Offshore system comprising dynamic submarine power cable

Abstract

To provide an offshore system comprising a dynamic submarine power cable.SOLUTION: An offshore system comprises: a dynamic submarine power cable 11; a bend stiffener 9 having a lower end 9b and an upper end 9a, the bend stiffener 9 having a central channel extending from the lower end 9b to the upper end 9a, the central channel receiving the dynamic submarine power cable 11 with a radial spacing between an inner surface of the central channel and an outer surface of the dynamic submarine power cable 11 along the length of the dynamic submarine power cable 11 arranged in the bend stiffener 9, the radial spacing forming a longitudinal channel between the bend stiffener 9 and the dynamic submarine power cable 11; and a fluid flow device 13 configured to generate a fluid flow inside the longitudinal channel.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Power generating floating offshore structures, such as floating wind turbines, are connected to dynamic subsea power cables to deliver the power generated by the floating wind turbines to the power grid. Other types of floating offshore structures, such as floating oil platforms, can be connected to dynamic subsea power cables for power consumption purposes.

[0003] The floating offshore structure is subjected to wave motions, therefore the dynamic subsea power cable is connected to the floating offshore structure via bending stiffeners to control the bending radius of the cable and reduce fatigue loads on the cable. Summary of the Invention

[0004] Power cables are designed to be able to operate at a maximum operating temperature which may be 90°C according to international standards such as IEC 60287-1-1.

[0005] It has been found that the bending stiffener, due to its low thermal conductivity, creates a cable hot spot along the cable path between the seabed and the floating offshore structure. This hot spot is the hottest area of ​​the dynamic submarine power cable. The maximum current allowed in the dynamic submarine power cable is therefore determined by the temperature within the power cable as it extends through the bending stiffener.

[0006] A general object of the present disclosure is to provide an offshore system that overcomes, or at least mitigates, problems in the prior art.

[0007] Thus, there is provided an offshore system comprising: a dynamic submarine power cable; a bend stiffener having a lower end and an upper end, the bend stiffener having a central channel extending from the lower end to the upper end, the central channel receiving the dynamic submarine power cable with a radial spacing between an inner surface of the central channel and an outer surface of the dynamic submarine power cable along a length of the dynamic submarine power cable disposed in the bend stiffener, the radial spacing forming a longitudinal channel between the bend stiffener and the dynamic submarine power cable; and a fluid flow device configured to generate a fluid flow within the longitudinal channel.

[0008] Thus, hot spot regions of the dynamic submarine power cable are cooled by forced cooling by the fluid flow device. As a result, higher currents can be supplied through the dynamic submarine power cable and / or the cross section of the conductor(s) of the dynamic submarine power cable can be reduced during the design stage as a result of a cooler dynamic submarine power cable in the bending stiffener.

[0009] As an example, the applicant has taken a 3 x 1000 mm conductor having a maximum allowable conductor temperature of 90°C. 2 The improvement given by forced cooling was analysed for a 230 kV nominal voltage AC dynamic submarine power cable in . In the simulation, a current of 1050 A was fed through the dynamic submarine power cable. This resulted in a maximum conductor temperature of the cable inside the bending stiffener of about 140 °C without cooling. When forced air cooling through the bending stiffener with a speed of 1 m / s was included in the simulation, the assumed ambient temperature was 30 °C and the maximum conductor temperature reached a maximum of about 90 °C.

[0010] According to one embodiment, the fluid flow device is configured to generate a fluid flow in a direction from the top to the bottom.

[0011] The bend stiffener tapers in a direction from the top to the bottom. Thus, the bend stiffener has the thickest radial dimension in the top half closer to the top than the bottom. Thus, the uncooled dynamic submarine power cable reaches its hottest point in the top half of the bend stiffener. By generating a fluid flow in a direction from the top to the bottom, the fluid passing the hottest point is cooler than, for example, if the fluid flow is provided in a direction from the bottom to the top, because the fluid travels a shorter distance inside the bend stiffener along the dynamic submarine power cable before reaching the hottest point. As a result, the hottest point is cooled more efficiently.

[0012] The fluid flow devices may be arranged to provide fluid flow along the entire length of the longitudinal channel and thus along the entire length of the bending stiffener.

[0013] According to one embodiment the fluid flow device is configured to generate a fluid flow at a velocity in the range of 0.5-10 m / s.

