JPS6031050B2 - Manufacturing method of strand insulated conductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a strand insulated conductor with reduced AC resistance due to the skin effect, which is used for large-capacity power transmission in power cable conductors and the like.

In recent years, as the demand for electricity has increased, the conductors of power cables have become larger and larger, and the cross-sectional area of the conductors is usually 10.
For large-sized conductors larger than 00 fences, split conductors are used, which are made by gathering the required number of segment conductors (also simply called segments), which are made by compression-molding the cross-section of twisted steel cables into a fan-shaped shape and have a circular cross-section. For example, the cross-sectional area of the conductor is 25
00 fence divided conductors have been put into practical use.

In such large-sized conductors, alternating current resistance increases due to the skin effect, so it is important to reduce the skin effect from the viewpoint of allowable current.

For example, a 6-divided conductor with a conductor cross-sectional area of 3000 squares (conductor outer diameter 7
0.6 skin, conductor inner diameter 19.6 ribs), AC resistance R^ with respect to DC resistance Roc. (in 2 ACs for 60 days) ratio (
R^c/Roc) reaches 1.27 (measured according to Japan Cable Industry Standard JCS-1). As a method to reduce such a large skin effect, the conductor is divided into multiple segments, insulating each segment with insulating tape, etc., and each wire that makes up the segment is also insulated, i.e. This wire insulation is used to prevent current from concentrating on the surface layer of the conductor.

As a related matter, there are examples of using enamel-coated steel cables as a method of insulating the strands, but the film needs to be 20 to 30 µm thick to withstand the twisting process of the strands and the subsequent compression molding process. This method requires an enamel coating of more than m, which has the drawback of extremely high cost.

For this reason, as a cheaper method, the use of strand insulated conductors in which a black oxidized steel film is formed on the surface of a steel cable is being put into practical use.

The wire insulated conductor with a black oxidized steel coating has a coating thickness of 0.5 to 2 meters, which is extremely thin and has good electrical and mechanical properties, as well as excellent chemical properties. It is known to have stability. Currently, as a method for manufacturing wire insulated conductors provided with such an oxidized steel film, an alkaline aqueous solution (N
A method has been adopted in which the stranded conductor is chemically oxidized with the aid of an oxidizing agent such as chlorous acid (NaCSO2) or potassium persulfate (K2S208) in aOH).

The oxidized steel that is wet-produced in this way is composed of microcrystalline materials, and has the characteristics of being relatively resistant to processing and having excellent adhesion to steel interfaces. However, in this method, an oxidized steel film is formed to the required thickness on the wires inside the twisted conductor, especially on the parts where the wires intersect and are in close contact with each other due to twisting or compression molding, thereby completely insulating the wires. In order to do this, it is necessary to use methods such as using ultrasonic waves to promote the penetration of the treatment liquid between the wires, and the treatment takes several days, and it is difficult to completely wash out the treatment liquid that has entered the conductor with water. It was difficult to remove and dry.

The present invention was made as a result of intensive research in view of the current situation, and an object of the present invention is to provide an economical and highly productive method for manufacturing a high-performance wire insulated conductor with a large wire insulation effect. do. In other words, the present invention is capable of heating a conductor made of twisted steel cables in a moist ammonia atmosphere at a heating rate of 1,500/cm.
This is a method for manufacturing a wire insulated conductor, characterized by maintaining the ambient temperature at 40 to 80° C. for a period of time or less. In the present invention, the temperature increase rate of the wet ammonia atmosphere is extremely important for the formation of the copper oxide film, and the salt increase rate must be 1500/hour or less.

The thickness of the copper oxide film formed at the overflow rate of 1500/hour is significantly different.When the heating rate is below 1500/hour, the smaller the heating rate, the thicker the copper oxide film formed. The relationship changes almost linearly. In other words,
When the heating rate is 1500/hour or less, the thickness of the produced steel oxide film decreases linearly as the heating rate increases. On the other hand, if the temperature increase rate is 15°C/hour or more, the heating rate will be at most 0.
A film thickness of only 6 to 0.7 A is produced, and even if the treatment time is increased, a film thickness greater than this cannot be obtained. Since ammonia gas is toxic, the process of the invention is preferably carried out in a closed container.

