JP2016054116A - Power cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an amount of stretch by means of a convenient structure.SOLUTION: A power cable has a conductive part composed of aluminum or aluminum alloys, an insulating layer that covers the periphery of the conductive part, and a coating layer that covers the periphery of the insulating layer. In the conductive part, wires composed of a material having a higher Young's modulus than that of a material constituting the conductive part and a lower linear expansion coefficient than that of it are provided in the axial direction of the conductive part.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power cable, and more particularly to a power cable used as an underground transmission line for high-voltage power.

  The power cable includes, for example, a conductive portion, an insulating layer that covers the outer periphery of the conductive portion, and a coating layer that covers the outer periphery of the insulating layer. Such a power cable is used as, for example, an underground transmission line for high-voltage power, and is laid in a limited space such as in a pipeline. When power is supplied to the conductive portion, the power cable extends in the axial direction due to thermal expansion and contraction. The amount of extension that cannot be absorbed in the restricted space in the pipeline is absorbed by the bending deformation of the power cable that extends into the manhole provided in the middle of the pipeline.

  Further, when there is an inclination or the like in the pipeline, the power cable may slide down due to this thermal expansion and contraction. Such slipping is greatly influenced not only by the mass, length, and temperature change of the power cable, but also by the linear expansion coefficient. That is, the power cable slides when the region where the temperature change width is large and the thermal expansion / contraction does not occur, that is, the immovable region disappears. For this reason, an anti-skid device or the like that holds the power cable using a spring or weight may be attached to the power cable.

  The amount of cross-linked polyethylene insulated PVC sheathed cable (CV cable) that has become mainstream in recent years is the same as that of oil-filled paper insulated power cables (OF cable: Oil Filled Cable). It is more than the amount to be put out.

  For this reason, for example, when there is a reason for renewal such as a system change of an existing line where an OF cable has been used, an accident response or aged disposal, etc., there is room to absorb the amount of extension of the CV cable in the manhole size etc. There may not be. In such a case, the actual situation is that it has to be updated with an OF cable as before.

  Therefore, in Patent Document 1, for example, a linear body is wound in a spiral shape on the circumference of the power cable body, and a snake-like deformation is assisted along the winding of the linear body. The extension to the snake shape suppresses the extension in the axial direction and reduces the extension amount from the pipe line to the human hole.

Japanese Patent Laid-Open No. 03-102713

  However, as in Patent Document 1, for example, a snake shape is not easily obtained simply by winding a linear body around a power cable body. Therefore, complicated additional measures such as applying tension to the linear body and forming the linear body so as to periodically have thick and thin portions in the length direction are required. Moreover, since a part of the outer shape is spiral and the cross section of the power cable is not circular, cable processing and laying are difficult.

  Moreover, in order to suppress the slipping of the power cable due to an inclination in the pipe line or the like, if a slipping prevention device using a spring or a weight is attached to the power cable as described above, the size of the human hole becomes large.

  An object of the present invention is to provide a power cable that can reduce the amount of extension with a simple structure.

According to a first aspect of the invention,
A conductive portion made of aluminum or an aluminum alloy;
An insulating layer covering the outer periphery of the conductive portion;
A coating layer covering the outer periphery of the insulating layer,
In the conductive part,
A power cable is provided in which a wire made of a material having a Young's modulus and a smaller linear expansion coefficient than the material constituting the conductive portion is provided along the axial direction of the conductive portion.

According to a second aspect of the invention,
A hollow portion extending in the axial direction of the conductive portion is provided in the central portion of the conductive portion,
The power cable according to the first aspect in which the wire provided in the conductive portion is inserted into the hollow portion is provided.

According to a third aspect of the invention,
The conductive portion is a combination of a plurality of segments,
The power cable according to the first aspect is provided in which the wire provided in the conductive portion is disposed in each of the segments.

According to a fourth aspect of the invention,
The electric power cable according to a third aspect is provided in which the wire is disposed in each segment so that the wire is located in the center in the segment.

