Dynamic submarine power cable with corrugated and smooth metallic water barrier

Abstract

To provide a dynamic submarine power cable which solves or at least mitigates problems of buckling and the like due to high hydrostatic pressure at deep sea and, if a power cable is constantly moving, deformation that may cause stress concentrations reducing the fatigue life of a metallic water barrier.SOLUTION: A dynamic submarine power cable (1) comprises: a conductor (3); an insulation system arranged around the conductor, where the insulation system comprises an inner semiconducting layer (5a) arranged around the conductor, an insulation layer (5b) arranged around the inner semiconducting layer, and an outer semiconducting layer (5c) arranged around the insulation layer; and a metallic water blocking layer (7) arranged around the insulation system. The metallic water blocking layer is formed by a first section, which is a corrugated metallic water blocking layer, and a second section, which is a smooth metallic water blocking layer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates generally to dynamic submarine power cables. [Background technology]

[0002] Dynamic submarine power cables are subject to movement when suspended from a floating structure to the seabed. Such cables therefore typically have a corrugated metallic water barrier in order to provide better fatigue properties to the metallic water barrier. An example of such a solution is disclosed in EP 2 896 053. Summary of the Invention

[0003] Nowadays, dynamic submarine power cables are being considered for use in deep sea installations, for example for water depths of more than 1500m or even more than 2000m. This makes the use of corrugated metal water barriers problematic, since in deep water the hydrostatic pressures are high and may cause buckling of the corrugated metal water barriers. Especially when the power cable is constantly moving, uncontrolled changes to the original design of the metal water barrier, e.g. due to buckling, are undesirable, since deformations may cause stress concentrations and reduce the fatigue life of the metal water barrier.

[0004] In view of the above, it is an object of the present disclosure to provide a dynamic submarine power cable that solves or at least mitigates the problems of the prior art.

[0005] Thus, according to a first aspect of the present disclosure, there is provided a dynamic submarine power cable comprising a conductor; an insulation system disposed about the conductor, the insulation system comprising an inner semi-conductive layer disposed about the conductor, an insulating layer disposed about the inner semi-conductive layer, and an outer semi-conductive layer disposed about the insulating layer; and a metallic waterstop layer disposed about the insulation system, the metallic waterstop layer being formed by a first section which is a corrugated metallic waterstop layer and a second section which is a smooth metallic waterstop layer.

[0006] The upper section of the dynamic submarine power cable is the part of the dynamic submarine power cable that is most affected by fatigue due to wave motions in the surface area of ​​the water body where the dynamic submarine power cable is installed. The corrugated metallic waterstop layer provides better fatigue resistance properties than the smooth metallic waterstop layer, and the dynamic submarine power cable is advantageously installed such that the corrugated metallic waterstop layer extends along the upper section of the dynamic submarine power cable. Further down the water column, the dynamic submarine power cable is much less affected by wave motions, but at deeper depths, hydrostatic pressures may affect the shape of the corrugated metallic waterstop layer. Therefore, advantageously, the smooth metallic waterstop layer forms the lower section of the dynamic submarine power cable to better withstand the surrounding hydrostatic pressures without any deformation of the metallic waterstop layer at deeper water depths.

[0007] The smooth metal waterstop is not corrugated.

[0008] According to one embodiment, in an installed state, the first section is an upper section and the second section is a lower section of the dynamic submarine power cable.

[0009] According to one embodiment, the corrugated metallic waterstop layer extends from a first end of the dynamic submarine power cable, or within 10 to 15 meters of the first end, until the corrugated metallic waterstop layer transitions to a smooth metallic waterstop layer, and the smooth metallic waterstop layer extends from the transition point to a second end of the dynamic submarine power cable opposite the first end.

[0010] According to one embodiment the first section is at least 50m long, such as at least 100m long, such as at least 150m long, such as at least 200m long.

[0011] According to one embodiment the first section is up to 800m long, such as up to 600m long, for example up to 400m long.

[0012] According to one embodiment the metal waterstop layer is made in one length in the area where the metal waterstop layer transitions from the corrugated metal waterstop layer to the smooth metal waterstop layer.

[0013] According to one embodiment, the insulation system is made in one length along the entire length of the dynamic submarine power cable. The dynamic submarine power cable may therefore be free of any factory splices along its entire length. Factory splices connect two semi-finished cable lengths before any armour is applied, with restoration of the insulation system by vulcanisation. Typically, in the case of a factory splice, the conductors of the two semi-finished cable lengths are joined by welding.

