power lines

Abstract

This achieves both a reduction in snow accumulation and a suppression of increased wind pressure load. [Solution] The power transmission line comprises a central part and an outer stranded layer having a plurality of strands twisted together to surround the outer circumference of the central part. The outer stranded layer comprises a plurality of uneven strands, each of which has a pair of protrusions, and a plurality of sector strands, each having a sector-shaped cross section without a pair of protrusions, on its outermost circumference. The pair of protrusions on each of the plurality of uneven strands protrude outward in the radial direction of the uneven strand, are spaced apart in the circumferential direction of the uneven strand, and extend along the axial direction of the uneven strand. The plurality of uneven strands are arranged continuously within an angular range of 80° to 200° around the central axis of the central part, with the pair of protrusions facing outward in the radial direction of the outer stranded layer.

Description

Technical Field

[0001] The present disclosure relates to a power transmission line.

Background Art

[0002] When snow adheres to a general power transmission line, the snow adhering to the power transmission line gradually increases (grows) while moving along the twisting direction of the power transmission line due to its own weight. Therefore, various technologies have been adopted or considered as countermeasures against snow adhesion to the power transmission line (for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present disclosure is to achieve both a reduction in the amount of snow adhesion and an increase in the suppression of wind pressure load.

Means for Solving the Problems

[0005] According to one aspect of the present disclosure, a power transmission line is provided, comprising a central part and an outer stranded layer having a plurality of strands twisted together to surround the outer circumference of the central part, wherein the outer stranded layer comprises a plurality of uneven strands having a pair of protrusions per strand among the plurality of strands, and a plurality of sector strands having a sector-shaped cross section without the pair of protrusions, the pair of protrusions on each of the plurality of uneven strands protrude outward in the radial direction of the uneven strand, are spaced apart in the circumferential direction of the uneven strand, and extend along the axial direction of the uneven strand, and the plurality of uneven strands are continuously arranged within an angular range of 80° to 200° around the central axis of the central part, with the pair of protrusions facing outward in the radial direction of the outer stranded layer. [Effects of the Invention]

[0006] According to this disclosure, it is possible to achieve both a reduction in snow accumulation and suppression of the increase in wind pressure load. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a cross-sectional view perpendicular to the central axis of a power transmission line according to one embodiment of the present disclosure. [Figure 2] Figure 2 is a cross-sectional view perpendicular to the central axis of the uneven wire. [Figure 3] Figure 3 is a schematic diagram showing the process of snow adhering to a power transmission line until it falls off, according to one embodiment of the present disclosure. [Figure 4] Figure 4 is a schematic diagram showing the process of snow adhering to a power transmission line until it falls off, according to one embodiment of the present disclosure. [Figure 5] Figure 5 shows a snowfall testing apparatus. [Figure 6] Figure 6 shows the snow accumulation ratio to the number of continuous uneven strands in the outer stranded layer. [Figure 7] Figure 7 shows the wind pressure load ratio to the number of continuous uneven strands in the outer stranded layer. [Figure 8]FIG. 8 is a diagram showing the snow adhesion ratio with respect to the opening angle of the convex ridges of the concavo-convex line.

Mode for Carrying Out the Invention

[0008] [Description of Embodiments of the Present Disclosure] [Findings Obtained by the Inventors] First, the findings obtained by the inventors will be described.

[0009] As countermeasures against snow adhesion on transmission lines that have been adopted or considered so far, for example, the following (i) to (v) can be mentioned. (i) Anti-snow adhesion ring (ii) Wire with a ring (iii) Wire with a spiral rod (SP) (iv) Finned wire (v) Transmission lines of Patent Documents 1 and 2

[0010] However, as a result of investigations by the inventors, it was found that each of (i) to (v) gives rise to specific new problems.

[0011] (i) Anti-snow adhesion ring The anti-snow adhesion ring is a ring that grips the outer circumference of the transmission line. A plurality of anti-snow adhesion rings are arranged at intervals in the axial direction of the transmission line. As a result, the movement of snow along the twisting direction of the transmission line can be stopped by the anti-snow adhesion rings. Consequently, the snow adhering to the transmission line can be made to fall.

[0012] However, the anti-snow adhesion ring had to be attached to the transmission line manually after stringing. Therefore, the attachment work was difficult.

[0013] (ii) Wire with a ring The wire with a ring is a transmission line in which a resin corresponding to the above-described anti-snow adhesion ring is attached to the outer circumference of the transmission line during the manufacture of the transmission line. Thereby, the attachment work of the anti-snow adhesion ring after stringing can be made unnecessary.

[0014] However, in construction work such as overhead line installation, for example, when attaching a member such as a clamp to a power transmission line, it was necessary to peel off the resin corresponding to the ring from the wire with a ring. Therefore, the construction work has been difficult.

[0015] (iii) Wire with SP The wire with SP is a power transmission line in which a spiral rod is wound spirally around the outer periphery of the power transmission line. Thereby, snow adhesion to the power transmission line can be suppressed by the same principle as the anti-snow ring.

[0016] However, in construction work such as overhead line installation, it was necessary to peel off the spiral rod from the wire with SP. Therefore, the construction work for the wire with SP was also difficult for the same reason as the wire with a ring.

[0017] (iv) Finned wire The conventional finned wire is a power transmission line provided with a finned strand including fins protruding in the radial direction of the power transmission line. Snow adhesion to the power transmission line can be suppressed by the finned strand.

