METHOD FOR OFFSHORE INSTALLING OF POWER CABLES OR TUBES FOR POWER CABLES FOR WIND TURBINE INSTALLATIONS AND SEABED VEHICLE

Abstract

Provided is a method for offshore installing of power cables or tubes for power cables for wind turbine installations, wherein an end of an incoming power cable and an end of an outgoing power cable or an end of an incoming tube and an end of an outgoing tube are pulled into an offshore wind turbine installation simultaneously. By pulling both ends of the incoming and outgoing power cables/tubes into the offshore wind turbine installation simultaneously, the ends of the incoming and outgoing power cables/tubes can be pulled into the offshore wind turbine installation in a single process step.

Claims

1. A method for offshore installing of power cables or tubes for power cables for wind turbine installations, wherein an end of an incoming power cable and an end of an outgoing power cable or an end of an incoming tube and an end of an outgoing tube are pulled into an offshore wind turbine installation simultaneously.

2. The method according to claim 1, wherein the incoming and outgoing power cables or the incoming and outgoing tubes are, during pulling their ends into the offshore wind turbine installation, of one piece such that their pulled in ends are continuous with each other.

3. The method according to claim 2, wherein pulling the ends of the incoming and outgoing power cables or of the incoming and outgoing tubes into the offshore wind turbine installation includes bending the incoming and outgoing power cables or the incoming and outgoing tubes relative to each other at their continuous ends.

4. The method according to claim 1, wherein pulling the ends of the incoming and outgoing power cables or of the incoming and outgoing tubes into the offshore wind turbine installation includes connecting a pulling head with the ends of the incoming and outgoing power cables or with the ends of the incoming and outgoing tubes.

5. The method according to claim 1, comprising, after the step of pulling, the step of cutting the incoming and outgoing power cables or the incoming and outgoing tubes at their continuous ends inside the offshore wind turbine installation.

6. The method according to claim 1, comprising installing a power cable or a tube on or in a seabed by a seabed vehicle, and providing an additional length of the power cable or tube close to the offshore wind turbine installation, the additional length forming the incoming and outgoing power cables or the incoming and outgoing tubes.

7. The method according to claim 6, wherein the additional length of the power cable or tube is provided by lifting a depressor of the seabed vehicle.

8. The method according to claim 7, wherein the additional length of the power cable or tube is provided by rotating a depressor wheel of the depressor of the seabed vehicle.

9. The method according to claim 6, wherein the power cable or tube is installed on or in the seabed by forming a trench in the seabed and laying the power cable or tube into the trench.

10. The method according to claim 9, wherein after laying the power cable or tube into the trench, the trench is buried by the seabed vehicle.

11. The method according to claim 1, wherein the ends of the incoming and outgoing power cables or of the incoming and outgoing tubes are pulled into the offshore wind turbine installation by a messenger cable acting as a pulling rope.

12. The method according to claim 6, wherein prior to installing the power cable or tube on or in the seabed by the seabed vehicle, one end of the messenger cable is installed inside the offshore wind turbine installation and the other end of the messenger cable is provided outside of the offshore wind turbine installation and below sea level.

13. The method according to claim 12, wherein the other end of the messenger cable is provided with buoyancy means or a buoyancy device.

14. The method according claim 1, wherein the ends of the incoming and outgoing power cables or the ends of the incoming and outgoing tubes are pulled into the offshore wind turbine installation up to a height above sea level.

15. A seabed vehicle for performing at least one step of the method according to claim 1, the seabed vehicle comprising: a main frame, skids for skidding on the seabed, the skids being fixed to the main frame, a plough for forming a trench in the seabed, the plough being fixed to the main frame, burying means or apparatus for burying the trench after a power cable or tube supplied by a vessel has been laid in the trench, a pivotable and rotatable depressor for holding down the power cable or tube in the trench prior to burying it and for providing an additional length of the power cable or tube at the offshore wind turbine installation by lifting the depressor, the additional length forming the incoming and outgoing power cables or the incoming and outgoing tubes the offshore wind turbine installation, wherein the depressor comprises a depressor wheel and a pivoting member, the depressor wheel being supported rotatably by the pivoting member, the pivoting member being supported pivotably by the main frame or the plough, and a robotic arm for grabbing the messenger cable acting as pulling rope and fixing the messenger cable to the power cable or tube, the robotic arm being fixed to the main frame.

