so as to meander with respect to the wire rod 120 .

Further, according to Modification 2, since more than five segments 110s are provided, if the filling rate of the wire rod 120 is increased, the points of contact between the conductor 110 and the wire rod 120 (the number of segments 110s in contact with the wire rod 120 ) can be increased. Thereby, the frictional force between the conductor 110 and the wire rod 120 can be easily increased.

(Modification 3)
FIG. 6A is a schematic cross-sectional view enlarging the central portion of the power cable of Modification 3. FIG.
In Modified Example 3 shown in FIG. 6( a ), hollow portion 110 w is, for example, rotationally asymmetric in at least some cross sections among a plurality of cross sections orthogonal to the axial direction of power cable 10 .

Specifically, in at least some of the plurality of cross sections perpendicular to the axial direction of the power cable 10, the cross-sectional shape of at least one segment 110s of the plurality of segments 110s is the cross-sectional shape of the other segment 110s. different in shape. Here, for example, each of the five segments 110s has a different cross-sectional shape. Also, for example, in a cross section orthogonal to the axial direction of the power cable 10, the cross-sectional shape of at least one of the five segments 110s is relative to the center line passing through the center of the segment 110s and the center of the arc-shaped outer peripheral surface 112s. are asymmetrical. Further, for example, in a cross section perpendicular to the axial direction of the power cable 10, at least one inner surface 114s of the five segments 110s is perpendicular to the center line passing through the center of the segment 110s and the center of the outer peripheral surface 112s. are inclined in different directions from each other. With such a configuration, the hollow portion 110 w is rotationally asymmetric with respect to the center of the conductor 110 .

In addition, in this modification, for example, in at least some cross sections among the plurality of cross sections orthogonal to the axial direction of the power cable 10, the gap 110v is on the opposite side of the segment 110s with which the wire 120 is in contact with the wire 120 therebetween. The rest is large.

According to Modified Example 3, hollow portion 110w is, for example, rotationally asymmetric in at least some of the plurality of cross sections perpendicular to the axial direction of power cable 10 . The contact points between the conductor 110 and the wire rod 120 when viewed from the axial direction of the power cable 10 are irregularly distributed in the circumferential direction of the conductor 110 . Thereby, when the power cable 10 is energized, only the conductor 110 can meander irregularly (for example, at an irregular cycle) with respect to the wire 120 . As a result, the thermal stress can be distributed so that the thermal stress when the power cable 10 is energized does not locally concentrate on the specific segment 110s.

(Modification 4)
FIG. 6B is a schematic cross-sectional view enlarging the central portion of the power cable of Modification 4. As shown in FIG.
In Modification 4 shown in FIG. 6B, as in Modification 3, hollow portion 110w is rotationally asymmetric in at least some of the plurality of cross sections orthogonal to the axial direction of power cable 10. ing.

In this modification, central angles of the plurality of segments 110s are different from each other in at least some of the plurality of cross sections perpendicular to the axial direction of the power cable 10 . That is, the respective cross-sectional areas of the multiple segments 110s are different from each other.

According to Modification 4, the same effect as Modification 3 can be obtained.

Further, according to Modification 4, by making the center angles of the plurality of segments 110s different from each other, the rigidity of each of the plurality of segments 110s can be made different from each other. Thereby, only the conductor 110 can be easily and irregularly meandered with respect to the wire 120 .

Note that in Modifications 3 and 4, different dies must be used to manufacture each of the plurality of segments 110s. Therefore, the manufacturing cost of the power cable 10 may increase. Therefore, when the cross-sectional shapes of the plurality of segments 110s are equal to each other, as in the above-described embodiment, the plurality of segments 110s are formed using the same die, and the manufacturing cost of the power cable 10 is reduced. can be reduced.

(Modification 5)
FIG. 7A is a schematic cross-sectional view enlarging the central portion of the power cable of Modification 5. FIG.
In modification 5 shown in FIG. 7( a ), for example, in at least some of the cross sections orthogonal to the axial direction of the power cable 10 , the inner surface 114 s of each of the segments 110 s is the segment 110 s It has a concave arc shape toward the center of the . Accordingly, in the cross section, the cross-sectional shape of the hollow portion 110w is, for example, circular.