[0018] However, in the conventional finned wire, in order to configure the power transmission line with low loss, the strands other than the finned strand are sector-shaped strands, and the portions other than the fins in the finned strand are also configured based on the sector-shaped strand. Therefore, the weight of the conventional finned wire was heavier than that of a standard power transmission line having strands with a circular cross-section.

[0019] (v) Power transmission lines of Patent Documents 1 and 2 The power transmission line of Patent Document 1 has a plurality of ridges and a plurality of grooves on the outer peripheral surface of a segment layer formed by twisting segment strands. The ridges and grooves extend along the segment strands.

[0020] In the power transmission line of Patent Document 2, strands formed with a plurality of ridges are twisted together on the outermost periphery so that the ridges face outward.

[0021] The power transmission lines described in Patent Documents 1 and 2 differ slightly in shape from each other, but they share the common feature of having multiple protrusions per strand. These protrusions can suppress snow accumulation on the power transmission lines.

[0022] However, in the power transmission lines described in Patent Documents 1 and 2, the protrusions were arranged along the entire outermost circumference of the power transmission line. In other words, the entire outermost circumference of the power transmission line was uneven, and no smooth surface was formed. As a result, when wind blew against the power transmission line, the wind resistance experienced by the power transmission line was increased due to the protrusions arranged along the entire outermost circumference of the line. Consequently, the wind pressure load on the power transmission line was increased.

[0023] As a result of diligent study by the inventors regarding the novel problems (i) to (v) described above, the inventors have found a power transmission line configuration that can achieve both a reduction in snow accumulation and suppression of the increase in wind pressure load, thereby solving the novel problems.

[0024] The following disclosure is based on the above-mentioned findings discovered by the inventors.

[0025] <Embodiments of this disclosure> Next, embodiments of this disclosure will be listed and described.

[0026] [1] A transmission line relating to one aspect of this disclosure is: The central area and An outer stranded layer having multiple strands twisted together to surround the outer circumference of the central part, Equipped with, The aforementioned outer stranded layer is A plurality of uneven strands, each of which has a pair of protrusions, A plurality of sector-shaped wires having a sector-shaped cross-section without the pair of protrusions, It is located on the outermost perimeter, The pair of protrusions on each of the plurality of uneven wires project outward in the radial direction of the uneven wire, are spaced apart in the circumferential direction of the uneven wire, and extend along the axial direction of the uneven wire. The plurality of uneven strands are arranged continuously within an angular range of 80° to 200° around the central axis of the central part, with the pair of protrusions facing outward in the radial direction of the outer strand layer. This configuration makes it possible to achieve both a reduction in snow accumulation and suppression of the increase in wind pressure load.

[0027] [2] In the power transmission line described in [1] above, Each of the pair of protrusions is, In a cross-section perpendicular to the central axis of the aforementioned uneven wire, A pair of flat sections that are linearly inclined in opposite directions, An arc-shaped projection between the pair of flat portions, It has, In each of the pair of protrusions, the angle of opening between the pair of flat portions sandwiching the arc-shaped protrusion is greater than 40° and less than 90°. This configuration makes it possible to stably reduce the amount of snow accumulating on power lines.

[0028] [3] In the power transmission line described in [1] or [2] above, The amount of snow accumulation on the aforementioned power transmission line is less than the amount of snow accumulation on a standard power transmission line having multiple standard strands, all of which have a circular cross-section, and whose outer strand layer has a cross-sectional area of ​​0.9 times or more and 1.1 times or less than the cross-sectional area of ​​the outer strand layer of the aforementioned power transmission line. The wind pressure load on the aforementioned power transmission line is smaller than the wind pressure load on the standard power transmission line. This configuration allows for both a reduction in snow accumulation and suppression of increased wind pressure loads compared to standard power transmission lines.

[0029] [Details of the embodiments of this disclosure] Next, an embodiment of the present disclosure will be described below with reference to the drawings. However, the present disclosure is not limited to these examples, and is intended to include all modifications within the meaning and scope of the equivalents of the claims.

[0030] <One Embodiment of the Present Disclosure> (1) Power transmission lines The power transmission line 10 according to this embodiment will be described with reference to Figures 1 and 2.

[0031] In the following, the "axial direction" of the power transmission line 10 refers to the direction along the central axis of the power transmission line 10, and may be rephrased as the "longitudinal direction" in some cases. The "radial direction" of the power transmission line 10 refers to the direction from the central axis of the power transmission line 10 toward the outer circumference, and may be rephrased as the "short direction" in some cases. The same terms as those used for the power transmission line 10 may also be used for the central part 100, the outer stranding layer 200, each strand 210, the uneven strand 240, and the fan-shaped strand 260.

[0032] As shown in Figure 1, the power transmission line 10 of this embodiment comprises, for example, a central part (steel core) 100 and an outer stranded layer 200.

[0033] (center) The central part 100 is located in the center of the power transmission line 10. The central part 100 is configured to function as a tension member that bears the tension of the power transmission line 10 when it is overhead.

[0034] The central part 100 has, for example, a plurality of core wires 110 that are twisted together in a spiral. The central part 100 has, for example, a first central layer 100a and a second central layer 100b in this order, extending radially outward from the central axis of the power transmission line 10. The first central layer 100a and the second central layer 100b each have, for example, one core wire 110 and six core wires 110, respectively.

[0035] Each core wire 110 has a wire portion 112 and a covering portion 114 provided to cover the outer circumference of the wire portion 112. Examples of core wires 110 include aluminum-clad steel wire, galvanized steel wire, aluminum-clad inverted wire, and galvanized inverted wire. The core wire 110 may also be a carbon composite core wire.

