JPH03176908A - Elongation restricting wire - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention increases the current carrying capacity of an overhead power transmission line, thereby increasing the temperature of the wire and causing elongation of the wire in the span of the overhead wire due to thermal expansion. The present invention relates to an improvement in a sag-reducing electric wire that can greatly suppress a decrease in the sag of the electric wire at that time.

[Prior Art] Overhead power transmission lines generally use steel-core aluminum stranded wires, which are made by twisting aluminum wires as conductive members around the outer periphery of a steel core as a tension member.

In this case, the general twisted wire configuration is that the steel core is twisted at a pitch of 20 to 40 times the layer core diameter, and the aluminum wires twisted around the outer periphery are twisted at a pitch of about 20 times the layer core diameter. It is normal to match.

For this reason, the mechanical properties of the steel core aluminum stranded wire come to exhibit properties as if they were a composite of the steel core portion and the aluminum stranded wire portion.

For example, when looking at the elastic modulus and linear expansion coefficient, which are important factors in calculating the sag of electric wires, when looking at the - example for a 410+nmz steel core aluminum stranded wire, the values shown in Table 1 are shown.

Table 1 On the other hand, the increasing trend in electricity demand in recent years is remarkable.
There is a strong need to increase current carrying capacity, but even if attempts are made to increase capacity using existing steel towers, there is a limit to the reduction in sag due to the specified ground insulation spacing, which poses a major obstacle.

In other words, if you try to increase the wire size, the sag will increase due to its own weight, and if you increase only the current carrying capacity while keeping the current size, the wire temperature will naturally increase due to energization, and the sag will increase due to linear expansion. Therefore, even if we try to increase the current carrying capacity using existing steel towers, we will be subject to inevitable restrictions.

As can be seen from Table 1, if only the steel core were to share the tension, or the sag, the coefficient of linear expansion would be reduced to about 60% of that of the steel core aluminum stranded wire. As the temperature rises, the sag decreases only a little, and the capacity can be increased accordingly for power transmission.

Figure 3 shows a loose electric wire 10 proposed for such a purpose.
4 is a sectional view of -, and FIG. 4 is a front view thereof. A small gap 3 is formed between the steel core 1 and the twisted wire layer of the aluminum wires 2, 2 in the loose electric wire 10-, and the two are connected with a clamp piece 4.4 at a predetermined interval. It is configured so that only the aluminum stranded wire 14 does not rotate and the worker does not fall due to this.

Due to the small gap formed in the loose wire 10, when the temperature reaches a predetermined temperature, the aluminum stranded wire layer no longer applies the tension (l), and only the steel core begins to share the tension, causing the temperature to rise. The accompanying linear expansion is largely suppressed, and the increase in laxity is also suppressed proportionally.

In addition to the above, the linear expansion coefficient is 1 to 2 as a sag suppression electric wire.
An invar-core aluminum stranded wire in which invar, which has xlO'/°C, which is extremely smaller than steel, is used in place of the steel core has also been proposed, and some of it has been put into practical use.

In addition, after laying steel-core aluminum stranded wires on overhead lines, the wires are held between rolls and run under pressure over the wires between the overhead wire spans, forcing only the aluminum stranded wire layer, which is easily deformed plastically, to elongate. There is also a proposal to cause tension to be shared only by the steel core, and this method has already been put into practical use.

[Problem to be solved by the invention] All of the previously proposed sag suppression wires mentioned above are theoretically valid, but when trying to put them into practical use, each has its own problems, The reality is that we are not necessarily satisfied with this.

First, regarding loose electric wires, the technique of twisting them together with a small gap is a problem, which is not preferable from the viewpoint of productivity. Moreover, the presence of small gaps tends to cause rainwater to stagnate, which may accelerate corrosion, especially on the steel core side.

In addition, those using Invar are more than 10 times more expensive than the Invar wire itself or steel wire, which not only makes the entire wire expensive, but also the fact that Invar wire is less strong than steel wire. It has some disadvantages.

Roll running method (There is also a method in which the wire is run in rolls in advance at the factory and both ends of the wire are fixed before being used as an overhead wire.)
will cause an external mechanical force to be applied to the aluminum wire,
There is a problem in that the management and control of external force to suppress the slack without damaging the wire is extremely delicate and difficult to maintain.

The purpose of the present invention is to solve the various problems of the prior art as described above, and to provide a new method for suppressing sag that can be completely suppressed by simply adjusting the pitch during stranding. The aim is to provide electric wires.

