Electric wire

Abstract

To provide an electric wire less affected by wind pressure in comparison with conventional electric wires.SOLUTION: An electric wire comprises a conductor and a covering material for covering the conductor. The covering material has a plurality of crest parts projecting outward in the radial direction in the cross section perpendicular to the lengthwise direction of the electric wire. Each of the crest parts is arranged in the circumferential direction in the cross section. The number of the crest parts is 30 to 48, and the height of the crest part is 0.10 mm or more and 0.2 mm or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electric wire. [Background technology]

[0002] 2. Description of the Related Art Electric wires capable of reducing the effects of wind pressure are known.

[0003] As such an electric wire, for example, Patent Document 1 describes an electric wire that includes a conductor and a covering material that covers the conductor, and in a cross section perpendicular to the longitudinal direction of the electric wire, the covering material has a plurality of ridges formed so as to protrude radially outward. According to this electric wire, since the covering material has a plurality of ridges, when the wire is exposed to wind, the pressure difference between the windward side and the leeward side via the electric wire is reduced, and the wind pressure load applied to the electric wire is reduced. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4383038 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional power lines are not able to fully reduce the effects of strong wind pressure (for example, wind pressure caused by wind speeds of 60 m / s or more) that has accompanied the increase in the power of typhoons in recent years, which could cause damage to the power lines themselves and even the collapse of utility poles.

[0006] In view of the above circumstances, an object of the present invention is to provide an electric wire which is less susceptible to the effects of wind pressure as compared with electric wires of the prior art. [Means for solving the problem]

[0007] After extensive research, the inventors discovered that the above problem could be solved by increasing the number of peaks compared to the wires of the prior art and setting the height of the peaks to a predetermined value, thereby completing the present invention.

[0008] That is, the electric wire according to the present invention is An electric wire comprising a conductor and a covering material covering the conductor, the covering material has a plurality of ridges formed so as to protrude radially outward in a cross section perpendicular to a longitudinal direction of the electric wire, In the cross section, the peaks are aligned in the circumferential direction, The number of the ridges is 30 to 48, and the height of the ridges is not less than 0.10 mm and not more than 0.2 mm.

[0009] According to this configuration, the number of peaks is 30 to 48 and the height of the peaks is 0.10 mm or more and 0.2 mm or less, so that the influence of wind pressure is reduced compared to the electric wire of the prior art. For example, the influence of wind pressure can be reduced for a wind speed of 60 m / s or more.

[0010] Moreover, the electric wire according to the present invention preferably comprises: In the cross section, the diameter of a circumscribing circle that circumscribes the peak portion is 10.8 to 26.1 mm.

[0011] According to this configuration, the diameter of the circumscribing circle is 10.8 to 26.1 mm, so that the influence of wind pressure is further reduced. Effect of the Invention

[0012] As described above, according to the present invention, it is possible to provide an electric wire which is less susceptible to the effects of wind pressure as compared with the prior art. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view of the electric wire according to the first embodiment. [Diagram 2]FIG. 2 is a partially enlarged cross-sectional view of the electric wire according to the second embodiment. [Diagram 3] FIG. 3 is a graph showing the evaluation results of the number of peaks and the height of the peaks in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an electric wire according to a first embodiment of the present invention will be described with reference to the drawings. In the following, a cross section perpendicular to the longitudinal direction of the electric wire may be simply referred to as a cross section.

[0015] The electric wire 1 of this embodiment is used as an overhead transmission line. As shown in the cross-sectional view of Fig. 1, the electric wire 1 includes a conductor 10 and a covering material 20 that covers the conductor 10.

[0016] The conductor 10 is preferably an aluminum-core stranded steel wire (ACSR) formed by twisting a plurality of aluminum wires around a galvanized steel wire, or an aluminum-core stranded steel wire (ACSR / AC) formed by twisting a plurality of aluminum wires around an aluminum-covered steel wire. The conductor 10 is not limited to ACSR or ACSR / AC, and may be, for example, an aluminum stranded wire formed by twisting only the aluminum wires together, or a copper stranded wire formed by twisting a plurality of copper wires together.