[0036] (external stranded wire layer) The outer stranded layer 200 is provided so as to surround the outer periphery of the central part 100. The outer stranded layer 200 is configured to function primarily as a conductor that carries electric current during power transmission.

[0037] The outer stranded layer 200 has a plurality of strands 210. In the outer stranded layer 200, the plurality of strands 210 are arranged by twisting them together in a spiral shape so as to surround the outer circumference of the central part 100. The strands 210 include, for example, aluminum (Al) or an Al alloy.

[0038] The outer stranded layers 200 are stacked in multiple concentric circles around the central axis of the central part 100, for example. In this embodiment, the outer stranded layers 200 include, for example, a first outer stranded layer (inner stranded layer) 200a and a second outer stranded layer (outermost stranded layer) 200b, arranged in this order from the region closest to the central axis of the power transmission line 10 toward the radially outward direction. In this embodiment, the first outer stranded layer 200a and the second outer stranded layer 200b each have, for example, 10 strands 210 and 15 strands 210, respectively.

[0039] (1st outer stranded wire layer) The first outer stranded layer 200a comprises, for example, a plurality of strands 210 with a circular cross-section. In this embodiment, the first outer stranded layer 200a has, for example, 10 strands 210.

[0040] (Second outer stranded wire layer) The outermost second outer stranded layer 200b comprises, for example, a plurality of uneven strands 240 and a plurality of fan-shaped strands (smooth strands) 260.

[0041] (Uneven wire) As shown in Figures 1 and 2, the uneven wire 240 has, for example, an uneven shape on its outer circumference. Specifically, the uneven wire 240 has, for example, a raised ridge 242, an inner concave surface 248, and a side surface 249.

[0042] The convex strips 242 are provided in pairs, for example, on each individual wire 210.

[0043] Each pair of protrusions 242 on each uneven wire 240 protrudes, for example, radially outward from the uneven wire 240. When the uneven wires 240 are arranged on the outermost second outer stranded layer 200b, the pair of protrusions 242 are positioned radially outward from the outer stranded layer 200.

[0044] The pair of protrusions 242 are provided, for example, spaced apart in the circumferential direction of the uneven wire 240. As a result, a recessed ridge 247 is formed between the pair of protrusions 242 that does not penetrate the uneven wire 240 in the short direction. In a cross section perpendicular to the central axis of the uneven wire 240, the recessed ridge 247 is curved in a concave arc shape toward the central axis of the uneven wire 240, for example.

[0045] The pair of protrusions 242 extend, for example, along the axial direction of the uneven wire 240. As a result, when the uneven wire 240 is arranged on the outermost second outer stranding layer 200b, the pair of protrusions 242 extend along the direction in which the uneven wire 240 is spirally twisted.

[0046] In the recessed groove 247 formed between the pair of convex grooves 242 described above, water from partially melted snow accumulates. This promotes the movement and fall of snow attached to the power line 10. The principle behind this will be explained later.

[0047] As shown in Figure 2, each of the pair of protrusions 242 has, for example, a pair of flat portions 244 and an arc-shaped protrusion 246 in a cross section perpendicular to the central axis of the concave / concave wire 240. The pair of flat portions 244 are, for example, linearly inclined in opposite directions. The arc-shaped protrusion 246 projects in an arc shape between the pair of flat portions 244. The opening angle θ between the pair of flat portions 244 with respect to the arc-shaped protrusion 246 will be described later.

[0048] The inner concave surface 248 is, for example, positioned opposite the pair of convex ridges 242 with respect to the central axis of the uneven wire 240. In a cross-section perpendicular to the central axis of the uneven wire 240, the inner concave surface 248 is, for example, curved in a concave arc shape toward the central axis of the uneven wire 240.

[0049] The side surface 249 connects, for example, the outer ends of the pair of protrusions 242 to the inner concave surface 248. The connection between the outer ends of the pair of protrusions 242 and the side surface 249, and the connection between the inner concave surface 248 and the side surface 249, may have, for example, an R-shaped cross section (arc-shaped cross section).

[0050] (Sector-shaped wire) As shown in Figure 1, the sector-shaped wire 260 has, for example, a sector-shaped cross-section without a pair of protrusions. The sector-shaped wire 260 has, for example, an outer circumferential surface 262, an inner circumferential surface 268, and a side surface 269.

[0051] The outer surface 262 of each sector-shaped wire 260 does not have a pair of protrusions as described above, but forms an arc on the outside (large diameter portion) of the sector-shaped cross-section. That is, in a cross-section perpendicular to the central axis of the sector-shaped wire 260, the outer surface 262 is curved in a convex arc shape toward the radially outward direction of the sector-shaped wire 260, for example.

[0052] The inner circumferential surface 268 forms the arc on the inside (small diameter) of the sector cross-section. That is, the inner circumferential surface 268 is positioned opposite the outer circumferential surface 262, for example, across the central axis of the sector wire 260. The inner concave surface 248 is curved in a concave arc shape with respect to the central axis of the sector wire 260 in a cross-section perpendicular to the central axis of the sector wire 260, for example.

[0053] Side surface 269 connects, for example, the outer circumferential surface 262 and the inner circumferential surface 268. The connection between the outer circumferential surface 262 and side surface 269, and the connection between the inner circumferential surface 268 and side surface 249, may have, for example, an R-shaped cross section (circular arc-shaped cross section). Furthermore, in a cross section perpendicular to the central axis of the sector wire 260, the radius of curvature at the connection between the outer circumferential surface 262 and side surface 269 may be larger than the radius of curvature at the connection between the inner circumferential surface 268 and side surface 249.