According to Modified Example 5, the inner surface 114s of each of the segments 110s is concave toward the center of the segment 110s, so that the wire rod 120 conforms to the shape of the inner surface 114s of the segment 110s. can be contacted. That is, the contact area between the segment 110s and the wire rod 120 can be increased. Therefore, this modification is effective, for example, when it is desired to increase the frictional force between the segment 110s and the wire rod 120. FIG.

Further, according to Modification 5, regardless of the number of segments 110 s and the central angle, in at least some of the plurality of cross sections perpendicular to the axial direction of power cable 10 , hollow portion 110 w is formed in the direction of conductor 110 . It can be symmetrical about the center. Thereby, regardless of the number and central angle of the segments 110s, when the power cable 10 is energized, a predetermined frictional force can be generated between the conductor 110 and the wire rod 120 in a well-balanced manner.

(Modification 6)
FIG. 7B is a schematic cross-sectional view enlarging the central portion of the power cable of Modification 6. As shown in FIG.
In Modified Example 6 shown in FIG. 7B, for example, in at least some of the cross sections perpendicular to the axial direction of the power cable 10, the inner surface 114s of each of the segments 110s is the segment 110s It has a convex circular arc shape toward the outer side in the radial direction.
Accordingly, in the cross section, the cross-sectional shape of the hollow portion 110w is, for example, substantially star-shaped.

Further, for example, in at least some cross sections among the plurality of cross sections perpendicular to the axial direction of the power cable 10, the gap 110v is at least between adjacent segments 110s among the plurality of segments 110s. radial direction of the conductor 110 from the side.

According to Modified Example 6, the inner surface 114s of each of the segments 110s has an arcuate shape that protrudes outward in the radial direction of the segment 110s, so that the wire rod 120 is in point contact with the inner surface 114s of the segment 110s. can be made That is, the contact area between the segment 110s and the wire rod 120 can be reduced. Therefore, this modification is effective, for example, when it is desired to reduce the frictional force between the segment 110s and the wire rod 120. FIG.

Further, according to Modification 6, in at least some of the plurality of cross sections perpendicular to the axial direction of the power cable 10, the gap 110v is at least between the adjacent segments 110s of the plurality of segments 110s. , spreads in the radial direction of the conductor 110 from the center side of the conductor 110, so that when the power cable 10 is energized, the wire 120 enters the gap 110v between the adjacent segments 110s, so that the wire 120 only the conductor 110 can be deflected. For example, only the conductor 110 can be bent with respect to the wire rod 120 along the spiral void 110v formed by twisting the multiple segments 110s.

(Modification 7)
FIG. 8 is an enlarged schematic view of the central portion of the power cable of Modification 7. As shown in FIG. FIG. 8 shows the inner wall 110i of the conductor 110 and the wire 120. FIG.

In Modification 7 shown in FIG. 8, the points of contact (hereinafter also referred to as points of contact of the wire 120) CP at which the wire 120 contacts the inner wall 110i of the conductor 110 are arranged at different positions along the axial direction of the power cable 10. there is That is, in an arbitrary first cross section A orthogonal to the axial direction of the power cable 10, only a part of the wire 120 is in contact with the conductor 110, while in a second cross section B different from the first cross section A, the first cross section A Only a portion of the wire 120 at a position different from the position where the wire 120 is in contact with the conductor 110 is in contact with the conductor 110 .

Furthermore, in this modification, the contact point CP of the wire 120 is positioned spirally with respect to the axial direction of the power cable 10 . For example, when the cross section perpendicular to the axial direction of the power cable 10 is moved in the axial direction, the contact point CP of the wire rod 120 sequentially moves to the adjacent segment 110s in the circumferential direction of the conductor 110 (for example, counterclockwise). ing.