Description

BRIEF DESCRIPTION

[0070] Some of the embodiments will be described in detail, with references to the following Figures, wherein like designations denote like members, wherein:

[0071] FIG. 1 shows a wind park with wind turbines according to an embodiment;

[0072] FIG. 2 shows a seabed vehicle installing a tube in the seabed while approaching one of the wind turbines of FIG. 1 according to an embodiment;

[0073] FIG. 3 shows another view of the seabed vehicle of FIG. 2;

[0074] FIG. 4 shows how the seabed vehicle from FIGS. 2 and 3 provides an additional length of the tube close to the wind turbine of FIG. 2 according to an embodiment;

[0075] FIG. 5 shows a detailed view of FIG. 4 in which a pulling head with a messenger cable is connected to the additional length of the tube;

[0076] FIG. 6 shows a detailed view of the pulling head from FIG. 5 in an initial position;

[0077] FIG. 7 shows a detailed view of the pulling head from FIG. 5 in an activated position;

[0078] FIG. 8 shows a view similar as FIG. 5 but with the pulling head in the activated state of FIG. 7;

[0079] FIG. 9 shows how the additional length of the tube is pulled into the wind turbine of FIG. 2 according to an embodiment, the additional length forming the incoming and outgoing tube of the wind turbine; and

[0080] FIG. 10 shows a flowchart illustrating a method for offshore installing of power cables or tubes for power cables, such as the tube of FIGS. 2 and 4 to 9, for the wind turbine of FIG. 2 according to an embodiment.

DETAILED DESCRIPTION

[0081] FIG. 1 shows an offshore wind farm 1 according to an embodiment. The offshore wind farm 1 comprises several offshore wind turbines. As an example, an offshore wind turbine 2 and another offshore wind turbine 3 of the wind farm 1 are shown in FIG. 1.

[0082] Each of the wind turbines 2 and 3 comprises a rotor 4 connected to a generator (not shown) arranged inside a nacelle 5. The nacelle 5 is arranged at the upper end of a tower 6 of the wind turbine 2, 3. The tower 6 is erected on a foundation 7 such as a monopile or tripile. The foundation 7 is connected to and/or driven into the seabed 8. The sea water is denoted with the reference numeral 9.

[0083] During operation of the wind turbine 2, 3, the wind's kinetic energy is converted into electrical energy by the generator in the nacelle 5. The power generated in the generator is transmitted via an interior power cable to a switch gear (not shown) in a lower part of the tower 6. The generated power is transmitted from the switch gear via a further interior power cable (not shown) to a hang-off zone 10 of the lower part of the tower 6. For an electrical connection from the hang-off zone 10 onward, electrical transmission means or a transmitter are required to connect the interior power cable of the wind turbine 2 to another offshore installation such as the wind turbine 3.

[0084] In the following an improved method for offshore installing of power cables or tubes for power cables for wind turbine installations is described with respect to FIGS. 2 to 10.

[0085] In step S1 of the method, a messenger cable 11 (FIG. 2) is provided at the wind turbine 2. One end 39 of the messenger cable 11 is connected to a winch 12 arranged at the hang-off platform 10 of the wind turbine 2. From there, the messenger cable 11 is unreeled from the winch 12 and guided through the interior of the lower part of the tower 6 and of the foundation 7. The messenger cable 11 is guided through an opening 13 to the outside of the wind turbine 2. At the outside of the wind turbine 2, a remotely operated underwater vehicle (ROV, not shown) lowered from a first vessel (not shown) connects the messenger cable 11 at its other end 40 with a pulling head 14 (FIG. 2). The ROV also connects buoyancy means or a buoyancy device 15, such as an air-filled balloon, with the pulling head 14. The buoyancy means or buoyancy device 15 cause the pulling head 14 to float above the sea bed 8. The ROV positions the pulling head 14 close to a main installation path 16 of a tube 17 (a power cable could be provided instead of the tube 17) such that the messenger cable 11 with the pulling head 14 is brought in place for the tube 17 to arrive in the next step.