[0014] According to one embodiment the fluid flow device is configured to generate a fluid flow at a velocity in the range of 0.5-5 m / s.

[0015] According to one embodiment the fluid flow device is configured to generate a fluid flow at a velocity in the range of 0.5 to 3 m / s.

[0016] According to one embodiment the fluid flow device is configured to generate a fluid flow at a velocity in the range of 0.5 to 2 m / s.

[0017] According to one embodiment, the fluid flow device comprises a first fan.

[0018] The first fan may be a first axial fan or a first radial fan. Alternatively, the first fan may be an axial fan.

[0019] The offshore system may comprise a tube to which the bend stiffener is attached and to which the longitudinal channel is in fluid communication. The tube may comprise a first radial opening, and the first fan may be configured to move air into the tube through the first radial opening such that airflow enters the longitudinal channel of the bend stiffener from above. Alternatively, the first fan may be positioned to blow air axially into the longitudinal channel from an axial top opening above the bend stiffener.

[0020] According to one embodiment the fluid flow device comprises a second fan.

[0021] The second fan may be a second axial fan or a second radial fan. Alternatively, the second fan may be an axial fan.

[0022] The offshore system may comprise a tube to which the bend stiffener is attached and to which the longitudinal channel is in fluid communication. The tube may comprise a second radial opening, and the second fan may be configured to move air into the tube through the second radial opening such that airflow enters the longitudinal channel of the bend stiffener from above. Alternatively, the second fan may be positioned to blow air axially into the longitudinal channel from an axial top opening above the bend stiffener.

[0023] According to one embodiment, the fluid flow is an air flow.

[0024] According to one embodiment, the flexural stiffener is an airborne flexural stiffener.

[0025] According to one embodiment, the dynamic submarine power cable is a high voltage power cable with a rated voltage of at least 66 kV.

[0026] One embodiment comprises an offshore floating structure, and a form of bending stiffener is connected to the offshore floating structure.

[0027] According to one embodiment, the offshore floating structure is one of a floating wind turbine, a floating electrical substation, a floating hydrocarbon platform, or a floating hydrocarbon vessel.

[0028] In general, all terms used in the claims should be interpreted according to their ordinary meaning in the art unless otherwise expressly defined herein. All references to "a / an / the element, apparatus, component, means, etc." should be interpreted non-limitingly as referring to at least one example of the element, apparatus, component, means, etc., unless otherwise specified. Specific embodiments of the inventive concept will now be described, by way of example, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0029] [Figure 1] 1 shows a schematic of an offshore system. [Diagram 2] 2 shows a schematic cross-sectional view of an enlarged portion of the offshore system of FIG. 1; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] The inventive concept will now be more fully described below with reference to the accompanying drawings, in which exemplary embodiments are shown. 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. 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 reference numerals refer to like elements throughout the description.

[0031] 1 shows an example of an offshore system 1. The offshore system 1 includes an offshore floating structure 3.

[0032] The offshore system 1 is deployed in water 5 such as seawater. Specifically, the offshore floating structure 3 is deployed in water 5 and floats on the water surface.

[0033] In this embodiment, the offshore floating structure 3 is a floating wind turbine, but may alternatively be, for example, a floating electrical substation, a floating hydrocarbon platform, a floating hydrocarbon vessel, a semi-submersible platform, or any other offshore floating structure that generates, relays, or consumes electricity.

[0034] The offshore floating structure 3 may comprise an offshore structure pipe 7. The offshore structure pipe 7 may be made of a metal, such as steel. The offshore structure pipe 7 extends vertically or essentially vertically downwards in a direction towards the seabed.

[0035] The offshore structure pipe 7 may be an I-pipe.

[0036] The offshore system 1 includes a bending stiffener 9. The bending stiffener 9 has an upper end 9a and a lower end 9b. The bending stiffener 9 tapers in a direction from the upper end 9a to the lower end 9b.

[0037] The flexural stiffener 9 has a central channel extending from an upper end 9a to a lower end 9b along a longitudinal axis of the flexural stiffener 9.

[0038] The bending reinforcement 9 is connected to the offshore structure pipe 7. The upper end 9a of the bending reinforcement 9 is connected to the lower part of the offshore structure pipe 7. The offshore structure pipe 7 is disposed vertically above the bending reinforcement 9.