[0014] In one embodiment, a polymeric layer is included disposed about the metallic waterstop layer, the polymeric layer extending along the first section and along the second section.

[0015] The polymer layer can be dielectric or semiconductive.

[0016] In one embodiment, an adhesive is included and disposed between the polymer layer and the smooth metallic waterstop layer in the second section to bond the polymer layer to the metallic waterstop along the second section.

[0017] If the polymer layer is dielectric, the adhesive may be dielectric, and if the polymer layer is semiconductive, the adhesive may be semiconductive.

[0018] According to one embodiment, the metallic water blocking layer includes one of copper, stainless steel, or aluminum.

[0019] The dynamic submarine power cable may be a medium voltage or a high voltage submarine power cable.

[0020] The dynamic submarine power cable may be an AC or DC dynamic submarine power cable.

[0021] The dynamic submarine power cable may include one or more power cores, each power core including a conductor, an insulation system disposed about the conductor, the insulation system including an inner semi-conductive layer disposed about the conductor, an insulating layer disposed about the inner semi-conductive layer, and an outer semi-conductive layer disposed about the insulating layer, and a metallic waterstop layer disposed about the insulation system, the metallic waterstop layer being formed by a first section that is a corrugated metallic waterstop layer and a second section that is a smooth metallic waterstop layer.

[0022] A dynamic submarine power cable may, for example, comprise one, two, or three power cores.

[0023] According to a second aspect of the present disclosure, there is provided an offshore structure comprising a floating platform and a dynamic subsea power cable of the first aspect suspended from the floating platform, with first and second sections of a metallic waterstop layer disposed in the water column between the floating platform and the seabed, the first section forming an upper section of the dynamic subsea power cable in the water column and the second section forming a lower section.

[0024] Thus, both the first section and the second section of the dynamic subsea power cable are suspended in the water column from the floating platform.

[0025] The dynamic submarine power cable may be joined to a static submarine power cable laid on the seabed. The joint may be located on the seabed, such that a portion of the second section of the dynamic submarine power cable may be laid on the seabed.

[0026] According to a third aspect of the present disclosure, there is provided a method for manufacturing a dynamic submarine power cable comprising a conductor and an insulation system disposed around the conductor, the insulation system comprising an inner semi-conductive layer disposed around the conductor, an insulation layer disposed around the inner semi-conductive layer, and an outer semi-conductive layer disposed around the insulation layer, the method including: a) corrugating a metallic tube disposed around the insulation system to form a first section of a metallic waterstop layer of the dynamic submarine power cable, the corrugated metallic waterstop layer; and b) performing diameter reduction on the metallic tube disposed around the insulation system to form a second section of the metallic waterstop layer, the smooth metallic waterstop layer, wherein the first section and the second section together define an axial length of the metallic waterstop layer.

[0027] According to one embodiment, during steps a) and b), the dynamic submarine power cable is of one length, and the metal tube of step a) and the metal tube of step b) are identical and made of one length.

[0028] According to one embodiment, the metal tubes of steps a) and b) are physically separate metal tubes, and the method comprises, after steps a) and b), c) joining the first section and the second section.

[0029] In general, all terms used in the claims should be interpreted according to their ordinary meaning in the art unless expressly defined otherwise herein. All references to "a / an / the element, device, component, means," etc. should be openly interpreted as referring to at least one instance of the element, device, component, means, etc., unless expressly specified otherwise.

[0030] Specific embodiments of the inventive concept will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0031] [Figure 1]1 illustrates a schematic diagram of an example of a dynamic submarine power cable; [Diagram 2] 1A and 1B show schematic side views of a portion of a metallic waterstop layer that transitions between corrugated and smooth. [Diagram 3] 1 shows a schematic representation of an offshore structure; [Figure 4] 1 is a flow chart of a method for manufacturing a dynamic submarine power cable. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] The inventive concept will now be more fully described below with reference to the accompanying drawings showing exemplary embodiments. However, the inventive concept may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein, but rather, these embodiments are provided as examples so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like numbers refer to like elements throughout the description.

[0033] Figure 1 shows an example of a dynamic submarine power cable 1. The dynamic submarine power cable 1 depicted in Figure 1 has a single power core, but may alternatively comprise two or more power cores, such as two or three power cores.

[0034] The exemplary dynamic submarine power cable 1 comprises a conductor 3. The conductor 3 may typically comprise copper or aluminum.

[0035] The dynamic submarine power cable 1 comprises an insulation system 5. The insulation system 5 comprises an inner semiconducting layer 5a arranged around the conductor 3.

