JPS6057165B2 - cable conductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in large-sized conductors used in power cables, and in particular to improvements in split compression shaped stranded conductors.

In recent years, with the increase in power transmission capacity, the size of the conductor of power cables has increased, and cables with a diameter of 5,000 to 6,000 Troi are being put into practical use.

In this case, alternating current loss due to skin effect, proximity effect, etc. becomes a major problem, and multi-segmented conductors, wire insulation, etc. have been considered as countermeasures.

FIG. 1 shows the relationship between the conductor cross-sectional area and the skin effect coefficient, and it was found that the larger the conductor size, the more significant the effect of wire insulation becomes.

By the way, it has been thought to use enamel coating to insulate this wire, and it has been recognized that it is effective against the proximity effect and skin effect, but it is difficult to insulate wire with this enamel coating in order to obtain the specified characteristics. In order to do this, it is necessary to select a coating material and apply a coating with a relatively thick film of 34 to 64 μm, which increases the finished outer diameter of the strands and, in turn, increases the outer diameter of the twisted conductor.

For example, in the case of a cable conductor of 2,500 mm, the outer diameter increases by about 3 Tfgn (equivalent to 300 m!i) due to the use of enamel, and the process of coating the wire with enamel takes time and increases the price. In addition, in the case of sleeve crimping connection, it is necessary to completely remove the enamel film on the connection part, and this removal work uses chemicals and is very time-consuming.

On the other hand, in the case of welded connections, when working inside a manhole, a large amount of harmful gas is generated due to thermal decomposition of the enamel, resulting in the need for a large-scale exhaust gas system. Furthermore, with wire insulation using enamel coating, the stainless steel tape wrapping and internal shielding layer are insulated from the internal conductor, so there is a risk that abnormal voltages that do not occur in normal cables may cause electrical discharge, leading to thermal decomposition deterioration of the enamel coating. be.

For these reasons, it was not put into practical use. In particular, this invention uses a copper wire as a cable conductor, makes it a split compression shaped stranded wire conductor, and insulates the wire with a cupric oxide film in the semiconducting region, which eliminates the drawbacks of the wire insulation with an enamel film described above. , we succeeded in providing a cable conductor that is effective against skin effect and proximity effect.

In other words, the volume resistivity of cupric oxide is in the semiconducting region, which is the object of the present invention to reduce the skin effect, and the object of the present invention is the stranded wire conductor that has been split and compressed. It is particularly effective in relation to structure.

In other words, the fan-shaped parts that make up the divided parts are insulated from each other by cupric oxide, and are twisted together at a pitch of a fixed length (usually 20 to 30 C!n). , and each fan-shaped part of this is its outer periphery,
Since the inner periphery is coated with the cupric oxide semiconducting resistor, the resistance between the strands is sufficiently larger than the resistance in the longitudinal direction of the copper strands, so the copper strands are electrically independent. Since the strands have a stranded wire structure, each of the sector-shaped parts described above can equivalently have an approximately uniform inductance, so current flows uniformly to each sector-shaped part of the divided part. , the skin effect can be effectively reduced.

Even with the resistance value of this semiconducting region, the potential difference between each copper wire constituting the conductor in the above-mentioned structure, which is the object of the present invention, is as low as about 1 mV. Therefore, the resistance value is sufficient to insulate against this voltage. Even if a high voltage is applied to the conductor, the potential sharing is small, so the occurrence of discharge due to abnormal voltage or charging current can be prevented. In order to satisfy the above requirements, the volume resistivity must be ρ=101 to 1σΩ even if the film ζ thickness is taken into account. C77! It is sufficient if it is of a certain extent.

Furthermore, as mentioned above, no discharge occurs in the present invention, but in the conventional insulation using an enamel film, the volume resistivity p'' of the enamel film is ρ''=1013 to 1015 Ω.
Cm is high and the coating thickness is thick, resulting in capacitance distribution and high voltage sharing, so discharge occurs between the strands that make up the conductor, the contact resistance of the conductor becomes zero, and there is no point in providing a coating.
Degrading gases (for example, C2H2, etc. in the case of 0F cables) are generated and deteriorate the insulating oil and the insulator as well, but the cupric oxide film of the present invention having a resistance in the semi-conducting range can overcome this problem. Nothing like that happens.

