JPS6355165B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to snow-resistant electrical wires such as overhead power transmission lines that prevent snow and ice from accumulating.

Overhead power transmission lines installed in areas with heavy snowfall generally accumulate snow during snowfall, and when the amount of accumulation increases beyond a certain level, the accumulated snow flows beneath the wires along the twists of the outermost strands of the wires. The snow spreads around the wires, and eventually snow accumulates around the entire outer periphery of the wires. In this way, when snow accretes on overhead power lines, the weight of the wires increases significantly, and as a result, the overhead power lines may sag significantly, causing grounding accidents, or the static load of the wires may become unbalanced over the spans of the wires. In addition to tilting of objects, vibrations caused by falling snow can cause abnormal fluctuations in wire tension, which may cause serious accidents such as wire breakage, contact, short circuits, etc. This may cause damage to above-ground structures.

Traditionally, power transmission lines have been used to prevent various accidents caused by snow accumulation as described above.
A type has been proposed in which a magnetic metal wire is wound around the outside of a stranded wire consisting of a large number of conductor wires twisted together. According to this type of snow-resistant electric wire, the magnetic flux generated around the stranded wire by the snow conveying current passes through the magnetic metal wire and causes it to generate heat due to eddy current loss. It is said that the surface temperature rises and prevents snow and ice from accreting on the wires.

However, in this case, in the prior art, it was only recognized that the magnetic metal wire should be simply wound around the outside of the electric wire, and the winding conditions and processing of the magnetic metal wire to generate heat effectively and reliably were recognized. Because deep consideration was not given to the conditions,
In reality, even if the above-mentioned technology is implemented, it is not always possible to effectively prevent the formation of ice and snow, and because of this low certainty, conventional methods have been to This necessitates the use of a magnetic metal wire, which has the disadvantage of unnecessarily increasing the weight of the wire.

This invention was made in view of the above circumstances, and aims to provide a new snow-resistant electric wire that does not increase the weight of the wire as much as possible and that efficiently promotes heat generation. be.

Embodiments of the present invention will be described in detail below with reference to the drawings.

1 and 2 show an embodiment in which the present invention is applied to a steel core aluminum stranded wire, in which a plurality of steel wires 1 are twisted together to form a steel core 2, and the steel core 2 is A stranded wire layer 4 made of a large number of aluminum wires twisted together as a conductor wire 3 is provided over multiple layers on the outside of the stranded wire layer 4. A plurality of magnetic metal wires 5 having magnetic properties are wound in an open spiral in a direction that intersects the twisting direction of the conductor wires 3 constituting the outermost layer strands, preferably in a direction perpendicular or close to perpendicular to the twisting direction. ing. Note that the magnetic metal wire 5
may be made of only a magnetic material, or may be made of a material whose surface is further coated with a highly conductive material such as aluminum.

Now, in the embodiment shown in FIGS. 1 and 2, each conductor strand 3 constituting the twisted wire layer 4 is
Magnetic flux is generated around the wire by the power transmission current, and since alternating current is normally passed through this type of wire, the magnetic flux changes. Then, the magnetic metal wire 5 outside the twisted wire layer 4
An eddy current is generated, which generates heat due to Joule heat, but the magnetic metal wire 5 has high magnetic permeability only in its axial direction, and the axial direction is the conductor element constituting the outermost layer stranded wire. The magnetic metal wire 5 is wound in a direction that intersects the twisting direction of the wire 3, in other words, in a direction parallel or nearly parallel to the direction of magnetic flux generated in each conductor strand 3.
The magnetic flux density inside becomes significantly high, and therefore the amount of heat generated becomes large. Furthermore, if a magnetic material whose surface is coated with a highly conductive material, such as aluminum-coated steel, is used as the magnetic metal wire 5,
Since a secondary current is generated in the highly conductive coating layer so as to cancel the magnetic flux, the temperature rise due to the secondary current is added, and therefore the amount of generated heat becomes even larger.

