JPS5938681B2 - power cable - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in power cables.

When power cables are recently laid on the seabed or buried underground, when hydrogen sulfide and other sulfides contained in the seabed or underground enter the cable through the sheath of the cable, the sulfur compounds and the copper of the conductor are destroyed. Copper sulfide is formed by contact with wires, which precipitates on the insulator layer made of polyethylene, etc., forming so-called sulfide trees, which significantly reduces electrical insulation and tends to lead to dielectric breakdown of cables during the heating period. . As a countermeasure to this problem, a substance that reacts with sulfides such as lead powder to form an insoluble salt is mixed into the polyethylene of the insulating layer as a sulfide blocker, and the sulfide compound reacts with the copper wire to form a sulfide trichloride. By trapping sulfur compounds that have entered the cable before it is formed, or by coating the outermost layer of the cable with lead or aluminum,
This prevents such problems from occurring. However, the former method, that is, the method using lead powder, is unfavorable from the safety and health standpoint of workers, and it is technically difficult to mix lead powder uniformly into polyethylene, etc., and there is a possibility that lead powder may infiltrate into the cable. The sulfur compound may pass through the gaps between the particles of lead powder, making it difficult to fully demonstrate its effect. Although the latter method is considered to be sufficiently effective in optimizing the price of the cable, the cost of the cable increases significantly, and in the case of lead sheathing, the weight of the cable increases, reducing workability and requiring aluminum sheathing. In this case, they had drawbacks such as being easily corroded when installed on the seabed.
In general, lead is soft and has poor mechanical performance, so even if it is made into a tape, it is easy to cut when used as a value-optimizing layer for an object, such as a power cable, and winding is not possible. There was no other way but to do so.

However, when extrusion coating is used, it is not possible to make the lead coating layer thin and workability is inevitably reduced. As a result of intensive research to improve these drawbacks, the present invention was able to develop a thin lead composite tape that has excellent mechanical performance such as tensile strength. The present invention was achieved based on the finding that the power cable can maintain excellent electrical properties for a long period of time by winding the cable around the cable to form a value-optimizing layer.

That is, the power cable of the present invention has a cable core provided with an electrically insulating layer made of rubber or plastic on the outside of the conductor, and a support made of a copper or copper alloy mesh on one or both sides of which is coated with lead or lead. It is characterized by providing a sulfide layer made of a composite tape made of an alloy adhered to it. The support for the composite tape used in the present invention is preferably flexible, has excellent mechanical performance, and has strong adhesion to lead. 50mes
A wire mesh of about 100mm is good. In the present invention, such a support is used, and lead or lead alloy is adhered to one or both sides of the support, which can be done by cold rolling lead on the support surface or by melting and joining. There is. A particularly preferred method is to immerse a copper or copper alloy wire mesh as described above in a molten lead alloy, cool it, and smooth the surface with a roll to obtain a composite tape. As described above, since the composite tape used for forming the sulfide barrier layer in the present invention has a thin lead layer on one or both sides of the support, the tape body is lightweight and has excellent mechanical performance. When forming the sulfide barrier layer of power cables, winding operations can be performed using normal tape winding methods such as wraparound wrapping and vertical wrapping, which significantly improves productivity and makes the sulfide barrier layer lightweight. can be converted into

In addition, the sulfide layer made of the composite tape of the present invention sufficiently exhibits the effect of sulfur-blocking the cable, and can also be used as a shielding copper tape normally used in power cables. There is no need to provide a shielding metal layer.

Next, examples of the present invention will be described.

A 50-mesh copper plate with round holes punched out from a 0.1 mm thick copper plate was used as a support, and the copper plate was immersed in a pre-molten lead bath for 3 to 5 seconds, taken out and cooled, and then rolled into a roll. The surface of the support was smoothed and a lead layer of 0.1 mm thick was applied on both sides of the support, and the thickness was O, 3!111! A composite tape was obtained.

Since the lead layer was embedded in the mesh portion of the support, it adhered well to the support, and the lead layer did not peel off even when the composite tape was bent. This composite tape was applied to form a sulfide barrier layer for power cables and its performance was measured.

That is, three conductors each having a polyethylene insulating layer and a sulfide barrier layer wrapped with the above-mentioned composite tape provided on the outside of the conductor are twisted together.
A power cable was made by integrating the cables with inclusions such as duet, and providing a protective layer of cross-linked polyethylene on the outside. The power cable thus obtained was laid on the seabed where a large amount of sulfur compounds existed, but no abnormality was found in the cable even after more than five years had passed. In addition, when the above-mentioned cable was not provided with a sulfide barrier layer, the polyethylene insulator layer suffered dielectric breakdown due to the generation of sulfide oxides and became unusable after about 1 to 2 years.

As detailed above, the power cable of the present invention has an excellent sulfur-blocking effect, and in its manufacture, a lead composite tape with excellent mechanical properties such as tensile strength and flexibility is used to form the sulfide layer. It has remarkable effects such as significantly improving productivity and being able to finish at a low cost.

Claims (1)

[Claims] 1. A composite tape made by adhering lead or a lead alloy to one or both sides of a support made of a mesh of copper or copper alloy on the outside of a cable core with an insulating layer made of rubber or plastic provided on the outside of the conductor. A power cable characterized by being provided with a sulfide layer consisting of.