JPS6330721B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention has a predetermined number of layers twisted around the outer periphery of stranded steel wires, and the product of the diameter _dAl of the aluminum strands and the number N of the strands in each layer is made smaller than that of conventional electric wires. This invention relates to a steel-core aluminum stranded wire (hereinafter abbreviated as ACSR) in which the twist pitch angle of the stranded wire is increased and the breaking load of the entire steel-core aluminum stranded wire is increased. [Prior art] In ACSR, which has been commonly used in the past, when the strand diameter d _st of the steel stranded wire and the strand diameter d _Al of the aluminum stranded wire layer are the same, a single strand is placed in the center, 6 on its outer circumference
It is made by tightly twisting 6 more strands of wire, such as 12, 18, 24, etc. for example
There is ACSR240 mouth ( ³⁰⁷ / _3.2 ). Also, the diameter of the steel wire
If d _st and the diameter of the aluminum stranded wire d _Al are different, the outer diameter of the steel core D _st and the diameter of the aluminum wire twisted around the outer circumference.
The maximum number of aluminum strands not exceeding π (D _st + d _Al )/d _Al was twisted between the d _Al and the next layer, 6 more strands than the previous layer were tightly twisted. It is something. For example, ACSR810/( ^45/4.8 _7/3.2 ), ACSR860 (
^54/4.5 _19/2.7 ). [Problems to be solved by the invention] These ACSRs are used to compensate for the lack of strength of the aluminum stranded wire layer with steel stranded wire, but the elongation at break of the aluminum stranded wire is far greater than that of the steel stranded wire. Therefore, when an ACSR made of a combination of these is pulled, the aluminum strand layer breaks due to insufficient elongation of the aluminum strands before the steel strands stretch and share the sufficient tension. rupture at a load much smaller than the sum of the In particular, this phenomenon becomes more pronounced as the number of twisted steel wires increases, such as 19 twists and 37 twists, and as the aluminum wire becomes an alloy wire with less elongation. This is because the twist pitch angle of conventional aluminum wire is
It is determined that this is because the elongation at break of the aluminum stranded wire layer is not sufficiently increased due to the spring effect of twisting, which is less than 0.25 radians. The above content will be explained in detail using figures and formulas. Figure 1 shows the relationship between the shape of aluminum wires a with outer diameter d _Al twisted together in the third layer, for example, and the layer core diameter D and twist pitch angle α that determine the shape. In the third layer, a similar aluminum wire a is N
It is twisted together. Here, the layer core diameter D is N
It means the diameter of the circle connecting the centers of the aluminum strands a, and the twist pitch angle α means the angle that the aluminum strands a make with the axis of the ACSR. The shape of the aluminum wire a on a plane cut at right angles to the axis of this ACSR is as shown in Figure 2, with a major axis d _Al /cosα and a minor axis d _Al
It is oval in shape. N pieces of these are arranged on the circumference of a diameter D, and the following condition must be satisfied. N·d _Al /cos α≦πD (1) Here, the equality sign holds only when there is no gap at all, and normally there is some gap between the strands, and the inequality sign holds. Conventional ACSR has N・d _Al /D of 3
Most of them have a twist pitch angle α of 0.3 or less, usually in the range of 0.17 to 0.25 radian. This twist pitch angle is too small to expect a spring effect, and a phenomenon has occurred in which the aluminum strands break before the steel strands stretch and share sufficient tension. [Means for solving the problem] In view of this, the present invention makes the product of the diameter and the number of aluminum wires in each aluminum stranded wire layer smaller than that of conventional electric wires, and increases the twist pitch angle of the aluminum stranded wires. The breaking load of the entire ACSR is increased by increasing the breaking load of the entire ACSR, that is, the result of the diameter d _Al of the aluminum wire of each stranded aluminum wire layer and the number N of the aluminum strands Nd _Al is 2.55 of the core diameter D of the aluminum stranded wire layer. ~
2.95 times, and the twist pitch angle of the aluminum wire is 0.3.
~0.5 radian. [Function] In the present invention, the product N・d _Al of the diameter d Al of the aluminum wire and _the number N thereof is expressed as the core diameter D of the aluminum stranded wire layer.
The reason why it is set to 2.55 to 2.95 times is because if it is larger than 2.95 times, the twist angle of the aluminum wire cannot be made more than 0.3 as in conventional ACSR, and the spring effect cannot be expected. If it is smaller than , the cross-sectional area of the aluminum stranded wire layer will be too small.
This is because the ACSR's breaking load decreases and its current capacity also decreases. In addition, the twist pitch angle of the aluminum wire is set to 0.3 to 0.5 radian because if it is smaller than 0.3 radian, the elongation at break of the aluminum stranded wire layer will not increase enough due to the spring effect of twisting, and if it is smaller than 0.5 radian, This is because the elongation at break of the aluminum stranded wire layer becomes too large, and the steel strands break first, reducing the breaking load of ACSR. Next, examples of the present invention will be described. Example 1 12 aluminum wires with a diameter of 3.2 mmφ were placed as an inner layer around a steel core made by twisting seven steel wires with a diameter of 3.2 mmφ.
ACSR240 ( ³⁰ ₇ /
Based on 3.2), various ACSRs were fabricated by reducing the number of aluminum wires in the inner and outer layers by 1 to 3, and varying the _NdAl /D and twist pitch angle α, and tensile tests were conducted. The results are shown in Table 1. ACSR225 (with _NdAl /D and twist pitch angle α within the claimed range of the present invention by reducing the number of wires by one from each aluminum layer)
²⁸ ₇ /3.2) No. 1 to No. 3 have two fewer aluminum wires, but the breaking load and breaking elongation are larger than the conventional example (No. 8) with a small twist pitch angle of α = 0.23 radians. ing. On the other hand, the twist pitch angle α is
No. 4 and No. 5, which are smaller than 0.3 radian, have small breaking load and breaking elongation. In addition, in Comparative Example No. 6, in which two aluminum wires were removed from each aluminum layer and the twist pitch angle α was set to 0.53 radians, the elongation at break was large, but the breaking load was reduced. No. 7, which has two wires from the inner aluminum layer and three wires from the outer aluminum layer, has a twist pitch angle of
Although it is within the range of 0.42 radians, Nd _Al /D
is 2.5, which means that the cross-sectional area of the aluminum stranded wire layer is too small and the breaking load is low.