According to a fifth aspect of the present invention,
The electric power cable according to a third aspect is provided in which the wire is disposed in each segment so that each wire is located in the vicinity of an outer edge portion in the segment.

According to a sixth aspect of the present invention,
The power cable according to any one of the first to fifth aspects is provided in which at least a part of an outer surface of a wire provided in the conductive portion is in contact with the conductive portion.

According to a seventh aspect of the present invention,
The power cable according to any one of the first to sixth aspects is provided in which at least a part of the conductive portion is meandered when the conductive portion is energized.

According to an eighth aspect of the present invention,
The power cable according to any one of the first to seventh aspects, in which the wire provided in the conductive portion is an invar wire.

According to a ninth aspect of the present invention,
The insulating layer is composed of cross-linked polyethylene,
The power cable according to any one of the first to eighth aspects, in which the covering layer is made of vinyl chloride.

  ADVANTAGE OF THE INVENTION According to this invention, the electric power cable which can reduce the amount of extension with a simple structure is provided.

It is sectional drawing orthogonal to the axial direction of the power cable which concerns on one Embodiment of this invention. It is sectional drawing orthogonal to the axial direction which shows the structural example of the power cable which concerns on one Embodiment of this invention. (A) is sectional drawing orthogonal to the axial direction of the power cable which concerns on the Example of this invention, and sectional drawing of an axial direction, (b) is sectional drawing orthogonal to the axial direction of the CV cable which concerns on a comparative example. (C) is sectional drawing orthogonal to the axial direction of OF cable which concerns on another comparative example, and sectional drawing of an axial direction. It is a schematic diagram which shows the state of the installation of the power cable used as an underground power transmission line.

<One Embodiment of the Present Invention>
(1) Structure of Power Cable A power cable according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view orthogonal to the axial direction of the power cable 1 according to the present embodiment.

  As shown in FIG. 1, the power cable 1 according to this embodiment includes a conductive portion 10, an insulating layer 20 that covers the outer periphery of the conductive portion 10, and a covering layer 30 that covers the outer periphery of the insulating layer 20. Prepare. In the conductive part 10, a wire 40 made of a material having a Young's modulus and a smaller linear expansion coefficient than the material constituting the conductive part 10 is provided.

  At this time, for example, the conductive portion 10 is a metal conductor such as an aluminum conductor or a copper conductor, the insulating layer 20 is made of crosslinked polyethylene, the covering layer 30 is made of vinyl chloride, the wire 40 is an invar wire, and the power cable 1 is crosslinked. It can be configured as a power cable in which an invar wire is combined with a polyethylene insulated vinyl sheathed cable (CV cable).

  That is, the conductive portion 10 is made of, for example, a plurality of segments 10s made of a metal such as (pure) aluminum (Al), an aluminum alloy, (pure) copper (Cu), or a copper alloy and having a cross-sectional shape such as a trapezoidal shape or a fan shape. Is a conductive metal conductor such as an aluminum conductor or a copper conductor. At this time, each segment 10s may be configured by twisting a plurality of strands made of metal such as aluminum, aluminum alloy, copper, or copper alloy. Moreover, each segment 10s may be combined so that it may become two layers of an inner layer and an outer layer, or may be combined so that it may become more than that several layers. A hollow portion 10 w extending in the axial direction of the conductive portion 10 is provided at the center of the combined (innermost layer) segment 10 s, that is, at the central portion of the conductive portion 10.

  The wire 40 is inserted into the hollow portion 10 w and is inserted along the axial direction of the conductive portion 10. At this time, the wire 40 may be inserted into the hollow 10w with a gap, or may be inserted into the hollow portion 10w without a gap, and at least a part of the outer surface of the wire 40 may be inserted into the hollow portion 10w inner wall. It may be in contact with the conductive part 10 to be configured. Moreover, at this time, the wire 40 may be comprised only from one piece, or may be comprised in the state bundled by twisting or compressing several strands. Further, the wire 40 is made of, for example, an invar wire made of stainless steel obtained by adding a predetermined amount of nickel (Ni) to iron (Fe), a carbon composite wire made of carbon fiber, or the like. Such a material has a higher Young's modulus and a smaller linear expansion coefficient than a metal conductor such as an aluminum conductor or a copper conductor constituting the conductive portion 10, for example.

