JPS5943616Y2 - Single core lead submerged bottom cable for power use - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a single-core lead-covered underwater cable for electric power.

Generally, as shown in Fig. 1, an underwater power cable has a lead sheath 2 and a plastic protective layer 3 such as polyethylene on the outer periphery of a cable core 1, and on top of that a jute,
An exterior 5 made of a plurality of iron wires is provided through a seat 4 made of plastic string or the like, and on the exterior 5 a pressing layer 6 made of jute, plastic cord, etc. and a paint layer (not shown) are applied. ing.

However, in the case of a single-core cable, the armored iron wire generates heat due to the induction effect caused by the current flowing through the cable conductor, reducing the current capacity of the cable.

In order to eliminate the drawbacks of single-core lead-covered underwater cables with iron wire sheathing, a round electrical conductor such as copper or aluminum is used as the sheath wire instead of the sheathed iron wire, and this sheath wire is used as a return conductor for induced currents. A submersible cable was proposed.

Although such cables can prevent reduction in current capacity,
During long-term use, the electrical conductors on the exterior were corroded by seawater.
The substantial cross-sectional area is reduced and the cable does not function adequately as a return conductor, resulting in a reduction in the current carrying capacity of the cable.

The present applicant has recently proposed an improved single-core lead-covered underwater cable which eliminates the drawbacks of the above-mentioned known or proposed underwater cables and prevents a decrease in the current capacity of the cable.

Its structure is as shown in Figure 2, with a seat 4 made of jute or plastic string placed on a lead sheath 2 on a cable core 1.
A return conductor 7 made of a flat electrical conductor is provided via the plastic protective layer 3, and a seat floor 4' is placed on top of the return conductor 7.
An iron wire sheath 5 is provided through the cable, and a pressure winding layer 6 and a paint layer (not shown) are applied on the iron wire sheath 5 in the same manner as in known cables.

As mentioned above, the improved underwater cable has a return conductor, which prevents the current capacity from decreasing, but since the return conductor is located inside the plastic protective layer, there is no risk of corrosion. This has the advantage of not causing dissimilar metal corrosion between the exterior iron wire and the exterior iron wire.

However, the drawback of this cable is its productivity.

That is, this cable requires three steps: winding the return conductor, extruding the plastic protective layer, and winding the outer iron wire.

The reason is detailed below.

The manufacturing equipment for electric cables is equipment A that winds tapes, strips, or wires made of steel, etc.
and Facility B, which extrudes and coats plastics, are different from each other, and it is common that they are not arranged in tandem for reasons such as improving the operating efficiency of each facility and the problem of the site. be.

Therefore, in the cable portion composed of the return conductor 7 made of a flat electrical conductor + the plastic protective layer 3 + the iron wire sheath 5, the return conductor 7 is provided by the equipment A, the protective layer 3 is provided by the equipment B, and the iron wire sheath 5 is is manufactured by equipment A.

That is, the supply pick-up is repeated three times, requiring three steps.

Further, for example, in a cable portion consisting of a plastic protective layer of 3,000 yen, the return conductor 7 and the iron wire sheath 5, the protective layer 3 is manufactured by the above equipment B, and the return conductor 7 and the iron wire sheath 5 are manufactured by the above equipment A. manufactured at the same time.

In other words, supply pick-up only needs to be repeated twice,
Since it is manufactured in two steps, it can be said that productivity is much improved compared to the cable structure that requires three steps.

The present invention eliminates the drawbacks of the previously proposed single-core lead-sheathed underwater cable, and in particular improves the electrical characteristics in terms of limited productivity and productivity, which is equivalent to the underwater cable newly applied by the applicant. The company provides single-core lead-sheathed submarine cables.
The cable has a plastic protective layer on the lead sheath, a return conductor made up of a plurality of round electrical conductors on its outer periphery, and an exterior sheathing made of electrical strips on its outer periphery.

Note that the term "electrical strip" as used herein refers to a strip-shaped, ie, tape-shaped electrical conductor such as copper or aluminum.

FIG. 3 is a cross-sectional view of an embodiment of the single-core lead-covered underwater cable according to the present invention, in which the same symbols and the same parts as in FIGS. 1 and 2 are used.

A return conductor 27 is provided on the plastic protective layer 3 made of polyethylene or the like on the cable lead sheath 2 through a seat 4 made of jute, plastic string, etc., and constituted by winding a plurality of round electrical conductors. There is.

On the return conductor 27, there is an exterior sheath 25 provided by horizontally wrapping electrical strips through the seat floor 4', and on top of that there is a pressing layer 6 and a paint layer (not shown). There is.

Next, the table below shows a comparison of the structures of the 525KV, 2500rr L2 single-core lead-covered underwater cable of the present invention and other cables.

As is clear from the above table, the effective cross-sectional area A of the cable of the present invention as a return conductor is larger than that of Comparative Example 2 using a flat conductor, and the finished cable outer diameter is larger than that of Comparative Examples 1 and 2.
It can be seen that it is smaller than

The reason why the effective cross-sectional area A of the flat return conductor is smaller than that of the round return conductor in Comparative Example 2 is because the thickness of the flat conductor is considered to be at its limit of about 3 to 5 mm, and if This is because it is difficult to increase the thickness for the following reasons.

■ Because it is flat, it is not easy to wrap around.

@ The widthwise surface of the flat conductor is difficult to follow the circumferential surface of the cable, and the corners of the flat conductor stand out, which may damage the layers provided above and below.

When the O-cable is bent or the coil is removed, laughter may occur in the flat conductor, and once it occurs, it may not return to its original state.

Therefore, even if the thickness of the flat conductor is 5m+n, the effective cross-sectional area A as a return conductor in Comparative Example 2 is 195
Only 0rIaI can be obtained, and it cannot be made larger than that of the round return conductor of the present invention.

The single-core lead-covered underwater cable for electric power according to the present invention as described above has the following advantages.

(1) As mentioned above, since it has a return conductor, it is possible to prevent a decrease in current capacity, but in particular, since a round electrical conductor is used as the return conductor, its effective cross-sectional area is large, and its effectiveness as a return conductor is is remarkable.

(2) Since there is no protective layer between the return conductor and the exterior as in the new proposal mentioned above, both can be performed in the same process.
The work process becomes easier.

(3) Since electrical conductors are used for both the return conductor and the exterior, dissimilar metal corrosion (metallic corrosion) does not occur.

0) The outer diameter of the cable is small because electrical strips are used as the exterior.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing an example of a conventional single-core lead-covered underwater cable, Fig. 2 is a cross-sectional view of a newly proposed underwater cable, and Fig. 3 is a cross-sectional view of an example of the underwater cable according to the present invention. FIG. 18.・Cable core, 2... Cable lead sheath, 3.・
・Plastic protective layer, 4.4'... Seat floor, 25. ,
, exterior, 2T...return conductor.

Claims (1)

[Scope of utility model registration request] A power unit comprising a plastic protective layer on the cable lead sheath, a return conductor made up of a plurality of round electrical conductors on the outer periphery, a seat layer on top of the return conductor, and an exterior covering made of electrical strips on the outer periphery. Lead-core underwater bottom cable.