GB2329764A

GB2329764A - Vibration damped overhead cable

Info

Publication number: GB2329764A
Application number: GB9819360A
Authority: GB
Inventors: Antero Hinkkuri; Petri Tuomainen
Original assignee: NK Cables Oy
Current assignee: Draka NK Cables Oy
Priority date: 1997-09-05
Filing date: 1998-09-04
Publication date: 1999-03-31
Anticipated expiration: 2018-09-04
Also published as: SE9802999L; NO984097L; GB2329764B; SE9802999D0; FI973614A; FI973614A0; FI104862B; GB9819360D0; NO984097D0

Abstract

A conductor or a cord (1) for an overhead line or the like comprises at least one cam part (13) formed on its surface to attenuate conductor or cord vibration caused by a turbulence formation due to a cross-wind. In order to improve fastening the cam part (13) is flexible. The cam part (13) may have an optical element (6) embedded in it.

Description

CONDUCTOR OR CORD FOR OVERHEAD LINE OR EQUIVALENT The invention relates to a conductor or a cord for an overhead line or equivalent comprising at least one cam part formed on the surface of the conductor or cord to attenuate conductor or cord vibration caused by a turbulence formation due to a cross-wind.

Conductor or cord vibration occurs on nearly all overhead lines in unfavolirable circumstances. The phenomenon can occur in connection with various conductors, for example coated conductors, bare conductors, partly coated conductors and overhead cables and furthermore in connection with various cords, for example lightning cords and stay wires. In this situation the conductor or the cord is subjected to a fairly weak even wind. This cross-wind creates a small turbulence behind the conductor or the cord causing forces in the vertical direction of the conductor or the cord. When the frequency of the forces approaches the natural frequency of the span, the conductor or cord vibration is locked at this frequency. The vibration can cause conductor or cord threads to break at bindings even years after installation and may thus present a potential problem.

Previously it has been known to arrange, for example on the conductor surface, a cam part that winds on the surface in a spiral or wavy manner, the cam part preventing turbulence to be created evenly behind the conductor, whereby the creation of harmful vibration is also prevented. The winding cam part described above is formed on the conductor surface, for example, at the extruding stage of the insulation procedure of the coated conductor.

Such a solution is described, for example, in the Finnish patent application 834396.

A drawback of the prior art described above is, for example, that a coated overhead line is attached to an insulator which can be, for example, a pin insulator or a supporting insulator with bonds that can be of prestressed metal or plastic or made of aluminium thread. If the surface of the coated overhead line comprises a cam part or cam parts, the surface area touching the coated overhead line decreases compared with such an overhead line that does not comprise a cam part or cam parts. Consequently the fastening of a conductor or cord provided with cam parts to an insulator or to another corresponding fastening point is weaker than the fastening of such{? conductor or cord that does not comprise cam parts. As a result of a weake5rfastening the conductor or the cord may move in the longitudinal direction of the conductor or the cord and even slip from the bond if the conductor, for example, breaks from a span close by.

An object of the invention is to provide a conductor or a cord by which prior art drawbacks can be eliminated. This is achieved with the conductor or the cord of the invention characterized in that a cam part is made flexible.

The solution of the invention has above all the advantage that the touching surface area between a fastening means, such as a fastening bond, and a conductor or a cord can be increased by means of the invention and thus increase, for example, the strength of the fastening of an overhead line or an insulator. The solution of the invention is furthermore simple and it can be applied for very different manufacturing processes, i.e. the manufacturing process of cam parts can preferably be arranged to the manufacturing process of each conductor or cord.

In the following the invention will be described in greater detail by means of the preferred embodiments in the accompanying drawings, in which Figure 1 is a schematic view seen in the direction of the conductor showing a preferred embodiment of the invention, Figure 2 is a schematic view showing a second preferred embodiment of the invention in perspective, Figure 3 shows a detail of the embodiment in Figure 2 in a larger scale, Figure 4 is a partial cross-sectional view seen in the axial direction of the conductor showing a third preferred embodiment of the invention, Figure 5 is a partial cross-sectional view seen in the axial direction of the conductor showing a fourth preferred embodiment of the invention, and Figure 6 is a schematic view showing a fastening of the embodiments in Figures 2-6 to an insulator.

Figure 1 shows a preferred embodiment of the invention in principle.

The preferred embodiment in Figure 1 is a coated overhead line. Reference number 1 indicates a conductor and reference number 2 a coating of the conductor. Reference number 3 indicates cam parts in Figure 1. Reference number 4 in the Figure, in turn, indicates a bond by which a line can be attached to an insulator. The insulator is not indicated in Figure 1.

In accordance with the essential idea of the invention the cam parts 3 are made flexible. The idea is that by making the cam parts 3 flexible the surface area of the bond 4 and the conductor touching one another can be increased, thus increasing the strength of the fastening between the insulator and the conductor. The surface-area of the bond 4 and the conductor increases because the cam part bends at the bond 4 as shown in Figure 1. In Figure 1 arrow 5 indicates the flexible cam part in principle.