[0036] The insulating system 5 comprises an insulating layer 5b arranged radially outward of the inner semiconductive layer 5a and an outer semiconductive layer 5c arranged radially outward of the insulating layer 5b.

[0037] The insulation system 5 may be, for example, a three-layer extruded insulation system including a polymeric material, or the insulation system 5 may be formed of layers of oil-impregnated paper, the innermost and outermost layers being semi-conductive paper layers.

[0038] The dynamic submarine power cable 1 comprises a metallic waterstop layer 7 extending along most or even the entire length of the dynamic submarine power cable 1. The metallic waterstop layer 7 may for example comprise copper, in which case it may be pure copper or a copper alloy, or it may comprise aluminium, in which case it may be pure aluminium or an aluminium alloy, or it may have a laminated structure, or it may comprise stainless steel.

[0039] A metallic water blocking layer 7 is arranged radially outside the insulation system 5 .

[0040] The metallic waterstop layer 7 may be formed of a metallic sheath wrapped around the insulation system 5 and welded longitudinally during manufacture of the dynamic submarine power cable 1 .

[0041] The dynamic submarine power cable 1 may comprise a cushioning layer disposed between the insulation system 5 and the metallic waterstop layer 7. The cushioning layer may comprise a polymeric material. The cushioning layer may be semi-conductive.

[0042] The metallic waterstop layer 7 includes a first section that is corrugated and a second section that is smooth, i.e., not corrugated. In particular, along the entire length of the first section, the metallic waterstop layer 7 is a corrugated metallic waterstop layer, and along the entire length of the second section, the metallic waterstop layer 7 is a smooth metallic waterstop layer. The first section transitions into the second section, whereby the corrugated metallic waterstop layer transitions into a smooth metallic waterstop layer.

[0043] The corrugations of the corrugated metallic waterstop layer are formed in the axial direction of the dynamic submarine power cable 1. Here, the metallic waterstop layer 7 is undulating in the axial direction along the first section.

[0044] The dynamic submarine power cable 1 comprises a polymer layer 9. The polymer layer 9 is disposed around the metallic waterstop layer 7. The polymer layer 9 extends along the first section and along the second section. The polymer layer 9 may comprise, for example, a polyolefin, such as polyethylene or polypropylene, or polyvinyl chloride.

[0045] The polymer layer 9 may be in direct contact with the corrugated metallic waterstop layer.

[0046] The dynamic submarine power cable 1 may include an adhesive provided between the polymer layer 9 and the metallic waterstop layer 7 to bond the polymer layer 9 to the metallic waterstop layer 7 along the second section, i.e., where the metallic waterstop layer 7 is a smooth metallic waterstop layer.

[0047] The adhesive may include, for example, a polyolefin, such as polyethylene.

[0048] The dynamic submarine power cable 1 may comprise one or more armor layers 11. Each armor layer 11 comprises a number of armor wires 11a. The armor wires 11a may be helically laid around the polymer layer 9. The armor wires 11a may be metallic armor wires, for example galvanized or stainless steel, or copper wires, or may be made of a synthetic material, such as a polymeric material, or some of the armor wires may be made of metal and others of a synthetic material.

[0049] If the dynamic submarine power cable 1 comprises an armor layer 11, the dynamic submarine power cable 1 may comprise a bedding layer disposed between the polymer layer 9 and the innermost layer of the one or more armor layers 11. The bedding layer may be made of a polymer material.

[0050] The dynamic submarine power cable 1 comprises an outer sheath or outer serving 13 that forms the outermost layer of the dynamic submarine power cable 1. The outer sheath or outer serving 13 may comprise a polymeric material.

[0051] Figure 2 shows a side view of a portion of the dynamic submarine power cable 1. In particular, the metallic waterstop layer 7 is shown with components external to the metallic waterstop layer 7 removed for clarity.

[0052] In Figure 2, a first section 8a of the metallic waterstop layer 7, only a portion of which is shown, is shown to be a corrugated metallic waterstop layer 7a, and a second section 8b, only a portion of which is shown, is shown to be a smooth metallic waterstop layer 7b. The metallic waterstop layer 7 extends continuously along the entire length of the dynamic submarine power cable 1 and transitions between corrugated and smooth.

[0053] FIG. 3 shows an offshore structure 15 comprising a floating platform 17 floating on water 16 and a dynamic submarine power cable 1 .

[0054] The floating platform 17 may be, for example, a floating platform for a floating wind turbine, or a semi-submersible platform for oil and gas applications.