[0017] The outer diameter of the conductor 10 is usually 7.2 to 18.7 mm. The outer diameter of the conductor 10 can be measured with a vernier caliper by the measurement method specified in JIS C 3005:2014 (Test method for rubber and plastic insulated wires) after the covering material 20 is peeled off from the electric wire 1.

[0018] The covering material 20 is made of a resin such as polyethylene, cross-linked polyethylene, polyvinyl chloride, or rubber.

[0019] The coating material 20 has a plurality of peaks 21 formed to protrude radially outward in the cross section. The peaks 21 are arranged along the circumferential direction of the electric wire 1. As a result, the electric wire 1 of this embodiment has a plurality of valleys 22 where the coating material 20 is not present between the peaks 21. The valleys 22 of this embodiment are formed to recess radially inward in the cross section.

[0020] In the cross section of each of the peaks 21 in this embodiment, both ends 211 in the circumferential direction form a pair of protruding base ends 211. In this embodiment, adjacent peaks 21 are formed to be continuous with each other while sharing the protruding base end 211. In other words, in the electric wire 1 of this embodiment, the number of peaks 21 and the number of protruding base ends 211 are the same (in FIG. 1, the number of peaks 21 is 37, and the number of protruding base ends 211 is 37).

[0021] In the present embodiment, the surface of each of the peaks 21 in the cross section is formed in a curved shape. More specifically, the surface is formed so that a circular arc shape protruding radially outward and a circular arc shape recessed radially inward are alternately repeated. Also, each of the peaks 21 is formed so as to have a vertex that is the point farthest radially outward from the center of the electric wire 1. As a result, a circumscribing circle C that circumscribes the vertex of each of the peaks 21 can be drawn in the cross section. The diameter R of the circumscribing circle C represents the outer diameter of the electric wire 1. The diameter R of the circumscribing circle C (i.e., the outer diameter of the electric wire 1) can be measured using a vernier caliper according to the measurement method specified in JIS C 3005:2014.

[0022] It is important that the number of the peaks 21 is 30 to 48, and the height h is 0.10 mm or more and 0.2 mm or less. The height h is preferably 0.10 mm or more and 0.20 mm or less, and may be 0.10 mm or more and less than 0.2 mm. The number of the peaks is preferably 40 to 48, and in this case, the height h is preferably 0.10 mm or more and 0.16 mm or less, and more preferably 0.10 mm or more and 0.15 mm or less. The number of the peaks may be 37, and the height h is 0.15 mm or more and 0.18 mm or less. This reduces the influence of wind pressure on the electric wire 1 under strong wind speed conditions (for example, conditions of 60 m / s or more). Among the multiple peaks 21, the heights of 80% or more of the peaks are preferably within the above range, and more preferably 90% or more of the peaks are within the above range.

[0023] The height h of the peak 21 can be obtained by measuring the heights of all the peaks individually and calculating the arithmetic mean. The height can be measured by observing the cross section of the electric wire 1 using a magnifying microscope. When measuring the height of one peak in cross section observation, the height is measured based on a straight line connecting the protruding base ends of the peak. In other words, when measuring the height of one peak, the shortest distance between the apex of the peak and the straight line is measured.

[0024] Although one embodiment has been shown above as an example, the electric wire according to the present invention is not limited to the configuration of the above embodiment. The electric wire according to the present invention is also not limited by the above-mentioned action and effect. The electric wire according to the present invention can be modified in various ways without departing from the gist of the present invention.

