阅读说明：本技术 用于风力涡轮机装置的电力电缆或电力电缆的管的海上安装的方法以及海底运载工具 (Method for offshore installation of a power cable or a pipe of a power cable for a wind turbine installation and a subsea vehicle ) 是由 J·索伦森 于 2020-03-05 设计创作，主要内容包括：一种用于风力涡轮机装置(2、3)的电力电缆或电力电缆的管(17)的海上安装的方法,其中同时将引入电力电缆的端部和引出电力电缆的端部或引入管(31)的端部(33)和引出管(32)的端部(34)牵引(S4)到海上风力涡轮机装置(2)中。通过同时将所述引入和引出电力电缆/管的两端牵引到所述海上风力涡轮机装置中,可以在单个过程步骤中将所述引入和引出电力电缆/管的所述端部牵引到所述海上风力涡轮机装置中。(A method for offshore installation of a power cable or a pipe (17) of a power cable for a wind turbine installation (2, 3), wherein an end of a lead-in power cable and an end of a lead-out power cable or an end (33) of a lead-in pipe (31) and an end (34) of a lead-out pipe (32) are simultaneously pulled (S4) into the offshore wind turbine installation (2). By simultaneously pulling both ends of the incoming and outgoing power cables/pipes into the offshore wind turbine installation, the ends of the incoming and outgoing power cables/pipes can be pulled into the offshore wind turbine installation in a single process step.)

1. A method for offshore installation of a power cable or a pipe (17) of a power cable for a wind turbine installation (2, 3), wherein an end of a lead-in power cable and an end of a lead-out power cable or an end (33) of a lead-in pipe (31) and an end (34) of a lead-out pipe (32) are simultaneously pulled (S4) into the offshore wind turbine installation (2).

2. Method according to claim 1, wherein the incoming and outgoing power cables or the incoming and outgoing pipes (31, 32) are one piece during pulling (S4) their ends (33, 34) into the offshore wind turbine device (2), such that the pulling-in ends (33, 34) of the incoming and outgoing power cables or the incoming and outgoing pipes are continuous with each other.

3. The method of claim 2, wherein pulling (S4) the ends (33, 34) of the incoming and outgoing power cables or the incoming and outgoing tubes (31, 32) into the offshore wind turbine device (2) comprises bending the incoming and outgoing power cables or the incoming and outgoing tubes (31, 32) relative to each other at successive ends (33, 34) of the incoming and outgoing power cables or the incoming and outgoing tubes.

4. The method of any one of claims 1-3, wherein pulling (S4) the ends (33, 34) of the incoming and outgoing power cables or the incoming and outgoing pipes (31, 32) into the offshore wind turbine device (2) comprises connecting a pulling head (14) with the ends of the incoming and outgoing power cables or the ends (33, 34) of the incoming and outgoing pipes (31, 32).

5. The method according to any one of claims 2-4, comprising, after the pulling step (S4), the step of cutting (S5) the incoming and outgoing power cables or the incoming and outgoing tubes (31, 32) inside the offshore wind turbine device (2) at their continuous ends (33, 34).

6. The method according to any one of claims 1-5, comprising the steps of:

installing (S2) a power cable or pipe (17) on or in the seabed (8) by means of a subsea vehicle (18), and

providing (S3) an additional length (25, 29, 30) of the power cable or pipe (17) close to the offshore wind turbine device (2), the additional length (25) forming the incoming and outgoing power cables or the incoming and outgoing pipes (31, 32).

7. The method according to claim 6, wherein the extra length (25) of the power cable or pipe (17) is provided by lifting a settler (23) of the subsea vehicle (18).

8. The method according to claim 7, wherein the extra length (25) of the power cable or pipe (17) is provided by rotating a settler wheel (26) of the settler (23) of the subsea vehicle (18).

9. The method according to any one of claims 6-8, wherein the power cable or pipe (17) is installed (S2) on or in the seafloor (8) by forming a trench (22) in the seafloor (8) and laying the power cable or pipe (17) into the trench (22).