[0054] (Arrangement of uneven and fan-shaped strands in the second outer stranded layer) As shown in Figure 1, in the outermost second outer stranded layer 200b, the multiple uneven strands 240 and the multiple fan-shaped strands 260 are arranged in a line along the circumferential direction of the second outer stranded layer 200b.

[0055] In this embodiment, the multiple uneven strands 240 are arranged continuously within an angular range of 80° to 200° around the central axis of the central part 100, with, for example, a pair of raised stripes 242 facing radially outward from the outer stranded layer 200.

[0056] On the other hand, in this embodiment, the multiple fan-shaped strands 260 are arranged continuously around the central axis of the central part 100, within a range other than the multiple uneven strands 240, with, for example, the outer peripheral surface 262 facing radially outward from the outer strand layer 200.

[0057] In this way, by setting the angle range in which multiple uneven wires 240 are arranged consecutively to 80° or more, the amount of snow accumulation on the power transmission line 10 can be reduced. "Reducing the amount of snow accumulation on the power transmission line 10" here means, for example, reducing the amount of snow accumulation on the power transmission line 10 to less than the amount of snow accumulation on a standard power transmission line, as will be described later.

[0058] On the other hand, by setting the angular range in which multiple uneven wires 240 are arranged consecutively to 200° or less, the increase in wind pressure load on the power transmission line 10 caused by the uneven wires 240 can be suppressed. "Suppressing the increase in wind pressure load on the power transmission line 10" here means, for example, keeping the wind pressure load on the power transmission line 10 below the wind pressure load of a standard power transmission line, as described later.

[0059] Multiple ridged wires 240 and multiple fan-shaped wires 260 are arranged such that their sides 249 and 269 are aligned along the radial direction of the power transmission line 10. The sides 249 of the ridged wires 240 and the sides 269 of the fan-shaped wires 260 are in contact with the sides 249 of adjacent ridged wires 240 or adjacent fan-shaped wires 260.

[0060] In this arrangement, the multiple uneven wires 240 and the multiple sector-shaped wires 260 form an annular second outer stranded layer 200b that surrounds the outer periphery of the first outer stranded layer 200a. The inner concave surfaces 248 of the multiple uneven wires 240 and the inner circumferential surfaces 268 of the multiple sector-shaped wires 260 coincide with the circumscribed circle formed by the multiple wires 210 in the first outer stranded layer 200a, or form concentric circles close to that circumscribed circle.

[0061] In the above-described arrangement, the height of the protrusions 242 of the uneven wire 240 is not limited to the height of the outer surface 262 of the sector-shaped wire 260 in the radial direction of the power transmission line 10. The height of the protrusions 242 of the uneven wire 240 in the radial direction of the power transmission line 10 may be the same as the height of the outer surface 262 of the sector-shaped wire 260, or it may be higher than the height of the outer surface 262 of the sector-shaped wire 260, or it may be lower than the height of the outer surface 262 of the sector-shaped wire 260.

[0062] (For example, the opening angle of the convex ridges in a concave / concave wire.) As shown in Figure 2, in this embodiment, the opening angle (inner angle) θ between the pair of flat portions 244 flanking the arc-shaped protrusion 246 in each of the pair of convex ridges 242 of the uneven wire 240 may be, for example, greater than 40° and less than 90°, or 45° or more and 80° or less.

[0063] By setting the opening angle of the convex ridge 242 to more than 40° and less than 90°, the amount of snow accumulation on the power transmission line 10 can be stably reduced. Furthermore, by setting the opening angle of the convex ridge 242 to 45° or more and 80° or less, the amount of snow accumulation on the power transmission line 10 can be reduced even more stably.

[0064] In this embodiment, the radius of curvature of the arc-shaped protrusion 246 in each of the pair of protrusions 242 of the uneven wire 240 is not particularly limited. However, the radius of curvature of the arc-shaped protrusion 246 may be, for example, 0.8 mm or less, or 0.6 mm or less. By setting the radius of curvature of the arc-shaped protrusion 246 to 0.8 mm or less or 0.6 mm or less, the uneven wire 240 can be manufactured stably. In addition, snow can be moved smoothly along the direction in which the uneven wire 240 is twisted. On the other hand, from a manufacturing standpoint, the radius of curvature of the arc-shaped protrusion 246 may be, for example, 0.2 mm or more.

[0065] In this embodiment, the depth of the concave ridge 247 from the virtual circumscribed circle passing through the vertex of the convex ridge 242 with the central axis of the power transmission line 10 as the center is not particularly limited. However, the depth of the concave ridge 247 may be, for example, 2% to 8% or 4% to 6% when the outer diameter of the virtual circumscribed circle described above is taken as 100%. This ensures that water from melted snow 90 can be reliably stored within the concave ridge 247.

[0066] (2) Principle of reducing snow accumulation on power lines in this embodiment Next, with reference to Figures 3 and 4, the principle of reducing snow accumulation in the power transmission line 10 of this embodiment will be explained. In Figures 3(a), 3(b), and 3(c), the upper figure is a side view of the power transmission line 10, and the lower figures are cross-sectional views perpendicular to the central axis of the power transmission line 10 at the indicated position. Figures 4(a), 4(b), and 4(c) are cross-sectional views perpendicular to the central axis of the power transmission line 10, showing the change in the state of the snow 90 from Figure 3(c) to the white arrows in Figure 4.

