JPH0412563B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Background and Objectives of the Invention] The present invention relates to a low-noise electric wire that can effectively prevent gearlopping that tends to occur in power transmission lines.

Overhead power transmission lines have a stranded wire structure, and when wind blows on such electric wires 1 at an angle of φ or -φ from the diagonal direction as shown in Figure 1, due to the presence of strand grooves, It is well known that lift forces are generated and can cause gearlopping, which is accompanied by large-amplitude vibrations. Based on the idea that in order to prevent this gear locking, it is sufficient to eliminate the twist grooves, attempts have been made to make the entire electric wire 1 smooth, and there have been reports of cases in which PVC tape is wrapped around the outer circumference of the electric wire 1. , it was not always satisfactory. In other words, it is technically difficult and expensive to make electric wires have a smooth body, and smooth bodies also tend to generate Karman vortices, which requires countermeasures against slight wind vibrations, and the drag coefficient This is because as the wind pressure increases, problems arise such as the need to strengthen the structure of the steel tower. Therefore, there has been a strong desire for a method to prevent the gear locking by a method other than creating a smooth body.

The inventors have been involved in research for many years on low-noise electric wires that use a spiral rod wrapped around the outer circumference of the wire, and have conducted numerous wind tunnel experiments. As a result, we found that, in addition to wind noise, there were large differences in the vibration characteristics caused by the wind depending on the winding conditions of the spiral rod. In other words, the inventors have discovered that by appropriately selecting the winding direction of the spiral rod and using it appropriately, it is possible to significantly suppress the occurrence of vibration in the wire.

The present invention has been made based on the above knowledge, and an object thereof is to provide an electric wire in which the structure of the spiral rod around which the wire is wound is specified so as to significantly prevent gear locking due to wind pressure.

[Summary of the invention]

That is, the gist of the present invention is to provide a low-noise electric wire in which a spiral rod is wound around the outer periphery of the electric wire, in which the spiral rod is wound in the same direction and in the opposite direction to the twisting direction of the outermost strands of the electric wire. The behavior of the lifting force of the spiral rod that is wound around the wire is a vibration-preventing low-noise electric wire that is constructed so that the ratio of rods wound in the same direction and rods wound in the opposite direction is approximately 1:2. Its major feature is that it has a noise-preventing effect and a vibration-preventing effect at the same time by skillfully utilizing it.

〔Example〕

The following is a sequential explanation based on examples.

2 and 3 are explanatory diagrams showing two ways of winding a spiral rod around the outer circumference of an electric wire,
Figure 2 shows a state in which a spiral rod 2 is wound around the outer periphery of an electric wire 1 whose outermost circumferential twisted layer is S-twisted in the S-twist direction. The spiral rod 2' is shown being wound in the twisting direction. It is important to note that there is a large difference in the behavior of each wire when wind blows on it under these conditions.
The inventors have discovered.

The one shown in Figure 6 is a 240 mm ² ACSR whose outermost layer is made of S-twist, with nothing wrapped around it, and a spiral rod 2 with a diameter of 4 mm around its outer periphery.
This shows the results of wind tunnel experiments when the wires are wound in S or Z windings at opposing positions, and the direction of the wind is φ = 90° in Figure 1, which is the R direction in the figure, which is perpendicular to the wire. This is a plot of the relationship between wind speed and lift coefficient when the wind is blown at a higher speed.

As is clear from FIG. 6, the lift coefficient when the wind blows from the right angle is negative in all cases, and no upward lift is generated.

However, the above results are true only when the wind blows from a right angle; if the wind blows from an oblique direction, the behavior is completely different.

FIG. 7 shows the results of a wind tunnel experiment when wind was blown from the above-mentioned oblique direction, that is, from the direction of φ=30° in FIG. In the case of Figure 7, a 240 mm ² ACSR double conductor is used as the test material, and the unfilled plot marks are the results for the windward conductor, and the filled plot marks are the results for the leeward conductor. The results are shown below. The twist direction of the outermost layer is the same S twist direction as in the case of FIG. 6, and the diameter and winding position of the spiral rod are also the same.

From Figure 7, it can be seen that the following can be said.

In other words, if the wind blows from an oblique direction,
Even when the spiral rod is not wrapped, the lift coefficient is positive and an upward force is generated, but S
If a spiral rod is further wound around the twisted wire in the S-twist direction, the lift coefficient will significantly increase.