10. Method according to claim 9, wherein the sea trench (22) is buried by means of the subsea vehicle (18) after laying the power cable or pipe (17) into the sea trench (22).

11. Method according to any of claims 1-10, wherein the ends (33, 34) of the incoming and outgoing power cables or the incoming and outgoing pipes (31, 32) are pulled (S4) into the offshore wind turbine device (2) by means of a hoist cable (11) acting as a pulling rope.

12. Method according to claims 6 and 11, wherein one end (39) of the hoist cable (11) is installed inside the offshore wind turbine device (2) and the other end (40) of the hoist cable (11) is provided outside the offshore wind turbine device (2) and below sea level (7) before installing (S2) the power cable or pipe (17) on or in the sea floor (8) by means of the subsea vehicle (18).

13. A method according to claim 12, wherein the other end (40) of the hoist cable (11) is provided with a buoyancy device (15).

14. Method according to any of claims 1-13, wherein the ends of the incoming and outgoing power cables or the ends (33, 34) of the lead-in and lead-out pipes (31, 32) are pulled (S4) into the offshore wind turbine device (2) up to a height (10) above sea level (7).

15. A subsea vehicle (18) for carrying out at least one step of the method according to any one of claims 1-14, the subsea vehicle (18) comprising:

-a main frame (38),

-a skid (20) for sliding on the seabed (8), the skid (20) being fixed to the main frame (38),

-a plough (21) for forming a sea ditch (22) in the sea floor (8), the plough (21) being fixed to the main frame (38),

-burying means (24) for burying the sea trench (22) after power cables or pipes (17) supplied by a vessel have been laid in the sea trench (22),

-a pivotable and rotatable settler (23) for pressing down the power cable or pipe (17) in the sea gully (22) before burying the power cable or pipe (17) and for providing an extra length (25) of the power cable or pipe (17) at the offshore wind turbine unit (2) by lifting the settler (23), the extra length (25) forming the incoming and outgoing power cables or pipes (31, 32) of the offshore wind turbine unit (2), wherein the settler (23) comprises a settler wheel (26) and a pivoting member (27), the settler wheel (26) being rotatably supported by the pivoting member (27), the pivoting member (27) being pivotably supported by the main frame (38) or the plow (21), and

-a robot arm (35) for gripping the hoist cable (11) acting as a pulling rope and securing the hoist cable (11) to the power cable or tube (17), the robot arm (35) being secured to the main frame (38).

Technical Field

The present invention relates to a method for offshore installation of a power cable or a tube of a power cable for a wind turbine installation and a subsea vehicle.

Background

Offshore installations, such as offshore wind turbines, require a transmission link to another offshore or onshore installation, for example for transmitting the generated power. The transmission link is for example provided by installing the power cable directly in or above the seabed between several offshore locations, e.g. between wind turbine foundations and/or substations. Alternatively, the power cable is installed between several offshore locations by using empty pipes, as proposed in EP 3086424 Bl. After the installation of the empty pipe in or above the seabed, the power cable is inserted into the empty pipe.

The cabling of power cables for several offshore wind turbines (e.g. offshore wind farms) is a time and cost consuming process, both with and without the use of empty pipes.

In a first conventional approach, power cable routing is done section by section. This means that for each section between adjacent offshore locations, the subsea vehicle is lowered from the vessel to dig a trench into the sea floor between these locations, and the power cables or pipes supplied by the vessel are laid down into said trench. The subsea vehicle is then lifted onto the vessel again. Thus, in this method, the subsea vehicle must be lowered from the vessel to the seabed and lifted again for each single offshore wind turbine.

In a second conventional method as proposed in EP 3086424 Bl, the subsea vehicle installs the empty pipe in a continuous manner without the need to lower and lift the subsea vehicle for each single offshore wind turbine. This is achieved by mounting the empty pipe in an overlapping manner in the area close to each wind turbine device. The two overlapping pipes are supplied by two supplies on the first vessel. The pipe is cut by a subsea vehicle or by means of a second vessel, such that the free end of the pipe floats towards the sea level. In a further process step, the free end of the tube is guided through a separate opening in the wind turbine foundation and mounted inside.

