SUBMARINE POWER CABLE

Abstract

A submarine power cable is provided having stranded conductor(s) and an insulation system, each individual stranded conductor, at given intervals, being compressed across an area to form a plurality of watertight partitions along a length of the of the submarine power cable. A method provides a plurality of watertight partitions along a length of the submarine power cable. The method includes, at a given point, arranging a compression tool around an outer circumference of the stranded conductor, using the compression tool to compress the stranded conductor, releasing the compression tool from the stranded conductor, and repeating the compression at a number of different points and using the compression tool to compress the stranded conductor at each of these points, thereby forming a plurality of watertight partitions along the length of the submarine power cable.

Claims

1. A submarine power cable comprising: one or more stranded conductors; and an insulation system surrounding each stranded conductor, wherein each individual stranded conductor, at given intervals of the submarine power cable, is compressed across an area to form a plurality of watertight partitions along a length of the submarine power cable.

2. The submarine power cable according to claim 1, wherein the insulation system comprises an inner semiconducting layer, a solid insulation layer and an outer semiconducting layer.

3. The submarine power cable according to claim 1, wherein the stranded conductor comprises a number of metallic wires, the metallic wires being bundled or wrapped together to form a bunch stranding, a concentric stranding, an unilay stranding or a rope lay stranding.

4. The submarine power cable according to claim 1, wherein the area which is compressed has a length between 1-1500 mm.

5. The submarine power cable according to claim 1, wherein each stranded conductor has a circular, triangular or polygonal cross-section.

6. The submarine power cable according to claim 1, wherein the metallic wires are made from aluminum, copper, other metals or a combination thereof.

7. The submarine power cable according to claim 1, wherein the stranded conductor in the area which is compressed has a substantially solid configuration.

8. The submarine power cable according to claim 1, wherein the stranded conductor is continuous along the length of the submarine power cable.

9. The submarine power cable according to claim 1, wherein the stranded conductor is a clean conductor.

10. The submarine cable according to claim 1, wherein the stranded conductor is filled with a filling compound over an entire length or in sections of the submarine cable.

11. A method for providing a plurality of watertight partitions along a length of a submarine power cable according to claim 1, wherein said method comprises the following step: at a given point of the length of the submarine power cable, arranging a compression tool around an outer circumference of the stranded conductor, using the compression tool to compress the stranded conductor across an area, releasing the compression tool from the stranded conductor, repeating the arranging of the compression tool around the outer circumference of the stranded conductor at a number of different points and using the compression tool to compress the stranded conductor at each of these points, thereby forming a plurality of watertight partitions along the length of the submarine power cable.

12. The method according to claim 11, wherein the method further comprises the following step: compressing the stranded conductor to a substantially solid configuration.

13. The method according to claim 11, wherein the method further comprises the following step: performing the compression in several step, in order to obtain a desired length of the watertight partition.

14. The method according to claim 11, wherein the method further comprises, before the compression of the stranded conductor the following step: arranging a thin sleeve or casing over an area which is to be compressed, compressing both the thin sleeve or casing and the stranded conductor, in order to provide the stranded conductor with a substantially equal diameter over the length of the stranded conductor.

15. The submarine power cable according to claim 4, wherein the area which is compressed has a length between 10-1000 mm.

16. The submarine power cable according to claim 4, wherein the area which is compressed has a length between 15-850 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Other advantages and characteristic features of the present invention will be seen clearly from the following detailed description, the appended figures and the following claims, wherein:

[0047] FIGS. 1A-1C illustrate perspective and cross-sectional views of a stranded conductor according to the present invention,

[0048] FIG. 2 illustrates use of a compression tool on a stranded conductor according to FIG. 1,

[0049] FIG. 3 illustrates removal of the compression tool according to FIG. 2 and

[0050] FIG. 4 illustrates the stranded conductor according to FIG. 1, where the stranded conductor is provided with a watertight partition.

DETAILED DESCRIPTION

[0051] FIGS. 1A-1C illustrate different embodiments of a stranded conductor 1 of a submersible power cable according to the present invention, where FIG. 1A shows the stranded conductor 1 in a perspective view, while FIGS. 1B-1C show the stranded conductor 1 in a cross-sectional view.

[0052] The stranded conductor 1 comprises a plurality of metallic wires 2, where the metallic wires 2 are bundled or wrapped together to form the stranded conductor 1.

[0053] The plurality of metallic wires 2 of the stranded conductor 1 may be arranged together in a variety of configurations, for instance in a bunch stranding, a concentric stranding, an unilay stranding or a rope lay stranding. A person skilled in the art would know how this can be done, whereby this is not described any further herein.

[0054] It can also be seen from FIGS. 1B and 1C that the metallic wires 2 of the stranded conductor 1 may have different profile or cross-section.

[0055] The plurality of metallic wires 2 are made of aluminium, copper, different alloys or combinations thereof.

[0056] Although the stranded conductor 1 in the embodiment according to FIGS. 1A-1C is shown to have a substantially circular form or cross-section, it should be understood that the stranded conductor 1 may also have other forms, for instance a triangular, square or polygonal cross-section.

[0057] According to the present invention, the submarine power cable comprises at least one clean, stranded conductor 1, meaning that a filling compound such as an elastic, a swellable powder or yarn or the like is not filled in between voids or spaces of the metallic wires 2 in order to provide a watertight conductor over an entire length or sections of the submarine power cable. Instead the stranded conductor 1 is made watertight through a compression, at given intervals, of the stranded conductor.

