JPH04136150A - Production of wire-insulated conductor - Google Patents

Abstract

PURPOSE:To form copper oxide coating films of nearly uniform thickness on the surfaces of wires at the inner and outer layers of a stranded copper wire conductor by heating the conductor in an atmosphere of wet ammonia while periodically fluctuating the temp. of the atmosphere from the temp. of the conductor. CONSTITUTION:When copper oxide coating films are formed on the surfaces of wires forming a stranded copper wire conductor (power cable) while heating the conductor in an atmosphere of wet ammonia, the temp. of the atmosphere is periodically fluctuated from the temp. of the conductor preferably with a period of about 10-60min within the temp. range of about + or -10 deg.C. The diffusion of ammonia between the wires is facilitated, the formed coating films are made nearly uniform in thickness at the inner and outer layers of the conductor and a wire-insulated conductor having a satisfactory state of the coating films is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in the manufacturing method of a stranded insulated conductor, and in particular to an improvement in the manufacturing method of a stranded conductor with less variation in thickness on the surface of each strand in the inner and outer layers of a copper stranded conductor. The present invention relates to a manufacturing method for forming a film.

(Prior Art) In recent years, as the demand for electric power has increased, the size of electric power cables has also increased. As such a power cable, a split conductor type cable is used, in which individual wires are twisted together and then compressed into a fan-shaped cross section to form compressed conductor segments, and these segments are further twisted together. In this split-conductor type cable, each segment is usually insulated with an insulating tape or the like, and each strand is also insulated to reduce alternating current resistance due to the skin effect as an insulated strand conductor.

One method for producing such a wire insulated conductor is a method called a dry method in which a copper oxide film is formed in an atmosphere of ammonia gas, water vapor, air, or oxygen, ie, a so-called wet ammonia atmosphere.

In this method, a copper stranded wire conductor is placed in an oxidation treatment bath containing a moist ammonia atmosphere, and a copper oxide film is formed on the surface of the wire while heating. Conventionally, the ambient temperature was set several degrees Celsius higher than the conductor temperature, and heating was performed from room temperature to 60 to 90 degrees Celsius over a period of 20 to 30 hours.

(Problem to be Solved by the Invention) By the way, when a wire insulated conductor is manufactured by the conventional method as described above, there is a large difference in the thickness of the insulation coating between the outer layer and the inner layer of the segment, for example, the outermost layer has a thickness of about 5 μm. A problem arose in that the innermost layer was coated with a thickness of only about 1.5 μm.

This is because each strand of the segment is compressed, so there is only a small gap, and if the ambient temperature is higher than the conductor temperature, steam condenses between the strands in the outer layer of the conductor, forming a thin film of water. This is because it becomes difficult for ammonia gas to penetrate into the inner layer.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method that allows ammonia gas to sufficiently penetrate into the inner layer of a segment to produce a wire insulated conductor with less variation in coating thickness for both the inner and outer layers.

(Means for Solving the Problems) In order to achieve the above object, in the present invention, when heating a copper stranded wire conductor in a moist ammonia atmosphere, the atmospheric temperature is periodically raised and lowered around the conductor temperature. It is characterized by heating.

Here, the period for raising and lowering the atmospheric temperature is 10 to 6.
Preferably every 0 minutes. The reason is that if the cycle is shorter than 10 minutes, the desired effect cannot be obtained;
This is because the effect remains the same even if the duration is longer than 1 minute. Further, it is preferable that the temperature range to be raised or lowered is within ±10°C. The reason for this is that if the ambient temperature is lower than 10°C compared to the conductor temperature, the film formation will be insufficient.
Even if the temperature is higher than 0℃, there is no significant change in the film formation effect.
This is because temperature control becomes more difficult.

(Function) Even if the ambient temperature is higher than the conductor temperature and steam condenses on the wire surface to form a water film, the next time the ambient temperature drops, this water film evaporates and ammonia gas is formed between the wires. Entry becomes easier. Subsequently, the formation of an oxide film is promoted by raising the ambient temperature again. By continuing such cycles, an insulating wave film with less variation in thickness can be formed.

(Example) Next, examples of the present invention will be described.

(Example 1) 3% of the 7-segmented conductor with a cable conductor cross-sectional area of 3000 mm2
It was placed in a sealed oxidation treatment tank containing aqueous ammonia, and then placed in a constant temperature oven and heated to 60°C. The processing conditions at this time were to adjust the ambient temperature to ±8°C in 30 minute cycles relative to the conductor temperature.
The heating time was 20 hours.

(Example 2) The same conductor as in Example 1 was placed in a sealed treatment layer containing 5% ammonia water, and further placed in a constant temperature oven and heated to 80°C. The processing conditions at this time were that the ambient temperature was raised and lowered by ±6° C. in 40 minute cycles with respect to the conductor temperature, and the heating time was 26 hours.

(Comparative Example 1) The ambient temperature was raised and lowered by +20°C and -12°C with respect to the conductor temperature, and the other conditions were the same as in Example 1.

(Comparative Example 2) The ambient temperature was raised and lowered by +18°C and -15°C with respect to the conductor temperature, and the other conditions were the same as in Example 2.

(Comparative Example 3) The ambient temperature was set to +8° C. with respect to the conductor temperature, and heating was performed without periodically changing the temperature. Other conditions were the same as in Example 1.

(Comparative Example 4) The ambient temperature was set to +6° C. with respect to the conductor temperature, and heating was performed without periodically changing the temperature. Other conditions were the same as in Example 2.

The results of the above examples and comparative examples are shown in the following table.

(Left below) As is clear from the above results, the conventional technology (Comparative Example 3)
In contrast and 4), the variation in coating thickness between the inner and outer layers is very large, whereas the variation in coating thickness decreases when the ambient temperature is periodically raised and lowered relative to the conductor temperature, and especially in the method of the present invention, A wire insulated conductor with little variation in coating thickness and good coating condition can be obtained.

(Effects of the Invention) As explained above, according to the present invention, since the ambient temperature is periodically raised and lowered relative to the conductor temperature, ammonia gas can easily enter between each strand, and the inner and outer layers are coated. A strand insulated conductor with less variation in thickness and a good coating state can be manufactured.

Claims (1)

[Claims] In a method for manufacturing a stranded insulated conductor in which a copper stranded conductor is heated in a wet ammonia atmosphere and a copper oxide film is formed on the surface of each strand constituting the copper stranded conductor, the atmospheric temperature of the wet ammonia atmosphere is adjusted to A method for manufacturing a wire insulated conductor, which is characterized by heating while periodically raising and lowering the temperature.