  The power cable 1 configured as described above is laid in, for example, a pipeline provided in the ground. For example, a cable connecting portion for connecting the power cables 1 to each other is installed in a human hole provided at a predetermined position of the pipeline. The power cables 1 are connected by compressing the wires 40 provided in the power cable 1.

(2) Action of power cable The power cable 1 according to the present embodiment has the following action.

  That is, when the conductive portion 10 is energized, the conductive portion 10 extends due to the temperature rise. On the other hand, the wire 40 inserted into the hollow portion 10 w has a smaller amount of extension than the conductive portion 10. For this reason, the conductive part 10 absorbs its extension amount by bending to meander with a predetermined period or an irregular period with respect to the axial direction. At this time, the snake shape may be taken so that the insulating layer 20, the covering material 30 and the like provided around the conductive portion 10 follow the conductive portion 10, and as a result, the entire power cable 1 may take the snake shape.

  Alternatively, the power cable 1 is shaped so as to be balanced between the conductive portion 10 having a small extension amount in the axial direction and the wire 40 having a large extension amount in the axial direction. The amount of extension of may be absorbed. Thus, when the power cable 1 takes a balanced shape so as to absorb the amount of extension, the power cable 1 may not have a snake shape.

  Further, as described above, if the wire 40 having a smaller linear expansion coefficient than that of the constituent material of the conductive portion 10 is used and, for example, as described above, the wire 40 and the conductive portion 10 are brought into contact with each other, the elongation is increased. The amount to be taken out can be further reduced, which is more preferable. In such a configuration, it is considered that the extension amount is reduced mainly due to friction between the wire 40 and the conductive portion 10. In such a case, it is considered that there is an effect of suppressing the extension force at the terminal of the power cable 1.

  The amount of extension at both ends of the cable that could not be absorbed by the above is absorbed when the power cable 1 is bent, that is, offset, in the human hole where the cable connection portion is installed. In the power cable 1, the amount of extension into the human hole is reduced.

  Thereby, the amount of bending deformation of the power cable 1 extending into the human hole, that is, the so-called offset deformation amount can be reduced. Usually, in a power cable having an outer diameter D, the allowable bending radius is, for example, 10D or more. In the power cable 1 of this embodiment, the amount of offset deformation can be kept small, and the amount of deformation (bending amount) equal to or larger than the allowable bending radius can be maintained in a small-sized human hole.

  Moreover, in the power cable 1, the extension amount of the whole power cable 1 is reduced, and even if the temperature change width increases, a region where thermal expansion and contraction does not occur, that is, a so-called immovable region can be sufficiently secured. . This makes it difficult for the power cable 1 to slide down even in an inclined pipeline. Therefore, for example, it is not necessary to attach an anti-skid device or the like that suppresses slipping using a spring, a weight, or the like in the human hole to the power cable 1, and laying is possible even if the human hole size is small.

  For example, in the conventional CV cable, the amount of extension exceeds that of the OF cable. For this reason, it may become an offset bend radius which falls below an allowable bend radius in the human hole due to extension when energized. In the case of an inclined pipe, sliding is likely to occur. Thus, it is often difficult to lay CV cables on existing lines for OF cables. In addition, when a new line for a CV cable is provided, the size of the manhole must be enlarged so that the bending radius is not less than the allowable bending radius when energized, and a slip prevention device or the like can be installed.

  However, in the power cable 1 according to the present embodiment, the amount of extension is equal to or less than that of the OF cable. Sliding in the pipeline is unlikely to occur. Further, the cross-sectional area of the conductive portion 10 of the power cable 1 can be configured to be substantially equal to, for example, an OF cable having a hollow tube serving as an oil path in the conductive portion. Therefore, compared with an OF cable, it can have the same or more power transmission capacity.