Disclosure of Invention

It is an object of the present invention to provide an improved method for offshore installation of a power cable or a tube of a power cable of a wind turbine installation and an improved subsea vehicle.

Accordingly, a method for offshore installation of a power cable or a pipe of a power cable for a wind turbine installation is proposed, wherein an end of a lead-in power cable and an end of a lead-out power cable or an end of a lead-in pipe and an end of a lead-out pipe are simultaneously pulled into the offshore wind turbine installation.

By simultaneously pulling both ends of incoming and outgoing power cables/pipes into an offshore wind turbine installation, said ends of said incoming and outgoing power cables/pipes can be pulled into said offshore wind turbine installation in a single process step. For example, they may be towed by a single towing device (such as a single winch). Thus, they can be more easily pulled. Further, the incoming and outgoing power cables/pipes may be kept in close proximity to each other during towing. Thus, they can be easily pulled through a single opening of the offshore wind turbine device, in particular of its foundation. Further, they take up less space inside the wind turbine device, in particular the base thereof.

The offshore wind turbine installation is for example a wind turbine or a substation of a wind farm.

Offshore includes not only marine environments but also lakes and other open waters.

A wind turbine is a device used to convert kinetic energy of wind into electrical energy. A wind turbine comprises, for example, a rotor with one or more blades, a nacelle comprising a generator, and a tower holding the nacelle at its top end. The tower of the wind turbine is connected to a foundation of the wind turbine, such as a mono pile, a tri pile or a tripod in the sea bottom.

The offshore wind turbine may be part of a wind farm. The wind farm is in particular an array of interconnected wind turbines. The offshore wind turbine may be connected to neighbouring wind turbines and/or substations of the wind farm, e.g. by power cables and/or pipes.

A substation of a wind farm (also called a collection substation) is in particular a station configured to collect energy produced by all or several wind turbines of the wind farm. The substation is configured to receive energy generated by the wind turbine over a power cable.

The power cable is in particular an electrical cable configured for transmitting energy generated by an offshore wind turbine device to another offshore wind turbine device and/or to an onshore device.

The tube is in particular an empty tube. The tube is particularly long and flexible. The tube is for example sufficiently flexible to be wound on a reel or drum. The tube serves to guide and protect the power cable inserted therein after installation of the tube. The tube is made of, for example, plastic, thermoplastic, polyethylene and/or high density polyethylene.

The incoming and outgoing power cables are not limited to the case where power is supplied through the incoming power cable and power is taken out through the outgoing power cable. Further, the inlet and outlet pipes are not limited to the case where power is supplied through a power cable inserted into the inlet pipe and power is extracted through a power cable inserted into the outlet pipe. Instead of "lead in" and "lead out", the terms "first" and "second", respectively, may be used.

The ends of said incoming and outgoing power cables/pipes are drawn into the interior of the foundation, for example from the outer region of the offshore wind turbine installation below sea level, through the opening of the foundation of the offshore wind turbine installation below sea level, and up to the level (e.g. platform) where they are further processed. In the case of power cables, the further processing may include electrical connections to electrical cables that transmit power generated by generators in the nacelle. In the case of a pipe, the further processing may also include inserting a power cable into the pipe.

According to an embodiment, the incoming and outgoing power cables or the incoming and outgoing pipes are one piece during the process of pulling their ends into the offshore wind turbine device, such that their pulling ends are continuous with each other.

Pulling the ends of the incoming and outgoing power cables/pipes into the offshore wind turbine installation in a state in which the incoming and outgoing power cables/pipes are one piece allows to easily grab them and pull them into the wind turbine installation. For example, allowing them to be gripped in a single process step using a single tow head, a single robotic arm of the subsea vehicle, and/or a single messenger cable as a tow line.

Furthermore, by means of the single-piece arrangement, the incoming and outgoing power cables/pipes can be provided continuously, for example by unwinding them from a vessel, while avoiding cutting them below sea level. Furthermore, a process step of capturing and/or securing the free ends of the incoming and outgoing power cables/pipes (e.g. free floating in the sea) is not necessary.

