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Description

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JSTS [BJ 11 UTLÄOGNINOf SKRIPT 6291 3 5¾¾ C Patent granted 10 03 1983

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France-France (FR) 7708106 (71) Jeumont-Schneider, 31-32 Quai National, 92806 Puteaux (Hauts de Seine), France-France (FR) (72) Valentin Bardoux, Jeumont (Nord), France-France (FR) ) (7M Oy Kolster Ab (5 * 0 Method for sealing a power cable with synthetic insulation in the longitudinal direction to prevent water transfer in it)

The invention relates to a method for longitudinally sealing an electric cable, in which a conductive substance is possibly placed on top of the plastic insulation, a sealing material is placed on it, a metal sheath is placed on it and a plastic cable sheath is placed on it. The invention is particularly applicable to a single-pole medium-voltage cable with synthetic insulation, comprising in particular the following parts: - a multi-stranded or massive conductive cable core of copper or aluminum, - semiconductor sheath around the core, polyethylene, etc.), 2. 62913 - possibly a semiconductor cladding around the insulation, which may be, for example, lacquer, a suitable strip or extruded material, - metal cladding, in the form of strip, extruded or tubular, - outer cladding, usually extruded.

In the case of a three-pole cable or, in general, a multi-conductor cable, the insulated parts are assembled in a sealing housing before the metal cladding and the protective cladding are connected to the cable.

When the cables are in use, they need to both heat up and cool down. As the cable heats up, it expands, allowing the diameter of the insulation to increase by several millimeters. Once the cable has cooled, a considerable void is created between the insulator (or the semiconductor on top of it) and the inelastic metal cladding. To make the cable tight, one solution is to insert a sealing material between the insulator (or the semiconductor on top of it) and the metal cladding, which expands under the influence of water (e.g. some cellulose powder, or kaolin or a homogeneous mixture of aluminum sulphate, petrolatum and oil). However, this solution is difficult to apply in practice, as it is not easy to obtain sufficient sealing material on the smooth insulation (or the semiconductor around it.

During the external cladding of the cable or if it is damaged, water can enter the cable, as a result of which - water can corrode the metal cladding, - move along the cable and penetrate eg switch and distribution boxes and cause breakthroughs.

With the present invention, this drawback can be eliminated by changing the appearance of the insulator (or the semiconductor around it) so that the expansion of the metal cladding can be limited and sufficient sealing material can be used.

The method according to the invention for sealing a synthetic cable with synthetic insulation longitudinally "waterproof" aims to provide a protective sheath surrounding the metal cladding and an insulating or semiconductor material under the metal cladding. longitudinal grooves in the cable are formed on the upper surface of the layer and that an expanding sealant is placed in the grooves in the presence of water.

The invention will be described in more detail below with reference to the accompanying drawings, which illustrate two structural examples.

Fig. 1 is a section of a single-pole cable according to the invention without semiconductor sheathing on the insulator, and Fig. 2 is also a section of a single-pole cable according to the invention with semiconductor sheathing on the insulator.

In Figure 1, the stranded Aluminum wires 1 form the electrically conductive core 2 of the cable, surrounded by a semiconductor sheath 3. On it is an insulator 4 made of chemically crosslinked polyethylene. The insulator 4 is pressed so that grooves 5 are obtained on its outer surface. The surface part of the grooves is shown in section 6. The grooves are made in the longitudinal direction of the cable. The edges 7 of the grooves are pressed into the inner surface of the aluminum cladding 9. Section 8 shows a sealing material, e.g. cellulose powder, placed in the recess of the groove 5. Section 10 shows a PVC molded cover housing.

Figure 2 shows a structure otherwise comparable to Figure 1, but the cable now has a semiconductor sheath 11 pressed over the insulator 4. In this structure, the grooves are not made in the insulator 4, but in the semiconductor sheath 11 on it.

Before attaching the metal cladding to the cable, the above-mentioned recesses are filled with sealing material 8. As the cable heats up, the edges 7 of the grooves 5 are compressed and act as a kind of damping pads and limit the expansion of the metal cladding 9. In addition, this arrangement provides continuous contact between the semiconductor 11 on the insulator and the metal cladding, regardless of the sealing material 8.

The invention can be applied to all types of cables which are desired to be sealed and which have a metal cladding and an underlying part of a pressed synthetic material.