JPH056765B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a low wind pressure electric wire that can reduce wind pressure on the electric wire.

[Prior Art] A simple way to increase the current-carrying capacity of overhead power transmission lines in response to the tightening power situation is to increase the outer diameter and cross-sectional area of the wires. Wind pressure load increases.

In addition, there is a so-called compression type smooth body wire that substantially increases the effective cross-sectional area by increasing the space factor of the strands without increasing the outer diameter of the wire, but in this case, the surface It is known that wind pressure loads increase due to smoothness.

[Problems to be Solved by the Invention] As the wind pressure load on electric wires increases as described above, the steel towers that support them need to be strong enough to withstand the load. Even if an attempt is made to increase the current carrying capacity by increasing the cross-sectional area, there is a risk that the design strength of the steel tower will become unreasonable.

Therefore, the inventors investigated whether there is any way to reduce the increase in wind pressure load even if the outer diameter of the electric wire becomes larger. If this problem were solved, it would be possible to increase the current carrying capacity of overhead power transmission lines by using existing towers as they were or without making special efforts to increase the strength of towers.

The wind pressure load F _D on the electric wire is expressed by the following formula.

F _D = 1/2C _D・ρ・V ²・A ...(1) Here, C _D : Drag coefficient ρ : Air density V : Wind speed A : Projected area In equation (1) above, if drag coefficient C _D If there is a way to reduce this, even if the outer diameter of the wire becomes large, the overall wind pressure load can be reduced.

[Means for Solving the Problems] The present invention has been made in view of the above-mentioned circumstances, and its gist is to provide a spiral strand wound on the envelope of the outermost strand of an electric wire. When a spiral protrusion is unevenly distributed on one side of the outer periphery of the electric wire and extends in the longitudinal direction, the height of the protrusion is H, the central angle of the protrusion is θ, and the outer diameter of the electric wire is D. The low wind pressure electric wire is configured such that 0.15≦H/D≦0.5 5°≦θ≦120°.

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

FIG. 1 is an explanatory view showing how a spiral strand is wound around the outer periphery of the outermost layer strands 1, 1 of an electric wire 10 to form a spiral protrusion 2. As shown in FIG. Although electric wires having such a configuration have been known as low-noise electric wires, it has been found that the wind pressure can be significantly reduced by configuring the spiral strands within a specific range.

In other words, as already explained, in order to reduce the wind pressure load on the wire, the drag coefficient in equation (1)
It would be better if C _D could be made smaller, but as a result of various experiments and theoretical analyses, this drag coefficient depends on the outer diameter D of the wire, the height H of the spiral protrusion 2, and the central angle θ of the helical protrusion 2. It was found that there is a close relationship. They have also discovered that by selecting these values within appropriate ranges, the wind pressure load on the wire can be reduced.

Figure 6 shows spiral wires of various diameters being wound around the outer circumference of a 410mm ² ACSR (steel core aluminum stranded wire) so that the center angle of the wires is 30°, and the wind speed is 30m.
A wind tunnel experiment was carried out, and the outer diameter D of the electric wire was
The ratio H/D of the height H of the spiral protrusion and the drag coefficient C _D
This is a plot of the relationship between As is clear from the sixth appendix, when H/D is between 0.15 and 0.5, the drag coefficient C _D is significantly reduced.

In Fig. 7, the same 410mm ² ACSR as in Fig. 6 was used, and the central angle θ formed by the spiral protrusion was varied, and the upper limit of H/D in Fig. 6 was 0.5.
The relationship between the central angle θ and the drag coefficient C _D is plotted for the lower limit value 0.15. As is clear from the figure, when θ is between 5° and 120°,
It can be seen that the drag coefficient C _D is also significantly reduced.

It was confirmed that the above results were essentially the same even when the size of the electric wire and the diameter of the spiral wire were varied.

Therefore, the spiral protrusions formed on the outer periphery of the wire must be unevenly distributed on only one side of the wire.For example, if the spiral protrusions are wound in two opposite positions, the increase in the number of protrusions will increase the wind pressure load. becomes large, and the effect of reducing the wind pressure load on the wire is canceled.

FIGS. 4 and 5 are experimental results showing this situation. FIG. 4 shows the result of winding a spiral wire around the outer periphery of the electric wire in the S direction at the position shown in the figure, and FIG. 5 shows the result of winding it in the Z direction. In either case, it can be seen that the drag coefficient significantly increases when the winding is counter-wound.

In addition, FIG. 2 shows an example in which a plurality of spiral wires 2' are closely wound, and FIG. 3 shows a compression type electric wire 1 made by twisting segment wires 1', 1'.
This shows an example in which a spiral wire 2'' is wound around the outer circumference of the wire 0'.

[Effects of the Invention] As detailed above, according to the low wind pressure electric wire according to the present invention, the spiral protrusion having a specific configuration is formed by the spiral strands wound around the outer periphery of the electric wire, thereby significantly reducing drag. Since the coefficient can be reduced, even under conditions where the outer diameter of the wire increases and the wind pressure load increases, the wind pressure load can be kept low as a result, making it extremely economical without having to reinforce supports such as steel towers. The present invention has great significance in today's world where there is a demand for an increase in the current carrying capacity of overhead power transmission lines.

[Brief explanation of the drawing]

1 to 3 are explanatory diagrams showing examples of the low wind pressure electric wire according to the present invention, FIGS. 4 and 5 are diagrams showing the relationship between the winding position of the spiral protrusion and the drag coefficient, and FIG.
The figure is a diagram showing the relationship between H/D and drag coefficient.
The figure is a diagram showing the relationship between the center angle of a spiral protrusion and the drag coefficient. 1; bare wire, 2; spiral projection, 10; electric wire.

Claims (1)

[Scope of Claims] 1. A spiral strand wound on the envelope of the outermost strand of an electric wire forms a spiral protrusion that is unevenly distributed on one side of the outer periphery of the electric wire and extends in the longitudinal direction. The low wind pressure is constructed so that 0.15≦H/D≦0.5 5°≦θ≦120° where H is the height of the protrusion, θ is the central angle of the protrusion, and D is the outer diameter of the electric wire. Electrical wire.