JPH0135446B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Background and Objectives of the Invention] The present invention relates to a low-noise, low-vibration electric wire that can significantly reduce noise and vibration caused by wind pressure in an overhead power transmission line or an overhead ground wire.

Since overhead power lines and overhead ground wires are installed high up on steel towers, it is difficult to avoid noise caused by wind pressure or vibrations caused by the wind pressure. Wind noise has a negative impact on environmental conditions,
Wind pressure vibrations pose a risk of causing accidents such as fatigue rupture of electric wires.

It has been discovered that wind noise in the former case can be suppressed by winding a spiral wire around the outer circumference of the electric wire, and the applicant has already made a proposal, but in this case, a spiral wire manufactured separately from the electric wire is prepared. Furthermore, it is necessary to attach a spacecraft or the like to the wire after the overhead wire is installed, which is unavoidably dangerous work.

Furthermore, since the strands protrude from the surface of the electric wire, corona characteristics are affected, and there is the problem of audible noise. Further, the weight of the wire increases due to the spiral wire, and an increase in wind pressure due to the protruding spiral wire must be considered, which is not necessarily preferable for the wind pressure vibration.

Research on wind noise on power transmission lines has made great progress in recent years, and it has become possible to predict routes where wind noise is likely to occur in advance. Therefore, instead of attaching a separate member to the wire to prevent wind noise, the wire itself has a special shape that does not generate noise.
All of the above-mentioned problems can be solved by installing the special electric wire in a dangerous area where wind noise is expected to occur.

Based on this knowledge, the applicant has already proposed an electric wire with a cross-sectional configuration as shown in Fig.
59-96603). In this method, at least the outermost twisted wire layer of the electric wire is constituted by fan-shaped segment wires, and a step is formed on the outer peripheral surface by the thinner wires 1' and the thicker wires 2' in the radial direction.
Low height part 10'a and high height part 10'b
and are formed so as to be positioned symmetrically.

It has been found that the electric wire 10' constructed in this manner not only has an excellent low-noise effect, but also greatly reduces wind pressure vibration and audible noise caused by corona.

The present invention aims to provide an electric wire that further improves the already proposed electric wire and exhibits even more significant noise reduction and vibration prevention effects.

[Detailed Summary of the Invention] That is, the gist of the present invention is that at least the outermost strand of the stranded wire is constituted by a fan-shaped segment element wire, and the outer periphery thereof has a high height portion and a low height portion, By forming steps so that they are symmetrically located, and forming another step higher in the higher height portion, noise prevention effects and vibrations are improved compared to the previously proposed electric wire shown in Fig. 1. It has been discovered that the preventive effect can be significantly increased.

[Example] What is shown in FIG. 2 is an electric wire 10 according to the present invention.
FIG. 2 is a cross-sectional view showing one embodiment of the present invention, in which the inner layer portions are each composed of wires having a circular cross section.
Of course, even the inner layer may be composed of fan-shaped segment wires as in the case of FIG. 1.

The outermost stranded wire layer is formed by twisting three types of fan-shaped segment wires 1, 2, and 3, each having a different thickness in the radial direction of the electric wire. The strands 2, 2 having a large thickness are arranged symmetrically as shown in FIG. Of course, this symmetry does not mean complete symmetry in a geometric sense, but just a roughly relative relationship, and it does not matter if there are some discrepancies in the numbers.

A low height portion 10a is formed by the thin wires 1, 1, and a high height portion 10b is formed by the thick wires 2, 2. In this state, there is no difference from the case shown in FIG. 1 described above. The present invention is characterized in that a third step portion 10c, which is still higher, is formed by mixing and twisting thicker strands 3 in this high-height portion 10b. In this embodiment, the number of mixedly twisted strands 3 is one high part 10b.
It goes without saying that there may be more than one line, although there is one line within the range. The position is not necessarily limited to the central position of the tall portion 10b.

FIG. 3 is a schematic diagram showing the external configuration of FIG. 2. The outer diameter formed by the high part 10b is D, the difference between the low height part 10a and the high height part 10b is _t1 , and the difference between the high height part 10b and the step part 10c which is one step higher is D. The results of wind tunnel experiments are shown in FIGS. 4 and 6, where the difference is t ₂ , the central angle of the higher height portion 10b is Θ ₁ , and the central angle of the step portion 10c, which is one step higher, is Θ ₂ .

