JPS5939843B2 - Koshin aluminum yorisen - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steel-core aluminum stranded wire used as an overhead power transmission line.

Conventional steel core aluminum stranded wire has a structure in which multiple aluminum wires are twisted directly around the outer circumference of a steel core made by twisting multiple steel wires together to form an aluminum stranded wire layer. , the tension during erection acts on both the steel core and the aluminum stranded wire layer, and as a result, the values of the equivalent elastic modulus and equivalent linear expansion coefficient of the wire as a whole are the same as those of the steel wire and aluminum wire. The value is shown as a composite twisted wire.

However, since the longitudinal elastic modulus of aluminum wire is less than 1/3 of that of steel wire, the longitudinal elastic modulus of a composite stranded wire made by twisting pixel lines is less than that of steel wire alone. The value is extremely low. Therefore, the ground deformation during the installation of electric cables will be significantly larger than the ground deformation calculated from only steel wires. Furthermore, since the linear expansion coefficient of aluminum wire is more than twice that of steel wire, the linear expansion coefficient of the composite stranded wire is considerably larger than that of steel wire alone. Therefore, the amount of change in wire ground deformation due to temperature change is considerably larger than the value calculated from only steel wires. In this way, in conventional steel-core aluminum stranded wires, although the steel core is formed by twisting steel wires together to increase the tensile strength, the earth deformation properties are lower than expected from steel wires. was also far inferior. Therefore, in the past, when installing steel-core aluminum stranded wires, the height of the erecting tower had to be increased, and the distance between adjacent wires had to be widened, making the tower larger. A huge amount of money is required for the construction of the tower and the cost of land for the tower. The inventors of the present invention have recently proposed various means to solve this problem, but the representative one is that when the wire is installed and tension is applied, the steel core and the aluminum stranded wire layer A spiral inclusion is inserted between the steel core and the aluminum stranded wire layer to create a gap between the wires, or a soft aluminum wire is inserted between the steel core and the aluminum conductor layer. In this case, voids similar to those described above are created due to plastic deformation of the soft aluminum wire during erection.
In all of these cases, the tension applied to the wire is received by the steel core, that is, the steel stranded wire, so the equivalent elastic modulus and equivalent linear expansion coefficient of the wire as a whole are almost equal to the values of the steel stranded wire. It is seen as promising as a method that can solve the above-mentioned problems to a considerable extent. However, since all of these products require other metal materials to be interposed between the steel core and the aluminum stranded wire layer, they have the disadvantage that manufacturing costs and material costs are higher than those of conventional products. The present invention provides a steel-core aluminum stranded wire with a novel structure that effectively solves the above-mentioned problem of ground deformation characteristics and does not increase manufacturing cost or material cost much compared to conventional products.

Embodiments of the present invention will be described in detail below with reference to the drawings.

1 and 2, a plurality of steel wires 1 are linearly bundled without being twisted to form a steel core 2, and a plurality of aluminum wires are formed outside the steel core 2. A plurality of aluminum twisted wire layers 4 made of twisted wires 3 are provided.

As the steel wire 1, galvanized steel wire, aluminum coated steel wire, piano wire, stainless steel wire, etc. can be used,
Further, as the aluminum wire 3, high-purity electrical aluminum, No. 1 aluminum alloy, high-strength aluminum alloy, heat-resistant aluminum alloy, corrosion-resistant aluminum alloy, etc. can be used.

Note that the steel core 2 is made up of a plurality of steel wires 1 that are bundled together without being twisted together, so if the steel wires 1 are not tightly bundled, gaps will occur between the steel wires. The outer diameter of the electric wire becomes locally large, which may make it impossible to send the electric wire smoothly during installation or the like, or the outer surface may be damaged.

In order to prevent this, it is desirable to control the back tension applied to each steel wire 1 to be equal when converging a plurality of steel wires 1. Furthermore, even if the steel core is tightly bundled, there is a risk that gaps may occur between the steel wires before being sent to the aluminum stranding device or during the aluminum stranding process.
In order to prevent this, as shown in Fig. 3, the tightly bundled steel core 2 is consolidated with adhesive or paint 5, and then an aluminum strand is placed on the outside of the consolidated steel core 2. A line layer 4 may also be provided. For the same purpose, as shown in FIG. It may also be provided above. In this case, the tape 6 may be previously formed into a spiral shape. As explained above, the steel core aluminum stranded wire of the present invention is
Since the steel core 2 is formed by converging a plurality of steel wires 3 into a straight line without being twisted together, and the aluminum stranded wire layer 4 is provided on the outside of the steel core 2, The tension applied to the wire during installation acts on the steel core 2 and hardly acts on the aluminum stranded wire layer 4, and as a result, the overall equivalent elastic modulus and equivalent linear expansion coefficient are approximately the same as those for the steel wire alone. is equal to the value of This was confirmed experimentally, but
This is considered to be due to the following reasons. Assuming that one aluminum strand 3 is twisted around the outer periphery of a steel core 2 made up of a plurality of steel strands 1, this aluminum strand 3
The expanded state is shown in Figure 5.

