EP1217634A1

EP1217634A1 - A high-voltage cable with at least one optical-fibre cable

Info

Publication number: EP1217634A1
Application number: EP00204617A
Authority: EP
Inventors: Allan Jensen; Peter A. Riisager
Original assignee: NKT Cables AS
Current assignee: NKT Cables AS
Priority date: 2000-12-19
Filing date: 2000-12-19
Publication date: 2002-06-26

Abstract

The present invention relates to a high-voltage power cable for submarine power transmission comprising one or more cable cores, each core comprising a conductor with an insulation system around the conductor, a sheath encompassing the cable cores, a tensile armour comprising a plurality of helical tensile wires wound around the sheath, at least one optical-fibre cable, and an outer protective cover jacketing the tensile armour, wherein the at least one optical-fibre cable is peripherally positioned in the tensile armour between two tensile wires thereof and provided with a protecting means. By a cable according to the invention, the optical-fibre cable is integrated in the cable structure in a particularly advantageous manner, so that it is ensured that the optical-fibre cable is easily accessible whilst being sufficiently well-protected.

Description

The present invention relates to a high-voltage power cable for submarine power transmission comprising one or more cable cores, each core comprising a conductor with an insulation system around the conductor, a sheath encompassing the cable cores, a tensile armour comprising a plurality of helical tensile wires wound around the sheath, at least one optical-fibre cable, and an outer protective cover jacketing the tensile armour.
By transmission of high-voltage electric power over long distances, it is desirable to be able to transmit communication data as well. For this reason, optical-fibre conductors are being provided in association with the power cable. However, the optical-fibre conductors are fragile and may easily be damaged by mechanical impact.
From FR-A-2 769 748, a power cable is known, in which the sheath is made up by reinforcement rods that are shaped to form a close circular fitting around the concentric wire conductor. Spaces are provided between some of the reinforcement rods. In these spaces, optical-fibre conductors are provided. This cable design is expensive to produce and offers only limited protection to the optical fibres against mechanical impact. Moreover, this incorporation of optical-fibre transmission cables into a power cable is only suitable for single electric conductor cables.
From DE-C-195 08 888, a flexible power cable with multiple electric conductors is known. Inside the cable, the optical fibres are provided in a metal tube in the space between the electrical conductors and the surrounding sheath. This offers protection to the optical-fibre cable as well as the electrical conductors. However, it is extremely difficult to gain access to the optical fibres for repair and maintenance inside this cable.
It is therefore the object of the present invention to provide a power cable for high-voltage electrical transmission with an optical fibre cable that is well-protected against mechanical impact and at the same time easily accessible for service and maintenance.
This object is achieved by a high-voltage cable of the initially mentioned kind, wherein the at least one optical-fibre cable is peripherally positioned in the tensile armour between two tensile wires thereof and provided with a protecting means.
By a cable according to the invention, the optical-fibre cable is integrated in the cable structure in a particularly advantageous manner, so that it is ensured that the optical-fibre cable is easily accessible whilst being sufficiently well-protected. The cable is relatively simple in its design as the optical-fibre cable is provided in the tensile armour and may merely be a replacement of a tensile wire in the armour. The optical-fibre cable comprises a number of optical fibres arranged in a tubular casing. In association with the optical-fibre cable, protecting means are provided for protecting the optical-fibre cable against mechanical impact.
In the preferred embodiment of the invention, the protecting means includes a protective strip positioned on the outside of the tensile armour adjacent to the optical-fibre cable in such a way that the optical-fibre cable and at least part of the neighbouring tensile wires on each side of the optical-fibre cable are covered. Hereby, a particularly simple embodiment of the protecting means is provided offering a good protection of the optical-fibre cable against mechanical impact as well as being relatively easy to apply during the manufacturing process. The protective strip is provided with a lay angle identical with that of the tensile wires and the optical-fibre cable or cables, so that it follows the optical cable along and around the tensile armour immediately inside the outer protection of cable.
In a first embodiment of the invention, the protective strip is provided on the inside of outermost layer of the tensile armour shaped with an outwardly protruding groove in which the optical-fibre cable is provided. Hereby, the protective strip is held in place by the two neighbouring tensile wires due to the serpentine cross-sectional shape.
Alternatively, the protective strip is a flat band helically disposed with the same lay angle as the tensile wires on the outer perimeter of the tensile armour. This solution is particularly simple and specially suitable for the manufacturing process as the flat band easily bends around the cable in a helical shape. Moreover, it is a particularly suitable solution for the manufacture of long cable lengths.
In a second embodiment of the invention, the protecting means includes a Bowden cable accommodating the optical-fibre cable. By replacing a tensile wire of the tensile armour with a Bowden cable, i.e. a tubular structure made up by a closely helically wound wire stand, a flexible protection may be provided against mechanical damage to the optical-fibre cable, either as a supplement or as an alternative to the solution of the first embodiment.
As another measure for providing protection against mechanical impact, the diameter of the optical-fibre cable is equal to or smaller than the diameter of the neighbouring tensile wires of the armour.
A power cable according to the invention may comprise either a single core or a multiple of cable cores. The power cable may be a DC or an AC high-voltage power cable, either a mass-impregnated, flat-type oil-filled or an XLPE cable or other types.
In a particular embodiment of the invention, the power cable includes two or more optical-fibre cables each associated with protecting means, wherein the protecting means is provided with individual identification means. The identification means may include colour codes, printing, embossing and/or other kinds of individualisation by providing the protecting means with a predetermined difference in shape and/or a predetermined difference in diameter or width of the shield.
Hereby, each of the optical-fibre cables is easy to identify at each end of the cable, whereby it is ensured that a correct connection of the cable is being performed.
The invention will be described in detail below with reference to the accompanying drawings, in which

