JP2001043740A - Overhead transmission line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an overhead transmission line that can effectively realize suppression of looseness, has no difficulty regarding manufacturing of electric wire, does not break the twisting state of a strand during a stringing work or the like, and is moreover inexpensive. SOLUTION: Six aluminum strands 12, for example, formed by concentrically twisting aluminum wires 3 around central steel strands (tension member strands) 2 are twisted with twisting factor not less than 0.7% to constitute this overhead transmission line 11. Thus, the equivalent effect that secures sufficient excess length for the aluminum wires 3 is provided, the steel strands 2 carry almost all the tension, the aluminum wires 3 are hardly acted by the tension. Therefore, a stringing design can be achieved using elastic coefficient and linear expansion coefficient of the steel strands, and looseness can be greatly suppressed comparing with a conventional steel core aluminum strand formed by concentrically simply twisting an aluminum wire around steel strands.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overhead power transmission line such as a steel core aluminum stranded wire (ACSR), and more particularly to an overhead power transmission line in which sag is suppressed.

[0002]

2. Description of the Related Art As shown in FIG. 8, a galvanized steel wire 2 in which a plurality of galvanized steel wires 1 are twisted is disposed at the center as a tension member, and an aluminum wire (aluminum wire) serving as a conductive path is provided on the outer periphery thereof. An overhead power transmission line 5 composed of a steel core aluminum stranded wire (ACSR), which is a composite stranded wire formed by concentrically twisting element wires 3 by concentric twisting to form a concentric aluminum stranded layer (the aluminum stranded wire is indicated by 4), Since they are lightweight and can easily achieve high tension, they are generally widely used as overhead power transmission lines.

[0003] In a general overhead transmission line 5 shown in Fig. 8, an aluminum wire 3 and a galvanized steel wire 1 having characteristics as shown in Table 1 are used in accordance with the wire diameter, and the galvanized steel wire 1 is used as a twisting rate. Is about 0.5% (the center line is 0%), and the aluminum wire 3 is 1.4% to 2.7% depending on the concentric twisted layer position.
% Is adopted, and the ACSR is configured by twisting with concentric twist. At the same time, twisting
A galvanized steel wire layer (one layer in the illustrated example) and an aluminum wire layer (two layers in the illustrated example) on the outer periphery from the center line of the galvanized steel stranded wire 2 are alternately twisted in different twisting directions for each layer. . In the case of an ACSR composed of one galvanized steel strand and six aluminum strands twisted around its periphery, the twisting ratio of each of the galvanized steel strand and the aluminum strand is 0% and 1.4% are commonly employed.

[Table 1]

[0004] The above-mentioned twisting rate is a ratio to be added to the length of the center axis of the stranded wire when calculating the actual length of each strand in the stranded wire. expressed. K = (x−L) / L = (√ (P ² + π ² D ′ ² ) −P) / P = √ (1 + π ² · (D ′ / P) ² ) −1, where L is the center axis of the stranded wire. Length x: Length of strand forming stranded wire D ': Pitch Diameter (layer core diameter) D: Outer diameter of stranded wire P: Pitch of stranded wire

[0005] When the overhead transmission line 5 made of ACSR is wired, the sag characteristic is calculated by the following equation in which the cross-sectional area is added to the respective elastic coefficients and linear expansion coefficients of the aluminum wire 3 and the galvanized steel wire 1. It is designed using the equivalent elastic modulus E and the equivalent linear expansion coefficient α. E = (Ea × Aa + Es × As) / (Aa + As) α = (αa × Ea × Aa + αs × Es × As) / (Ea
× Aa + Es × As) where E: Equivalent elastic modulus of ACSR A: Equivalent linear expansion coefficient of ACSR Ea: Elastic modulus of aluminum wire Es: Elastic modulus of galvanized steel wire Aa: Total cross-sectional area of ACSR aluminum wire As: ASR: Total cross-sectional area of galvanized steel wire αa: Coefficient of linear expansion of aluminum wire αs: Coefficient of linear expansion of galvanized steel wire This type of overhead transmission line 5 has a “load-elongation characteristic” as shown in FIG. As shown in the figure, the wire has a characteristic of an equivalent elastic modulus in the temperature range at the time of the overhead wire. In the sag design using the equivalent elastic modulus and the equivalent linear expansion coefficient, ACS
The “sag-temperature characteristic” of R is indicated by a broken line (ACSR41) in FIG.
0 mm ² ), and the sag increases in proportion to the wire temperature.

