DK2922069T3 - Air Line Cable - Google Patents

Description

DESCRIPTION

[0001] The invention relates to an overhead line cable for high-voltage overhead lines, with at least one metallic core wire and a plurality of wire layers arranged (concentrically) around the core wire (layer stranded).

[0002] A constant problem with high-voltage overhead lines are corona discharges, which occur at high electrical voltages lead to energy losses and disturbing noises. It is known that this effect can be reduced by increasing the cable diameter, because an increase in the diameter leads to a reduction in the edge field intensity and thus to the reduction of the described corona effects. Merely increasing the cable diameter in conventional standard cables, however, usually leads to a significant increase in the cable weight, which in turn leads to other disadvantages, in particular high mast loads or a high degree of sagging.

[0003] For this reason, it has already been proposed to design overhead line cables as hollow cables (cf. EP 1 220 235 B1). The considerably larger cable diameter reduces the corona effect but without increasing the total weight of the line. In practice, such hollow cables have proved to work very well. However, this presupposes the insertion of a tube in the inside of the line, which presents certain challenges as regards production and also installation. There is in principle therefore a need to create alternative overhead line cables which are designed to avoid or reduce corona discharges without involving tubes or hollow cables.

[0004] CH 86777 A proposes a conductor made from a plurality of individual wires, wherein at least a part of the individual wires are designed to be hollow. The intention is to combine solid wires and hollow wires together in order to increase the outer diameter while keeping the same metal cross section.

[0005] A similar cable, which is intended to result in a reduction of corona discharges, is described in FR 931 195. A plurality of layers of single wires is arranged around a core, wherein the individual layers are either constructed entirely of solid wires or entirely of hollow wires.

[0006] In US 2 046 978, an overhead line is described in which a plurality of layers of single wires are arranged around a core, wherein the individual layers consist alternately of hollow wires and solid wires. The problem of the corona discharge is not addressed in this case.

[0007] Elsewhere, WO 88/ 01 430 A1 discloses a self-supporting overhead line cable with a number of metallic wires and at least one strain relief element made from a plurality of strand-like reinforcing fibres arranged in relation to each other, wherein the reinforcing fibres are impregnated with a binding material and form a composite element.

[0008] Finally, electrical transmission line cables with integrated fibre-optic conductors are known, wherein fibre-optic cables or fibre-optic bundles are mounted in a small stainless steel tube (EP 0 286 804 A2). A similar overhead line cable in which fibre-optic elements made of optical fibres are arranged in tubes is described in DE 44 25 464 A1.

[0009] In practice, overhead line cables designed from solid wires on the one hand and hollow wires on the other hand have not established themselves. -This is where the invention applies.

[0010] The object of the invention is to create an overhead line cable for high-voltage overhead lines of the type described above, in which not only are corona discharges avoided or reduced, but which can also be easily manufactured with high stability and are simple to install (route).

[0011] To achieve this object, the invention teaches an overhead line cable for high-voltage overhead power lines with at least one metallic core wire and a plurality of wire layers arranged (concentrically) around the core wire (layer stranded), wherein at least one outer wire layer as a metallic wire layer consists exclusively of metallic wires and wherein a plurality of the inner wire layers arranged between the core wire and the outer wire layer are mixed wire layers, which each consist of both metallic wires and non-metallic wires, characterized in that the non-metallic wires are placeholders, without a conductor function and without bearing any tensile forces, and are stranded together with the cable.

[0012] Particularly preferably, all inner wire layers between an outer metallic wire layer and the metallic core wire are designed as mixed wire layers. Optionally however, it is also within the scope of the invention that, for example, a plurality of outer wire layers are designed as metallic wire layers, that is to say, the outermost wire layer together with one or more wire layers directly underneath it.

[0013] Particularly preferably, the non-metallic wires of the mixed wire layers are designed as plastic wires. In this way, a reduction of the weight is achieved compared to metal wires. The weight can be reduced particularly efficiently if the non-metallic wires are designed as hollow wires, preferably as plastic hollow wires, which can also be known as "plastic microtubes". Metallic wires means wires that are manufactured from metal.

[0014] The starting point of the invention is the fact mentioned at the very beginning, that corona discharges can be reduced by increasing the cable diameter. According to the invention, the cavity of the generally known hollow cables is divided into a plurality of individual cross-sections, which are formed by the non-metallic wires, particularly preferably by the hollow wires. These non-metallic wires, which are particularly preferably designed as hollow wires and preferably as plastic hollow wires, are only used as placeholders, and as placeholders they are therefore stranded together with the cable in the course of the manufacturing process, but without any conductor function and without bearing any tensile forces. It has been shown that these placeholders, which are stranded together with the cabie during the manufacturing process no longer have any effect at all in operation, once they are installed. Apart from the fact that they have no conductor function, they do not need to perform any mechanical correction (bearing tensiie forces). The finished stranded overhead line cable is stable and functional after completed installation even without these placeholders, so that the "fate" of the placeholders after installation plays no role either. This means that piacehoider wires which subsequently rot away can also be used, so that e.g. biodegradable plastics can be used. After the cable stranding and suspension (installation of the cable) they no longer have any function. They also do not accommodate any optical fibres or similar components, i.e. in the case of hollow wires their interior remains empty (during the stranding). These are unfiiied hoiiow wires.