The direction in which the contact points CP of the wire rod 120 move in the circumferential direction of the conductor 110 (the rotation direction of the contact points CP) may be the same as the twist direction of the plurality of segments 110s that form the conductor 110, or may be the twist direction. and vice versa. In addition, the period in which the contact CP of the wire 120 moves in the circumferential direction of the conductor 110 (the rotation period of the contact CP) may be the same as or different from the twist period of the plurality of segments 110s. may

If the rotation direction and rotation period of the contact point CP of the wire 120 are equal to the twist direction and twist period of the plurality of segments 110s, the wire 120 may always be in contact with the same segment 110s.

Here, for example, in a state where the power cable 10 is not energized, only the conductor 110 is arranged in a helical meandering manner with respect to the linear wire 120 . Thereby, the contact point CP of the wire 120 is positioned spirally with respect to the axial direction of the power cable 10 . Since the wire rod 120 is spirally arranged in the hollow portion 110w of the linear conductor 110, even if the contact point CP of the wire rod 120 is spirally positioned with respect to the axial direction of the power cable 10, good.

According to Modified Example 7, the contacts CP where the wire rod 120 is in contact with the conductor 110 are arranged at different positions along the axial direction of the power cable 10, so that when the power cable 10 is energized, the conductor Frictional forces can be generated at random locations between 110 and wire 120 . As a result, only the conductor 110 can be easily meandered with respect to the wire 120 .

Further, according to the fifth modification, the contact point CP where the wire rod 120 is in contact with the conductor 110 is positioned spirally with respect to the axial direction of the power cable 10, so that when the power cable 10 is energized, , a spiral frictional force can be generated between the conductor 110 and the wire rod 120 . As a result, only the conductor 110 can be easily helically meandered with respect to the wire 120 .

<Other embodiments of the present invention>
Although the embodiments and modifications of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments and modifications, and various changes can be made without departing from the scope of the invention.

In the above-described embodiment, the wire 120 is made of Invar wire, but the wire 120 may be made of carbon fiber, aramid fiber such as Kevlar (registered trademark) manufactured by DuPont, or the like. may

In the above-described embodiment, the segment 110s that configures the conductor 110 is configured by a single layer in the radial direction of the power cable 10, but the segment 110s that configures the conductor 110 It may be composed of a plurality of layers with respect to the direction.

In the above-described embodiment, modified example 1 and modified example 2, the cases where the segments 110s are provided five, four and six are described, respectively, but the number of the segments 110s is two, three or seven. or more may be provided.

Next, examples according to the present invention will be described.

(1) Fabrication of Power Cable As shown in Tables 1 to 3, power cables of Samples 1 to 10 and Comparative Samples 1 and 2 were fabricated.

(Samples 1-8)
FIG. 9(a) is a schematic cross-sectional view enlarging the central portion of the power cables according to Samples 1 to 5, and FIG. 9(b) is a schematic cross-sectional view enlarging the central portion of the power cables according to Samples 6 to 8. It is a diagram. As shown in FIGS. 9(a) and 9(b), CV cables having the configuration of the above-described embodiment were produced as power cables of samples 1 to 10. FIG.

Details of the configuration of the power cables of samples 1 to 8 are as follows.
Nominal voltage of power cable: 154 kV
Conductor material: Pure Cu
Conductor cross section: ^2000mm2
Number of segments: 5 (samples 1-5), 4 (samples 6-10)
Segment center angle: 72° (Samples 1-5), 90° (Samples 6-10)
Wire material: Inba Number of wires: 7 Outer diameter of wires:
4.3 mm (Samples 1-3, 5), 3.5 mm (Sample 4)
Ratio of wire cross-sectional area to conductor cross-sectional area:
20.3% (Samples 1-3, 5), 13.5% (Sample 4)
Other configuration of the central part of the power cable: As described in Tables 1 and 2 above Configuration outside the central part of the power cable: Common to each sample as in the above embodiment Outer diameter of the power cable: Conductor outer diameter +56 mm