The drawn-in ends of the incoming and outgoing power cables/pipes are continuous with each other, including in particular the end of the incoming power cable/pipe as well as the end of the outgoing power cable/pipe. Further, it includes situations where the incoming and outgoing power cables/pipes are bent, substantially bent and/or curved at their continuous ends. This may include damage to the incoming and outgoing power cables/pipes at their ends due to bending and/or buckling processes.

According to a further embodiment, pulling the ends of the incoming and outgoing power cables or the incoming and outgoing tubes into the offshore wind turbine device comprises bending the incoming and outgoing power cables or the incoming and outgoing tubes relative to each other at their continuous ends.

By bending the incoming and outgoing power cables/pipes at their continuous ends with respect to each other, they can be better fitted through openings in (the foundation of) the offshore wind turbine device. For example, they may fit through openings having a diameter of less than 1 meter, preferably less than half a meter. Further, they may be better pulled through the interior of (the foundation of) the offshore wind turbine device.

The incoming and outgoing power cables/pipes are folded towards each other, for example. The bending may comprise a substantial bending such that the lead-in and lead-out power cables/pipes of the bending are partly parallel to each other and/or the angle between them is an acute angle, an angle smaller than 45 degrees, an angle smaller than 30 degrees and/or an angle smaller than 15 degrees.

According to a further embodiment, pulling the ends of the incoming and outgoing power cables or the incoming and outgoing tubes into the offshore wind turbine device comprises connecting a pulling head with the ends of the incoming and outgoing power cables or with the ends of the incoming and outgoing tubes.

By having a pulling head, pulling can be performed more easily.

The traction head is connected to the ends of said incoming and outgoing power cables/pipes, for example by means of a crane and/or a robotic arm of the subsea vehicle. Before connecting the pulling head with the ends of said incoming and outgoing power cables/pipes, the pulling head is connected, for example, with a hoist cable acting as a pulling rope.

The traction head can also have a bending function. For example, by attaching and pulling a pulling head with a bending function to the incoming and outgoing power cables/pipes, the incoming and outgoing power cables/pipes are folded over each other and then pulled towards and into the wind turbine arrangement in the folded state.

According to a further embodiment, the method comprises, after the pulling step, a step of cutting the incoming and outgoing power cables or the incoming and outgoing pipes inside the offshore wind turbine device at the continuous end of the incoming and outgoing power cables or the incoming and outgoing pipes.

By cutting the incoming and outgoing power cables/pipes inside the offshore wind turbine installation, the incoming and outgoing power cables/pipes can be cut more easily. In particular, they can be cut in a dry and shielded environment. In particular, they can be cut without using any subsea and/or underwater vehicles. The cutting of the incoming and outgoing power cables/pipes may comprise cutting off any part of the cable/pipe that has been damaged by the attachment of a pulling head and/or the bending process.

According to a further embodiment, the method comprises the steps of:

installing a power cable or pipe on or in the seabed by means of a subsea vehicle, an

Providing an additional length of the power cable or tube proximate to the offshore wind turbine arrangement, the additional length forming the incoming and outgoing power cable or the incoming and outgoing tube.

The power cable or pipe is lowered, for example, from sea level, wherein the supply of the rolled up power cable or pipe is provided by a support vessel.

The power cable or pipe is installed on or in the seabed along a main installation path, for example by laying it on or burying it into the seabed by means of a subsea vehicle.

The provided extra length forms the incoming and outgoing power cables/pipes configured to cover paths to and from the offshore wind turbine arrangement and the interior of the offshore wind turbine arrangement from the primary installation path.

Advantageously, providing an extra length of said power cable/pipe at the site close to the offshore wind turbine device enables the installation of a single continuous power cable/pipe. During the provision of the extra length, the support vessel providing the power cable/pipe may slow down or may increase the feeding speed of the power cable/pipe.

Said step of providing an extra length of power cable/pipe is for example partly performed before said step of pulling said incoming and outgoing power cable/pipe into the offshore wind turbine unit. For example, the subsea vehicle pays out the first portion of the additional length. The first part forms, for example, the drop power cable/tube. The extra length of the second section is then provided by pulling this first section while continuing to unwind the cable/pipe from the support vessel. The second part forms, for example, the outgoing power cable/pipe.

