DE2932947A1 - INSULATED HIGH VOLTAGE CABLE - Google Patents

Description

Dipl.-Ing. H. MITSCHERLICH D-8000 MÖNCHEN 22

Dipl. -Ing. K. GUNSCHMANN Steinsdoffstrasse 10

Dr. rar. .at. W. KÖRBER Ά ^{9 (} ° ⁸⁹⁾ ' ²

Dipl.-Ing. J. SCHMIDT-EVERS PATENTANWÄLTE

August 14, 1979

OY NOKIA AB
Pursimiehenkatu 29-31
00101 Helsinki 10
Finland

Insulated high voltage cable

Π30009 / 0846

2932S47

The present invention relates to an insulated high voltage cable , which comprises an insulation layer and an electrical conductor located therein, the one stranded from metal wires Inner part and a tubular enveloping this jacket, mainly made of the same metal.

A conductor is previously known which is normally made entirely of stranded wires from separate wires. The disadvantage here is the inadequate tightness of the surface and also the unevenness of the surface, which among other things causes a disadvantageous corona phenomenon in high-voltage cables.

Also known is a ladder construction (DE-PS 2.162.210), where the top layer consists of a metal tube, the task of which is, among other things, to protect the conductor from corrosion.

On the other hand, it is difficult or impossible to make out materials that the Withstands corrosion significantly better than aluminum, with processes suitable for aluminum a pipe that would meet the same requirements, to manufacture. For example, the surface of a weld seam is never as smooth as an unhemmed pipe, and the tightness of the seam is not reliable

In a tubular and, above all, in a solid ladder is the Generally known disadvantage is that the inductive resistance in the case of alternating current is somewhat greater than in a conventionally stranded conductor especially in a conductor with a large cross-sectional area.

However, the relative adverse influence can thereby be reduced that the thickness of the pipe wall is kept within reasonable limits. In addition, the pipe has a structurally better conductivity than the surface layer of a stranded conductor. The safety of the manufacturing process promotes the economic possibilities that To increase the cross-sectional area of the conductor to a sufficient extent for alternating current.

So Bisner was thought that a tubular metal jacket wasn't should be used as the outermost layer of a stranded conductor, because the AC resistance of such a conductor is what the The cross-sectional area is somewhat larger compared to the same-sized conventional sheathed conductor, due to the influence of eddy currents.

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But now it has surprisingly been found that this influence is completely insignificant compared to the advantages that can be obtained using shell constructions of some kind.

The invention is based on the idea that the conductor has a tubular, dense and smooth outer layer made of aluminum. A known conductor is located inside the tube, initially a conductor stranded and sealed with the aluminum or copper wires. The manufacturing mass of the pipe and the inner part have a small gap.

More precisely, the cable according to the invention is mainly characterized in that the metal jacket is made of aluminum, its outer surface is smooth on the whole, its cross-sectional area is 5 to 50 % of the total cross-sectional area of the electrical conductor and is arranged around the inner part with a gap, which corresponds at least approximately to a loose sliding fit.

By means of the invention, almost all of the good properties become advantages of a solid conductor, but the flexibility is much better. The tightness of the surface of the conductor is an advantage, though a conductor by means of sheathing with plastic or a corresponding one Material is processed into a cable: in high-voltage cables with a conductor protection and insulation and in a low-voltage cable with an isolation. When sheathing an ordinary stranded conductor, namely, the plastic or a corresponding material can be between the Wires penetrate, which often causes damage to the cable when the conductor is stressed. Another advantage is the reliable tightness is shown in the event of any damage to the cable: if water reaches the undamaged conductor, it is sufficient to use the repair damaged area. The same applies if the enveloping pipe is damaged: the water gets inside the conductor, but it does cannot leak elsewhere and damage the insulation. Here, too, it is sufficient to repair the damaged area. The smoothness the surface of the conductor again results in the fact that the conductor protection to be attached to a high-voltage cable can be thinner,

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than on a relatively uneven stranded conductor. In one In a similar way, insulation that is to be attached directly to the conductor comes into contact with a smooth surface on low-voltage cables Increases the reliability of the cable and makes the insulation itself easier. When the conductor is bent, the pipe can also be used to achieve it easily follows bending, because the manufacturing process, usually extrusion known per se, presupposes soft aluminum.