However, when a spiral rod is wound around an S-twist electric wire in the Z-twist direction, the lift coefficient becomes negative.

Furthermore, if the direction of the wind is changed to the same object and the wind is blown from the opposite direction, that is, the direction of -φ in Figure 1, a Z-wound spiral rod will be applied, although it is not shown in the figure. The lift coefficient is positive and, on the contrary, negative in the S direction.

Based on the above facts and the magnitude of the lift coefficient value under each condition, the inventors were able to stably offset the lift force on the wire regardless of whether the wind direction is in the φ direction or in the −φ direction. We focused on the possibility that there might be conditions for winding a spiral rod, and repeated various experiments.

Reading the approximate values from Fig. 7, the lift coefficient C _L ≒0.3 when the rod is wound around the S winding.
The lift coefficient C _L for only the Z-wound rod is approximately −0.15.

Now, in the case of a wind speed of 30 m/s, find the vertical load F _L that causes gear locking.
The load due to lift force is determined by the following formula.

C _L・(1/2ρ・v ²・A) where ρ: Air density v: Wind speed A: Cross-sectional area (diameter) 240mm ² ACSR's own weight is 1.11Kg/m, so the load in case of S winding is F _L Load F _L for s and Z windings
Each z is as follows. (Unit: Kg/m) F _L S = 1.11 - 0.378 = 0.732 F _L Z = 1.11 + 0.189 = 1.299 Therefore, in case of sloping wind, the average load over the entire length of the wire should be 1.11 Kg/m of the wire's own weight. If you do that,
This will allow you to maintain a stable state. In order to do this, it is understood that for a wire of length l, the ratio of the length ls of the S-wound rod portion to the length lz of the Z-wound rod portion should be ls/lz=1/2. Of course, this is not strict, and it goes without saying that it is sufficient that the windings are wound approximately at such a ratio.

The above is a case where the oblique wind direction is the φ direction in Fig. 1, but even if it is in the opposite direction -φ direction, according to each measurement result, the Z direction winding C _L ≒
0.15, C _L in the S winding direction is approximately -0.3, and it was found that under the above condition ls/lz = 1/2, the same F _L results and the load is balanced.

4 and 5 are schematic diagrams of a vibration-preventing low-noise electric wire according to the present invention in which a spiral rod is wound around the electric wire based on the knowledge based on the present invention, and FIG. The case of a conductor is shown in FIG. 5, and FIG. 5 shows the case of a double conductor. these
The ratio of ls and lz only needs to be such that the wires are wound at such a ratio over the entire length of the wire, and they do not necessarily have to be alternated at all times. However, in the case of the double conductor shown in Figure 5, if adjacent spiral rods are not wound in the same direction, lift forces will be generated in opposite directions vertically on the windward and leeward sides, resulting in a twisting force acting on the entire wire. This is an undesirable result.

〔Effect of the invention〕

As described above, the electric wire according to the present invention fully exhibits the conventional low-noise effect and can completely prevent the generation of vibrations that have been a problem and suppress gearroping, and the utility value of the low-noise electric wire is It is of great significance as it has greatly improved the quality of life.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the direction in which the wind blows on the wire, Figures 2 and 3 are explanatory diagrams showing the direction in which the spiral rod is wound, respectively, with respect to the twisting direction of the outermost layer of the wire, and Figures 4 and 5 are illustrations of the direction in which the wind blows on the wire. FIGS. 6 and 7 are schematic diagrams showing an example of the electric wire according to the invention, and are diagrams showing the results of an experiment on lifting force of the electric wire due to wind. 1, 1': Electric wire, 2, 2': Spiral rod.

Claims (1)

[Claims] 1. In a low-noise electric wire in which a spiral rod is wound around the outer circumference of an electric wire, the spiral rod is wound in the same direction and in the opposite direction to the twisting direction of the outermost stranded wire in the longitudinal direction of the electric wire. A vibration-preventing low-noise electric wire is constructed so that the ratio of rods wound in the same direction and rods wound in the opposite direction is approximately 1:2. 2. In the case of a multi-conductor power transmission line in which a plurality of electric wires are connected in parallel, the vibration according to claim 1 is obtained by winding adjacent spiral rods in the same direction. Prevention type low noise electric wire.