JPH0487212A - Stranded cable - Google Patents

Abstract

PURPOSE:To improve reliability of a stranded cable by making a core of a strand which is compositely formed with a resin out of hard steel wires having a ratio of sectional area within the specific range and carbon fiber having the remaining ratio of sectional area, or of a wire into which these strands are twisted together, and forming the stranded cable by twisting conducting metal wires together onto the core. CONSTITUTION:A stranded cable is formed by making a core 18 of a strand which is compositely formed with a resin out of hard steel wires 12 having a ratio of sectional area of 10 to 40% and carbon fiber 14 having the remaining ratio of sectional area, or of a wire into which these strands are twisted together, and twisting conducting metal wires 20 together onto the core 18. The core 18 is constituted in combination of the hard steel wires 12 and the carbon fiber 14 by reinforcing them with the resin, thereby even if the stranded cable suffers an arc and the resin is burnt due to the arc, tension can be borne by the hard steel wires 12 and there is no breaking of the cable. Further, by setting the ratio of sectional area of the hard steel wires 12 within the range of 10 to 40%, there are no hindrance to lightening the weight and no increase of the thermal expansion coefficient. As a result, the reliability of the stranded cable can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvements in twisted electric wires suitable for use as conductors in overhead power transmission lines.

[Conventional technology]

Conductors for overhead power transmission lines are required to be lightweight, have a low coefficient of thermal expansion, and have low sag.

Generally, this type of twisted electric wire is formed by twisting a conductive metal wire such as an aluminum wire around a central wire having high strength. Therefore, as a center wire, the inner wire has a smaller thermal expansion coefficient than the steel wire (thermal expansion coefficient 2.5 to 4xlO).
-6/'C) or lightweight carbon fiber (see Japanese Patent Publication No. 56-40922).

In addition, Japanese Patent Publication No. 1983 discloses a 'ia wire using a center line made of carbon fiber. -40922 publication,
The coefficient of thermal expansion is not directly mentioned, or the coefficient of thermal expansion of carbon fiber is equal to or lower than that of in-line electric wire, and the coefficient of carbon fiber composited with resin is less than 2xlO-6/'C, which is a minor issue. Thermal expansion coefficient or small wire is provided.

A center line using carbon fiber is generally considered to be manufactured in the following manner. That is, carbon fibers have a filament diameter of 7 to 10 μm, and each carbon fiber filament is impregnated with resin, twisted and assembled, and wrapped with a plastic tape such as polyester to obtain Jm. W,? + These strands are used as they are or are twisted together, and the resin is cured through a heat curing process to produce a center line.

The reason why carbon fibers are cured with resin in this way is that carbon fibers as they are have low mechanical strength and will easily break if subjected to bending or the like.

[Invention or problem to be solved]

In general, power transmission lines are exposed to high temperatures during use, or the operating temperature can be addressed by increasing the heat resistance of the resin, and currently it is possible to handle up to 240°C6. The insulation is destroyed by power lines or lightning strikes, etc.
The alternating current arc that occurs during the subsequent backflash from the wire to ground is usually very short-lived or generates high temperatures ranging from 1 to several thousand degrees Celsius, often melting the aluminum wire around the centerline and The fever may extend to the center line. but,
No resin can withstand such high temperatures, so the centerline will partially burn out the resin around it.

In other words, aluminum m? is attached to the center line formed by reinforcing carbon fiber with resin. : When an electric wire formed by twisting conductive metal wires is subjected to an arc, the resin that should maintain its mechanical strength even if the carbon fiber filament remains is burned out, resulting in an accident where the electric wire immediately turns into an i-wire. or occur.

Therefore, prior art wires suffer from unreliable or low reliability.

It should be noted that an electric wire formed with the inner electric wire as the center line is heavy and has a higher coefficient of expansion at high temperatures than one using carbon fiber, which increases the strength of the electric wire, which is not preferable.

SUMMARY OF THE INVENTION An object of the present invention is to avoid the above-mentioned drawbacks and provide a highly reliable stranded electric wire that does not cause wire breakage even if the resin in the carbon fibers is burnt out due to arcing.

(First Step for Solving the Problems) In order to solve the above problems, the present invention aims to solve the problems by 10 to 40%
The center line is a wire formed by compounding a hard steel wire having a cross-sectional area ratio of 1 and a carbon fiber having a cross-sectional area ratio of The twisted It! , which provides the line.

(Function) In this way, if the center wire is made of a combination of hard steel wire and carbon fiber and reinforced with resin, even if the resin is burned out due to the electric wire receiving an arc, the hard steel wire will still retain the tension. Because of this, wire breakage will not occur, and if the cross-sectional area ratio of the hard steel wire is 10 to 40%, weight reduction will not be hindered or the coefficient of thermal expansion will not increase.