Figs. 1 to 3: are schematic cross-section views of three embodiments of a circular cable according to the invention with a multiple of conductors,
figs. 4 to 6: are schematic cross-section views of three embodiments of a cable according to the invention with a single conductor,
figs. 7 to 9: are schematic cross-section views of three embodiments of a flat-type cable according to the invention,
figs. 10 to 12: are detailed views of three embodiments of the protecting means according to an embodiment of the invention, and
fig. 13: is a view of an optical-fibre cable with protecting means according to another embodiment.

In figures 1 to 9, different types of cables are shown. In the figures, the cable comprises one or more cable cores 1 arranged in a circular formation, as shown in figs. 1 to 3, or next to each other to form a flat configuration power cable, as shown in figs. 7 to 9. The cable cores comprise a conductor which is provided with an insulation system (not shown). The cable cores 1 are encompassed by a lead sheath 2. The sheath 2 is protected by a tensile armour 3 jacketing the sheath 2. Finally, the tensile armour 3 is coated by an outer sheath (not shown) which protects the cable and prevents water from penetrating the cable.
The tensile armour 3 is made up by a number of helically wound tension wires 4. In this armour 3, at least one of the tensile wires 4 is replaced by an optical fibre cable 5. Hereby, the optical-fibre cable 5 is easily accessible for maintenance and repair. In order to protect the optical cable 5 from mechanical impact, a protecting means 6 is provided. The protecting means 6 may be designed in different ways.
In figures 1, 4 and 7, the protecting means 6 is not shown. In this embodiment of the protecting means 6 (not shown in these figures) for the optical cable 5, protection may be provided by a reduced diameter of the optical cable 5 relative to the tensile wires 4, so that an impact will be absorbed by the tensile wires 4 instead of the fragile optical cable 5. Another solution could be that the optical cable 5 is provided with a Bowden cable 63 (see fig. 12) in order to provide the required impact strength.
In figures 2, 3, 5, 6, 8 and 9, the optical cable 5 is shielded by a protective strip 6 positioned on the outside perimeter of the tensile armour 3. The strip 6 is laid around the tensile armour 3 in the same lay angle as the tensile wires 4 and the optical cable 5. The strip 6 is positioned on the perimeter of the tensile armour 3 so that it completely covers the optical cable 5 and two neighbouring tensile wires 4. Hereby, a particularly simple protection of the optical cable 5 is obtained. The protective strip is generally a flat strip of metal or another suitable material, making the strip 6 is easy to bend and to wind around the cable. In particular, by a flat cable configuration, a flat protective strip is particularly suitable due to the geometry of the cable.
In figures 3, 5 and, 9 the tensile armour 3 is made up by two layers of helically counter-wound wires 4. The optical cable 5 is arranged in the outermost layer. One or more optical cables 5 could alternatively be arranged in another layer of tensile wires.
Figs. 10 and 11 show two partial cross-section views of a tensile armour 3 with two embodiments of the protective metal strip 6. In fig. 10, the serpentine-shaped strip 61 is held in place by the neighbouring tensile wires 41, 42 on each side of the optical cable 5. In fig. 11, a protective strip 62 with a slightly different shape is shown. The bent strip 63 is held in place by at least the neighbouring tensile wires 41, 42 and the adjacent tensile wires 4 in the armour 3.
In figure 12, a partial cross-section view of a tensile armour 3 with flat protective strip 60 is shown. The strip 60 is positioned on the outside of the tensile armour 3 covering the optical cable 5 and at least the neighbouring the tensile wires 41, 42. The strip 60 is helically wound around the tensile armour 3 with the same lay angle as the optical cable 5 and the tensile wires 4. Hereby, the strip 60 is secured to the tensile armour in a simple manner.
In fig. 13 a cross-section view of another embodiment of the protecting means is shown. The optical fibre cable 5 is provided with a Bowden cable 63 around the optical cable 5. The Bowden cable 63 is a coiled steel wire that offers the optical cable good protection against mechanical impacts. The optical fibre cable 5 inserted in the Bowden cable 63 is then wound together with the tensile wires 4 around the sheath 2.

