JPS61245409A - Low noise wire - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electric wire in which a plurality of strands are arranged in concentric layers, and particularly relates to the prevention of noise generated from the electric wire during strong winds. It is something.

[Problems to be Solved by the Prior Art and the Invention] During strong winds, power transmission lines may generate a low humming noise. This noise often occurs when the wind hits the power line at a nearly right angle, especially during the winter season when the wind direction is almost constant.

According to measurements with an indicating sound level meter, there is almost no difference in the noise level (horn) between when power lines are not installed and when they are installed. However, the noise from this power line is 1
Since it has a low dominant frequency component of around 00 to 200H2, it can be clearly distinguished from surrounding background noise. This noise is an unpleasant sound that resonates in your stomach, similar to the sound of an airplane flying in. As a result, complaints may be received from people living near the power lines whenever noise occurs.

As electricity demand increases, it is conceivable that taller steel towers will be used to support power transmission lines. Furthermore, as fibers for optical communication are incorporated into electric wires, it is predicted that the electric wires will have multiple conductors and that equipment will become larger. Because of this, there is a possibility that noise will occur more frequently. Therefore, this noise problem is expected to be a hindrance to the construction of power transmission lines.

The main cause of this noise is the Karman vortex that is generated at the rear of the wire when wind hits the wire. This has been confirmed because the dominant frequency of the noise generated from the electric wires almost matches the frequency of the Karman vortex. Note that the frequency of the Karman vortex is calculated using f=o and 185v/d. f is the frequency [Hzl, v is the wind speed [m/sl, d is the outer diameter of the wire [11
, 0°185 indicates the Strohals number.

Karman vortices are regular vortices that form on the rear surface of a cylinder when fluid flows along the curved surface of the cylinder.

An electric wire with a smooth outer peripheral surface has a shape that easily generates this Karman vortex.

Therefore, an object of the present invention is to provide an electric wire in which Karman vortices are less likely to occur and which are less likely to cause noise.

[Means for solving the problem] In a low-noise electric wire in which a plurality of strands are provided in concentric layers, the outer periphery can be reduced by removing one or more of the strands forming the outermost layer. A spiral groove extending in the length direction of the wire is provided on the surface, and spacer wires are placed inside the groove to maintain a constant distance between the wires located on both sides of the groove. The outer layer is characterized by using a wire having a smooth outer peripheral surface.

[Function] In the low-noise electric wire according to the present invention, a square groove is provided by removing one or more of the strands forming the outermost layer. Since the flow along the curved surface of the wire is further disturbed by the square grooves, the generation of Karman vortices is advantageously prevented. Furthermore, a spacer wire is arranged inside the groove. Therefore, the spacing between the strands on both sides of the groove is kept constant, and the shape of the groove is maintained.

[Example] FIG. 1 shows an example of a low-noise electric wire according to the present invention. The basic structure is that of conventional steel core aluminum electric wire <AC
3R) is almost the same.

A steel core 2 runs through the center of this low-noise electric wire 1. The inner layer 3 surrounding the steel core 2 is made up of a plurality of round aluminum wires 4. The outer layer portion 5 surrounding the inner layer portion 3 is made of a deformed aluminum wire 6 having a cross-sectional shape such that the outer peripheral surface is smoothed. A groove 8 is provided in the outermost layer 7 by removing one or more of the strands.

This groove 8 disturbs the flow of wind along the outer peripheral surface of the low-noise electric wire 1, thereby preventing the generation of Karman vortices. Therefore, noise from the electric wire caused by the Karman vortex is prevented.

A spacer wire 9 is arranged inside this groove 8 . Due to the presence of the spacer wire 9, the deformed aluminum wire 6 on both sides of the groove
The spacing between the grooves 8 and 8 is maintained constant, and the shape of the groove 8 is maintained.

More preferably, the spacer wire 9 is provided with outwardly projecting fins 10. When wind hits this low-noise electric wire 1, an outward airflow is generated along the fins 10, so that the effect of disturbing the airflow that follows the Karman vortex is further enhanced.

In order to exhibit the effect of preventing the occurrence of Karman vortices, the grooves 8 are preferably provided as follows. When the outer diameter of the low-noise electric wire 1 is d, the groove 8 (7) width X is:
0.15d or o, 3d, 83Y is 0.15d. When fins 10 are provided, the width of the fins 10
, height y are both 0.03d. Further, since the groove 8 is provided in a spiral shape, the spiral interval is preferably 3d to 15d. The direction of the spiral may be either S (cloth wound) or Z (left handed).

The groove 8 provided in this way prevents the generation of Karman vortices.
[7i It is possible to fully demonstrate the effect of

Further, since the groove 8 is provided in a spiral shape, the effect of reducing the wind pressure load applied to the low-noise electric wire 1 can be expected. This is because the wind whose direction is changed by the groove 8 interferes with the wind hitting the electric wire at right angles and weakens it. In fact, in the low-noise electric wire 1 according to the embodiment, the effectiveness coefficient can be reduced by about 30% to 50% compared to the conventional electric wire. By reducing the wind pressure load on the wires, the burden on the steel towers that support the wires will also be reduced.