  Thus, the power cable 1 according to this embodiment can be easily laid on an existing line for an OF cable. By replacing the existing OF cable, for example, the oil supply facility can be eliminated from the inside of the track. Moreover, when providing a new track, it is not necessary to increase the size of the manhole. Thus, the power cable 1 according to the present embodiment is advantageous in terms of line design and line maintenance.

  Here, a case where the conductive portion is made of aluminum or an aluminum alloy will be described.

The linear expansion coefficient of copper is 16.5 × 10 ⁻⁶ (1 / ° C.), whereas the linear expansion coefficient of aluminum is 23 × 10 ⁻⁶ (1 / ° C.), and the linear expansion coefficient of aluminum is About 35% larger than the linear expansion coefficient of copper. For this reason, in the case where the conductive part is made of aluminum or an aluminum alloy in the CV cable or OF cable, the linear expansion coefficient of the CV cable or OF cable is larger than that in the case where the conductive part is made of copper. Alternatively, the amount of extension of the OF cable tends to be larger than when the conductive portion is made of copper.

  However, in the power cable 1 according to the present embodiment, even if the conductive portion 10 is made of aluminum or an aluminum alloy having a large linear expansion coefficient, the conductive portion 10 is made of a material having a low linear expansion coefficient. By providing the wire 40, the linear expansion coefficient of the power cable 1 can be reduced more than the linear expansion coefficient of the CV cable or OF cable. Thereby, the extension amount of the power cable 1 can be suppressed. Therefore, even in a line where it is difficult to lay a CV cable or OF cable in which the conductive portion is made of aluminum or an aluminum alloy because the extension amount is large, the conductive portion is made of aluminum or an aluminum alloy. The power cable 1 thus made can be laid easily.

  When the conductive part 10 is made of aluminum or an aluminum alloy, the cost of the power cable 1 can be reduced because aluminum is a metal that is cheaper than copper. Moreover, since the specific gravity of aluminum is smaller than the specific gravity of copper, the power cable 1 can be reduced in weight.

(3) Power Cable Manufacturing Method The power cable 1 according to this embodiment can be manufactured by the following manufacturing method.

  That is, first, a strand such as an invar wire is prepared, and this is used as the wire 40. Alternatively, a stranded wire obtained by twisting a plurality of such strands is used as the wire 40. For example, by twisting one or more layers of segments 10s made of metal such as aluminum, aluminum alloy, copper or copper alloy around the wire 40, the conductive portion 10 in which the wire 40 is inserted into the hollow portion 10w is obtained. . As described above, each segment 10s is formed by twisting a plurality of strands made of metal such as aluminum, aluminum alloy, copper, or copper alloy so as to have a cross-sectional shape such as a trapezoidal shape or a fan shape. be able to.

  Thereafter, for example, an insulating layer 20 made of crosslinked polyethylene and a coating layer 30 made of vinyl chloride are formed on the outer periphery of the conductive portion 10 by extrusion molding or the like. As described above, the power cable 1 according to this embodiment is manufactured.

(4) Modified Example of Present Embodiment Next, a power cable according to a modified example of the present embodiment will be described with reference to FIG. FIG. 2 is a cross-sectional view orthogonal to the axial direction illustrating a configuration example of a power cable according to an embodiment of the present invention. In FIG. 2, components that are substantially the same as those described in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted.

  In the above-described embodiment, the insertion position of the wire rod 40 is the central portion of the conductive portion 10, but the insertion positions of the wire rods 41 and 42 are different in the power cables 1a and 1b according to the modification.

  That is, as shown in FIG. 2A, in the cable 1a according to the modified example, the conductive portion 11 is formed by combining a plurality of segments 11s, and the wire 41 is disposed at the center of each segment 11s. Has been.

