JPS6031167B2 - How to install low-sag electric wires - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for constructing a low-sag electric wire.

Generally, as overhead electric wires, steel-core aluminum stranded wires are used, which are formed by providing an aluminum stranded wire layer made of hard aluminum wire on a steel core.

Since the steel core and aluminum strands of this steel core aluminum stranded wire are in close contact with each other, the coefficient of linear expansion as an electric wire is a composite value of steel and aluminum, and the sag increases due to conduction and an increase in ambient temperature. There is a problem with doing so. Conventionally, the steel tower had to be built high to absorb the increase in sag, which resulted in the problem of high tower construction costs.

An overhead electric wire that solves the above problem is a loose-core electric wire in which a gap is provided between a steel core and an aluminum stranded wire layer.

Since this electric wire has a gap between the steel core and the aluminum stranded wire layer, the value of the linear expansion coefficient of the electric wire can be the same as that of the steel core, which has the advantage of reducing the increase in sag. Not only is manufacturing complicated, but the wire is also prone to damage such as friction between the steel core and the aluminum stranded wire layer and the aluminum strands sinking during wire drawing. There was a drawback.

Another well-known method is to replace the hard aluminum wire used in steel-core aluminum Fujibori Isoko with aged aluminum wire, and then apply tension to the aluminum wire to make it permanently elongate. be. This wire uses aged aluminum wire, which has the advantage of permanent elongation with a small amount of tension.

However, since this electric wire is made of aluminum wire, it requires a special heat treatment process, which is troublesome.

Also, since the aluminum wire is hardened, there is a risk that it will be damaged during the wire drawing, and since the aluminum wire is annealed, if it is stretched, it may bend in the longitudinal direction. As the number increases, the degree of adhesion with the steel core increases accordingly, and therefore, the value of the bran expansion coefficient of the electric wire after installation cannot be made the same as that of the steel core. The present invention improves these drawbacks. This will be explained based on an embodiment shown in FIG.

In the figure, 1 indicates a steel D aluminum stranded wire, and this steel core aluminum stranded wire 1 is a normal one, that is, as shown in FIG. It is provided in close contact with 2.

Two layers of this aluminum twisted wire layer 3 are provided. Further, in this case, the length of the steel-core aluminum fuel wire 1 is set to a predetermined length depending on the distance between the steel towers. This steel/aluminum stranded wire 1 is extended between the steel towers 4 and 4' as shown in FIG. 1 by a known method.

Next, clamps 5 are attached to both ends of the stretched steel D aluminum stranded wire 1.
. Permanent elongation occurs over approximately the entire length of the The tension that causes permanent elongation in the aluminum stranded wire layer 3 is 60% or more (50% or more when a special steel core is used as the steel core) of the breaking load of the steel core aluminum strand as a whole. .

After that, while keeping the clamps 5 and 5' fixed, the tension is gradually loosened so that the steel D2 and the aluminum stranded wire layer 3 do not come into close contact with each other, as shown in FIG. The electric wire is held and installed with a tension lower than the applied tension, and the value of the linear expansion coefficient of the installed steel core aluminum stranded wire is made approximately the same as the value of the linear expansion coefficient of the steel core 2, thereby making the electric wire a low-sag electric wire.

The clamps 5, 5' constitute a retaining portion for the end of the electric wire. In this case, if tension is applied to the entire steel-core aluminum stranded wire, the steel core will also stretch, but since the tension is within the elastic limit of the steel core (8 times greater than the elastic limit of the aluminum wire), the aluminum stranded wire layer Even if tension that causes permanent elongation is applied, the steel core only undergoes elastic deformation and easily returns to its original state when the tension is released.

Therefore, after applying a tension that is within the elastic limit of the steel core and causing permanent elongation of the aluminum stranded wire layer, if the tension is loosened while the clamp remains fixed as described above, the result will be as shown in Figure 3. The aluminum strand layer 3 that has undergone permanent elongation does not come into close contact with the steel D2, and if this is held and erected with a tension lower than the applied tension, the linear expansion coefficient of the erected steel D aluminum stranded wire will be the same as that of the steel core. The coefficient of expansion is almost the same as that of the wire, resulting in a low-sag wire on the tower.

However, according to the present invention, the steel D aluminum stranded wire, which is formed by providing an aluminum stranded wire layer made of loose rock aluminum on the steel D in close contact with the key core, is extended between the steel towers, and this is used as a low-sag electric wire. Since,
There is no risk of damage during wire extension unlike in conventional loose core wires, and the wire is easier to wire than loose core wires.

In addition, with clamps fixed to both ends of the drawn steel D aluminum lacquered wire, tension is applied at room temperature within the elastic limit of the steel core and at which permanent elongation occurs in the aluminum stranded wire layer. Permanent elongation is caused in the aluminum stranded wire layer over almost its entire length, and then the tension is loosened while the clamp remains fixed to prevent the steel core and the aluminum stranded wire layer from coming into close contact with each other, and this is applied as described above. Because the construction is carried out with a tension lower than the tension applied,
When the tension is loosened, the steel 0 does not slide through the aluminum stranded wire layer and sink into the aluminum stranded wire layer, and it is possible to ensure that the two do not come into close contact with each other. Moreover, in the present invention, a hard aluminum wire is used, and since a tension that causes permanent elongation is applied to the aluminum wire at room temperature to cause permanent elongation, it is possible to bend the stretched aluminum wire in the longitudinal direction. The form is
Compared to the conventional stretched aluminum wire, the wire is more curved, so its adhesion is much lower.

Therefore, when this is installed, the influence of the aluminum stranded wire layer on the steel core is significantly reduced, and the coefficient of linear expansion of the wire as a whole is almost equal to that of the steel core, and the increase in sag is reduced. This will reduce the cost of constructing a steel tower.

In addition, since the present invention uses ordinary steel core aluminum stranded wire,
It has synergistic effects such as being extremely easy to implement.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a front view showing an example of the method for constructing a low-sag electric wire according to the present invention, Fig. 2 is a cross-sectional view showing an example of a steel/aluminum stranded wire used in the present invention, and Fig. 3 The figure is an explanatory diagram of main parts showing the state of the electric wire according to the present invention.

1... Steel core aluminum stranded wire, 2... Steel 0, 3... Aluminum stranded wire scrap, 4, 4'... Steel tower, 5, 5'...
clamp.

Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1 A steel-core aluminum stranded wire, which is made of a steel core with an aluminum stranded wire layer made of hard aluminum wire in close contact with the steel-core wire, is extended between the steel towers, and both ends of the extended steel-core aluminum stranded wire are The clamp is fixed, and then a tension is applied to the entire steel-core aluminum strand at room temperature, within the elastic limit of the steel core and causing permanent compression of the aluminum strand. Permanent elongation is caused over approximately the entire length, and then the tension is loosened with the clamp fixed so that the steel core and the aluminum stranded wire layer do not come into close contact with each other, and this is held and erected with a tension lower than the tension applied above. A method for constructing a low-sag electric wire, characterized in that the linear expansion coefficient of the installed steel-core aluminum stranded wire is made substantially the same as the linear expansion coefficient of the steel core to obtain a low-sag electric wire.