[0039] Alternatively, the bending stiffeners 9 may be connected to a balcony (not shown) of the offshore floating structure 3 .

[0040] In this embodiment, the bending reinforcement member 9 is an aerial bending reinforcement member. Therefore, the bending reinforcement member 9 does not sink in the water 5.

[0041] The offshore system 1 comprises a dynamic submarine power cable 11 .

[0042] The dynamic submarine power cable 11 may be a single or multi-phase AC power cable or a single or multi-pole DC power cable.

[0043] The dynamic submarine power cable 11 may be a high voltage AC or DC power cable.

[0044] The dynamic submarine power cable 11 comprises a conductor and an insulation system disposed around the conductor. The insulation system comprises an inner semiconducting layer, an insulating layer disposed outside the inner semiconducting layer, and an outer semiconducting layer disposed outside the insulating layer.

[0045] The dynamic submarine power cable 11 comprises a metallic water barrier arranged concentrically with the conductor outside the insulation system. The metallic water barrier may be corrugated or smooth. The metallic water barrier may contain lead or may be lead-free. If lead-free, the metallic water barrier may comprise, for example, copper, aluminum, or stainless steel. Alternatively, the dynamic submarine cable may have a wet or semi-wet design, i.e., there is no metallic water barrier.

[0046] The dynamic submarine power cable 11 comprises a polymer sheath disposed on the outside of a metallic water barrier.

[0047] The dynamic submarine power cable 11 may comprise one or more armor layers disposed about the polymer sheath. The armor layer(s) may include metal wires or ropes, for example made of galvanized steel or austenitic stainless steel, synthetic wires such as jacketed aramid fibers, or a combination of both.

[0048] The dynamic submarine power cable 11 may have an outer serving disposed outside the one or more armor layers.

[0049] When the dynamic submarine power cable 11 includes multiple electrical phases or poles, the dynamic submarine power cable 11 includes multiple conductors, each conductor having the corresponding structures described above disposed therearound, i.e., insulation system, metallic water barrier, and polymer sheath. Each such structure forms a power core. Armor layer(s) are disposed around all of the power cores.

[0050] The dynamic submarine power cable 11 passes through the entire bending stiffener 9 in a central channel of the bending stiffener 9 .

[0051] A dynamic submarine power cable 11 extends from the offshore floating structure 3 to the seabed.

[0052] The dynamic submarine power cable 11 passes through the offshore structure pipe 7 and is fixed to the offshore floating structure 3. The dynamic submarine power cable 11 can be fixed to the offshore floating structure 3 by a hang-off device.

[0053] The dynamic submarine power cable 11 terminates on the offshore floating structure 3 .

[0054] The dynamic submarine power cable 11 is cooled by forced fluid flow within the bending stiffeners 9, as will be described in more detail below.

[0055] FIG. 2 shows an enlarged view of the offshore system 1 in the region of the bending stiffeners 9 .

[0056] The central channel 9c of the bending stiffener has an inner surface that is radially spaced from the outer surface of the dynamic submarine power cable 11 along the entire length of the dynamic submarine power cable 11 that passes through the bending stiffener 9. Thus, there is a radial spacing between the dynamic submarine power cable 11 and the central channel 9c.

[0057] The radial spacing forms a longitudinal channel between the bending stiffener 9 and the dynamic submarine power cable 11. The longitudinal channel extends from the upper end 9a to the lower end 9b of the bending stiffener 9 along the entire length of the dynamic submarine power cable 11 disposed within the bending stiffener 9.

[0058] The offshore structure tube 7 has an inner tube channel 7a in fluid communication with the longitudinal channels of the bending stiffeners 9. The longitudinal channels open vertically upwards into the inner tube channel 7a.

[0059] The offshore system 1 comprises a fluid flow device 13. The fluid flow device 13 is configured to generate a fluid flow within the longitudinal channel.

[0060] The fluid flow device 13 is configured to generate a fluid flow having a velocity in the range 0.5-10 m / s, for example in the range 0.5-5 m / s, such as 0.5-3 m / s or 0.5-2 m / s.

[0061] The speed or flow rate may be determined based on the magnitude of the current passing through the dynamic submarine power cable 11 and / or the ambient air temperature.

[0062] The fluid flow device 13 is, by way of example, configured to generate a fluid flow in a direction from the upper end 9a towards the lower end 9b. The fluid flow device 13 is configured to generate a fluid flow along the entire longitudinal channel.