In the overhead power transmission line 5 made of the above-mentioned ACSR, when the overhead transmission line 5 is installed, the tension of the electric wire is set to a galvanized steel stranded wire (hereinafter simply referred to as a steel stranded wire) 2 and an aluminum stranded wire 4 on its outer periphery.
As described above, the equivalent elastic modulus and equivalent linear expansion coefficient of the entire wire show the value as a composite stranded wire of both, as described above, so that not only the sag during installation is large, but also Fluctuations in the sag resulting from changes in load and temperature due to wind pressure and the like also increase. For this reason, it is necessary to increase the distance between phases or lines, and there is a problem that the entire transmission line including the tower becomes large.

[0007] The cause of the increase in the sag as described above is that tension acts on both the steel stranded wire 2 and the aluminum stranded wire 4 on the outer periphery thereof. It is conceivable to adopt a structure in which most of the components act on the steel stranded wire 2 and do not act on the aluminum stranded wire 4. As a sag suppressing type overhead transmission line based on this idea, for example,
A so-called loose-type overhead transmission line has been developed in which an aluminum stranded wire layer is loosely covered over the entire length of a steel stranded wire and mechanically separated from each other as disclosed in Japanese Patent No. 21683.

Further, a sag-suppression type overhead transmission line using an invar wire having a significantly smaller linear expansion coefficient in place of the galvanized steel wire 1 as a tension member is also known.

[0009]

In the above-mentioned so-called loose type overhead power transmission line, it is not easy to loosely twist an aluminum wire around the outer periphery of a steel stranded wire at the center, and there is a great difficulty in manufacturing technology. is there. Further, an overhead transmission line using an invar wire as a tension member has a disadvantage that the cost of the product is extremely high because the invar wire is expensive.

By the way, in the ACSR type overhead transmission line having the structure shown in FIG. 8, as a method of applying most of the wire tension to only the steel stranded wire 2, it is conceivable to increase the twisting rate of the aluminum stranded wire 4 sufficiently. . That is, if the twist rate of the aluminum stranded wire 4 is sufficiently larger than the twist rate of the steel stranded wire 2, the actual length of the aluminum wire 3 is sufficiently longer than the actual length of the steel wire 1, and the Since the elongation rate (elongation strain) of the wire 3 is sufficiently smaller than the elongation rate (elongation strain) of the steel wire 1, as described above, by sufficiently increasing the twist rate of the aluminum stranded wire 4, the wire tension can be reduced. The steel strand 2 can be almost received.

However, as shown in FIG. 8, the aluminum wire 3 is concentrically twisted around the outer periphery of the steel wire 2 so that the aluminum wire 4
When the twist rate is increased to such an extent that the tension hardly acts on the aluminum wire 3, there is a problem that it is difficult to maintain a stable twist state as the twisted wire. If the twist rate is too large,
For example, a pressing force generated when the overhead power transmission line 5 is passed through the metal wagon in the overhead wire construction causes a problem such that the twisted state of the aluminum stranded wire 4 is broken (for example, laughter occurs).

The present invention has been made in view of the above circumstances, and it is possible to suppress the sag and realize no difficulty in the electric wire manufacturing technology, and the twisted state of the aluminum stranded wire is broken at the time of overhead wire construction or the like. An object of the present invention is to provide an overhead transmission line that does not cause any problem and can be manufactured at low cost.

[0013]

The overhead transmission line according to the present invention for solving the above-mentioned problems comprises a plurality of aluminum stranded wires formed by concentrically twisting aluminum wires around a center tension member stranded wire. It is characterized by being twisted at a twist rate of 0.7% or more.