In Tables 1 and 2, "filling rate" is the ratio of the cross-sectional area of wire rod 120 to the cross-sectional area of hollow portion 110w. Note that the cross-sectional area of the wire 120 was calculated as the sum of the cross-sectional areas of the seven wires 122 forming the wire 120 . The “wire outer diameter” is the diameter of the circumscribed circle 120 oc of the seven wires 122 forming the wire 120 . The “conductor inscribed circle diameter” is the diameter of the inscribed circle 110 sic in contact with the inner wall 110 i of the conductor 110 .
The “gap interval” (d) is the maximum value of the interval between the circumscribed circle 120oc of the seven wires 122 forming the wire 120 and the inscribed circle 110sic in contact with the inner wall 110i of the conductor 110 . In sample 1, since the conductor 110 was compressed, the cross-sectional shape of the hollow portion 110w side of the conductor 110 followed the outer shape of the seven wires 122, so the gap interval was set to 0 mm.

(Comparative sample 1)
As a power cable of Comparative Sample 1, a conventional OF cable was produced. The OF cable of Comparative Sample 1 comprises, from the center to the outside, a hollow tube, a conductor, a binder, an insulating layer, carbon paper, a shielding layer, a cloth tape, an aluminum covering, and a covering layer. ,have. The hollow tube forms an oil passage through which the oil impregnating the insulating layer is passed, and consists of a galvanized steel strip spiral. The conductor has multiple segments. The binder is made of metal tape and kraft paper, and is provided between each segment constituting the conductor and around the outer periphery of the conductor. The insulating layer is made of oil-impregnated paper. Carbon paper is provided inside and outside the insulating layer. The shielding layer consists of metal tape and carbon paper. The cloth tape is woven with copper wires. The aluminum cover consists of a corrugated aluminum coating, the outside of which is coated with an anti-corrosion paint. The covering layer is made of polyvinyl chloride.

Other details of the configuration of the OF cable of Comparative Sample 1 are as follows.
Nominal voltage of power cable: 154 kV
Conductor material: Pure Cu
Conductor cross section: ^2000mm2
Number of segments: 6 Segment center angle: 60°
Outer diameter of power cable: 111mm

(Comparative sample 2)
As a power cable of Comparative Sample 2, a conventional CV cable (reference power cable) was produced. That is, the conventional CV cable of Comparative Sample 2 is provided with no hollow portion and no wire.

Details of the configuration of the conventional CV cable of Comparative Sample 2 are as follows.
Nominal voltage of power cable: 154 kV
Conductor material: Pure Cu
Conductor cross section: ^2000mm2
Conductor outer diameter: 53.8mm
Number of segments: 5 Segment center angle: 72°
Configuration outside the center of the power cable: Same as samples 1 to 10 Outer diameter of the power cable: 110 mm

(2) Evaluation of power cable As shown in Tables 1 to 3, the theoretical value of the "linear expansion coefficient α" of the power cable was calculated. In samples 2 to 5, it has been confirmed that the actually measured value of the linear expansion coefficient of the power cable is equal to or less than the theoretical value of the linear expansion coefficient of the power cable.

Also, the "Young's modulus E" of the power cable was actually measured. The Young's moduli shown in Tables 1 to 3 are average values of actual measurements. Also, the stiffness of the conductor was calculated based on the measured Young's modulus E.

Also, the "buckling load of the conductor" _Pcr was determined by the following equation (4).

However, C is a terminal condition coefficient in the case of both ends being fixed, and was set to 4. I is the area moment of inertia of the conductor, and EI is the stiffness of the conductor in Table 1. Also, L is the length of the power cable, which is 6000 mm.

"Thermal stress" is the thermal stress that occurs in the power cable, and was determined by the above equation (1). However, the Young's modulus E and the coefficient of linear expansion α of the power cable used the Young's modulus E and the coefficient of linear expansion α of the power cable in Tables 1 to 3, respectively. The cross-sectional area A of the conductor was 2000 mm ² as described above. In addition, the temperature difference t is assumed to be 65°C and 65°C based on the difference between the conductor temperature and the base temperature of 25°C, assuming that the maximum allowable current flows through the conductor and the temperature of the conductor reaches 90°C. bottom. However, for the OF cable of Comparative Example 1 in Table 3, the temperature difference t was set to 50° C. based on the actual temperature change width of the OF cable.