【table】

[Table] Example 2 The steel stranded wire is 37/3.43, the aluminum stranded wire layer twisted around the outer circumference is 72/4.8, and the twist pitch angle of the aluminum stranded wire is 72/4.8.
ACSR1300 in normal stranded wire structure with 0.24 radians
Mouth ( ^72/4.8 _37/3.48 ) (18 aluminum inner layer, 24 middle layer,
ACSR was prepared by removing 1 to 5 aluminum wires from each layer of the aluminum twisted wire layer (30 wires in the outer layer, 72 wires in total) and subjected to a tensile test. Table 2 shows the twisted structure of each ACSR and the results of the tensile test. No. 1 aluminum wire was pulled out, one from the inner aluminum layer, two from the middle layer and the outer layer, and two from the inner aluminum layer.
For No. 2 and No. 3 ACSR with three aluminum wires removed from the middle layer and four aluminum wires from the outer layer, the twist pitch angle α is
It is 0.32 to 0.50 radian, which is the No.1 of conventional structure.
Even though the cross-sectional area of the aluminum stranded wire layer is smaller than that of ACSR, the breaking load is increased. On the other hand, when the twist pitch angle α is 0.55 radians,
In No. 4, the spring effect was too large, leading to a decrease in the breaking load. Also, from the aluminum inner layer, 3
Reduced books by 4 from the middle layer and 5 from the outer layer.
ACSR1090 (No. 5) has a small _NdAl /D and the cross-sectional area of the aluminum stranded wire layer is too small, resulting in a small ACSR breaking load. In addition, in No. 6, which has a relatively large cross-sectional area of the aluminum stranded wire layer because one aluminum wire is pulled out from each aluminum layer, the twist pitch angle α is 0.27 radians, and a sufficient spring effect cannot be exerted, and the Breaking load is small due to insufficient load sharing.

【table】

〔effect〕

As explained above, according to the present invention, the product of the diameter d _Al of the aluminum wire and the number N of wires to be twisted is set to 2.55 to 2.95 times the diameter D of the aluminum twisted wire layer, and the twist pitch angle of the aluminum wire is set to 0.3. With ~0.5 radian, the breaking load of the entire ACSR can be increased even if the number of aluminum wires is reduced, making it suitable for use in long span overhead power transmission lines and overhead ground wires.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the twisted shape of aluminum wire,
Figure 2 shows aluminum wire twisted at twist pitch angle α.
FIG. 3 is an explanatory diagram showing a cross-sectional shape when cut at right angles to the axis of ACSR. a... Aluminum wire, D... Layer core diameter, α... Twisting pitch angle, d _Al ... Wire diameter.

Claims (1)

[Claims] 1 In a steel-core aluminum stranded wire in which a desired number of aluminum stranded wire layers are provided around the outer periphery of the steel stranded wire, the diameter d _Al of the aluminum strands of the layer constituting each aluminum stranded wire layer and the number of wires are N. A steel-core aluminum stranded wire, characterized in that Nd _Al is 2.55 to 2.95 times the core diameter D of the aluminum stranded wire layer, and the twist pitch angle of the aluminum wire is 0.3 to 0.5 radian.