[0063] According to one example, the fluid flow device 13 is located within the offshore structure pipe 7 .

[0064] The offshore system 1 may, according to one variant, comprise a fluid intake 15 configured to draw ambient air outside the offshore structural tube 7 into the fluid flow device 13 for discharging into the longitudinal channel. The fluid intake 15 may comprise a through opening extending through the wall of the offshore structural tube 7 to the fluid flow device 13.

[0065] The fluid flow device 13 may include one or more fans, for example a first fan and a second fan. Multiple fans provide redundancy in the event of a fan failure.

[0066] The dynamic submarine power cable 11 may comprise a fiber optic cable configured to measure a temperature of a conductor of the dynamic submarine power cable 11 within the bend stiffener 9. The offshore system 1 may comprise a control system configured to control the fluid flow device 13 based on a conductor temperature measured along a section of the dynamic submarine power cable 11 that extends within the bend stiffener 9. The control system may be configured to control the fluid flow device 13 based on, for example, a maximum conductor temperature measured along a section of the dynamic submarine power cable 11 that extends within the bend stiffener 9.

[0067] According to one example, the offshore system 1 may comprise an air cooler configured to cool air and supply the cooled air to the fluid flow device 13 .

[0068] As shown in Figure 2, in use, the fluid flow device 13 generates a fluid flow 17 within the bend reinforcement 9. The fluid flow 17 is an air flow. The fluid flow 17 is in a direction from the upper end 9a to the lower end 9b of the bend reinforcement 9. The fluid flow 17 exits the bend reinforcement at the lower end 9b of the bend reinforcement 9.

[0069] 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 than those disclosed above are equally possible within the scope of the inventive concept, as defined by the appended claims.

Claims

1. Offshore system (1), Dynamic submarine power cable (11) and A bending reinforcement member (9) having a lower end (9b) and an upper end (9a), wherein the bending reinforcement member (9) has a central channel extending from the lower end (9b) to the upper end (9a), and the central channel accepts the dynamic submarine power cable (11) along the length of the dynamic submarine power cable (11) disposed within the bending reinforcement member (9) by creating a radial gap between the inner surface of the central channel and the outer surface of the dynamic submarine power cable (11), and the radial gap forms a longitudinal channel between the bending reinforcement member (9) and the dynamic submarine power cable (11), An offshore system (1) comprising a fluid flow device (13) configured to generate a fluid flow inside the longitudinal channel.

2. The offshore system (1) according to claim 1, wherein the fluid flow device (13) is configured to generate the fluid flow in a direction from the upper end (9a) to the lower end (9b).

3. The offshore system (1) according to claim 1 or 2, wherein the fluid flow device (13) is configured to generate the fluid flow at a speed in the range of 0.5 to 10 m / s.

4. The offshore system (1) according to claim 1 or 2, wherein the fluid flow device (13) is configured to generate the fluid flow at a speed in the range of 0.5 to 5 m / s.

5. The offshore system (1) according to claim 1 or 2, wherein the fluid flow device (13) is configured to generate the fluid flow at a speed in the range of 0.5 to 3 m / s.

6. The offshore system (1) according to claim 1 or 2, wherein the fluid flow device (13) is configured to generate the fluid flow at a speed in the range of 0.5 to 2 m / s.

7. The offshore system (1) according to claim 1 or 2, wherein the fluid flow device (13) comprises a first fan.

8. The offshore system (1) according to claim 7, wherein the fluid flow device (13) comprises a second fan.

9. The offshore system (1) according to claim 1 or 2, wherein the fluid flow is an airflow.

10. The offshore system (1) according to claim 1 or 2, wherein the bending reinforcement member (9) is an aerial bending reinforcement member.

11. The offshore system (1) according to claim 1 or 2, wherein the dynamic submarine power cable (11) is a high-voltage power cable with a rated voltage of at least 66 kV.

12. The offshore system (1) according to claim 1 or 2, comprising an offshore floating structure (3), wherein the bending reinforcement member (9) is connected to the offshore floating structure (3).

13. The offshore system (1) according to claim 12, wherein the offshore floating structure (3) is one of a floating wind turbine, a floating substation, a floating hydrocarbon platform, or a floating hydrocarbon vessel.

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