[0058] Such a compression of the submarine power cable at different intervals, will provide a plurality of watertight partitions along the length of the submarine power cable, whereby an ingress or intrusion of water, will be limited by two adjacent watertight partitions, whereby only the length between these two adjacent watertight partitions can be filled with water and as such, only this part of the submarine power cable would need to be replaced and/or repaired.

[0059] FIG. 2 shows how two matrixes 3 or dies, the matrixes 3 or dies in appropriate ways being connected to a compression tool (not shown) can be used to provide the plurality of watertight partitions 4 along the length of the stranded conductor 1.

[0060] Each matrix 3 or die will have a cut-out 3a or recess facing the stranded conductor 1, when the two matrixes 3 or dies are arranged around the stranded conductor 1, where this cut-out 3 or recess has a corresponding form as the stranded conductor 1. However, the diameter of the matrixes 3 or dies, when placed together, will be somewhat smaller that a diameter of the stranded conductor 1.

[0061] FIG. 2 shows that the stranded conductor 1 has a circular cross-section, whereby the cut-out 3 or recess in each matrix 3 or die will have a form of a semicircle.

[0062] If the stranded conductor 1 has a polygonal form, the cut-out 3 or recess in each will have a shape or form that corresponds to half of the polygonal form of the stranded conductor 1.

[0063] When the two matrixes 3 or dies are arranged over and under the stranded conductor 1, the compression tool is used to compress the two matrixes 3 or dies together, this also resulting in that the stranded conductor 1 is compressed in this area.

[0064] The compression of the stranded conductor 1 will result in that the metallic wires 2 of the stranded conductor 1 are compressed to such a degree that the stranded conductor 1 in this area is made substantially solid, such that water cannot penetrate through the stranded conductor when an insulation system is arranged around the outer circumference of the stranded conductor 1.

[0065] Such an insulation system may, for instance, comprise an inner semiconducting layer arranged around the stranded conductor 1, a solid insulation layer arranged around the inner semiconducting layer and an outer semiconducting layer arranged around the solid insulation layer.

[0066] The matrixes 3 or dies may have two or four compression directions.

[0067] When the compression is finished, as seen in FIG. 3, the compression tool is used to release the two matrixes 3 or dies from each other and the stranded conductor 1. A watertight partition 4 is then provided in the stranded conductor 1.

[0068] How long a length of such a watertight partition 4 is, will depend on the configuration of the submarine power cable, the area of application of the submarine cable or the like.

[0069] For instance, if the submarine power cable according to the present invention is to be used at large water depths, exposing the cable for large pressures, or the submarine power cable is to be used in harsh environment and thereby subjected to large loads, the length of the watertight partition 4 may be longer that if the submarine power cable is subjected to smaller loads.

[0070] Depending on the configuration of the submarine power cable, the area of application of the submarine power cable (i.e. which water depth it is to be used on the pressure or load it is subjected to) etc. the length of the area which is compressed may vary.

[0071] Furthermore, the plurality of watertight partitions 4 that are provided over the length of the stranded conductor 1 may have the same length, but it could also be envisaged that some of the watertight partitions 4 may be provided with a different length.

[0072] If the matrixes 3 or dies used with the compression tool have a length (or width) that is smaller than the intended length of the area which is to be compressed, the compression may be done in several steps. The matrixes 3 or dies will then be arranged around the outer circumference of the stranded conductor 1 and the compression tool is thereafter used to compress a first part of the watertight partition 4, whereafter the matrixes 3 or dies are released and moved in the longitudinal direction of the stranded conductor 1 to compress a subsequent part of the watertight partition 4. This process will be repeated until the desired length of the watertight partition 4 is obtained. Thereafter the same is repeated for each area which is to be compressed in order to provide a watertight partition 4.

[0073] For instance, if the length of a watertight partition 4 is to be 850 mm and the matrixes 3 or dies have a length (or width) that is only 212.5 mm, then the stranded conductor 1 must be compressed four times in order to provide a watertight partition 4 having a length of 850 mm.

[0074] FIG. 4 shows the stranded conductor 1 after the compression process is complete and the compression tools and matrixes 3 or dies are removed.

[0075] As the stranded conductor 1 has been compressed in this area to a substantially solid configuration, the watertight partition 4 will have a smaller diameter than the areas of the stranded conductor 1 which are not compressed.

[0076] It could be envisaged that the stranded conductor 1 also could be provided with a thin sleeve or casing over the area that is to be compressed before the compression of the stranded conductor 1, whereafter both the thin sleeve or casing and the stranded conductor 1 are compressed together by using the compression tool. When the compression is done, the stranded conductor 1 is compressed to a substantially solid configuration, while the thin sleeve or casing will be in level or in line with the stranded conductor 1 which is not compressed, thereby providing a stranded conductor with a substantially equal diameter over the length of the stranded conductor 1.

[0077] Furthermore, for the sake of simplicity, only one watertight partition 4 is shown provided on the stranded conductor 1, but it should be understood that a plurality of such watertight partitions 4 will be provided spaced apart from each other and over the entire length of the stranded conductor 1.

[0078] The invention has now been explained with several non-limiting exemplary embodiments. One skilled in the art will appreciate that a variety of variations and modifications can be made to the submarine power cable and the method for providing a plurality of watertight partitions along a length of a submarine power cable as described within the scope of the invention as defined in the appended claims.