Offshore structure

Abstract

A system and corresponding method for connecting a cable (10) to an offshore structure (100); the offshore structure comprises a routing unit (102) for the cable; the routing unit is movably attached to the offshore structure between at least two positions relative to the offshore structure; furthermore, the system comprises an actuator (300) adapted to selectively move the routing unit between at least two positions relative to the offshore structure; the at least two positions comprise a first position, in which the routing unit is completely above sea level (40) allowing for connection of the cable and a lower end of the routing unit is accessible from the offshore structure; and a second position, relatively lower than the first position, in which the lower end of the routing unit is in a normal installed position relative the offshore structure. The offshore structure may include a hang off balcony 510 (Figure 5), the routing unit may be moved to a third position adjacent the hang of balcony. A zip line 540 may transfer the cable between a vessel 520 and the offshore structure (Figure 4).

Description

Technical Field The present disclosure relates to a system for connecting a power cable to an offshore structure and to a method for installing the power cable to the offshore structure. The present disclosure relates generally to the field of offshore wind and wave power. More specifically, the present invention describes a system, and method for guiding, via a routing unit, a power cable to an offshore structure, such that the power cable is protected and in a position to be electrically connected to the offshore structure. Background In wind farms positioned offshore, power cables or inter array power cables are used to transport the energy generated at the different wind mills positioned around at the offshore location to an export cable for transfer of the power to shore. Power cables are also used for other renewable energy productions sites or for oil and gas structures offshore. Due to the offshore location the power cables extend in normal operation from a position at top off an offshore structure and down into the water and are extending in the water or at the seabed to another location. l-tubes or J-tubes are normally used for guiding and protecting the power cables as they extend from the body of water and up to an offshore structure. These tubes are fixed to the offshore structure and extend normally from the offshore structure and down into the body of water. How to install the power cable so that it runs through these tubes is a technical challenge. To install a power cable, the one end of the power cable would have to be inserted in the to l / J-tube at the relative bottom end of the l / J-tube which is below sea level, giving a need to have a water resistant end connection of the cable and additional equipment as bend restrictors or similar as it would have to be moved through the body of water for installation. Additionally the normally installation procedure would also involve wet parking of the end of the cable at the seabed for thereafter pulling it up and into the l / J-tube. It is a problem how to get a power cable to an offshore structure and how to connect it to the offshore structure in a cost effective and safe way. A preference would be to avoid having to operate below the sea surface. It is desirable to avoid using wet mate connectors, because such connections are a more complicated and relatively expensive in comparison to dry mate connectors. Furthermore, installing the power cables to the offshore structure when in shallow waters becomes difficult since the power cable may be scratched by the seabed during installation. Such damages is especially difficult to avoid the further the tubes extend below the sea surface. Aspects of the present disclosure seek to provide a system and method for overcoming these problems. In particular, the present invention aims to provide an arrangement to install a cable to an offshore structure at a raised elevation such that the connection is in a dry state. Summary It is an objective of the present invention to provide a system for connecting a power cable to an offshore structure, and a method for installing a power cable to an offshore structure. This objective can be achieved by the features as defined by the independent claims. Further enhancements are characterized by the dependent claims. The invention is defined by the claims. According to a first aspect of the present invention, there is provided a system for connecting a power cable to an offshore structure. The offshore structure comprises a routing unit for the power cable such that the power cable is protected and in a position to be electrically coupled to the offshore structure, or to components on the offshore structure. The routing unit is movably attached to the offshore structure between at least two positions relative to the offshore structure. The system further comprises an actuator adapted to selectively move the routing unit between a first position in which the routing unit is completely above sea level, where a relative lower end of the routing unit is accessible from the offshore structure; and a second position, relatively lower than the first position, in which the lower end of the routing unit is in a normal installed position, or normal operation position, relative the offshore structure. This allows the connection to be done with the end of the power cable being above sea level. That the relative lower end is accessible from the offshore structure should be understood such that it is possible to perform work close to or on the lower end of the routing unit from a deck positioned at the offshore structure. This means that the work with possibly connecting a bend restrictor to the routing unit can be done above sea level in dry conditions, i.e not seawater influenced conditions. The routing unit may be movably relative to the offshore structure between a plurality of predetermined positions, wherein the predetermined positions comprises the first position and the second position. The first position may be further defined such that the lower end of the routing unit is accessible to a worker on the offshore structure, for example a worker on a ground level of the offshore structure, or on a hang off balcony on the offshore structure. This may be the position at which the worker connects the cable to the offshore structure, before arranging the cable and the routing unit in their final position that they have during normal subsequent operation of the offshore structure. The first position may be substantially spaced from the second position. Preferably, a lower end of the routing unit is proximate to the sea level in the second position. The lower end of the routing unit may be at least partially below sea level in the second position. The lower end of the routing unit may be above, but proximate to, the sea