FIG. 4 is a diagram showing the effect of the value of t ₂ /t ₁ on wind noise reduction. t ₂ /t ₁ =0 indicates the case of the previously proposed configuration shown in FIG. In this experiment, the central angle Θ ₁ =90°, t ₁ =2 mm, and D = 40 mm. In order to form an even higher stepped portion 10c, wires are mixed and twisted as shown in _{FIG .}
= 1/5 and Θ ₂ /Θ ₁ = 2/5, Θ ₁ = 90°,
Wires with D=40 mm and different values of t ₂ /t ₂ were made, and wind tunnel experiments were conducted at a wind speed of 15 m/s to investigate the relative level reduction. As a result, it can be clearly seen that when t ₂ /t ₁ =0.5 or less, the effect of the step portion 10c which is one step higher is hardly exhibited, but when it becomes 0.5 or more, the relative level decreases very markedly. Such experiments were attempted with other commercial-sized electric wires of different diameters, but the results were largely the same and slightly different. It was also found that when Θ ₁ is the same, the smaller Θ ₂ is, the more pronounced the effect is. However, if it is made too small, a peak will be formed in some areas, so care must be taken to prevent corona noise. A particularly preferred range of Θ ₁ was 60°<Θ ₁ <120°.

Furthermore, FIG. 6 is a plot of the ratio of lift fluctuations due to wind pressure between the conventional 810 mm ² ACSR (steel core aluminum stranded wire) and the 810 mm ² ACSR according to the present invention.

810mm ² ACSR outer diameter 38mm, 810mm ² according to the invention
ACSR is D = 38mm, t ₁ = 2mm, t ₂ in Figure 3.
= 1 mm, therefore t ₂ /t ₁ = 0.5, Θ ₁ = 90°, and Θ ₂ /Θ ₁ = 1/5.

As is clear from Fig. 6, as the wind speed increases, the lift of the electric wire according to the present invention is significantly reduced, and the wind pressure vibration is significantly reduced. It has also been found that it is possible to omit a damper for absorbing vibrations of electric wires. Although this kind of vibration prevention effect is fully recognized even with the shape shown in Figure 1,
In the case of the present invention, similar to the above-mentioned noise prevention effect, it is even more noticeable.

Note that the wires 1 and 2 need to be fan-shaped segment wires, but the wire 3 for forming the step portion which is one step higher may be a wire with a circular cross section.

Furthermore, in forming the step surface, there are five steps instead of three steps 10a, 10b and 10c as shown in FIG.
There may be four stages 10a, 10b, 10c and 10d as shown in the figure. It was also found that using multiple stages in this way makes it more difficult to manufacture, but the effect can be further improved even if Θ ₂ /Θ ₁ becomes large.

[Effects of the Invention] It is believed that the reason why the electric wire according to the present invention has the remarkable noise prevention effect and vibration suppression effect as described above is because its special outer peripheral structure has a large effect on air flow. It will be done.

It is noteworthy that by providing such electric wires, we were able to not only prevent noise without the need for special attachments, but also reduce the vibrations of the wires, and are highly valued in the industry. It is something that should be done.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of the already proposed electric wire, Fig. 2 is a cross-sectional view showing an embodiment according to the present invention, Fig. 3 is a schematic cross-sectional view of Fig. 2, and Fig. 4 is a ratio of stepped portions and noise. FIG. 5 is a partially omitted sectional view showing another embodiment of the present invention, and FIG. 6 is a diagram showing the development of wind speed and lift fluctuations. 1, 2, 3: Element wire, 10a, 10b, 10c,
10d: Step surface.

Claims (1)

[Claims] 1. At least the outermost stranded wire layer of the stranded wires is composed of fan-shaped segment wires, and on the outer peripheral surface thereof, high height parts and low height parts are respectively located symmetrically, 1. A low-noise, low-vibration electric wire characterized in that a step is formed, and a step portion that is one step higher is formed in the high-height portion.