JP2561839B2 - Low AC resistance conductor - Google Patents

Description

The present invention relates to a low AC resistance conductor.

(Prior art and its problems) In a conductor that carries an alternating current, when the cross-sectional area of the conductor increases, the current density increases as the surface effect of the conductor increases from the center to the surface of the conductor, that is, the current flows near the conductor surface. As a result, the AC resistance, which is the effective energization resistance, increases. For this reason, the power transmission loss is inevitably large in a power cable for power transmission or the like in which the current to be passed is large and the cross-sectional area of the conductor must be large.

Therefore, in order to eliminate this defect, in a power cable, as shown in FIG. 1 (a), a plurality of conductors 1 are bundled in a circle, or as shown in FIG. 1 (b), the strands 1 are bundled. There is often adopted a means of shaping a fan into a fan shape and then further combining them into a circular shape to form the wires 1 at the same time, and using an insulated wire as the wire 1 to make the shared current of each wire uniform. .

However, even if the strands are insulated, the self and mutual inductances of individual strands generated when energized differ depending on the proximity effect due to other neighboring strands, and the impedance that determines the current sharing of each strand is The closer the strand is, the smaller it is. For this reason, the current sharing cannot be made uniform, and the effect is greater for superconducting wires that reduce the resistance component of the impedance that determines the current sharing for each strand, and the AC resistance is that of a conductor whose strands are not insulated. There is not much difference. Therefore, as it is, the benefits of superconducting technology cannot be fully obtained.

(Object of the Invention) The present invention, after the conductor described with reference to FIG. 1 (b), that is, a plurality of insulated wires are bundled into a fan shape and shaped,
By effectively utilizing the conductor structure formed by combining these multiple cylinders in a circular shape, we provide a low AC resistance conductor with a uniform current sharing of each element wire. This is a cable that can be realized.

(Means for Solving the Problems of the Present Invention) The so-called segment conductor described above with reference to FIG. 1 (b) has a straight central wire 1a as shown in FIG. 2 (a). The strand layers 1b, 1c, etc. are twisted in a spiral shape in the required number of layers and shaped into a fan shape as shown in Fig. 2 (b).
To form. Next, this is assembled into a circular shape as shown in FIG. 1 (b), and then insulating paper or the like is wound on it to form a bundle. That is, in the present invention, the fan-shaped segment 3 is formed by spirally twisting a plurality of insulated wires around the central wire in a required number of layers and shaping them into a fan shape, which facilitates handling. An example in which the insulating paper 2 is wound in order to do so is shown.

In this layered structure of the fan-shaped segment wires of the conventional example, the center wire 1a is at the center of the fan-shaped segment 3, that is, from the circumference line passing through the center wire 1a to the surface as shown in FIG. 2 (b). The number of strand layers N ₁ located in between is the same as the number of strand layers N ₂ located between the circumferential line and the inner surface, and the position of the inner surface of the fan-shaped segment is 0%, and the surface position is When it is set to 200%, it is common to shape the central wire 1a so that it is located at the 100% point.

However, as a result of research, the present inventor has clarified that even in the layered structure of the fan-shaped segment of this conventional example, there is a cause of non-uniformity in the shared current of each strand.
That is, the generated magnetic field B based on the circulating current I as shown in FIG.
The distribution of the electromotive force generated in the cross section of the fan-shaped segment is indicated by a downward convex line E, and the average value of its superpower is point M.
It was clarified that it is located in.

This is because the distribution of electromotive force is large on the surface side of the spirally twisted conductor, small on the inner surface side, and has a convex shape downward, so the average value of the electromotive force of the entire conductor is It will be on the front side of the position. That is, since the magnitude of the current flowing in each strand is proportional to the electromotive force averaged in the length direction, a larger current flows around the central strand 1a of each fan-shaped segment, and a larger current flows to the strand layers. This causes non-uniform current flow. Therefore, as described above, when the central wire 1a is shaped so as to be located at the point of 100% as shown in FIG. 2 (b), non-uniformity occurs between the shared currents of the respective wires, resulting in an effective There is a problem that the AC resistance, which is the energization resistance, increases.

The present invention, the position of the center strand 1a of each fan-shaped segment,
Since the number of strand layers on the inner surface side and the front surface side of the central strand 1a is not the same, it is arranged near the mean value point M of the electromotive force distribution existing on the surface side from the center position of the fan-shaped segment. Is. As a result, the electromotive force averaged in the length direction of each insulated wire is made uniform, and the magnitude of the current flowing through each wire can be averaged.