The cam parts 3 can be made at the extruding stage of the insulation procedure. The cam part 3 can be made with a different extruder than the actual coating. It is essential that the cam part is made thin in relation to the height of the cam part, whereby preferable properties are achieved. The cam part can be made of the same material as the actual coating. However, it is preferable to use a different material than the one used in the conductor coating for making the cam part, since then a more elastic material than the actual coating material or a material, whose friction coefficient is better than the friction coefficient of the actual coating material, can be used as the cam part material. If the cam part material is extruded onto the actual conductor coating as a compact skin layer, the UV shielding can be restricted to the skin layer only. Then there is no need to use carbon black decreasing the voltage endurance of the coating in the coating of the conductor.

The cam parts 3 can be formed either as continuous parts extending over the entire length of the conductor or as longitudinal and noncontinuous parts in the longitudinal direction of the conductor. Longitudinal cavities or cross directional holes can also be formed in the cam parts 3.

Figures 2 and 3 show a second preferred embodiment of the conductor of the invention. Reference number 1 indicates the conductor in Figures 2 and 3 and reference number 2 indicates the coating. The essential feature of the preferred embodiment in Figures 2 and 3 is that an optical element 6 is placed in a cam part 13.

Figures 4 and 5 show additional applications of the embodiment according to Figures 2 and 3. The embodiment in Figure 4 deviates from the one in Figures 2 and 3 in that a cam part 23 in the embodiment in Figure 4 is made thin at the base. Arrow 7 indicates the thin point at the base of the cam part in Figure 4. In Figure 4 arrows and dotted lines indicate the turning motion of the cam part 23 which is facilitated on account of the thin base of the cam part.

Figure 5 shows another alternative to thin the base of the cam part. Arrow 8 indicates how the base of a cam part 33 is narrowed. In Figure 5 arrows and dotted lines also indicate the turning motion of the cam part as in Figure 4. It should be noted that in addition to the vibration attenuation of the conductor the cam part can provide an optical element with an ability to move both in the radial and circumferential direction. Said ability is obtained particularly by the embodiments in Figures 4 and 5. On account of said abilities the increase in conductor length caused by a conductor creep does not cause strain for optical fibres but the increase in conductor length is compensated by moving the optical element closer to the conductor in the radial direction. Due to the cam part the optical element is easy to remove from the coated overhead line by cutting the cam part off. In this respect the cam part with a thin base is very advantageous. Figure 6 shows such a situation where the embodiment according to Figure 4 is shown by means of a bond 4 attached to an insulator 9.

Cutting the cam part is an easier operation than1 for example, raising an optical element from the middle of the conductor. Due to the cam part the optical element can during the manufacturing stage be attached to a cable as a part.

A separate fastening work stage of the optical part is therefore not needed.

Thinning the base of the cam part can naturally be used also without an optical element, i.e. the bases of the cam parts in the embodiment in Figure 1 can naturally be thinned too, in which case it is very easy to remove the cam parts as shown above.

The above described embodiments are not intended to restrict the invention, but the invention can freely be modified within the scope of the claims. It is thus clear that all details of the conductor or the cord of the invention need not be exactly as shown in the Figures, but other kinds of solutions are also possible. A coated overhead line is used to describe the invention in the Figure. However, the invention is not restricted to a coated overhead line but can be applied to all structures, concerning said wind load, such as bare overhead lines, partly coated overhead lines, overhead cables, cords, for example lightning cords, stay wires etc. The invention is not either restricted to a particular type of conductor or cable but can be applied in connection with energy transfer cables, telecables, optical cables, hybrid cables etc. The cam parts can be manufactured by using any technique. For example, during the twisting stage an element, which may also be an optical element forming the cam part on the surface of the cable etc., can be arranged inside the cable.

The optical element can also be any known solution.

Claims

CLAIMS A conductor or a cord for an overhead line or equivalent comprising at least one cam part (3, 13,23, 33) formed on the surface of the conductor or cord to attenuate conductor or cord vibration caused by a turbulence formation due to a cross-wind, c h a r a c t e r i z e d in that the cam part (3, 13, 23, 33) is made flexible.
2. A conductor or a cord as claimed in claim 1, character i z e d in that the cam part (3, 13, 23, 33) is formed as a continuous part ex- tending over the length of the conductor or the cord.
3. A conductor or a cord as claimed in claim 1, characteri z e d in that the cam part (3, 13, 23, 33) is formed as a non-continuous part in the longitudinal direction of the conductor or the cord.
4. A conductor or a cord as claimed in any one of the preceding claims 1-3, c h a r a c t e r i z e d in that longitudinal cavities are formed in the cam part (3, 13, 23, 33).
5. A conductor or a cord as claimed in any one of the preceding claims 1-3, c h a r a c te r i z e d in that cross directional holes are formed in the cam part (3,13, 23, 33).
6. A conductor or a cord as claimed in any one of the preceding claims 1-5, c h a r a c t e r i z e d in that the cross-section of the cam part (23, 33) is made thin at the base.
7. A conductor or a cord as claimed in any one of the preceding claims 1-6, c h a r a C t e r i z e d in that an optical element (6) is arranged to the cam part (13, 23, 33).