In the case of a pipe, in particular an empty pipe filled with air, the extra length (e.g. a first part of the extra length) given off by the subsea vehicle before towing may float in the sea water, forming for example a loop.

In the case of power cables, the extra length paid out by the subsea vehicle before towing may be sunk to the seabed. In several embodiments, buoyancy means may be attached to the power cable.

According to a further embodiment, the extra length of the power cable or pipe is provided by lifting a settler of a subsea vehicle.

The settler is for example movably and/or pivotably supported by a main frame of the subsea vehicle such that it can be moved up and down and/or pivoted up and down. The movement/pivoting of the settler may be controlled remotely, for example. Thus, the extra length can be easily (e.g. automatically) provided.

According to a further embodiment, the additional length of the power cable or pipe is provided by rotating a settler wheel of a settler of a subsea vehicle.

Rotating the settler wheel allows for a better payout of the extra length.

The settler comprises settler wheels and e.g. pivoting members. The settler wheels are rotatably supported, for example, by the pivot member. The pivoting member is pivotally supported, for example by a main frame or plow of the subsea vehicle. For example guiding the power cable/pipe along and below the pivoting member and the settler wheel. For example by pivoting the pivoting member upwards to lift the settler.

According to a further embodiment, the power cable or pipe is installed on or in the seabed by forming a sea ditch in the seabed and laying the power cable or pipe into the sea ditch.

According to a further embodiment, after laying said power cable or pipe into the trench, the trench is buried by means of a subsea vehicle.

According to a further embodiment, the end of the incoming and outgoing power cable or the incoming and outgoing pipe is pulled into the offshore wind turbine device by means of a hoist cable acting as a pulling rope.

The use of messenger cables allows better pulling in of the ends of the incoming and outgoing power cables/pipes, in particular because they can be very heavy.

According to a further embodiment, one end of the hoist cable is mounted inside the offshore wind turbine arrangement and the other end of the hoist cable is provided outside the offshore wind turbine arrangement and below sea level, before the power cable or pipe is mounted on or in the sea bottom by means of the subsea vehicle.

By having the other end of the hoist cable provided outside the offshore wind turbine arrangement, the other end of the hoist cable is put in place and ready for connection with said incoming and outgoing power cables/pipes when the subsea vehicle is driven through.

The end portions of the hoist cables for several adjacent offshore wind turbine arrangements are provided at the outer side of the several adjacent offshore wind turbine arrangements, over which the subsea vehicle may drive for connecting the end portions of the hoist cables with the power cables/pipes.

One end of a hoist cable installed inside the offshore wind turbine device is connected to a pulling device (such as a winch), for example. The winch may be configured to wind up the hoist cable, thereby pulling the ends of the incoming and outgoing power cables/pipes into the wind turbine installation.

The other end of the hoist cable is provided outside the offshore wind turbine arrangement, for example by means of an additional underwater vehicle. The other end of the hoist cable may be connected to the towing head, for example by an additional underwater vehicle.

According to a further embodiment, the other end of the hoist cable is provided with a buoyancy device.

Thus, the other end of the hoist cable will float in the sea, e.g. slightly above the sea bottom. Thus, the hoist cable can be more easily connected with the incoming and outgoing power cables/pipes.

According to a further embodiment, the end of the incoming and outgoing power cable or the end of the incoming and outgoing pipe is pulled into the offshore wind turbine device up to a height above sea level.

The end is for example pulled up to a platform above sea level.