level in the second position. The second position is normally not accessible from the offshore structure as such. Preferably, the offshore structure further comprises a hang off balcony extending from the offshore structure to a free end spaced from the offshore structure. The hang off balcony may be substantially parallel to the sea level. A lower end of the routing unit may be moveable to a third position, the third position being proximate to and above the hang off balcony. The power cable may be attachable to the hang off balcony. If a third position is provided, an actuator may be further configured to move the routing unit from the third position to the first or second positions. The hang off balcony may further operate as an elevated working platform to allow a worker to access and service the offshore structure and / or power cable when the routing unit is held in the first or third position. Optionally, the system comprises a hoisting device. The hoisting device may be arranged on the offshore structure. Furthermore, the hoisting device may comprise a pulling element attachable to the first end of the power cable, and configured to pull the power cable through the routing unit. The system may further comprise a transfer apparatus configured to move the power cable to the offshore structure. The transfer apparatus might be a vesselbased crane or a zip line arrangement between the vessel and the offshore structure. The transfer apparatus may be further configured to align the power cable such that the power cable is proximate and vertically below an opening at the lower end of the routing unit. The transfer apparatus may be a zip line arrangement having a zip line cable extending between a first connection on the offshore structure at a position proximate and above the hang off balcony, and a second connection positioned on a vessel. The zip line arrangement may further comprise a cable mounting device on the zip line cable, the cable mounting device configured to receive the power cable. The first connection may comprise a driving arrangement configured to move the first connection along a vertical length of the offshore structure. The routing unit may be selected from a group consisting of: an l-Tube, a J-Tube, a telescopic tube, a short tube element, a bell mouth, and a connector unit. The offshore structure may be a floating offshore structure, alternatively it could be a bottom fix structure. Preferably, the floating offshore structure comprises a wind turbine, alternatively it may comprise a wave an / or tidal energy power plant, or a renewable energy power plant solution as such where the cable is an energy export cable from the offshore structure. The offshore structure may comprise a supporting post, such that the routing unit is movably attached to the supporting post. The supporting post and the routing unit may each extend parallel to each other in a substantially perpendicular direction to the sea level. According to a second aspect of the invention, there is a method for installing a power cable to an offshore structure. The method comprises: providing a system according to the first aspect of the invention; providing a power cable; activating the actuator to move the routing unit to the first position; connecting the power cable with the offshore structure via the routing unit; and activating the actuator to move the routing unit to the second position. In this way the power cable may be installed to the offshore structure with the installation work being done above the sea level. The step of connecting the power cable to the offshore structure may further comprises the steps of: attaching the pulling element to a first end of the power cable; pulling, via the pulling element, the power cable through the routing unit; and / or advancing the power cable through the routing unit by lowering the routing unit while holding the power cable with the pulling element. The step of providing the power cable may comprises providing the power cable at a vessel spaced from the offshore structure, and may be followed by the step of: transporting, via the transfer apparatus, the first end of the power cable to the third position. The power cable may be transported, via the transfer apparatus, to the first position, rather than the third position. At least one of the above embodiments provides one or more solutions to the problems and disadvantages with the background art. Other technical advantages of the present disclosure will be readily apparent to one skilled in the art from the following description and claims. Various embodiments of the present application obtain only a subset of the advantages set forth. No one advantage is critical to the embodiments. Any claimed embodiment may be technically combined with any other claimed embodiment or embodiments. Brief Description of the Drawings The accompanying drawings illustrate presently exemplary embodiments of the disclosure and serve to explain, by way of example, the principles of the disclosure. FIG. 1 is a schematic of an offshore structure according to one embodiment of the disclosure in a first position completely above sea level, and a transfer apparatus. FIG. 2 is a detailed view according to one embodiment of the disclosure of a hoisting device arranged on the offshore structure; FIG. 3 is a detailed view according to one embodiment of the disclosure of an actuator arranged on the offshore structure; FIG. 4 is a schematic according to one embodiment of the disclosure of a transfer apparatus; FIG. 5 is a detailed view according to one embodiment of the disclosure of the offshore structure in the first position; FIG. 6 is a detailed view according to one embodiment of the disclosure of a load transfer between the transfer apparatus and offshore structure; FIGs. 7A and 7B are detailed views according to embodiments of the disclosure of a power cable connecting to a hoisting device; FIG. 8 is a detailed view according to one embodiment of the disclosure of the offshore structure in a third position; FIGs. 9A and 9B are detailed views according to embodiments of the disclosure of the power cable being pulled through the routing unit; FIG. 10 is a schematic according to one embodiment of the disclosure of the offshore structure with the routing unit in a second position; and FIG. 11 is a schematic view according to one embodiment of the disclosure with the routing unit being a bell mouth. Detailed Description Embodiments of the present description provide a system for connecting a power cable to an offshore structure and method for installing a power cable to an offshore structure. The figures illustrate schematic exemplary embodiments and this detailed description describes in detail several ways of carrying out the system and method by referring to the figures and examples. The system as shown in FIG. 1 comprises an offshore structure 100 having a moveably attached routing unit 102, the routing unit 102 may be a