In addition, the space between the tube and the inner part leaves a mutual movement too. At the same time, the tube eliminates the risk that those in the top layer of a stranded conductor will lie close to one another If the wires slide during the bend, they would damage the plastic on the cable.

In the following, the invention will be considered in more detail with reference to the accompanying drawing illustrating preferred embodiments of the invention.

FIG. 1 shows in cross section an electricity conductor of circular cross section of a cable according to the invention.

FIG. 2 shows in cross section an electricity conductor of a cable according to the invention, which is sector-shaped in cross section.

FIG. 3 shows a cable according to the invention in cross section.

The inner part 1 of the cable is stranded in a manner known per se and can be unsealed or, in order to save space, be sealed (FIG. 1). On the stranded part is a known manner tubular casing part 2 made of aluminum has been extruded so that a small gap remains free between this and the inner part 1, or so, that it is at most slightly in contact with the inner part 1. Instead of extrusion, any method known per se can be used, by means of whose tubular casing part is tight and smooth on the outside can be made, e.g. by means of pipe welding processes of various kinds, where an aluminum strip is used as the starting material.

In principle, the tubular casing part 2 should be as thin as possible, but not so thin that it wrinkles. On the other hand, the tubular jacket part 2 forms a substantial Ipart, for example 20 to 50 % of the

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ORIGINAL INSPECTED

total cross-sectional area of the conductor.

A 100 kV cable is mentioned as an example, where the total cross-sectional area of the conductor made of aluminum is 1400 μm. The diameter of the conductor is 44 mm. The average thickness of the shell part is about 3 mm (lowest limit 2.75 mm). The aluminum jacket 2 is covered by a semiconducting conductor protection layer 3, the thickness of which is approximately 1 mm. The thickness of the insulating layer 4 enveloping this layer is approximately 15 nm. The insulating layer is furthermore of a 0.5 to 2.0 mm thick semiconducting the insulating protective layer 5 ₃ of a 3 mm thick contact protection or the like. Metal layer 6 and extremely _{enveloped by a 3 ½} 5 mm thick plastic jacket 7.

The space between the casing part 2 and the inner part 1 is of the order of 0.1 mm, which corresponds to a loose sliding fit.

Because the outer surface of the casing part 2 is smooth, it has Surface no adverse corona phenomena.

It goes without saying that the idea according to the invention also can be transferred to conductors with a cross-section deviating from the circular shape, e.g. to a sector element according to Figure 2.

Of course, the structure of the inner conductor part can differ from the above-mentioned exemplary embodiments. Thus he can e.g. be steel reinforced.

The patent attorney

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Claims (5)

Patent claims: Insulated high-voltage cable, which comprises an insulation layer and an electrical conductor located therein, which comprises an inner part stranded from metal wires and a tubular sheath mainly of the same metal, characterized in that the metal sheath (2) is made of aluminum, its The outer surface is smooth on the whole, its cross-sectional area is 5 to 50 % of the total cross-sectional area of the electrical conductor and is arranged around the inner part (1) with a gap which at least approximately corresponds to a loose sliding fit. 2. High-voltage cable according to claim 1, thereby g e k e η η ze Inet that the metal jacket (2) is made of aluminum by extrusion. 3. High-voltage cable according to claim 1, characterized in that the space mentioned is in the order of magnitude of 0.1 mm. 4. High-voltage cable according to claim 1 or 3, characterized in that the metal jacket is made from an aluminum strip by welding. 5. High-voltage cable according to claim 1, characterized in that the cross-sectional area of the metal jacket (2) is approximately 20 to 50 % of the total cross-sectional area of the electrical conductor. 030009/0846 ORIGINAL INSPECTED