Here, as the magnetic metal wire 5 having a high electromagnetic coefficient only in its axial direction and used in carrying out this invention, a drawn wire made by cold drawing a magnetic material such as steel or alloy steel can be used. . In other words, in a drawn wire obtained by cold drawing, the magnetic properties change directionally due to plastic deformation in the drawing direction, and the alignment of the magnetic domains increases in the processing direction, that is, the axial direction of the wire, making it transparent. While the magnetic permeability increases significantly, the magnetic permeability decreases significantly in the cross-sectional direction, that is, in the direction perpendicular to the axial direction. Therefore, the magnetic wire subjected to cold drawing has a magnetic permeability in the axial direction that is much higher than that in the cross-sectional direction. For example, when the present inventors measured the magnetic permeability of an aluminum-coated steel wire with a history of wire drawing made by coating the surface of steel, which is a magnetic material, with aluminum, the maximum relative magnetic permeability in the axial direction was 3 to 4 AT/ The relative magnetic permeability in the cross-sectional direction is about 3 to 5 when measured by arranging multiple aluminum-coated steel wires in parallel so that they are in contact with each other, while the relative magnetic permeability in the cross-sectional direction is about 3 to 5. Even when the removed steel wires were lined up and measured in the same way, the maximum relative magnetic permeability was about 30 at most.

Further, although ordinary steel may be used as the magnetic metal wire, it is necessary to prevent the temperature of the wire from rising excessively in conditions other than the period of freezing and snowing, especially in the summer, beyond the original purpose of preventing freezing and snowing. To,
It is desirable to use a low Curie point material with a Curie point of about 0°C. In this way, when the temperature near the installed electric wire falls to the point where the electric wire temperature starts to form ice and snow, the magnetic metal wire 5 rapidly changes to a ferromagnetic material and increases the electric wire temperature, thereby preventing the formation of ice and snow. At the same time, it is possible to prevent the electric wire temperature from increasing excessively when there is no ice or snow.

In addition, when attaching the magnetic metal wire 5 to the electric wire, it may be formed into a spiral shape in advance and wound around the outer circumference of the electric wire, or it may be wound on the twisted wire layer 4 by twisting. good. Furthermore, in the above embodiment, the magnetic metal wire 5 is wound in an open spiral,
Of course, it may be wound in a tightly wound spiral.
Furthermore, the magnetic metal wire 5 may be one, or may be two or more. Furthermore, the shape of the magnetic metal wire 5 is not limited to the round wire shape,
Other tape-like materials may also be used.

As is clear from the above description, the snow-resistant electric wire of the present invention is used as a magnetic metal wire to generate heat through eddy current loss and increase the temperature of the wire in order to prevent ice and snow from accumulating. It has the highest current density because it uses a material with magnetic permeability and is wound on the outermost stranded wire so that its axial direction intersects the twisting direction of the conductor wires constituting the outermost stranded wire. The magnetic metal wire has an extremely high magnetic permeability in the direction of the magnetic flux generated around the outermost layer conductor wire or in a direction close to that direction. The heat generation efficiency of the wire is high and it is possible to reliably and sufficiently generate heat from the wire, and as a result, the temperature of the wire can be sufficiently increased and formation of ice and snow can be effectively prevented.

In addition, because of its excellent heat generation efficiency, the amount of magnetic metal wire used can be minimized.
Therefore, the weight of the wire will not be increased unnecessarily.

[Brief explanation of the drawing]

The drawings show an embodiment of the snow-resistant electric wire of the present invention, and FIG. 1 is a cross-sectional view thereof, and FIG. 2 is a side view thereof. In the figure, 3 represents a conductor wire, 4 represents a conductor stranded wire layer, and 5 represents a magnetic metal wire.

Claims (1)

[Claims] 1. On the outer periphery of a bare electric wire made by twisting conductor wires into multiple layers, a magnetic metal wire material having high magnetic permeability only in its own axial direction is placed in a direction that intersects the twisting direction of the conductor wires constituting the outermost stranded wire. A snow-resistant electric wire that is characterized by being wrapped around.