  Thus, it can suppress that the meandering of the electroconductive part 11 arises because each wire 41 is arrange | positioned equally in the center part of each segment 11s. Therefore, for example, in the pipe line that extends in a straight line, the conductive portion 11 or the power cable 1a has a snake shape that is substantially along the pipe line.

  The power cable 1a can be manufactured, for example, by the following method. That is, first, a wire such as an invar wire or a stranded wire obtained by twisting a plurality of strands is used as a wire 41, and is made of a metal such as aluminum, aluminum alloy, copper, or copper alloy around the wire 41. Each segment 11s is manufactured by twisting one or more strands. Thereafter, the power cable 1a is manufactured by combining the segments 11s in a predetermined number and in a predetermined arrangement, and compressing the whole from the outermost layer side before or after forming the insulating layer 20 and the covering layer 30. .

  Further, as shown in FIG. 2B, in the cable 1b according to another modification, the conductive portion 12 is formed by combining a plurality of segments 12s, and a plurality of segments are provided near the outer edge of each segment 12s. Wires 42 are respectively arranged. Like each segment 11s of the power cable 1a, each segment 12s of the power cable 1b is also formed by twisting a strand such as an invar wire and a strand made of a metal such as aluminum, aluminum alloy, copper, or copper alloy. As configured together, the arrangement of the wires 42 in the cross section shown in FIG. 2B is merely an example. That is, the position of each wire 42 changes while undulating within the segment 12s. Therefore, depending on which cross section of the power cable 1b is cut out, the outer edge side in contact with the insulating layer 20, the outer edge side in contact with one adjacent segment 12s, and the outer edge side in contact with the other adjacent segment 12s in the segment 12s , And the position of each wire 42 seems to move.

  As described above, the conductive portions 12 are easy to meander by arranging each wire 42 at the outer edge of each segment 11s while changing its position. Therefore, for example, in a meandering pipeline, the conductive portion 12 or the power cable 1b can be adjusted by the arrangement of each wire 42 so as to take a snake shape along the curvature in the pipeline.

  The power cable 1b can also be manufactured by the same method as the power cable 1a. However, in this case, in the bundle of a plurality of strands made of metal such as aluminum, aluminum alloy, copper or copper alloy, the wire 42 is mixed so as to be positioned in the vicinity of the outer edge portion of the segment 12s, The wire 42 and the strand are twisted together.

<Other Embodiments of the Present Invention>
As mentioned above, although embodiment and modification of this invention were described concretely, this invention is not limited to the above-mentioned embodiment and modification, and can be variously changed in the range which does not deviate from the summary.

  For example, in the above-described embodiment and modification, the wire rods 40, 41, and 42 are made of invar wires, but the wire rod is, for example, carbon fiber or aramid fiber such as Kevlar (registered trademark) manufactured by DuPont. You may be comprised from. As described above, any material having a Young's modulus and a smaller linear expansion coefficient than the material constituting the conductive portion can be used as a wire.

  Further, for example, the shape and number of segments, the number of layers, the arrangement, the number and arrangement of inserted wires described in the above-described embodiments and modifications are merely examples, and are not limited thereto.

  Further, for example, in the above-described embodiment and modification, the power cable 1 in which the wire 40, 41, 42 such as the invar wire is combined with the CV cable has been described. However, this configuration is applied to the OF cable and other cables. Also good.

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

(1) Calculation of extension amount First, theoretical values such as the extension amount were calculated for the power cables according to the example and the comparative example. FIG. 3 shows the specifications of the power cable used for calculating the theoretical value.

  3A is a cross-sectional view orthogonal to the axial direction of the power cable 2 according to the embodiment of the present invention and an axial cross-sectional view, and FIG. 3B is a cross-sectional view of the CV cable 3 according to the comparative example. It is sectional drawing orthogonal to an axial direction, and sectional drawing of an axial direction, (c) is sectional drawing orthogonal to the axial direction of OF cable 4 which concerns on another comparative example, and sectional drawing of an axial direction.