[0067] As shown in the upper and lower diagrams of Figure 3(a), the power transmission line 10 has a structure in which strands 210 are twisted together in a spiral. Therefore, as shown in the lower diagrams of Figure 3(a), the position of the uneven strands 240 changes in the circumferential direction of the power transmission line 10 depending on the axial position of the power transmission line 10.

[0068] Here, we assume that snow 90 has accumulated in the area of ​​the power transmission line 10 where multiple uneven wires 240 are arranged in a continuous manner, as shown in Figure 3(a).

[0069] At this time, even if snow 90 is falling, the outside temperature may be above 0°C. Furthermore, when power is being transmitted through the power transmission line 10, the temperature of the power transmission line 10 is around 90°C. As a result, some of the snow 90 attached to the power transmission line 10 melts and turns into water.

[0070] When a portion of the snow 90 melts, the water from the melted snow 90 accumulates in the grooves 247 formed between the pair of protrusions 242 of the uneven wire 240. When water accumulates in the grooves 247, the snow 90 remaining on the uneven wire 240 becomes slippery.

[0071] When the snow 90 remaining on the uneven wire 240 begins to slide, as shown in Figures 3(b) and 3(c), the weight of the snow 90 causes it to move vertically downward along the direction in which the uneven wire 240 of the power transmission line 10 is spirally twisted.

[0072] Subsequently, as shown in Figures 3(c) and 4(a), the snow 90 reaches the vertically downward side of the power transmission line 10. At this point, the snow 90 is in close contact with the power transmission line 10 at all locations except for the grooves 247 of the uneven wire 240, but at the grooves 247 of the uneven wire 240, the adhesion force of the snow 90 to the power transmission line 10 is reduced due to the water from which the snow 90 has melted.

[0073] Therefore, as shown in Figure 4(b), the snow 90 begins to detach from the power line 10 due to its own weight, with the water accumulated in the grooves 247 of the uneven wire 240 acting as the detachment point. Once the snow 90 has detached from the entire uneven wire 240, the contact points of the snow 90 with the power line 10 become smaller. As a result, the small contact points of the snow 90 with the power line 10 are no longer sufficient to hold the snow 90 in place.

[0074] As a result, as shown in Figure 4(c), the entire snow 90 attached to the power line 10 falls vertically downward due to its own weight.

[0075] In this way, the amount of snow accumulation on the power transmission line 10 can be reduced in the power transmission line 10 of this embodiment.

[0076] (3) Characteristics of power transmission lines In this embodiment, the power transmission line 10 comprises a plurality of uneven strands 240 and a plurality of fan-shaped strands 260 in the arrangement described above. As a result, the power transmission line 10 of this embodiment has the following characteristics compared to a standard power transmission line which comprises a plurality of standard strands that are all circular in cross-section and has an outer strand layer cross-sectional area that is 0.9 to 1.1 times the cross-sectional area of ​​the outer strand layer 200 of the power transmission line 10 of this embodiment.

[0077] In this embodiment, the amount of snow accumulation on the power transmission line 10 is less than, for example, the amount of snow accumulation on a standard power transmission line. Specifically, the amount of snow accumulation on the power transmission line 10 may be less than 100%, or 95% or less, when the amount of snow accumulation on a standard power transmission line under the same snowfall conditions as the power transmission line 10 is taken as 100%.

[0078] In this embodiment, the wind pressure load on the power transmission line 10 is smaller than, for example, the wind pressure load on a standard power transmission line. Specifically, the wind pressure load on the power transmission line 10 may be less than 100%, or 95% or less, when the wind pressure load on a standard power transmission line tested under the same conditions as the wind pressure load test for the power transmission line 10 is set to 100%.

[0079] (4) Summary of this embodiment This embodiment provides one or more of the following effects.

[0080] (a) In this embodiment, the outermost second outer stranding layer 200b of the power transmission line 10 comprises a plurality of uneven strands 240 and a plurality of fan-shaped strands 260. The plurality of uneven strands 240 are arranged continuously within an angular range of 80° to 200° around the central axis of the central part 100, with a pair of protrusions 242 facing radially outward from the outer stranding layer 200.

[0081] Here, we consider the case where the angle range in which multiple uneven wires 240 are arranged consecutively is less than 80°. In this case, there is a case where there is only one uneven wire 240 on the power transmission line 10, or where uneven wires 240 and fan-shaped wires 260 are arranged alternately on the power transmission line 10. In such a case, even if the snow 90 attached to the power transmission line 10 moves and reaches the vertically lower side of the power transmission line 10, there will be only one point of separation of the snow 90 due to the water accumulated in the grooves 247 of the uneven wire 240, or the separation points will be far apart from each other. As a result, it becomes difficult for the snow 90 to detach from the power transmission line 10. Consequently, it becomes difficult for the snow 90 to fall from the power transmission line 10, and the snow 90 attached to the power transmission line 10 gradually grows.

[0082] In contrast, in this embodiment, by setting the angular range in which multiple uneven wires 240 are arranged consecutively to 80° or more, the points where snow 90 detaches due to water accumulated in the grooves 247 of the uneven wires 240 can be continuously arranged over an angular range of 80° or more in the circumferential direction of the power transmission line 10 (i.e., multiple locations). As a result, when snow 90 attached to the power transmission line 10 moves and reaches the vertically downward side of the power transmission line 10, the snow 90 can be easily dropped vertically downward by the detachment points of snow 90 arranged over a wide angular range of the power transmission line 10. Consequently, it is possible to reduce the amount of snow accumulating on the power transmission line 10.