[0015] The cable according to the invention can also be easily installed, and consequently easily routed. In contrast to conventional hollow cables, no special clamping fixtures and equipment are required for the installation, rather the cables can be laid with conventional standard fittings and equipment.

[0016] According to the invention it is provided that on the one hand, the core wire is a metallic conductor and on the other hand the outer wire layer consists of metallic conductors. The layers in between can be designed as mixed wire layers, with a correspondingly high proportion of placeholder wires, so that the cable cross-section is increased as much as possible to support an appropriate transmission power. In accordance with the invention therefore it is not only important that solid wires and hollow wires be combined, but the combination of the described measures is a central feature. The metallic core wire guarantees a high degree of stability of the cable and the metallic outer layer leads to a high level of functionality in its application.

[0017] In the mixed wire layers, both the metallic wires and the non-metallic wires (placeholders) are each preferably arranged alternately next to each other, so that pairs of non-metallic wires are arranged on both sides of a metallic wire, and vice versa. Alternatively, it is also within the scope of the invention, however, to sort the mixed wire layers in other ways, so that in one layer, e.g. one metallic wire is followed by a number of non-metallic wires, or also a number of metallic wires are followed by a number of non-metallic wires, or a number of metallic wires are each followed by a non-metallic wire.

[0018] In addition, it is advantageous if all wires of a wire layer have (substantially) identical outer diameters. This also applies to the intermediate layers, in which all metallic wires and all non-metallic wires (placeholder wires) then have a (substantially) identical outer diameter. This means that the cable is easy to produce, and that after installation the placeholders no longer actually have to perform any function. In principle, it is within the scope of the invention that all wire layers are then produced from wires having substantially the same diameter. Alternatively, the individual layers can be formed from wires with different diameters, however, that is to say, a wire layer with wires of the same diameter can be followed by a wire layer with wires of another diameter, the diameter again preferably being identical within each wire layer.

[0019] The metallic wires are preferably manufactured from aluminium or an aluminium alloy. It is also within the scope of the invention however, to manufacture the metallic wires from other metals or alloys or types of sintering.

[0020] Hereafter the invention will be described in more detail by reference to a drawing showing a single exemplary embodiment.

[0021] The single figure shows an overhead line cable according to the invention in cross-section.

[0022] In the figure, an overhead line cable for high-voltage overhead lines is shown, which in its basic structure comprises a metallic core wire 1 and a plurality of wire layers 2, 4 arranged concentrically around the core wire.

[0023] The outer wire layer 2, being a metallic wire layer 2, is manufactured exclusively from metallic wires 3.

[0024] The inner wire layers 4 arranged between the core wire 1 and the outer wire layer 2 are designed as mixed wire layers 4, which each consist both of metallic wires 5 and non-metallic wires 6.

[0025] The non-metallic wires 6 in the exemplary embodiment are designed as plastic hollow wires and consequently as plastic microtubes. They are merely placeholders in the course of manufacturing, and thus lead to an increased cable cross-section for the same transmission performance. The important point here is the fact that the core wire 1 and the outer wire layer 2 consist of metallic conductor wires.

[0026] In the exemplary embodiment shown, all wires 1, 3, 5, 6 are designed with the same outer diameter, that is to say, that the placeholder wires 6 have substantially the same outer diameter as the conducting wires 1, 3, 5. It is particularly important here that the wires of a single (concentric) wire layer and in particular also the mixed wire layers, each consist of wires with identical, or substantially identical, outer diameter, which means that the outer diameter within a wire layer should be substantially the same. In principle, the possibility exists of combining a plurality of wire layers together, which while each being formed from wires with the same outer diameter, can still vary in outer diameter from layer to layer. Such an embodiment is not shown.

Claims (6)

An air line cable for high voltage air lines with at least one metallic core wire (1) and several wire layers (2, 4) arranged around the core wire (1), at least the outer wire layer (2) as a metallic wire layer (2) consists of metallic threads (3) and wherein several of the inner thread layers (4) arranged between the core thread (1) and the outer thread layer (2), each of which mixed thread layers (4) each consist partly of metallic threads (5) and partly non-metallic wires (6), characterized in that the non-metallic wires (6) are twisted together with the cable as place holders without wiring and without carrying any traction. Air conduit cable according to claim 1, characterized in that the non-metallic wires (6) of the mixed wire layers (4) are formed as plastic wires. Air conduit cable according to claim 1 or 2, characterized in that the non-metallic wires (6) are formed as hollow wires, preferably as plastic wires. Air conduit cable according to one of claims 1 to 3, characterized in that the metallic wires (5) and the non-metallic wires (6) in the mixed wire layers (4) are arranged alternately side by side. Air conduit cable according to one of claims 1 to 4, characterized in that all metallic wires (5) and non-metallic wires (6) of an intermediate layer (4) have the same outer diameter. An air line cable according to one of claims 1 to 5, characterized in that the metallic wires are made of aluminum or an aluminum alloy.