Regarding the "cable deflection when energized", when the power cable 10 was energized under the condition that the maximum allowable current flowed through the conductor, the power cable flexed due to the deflection of only the conductor with respect to the wire rod. A case where the power cable did not bend was evaluated as x.

(3) Results FIG. 10 is a graph showing the thermal stress and buckling load of the power cables with respect to the filling factor of the power cables according to samples 1-8.
As shown in FIG. 10, the thermal stress of the power cable and the buckling load of the conductor with respect to the filling factor of the power cables according to Samples 1 to 8 each showed a downwardly convex tendency. In FIG. 10, the trend based on the thermal stress of each sample is extrapolated with a solid line, and the trend based on the buckling load of the conductor of each sample is extrapolated with a dotted line.

When the filling rate of the wire is less than 20%, the gap between the conductor and the wire becomes large, and friction between the conductor and the wire becomes difficult. The coefficient of linear expansion of conventional CV cables was not sufficiently reduced. In addition, since the conductor has a hollow cylindrical shape, the Young's modulus of the electric power cable is higher than that of the conventional CV cable of comparative sample 2. For these reasons, the thermal stress of the power cable tends to increase as the wire filling rate decreases to less than 20%, and the thermal stress of the OF cable of Comparative Sample 1 and the thermal stress of the conventional CV cable of Comparative Sample 2 showed a tendency to be larger than As a result, the extension amount of the power cable tended to be larger than the extension amount of the OF cable of Comparative Sample 1 and the extension amount of the conventional CV cable of Comparative Sample 2.

In addition, when the filling rate of the wire rod is less than 20%, the moment of inertia I of the conductor increases as the outer diameter of the conductor increases, so the buckling load of the conductor tends to increase excessively. rice field. On the other hand, as the filling rate of the wire decreased to less than 20%, the Young's modulus of the power cable was saturated, so the thermal stress of the power cable also tended to be saturated. When the filling rate of the wire was less than 20%, the thermal stress of the power cable tended to be less than the buckling load of the conductor 110 . For this reason, it was difficult for the conductor to buckle due to the thermal stress of the power cable, and no bending of the power cable was observed.

In addition, in the conventional CV cable of Comparative Example 2, although the thermal stress was larger than the buckling load, the cable did not bend because there was no air gap in the center of the conductor.

On the other hand, when the filling rate of the wire is 20% or more, a predetermined frictional force can be generated between the conductor and the wire, and the linear expansion coefficient of the power cable is reduced to that of the conventional CV cable of Comparative Sample 2. It was confirmed that the coefficient of linear expansion can be smaller than that of Moreover, it was confirmed that an increase in the Young's modulus of the power cable can be suppressed by setting the filling rate of the wires to 20% or more. From these, it was confirmed that the thermal stress of the power cable can be made smaller than the thermal stress of the OF cable of comparative sample 1 and the thermal stress of the conventional CV cable of comparative sample 2. As a result, it was confirmed that the extension amount of the power cable can be made smaller than the extension amount of the OF cable of Comparative Sample 1 and the extension amount of the conventional CV cable of Comparative Sample 2.

Moreover, it was confirmed that when the filling rate of the wire was set to 20% or more, the outer diameter of the conductor could be reduced and the buckling load of the conductor could be reduced. As a result, even if the thermal stress of the power cable tends to decrease as the wire filling rate increases to 20% or more, it was confirmed that the thermal stress can be made equal to or greater than the buckling load of the conductor. It was actually confirmed that the thermal stress of the power cable can cause the conductor to buckle and the conductor alone to bend with respect to the wire, that is, the power cable can bend.

On the other hand, when the filling rate of the wire rod was more than 90%, the conductor and the wire rod were in close contact with each other and behaved as one. The Young's modulus of the wire approached the Young's modulus of the wire and became large. For this reason, as the wire filling rate increases to more than 90%, the thermal stress of the power cable tends to increase, and the thermal stress of the OF cable of Comparative Sample 1 and the thermal stress of the conventional CV cable of Comparative Sample 2 also tended to increase. As a result, the extension amount of the power cable tended to be larger than the extension amount of the OF cable of Comparative Sample 1 and the extension amount of the conventional CV cable of Comparative Sample 2.

