JPH024083B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Background and Objectives of the Invention] The present invention relates to an improved wind noise prevention electric wire that effectively reduces corona noise (hereinafter referred to as AN) emitted by an overhead power transmission line.

Overhead power transmission lines connected between steel towers may generate noise due to wind pressure, and the applicants have developed a spiral strand S around the electric wire W as shown in Fig. 1 as an electric wire that can prevent this. We proposed a low wind noise electric wire made by wrapping (For example, Tokuko Sho 53-
14146) The low wind noise electric wire with this shape exhibits an excellent wind noise prevention effect, but since the strands S protrude from the surface of the electric wire W, so-called audible noise (i.e., the above-mentioned AN) due to corona occurs in rainy weather. sometimes became a problem.

Therefore, the applicants proposed an electric wire having a special shape as shown in the cross-sectional view of FIG. 3, for example, as an electric wire that can effectively prevent wind noise and also prevent the generation of the corona noise. In this method, at least the outermost wire is made up of a segment wire, and the shape of the wire is made up of a bulky wire 1 and a small bulky wire 2 in the radial direction of the wire. A high step surface 10a on the outer peripheral surface of 10
This is achieved by symmetrically forming a low stepped surface 10b. By configuring like this,
By exhibiting an external structure as schematically shown in FIG. 2, and selecting an appropriate value for the difference h between the high step surface 10a and the low step surface 10b, as shown in FIG. It has been found that it can exhibit a remarkable noise prevention effect. In this case, if the central angle of the high level difference surface is θ, the height of the level difference is h, the pitch of the high level difference part is P, and the outer diameter of the high level difference surface is _D1 , then the optimum noise prevention effect is determined. It has become clear through numerous demonstration experiments that the ranges are θ=60 to 120°, h≧1 mm, and P=10D ₁ to 15D ₁ .

However, when the electric wire shown in FIG. 3 was further examined in detail, it was found that there was a problem with the behavior of rainwater flowing on the outer surface of the electric wire during rainy weather. This is because it has been found that rainwater collects along the stepped portion, and instead of water droplets, it grows to a large extent at the bottom B of the high stepped surface, which may cause corona noise.

The present invention aims to provide an improved electric wire, as shown in FIG. 3, which is improved so as to solve the problem of the generation of corona noise and at the same time prevent the protrusion of the strands, in the electric wire proposed by the applicant. That is.

[Summary of the Invention] That is, the present invention focuses on the structure of the strands that constitute the high stepped surface, and attempts to eliminate the growth of water droplets caused by rainwater and also prevent the strands from protruding. The gist is that at least the outermost strands of the stranded wire are composed of segmented wires, and by mixing and twisting the bulky wires and small wires in the radial direction of the wire, In a low wind noise electric wire formed by forming a symmetrical pair of step surfaces in a spiral shape on the outer peripheral surface of a stranded wire, there is a gap between the segment wires constituting the high step surface, which is equal to the circumferential width of the step surface. A low wire is formed by inserting a strand of wire with at least the outer surface of the wire formed into a circular surface at approximately the center position.
It is in the AN type low wind noise electric wire.

[Example] This will be explained below based on examples.

FIG. 5 is a sectional view showing an embodiment of the low AN type low wind noise electric wire according to the present invention. By mixing and twisting the bulky strands 1 and the small bulky strands 2 in the radial direction, High step surface 10a and low step surface 1
0b is the same as in the case of FIG. 3, but in the electric wire according to the present invention, the front lines 1, 1 forming the high step surface 10a are located approximately in the center of the radial width of the high step surface 10a. A major feature is that the wire 1a is fitted into the wire 1a with a circular cross section separately from the wire 1a.

As a result, the circular cross-section strand 1a can always be positioned at the lowest point B of the wire, and the
They discovered that AN can be significantly reduced. That is, if the circular cross-section strand 1a is made to exist in this way, the high step surface 10a will form a spiral step portion having the twist pitch P according to the twist of the strand, and the high step At the lowest point B of the surface 10a, as shown in FIG. 5, the circular cross-section strand 1a is always present.

As mentioned above, the rainwater collected by the high step surface collects at this lowest point B and grows as water droplets, but in the electric wire of the present invention, the circular cross-section strand 1a is formed at this lowest point B. Because of the presence of the water droplets, water droplets are absorbed by capillary action in this circular cross-section strand 1a, and as a result, they do not grow large. Therefore, the occurrence of AN can be significantly suppressed. Although the detailed reason why the presence of the circular cross-section strand 1a suppresses the growth of water droplets is not necessarily clear, the reason is that the surface of the strand is circular and that there is no bond between the adjacent surface wire. This is thought to be because the presence of the interface causes dispersion of the surface tension of water droplets and promotion of capillarity.

Therefore, the shape of the wire to be inserted does not have to be circular all the way around; it is sufficient that at least the outer peripheral side of the wire has a circular surface (not circular in the strict sense but a curved surface), as shown in Figure 6. ), the desired effect can be expected if the strand 1b is configured as follows.

FIG. 7 shows the results of a water drop growth experiment conducted on the conventional 810 mm ² ACSR, the existing proposal (FIG. 3) with a corresponding cross-sectional area, and the electric wire according to the present invention. In both cases, after water was injected at a rate equivalent to 10 mm per hour, the water injection was stopped and the height of the water droplet above the wire surface after 1 minute had passed was determined as the water droplet radius. According to this, it can be seen that in the case of the electric wire of the present invention, the water droplet radius is significantly smaller. Naturally, the AN generated voltage increases accordingly, and the AN value also decreases.

Furthermore, in the case of the electric wire of the present invention, since the strands at the center of the strands forming the high step surface are configured to be in a fitted state, a pressing force is applied during wire drawing, and a force that causes the strands to pop out is applied. It will no longer jump out easily.

[Effects of the Invention] As described above, the electric wire according to the present invention can further reduce the AN value of the low wind noise electric wire of the step surface formation method, which can significantly reduce the AN value compared to the conventional spiral winding method. It also ensured a stable configuration of the electric wire, and is of great significance as it contributes to environmental improvement.

[Brief explanation of drawings]

Figure 1 is a partial sketch showing a conventional spiral winding low wind noise electric wire, Figure 2 is a schematic diagram showing the dimensions of the already proposed electric wire, and Figure 3 is an example of the already proposed low wind noise electric wire. 4th cross-sectional view showing
The figure is a diagram showing the low wind noise effect of the electric wire shown in Figure 3,
FIGS. 5 and 6 are cross-sectional views showing examples of the electric wire according to the present invention, and FIG. 7 is a diagram showing the measurement results of water droplets in a smooth experiment. 1: Large bulky wire, 2: Small bulky wire, 1
a: Wire with circular outer surface, 10a: High step surface, 10b: Low step surface.

[Claims]

1 A bridging piece is provided in the window hole, and a handle having a support protrusion that abuts the bridging piece on the center line in the left and right width direction is mounted in the window hole so as to be swingable in the left and right direction using the support protrusion as a fulcrum. A small switch such as a micro switch that is pushed and driven when the handle swings is arranged opposite to the back of the handle, and a coil spring is compressed between the back of the handle and the board on which the small switch is installed. The structure of the switch's operating section is characterized by: