JP3185346B2 - Foam conductor for electric wire, electric wire using the same, and overhead transmission line - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foamed conductor for electric wires, an electric wire using the same, and an overhead transmission line, and is particularly suitable for a lightweight electric wire. An electric wire refers to a wire obtained by twisting a conductor in addition to a bare wire composed of only a conductor, and furthermore, a wire provided with an outer layer for insulation and protection on the outer periphery of the conductor.

[0002]

2. Description of the Related Art Initially, transmission lines for transporting electric power are shown in FIG.
The solid conductor 1 made of copper as shown in FIG. 1 was exclusively used, and the weight was extremely large. The weight was considerably reduced when aluminum was adopted, but it was still solid and could not be ignored. Therefore, as shown in FIG. 8A, a hollow conductor 4 in which a gap 3 is provided inside a copper or aluminum conductor 2 has been proposed for weight reduction. In particular, in the case of a 1000 kV-class UHV (ultra-high voltage transmission) electric wire that is planned in the future, this hollow conductor 4 is used and the steel wire 5 is used.
An overhead power transmission line having a steel core aluminum stranded wire (ACSR) structure in which a plurality of wires are twisted on the outer periphery of the wire has also been proposed (FIG. 8B).
Since the hollow conductor 4 has a problem in mechanical strength, it has not yet been put to practical use.

In addition, as shown in FIG. 9, for example, a so-called expanded electric wire which is light in weight by locking copper conductors (element wires) 6 to each other so as not to be deformed and which prevents corona discharge and the like is used. A so-called hollow electric wire has been invented, but it is not suitable for practical use. Further, there is also a type in which a plastic is interposed in the hollow to improve the strength.

As described above, most copper or aluminum conductors for the purpose of weight reduction have a hollow pipe or a plastic interposed in the pipe, but have a solid mechanical strength such as tension or crush. Extremely low. For this reason, as shown in FIG. 10, a structure in which a deformed material made of metal or plastic is interposed as a spacer 8 inside a pipe 7 has been proposed and has attracted attention.

However, in the conventional hollow conductor having a spacer interposed, the shape of the spacer is not only complicated but also its weight cannot be ignored in order to increase its strength. It was a fact that they could not expect as much. In addition, when a hollow conductor is used, not only accessories such as clamps become special, but also when used for overhead power transmission lines, the construction method must be special.

Therefore, as a conductor for an overhead transmission line, an aluminum conductor having a groove formed continuously in the longitudinal direction or a porous aluminum conductor is used, and a space is provided inside the conductor to reduce the weight. (Japanese Patent Laid-Open No. 2-15800)
No. 6). According to this, no special accessories are required, and a normal construction method can be applied.

[0007] Not only transmission lines, but also ordinary lines using copper or the like, for example, control cables for automobiles, etc.
Although the weight needs to be reduced, simply having a hollow space cannot maintain the required electric conductivity, and also cannot solve the problem of mechanical strength. For this reason, special copper alloys (for example, Cu-Sn based, C
(u-Ni-based alloy) is being developed, and in this regard, there is a problem common to transmission lines.

[0008]

However, the above-described wire provided with the gap has the following disadvantages. this is,
Although this is a disadvantage common to hollow conductors, holes can be formed on the surface when there is an electrical accident such as corrosion of metal during long use, snowfall, ground faults due to strong winds, etc., or when there is an electric shock. Is bright or eroded. However, in the case of the grooved aluminum conductor, the grooves are formed continuously in the longitudinal direction, and in the case of the porous aluminum conductor, there are a large number of communication holes. When this occurs, the water that has entered from there runs along the groove or the communication hole, causing water to run. Therefore, there has been a fatal defect that the conductor is deteriorated by corrosion and cannot function as an electric wire.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a practically usable foamed conductor for an electric wire capable of minimizing deterioration due to corrosion, an electric wire using the same, and an overhead transmission line. To provide.

[0010]

The foamed conductor for electric wires of the present invention has an inner layer made of a conductive foamed metal having closed cells therein. An independent bubble does not communicate with an adjacent bubble and means that it has a completely independent configuration.
In order to produce such a foamed metal, a known method can be employed. For example, a method of adding an appropriate foaming agent or blowing air bubbles can be used. The bubbles are made of a gas such as air or an inert gas, and high foaming and low foaming can be adopted depending on the purpose of use. Conductive foamed metal materials include copper and copper alloys or aluminum and aluminum alloys.

The foamed conductor for an electric wire according to the present invention is provided with an outer layer made of the same kind of conductive metal as the foamed metal on the outer periphery of the foamed metal as the inner layer in order to prevent electrolytic corrosion due to dissimilar metals. In this case, the outer layer may be constituted by a pipe, and a mechanical boundary may exist between the outer layer and the foamed metal, or the outer layer and the foamed metal may be completely integrated, and the space between them may be formed. It may be configured such that there is no mechanical boundary by metal bonding. If there is no mechanical boundary, it is possible to prevent a phenomenon that only the outer layer slips when a tensile force is applied as compared with a mechanical boundary, and to prevent water running at the boundary. Further, a core material such as a steel wire or an invar wire may be provided inside the foamed metal to further increase the strength.

Further, the electric wire of the present invention is an electric wire (strand) formed by twisting a plurality of conductors, wherein all or a part of the plurality of conductors is constituted by the above-mentioned foamed conductor for electric wire. is there.

An overhead transmission line according to the present invention is an overhead transmission line having an aluminum stranded wire structure in which aluminum wires are alternately and concentrically twisted in opposite layers, wherein the aluminum wire is formed of a wire using the above-described foamed conductor for wires. In addition, the conductive foam metal is made of aluminum or aluminum alloy. In this case, if a foam conductor for an electric wire without a core material is used, a core material is required at the center of the overhead transmission line. There is no need to provide a core material.

[0014]

When the inside of the conductor is made of a foamed conductive metal like the foamed conductor for electric wires of the present invention, high strength and light weight can be achieved while increasing the power transmission capacity. In addition, even if it is under high temperature or heat is generated due to conductor resistance, the conductor is hardly melted down due to the heat insulating effect of the bubbles, and even if there is a hole in the conductor surface, the bubbles are independent so there is no water running, Therefore, the problem of corrosion due to flooding does not occur.

Since the outer layer provided on the foamed conductor for electric wires has no irregularities on the outer surface, the pressure resistance of the conductor or the electric wire using the same can be improved. In particular, when applied to overhead power transmission lines, mechanical strength such as tension and crushing can be maintained at about the same level as solid ones, and there is no water running in the electric wires, which can be said to be fatal, as described above. It can be improved and put to practical use.

Also, when applied to electric wires for automobiles,
Since the thermal problem can be solved together with the weight reduction, there is no need to use a special copper alloy or the like.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The foamed conductor for electric wires according to the present embodiment has an inner layer of foamed metal having independent bubbles inside. Bubbles do not communicate with neighboring bubbles and have a completely independent configuration.
High and low foaming depending on the purpose of use. As the foam metal material, for example, a conductive metal such as copper and a copper alloy or aluminum and an aluminum alloy is used. In order to produce such a foamed metal, a known method can be employed. For example, an appropriate blowing agent may be added by blowing air (Japanese Patent Publication No. 57-53425), or molten copper and copper alloy. Alternatively, a method of blowing air bubbles into aluminum or an aluminum alloy (Japanese Patent Publication No. 60-49704) can be used. The bubbles are composed of a gas such as air or an inert gas.

FIGS. 3 and 4 both show a foamed conductor for electric wire having an inner layer of a conductive foamed metal 12 such as aluminum or an aluminum alloy having such closed cells 11 therein.

In FIG. 3, an outer layer 14 made of the same kind of conductive metal as the foam metal 12 is provided on the outer periphery of the foam metal 12 (FIGS. 3B and 3C). The outer layer 14 is provided to eliminate irregularities on the conductor surface, and is formed by taping an aluminum tape 15 (FIG. 3A). As a taping method, a butt winding without unevenness is preferable. In this case, a plurality of foamed conductors for electric wires may be lashed with a tape. In addition,
Instead of taping, the outer layer can be made of an aluminum pipe, in which case there may or may not be welding to close the pipe. In these cases, the foam metal 1
There will be a mechanical boundary between 2 and outer layer 14.

In FIG. 4, the foam metal 12 and the outer layer 16 are integrally joined and have no welds or seams. Therefore, there is no mechanical boundary and there is a metal bond.

FIGS. 1 and 2 show an example of an overhead transmission line using the foamed conductor for an electric wire, and particularly show a case where the present invention is applied to a UHV electric wire using aluminum or an aluminum alloy as a conductive metal material. FIG. 1 shows a galvanized steel wire 1
A, in which the foamed conductor for electric wire 18 according to the present embodiment is twisted concentrically around the stranded wire of No. 7 in the opposite direction of each layer.
It has a CSR (steel core aluminum stranded wire) structure.

FIG. 2 shows a modified example of a foamed conductor for electric wires different from the above embodiment and an overhead transmission line using the same. That is, as shown in FIG.
A foamed conductor for electric wire using a core material 20 made of a galvanized steel wire or an invar wire or the like is formed at the center, and this conductor is used for an overhead transmission line. If the foamed conductor for electric wire having the core material is used in this way, it is not necessary to adopt the ACSR structure in which the stranded wire of the steel wire is arranged at the center of the overhead transmission line. Can be arranged.

The above-described foamed conductor for electric wire having an outer layer on the foamed metal can be obtained, for example, by the following two manufacturing methods.

One, as shown in FIG. 5, is to form a continuous strip 21 of foamed metal by the method of blowing air bubbles as described above and cut it appropriately to obtain a strip 22. Is processed into a circular cross-section by subjecting it to roll forming or the like to form a foamed metal 23, and aluminum and an aluminum alloy are further applied to the outer layer to form a foamed conductor for electric wires. There are two methods of applying aluminum to the outer layer, one is a method of compounding in continuous extrusion of aluminum, and the other is a method of winding and welding an aluminum tape, drawing and heat treating. In this case, the foam conductor 24 or 25 for electric wire, in which a mechanical boundary exists between the inner layer and the outer layer, is obtained.

The other one, as shown in FIG. 6, is to add aluminum to a foaming assistant, continuously cast, heat-treat in a gas atmosphere to foam, and then immerse (dip forming) in molten aluminum. Thus, an integrated electric wire foam conductor 26 having no mechanical boundary between the inner layer and the outer layer is obtained. Note that both the heat treatment and the molten metal treatment are performed in a gas atmosphere.

In these methods, in particular, in order to make the bubbles completely independent, the type of foaming auxiliary (using a fine particle auxiliary), the method of addition, and the atmosphere are devised.

As described above, according to the foamed conductor for electric wire of the present embodiment, even if aluminum, copper or its alloy is foamed, it forms a continuous body as a conductor.
It can withstand a sufficiently large stress. This is, for example, 4φ A
Let's consider the case of 1 strand (conductor). A as outer layer
Assuming that the thickness t of the l-pipe is 0.5 mm and the electrical performance is good, the weight of 4φ solid Al (assuming ρ = 2.7 g / cm ³ ): 33.91 g / m 4φ (0.5t) Weight of pipe: 14.84 g / m 2, and assuming that the degree of foaming is 90% in this example, the weight of the foamed metal is (33.91-14.84) × 90% = 1.91
Therefore, as a total weight, 14.84 + 1.91 = 1
6.75 g / m, ie, about 1 weight for aluminum pipe
A conductor that satisfies mechanical strength and the like can be obtained only by increasing it by 3%, and a lightweight conductor can be realized.