[0083] On the other hand, if the angular range in which multiple uneven wires 240 are arranged consecutively exceeds 200°, then, similar to the power transmission lines described in (v) Patent Documents 1 and 2 above, the protrusions 242 of the uneven wires 240 will be arranged over a wide angular range of the power transmission line 10. In other words, there will be no sector-shaped wires 260 with a smooth outer surface, or the angular range of sector-shaped wires 260 will be narrowed. As a result, the wind resistance experienced by the power transmission line 10 will increase due to the protrusions 242 of the uneven wires 240 that extend over a wide angular range of the power transmission line 10. Consequently, the wind pressure load on the power transmission line 10 will increase.

[0084] In contrast, in this embodiment, by setting the angular range in which multiple uneven wires 240 are arranged consecutively to 200° or less, it is possible to prevent the range in which the raised ridges 242 of the uneven wires 240 are arranged in the power transmission line 10 from becoming excessively wide. In other words, it is possible to reliably provide an angular range in which fan-shaped wires 260 having a smooth outer surface 262 with low wind resistance are arranged consecutively. This prevents the wind resistance experienced by the power transmission line 10 from increasing when wind blows against it. As a result, it is possible to suppress the increase in wind pressure load on the power transmission line 10.

[0085] As described above, this embodiment makes it possible to achieve both a reduction in snow accumulation and suppression of the increase in wind pressure load.

[0086] (b) In this embodiment, the power transmission line 10 is not fitted with any other components such as (i) snow-resistant rings, (ii) rings on wires with rings, or (iii) spiral rods on wires with SPs. This eliminates the need to attach other components such as snow-resistant rings after the power transmission line 10 has been installed. Furthermore, it eliminates the need to remove other components such as rings or spiral rods during construction work such as the installation of the power transmission line 10 in this embodiment.

[0087] (c) In this embodiment, the total cross-sectional area of ​​the outer stranding layer 200 in the transmission line 10 can be made approximately the same as the cross-sectional area of ​​a standard transmission line having multiple standard strands, all of which have a circular cross-section. This prevents the transmission line 10 from becoming excessively heavy compared to conventional (iv) finned wires.

[0088] (d) In this embodiment, each of the pair of protrusions 242 has a pair of flat portions 244 and an arc-shaped protrusion 246 in a cross section perpendicular to the central axis of the uneven wire 240. That is, the entire protrusion 242 is not formed in an arc shape, but rather the protrusion 242 has a linearly inclined flat portion 244. As a result, when the snow 90 attached to the power line 10 moves in the vertically downward direction of the power line 10, the inclination direction of the flat portion 244 of the protrusion 242 coincides with the vertically downward direction, or the inclination direction of the flat portion 244 approaches the vertically downward direction, the snow 90 can slide vertically downward along the flat portion 244, promoting the separation of the snow 90 from the power line 10. As a result, the snow 90 can be stably dropped from the power line 10.

[0089] Furthermore, in this embodiment, in each of the pair of convex ridges 242 of the uneven wire 240, the opening angle θ between the pair of flat portions 244 flanking the arc-shaped convex portion 246 is greater than 40° and less than 90°. By setting the opening angle θ of the convex ridge 242 to greater than 40°, it is possible to prevent excessive obstruction of the movement of snow 90 along the direction in which the uneven wire 240 is twisted due to excessive sharpness of the convex ridge 242. On the other hand, by setting the opening angle θ of the convex ridge 242 to less than 90°, it is possible to prevent the concave ridge 247 formed between the pair of convex ridges 242 from becoming excessively shallow. This ensures that water from partially melted snow 90 can be reliably stored within the concave ridge 247. As a result, the water stored within the concave ridge 247 can stably promote the movement and fall of snow attached to the power transmission line 10.

[0090] Thus, in this embodiment, each convex ridge 242 has a pair of flat sections 244, and the opening angle θ of the convex ridges 242 is optimized, making it possible to stably reduce the amount of snow accumulating on the power transmission line 10.

[0091] <Other embodiments of this disclosure> Although embodiments of this disclosure have been described in detail above, this disclosure is not limited to the embodiments described above, and can be modified in various ways without departing from its essence.

[0092] In the embodiments described above, examples were given in which the first outer stranded layer 200a and the second outer stranded layer 200b each have 10 strands 210 and 15 strands 210, respectively, but the disclosure is not limited to this case. The total number of strands 210 in each outer stranded layer 200 may be changed to a different number of layers than in the embodiments described above, depending on the cross-sectional area of ​​the strands 210, the shape of the uneven strands 240, etc.

[0093] In the embodiments described above, the configuration shown in Figure 1 was explained as an example of a power transmission line 10, but this disclosure is not limited to this case. In addition to the total number of strands 210 of the outer stranded layer 200 described above, for example, the number and arrangement of core wires 110 in the central part 100, the number of layers in the central part 100, and the number of layers in the outer stranded layer 200 may also be changed. [Examples]

[0094] Next, embodiments relating to this disclosure will be described. These embodiments are examples of this disclosure and the disclosure is not limited to these embodiments.

[0095] (1) Experiment 1: Angular range dependence of uneven strands in the outer strand layer First, we investigated the angular range dependence of the uneven strands in the outer stranded layer.