[0025] For example, the electric wire 1 may have a cross-sectional shape as shown in Fig. 2. That is, in the electric wire 1 according to the second embodiment shown in Fig. 2, the covering material 20 has a plurality of peaks 21 formed so as to protrude radially outward in the cross section, and a flat portion 23 provided between the peaks 21 and having a flat surface. In the cross section, the surface of the flat portion 23 is formed along the circumscribing circle C. In the second embodiment, since the flat portion 23 is formed between the peaks 21, each of the peaks 21 has a pair of protruding base ends 211. In other words, in the electric wire 1 according to the second embodiment, the number of protruding base ends 211 is twice the number of the peaks 21. EXAMPLES

[0026] The present invention will be further described below with reference to examples, but the present invention is not limited to these.

[0027] [Evaluation of the number and height of peaks] As shown in Table 1, wires were manufactured by varying the number and height of ridges, and the following wind tunnel test was conducted in an environment with a wind speed of 60 m / s to evaluate the low wind pressure performance. Specifically, a wire (outer diameter Ch) with a circular cross section (without ridges) corresponding to each wire in Table 1 was separately manufactured and a wind tunnel test was conducted. Then, the wind pressure load reduction rate Re (%), which indicates the percentage by which the wire with ridges reduces the wind pressure load compared to a circular wire, was calculated using the following formula, and the low wind pressure performance was evaluated using Re as an index. The results are shown in Table 1 and Figure 3. (Re calculation formula) Re=(F 0 -F) / F 0 ×100 Re: Wind pressure load reduction rate (%) F 0 : Wind pressure load on a circular cross-section wire (N / m) F: Wind pressure load on the wire with crests (N / m)

[0028] [Wind tunnel testing] A three-component force gauge was attached to both ends of an electric wire (effective sample length placed in the wind tunnel: 50 cm), and the wire was fixed in the wind tunnel so that the length direction of the electric wire was perpendicular to the wind flow direction. The wind speed was set to 60 m / s, and the load per 50 cm was measured. The test was carried out under atmospheric pressure (approximately 100 kPa) and at 22 to 25°C. The measured values ​​of the wind pressure load and resistance coefficient Cd at a wind speed of 60 m / s were calculated using the following formula. (Drag coefficient calculation formula) F = P C d S (1) Fv=ρV 2 CdS / 2 (2) F: Load per 50cm (N / 50cm), P: measured dynamic pressure (kPa), Cd: Resistance coefficient, S: Projected area (m 2 ) = outer diameter of wire (m) × effective sample length inside the wind tunnel (m), Fv: Wind pressure load at wind speed V (N / m), ρ: Air density (1.1277kg / m 3 (Assumed.)

[0029] [Table 1]

[0030] As shown in Table 1 and Figure 3, the electric wires with 30 to 48 peaks complete turbulent transition when the peak height is in the range of 0.10 to 0.20 mm. Therefore, these electric wires can be evaluated as having excellent low wind pressure performance. Furthermore, it was found that the electric wires with 40 to 48 peaks and a peak height of 0.10 to 0.16 mm have better low wind pressure performance under strong wind pressure. Another example of an electric wire with equivalent low wind pressure performance is a wire with 37 peaks and a height h of 0.15 mm to 0.18 mm. [Explanation of symbols]

[0031] 1: electric wire, 10: conductor, 20: coating material, 21: peak, 211: protruding base end, 22: valley, 23: flat portion, C: circumscribed circle

Claims

[Claim 1] An electric wire comprising a conductor and a covering material covering the conductor, the covering material has a plurality of ridges formed so as to protrude radially outward in a cross section perpendicular to a longitudinal direction of the electric wire, In the cross section, the plurality of peaks are arranged in a circumferential direction, and surfaces of the plurality of peaks are formed so as to alternately form arc shapes protruding radially outward and arc shapes recessed radially inward, The number of the ridges is 30 to 48, and the height of the ridges is 0.10 mm or more and 0.2 mm or less, In the cross section, a circumscribing circle circumscribing the peak portion has a diameter of 10.8 to 26.1 mm.

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