EP0988673A1

EP0988673A1 - Overhead line conductor

Info

Publication number: EP0988673A1
Application number: EP98924344A
Authority: EP
Inventors: Antero Hinkkuri; Petri Tuomainen
Original assignee: NK Cables Oy
Current assignee: Draka NK Cables Oy
Priority date: 1997-06-03
Filing date: 1998-06-02
Publication date: 2000-03-29
Also published as: FI105365B; FI972355A0; WO1998058431A1; FI972355A; AU7657098A

Abstract

The invention relates to an overhead line conductor, particularly to a sheathed conductor (1) comprising at least one ridge part (5) on the surface of the conductor for damping conductor (1) vibration generated by formation of turbulence caused by side wind. To enable a quicker manufacturing process, the ridge part (5) is a part of varying height in the longitudinal direction of the conductor (1).

Description

1

OVERHEAD LINE CONDUCTOR

The invention relates to an overhead line conductor, particularly to a sheathed conductor comprising at least one ridge part on the surface of the conductor for damping conductor vibration generated by formation of turbu- lence caused by side wind.

Vibration of a conductor may occur on almost every overhead line under unfavourable conditions. A steady, scant wind is thus directed against the conductor. This side wind generates weak turbulence behind the conductor, which generates forces parallel with the vertical plane of the conductor. When the frequency of these forces approaches the natural frequency of the span, the conductor vibration is locked at this frequency. The vibration can cause the wires of the conductor to break at binding points as late as years after the installation and may thus prove to be a potential problem.

It is previously known to arrange on the surface of a conductor a ridge part winding around the surface of the conductor in a spiral or wave-like manner, by means of which the formation of turbulence evenly behind the conductor has been inhibited, whereby the generation of harmful vibration has also been inhibited. The above ridge part is formed on the surface of the conductor in the extrusion stage of the insulation step. A solution of this kind is disclosed in Finnish Patent Application 834 396.

However, a drawback of the previously known solutions has been that the formation of the ridge part has slowed down the rate of the insulation step, whereby the economic efficiency of the manufacturing process is not as high as possible. It is an object of the invention to provide a conductor wherewith the drawbacks of the prior art technique can be eliminated. This object is achieved by the conductor of the invention, which is characterized in that the ridge part is a part of varying height in the longitudinal direction of the conductor.

A primary advantage of the invention is that the structure can be manufactured in such a manner that the production rate does not considerably deviate from the production rate of a conductor without ridge parts. A further advantage of the invention is its simplicity which allows the invention to be advantageously put to use. Another advantage of the invention is its functionality ^~ during installation and, in addition, the fact that the increase in cross-section provided by the straight ridge parts is smaller than in connection with the spi- 2 ral, whereby the wind load of the conductor of the invention is lower than in connection with the previous solutions when the wind is strong.

The invention will be described in closer detail in the following by means of an example of a preferred embodiment disclosed in the accompa- nying drawing, in which

Figure 1 shows a schematic perspective view of a first embodiment of the invention,

Figure 2 shows a schematic view of the shape of the ridge part of the embodiment in accordance with Figure 1 , and Figure 3 shows a schematic view of the shape and arrangement of the ridge part of a second embodiment of the invention.

Figure 1 schematically shows an embodiment of the conductor of the invention. The conductor is generally referred to by reference number 1. In the example of Figure 1 the conducting part of the conductor comprises a structure 3 stranded from wires 2. It will be obvious that the structure 3 forming the conducting part can also be provided in some other manner, for example from one wire, etc. The structure 3 shown in Figure 1 is thus to be understood to be a conducting structure in general and not so much a particular configuration. In Figure 1 , reference number 4 denotes a sheathing layer which can be of plastics material, for example.

The ridge parts that have been arranged to damp conductor 1 vibration generated by formation of turbulence caused by side wind are marked in Figure 1 by means of reference number 5.

In accordance with the essential idea of the invention, each ridge part 5 is a part of varying height in the longitudinal direction of the conductor 1. The number of the ridge parts 5 can vary as required. There can thus be one or more ridge parts 5. The ridge parts 5 can be parts that are coaxial with the symmetry axis S of the conductor 1 as in the figures. Nothing, however, prevents the ridge parts from being spiral-shaped, if this alternative is found necessary, etc.

The shape of the ridge parts 5 can be freely chosen as required. The shape of the ridge parts can be sinusoidal, angular, irregular, etc. The periodicity of the ridge parts can also be implemented in different ways. The ridge part 5 can be continuous, for example, whereby successive ridges im- mediately follow each other. An application of this kind is shown in Figures 1 and 2. The ridge part 5 can also be partial, whereby between the successive 3 ridges 5a there is a smooth section 5b. An application of this kind is shown in Figure 3. The smooth section 5b can be a section on the level of the surface of the conductor, as in the example of Figure 3, or it can comprise a low, smooth section slightly projecting from the surface of the conductor 1 , etc. If the con- ductor comprises more than one ridge part 5, a mutual phase shift can be arranged between the different ridge parts. A solution of this kind is shown in Figure 3. The ridge parts 5 can be either flexible or rigid ones.

The cross-sectional shape of the ridge parts 5 can be chosen as required. For example, the substantially triangular shape shown in Figure 1 can be given as a preferred embodiment. The height of the ridge parts can also vary in accordance with the dimensions of the conductor. It can be stated here that a ridge part with a maximum height of 1/3 x the outside diameter of the conductor gives an advantageous result. The ridge parts 5 can be made of the same material as the sheathing layer 4. This is not, however, the only al- ternative, since the ridge parts can also be made of a different material than the sheathing layer 4, or they can contain a different material than the sheathing layer. As an example a solution can be given in which the ridge parts are of the material of the sheathing layer, to which material plastic fibre reinforcements have been added to increase the tensile strength of the conductor, and a solution in which the ridge parts are made of a material with better strength properties than the sheathing 4. Optical fibres can also be added to the ridge parts 5 if this kind of solution is felt necessary. The ridge parts 5 can also be parts in a separate surface layer, whereby the surface layer comprising the ridge parts as its parts is arranged on the sheathing layer 4. The surface layer can either be made of the same material as the sheathing layer 4 or of a different material. The ridge parts 5 are preferably made by the same tool as the sheathing layer 4.

The examples of embodiments presented above are by no means intended to restrict the invention, but the invention can be quite freely modified within the scope of the claims. It is thus obvious that the conductor of the invention or its details do not have to be identical to those presented in the figures.

Claims

4 CLAIMS

1. An overhead line conductor, particularly to a sheathed conductor (1) comprising at least one ridge part (5) on the surface of the conductor for damping conductor (1) vibration generated by formation of turbulence caused by side wind, characterized in that the ridge part (5) is a part of varying height in the longitudinal direction of the conductor.

2. A conductor as claimed in claim 1, characterized in that the ridge part (5) is a continuous part in which higher and lower sections immediately follow each other.

3. A conductor as claimed in claim 1, characterized in that the ridge part (5) is a discontinuous part in the longitudinal direction of the conductor (1), comprising a smooth section (5b) between the sequential ridges (5a).

4. A conductor as claimed in claim 3, characterized in that the plain section (5b) is a section which is on the level of the surface of the conductor (1).

5. A conductor as claimed in any one of claims 1 to 4, character i z e d in that a mutual phase shift is arranged between the different ridge parts (5) of the conductor (1 ).

6. A conductor as claimed in any one of claims 1 to 5, character i z e d in that the ridge parts (5) are parts that are coaxial with the symmetry axis (S) of the conductor.

7. A conductor as claimed in any one of claims 1 to6, characterized in that the ridge parts (5) are flexible parts.