[0014]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described with reference to FIGS. FIG. 1 is a cross-sectional view of an overhead transmission line 11 made of a steel core aluminum stranded wire according to an embodiment of the present invention. For example, a galvanized steel stranded wire 2 obtained by twisting seven galvanized steel wires 1 is used as a tension member. This galvanized steel stranded wire (hereinafter simply abbreviated as steel stranded wire) 2
, For example, six aluminum stranded wires 12 formed by concentrically twisting aluminum wires (aluminum wires) 3 such as seven hard aluminum wires, etc., at a twist rate of 0.7% or more. It is a combined structure.

In general, in the design of overhead power transmission lines, the following various types of elongation of the electric wires are considered. That is, elastic elongation 0.3% to 0.5% (tension elongation corresponding to the maximum working tension of the electric wire) Initial elongation 0.01% (twist tightening elongation) Creep elongation 0.01% Rotational elongation 0.02% (electric wire elongation) Elongation due to rotation of electric wire during wire) Elongation by wheel drive 0.1% (Elongation due to the passage of wire wheel when wire is extended) Corrected elongation of linear expansion coefficient when temperature falls from temperature during overhead wire to low temperature 0.3 % The sum S of the various elongations above is S = 0.47% ~
0.67%.

On the other hand, as a special distribution line instead of an overhead transmission line, there is a distribution line obtained by coating a wire having a structure substantially similar to that shown in FIG. 1 (however, three to four aluminum stranded wires). In this type of distribution line, the aluminum stranded wire is 0.3% to 0.1%.
It is normal to twist around the galvanized steel stranded wire at a twist rate of 5%. For a distribution line having such a normal twisting rate, a normal equivalent elastic modulus and an equivalent linear expansion coefficient are applied. Therefore, the normal twisting rate of such a distribution line is 0.3% to 0.3%. Twisting at a twist rate of 0.5% plus the sum S of the various elongations described above of 0.47% to 0.67%, that is, a twist rate of 0.77% to 1.17%, An effect equivalent to securing the total length S of the various elongations described above is obtained for the aluminum wire 3, and the galvanized steel stranded wire 2 shares most of the tension.
However, even if the twisting ratio is set to be larger than 1.17%, the remaining length of the aluminum wire 3 is equivalent to further increase, and the sharing of the galvanized steel stranded wire 2 is further increased. Therefore, in the present invention, as described above, the twist rate of the aluminum stranded wire is set to 0.77% or more.

As described above, since the galvanized steel stranded wire 2 shares most of the tension, the elastic modulus and linear expansion coefficient of the galvanized steel stranded wire can be applied to the overhead wire design, and therefore, the conventional structure of the ACSR The sag can be greatly suppressed as compared with.

FIG. 3 shows a specific sag characteristic of the overhead transmission line 11 composed of the above-mentioned ACSR (solid line ACSR404m).
m ² ). The ACSR 404 mm ² is a wire (HAl7 / 3.5) of the embodiment of the present invention having the structure shown in FIG.
mm × 6 pcs + St7 / 3.5 mm), and all the load conditions and the like are shown by the broken line in FIG.
0mm ² (HA26 / 4.5mm + St7 / 3.5m
m). ACSR410m of conventional structure
sag to can be reduced by 30% to 40% as compared to m ^2. The twist of the aluminum stranded wire 3 itself may be a normal twist rate (for example, 1.4% or the like).

The tension member stranded wire of the overhead transmission line according to the present invention is not limited to the galvanized steel stranded wire 2 of the embodiment, but may be a reinforced aluminum covered steel stranded wire, an ultra-extra strong galvanized steel stranded wire,
Aluminum coated steel stranded wire and special aluminum coated steel stranded wire can be used. As the aluminum wire (aluminum wire) 3, a soft aluminum wire, instead of the hard aluminum wire of the embodiment,
Heat-resistant aluminum alloy wires and the like can be used in the same manner.