In addition, when the filling rate of the wire material exceeds 90%, the rigidity of the conductor increases as the Young's modulus of the power cable increases as described above, and the buckling load of the conductor increases excessively. rice field. Even though the thermal stress of the power cable tends to increase when the power cable is energized as the filling rate of the wire increases to more than 90%, the thermal stress is less than the buckling load of the conductor. . For this reason, it was difficult for the conductor to buckle due to the thermal stress of the power cable, and no bending of the power cable was observed.

On the other hand, when the filling rate of the wire rod is 90% or less, the electric power is generated by allowing the conductor and the wire rod to deform relative to each other while generating a predetermined frictional force between the conductor and the wire rod. It was confirmed that the Young's modulus of the power cable can be suppressed from increasing to approach the Young's modulus of the wire while reducing the linear expansion coefficient of the cable to approach that of the wire.
As a result, it was confirmed that the thermal stress of the power cable can be made smaller than the thermal stress of the OF cable of comparative sample 1 and the thermal stress of the conventional CV cable of comparative sample 2. As a result, it was confirmed that the extension amount of the power cable can be made smaller than the extension amount of the OF cable of Comparative Sample 1 and the extension amount of the conventional CV cable of Comparative Sample 2.

In addition, when the filling rate of the wire rod is 90% or less, the rigidity of the conductor can be reduced as the increase in the Young's modulus of the power cable is suppressed as described above, and the buckling load of the conductor can be reduced. I'm sure it can be made smaller. As a result, even if the thermal stress of the power cable tends to decrease as the filling rate of the wire decreases to 90% or less, it was confirmed that the thermal stress can be made equal to or greater than the buckling load of the conductor. It was actually confirmed that the thermal stress of the power cable can cause the conductor to buckle and the conductor alone to bend with respect to the wire, that is, the power cable can bend.

As described above, it was confirmed that the amount of extension of the power cable (especially the amount of extension in the installation direction of the power cable) can be reduced by setting the filling rate of the wire to 20% or more and 90% or less.

By setting the filling rate of the wire to 30% or more and 85% or less, the absolute value of the gradient of the thermal stress of the power cable with respect to the filling rate of the wire can be reduced, and the thermal stress of the power cable can be stably reduced. confirmed that it is possible. In other words, it was confirmed that the extension amount of the power cable can be stably reduced.

<Preferred embodiment of the present invention>
Preferred embodiments of the present invention are described below.

(Appendix 1)
A power cable comprising a conductor and an insulating layer covering the outer periphery of the conductor,
A hollow portion extending in the axial direction of the conductor is provided at the center of the conductor,
A wire made of a material having a higher Young's modulus and a lower coefficient of linear expansion than the material forming the conductor is inserted into the hollow portion of the conductor along the axial direction of the conductor,
The power cable, wherein a filling rate of the wire rod, which is a ratio of the cross-sectional area of the wire rod to the cross-sectional area of the hollow portion, in an arbitrary cross section perpendicular to the axial direction of the power cable is 20% or more and 90% or less.

(Appendix 2)
The power cable according to appendix 1, wherein the filling rate of the wire is 30% or more and 85% or less.

(Appendix 3)
A power cable comprising a conductor and an insulating layer covering the outer periphery of the conductor,
A hollow portion extending in the axial direction of the conductor is provided at the center of the conductor,
A wire made of a material having a higher Young's modulus and a lower coefficient of linear expansion than the material forming the conductor is inserted into the hollow portion of the conductor along the axial direction of the conductor,
The thermal stress generated in the power cable when the difference between the temperature of the conductor of the power cable and the base temperature is 65° C. is the buckling of the conductor when both ends of the power cable with a length of 6000 mm are fixed. Power cables that are over load.