[0055] The dynamic submarine power cable 1 is suspended from a floating platform 17 and extends down to the seabed 19 .

[0056] The offshore structure 15 comprises a bending stiffener 21, or alternatively a bellmouth, connected to the floating platform 17, disposed around an upper portion of the dynamic submarine power cable 1. In particular, the bending stiffener 21, or bellmouth, is disposed around the upper section 1a of the dynamic submarine power cable 1. A first section 8a of the metallic waterstop layer 7 is disposed along the upper section 1a of the dynamic submarine power cable 1 as it hangs down from the floating platform 17 and extends to the seabed 19.

[0057] The first section 8a may be at least 50m long, such as at least 100m long, such as at least 150m long, such as at least 200m long. The first section 8a may be up to 800m long, such as up to 600m long, such as up to 400m long.

[0058] The dynamic subsea power cable 1 may be provided with buoyancy modules 23 to provide the dynamic subsea power cable 1 with a wavy configuration as it extends towards the seabed 19. Alternatively, the dynamic subsea power cable 1 may floatably hang from the floating platform 17.

[0059] The dynamic submarine power cable 1 has a lower section 1b, similar to the first section 8a, arranged to hang in the water column between the floating platform 17 and the seabed 19. The second section 8b is arranged alongside the lower section 1b of the dynamic submarine power cable 1.

[0060] The second section 8b may, according to one example, be at least 100 m long, for example at least 200 m long. The second section 8b may, according to one example, be up to 3000 m long or up to 5000 m long. In general, the length of the second section 8b depends on the water depth.

[0061] The lower section 1b, and therefore part of the second section 8b, may extend to the seabed 19 and along the seabed 19 to a junction 27 on the seabed 19 which connects the dynamic submarine power cable 1 to a static submarine power cable 27.

[0062] A method of manufacturing a dynamic submarine power cable such as the dynamic submarine power cable 1 will now be described with reference to FIG.

[0063] In a first example, the first section 8a and the second section 8b are manufactured in one length. The insulation system 5 may be made in one length along the entire length of the dynamic submarine power cable 1. Thus, in this example, no shop splices are performed to join the insulation system 5.

[0064] First, a metal tube is placed around the insulation system 5. The metal tube may be made by wrapping a metal sheath around the insulation system 5 and welding, soldering, or gluing the metal sheath longitudinally.

[0065] In a second example, the first section 8a and the second section 8b are manufactured in two separate lengths and then spliced. In this case, the dynamic submarine power cable 1, or more typically one or more power cores of the submarine power cable 1, may also typically be manufactured in two lengths that are spliced.

[0066] In both examples, in step a), a metal tube arranged around the insulation system 5 is corrugated to form a corrugated metallic waterstop layer 7a.

[0067] In step a), a first section 8a of the metallic water-stopping layer 7 is produced.

[0068] Step a) is carried out by a corrugating machine through which at least a portion or part of the dynamic submarine power cable 1, whose metallic tube is corrugated, passes.

[0069] In both examples, step b) involves carrying out a diameter reduction of the metal tube arranged around the insulation system 5 to form a smooth metallic water-stopping layer 7b.

[0070] Step b) is performed by a roller assembly through which the second section 8b of the dynamic submarine power cable 1 passes.

[0071] In step b) the second section 8b of the metallic water-stopping layer 7 is produced.

[0072] Step a) may be performed before step b) and step b) may be performed before step a). If the first section 8a and the second section 8b are physically separate lengths of metallic waterstop 7 during steps a) and b), steps a) and b) may be performed simultaneously if the factory provides such manufacturability.

[0073] In a first example, when steps a) and b) are performed, the corrugated metal waterstop layer 7a and the smooth dynamic metal waterstop layer 7b form the metal waterstop layer 7, in which case the metal waterstop layer 7 can be made to one length in the area where the metal waterstop layer 7 transitions from corrugated to smooth.

[0074] In a second example, the first section 8a and the second section 8b have to be joined after steps a) and b) have been performed. The joining may involve joining the conductor 3, the insulation system 5, and the corrugated metal waterstop layer 7a and the smooth metal waterstop layer 7b. The joining of the corrugated metal waterstop layer 7a and the smooth metal waterstop layer 7b may be performed, for example, by soldering or welding.

[0075] In one variation of the second example, only a portion of one of the metal tubes is corrugated. The remaining length of this metal tube can be made smooth by subjecting the remaining length of the metal tube to a diameter reduction, and the smooth portion can be joined with the smooth metal waterstop layer 7b made in step b).