[0086] In step S2, the tube 17 is installed in the seabed 8 by a seabed vehicle 18. The seabed vehicle 18 has been lowered from a support vessel (not shown) at the beginning of the installation path 16, e.g., at a first offshore wind turbine along the installation path 16. The seabed vehicle 18 is pulled at a pulling yoke 19 by the support vessel. The pulling yoke 19 is part of a main frame 38 of the seabead vehicle 18. Through the pull of the vessel, the seabed vehicle 18 is skidding on skids 20 over the floor of the seabed 8 along the installation path 16.

[0087] The seabed vehicle comprises a plough 21, as can best be seen in FIG. 3. The plough 21 is fixed to the main frame 38 of the seabead vehicle 18. Through the pull of the vessel at the pulling yoke 19, the plough 21 opens a trench 22 in the seabed 8 (FIG. 2). The tube 17 is continuously unreeled from a winch on the support vessel (not shown) and laid into the trench 22. In particular, the seabed vehicle 18 comprises a depressor 23 (FIG. 3) which can be pivoted downwards for forcing the tube 17 into the trench 22 (FIG. 2). The tube 17 laid into the trench 22 is buried by a roller cutter 24 of the seabed vehicle 18. The process of continuously forming a trench 22, laying the tube 17 in the trench 22 and burying it with the roller cutter 24 is performed until the seabed vehicle 18 reaches a position along the installation path 16 which is close, e.g., closest, to a wind turbine, such as the wind turbine 2.

[0088] In step S3, an additional length 25 of the tube 17 is provided at the installation path 16 close to the wind turbine 2 (FIG. 4). The additional length 25 is provided by the depressor 23.

[0089] The depressor 23 comprises, for example, a depressor wheel 26 and a pivoting member 27 (FIG. 3). The depressor wheel 26 is, for example, rotatably supported by the pivoting member 27. The pivoting member 27 is, for example, pivotably supported by the plough 21.

[0090] With the pivoting member 27 pivoted downwards (FIG. 2), the depressor 23 is used in step S2 for holding down the tube 17 in the trench 22 prior to burying it. With the pivoting member 27 pivoted upwards (FIGS. 4, 5, 8, 9), the depressor 23 is used in step S3 for providing the additional length 25 of the tube 17.

[0091] In step S3, firstly the support vessel pulling the seabed vehicle 18 for example slows down its speed. Further, the depressor 23 is lifted by pivoting the pivoting member 27 upwards (FIG. 4).

[0092] As the tube 17 is filled with air it is floating upwards as far as permitted by the upward lifted depressor 23. The tube 17 is continuously supplied by the support vessel in the upward lifted state of the depressor 23, thereby paying out portions of the tube 17 in form of a loop 28. Paying out of the tube 17 is further supported by rotation of the depressor wheel 26.

[0093] The loop 28 shown in FIG. 4 represents, for example, a first portion 29 of the additional length 25. For example, by pulling on this first portion 29 in the next step S4 in conjunction with the continuous supplying of the tube 17 from the support vessel, a second portion 30 of the additional length 25 is provided (FIG. 9).

[0094] The additional length 25, comprising for example the first and second portions 29, 30, is used for forming an incoming tube 31 and an outgoing tube 32 of the wind turbine 2. When the installation of the tube 17 at the wind turbine 2 will be completed, the incoming tube 31 will cover the path from the main installation path 16 to the foundation 7 of the wind turbine 2, through the opening 13 and to the hang-off platform 10 of the wind turbine 2. Furthermore, in the completed state, the outgoing tube 32 will cover the return path from the hang-off platform 10, through the opening 13 and back to main installation path 16.

[0095] In step S4, an end 33 of the incoming tube 31 and an end 34 of the outgoing tube 32 are pulled into the wind turbine 2 simultaneously (FIG. 9).