(Appendix 4)
A power cable comprising a conductor and an insulating layer covering the outer periphery of the conductor,
A hollow portion extending in the axial direction of the conductor is provided at the center of the conductor,
A wire made of a material having a higher Young's modulus and a lower coefficient of linear expansion than the material forming the conductor is inserted into the hollow portion of the conductor along the axial direction of the conductor,
The power cable, wherein the hollow portion is asymmetrical with respect to the center of the conductor in at least one of a plurality of cross sections perpendicular to the axial direction of the power cable.

(Appendix 5)
A power cable comprising a conductor and an insulating layer covering the outer periphery of the conductor,
A hollow portion extending in the axial direction of the conductor is provided at the center of the conductor,
A wire made of a material having a higher Young's modulus and a lower coefficient of linear expansion than the material forming the conductor is inserted into the hollow portion of the conductor along the axial direction of the conductor,
The power cable, wherein the hollow portion is rotationally asymmetric in at least a portion of a plurality of cross sections perpendicular to the axial direction of the power cable.

(Appendix 6)
A power cable comprising a conductor and an insulating layer covering the outer periphery of the conductor,
A hollow portion extending in the axial direction of the conductor is provided in the central portion of the conductor,
A wire made of a material having a higher Young's modulus and a lower coefficient of linear expansion than the material forming the conductor is inserted into the hollow portion of the conductor along the axial direction of the conductor,
In any first cross section perpendicular to the axial direction of the power cable, only a portion of the wire is in contact with the conductor,
In a second cross section different from the first cross section, only part of the wire is in contact with the conductor at a position different from the position where the part of the wire is in contact with the conductor in the first cross section. .

(Appendix 7)
7. The power cable according to appendix 6, wherein the portion where the wire is in contact with the conductor is positioned spirally with respect to the axial direction of the power cable.

(Appendix 8)
8. The power cable according to any one of Appendices 1 to 7, wherein only the conductor bends so as to meander with respect to the wire when the power cable is energized.

(Appendix 9)
A reference power in which the Young's modulus of the power cable is E, the linear expansion coefficient of the power cable is α, and the cross-sectional area of the conductor is equal to the cross-sectional area of the conductor of the power cable and the hollow portion and the wire are not provided When the Young's modulus of the cable is E ₀ and the linear expansion coefficient of the reference power cable is α ₀ , the thermal stress ratio R obtained by R = Eα/E ₀ α ₀ is less than 1. The power cable according to any one of .

(Appendix 10)
The coefficient of linear expansion of the power cable is smaller than the coefficient of linear expansion of a reference power cable in which the cross-sectional area of the conductor is equal to the cross-sectional area of the conductor of the power cable and the hollow portion and the wire are not provided,
10. The power cable according to any one of Appendices 1 to 9, wherein the Young's modulus of the power cable is 1 to 1.2 times the Young's modulus of the reference power cable.

(Appendix 11)
11. The power cable according to any one of Appendices 1 to 10, wherein the ratio of the cross-sectional area of the wire to the cross-sectional area of the conductor is 4% or more and 10% or less.

(Appendix 12)
The power cable according to any one of claims 1 to 11, wherein the conductor has a plurality of segments formed by twisting a plurality of strands.

(Appendix 13)
13. The power cable according to appendix 12, wherein the wire is in contact with at least one of the plurality of segments in at least some of the plurality of cross sections perpendicular to the axial direction of the power cable.

(Appendix 14)
Supplementary note 12 wherein the hollow portion has a gap between at least one of the plurality of segments and the wire in at least some of the plurality of cross sections perpendicular to the axial direction of the power cable. Or the power cable according to 13.

(Appendix 15)
15. The power cable according to Appendices 1 to 14, wherein the conductor is incompressible.

(Appendix 16)
16. The power cable according to any one of Appendices 1 to 15, wherein a predetermined length of the wire rod can be pulled out from the hollow portion at the distal end of the power cable.