As shown in FIG. 2, the wire insulation used in the present invention comprises a copper wire 12 coated with a cupric oxide film 14 to form a wire insulated wire 10. ) or above to form a cupric oxide film 14 on the surface, or use other chemical oxidation techniques, such as placing the copper wire in an oxidizing agent mixture of sodium chlorite and hydric soda. By immersing the copper wire, it is possible to obtain a copper wire, that is, a wire insulated wire, whose surface is oxidized and a cupric oxide film is formed. The method of forming a cupric oxide film on a copper wire is extremely simple, the film is thin, and it is strong and integrated with other copper wires, so it is not susceptible to mechanical friction, bending, etc. It is chemically stable and thermally strong without fear of peeling, and has a volume resistivity of ~1σΩ, which has sufficient performance for strand insulation. Cm and is semiconductive, allowing conventional conductor shielding design.

On the other hand, the cuprous oxide film has a resistance of 1CP to 1σΩ. Cj!
Its volume resistivity is mechanically weak, chemically unstable, and has poor heat resistance, and it cannot be used for wire insulation because it cannot obtain a surface resistance suitable for wire insulation. Coatings including cuprous oxide coatings, which are commonly referred to as copper oxide coatings, also have the aforementioned unfavorable properties and cannot be used for wire insulation.

In the present invention, a copper wire provided with such a cupric oxide film is used to construct a cable conductor, as shown in FIG. 3, for example.

That is, a plurality of copper wires are twisted together and compressed to form a segment 20, and from the surface of each segment 20, the copper wires of the second layer 22 are insulating elements having a cupric oxide film. The first surface layer 26 and the inner layer 24 are made of ordinary copper wire. Note that although the number of segments is six in the figure, it is not limited to this.
Furthermore, the wires having a cupric oxide film may be arranged in the same twisted wire layer position in each segment other than the surface of the segment 20; Of course, it may also be a line. As described above, the structure of the cable conductor using copper bare wire is a split conductor, and the bare wire insulated wire with cupric oxide film is placed in each segment at least at the same strand layer position in the conductor. In addition to being able to suppress the proximity effect to a small extent by disposing the insulating material in As an effect, when making a connection, the cupric oxide film can be easily removed using a weak acid solution or mechanical means, so welding connections are easy, especially when the wire insulation is near the surface layer. The oxide film on the strands of wire is very efficient to remove, and the film thickness is about 0.5 to 1.
Because it is as thin as μm (i.e., 50.3 to 3.0 pm), the finished conductor diameter does not become too thick, it is stable against insulating oil, and has a volume resistivity of 101 to 103 Ω. With Crfl, it is possible to promote the practical application of wire insulation for the first time without causing the various drawbacks of the enameled wire insulation described above.

[Brief explanation of the drawings] Fig. 1 is a diagram showing the relationship between the skin effect coefficient and the conductor cross-sectional area, Fig. 2 is a sectional view of an insulated wire used in the present invention, and Fig. 3 is a diagram showing the relationship between the skin effect coefficient and the conductor cross-sectional area. It is a sectional view showing the structure of an example of implementation. 10... Insulated strand, 12... Element wire, 14
...... Cupric oxide film layer, 20 ... Segment, 24 ... Inner layer, 22 ... Second layer (CLlO
With film).

Claims (1)

[Scope of Claims] 1. In a split compression shaped stranded wire conductor constructed by twisting copper wires, each segment of the wires is provided with an insulating film made of cupric oxide. A cable conductor characterized in that the cable conductor is arranged in one layer in a position where the layers are twisted in the same way. 2. In a split compression shaped stranded wire conductor constructed by twisting copper wires, a wire provided with an insulating film made of cupric oxide is applied to the surface layer of the split compression shaped stranded wire conductor. 2. A cable conductor according to claim 1, characterized in that the cable conductor is arranged as follows.