[0076] The inventive concept has been described above primarily with reference to certain examples, however, as will be readily appreciated by those skilled in the art, other embodiments besides those disclosed above are equally possible within the scope of the inventive concept as defined by the appended claims.

Claims

1. A dynamic submarine power cable (1), Conductor (3) and An insulating system (5) arranged around the conductor (3), The insulating system (5) comprises an inner semiconducting layer (5a) disposed around the conductor (3), an insulating layer (5b) disposed around the inner semiconducting layer (5a), and an outer semiconducting layer (5c) disposed around the insulating layer (5b). A metal watertight layer (7) is arranged around the insulating system (5), The metal watertight layer (7) is formed by a first section (8a) which is a corrugated metal watertight layer (7a), and a second section (8b) which is a smooth metal watertight layer (7b), A dynamic submarine power cable (1) equipped with the following features.

2. The dynamic submarine power cable (1) according to claim 1, wherein, in its installed state, the first section (8a) is the upper section of the dynamic submarine power cable (1), and the second section (8b) is the lower section.

3. The dynamic submarine power cable (1) according to claim 1, wherein the corrugated metal watertight layer (7a) extends from a first end of the dynamic submarine power cable (1), or from a position within 10 to 15 meters from the first end, until the corrugated metal watertight layer (7a) transitions to the smooth metal watertight layer (7b), and the smooth metal watertight layer (7b) extends from the transition point to a second end of the dynamic submarine power cable (1) opposite to the first end.

4. The dynamic submarine power cable (1) according to claim 1, wherein the first section (8a) is at least 50 m long, at least 100 m long, at least 150 m long, or at least 200 m long.

5. The dynamic submarine power cable (1) according to claim 1, wherein the first section (8a) has a maximum length of 800 m, a maximum length of 600 m, or a maximum length of 400 m.

6. The dynamic submarine power cable (1) according to claim 1, wherein the metal watertight layer (7) is made to be one length in the region where it transitions from the corrugated metal watertight layer (7a) to the smooth metal watertight layer (7b).

7. The dynamic submarine power cable (1) according to claim 1, wherein the insulating system (5) is manufactured in a single length along the entire length of the dynamic submarine power cable (1).

8. The dynamic submarine power cable (1) according to claim 1, comprising a polymer layer (9) disposed around the metal watertight layer (7), wherein the polymer layer (9) extends along the first section (8a) and along the second section (8b).

9. The dynamic submarine power cable (1) according to claim 8, comprising an adhesive, wherein the adhesive is disposed between the polymer layer (9) and the smooth metal waterproof layer (7b) in the second section (8b) to bond the polymer layer (9) to the metal waterproof layer (7) along the second section (8b).

10. The dynamic submarine power cable (1) according to claim 1, wherein the metal watertight layer (7) comprises one of copper, stainless steel, or aluminum.

11. An offshore structure (15) comprising a floating platform (17) and a dynamic submarine power cable (1) according to any one of claims 1 to 10 suspended from the floating platform (17), wherein the first section (8a) and the second section (8b) of the metal watertight layer (7) are arranged in a water column between the floating platform (17) and the seabed (19), and in the water column, the first section (8a) forms the upper section of the dynamic submarine power cable (1) and the second section (8b) forms the lower section.

12. A method for manufacturing a dynamic submarine power cable (1) comprising a conductor (3) and an insulating system (5) disposed around the conductor (3), wherein the insulating system (5) comprises an inner semiconducting layer (5a) disposed around the conductor (3), an insulating layer (5b) disposed around the inner semiconducting layer (5a), and an outer semiconducting layer (5c) disposed around the insulating layer (5b), wherein the method is a) By corrugating the metal tubes arranged around the insulating system (5), a corrugated metal watertight layer (7a) is formed, which is the first section (8a) of the metal watertight layer (7) of the dynamic submarine power cable (1), b) performing a diameter reduction on the metal tubes arranged around the insulating system (5) to form a smooth metal watertight layer (7b), which is a second section (8b) of the metal watertight layer (7), The first section (8a) and the second section (8b) together define the axial length of the metal watertight layer (7). method.

13. The method according to claim 12, wherein during steps a) and b), the dynamic submarine power cable (1) is of one length, and the metal tube in step a) and the metal tube in step b) are the same and are made of one length.

14. The method of claim 12, wherein the metal tubes in step a) and b) are physically separate metal tubes, and the method further comprises, after step a) and b), c) joining the first section (8a) and the second section (8b).

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