Claims

A high-voltage power cable for submarine power transmission comprising:

one or more cable cores, each core comprising a conductor with an insulation system around the conductor,

a sheath encompassing the cable cores,

a tensile armour comprising a plurality of helical tensile wires wound around the sheath,

at least one optical-fibre cable, and

an outer protective cover jacketing the tensile armour,

characterised in that

the at least one optical-fibre cable is peripherally positioned in the tensile armour between two tensile wires thereof and provided with a protecting means.
A cable according to claim 1, wherein the protecting means includes a protective strip positioned on the outside of the tensile armour adjacent to the optical-fibre cable in such a way that the optical-fibre cable and at least part of the neighbouring tensile wires on each side of the optical-fibre cable are covered.
A cable according to claim 1 or 2, wherein the protective strip is provided with the same lay angle as the tensile wires and the optical-fibre cable or cables.
A cable according to any of claims 1 to 3, wherein the protective strip is provided on the inside of outermost layer of the tensile armour shaped with an outwardly protruding groove in which the optical-fibre cable is provided.
A cable according to any of claims 1 to 3, wherein the protective strip is a flat band helically disposed on the outer perimeter of the tensile armour.
A cable according to claim 1, wherein the protecting means includes a Bowden cable accommodating the optical fibre cable.
A cable according to any of the preceding claims, wherein the diameter of the optical-fibre cable is equal to or smaller than the diameter of the neighbouring tensile wires of the armour.
A cable according to any of the preceding claims, wherein the power cable comprises a multiple of cable cores.
A cable according to claim 8, wherein the power cable includes two or more cable cores in a flat cable configuration.
A cable according to claim 8 or 9, wherein the power cable is provided with a filling material between the cable cores.
A cable according to claim 10, wherein the power cable is an oil-filled cable.
A cable according to any of the preceding claims, wherein the optical-fibre cable comprises a number of optical fibres arranged in a protective tubular casing.
A cable according to any of the preceding claims, wherein the power cable includes two or more optical-fibre cables each associated with protecting means, wherein the protecting means is provided with individual identification means.
A cable according to claim 13, wherein the identification means includes colour codes, printing, embossing and/or individualisation by providing the protecting means with a predetermined difference in shape and/or a predetermined difference in diameter or width of the shield.