When an electric wire is manufactured using the foamed conductor for an electric wire of the present embodiment, since the bubbles are independent, high flexibility and fatigue strength are obtained. Even if a hole or the like is formed on the surface, no problem of corrosion due to water infiltration occurs, so that high reliability can be obtained. Therefore, it can be widely applied to not only future electric wires of UHV but also other applications such as electric wires for automobiles and electric wires for robots.

[0029]

As described above, according to the present invention, the following effects can be obtained.

(1) Since the bubbles are independent, deterioration due to corrosion can be minimized, so that practically usable foamed conductors for electric wires, electric wires, and overhead transmission lines can be obtained.

(2) Since foaming forms a continuous material, it is possible to produce a foamed conductor for electric wires that can withstand sufficient stress and satisfy mechanical strength and the like. Electric wires, automobile electric wires, and lightweight electric wires can be put to practical use.

[Brief description of the drawings]

FIG. 1 is a sectional view of an overhead transmission line according to an embodiment.

FIG. 2 is a cross-sectional view of a foamed conductor for an electric wire having a core according to another embodiment and an overhead transmission line using the same.

FIG. 3 is an external view, a cross-sectional view, and a vertical cross-sectional view illustrating a foamed conductor for electric wires having a mechanical boundary according to the present embodiment.

FIGS. 4A and 4B are an external view and a cross-sectional view showing a foamed conductor for an electric wire having no mechanical boundary according to the present embodiment.

FIG. 5 is a process chart showing a method for producing a foamed conductor for electric wires having a mechanical boundary according to the present embodiment.

FIG. 6 is a process chart showing a method for manufacturing a foamed conductor for electric wires having no mechanical boundary according to another embodiment.

FIG. 7 is a sectional view showing a conventional solid conductor.

FIG. 8 is a sectional view of a conventional hollow conductor and a UHV electric wire using the same.

FIG. 9 is a cross-sectional view showing a typical structure of an expanded electric wire in a conventional hollow electric wire using copper or the like.

FIG. 10 is a cross-sectional view of a conventional hollow conductor using a deformed spacer made of metal, plastic, or the like.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 air bubble 12 foam metal 14 outer layer 15 aluminum tape 17 galvanized steel wire 18 foam conductor for electric wire

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Sato 4-10-1, Kawajiri-cho, Hitachi City, Ibaraki Prefecture Inside the Toyoura Plant of Hitachi Cable Corporation (72) Inventor Hirokazu Shiga 4-chome, Kawajiri-machi, Hitachi City, Ibaraki Prefecture No. 10 No. 1 Nippon Cable Co., Ltd. Examiner in the Toyoura Plant Junko Yoshimizu (56) References JP-A-5-145987 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01B 5 / 02 H01B 1/02 H01B 5/08

Claims (6)

(57) [Claims] 1. A foamed conductor for electric wire, comprising a foamed conductor made of a conductive foamed metal having closed cells inside, and an outer layer made of a conductive metal of the same kind as the foamed metal provided on the outer periphery of the foamed conductor. 2. The foamed conductor for an electric wire according to claim 1, wherein said outer layer comprises a wound tape or a pipe. 3. The method according to claim 1, wherein the outer layer is a conductive metal of the same kind as the foam metal.
Formed by immersion in a molten metal
The foamed conductor for an electric wire according to claim 1, wherein 4. The foamed conductor for an electric wire according to claim 1, wherein a core material such as a steel wire or an invar wire is provided inside the foamed metal. 5. An electric wire in which a plurality of conductors are twisted, wherein all or a part of the plurality of conductors is formed of the foamed conductor for electric wire according to any one of claims 1 to 4. 6. An overhead transmission line having an aluminum stranded wire structure in which aluminum wires are twisted concentrically alternately in opposite layers, wherein the aluminum wire is made of the foamed conductor for an electric wire according to any one of claims 1 to 4, An overhead power transmission line in which the conductive metal foam is made of aluminum or an aluminum alloy.