  As shown in FIG. 3A, the power cable 2 according to the embodiment is configured as a power cable in which a wire 240 is inserted into a hollow portion 210w provided in the central portion of the conductive portion 210.

  That is, the power cable 2 includes a conductive portion 210 made of a plurality of segments made of aluminum or copper, an insulating layer 220 made of crosslinked polyethylene, and a coating layer 230 made of vinyl chloride. Further, a wire 240 made of Invar stranded wire is provided in the hollow portion of the conductive portion 210. In addition, a binder 221 made of a semiconductive tape is provided on the outer periphery of the conductive portion 210. Insulating paper is inserted between the segments of the conductive portion 210.

  An internal semiconductive layer 222 is provided between the binder 221 and the insulating layer 220. Further, between the insulating layer 220 and the covering layer 230, an outer semiconductive layer 231, a shielding layer 232 formed by combining an annealed copper wire, a pressing tape 233, and a water shielding layer 234 are provided in this order from the insulating layer 220 side. Yes.

  As shown in FIG. 3B, the power cable 3 according to the comparative example is a general cross-linked polyethylene insulated PVC sheathed cable (hereinafter referred to as CV cable). Say).

  That is, the CV cable 3 includes a conductive portion 310 composed of a plurality of segments made of aluminum or copper, an insulating layer 320 made of crosslinked polyethylene, and a coating layer 330 made of vinyl chloride.

  An internal semiconductive layer 322 is provided between the conductive portion 310 and the insulating layer 320. Between the insulating layer 320 and the covering layer 330, an external semiconductive layer 331, a shielding layer 332 formed by combining an annealed copper wire, a pressing tape 333, and a water shielding layer 334 are provided in this order from the insulating layer 320 side. Yes.

  As shown in FIG. 3C, the power cable 4 according to another comparative example is a general oil-immersed paper insulated power cable (OF cable: Oil Filled Cable) (hereinafter referred to as the OF cable 4). Say).

  That is, the OF cable 4 includes a conductive portion 410 made of an aluminum wire or a soft copper wire, an insulating layer 420 made of insulating paper soaked with oil, and a coating layer 430 that is an anticorrosion layer made of vinyl chloride (PVC). Is provided. In addition, a hollow tube 411 made of a zinc steel strip spiral is inserted in the center of the conductive portion 410, and an oil passage P through which oil to be impregnated into the insulating layer 420 is passed is provided. In addition, a binder 421 made of a metal tape and insulating paper such as kraft paper is provided on the outer periphery of the conductive portion 410. Part of the insulating paper constituting the binder 421 is also inserted between the segments of the conductive portion 410.

  The insulating layer 420 is covered with carbon paper 422 and 431 on the inside and outside, respectively. Further, between the outer carbon paper 431 and the coating layer 430, a shielding layer 432 made of a metal tape and carbon paper, a copper wire woven cloth tape 433, and an anticorrosion paint are applied to the outside in order from the carbon paper 431 side. A corrugated aluminum cover 434 is provided.

For each of the cables 2 to 4 having such a structure, the theoretical value of the amount of extension was calculated when the conductive portion was made of aluminum or when the conductive portion was made of copper. The examination conditions for the calculation are as follows: the conductor cross-sectional area of each cable 2 to 4 is 2000 mm ² , the distance between the cable connection parts (joints) is 500 m, and the annual temperature change in each of the conductive parts 210, 310, and 410 The width was 65 ° C., the coefficient of friction between the pipe and each cable 2 to 4 was 0.4, and the force (offset resistance) against the offset deformation of each cable 2 to 4 was 100 kgf. The Young's modulus of the power cable 2 according to the example is the same as that of the CV cable according to the comparative example.

  As shown in Tables 1 and 2, the power cable 2 according to the example is considered to have the same Young's modulus of the entire cable as the CV cable 3 according to the comparative example, but the linear expansion coefficient is comparative. It becomes an excellent numerical value equal to or less than that of the OF cable 4 according to the example. Therefore, it is predicted that the extension amount can be suppressed to be equal to or less than that of the OF cable 4.