Note that because the groove 8 is provided, the apparent cross-sectional area of the low-noise electric wire 1 is smaller than that of a conventional electric wire. If the cross-sectional area becomes smaller, problems such as a decrease in current capacity and a decrease in mechanical strength arise. However, in this embodiment, deformed aluminum wires 6 are used in the outermost layer and the next layer of the low-noise electric wire 1, so that the gaps between the wires are made small and the total cross-sectional area of the wires is made as large as possible. Therefore, the low-noise electric wire 1 can maintain the necessary current capacity and mechanical strength while maintaining the same outer diameter. In addition, the apparent outer diameter of the low-noise electric wire 1 is N1m compared to the conventional one.
Therefore, conventional wire accessories can be used. Additionally, construction works such as line extensions, overhead wires, and tension lines can be carried out as usual.

In the embodiment shown in FIG. 1 described above, only one groove 8 is provided, but two or three or more grooves 8 may be provided as in the low-noise electric wire 11 shown in FIG. In the embodiment shown in FIG. 1, the spacer wire 9 is provided with fins 10, but spacer wires without fins may be used as shown in FIGS. 2 to 4. Furthermore, in the embodiment shown in FIG. 1, three wires are removed in order to provide the groove 8, but one wire is removed as shown in FIGS. 3 and 5, or one wire is removed as shown in FIGS. 2 and 6. 2 bottles is fine. In short, the width of the groove should be a width suitable for preventing the generation of Karman vortices.

Further, in the embodiment shown in Fig. 1, aluminum wire is used as the wire material, but aluminum alloy wire, steel wire, steel wire coated with aluminum or copper, copper or copper alloy wire can also be used. .

Experimental Example 1 A round bar with outer diameter d = 3Qlllllll and length 1- is placed at wind speed V.
- When exposed to the 2011/S wind, a noise similar to the sound of an airplane flying is generated. Frequency analysis of this noise revealed that the dominant center frequency was 125 Hz and the noise level was 74.5 dB (C) as shown in the bar graph of FIG.

The same round bar provided with one longitudinally extending groove of the predetermined dimensions described above was exposed to wind at a wind speed of V-20111/S, and the noise level at a dominant center frequency of 125H2 was measured. The noise level is 56.4 dB (C), which is 18.1 dB (C) compared to the round bar as you can see from the difference in the graph.
C) It was decreasing. The noise at this time was barely audible. It has been found that providing vertically extending grooves on the surface of an object such as a round bar is effective in preventing noise generated therefrom.

[Effects of the Invention] As described above, since the outer peripheral surface of the low-noise electric wire according to the present invention is provided with a spiral groove extending in the length direction,
Generation of Karman vortices is prevented.

Therefore, noise from the electric wire, which is mainly caused by Karman vortices, is prevented.

Low-noise electric wires that exhibit such effects can be advantageously used as overhead power transmission lines, overhead ground wires, optical composite overhead power transmission lines, optical composite overhead ground wires, and the like.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of a low-noise electric wire according to the present invention. FIG. 2 is a sectional view showing another example of the low-noise electric wire according to the present invention. FIG. 3 is a partial sectional view of a low-noise electric wire according to the present invention. FIG. 4 is a partial cross-sectional view showing another example of the low-noise electric wire according to the present invention. FIG. 5 is a partial cross-sectional view showing still another example of the low-noise electric wire according to the present invention. FIG. 6 is a partial cross-sectional view showing still another example of the low-noise electric wire according to the present invention. FIG. 7 is a graph of an experimental example showing the effects of the present invention. In the figure, 1 is a low-noise electric wire, 6 is a deformed aluminum wire, 7 is an outermost layer, 8 is a groove, 9 is a spacer wire, and 10 is a fin. Figure 1

Claims (6)

[Claims] (1) In a low-noise electric wire using strands in which a plurality of strands are arranged in concentric layers and at least the outer peripheral surface of the outermost layer is smooth, the strands forming the outermost layer are By removing one or more wires, a spiral groove extending in the length direction of the wire is provided on the outer circumferential surface, and in order to maintain a constant interval between the wires located on both sides of this groove, A low-noise electric wire characterized by the arrangement of spacer wires. (2) The groove is provided to have a width of 0.15 d to 0.3 d and a depth of 0.15 d relative to the outer diameter d of the low-noise electric wire. 1st
Low-noise electric wires as described in Section. (3) The low-noise electric wire according to claim 1 or 2, wherein the spacer wire is provided with a fin that projects outward. (4) The fin has a width of 0.03 with respect to the outer diameter d.
The low-noise electric wire according to claim 3, characterized in that the wire has a height of 0.03d. (5) The low-noise electric wire according to any one of claims 1 to 4, wherein a plurality of the grooves are provided. (6) At least the outermost layer of the low-noise electric wire and the following 1
Claims 1 to 5, characterized in that the layer is made of wire having a smooth outer peripheral surface.
The low-noise electric wire described in any of the paragraphs.