The overhead transmission line 11 composed of the above-mentioned ACSR
In FIG. 4, six aluminum stranded wires 12 are twisted around the steel stranded wire 2, and the number of the aluminum stranded wires 12 is 4 as shown in FIG.
It is also possible to use five books or five books as shown in FIG. 5, and there is no particular limitation. Also, galvanized steel stranded wire 2
The twisted wire configuration of the aluminum twisted wire 12 can be applied to 19 twists in addition to the 7 twists of the embodiment. In the embodiment,
Although the case where the aluminum wire (aluminum wire) is a round wire is shown, reducing the outer diameter of the wire by using a molded aluminum wire is effective in reducing the wind pressure load.

As the tension member twisted wire, FIG.
As shown in the figure, an aluminum-covered circular steel wire 22 centered on an aluminum-covered fan-shaped steel wire 21 in which a sector-shaped steel wire 21a is covered with aluminum 21b.
7, a tension member stranded wire 2 'having a structure twisted around the outer periphery of the aluminum-coated circular steel wire 20 having a circular steel wire 23a as shown in FIG.
The use of a tension member twisted wire 2 "having a structure twisted around the outer periphery of the wire is effective in reducing the outer diameter. In addition, as a tension member twisted wire, a galvanized invar twisted wire and an aluminum-covered invar twisted wire are used. In this case, the maximum degree of sag can be suppressed because of the low coefficient of linear expansion.Invar is made of Fe (iron) and Ni (nickel) whose linear expansion coefficient is 1/3 of steel. ) 36% alloy.

[0022]

According to the overhead transmission line of the present invention, a twist ratio of 0.7% or more of a plurality of aluminum twisted wires formed by concentrically twisting aluminum wires around a central tension member twisted wire. Most of the tension acting on the electric wire can be shared by the tension member twisted wires, and thus the overhead wire design is performed by the elastic coefficient and the linear expansion coefficient of the tension member twisted wires such as galvanized steel wires. This makes it possible to greatly reduce the sag compared to a conventional steel core aluminum stranded wire in which an aluminum wire is simply twisted concentrically around a steel stranded wire.

[Brief description of the drawings]

FIG. 1 is a steel core aluminum stranded wire (ACS) according to an embodiment of the present invention.
It is a cross section of an overhead transmission line consisting of R).

FIG. 2 is a load-elongation characteristic diagram of the steel core aluminum stranded wire of FIG.

FIG. 3 is a diagram showing the sag characteristics of the present invention and a conventional steel core aluminum stranded wire, wherein a solid line is an overhead transmission line made of the steel core aluminum stranded wire of the present invention, and a broken line is a conventional steel core aluminum stranded wire. is there.

FIG. 4 is a cross-sectional view of an overhead transmission line made of a steel core aluminum stranded wire according to another embodiment of the present invention, in which the number of aluminum stranded wires is four.
It is a book.

FIG. 5 is a cross-sectional view of an overhead transmission line made of a steel core aluminum stranded wire according to still another embodiment of the present invention, in which the number of aluminum stranded wires is five.

FIG. 6 is a cross-sectional view showing another embodiment of the tension member twisted wire in the overhead transmission line of the present invention.

FIG. 7 is a transverse sectional view showing still another embodiment of the tension member twisted wire in the overhead transmission line of the present invention.

FIG. 8 is a cross-sectional view of a conventional steel core aluminum stranded wire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Galvanized steel wire 2 Galvanized steel twisted wire (tension member twisted wire) 2 'Aluminum covered fan-shaped steel twisted wire (tension member twisted wire) 2 "Aluminum covered molded steel twisted wire (tension member twisted wire) 3 Aluminum wire 11 Fictitious Transmission line 12 Aluminum stranded wire

Claims (1)

[Claims] 1. Around the center tension member stranded wire,
An overhead power transmission line characterized in that a plurality of aluminum wires, which are obtained by twisting aluminum wires by concentric twisting, are twisted at a twist rate of 0.7% or more.