According to a further aspect, there is provided a subsea vehicle for carrying out at least one step of the previously described method. The subsea vehicle comprises:

-a main frame,

-a skid for sliding on the seabed, the skid being fixed to the main frame,

-a plough for forming a sea ditch in the sea floor, the plough being fixed to the main frame,

-a burying device for burying the sea trench after power cables or pipes supplied by a vessel have been laid in the sea trench,

-a pivotable and rotatable settler for pressing down the power cable or pipe in the sea trench before burying the power cable or pipe and for providing an extra length of the power cable or pipe at the offshore wind turbine installation by lifting the settler, the extra length forming the incoming and outgoing power cables or incoming and outgoing pipes of the offshore wind turbine installation, wherein the settler comprises a settler wheel rotatably supported by the pivot member, and a pivot member pivotably supported by the main frame or plough, and

-a robot arm for gripping a hoist cable acting as a pulling rope and securing the hoist cable to the power cable or pipe, the robot arm being secured to the main frame.

The embodiments and features described with reference to the method of the invention are applicable to the subsea vehicle of the invention with necessary modifications in detail.

Other possible embodiments or alternative solutions of the invention also include combinations of features not explicitly mentioned herein above or below with respect to the examples. Those skilled in the art may also add individual or isolated aspects and features to the most basic form of the invention.

Drawings

Other embodiments, features and advantages of the invention will become apparent from the subsequent description and the dependent claims, considered in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a wind farm with wind turbines according to an embodiment;

FIG. 2 illustrates a subsea vehicle installing a pipe in the seafloor while approaching one of the wind turbines of FIG. 1, in accordance with an embodiment;

FIG. 3 shows another view of the subsea vehicle of FIG. 2;

FIG. 4 illustrates how the subsea vehicle of FIGS. 2 and 3 provides an additional length of pipe proximate to the wind turbine of FIG. 2, according to an embodiment;

FIG. 5 shows a detailed view of FIG. 4 with the pulling head with hoist cable attached to the extra length of pipe;

FIG. 6 shows a detailed view of the traction head of FIG. 5 in an initial position;

FIG. 7 shows a detailed view of the traction head of FIG. 5 in an activated position;

FIG. 8 shows a view similar to FIG. 5, but with the traction head in the activated state of FIG. 7;

FIG. 9 illustrates how the additional length of the tube forming the lead-in and lead-out tubes of the wind turbine of FIG. 2 is drawn into the wind turbine according to an embodiment; and is

Fig. 10 shows a flow diagram illustrating a method of offshore installation of a power cable or a pipe for a power cable (such as the pipes of fig. 2 and 4-9) for the wind turbine of fig. 2, according to an embodiment.

In the drawings, like reference numerals refer to similar or functionally equivalent elements, unless otherwise specified.

Detailed Description

Fig. 1 shows an offshore wind farm 1 according to an embodiment. The offshore wind park 1 comprises several offshore wind turbines. As an example, in fig. 1 an offshore wind turbine 2 and a further offshore wind turbine 3 of a wind park 1 are shown.

Each of the wind turbines 2 and 3 comprises a rotor 4, the rotor 4 being connected to a generator (not shown) arranged inside a nacelle 5. A 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 mono-pile or a tri-pile. The base 7 is connected to and/or driven into the seabed 8. The seawater is indicated by reference numeral 9.

During operation of the wind turbines 2, 3, kinetic energy of the wind is converted into electrical energy by a generator in the nacelle 5. The power generated in the generator is transmitted via internal power cables to a switching device (not shown) in the lower part of the tower 6. The generated power is transmitted from the switchgear to a hang-off zone (hang-off zone)10 in the lower part of the tower 6 via another internal power cable (not shown). For the electrical connection forward from the suspension area 10, a power transmission device is required to connect the internal power cables of the wind turbine 2 to another offshore device, such as the wind turbine 3.

In the following, an improved method for offshore installation of a power cable or a pipe for a power cable of a wind turbine installation is described with respect to fig. 2 to 10.

In step S1 of the method, a hoist cable 11 (fig. 2) is provided at the wind turbine 2. One end 39 of the hoist cable 11 is connected to a winch 12 arranged at the suspended platform 10 of the wind turbine 2. From there, the hoist cable 11 is unwound from the winch 12 and guided through the lower part of the tower 6 and the inside of the foundation 7. The hoist cable 11 is guided through the opening 13 to the outside of the wind turbine 2. Outside the wind turbine 2, a remotely operated underwater vehicle (ROV, not shown) lowered from a first vessel (not shown) connects the hoist cable 11 at its other end 40 to the tractor head 14 (fig. 2). The ROV also connects a buoyancy device 15 (such as an inflatable balloon) to the tractor head 14. Buoyancy means 15 cause the towing head 14 to float above the sea floor 8. The ROV positions the tractor 14 close to the main installation path 16 of the pipe 17 (instead of the pipe 17, a power cable may be provided) so that the hoist cable 11 with the tractor 14 is brought into position for the pipe 17 to the next step.