That is, since the distribution of the electromotive force of each fan-shaped segment is a downwardly convex distribution, the average value of the electromotive force is at a point closer to the surface than the position of 100%. Therefore, if the central strand 1a of the fan-shaped segment of the layered structure is located at the point of this average value, the electromotive force averaged in the length direction of each insulated strand belonging to each layer from the inner surface to the surface is the center. It becomes close to the electromotive force of the strand 1a, and the difference in the average longitudinal electromotive force of the strands belonging to different layers becomes small. Since the magnitude of the current flowing in each strand is proportional to the average electromotive force in the length direction, the difference in the magnitude of the current flowing in the strands belonging to each layer becomes small, and the sharing of the shared current of each strand is achieved. it can.

 Next, examples of the present invention will be described.

(Example) FIG. 5 shows that each fan-shaped segment has an insulated diameter of 0.
It is composed by twisting 16 layers of 8mmφ strands, and the overall structure is 90mmφ in outer diameter, 40mmφ in inner diameter, and conductor cross section area 4000mm.
It is configured as a ^2- segment 8-segment conductor. The layer structure of the wire 1 of each fan-shaped segment is shown in a cross-sectional view of the wire 1 of the wire layer in the central portion of the fan-shaped segment, as shown in the partial cross-sectional view shown in the upper segment as a representative example. The strand layers from to the outer peripheral portion of the fan-shaped segment are shown in a schematic diagram of a fan-shaped frame and are shown to have a plurality of layers. Then, as shown by the fan-shaped frame, each strand layer is twisted in a spiral and layered manner around the central strand 1a sequentially, and the strands between the strands are denser on the surface side than the central strand 1a. The inner surface side of the central strand 1a is configured by roughening the strand layers. By constructing the strand layer of each fan-shaped segment in this way, the conductor structure in which the position of the central strand 1a is located at a point of 130% in the example shown in FIG.

As a means for constructing this layer structure, an insulating material such as oil-impregnated paper or plastic is interposed between the strands on the inner surface side of the central strand 1a to form an interlayer gap, and the surface side of the central strand 1a is twisted. At the time of joining, pressure is applied from the outside so that the wire-wire layers are adhered to each other.

FIG. 4 shows the position of the center wire 1a as shown in FIG.
It is a characteristic diagram of the current density showing the result of calculating the magnitude of the current flowing through each layer by changing it from 122.5% (a) to 135% (f). The inner 16 indicates the current density of the central wire 1a. In the figure, the numbers are smaller from the wire layer (inner layer) closer to the central wire 1a toward the wire layer (outer side) farther away, and the outermost wire layer shows a current density of 1. Thus, the closer the position of the central wire is to 100% (see FIG. 4 (a)), the higher the current density of the wire in the outer wire layer becomes, and the current density of the wire is 132.5% (see FIG. 4 (e)). ), The current densities of the wires of each layer are almost equalized. From this, it is understood that the effect of equalizing the shared current according to the present invention is high.

Further, by applying the present invention, by utilizing the high conductivity obtained when ordinary copper or aluminum is cooled to about -196 ° C. with liquid nitrogen, a conductor cross-sectional area through which a large current flows
In the case of a wire-insulated segmented conductor of about 4000 mm ² , the AC resistance can be reduced to about 1/3 that of the conventional case. Further, when a conductor is formed by bundling superconducting wires, further effects can be expected.

(Effect of the Invention) In a segment conductor in which segments formed by shaping an insulated wire into a fan shape are combined in a circle, by arranging the position of the center wire on the surface side from the center position of the fan-shaped segment, each wire It is possible to make the magnitude of the current flowing through the electrodes uniform and to make the alternating current resistance much smaller than in the case of simply bundling the insulating wires. Therefore, according to the present invention, it is possible to realize a high-current conductor such as a normal conductor or a superconducting power cable with less loss.

[Brief description of drawings]

1 and 2 are cross-sectional views of a conventional conductor and an explanatory view of a method for forming the same, FIG. 3 is an explanatory view of an electromotive force distribution, and FIG. 4 is a view of each strand layer depending on a position of a central strand in the present invention. FIG. 5 is a partial cross-sectional view of a conductor according to an embodiment of the present invention. 1 ... strand, 1a ... central strand, 1b, 1c ... strand layer, 2 ...
… Insulating paper, 3… Fan-shaped segment.

Claims (1)

(57) [Claims] 1. A fan-shaped segment is formed by spirally twisting a plurality of insulated wires around the central wire in a required number of layers to form a fan-shaped segment, and a plurality of the fan-shaped segments are united to form a circular shape. To form a segment conductor, the center strand position of each fan-shaped segment, while the number of strand layers on the surface side and the inner face side of the center strand is the same, between the layers of the strand layer on the surface side. A low AC resistance conductor configured so as to be dense and to roughen the interlayer of the wire layer on the inner surface side so as to be located near the mean value point of the electromotive force distribution on the surface side from the center position of the fan-shaped segment.