[0096] (1-1) Manufacturing of sample power transmission lines We manufactured power transmission lines of Sample A, which differed in the number of uneven strands, as shown below.

[0097] <Sample A> Nominal cross-sectional area of ​​power transmission lines: 410 mm² 2

[0098] [Center of Sample A] Core wire: AC wire Core wire diameter: 3.5mm Number of core wires: 6

[0099] [Outer stranded layer of sample A] Number of layers: 2 layers Strands of the first outer stranded layer: Strands with a circular cross-section Total number of strands in the first outer stranding layer: 10 Diameter of the strands in the first outer stranded layer: 4.5 mm Strands of the second outer stranding layer: uneven strands and fan-shaped strands of the above-described embodiment Total number of strands in the second outer stranding layer: 15 Number of uneven strands in the second outer stranding layer: 0 to 15 (the rest are fan-shaped strands) Equivalent outer diameter of the uneven strands in the second outer stranding layer: 4.93 mm Equivalent outer diameter of the fan-shaped strands in the second outer stranding layer: 4.54 mm

[0100] In this context, the "equivalent outer diameter" of a concave or sector-shaped wire refers to the value obtained by converting the outer diameter of the concave or sector-shaped wire to the outer diameter of a standard wire having a circular cross-section and a cross-sectional area equal to that of the concave or sector-shaped wire.

[0101] [Rough and uneven wires of Sample A] The opening angle of each of the pair of protrusions: 60°

[0102] <Sample B: Standard power transmission line> As Sample B, a standard power transmission line was manufactured. Sample B was manufactured in the same manner as Sample A, except that all the strands in the second outer stranding layer were standard strands with a circular cross-section, as specified below.

[0103] [Second outer stranded layer of Sample B] Strands of the second outer stranding layer: Standard strands with a circular cross-section Total number of standard strands in the second outer stranding layer: 16 Standard strand diameter of the second outer stranding layer: 4.5 mm

[0104] Under this condition, the total cross-sectional area of ​​the outer stranded layer of Sample B was made equal to the total cross-sectional area of ​​the outer stranded layer of Sample A when the number of uneven strands is set to four. Under this condition, the total cross-sectional area of ​​the outer stranded layer of Sample B will be within the range of 0.9 times to 1.1 times the total cross-sectional area of ​​the outer stranded layer of Sample A, regardless of which Sample A sample it is compared to.

[0105] (1-2) Evaluation The following two tests were performed on the power transmission lines of samples A and B described above.

[0106] (Snowfall test) Referring to Figure 5, the snowfall test will be described. As shown in Figure 5, the snowfall test apparatus comprises a pair of power line support sections 920, a snowfall outlet 940, and a blower (not shown). The pair of power line support sections 920 horizontally support the power line 10 at a predetermined height. The snowfall outlet 940 is installed in the ceiling and is configured to generate snow under predetermined conditions. The blower is configured to blow air from the snowfall outlet 940 toward the power line 10 supported by the pair of power line support sections 920.

[0107] Using the snowfall test apparatus described above, snow was induced on each sample power line under common snowfall conditions. The common snowfall conditions included temperature, wind speed, snowfall amount (snowfall rate), and snow quality. The temperature was set to between 1°C and 2°C. The snowfall rate was set to between 3 mm / h and 5 mm / h. The wind speed was kept constant within the range of 2 m / s and 7 m / s. The power lines were not energized.

[0108] Under the aforementioned snowfall conditions, snow was allowed to accumulate on the power lines for one minute. After one minute, the fan and snowfall were temporarily stopped, and the amount of snow accumulated on the power lines was measured. After measuring the amount of snow, snowfall was repeated for one minute under the aforementioned snowfall conditions, and the amount of snow accumulated after one minute was measured again. The above cycle was repeated until the snow fell off. When snow fell from the power lines, the measurement result of the amount of snow accumulated just before that time represents the maximum amount of snow accumulated on each sample power line. In samples where snow was difficult to fall, the time until the snow fell was longer, and the maximum amount of snow accumulated was higher. On the other hand, in samples where snow fell easily, the time until the snow fell was shorter, and the maximum amount of snow accumulated was lower. Alternatively, the amount of snow accumulated could be measured in real time as an increase in the weight of the power lines. Based on the results of the snowfall test described above, the maximum amount of snow accumulated on the power line of sample A was determined as the "Snow accumulation ratio of sample A (unit: %)" when the maximum amount of snow accumulated on the standard power line of sample B was set to 100%.

[0109] (Wind pressure load test) Using a wind tunnel, a wind of 40 m / s was blown onto each sample power line from a direction perpendicular to the power line, and the wind pressure load of each sample power line was measured. As a result, the wind pressure load of sample A was determined as the "wind pressure load ratio of sample A (in %)" when the wind pressure load of the standard power line of sample B was set to 100%.

[0110] (1-3) Results The following results were obtained for samples A and B.

[0111] (Snowfall test results) As shown in Figure 6, in Sample A, when the number of uneven wires was between 0 and 3, that is, when the angular range in which multiple uneven wires were arranged consecutively was less than 80°, the snow accumulation rate of Sample A was over 100%. In other words, in these cases, the power transmission lines of Sample A accumulated more snow than the standard power transmission lines of Sample B.

[0112] Since the snow accumulation rate exceeded 100% even when there was only one uneven wire, it is thought that the snow accumulation rate would also exceed 100% when uneven wires and fan-shaped wires were arranged alternately.

