JPH0125450Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to the improvement of bare wire insulated power cables, and is particularly intended to provide a power cable that is used for large-capacity power transmission and has reduced alternating current resistance due to the skin effect. As the demand for electric power increases in recent years, the size of the conductors of power cables tends to increase. However, increasing the size inevitably increases the alternating current resistance due to the skin effect, so it is important to reduce the skin effect from the viewpoint of allowable current. For this purpose, strand insulated conductors have been developed and partially put into practical use, in which a copper oxide film is formed on the surface of the strands constituting the conductor to prevent current from concentrating on the surface layer of the conductor. However, when a rubber or plastic insulated power cable made of a conductor with a copper oxide film is subjected to repeated bending deformation, friction occurs between the conductor strands, and the oxide film falls off at the contact area between the wires, causing the strands made of the copper oxide film to fall off. Even if an excellent insulating effect was imparted to the material, it would be completely meaningless. The present invention allows power cables, especially CV cables, to stably maintain excellent wire insulation effects even when subjected to repeated bending. That is, the present invention has an internal conductive layer, an insulator layer,
A wire insulated power cable having an external conductive layer and a protective coating layer successively provided thereon is characterized in that an electrically insulating oil is applied to the copper oxide film surface of the conductor. In this invention, the copper oxide provided on the surface of the copper wire of the wire insulated conductor is composed of extremely porous fine grains.
Due to its excellent adsorption properties, by impregnating the copper oxide film with electrical insulating oil, the impregnated electrical insulating oil can act as a lubricant when external mechanical forces such as repeated bending are applied to the CV cable. This prevents metal-to-metal contact between the strands and prevents the oxide film from peeling off or falling off. In addition, electrical insulating oil has copper oxide film resistance (10 ⁴ ~
specific resistance (more than 10 ¹⁰ Ω-cm) compared to 10 ⁷ Ω-cm)
Since the contact resistance between the strands is large, the contact resistance between the strands increases significantly, which is extremely effective in reducing the skin effect. The electrical insulating property preferably has a viscosity of 100 centistokes or less at 100〓,
If it exceeds 100 centistokes, the fluidity deteriorates and the workability of uniformly adsorbing and impregnating oil into the gaps of the stranded insulated conductor deteriorates. Embodiments of the present invention will be described with reference to the drawings. Example 1 Segment conductor 1, which was made by twisting 88 annealed copper wires with a diameter of 2.3 mm and compression-molding them into a fan-shaped cross section, was placed in a humid ammonia atmosphere (ammonia concentration 20%) at 70°C.
After holding for a period of time, copper oxide film 2 (thickness 1μ) is applied to the surface of the copper wire.
was formed. When twisting six segment conductors together, drop silicone oil 3 (100〓viscosity 40 centistokes) to wet the space between the copper wires with the silicone oil, then spread a conductive cloth over the conductors, and The present invention includes an inner conductive layer 4, a polyethylene insulating layer 5, an outer conductive layer 6, and a protective coating layer 7 of crosslinked polyethylene.
I got a CV cable. Example 2 A segment conductor made by twisting 88 annealed copper wires with a diameter of 2.3 mm and compression molding them into a fan-shaped cross section was immersed in an 80°C oxidation treatment solution (50 g of NaoH/+100 g of NaCl ₂ /) for 5 minutes to remove the surface of the copper wire. A copper oxide film was formed on the surface. The above segment is mixed with mineral oil (viscosity at 100〓)
10 centistokes) to impregnate mineral oil between the strands. Thereafter, six segment conductors were twisted together, a conductive cloth was spread over the conductors, and an inner conductive layer, an insulator layer, an outer conductive layer, and a protective coating layer were respectively provided to obtain the CV cable of the present invention. Comparative Example 1 A comparative CV cable was obtained in the same manner as in Example 1 except that silicone oil was not used. Comparative Example 2 A comparative CV cable was obtained in the same manner as in Example 2 except that mineral oil was not used. Comparative Example 3 A conventional CV cable was obtained by providing an inner conductive layer, an insulating layer, an outer conductive layer, and a protective coating layer on the outside of a 2000 mm ² six-segmented conductor without any treatment on the surface of the annealed copper wire. After measuring the AC resistance R _AC and DC resistance R _DC of the conductors of the CV cable of the present invention, the comparative CV cable, and the conventional CV cable obtained in this way, the cables were reciprocated 3 times along a bend plate having a diameter 6 times the cable diameter. The R _AC /R _DC ratio of the conductor was measured by repeatedly bending and performing a 5-reciprocating bend test. The results are shown in Table 1.

[Table] As detailed above, the power cable of the present invention has stable characteristics without causing any damage to the copper oxide film formed on the surface of the copper strands even when subjected to repeated bending deformation, and has excellent insulation between the strands. This makes it extremely useful as a power cable, especially a CV cable.

[Brief explanation of the drawing]

The drawing is a sectional view showing an example of the inventive wire insulated power cable. 1... Conductor, 2... Copper oxide film, 3... Electric insulating oil coating, 4... Internal conductive layer, 5... Insulator layer,
6...Outer conductive layer, 7...Protective coating layer.

Claims (1)

[Claims for Utility Model Registration] (1) An insulated wire conductor with a copper oxide film formed on the surface of a copper wire, and an inner conductive layer, an insulator layer, an outer conductive layer, and a protective coating layer are sequentially provided on the outside of the wire insulated conductor. A bare wire insulated power cable characterized in that the copper oxide film surface of the conductor is coated with electrical insulating oil. (2) The wire insulated power cable according to claim 1, which is characterized in that the electric insulating oil has a viscosity of 100 centistokes or less at 100 centistokes.