〔Example〕

Embodiments of the present invention will be described in detail with reference to the drawings. FIGS. 1 to 4 show twisted electric wires 10 according to different embodiments of the present invention, and each of these twisted electric wires 10 is
The center line 18 is a wire formed by compounding a hard steel wire 12 having a cross-sectional area ratio of 0 to 40% and a carbon fiber 14 having the remaining cross-sectional area ratio using a resin 16, or a wire obtained by twisting them. , and is formed by twisting a conductive metal wire 20 on the top thereof.

In the 11th N embodiment, the center MJ, 18 has a plurality of thin hard steel wires 1 in the resin-reinforced carbon fiber 14.
2, and in the embodiment of FIG.
8 is formed by arranging a plurality of carbon fibers 14 around one hard steel wire and reinforcing it with resin. Also,
In the third [31st embodiment], the center line 18 is formed by twisting together a plurality of strands of resin-reinforced carbon fiber 14 and a plurality of hard steel wires 12.

The hard steel wire 12 may be a galvanized special steel wire. Furthermore, in the embodiment shown in FIG. 4, the center line 18 is formed by disposing a plurality of carbon fibers 14 around a plurality of assembled hard steel wires 12 and reinforcing them with resin.

Next, in order to clarify the reason why the cross-sectional area ratio of the hard steel wire 12 and the carbon fiber 14 is set to 10 to 40% of the cross-sectional area ratio of the hard steel wire 12, the cross-sectional area ratio of both the hard steel wires is set as a parameter. The relationship between linear expansion coefficient C (x 10-6/''C) and specific gravity G is listed in the table below. In the table, CF indicates carbon fiber and H3 indicates hard steel wire.

When designing a stranded wire based on Table 1 and calculating the sag-tension, the cross-sectional area ratio of the hard steel wire at the center line is 40%.
If it exceeds , the center line 11f coefficient becomes large and the specific gravity becomes large, and as will be described later, the strength reduction effect becomes lower compared to aluminum stranded wire with an in-core core. In addition, if the cross-sectional area ratio of the hard steel wire at the center line is smaller than 10%, the stranded wire will
It is impossible to provide a strength that is only about 10% of the breaking load of AC3R of m2.

Therefore, the cross-sectional area ratio of the hard steel wire composited with the carbon fiber is appropriately 10 to 40%.

FIG. 5 shows the temperature-strength characteristics of the stranded electric wire of the present invention and the stranded electric wire of the prior art. Both AC5Rs are 410m
It has a cross-sectional area of m''. In the figure, a is the sag characteristic of ACSR with the center line of the aluminized steel wire, b is the sag characteristic of ACSR with the center line of the insulated wire, and C is the sag characteristic of carbon fiber reinforced with resin. The sag characteristic of AC3R with the center line set to , d is the sag characteristic of AC5R of the present invention having the center line with the cross-sectional area ratio of the hard steel wire being 40%, and e is the sag characteristic of the AC5R having the cross-sectional area ratio of the hard steel wire being 10%. AC3 of book ff1l!+ with a center line of
It shows the relaxation 1■ characteristic of R. To calculate the slackness, set the length between a to 300
m, the maximum working tension is 5,000 kg, and the worst conditions are 15°C in the high temperature season and a wind pressure of 100 kg/m2, and -15°C in the low temperature season with a wind pressure of 50 kg/m2 and a thickness of 6 mm with a specific gravity of 0.9. It was assumed that there had been some water damage.

As can be seen from this figure, the stranded electric wire of the present invention has a preferable sag characteristic between that of the in-core core AC5R and the carbon fiber core AC3R, and has a sag characteristic of 40% of the cross-sectional area of the hard steel wire. If it exceeds the sag reduction effect of the in-core core AC3R, the cross-sectional area ratio of the hard steel wire will be at most 40.
% is required.

〔Effect of the invention〕

According to the present invention, if the center wire is made of a combination of hard steel wire and carbon fiber and reinforced with resin as shown in L, even if the wire is arced and the resin is burned out, the hard steel wire will maintain the tension. 1. Also, if the cross-sectional area ratio of hard steel wire is 10 to 40%, it will not inhibit light violetization or increase the coefficient of thermal expansion. Therefore, even if the wire is placed in a bad environment, it can maintain a certain level of strength, so the reliability of the wire will not be compromised.

[Brief explanation of the drawing]

1 to 4 are cross-sectional views of different examples of the twisted electric wire of the present invention, and FIG. 5 is a curve diagram comparing the strength characteristics of the twisted electric wire 1ii11 of the present invention and the conventional twisted electric wire. 10---Single twisted electric wire, 12---Single hard copper wire, 14
-----1 carbon fiber, 16-resin, 18---
-One center line, 20---m-conductive metal wire.

Claims (1)

[Claims] A wire formed by combining a hard steel wire with a cross-sectional area ratio of 10 to 40% and a carbon fiber having the remaining cross-sectional area ratio with resin, or a wire made by twisting them together, is the center line, and A twisted electric wire formed by twisting conductive metal wires.