For example, a stranded copper wire conductor to be treated is placed in a sealed container, ammonia water or water and ammonia gas, and oxygen if necessary are added to the container, and the container is sealed. Place the heated container in a heating furnace or water tank,
It is common and preferred to raise the ambient temperature in the closed container at a temperature increase rate of lyo/hour or less and maintain it at a predetermined temperature of 40 to 80 qo. Oxygen is necessary for the surface of the steel cable to oxidize and form a copper oxide film, but since air is present in the container when the conductor is placed in the container, it is generally not necessary to introduce oxygen. However, when a large amount of conductor is loaded, it is preferable to introduce oxygen. In the present invention, a conductor made of twisted steel cables is a conductor made by simply twisting a desired number of steel cables, or a conductor obtained by compression molding this conductor, and the shape of the conductor is not limited at all.

Regarding split conductors, it is common to insulate each segment using the method of the present invention and then turn the segment into a split conductor. Line insulation may be applied to the entire divided conductor. Next, the present invention will be explained using Examples and Comparative Examples. Example 1 Eight strands of European copper wire with a diameter of 2.3 mm were twisted together, and the segments were compressed into a fan-shaped cross section and placed in a stainless steel container. Then, 20% ammonia water was poured into the container and the container was sealed. Immediately, the thus sealed container was placed in a water tank, and the atmospheric temperature inside the container was raised to 60 oo at the temperature increase rate shown in Table 1.

One field hour after the start of temperature rise, the container was removed from the water tank and the segment was taken out from inside the container. When one part of the thus treated segment was disassembled, it was found that a copper oxide film was evenly formed on the wires inside the segment. Next, the thickness of the copper oxide film was measured, and the results are also listed in Table 1. Comparative Example 1 As shown in Table 1, a copper oxide film formation treatment was performed on the segments in exactly the same manner as in Example 1 except that only the temperature increase rate was changed.

When part of the thus treated segment was disassembled,
There were parts of the Qin wire inside the segment where no steel oxide film was formed, and the copper color was exposed in spots. The thickness of the steel oxide film on the wire at the outermost portion of the segment was measured, and the results are also listed in Table 1. Table 1 Next, M. Twist six segments of No. 1 together to obtain a divided conductor with a conductor cross section of 200 mm, and for this divided conductor, calculate the DC resistance value Roc and the AC of 60 days 2 according to the measurements shown in the Japanese Cable Industry Standard JCS-1. The AC resistance value R^c was measured and the ratio (R^c/RDc) was found to be 1.04.

Also, the land of Comparative Example 1. A divided conductor completely similar to the above was obtained using 3 segments, and the same ratio (R^c/Roc) was found to be 1.14 for this divided conductor as well. Example 2, Comparative Example 2 After putting the same untreated segment as in Example 1 into a stainless steel container, water and ammonia gas (25% concentration) were added and the container was sealed, and the container was immediately placed in an electric furnace.
By adjusting the temperature increase rate of the electric furnace, the temperature was raised at the temperature increase rate shown in Table 2 until the atmospheric temperature within the container reached 75q0, and was maintained at 750o.

The treatment was completed one hour after the start of temperature rise. Next, the results were measured in the same manner as in Example 1 and are also listed in Table 2. Note that, as is clear from Table 2, Example 2 and Comparative Example 2 differ only in the rate of temperature increase, and are otherwise the same.

In addition, in the segment treated in Example 2, the copper oxide film of the Qin wire was uniform even inside the segment, whereas in Comparative Example 2, it was seen that the copper color remained in spots on the inner wire. It was done.

As is clear from Table 2 and the examples, according to the present invention, a relatively thick copper oxide film is uniformly formed on the surface of all the wires of the conductor in a short period of time, and as a result, the skin effect is reduced. It is possible to produce a lossy strand insulated conductor, which is extremely useful in practice.

Claims (1)

[Claims] 1. An insulated strand conductor comprising a conductor made of twisted copper strands, which is maintained at an ambient temperature of 40 to 80°C at a heating rate of 15°C/hour or less in a moist ammonia atmosphere. manufacturing method. 2. The method for manufacturing a wire insulated conductor according to claim 1, wherein the moist ammonia atmosphere contains ammonia, water vapor, and oxygen.