(2) Consideration about installation and sliding Next, the possibility of installation and the possibility of sliding down of the cables 2 and 3 in the predetermined pipe line are considered from the calculation result of the extension amount.

(Laying possibility)
First, the possibility of laying the cables 2 and 3 in a line form shown in FIG. FIG. 4 is a schematic diagram showing a laying state of a power cable used as an underground power transmission line.

  As shown in FIG. 4, in the line form to be considered, the length L of the conduit 52 connecting the two human holes 51 is 300 m or 500 m, and the cables 2 and 3 to be laid in the human holes 51 are provided. The length to the cable connecting portion J, that is, the offset length d was 2800 mm, and the allowable width of offset deformation in the human hole 51, that is, the offset width F was 650 mm.

In addition, the specifications of the cables 2 and 3 to be installed were based on a CV cable having an applied voltage of 154 kV, the number of conductive parts × the nominal conductor cross-sectional area of 1 × 2000 mm ² , and the cable outer diameter D of 110 mm.

  In addition, the offset bending radius R after the cable extends is obtained by the following formula (1).

  Here, θ satisfies the following formula (2).

However,
R: Offset bend radius after cable extension (mm)
l ₁ : Length of the arc portion in the offset length d (mm)
l ₂ : Length of the straight portion (mm) out of the offset length d
F: Offset width (mm)
m: Cable extension (mm)
It is.

  When the CV cable 3 according to the comparative example in which the conductive portion is made of aluminum is laid in a line form of L = 300 m, the extension amount m when the annual temperature change width is 65 ° C. is 198 mm from Table 1. is there. In this case, the offset bending radius R after the extension amount m is absorbed by the human hole 51 is 9.1D with respect to the cable outer diameter D. Further, when the CV cable 3 according to the comparative example in which the conductive portion is made of copper is laid in a line form of L = 500 m, from Table 2, the amount of extension m when the annual temperature change width is 65 ° C. is 205 mm. In this case, the offset bending radius R after the extension amount m is absorbed by the human hole 51 is 9.0 D with respect to the cable outer diameter D. As described above, in the two cases of the comparative example described above, the offset bending radius R is less than the allowable bending radius 10D of the cable. For this reason, the CV cable 3 cannot be laid in such a line form, or the line form must be expanded to a larger one.

  On the other hand, when the power cable 2 according to the embodiment in which the conductive portion is made of aluminum is laid in the line form of L = 300 m, the extension amount m when the annual temperature range is 65 ° C. is 148 mm from Table 1. It is. In this case, the offset bending radius R after the extension amount m is absorbed by the human hole 51 is 10.1 D with respect to the cable outer diameter D. In addition, when the power cable 2 according to the embodiment in which the conductive portion is made of copper is laid in a line form of L = 500 m, from Table 2, the amount of extension m when the annual temperature range is 65 ° C. is 145 mm. It is. In this case, the offset bending radius R after the extension amount m is absorbed by the human hole 51 is 10.1 D with respect to the cable outer diameter D. Thus, in the two cases of the above-described embodiments, the offset bending radius R can be 10D or more. For this reason, the power cable 2 according to the embodiment can be laid also in such a line form in which it is difficult to lay a conventional CV cable. Moreover, the extension of a track form is not required.

(Sliding possibility)
Subsequently, the electric power cable 2 according to the example and the CV cable 3 according to the comparative example in which the respective conductive parts are made of copper are simulated, and the pipe length L between the manholes is 600 m, and the height difference. Consider the possibility of slipping when laying in a 10m track form.

  When the CV cable 3 according to the comparative example is laid in such a line form, the annual temperature change width in which the sliding occurs is 53 ° C. In addition, when the annual temperature change width is 65 ° C., the sliding amount is 6.1 mm.