In step S2, the pipe 17 is installed in the seabed 8 by means of the subsea vehicle 18. At the beginning of the installation path 16, for example, at a first offshore wind turbine along the installation path 16, the subsea vehicle 18 has been lowered from a support vessel (not shown). The subsea vehicle 18 is towed by a support vessel at a towing yoke 19. The traction yoke 19 is part of the main frame 38 of the subsea vehicle 18. By the towing of the vessel, the subsea vehicle 18 slides along the installation path 16 over the base of the seafloor 8 on a skid 20.

The subsea vehicle comprises a plow 21, as best seen in fig. 3. Plow 21 is secured to main frame 38 of subsea vehicle 18. The plow 21 opens a sea ditch 22 (fig. 2) in the sea floor 8 by the towing of the vessel at the towing yoke 19. The pipe 17 is continuously unwound from a winch on a support vessel (not shown) and laid into the sea chest 22. In particular, the subsea vehicle 18 comprises a settler 23 (fig. 3), which settler 23 can be pivoted downwards to force the pipe 17 into the sea ditch 22 (fig. 2). The pipe 17 laid into the sea ditch 22 is buried by the roller cutters 24 of the subsea vehicle 18. The process of continuously forming a sea ditch 22, laying the pipe 17 in the sea ditch 22, and burying the pipe with the roller cutter 24 is carried out until the subsea vehicle 18 reaches a location along the installation path 16 that is close to (e.g., closest to) a wind turbine, such as wind turbine 2.

In step S3, an extra length 25 of pipe 17 is provided at the installation path 16 close to the wind turbine 2 (fig. 4). The extra length 25 is provided by means of a settler 23.

The settler 23 comprises e.g. settler wheels 26 and pivoting members 27 (fig. 3). The settler wheels 26 are rotatably supported, for example, by a pivot member 27. The pivoting member 27 is pivotably supported by the plow 21, for example.

With the pivoting member 27 pivoted downwardly (fig. 2), the settler 23 is used in step S2 to press the pipe 17 down in the sea ditch 22 before burying the pipe 17. With the pivoting member 27 pivoted upwardly (fig. 4, 5, 8, 9), the settler 23 is used in step S3 to provide additional length 25 of pipe 17.

In step S3, first, a support vessel, such as a towing subsea vehicle 18, slows its speed. Further, the settler 23 is lifted by pivoting the pivoting member 27 upwards (fig. 4). When the tube 17 is filled with air, it floats upwards, as far as the upward-lifting settler 23 permits. In the raised condition of the settler 23, the pipe 17 is continuously supplied by the support vessel, discharging parts of the pipe 17 in the form of loops 28. The discharge of the pipe 17 is further supported by the rotation of the settler wheels 26.

The loop 28 shown in fig. 4 represents, for example, a first portion 29 of the extra length 25. This first portion 29 is towed, for example, by the continuous supply of support vessels in conjunction with the pipe 17 in the next step S4, providing the second portion 30 of the extra length 25 (fig. 9).

The extra length 25 (including, for example, the first and second portions 29, 30) is used to form an inlet duct 31 and an outlet duct 32 of the wind turbine 2. When the installation of the pipe 17 at the wind turbine 2 is to be completed, the lead-in pipe 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 suspended platform 10 of the wind turbine 2. Furthermore, in the completed state, the exit tube 32 will cover the return path from the hanging platform 10, through the opening 13 and back to the primary installation path 16.

In step S4, the end 33 of the inlet pipe 31 and the end 34 of the outlet pipe 32 are simultaneously pulled into the wind turbine 2 (fig. 9).