Here, the length of the steel strand 1 until the aluminum strand 3 goes around the steel core 2 once is L, the actual length of the aluminum strand 3 for one rotation is e, and the center of the aluminum strand 3 is Let the winding radius of the aluminum wire be r. If tension is applied to the wire and the entire wire elastically stretches by ΔL, the amount of extension of each steel wire 1 will also be ΔL since each steel wire 1 is straight.

On the other hand, assuming that the winding radius r of the aluminum wire 3 does not change, the aluminum wire 3 will elongate as shown by the imaginary line a in FIG. Here, if the virtual elongation amount of the aluminum wire is △EO, then △EO will be a smaller value than △L because the aluminum wire 3 is inclined with respect to the center line b of the steel core 2. . Since this can be easily proven geometrically, the explanation will be omitted. When the electric wire is stretched, the outer diameter of the steel wire 1 is actually reduced and the winding radius r of the aluminum wire 3 is also reduced, so the state of the aluminum wire 3 when it is stretched is as shown by the imaginary line c in Fig. 5. become.

It is clear from the figure that the actual elongation amount Δe of the aluminum wire 3 at this time is smaller than the virtual elongation amount ΔEO. Therefore, the amount of elongation Δe of the aluminum wire 3 is significantly smaller than the amount of elongation ΔL of the steel wire 1. Furthermore, the actual length e of the aluminum wire 3
is larger than the actual length L of the steel wire 1, and therefore the elongation amount ε2 per unit length of the aluminum wire 3 is significantly greater than the elongation amount ε1 per unit length of the steel wire 1. becomes smaller.

When the pixel line is extended by ε1 and ε2 in this way, the stress ρ2 acting on the aluminum wire 3 and the stress ρ1 acting on the steel wire 1 are given by the following equations. Here, K1 indicates the longitudinal elastic modulus of the steel wire 1, and K2 indicates the longitudinal elastic modulus of the aluminum wire 3. ρ1-Kl8l ρ2=K262 K2 is significantly smaller than K1, and ε2 is as described above. Since ρ2 is significantly smaller than ε1, ρ2 is significantly smaller than ρ.

As described above, the stress that the aluminum wire 3 receives is significantly smaller than the stress that the steel wire receives. In other words, it is clear that the tension applied to each aluminum wire 3 is significantly smaller than the tension applied to each steel wire 1. Furthermore, it is clear that the tension applied to each aluminum wire in the second and higher aluminum stranded wire layers becomes even smaller. Therefore, considering the electric wire as a whole, most of the tension applied to the electric wire is considered to act on each steel strand 1 of the steel core 2. Note that since each steel wire 1 is straight, tension acts equally on each steel wire 1. The above consideration was based on the assumption that the aluminum wire 3 is in close contact with the steel core 2 and that the winding curve of the aluminum wire 3 is a correct helical curve, but in reality, the aluminum wire 3 does not draw a perfect helical curve, and the aluminum wire 3 often partially lifts from the steel core 2.

Considering these factors, when tension is applied to the wire, deformation occurs in the shearing direction before the aluminum wire 3 stretches, and the elongation of the wire is absorbed to some extent, so the tension applied to the aluminum wire 3 becomes even smaller. In this extreme case, the aluminum wire itself may not elongate at all, but only deforms in the shearing direction, and no tension is applied to the aluminum wire at all. On the other hand, since the steel wires 1 are not twisted together, it is considered that there is almost no deformation in the shear direction. On the other hand, if the outer diameter of the steel core 2 is extremely reduced when the wire is stretched, a space is created between the steel core 2 and the aluminum stranded wire layer 4, and tension acts on the aluminum wire 3. It is possible that they may not.

If we consider the conventional steel core aluminum stranded wire, in the conventional one, the steel wires are twisted together, so the tension applied to the steel wires other than the central core wire is the same as that of the steel core of the present invention. Similar to what was explained about the aluminum wire of the aluminum strand, it is significantly smaller than the central core wire.

Therefore, the tension applied to the outer aluminum stranded wire layer increases accordingly. As explained above, in the steel core aluminum stranded wire of the present invention, the aluminum stranded wire layer hardly receives the tension when the wire is installed, and therefore the equivalent elastic modulus and equivalent linear expansion coefficient of the entire wire are the same as those of the steel wire. Almost equal.

Therefore, when the steel-core aluminum stranded wire of the present invention is installed, it not only has a small sag, but also has little sag change due to temperature changes or load changes due to ice and snow accumulation, making it easy to install steel towers. It can be made smaller, which has the advantage of significantly reducing tower construction costs and tower land costs compared to conventional methods. Since there is no need for this, there is also the advantage that the manufacturing cost and material cost of the electric wire itself are low.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway side view showing a steel-core aluminum stranded wire according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line -- in FIG. FIG. 4 is a cross-sectional view showing an example of the steel core used, FIG. 4 is a side view showing another example of the steel core, and FIG. 5 is a schematic diagram for explaining the action of the steel-core aluminum stranded wire of the present invention. be. 1... Steel wire, 2... Steel core, 3...
... Aluminum wire, 4 ... Aluminum twisted wire layer.

Claims (1)

[Claims] 1 A steel core is formed by converging a plurality of steel wires into a straight line without being twisted together, and an aluminum stranded wire layer made by twisting a plurality of aluminum wires is provided on the outside of the steel core. Steel-core aluminum stranded wire.