  On the other hand, when the power cable 2 according to the embodiment is laid in such a line form, sliding does not occur until the annual temperature change width reaches 68 ° C. Therefore, a slip-preventing device such as a restraining device that suppresses the slip-off is not necessary, and the extension of the track form is also unnecessary.

  Subsequently, the electric power cable 2 according to the example and the CV cable 3 according to the comparative example in which the respective conductive portions are made of aluminum are simulated, and the pipe length L between the manholes is 1000 m, and the height difference. Consider the possibility of slipping when laying in the form of a 5m track.

  When the CV cable 3 according to the comparative example is laid in such a line form, the annual temperature change width in which the sliding occurs is 43 ° C. In addition, when the annual temperature change width is 65 ° C., the sliding amount is 6.4 mm.

  On the other hand, when the power cable 2 according to the embodiment is laid in such a line form, sliding does not occur until the annual temperature change width reaches 70 ° C. Therefore, a slip-preventing device such as a restraining device that suppresses the slip-off is not necessary, and the extension of the track form is also unnecessary.

(3) Measurement of linear expansion coefficient The linear expansion coefficient of the power cable 2 according to the example was measured.

As a result of actual measurement, when the conductive portion is made of copper, the linear expansion coefficient of the power cable 2 according to the example was 12 × 10 ⁻⁶ (1 / ° C.). Therefore, it was found that the theoretical value 20 × 10 ⁻⁶ (1 / ° C.) of the CV cable 3 according to the comparative example can be reduced by about 40%. Further, it was found that the theoretical value of 16.5 × 10 ⁻⁶ (1 / ° C.) of the OF cable 4 according to another comparative example can be reduced by about 25%.

Moreover, as a result of actual measurement, when the conductive portion was made of aluminum, the linear expansion coefficient of the power cable 2 according to the example was 14 × 10 ⁻⁶ (1 / ° C.). Therefore, it was found that the theoretical value 23 × 10 ⁻⁶ (1 / ° C.) of the CV cable 3 according to the comparative example can be reduced by about 40%. Further, it was found that about 40% can be reduced compared with the theoretical value 23 × 10 ⁻⁶ (1 / ° C.) of the OF cable 4 according to another comparative example. Thus, it was found that the linear expansion coefficient of the power cable 2 can be reduced by providing a predetermined wire in the conductive portion even when the conductive portion is made of aluminum having a large linear expansion coefficient.

1, 1a, 1b Power cable 10, 11, 12 Conductive part 10s, 11s, 12s Segment 10w Hollow part 20 Insulating layer 30 Covering layer 40, 41, 42 Wire material

Claims (9)

A conductive portion made of aluminum or an aluminum alloy;
An insulating layer covering the outer periphery of the conductive portion;
A coating layer covering the outer periphery of the insulating layer,
In the conductive part,
A power cable comprising a wire made of a material having a Young's modulus and a smaller linear expansion coefficient than a material constituting the conductive portion, along an axial direction of the conductive portion. A hollow portion extending in the axial direction of the conductive portion is provided in the central portion of the conductive portion,
The power cable according to claim 1, wherein the wire provided in the conductive portion is inserted into the hollow portion. The conductive portion is a combination of a plurality of segments,
The power cable according to claim 1, wherein the wire provided in the conductive portion is disposed in each segment. The power cable according to claim 3, wherein the wire is disposed in each segment so that each wire is located in a central portion in the segment. The power cable according to claim 3, wherein the wire is disposed in each segment so that each wire is positioned in the vicinity of an outer edge portion in the segment. The power cable according to any one of claims 1 to 5, wherein at least a part of an outer surface of a wire rod provided in the conductive portion is in contact with the conductive portion. The power cable according to claim 1, wherein at least a part of the conductive portion is meandered when the conductive portion is energized. The electric power cable according to claim 1, wherein the wire provided in the conductive portion is an invar wire. The insulating layer is composed of cross-linked polyethylene,
The power cable according to claim 1, wherein the covering layer is made of vinyl chloride.

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