To carry out step S4, first, the robotic arm 35 of the subsea vehicle 18 grasps the tow head 14 (fig. 5), the tow head 14 having been previously provided at the correct position for grasping in step S1. The robotic arm 35 moves the tractor 14 toward the paid-out excess length 25 of the tube 17 and attaches it thereto. The location of the extra length 25 where the tractor 14 attaches to the tube 17 marks in this example the transition between a first portion 29 of the extra length 25 (which will form the inlet tube 31) and a second portion 30 of the extra length 25 (which will form the outlet tube 32).

The traction head 14 has a bending function. The pulling head 14 comprises two arms 36, which arms 36 can be lowered to bend the additional portion 25 of the tube 17 (fig. 6, 7). Further, the traction head 14 comprises an intermediate portion 37, at which intermediate portion 37 the hoist cable 11 may be attached (fig. 7). When the tractor 14 is attached to the extra length 25 of the tube 17, the two arms 36 are attached at two spaced apart locations on the extra length 25 (fig. 6). This means that one arm 36 of the drawing head 14 is attached to the first part 29 of the extra length 25 forming the inlet tube 31. The other arm 36 of the tractor 14 is attached to the second portion 30 of the extra length 25 that forms the exit tube 32. By pulling the intermediate part 37 by means of the hoist cable 11, the arm 36 is lowered and the part 29 of the extra length 25 forming the lead-in pipe 31 and the part 30 of the extra length 25 forming the lead-out pipe 32 are bent relative to each other (fig. 7, 8).

After attaching the traction head 14 to the lead-in and lead-out pipes 31, 32, the hoist cable 11 is pulled into the wind turbine 2 (fig. 9) by rolling up the winch 12 (fig. 2). Thus, the ends 33, 34 of the lead-in and lead-out pipes 31, 32 are drawn towards the base 7 of the wind turbine 2 and through the opening 13 in the base 7. The ends 33, 34 of the lead-in and lead-out pipes 31, 32 are drawn further upwards inside the foundation 7 and, for example, also inside the tower 6. The ends 33, 34 of the lead-in and lead-out pipes 31, 32 are drawn up to the suspended platform 10 (fig. 2), for example.

In step S5, the lead-in and lead-out pipes 31, 32 are cut inside the wind turbine 2, for example at the suspended platform 10. In particular, the portions of the lead-in and lead-out tubes 31, 32 damaged by the bending process are cut away (fig. 7).

In a further process, power cables (not shown) may be inserted into the cut lead-in and lead-out tubes 31, 32 for electrical connection of the wind turbine 2.

By the described method, the installation of the tube 17 for the power cable can be efficiently installed for several wind turbines of a wind park, such as the wind turbines 2, 3 of the wind park 1 shown in fig. 1. Advantageously, the subsea vehicle 18 is lowered only once from the vessel for connecting several wind turbines. Further, the subsea vehicle 18 continuously travels along the main installation path 16 and provides an extra length 25 of pipe 17 close to each wind turbine (such as wind turbines 2, 3). At this point, at each wind turbine (such as wind turbines 2, 3), the tow head 14 with hoist cable 11 is ready for connection with the extra length 25. As soon as the extra length 25 forming the lead-in and lead-out pipes 31, 32 is provided by the subsea vehicle 18 at a certain wind turbine, it is automatically connected with the tractor head 14 and is pulled into the base 7 of the wind turbine 2, 3. Inside the wind turbine, the lead-in and lead-out pipes 31, 32 may be cut in a dry and shielded environment.

While the invention has been described in terms of preferred embodiments, it will be apparent to those skilled in the art that modifications are possible in all embodiments. In particular, instead of the tube 17, the power cable can also be installed directly by the described process steps. In this case, the power cable is buried directly in the sea floor 8 between the locations of the wind turbines 2, 3 by a subsea vehicle 18. Further, an extra length of said power cable is provided at each of the wind turbines (such as wind turbines 2, 3). This extra length is then towed as incoming and outgoing power cables into the respective wind turbines by means of the towing head 14, the robot arm 35 and the hoist cable 11.