[0113] In contrast, in Sample A, when the number of uneven wires ranged from 4 to 8, that is, when the angular range in which multiple uneven wires were arranged consecutively was 80° or more, the snow accumulation rate of Sample A was less than 100%. From these results, it was confirmed that the amount of snow accumulation on power lines can be reduced by setting the angular range in which multiple uneven wires were arranged consecutively to 80° or more.

[0114] (Wind pressure load test) As shown in Figure 7, in Sample A, when the number of uneven wires was between 10 and 15, that is, when the angular range in which multiple uneven wires were arranged consecutively exceeded 200°, the wind pressure load ratio of Sample A was greater than 100%. In other words, in these cases, the wind pressure load of Sample A was greater than the wind pressure load of the standard power transmission line in Sample B.

[0115] In contrast, in Sample A, when the number of uneven wires ranged from 0 to 8, that is, when the angular range in which multiple uneven wires were arranged consecutively was 200° or less, the wind pressure load ratio of Sample A was less than 100%. From these results, it was confirmed that the increase in wind pressure load on power transmission lines can be suppressed by limiting the angular range in which multiple uneven wires were arranged consecutively to 200° or less.

[0116] (2) Experiment 2: Dependence of the opening angle of the convex ridge of the concave wire Next, we investigated the dependence of the convex ridges on the opening angle of the concave and concave wires.

[0117] (2-1) Manufacturing of sample power transmission lines As Sample C, a power transmission line was manufactured in the same manner as Sample A, except that the opening angle of the convex ridges of the convex wires was changed as follows, and the number of convex and convex wires was four.

[0118] [Sample C's uneven surface lines] The opening angle of each of the pair of protrusions: 35° to 100°

[0119] (2-2) Evaluation Similar to Experiment 1, a snowfall test was conducted on Sample C. The amount of snow accumulation on Sample C's power transmission line was determined as the "Snow accumulation ratio of Sample C (in %)" when the amount of snow accumulation on Sample B's standard power transmission line was set to 100%.

[0120] (2-3) Results As shown in Figure 8, in the range where the opening angle of the convex ridges of sample C is between 35° and 100°, the snow accumulation rate of sample C was less than 100%, regardless of the opening angle.

[0121] However, in sample C, a clear decrease in snow accumulation was observed when the opening angle of the convex ridges was greater than 40° but less than 90°. From these results, it was confirmed that the amount of snow accumulation on power lines can be stably reduced by setting the opening angle of the convex ridges of the uneven wire to greater than 40° but less than 90°.

[0122] In particular, when the opening angle of the convex ridges was between 45° and 80°, the snow accumulation rate was 95% or less. From these results, it was confirmed that by setting the opening angle of the convex ridges of the uneven wire between 45° and 80°, the amount of snow accumulation on power transmission lines can be reduced even more stably.

[0123] <Note> The following appendices describe the embodiments of this disclosure. The embodiments referenced by the numbers in brackets [] to which the following appendices depend correspond to the embodiments described in <Embodiments of this Disclosure>.

[0124] [4] Each of the plurality of sector-shaped wires has an outer surface that forms the outer arc of the sector-shaped cross-section, The plurality of fan-shaped strands are arranged continuously around the central axis of the central part, within the range other than the plurality of uneven strands, with their outer surfaces facing outward in the radial direction of the outer strand layer. A power transmission line as described in any one of [1] through [3]. [Explanation of Symbols]

[0125] 10 Power transmission lines 90 Snow 100 center 100a 1st central layer 100b 2nd central layer 110 Core wire 112 Wire section 114 Covering part 200 external strand layer 200a 1st outer strand layer 200b 2nd outer strand layer 210 strands 240 Uneven wire 242 convex stripes 244 Flat area 246 Arc-shaped protrusion 247 Concave line 248 Inner concave surface 249 Side view 260 Fan-shaped wire 262 Outer surface 268 Inner surface 269 ​​Side view θ Opening angle

Claims

1. It is a power transmission line, The central area and An outer stranded layer having multiple strands twisted together to surround the outer circumference of the central part, Equipped with, The aforementioned outer stranded layer is A plurality of uneven strands, each of which has a pair of protrusions, A plurality of sector-shaped wires having a sector-shaped cross-section without the pair of protrusions, It is located on the outermost perimeter, The pair of protrusions on each of the plurality of uneven wires project outward in the radial direction of the uneven wire, are spaced apart in the circumferential direction of the uneven wire, and extend along the axial direction of the uneven wire. The plurality of uneven strands are arranged continuously within an angular range of 80° to 200° around the central axis of the central part, with the pair of protrusions facing outward in the radial direction of the outer strand layer. Power lines.

2. Each of the pair of protrusions is, In a cross-section perpendicular to the central axis of the aforementioned uneven wire, A pair of flat sections that are linearly inclined in opposite directions, An arc-shaped projection between the pair of flat portions, It has, In each of the pair of protrusions, the opening angle formed by the pair of flat portions sandwiching the arc-shaped protrusion is greater than 40° and less than 90°. The power transmission line according to claim 1.

3. The amount of snow accumulation on the aforementioned power transmission line is less than the amount of snow accumulation on a standard power transmission line having multiple standard strands, all of which have a circular cross-section, and whose outer strand layer has a cross-sectional area of ​​0.9 times or more and 1.1 times or less than the cross-sectional area of ​​the outer strand layer of the aforementioned power transmission line. The wind pressure load on the aforementioned transmission line is smaller than that on the standard transmission line. A power transmission line according to claim 1 or claim 2.

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