[0096] To perform step S4, firstly a robotic arm 35 of the seabed vehicle 18 is grabbing the pulling head 14 (FIG. 5) which has been provided at the right position for grabbing beforehand in step S1. The robotic arm 35 is moving the pulling head 14 towards the payed out additional length 25 of tube 17 and attaches it there. Where the pulling head 14 is attached to the additional length 25 of tube 17 marks in this example the transition between the first portion 29 of the additional length 25 (which will form the incoming tube 31) and the second portion 30 of the additional length 25 (which will form the outgoing tube 32).

[0097] The pulling head 14 has a bending function. The pulling head 14 comprises two arms 36 which can be flapped to bend the additional portion 25 of the tube 17 (FIGS. 6, 7). Further, the pulling head 14 comprises a middle portion 37 where the messenger cable 11 can be attached (FIG. 7). When the pulling head 14 is attached to the additional length 25 of the tube 17 the two arms 36 are attached at two spaced apart positions on the additional length 25 (FIG. 6). That means, one arm 36 of the pulling head 14 is attached to the first portion 29 of the additional length 25 forming the incoming tube 31. The other arm 36 of the pulling head 14 is attached to the second portion 30 of the additional length 25 forming the outgoing tube 32. By pulling on the middle portion 37 by the messenger cable 11 the arms 36 are flapped and the portion 29 of the additional length 25 forming the incoming tube 31 and the portion 30 of the additional length 25 forming the outgoing tube 32 are bent relative to each other (FIG. 7, 8).

[0098] After attaching the pulling head 14 to the incoming and outgoing tubes 31, 32, the messenger cable 11 is pulled into the wind turbine 2 (FIG. 9) by reeling up the winch 12 (FIG. 2). Thus, the ends 33, 34 of the incoming and outgoing tubes 31, 32 are pulled towards the foundation 7 of the wind turbine 2 and through the opening 13 in the foundation 7. The ends 33, 34 of the incoming and outgoing tubes 31, 32 are further pulled upwards inside the foundation 7 and, for example, also inside the tower 6. The ends 33, 34 of the incoming and outgoing tubes 31, 32 are, for example, pulled up to the hang-off platform 10 (FIG. 2).

[0099] In step S5, the incoming and outgoing tubes 31, 32 are cut inside the wind turbine 2, for example at the hang-off platform 10. In particular, the portions of the incoming and outgoing tubes 31, 32 damaged by the bending process (FIG. 7) are cut off.

[0100] In the further processing, power cables (not shown) can be inserted into the cut incoming and outgoing tubes 31, 32 for electrical connection of the wind turbine 2.

[0101] By the described method, the installation of tubes 17 for power cables can be efficiently installed for several wind turbines of a wind park, such as the wind turbine 2, 3 of the wind park 1 shown in FIG. 1. Advantageously, the seabed vehicle 18 is lowered only once from a vessel for connecting the several wind turbines. Further, the seabed vehicle 18 is driving continuously along a main installation path 16 and is providing an additional length 25 of the tube 17 close to each wind turbine (such as the wind turbines 2, 3). At this time, the pulling head 14 with the messenger cable 11 is ready for connection with the additional length 25 at each wind turbine (such as the wind turbines 2, 3). As soon as the additional length 25 forming the incoming and outgoing tubes 31, 32 is provided by the seabed vehicle 18 at a certain wind turbine, it is automatically connected with the pulling head 14 and pulled into the foundation 7 of the wind turbine 2, 3. Inside the wind turbine, the incoming and outgoing tubes 31, 32 can be cut in a dry and shield environment.

[0102] Although embodiments of the present invention have been described in accordance with various embodiments, it is obvious for the person skilled in the art that modifications are possible in all embodiments. In particular, instead of the tube 17 also a power cable could be directly installed by the described process steps. In this case, the power cable is directly buried by the seabed vehicle 18 in the seabed 8 in between positions of the wind turbines 2, 3. Further, an additional length of the power cable is provided at each of the wind turbines such as the wind turbine 2, 3. This additional length is then pulled as incoming and outgoing power cable into the respective wind turbine by the pulling head 14, the robotic arm 35, and the messenger cable 11.

[0103] Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

[0104] For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.