1. Means for Solving the Problem] The present invention provides a steel core aluminum stranded wire in which aluminum cable wires are twisted around the outer periphery of a steel core, by reducing the number of aluminum wires and making the twisting pitch extremely small. It is twisted at a close pitch so that it almost forms a coil.

[If the working core aluminum strands are twisted into a nearly coiled shape, they behave like a coil spring, and the tension is completely transferred to the steel core, and the aluminum wire simply follows the expansion and contraction of the steel core.] The wire only deforms, and the increase in sag as the temperature -J- rises almost follows the linear expansion of the steel core, achieving greater sag control than conventional wires. Moreover, it is easy to manufacture, there is no risk of inferior strength, and there is no risk of damaging the aluminum wire.

[Example] The present invention will be explained below with reference to examples.

FIG. 1 is an explanatory diagram showing a specific configuration of a sag suppression electric wire 10 according to the present invention.

In the case of the conventional steel-core aluminum stranded wire, for example, in the case of the above-mentioned '+10101n steel-core aluminum stranded wire, the steel core is 3.5 mm in diameter and has 7 twisted wires, and the outer circumference is 4.5+ nm thick.
12 aluminum wires in the inner layer and 18 in the outer layer, total 51
It has a two-layer structure made of 26 pieces of wood twisted together.

However, in the present invention, the steel core 1 is the same, but the aluminum wire 2 has one 4.5rnm diameter wire as an inner layer, and the same 4.5+++m diameter aluminum wire 1 is placed on top of it as an inner layer as shown in FIG. As shown in the figure, it has a structure in which aluminum wires 2°2 are twisted together at extremely dense pitches to form a coil shape. As a result, the cross-sectional area is equivalent to the cross-sectional area when the 26 aluminum wires are twisted together.

Table 2 shows the conventional 410+nm2@core aluminum stranded wire and the slack-suppressing electric wire according to the present invention, which is twisted at a dense pitch in a coil shape as shown in FIG. 1 to be equivalent to the conventional structure described above. The results are shown in comparison with No. 10.

Table 2 As shown in Table 2, the sag control wire according to the present invention has the same outer diameter and cross-sectional area, and the elastic modulus and linear expansion coefficient are equivalent to those of the llR wire shown in Table 1. Therefore, it is clear that the wire has a great effect of suppressing sag when the wire temperature rises.

However, in the J-wire arrangement of the present invention, if a round wire is used as the aluminum wire 1, there is a concern that the electrical resistance will increase.
In this case, a modified cable wire with a rectangular cross section is wound ζI
By increasing the G, it is possible to increase the space factor and lower the electrical resistance.

In addition, there is a concern that gaps may occur between the aluminum wires when the wire is stretched, but in order to deal with this, an appropriate design has been developed to prevent the band-shaped irregularly shaped wires from being wrapped around each other. Therefore, they are completely solvable problems.

Figure 2 shows a conventional example of '110mmz steel core aluminum stranded wire,
Span length 3
It is a diagram showing the result of trial calculation and measurement at 00 m.

It can be clearly seen that the slope of increase in sag of the product of the present invention is gentle and reverses that of the conventional example at 55°C. It has also been confirmed through experiments that in order to further reduce the increase in sag caused in the steel core, it is better to deviate the twist pitch of the steel core to a greater extent than in the past.

[Effects of the Invention] As described below, according to the electric wire according to the present invention, the current carrying capacity in the overhead power transmission line is increased by using the existing steel tower, thereby increasing the temperature of the electric wire, and reducing the temperature of the overhead power line due to thermal expansion. Even if the wires in the span stretch, it is possible to greatly suppress the decrease in the slack of the wires, and it is an industry that can appropriately respond to the current demands of the electric power industry. The significance is great.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an embodiment according to the present invention, Fig. 2 r;
1 is a diagram showing the relationship between temperature and sag increase for the product of the present invention and a conventional example, FIG. 3 is a sectional view of a conventional loose electric wire, and FIG. 4 is a front view thereof. 1: Steel core, 2 Ni aluminum wire, 10: Slack suppressed electric wire.

Claims (1)

[Claims] (1) In steel-core aluminum stranded wires made by twisting aluminum wires around the outer periphery of a steel core, the number of aluminum wires is reduced and the twisting pitch is extremely small to create a dense pitch that almost forms a coil. Sag control wire made by twisting together.