(Appendix 17)
A method for manufacturing a power cable, comprising: forming a conductor; and forming an insulating layer so as to cover the outer periphery of the conductor,
In the step of forming the conductor,
While forming a hollow portion extending in the axial direction of the conductor at the center of the conductor,
inserting a wire made of a material having a higher Young's modulus and a lower coefficient of linear expansion than the material forming the conductor into the hollow portion of the conductor along the axial direction of the conductor;
A method of manufacturing a power cable, wherein the filling rate of the wire, which is a ratio of the cross-sectional area of the wire to the cross-sectional area of the hollow portion in an arbitrary cross section perpendicular to the axial direction of the power cable, is 20% or more and 90% or less.

(Appendix 18)
A conductor and an insulating layer covering the outer periphery of the conductor, a hollow portion extending in an axial direction of the conductor is provided at the center of the conductor, and the conductor is configured in the hollow portion of the conductor. a pair of power cables in which a wire made of a material having a higher Young's modulus and a lower coefficient of linear expansion than the material is inserted along the axial direction of the conductor;
a stopper fixed to the tip of the wire pulled out from the hollow portion of the conductor of each of the pair of power cables and restricting extension of the conductor in the axial direction;
a sleeve configured as a metal cylindrical body, inserted so that the ends of the conductors of each of the pair of power cables are opposed to each other with the stoppers fixed, and compressively connecting the pair of conductors;
A power cable connection structure comprising:

(Appendix 19)
A conductor and an insulating layer covering the outer periphery of the conductor, a hollow portion extending in an axial direction of the conductor is provided at the center of the conductor, and the conductor is configured in the hollow portion of the conductor. A step of preparing a pair of power cables in which a wire composed of a material having a larger Young's modulus and a smaller linear expansion coefficient than the material is inserted along the axial direction of the conductor;
a step of pulling out the tip of the wire from the hollow portion of each of the conductors of the pair of power cables, and fixing a stopper to the tip of each of the wires for restricting extension of the conductor in the axial direction;
The ends of the conductors of each of the pair of power cables are inserted into a sleeve configured as a metal cylindrical body so as to face each other with the stopper fixed, and the sleeve is compressed from the outside. thereby compressively connecting the pair of conductors together;
A method of connecting a power cable comprising:

10 power cable 20 connection structure 110 conductor 110i inner wall 110s segment 110sic inscribed circle 110v gap 110w hollow portion 112s outer peripheral surface 114s inner surface 116s side surface 120 wire rod
120oc Circumscribed circle 122 Wire 130 Binder 140 Internal semiconductive layer 150 Insulating layer 160 External semiconductive layer 172 Shielding layer 174 Pressing tape 176 Waterproof layer 180 Sheath 210 Sleeve 220 Stopper 230 Insulating cylinder 920 Pipe 940 Manhole

Claims (2)

A conductor and an insulating layer covering the outer periphery of the conductor, a hollow portion extending in an axial direction of the conductor is provided at the center of the conductor, and the conductor is configured in the hollow portion of the conductor. a pair of power cables in which a wire made of a material having a higher Young's modulus and a lower coefficient of linear expansion than the material is inserted along the axial direction of the conductor;
a stopper fixed to the tip of the wire pulled out from the hollow portion of the conductor of each of the pair of power cables and restricting extension of the conductor in the axial direction;
a sleeve configured as a metal cylindrical body, inserted so that the ends of the conductors of each of the pair of power cables are opposed to each other with the stoppers fixed, and compressively connecting the pair of conductors;
A power cable connection structure comprising: A conductor and an insulating layer covering the outer periphery of the conductor, a hollow portion extending in an axial direction of the conductor is provided at the center of the conductor, and the conductor is configured in the hollow portion of the conductor. A step of preparing a pair of power cables in which a wire composed of a material having a larger Young's modulus and a smaller linear expansion coefficient than the material is inserted along the axial direction of the conductor;
a step of pulling out the tip of the wire from the hollow portion of each of the conductors of the pair of power cables, and fixing a stopper to the tip of each of the wires for restricting extension of the conductor in the axial direction;
The ends of the conductors of each of the pair of power cables are inserted into a sleeve configured as a metal cylindrical body so as to face each other with the stopper fixed, and the sleeve is compressed from the outside. thereby compressively connecting the pair of conductors together;
A method of connecting a power cable comprising:

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