guide unit 102. The offshore structure 100 is provided with a power cable 10 having a first portion of length arranged vertically along the offshore structure 100, and a second portion of length deviating out of the offshore structure 100 into a body of water and eventually laying on a sea bed. The power cable 10 may have a first portion of length extending between an upper end of the routing unit 102 to a lower end of the routing unit 102, and a second portion of length extending between a lower end of the routing unit 102 to below a sea level 40. A first end 12 of the power cable 10 may be connected to the offshore structure 100. The routing unit 102 serves to guide the power cable 10 from the body of water to the offshore structure 100, such that the power cable 10 is in position to be electrically connected to the offshore structure 100. Electrically connecting to the offshore structure 100 may also include connections to one or more electrical components on the offshore structure. The offshore structure 100 may further comprise a windmill 30, such that the offshore structure 100 forms part of a power distribution system that facilitates the transmission of electricity from the windmill 30 to various components. The offshore structure 100 may comprise other types of energy generators, such as for example a wave, tidal, and / or wind generator. The offshore structure 100 may comprise any suitable structure for generating electricity to which the first end 12 of the power cable 10 may be connected. As illustrated, the routing unit 102 may be moveably attached to a supporting post 101, with the routing unit 102 and supporting post 101 each extending parallel to one another in a direction substantially perpendicular to a sea level 40. Initially, the routing unit 102 may be held in a first position defined as where the routing unit 102 is completely above the sea level 40, and preferably substantially spaced from the sea level 40. The first position may be accessible to a worker from an elevated platform 510, such as for example a hang off balcony 510, on the offshore structure 100. In the first position, the lower end of the routing unit 102 may be accessible to a worker from an elevated platform 510, such as for example a hang off balcony 510, on the offshore structure 100. The routing unit 102 may be a generally hollow body structured to protect the power cable 10 and route the power cable 10 inside the routing unit 102 to the offshore structure 100. To further protect the power cable, a bend stiffener 20 may be provided towards the first end 12 of the power cable 10. The bend stiffener 20 may be formed with an elongate sleeve defining a substantially cylindrical passage which can receive at least a portion of the power cable 10. The bend stiffener 20 may be provided with a bend stiffener connector removably connectable to the routing unit 102. As illustrated, the routing unit 102 comprises an l-Tube having a flange attachable with the bend stiffener connector. However, other types of tubes with an appropriate connecting means to the power cable directly, or via a bend stiffener connector 20, such as a J-Tube, a telescopic tube, a short tube element, a bell mouth, and a connector unit. As illustrated in the figures, the offshore structure 100 is provided with an actuator 300 adapted to selectively move the routing unit 102 relative to the offshore structure 100 between a plurality of predetermined positions. The plurality of positions may comprise at least a first position, wherein the routing unit 102 is completely above sea level, see for example FIG. 1; and a second position, lower than the first position. The second position may be, for example, proximate to the lower end of the offshore structure 100. The second position may be, for example, proximate to the sea level. For example, the second position may be proximate yet above the sea level 40. For example, the second position may be proximate yet below the sea level 40. For example, the lower end of the routing unit 102 may be at an elevation at least partially below the sea level, see for example FIG. 10. The second position may be the position that the routing unit 102 have after the power cable 10 has been fully installed and the offshore structure is operating and generating electric power and transporting the electric power via the power cable 10. The first position may be defined by that the lower end of the routing unit 102 being accessible to a worker from a level of the offshore structure 100. The level may be a hang off balcony or other a platform on which a worker electrically connects the power cable 10 to the offshore structure 100. The first position may be substantially spaced from the second position. Attaching the power cable 10 to the offshore structure 100 when the routing unit is held in the first position provides the technical benefit of being able to deploy a dry-mate connection, rather than a wet mate connection. By having the routing unit 102 in the first position the power cable 10 may be protected from damages by being dragged on the sea bed when the offshore structure 100 is in relatively shallow water. FIG 2. illustrates a detailed view of the offshore structure 100 provided with a hoisting device 400. The hoisting device may be winch, such as for example a pull-in winch and gantry. Sections of the routing unit 102 have been removed from the illustration for clarity purposes. The hoisting device may be arranged on the offshore structure 100, or on the routing unit 102, and may comprise a frame 410 removably mounted to the offshore structure 100, or to the routing unit 102. A rotatable drum 420 having a wire 432 wound thereon may be positioned on an upper end 412 of the frame 410. The wire 432 hangs downwardly due to gravity, and can extend into and along the entire length of the routing unit 102, such that a wire end 434 terminates below an opening at the lower end of the routing unit 102. The wire end 434 is attachable to the first end 12 of the power cable 10. The hoisting device 400 may reel in the wire 432, such an attached power cable 10 is pulled towards the frame 410. The hoisting device 400 may be coupled to a controller, such that the hoisting device 400 is remotely operable. The rotatable drum 420 may further comprise a motor configured to reel the wire end 434 towards, or away from the upper end of the routing unit 102. The hoisting device 400 may be operable to pull a first end 12 of the power cable 10 into and through the opening in the routing unit 102, thereby making the power cable 10 at least partially protected by the routing unit 102. The hoisting device 400 is further operable to lower the power cable 10 back through the routing unit 102 until the wire 432 emerges at an opening at the lower end of the routing unit 102. FIG. 3 illustrates a detailed view of the routing unit’s 102 lower end, and details an example of the actuator 300 arranged on the offshore structure 100. FIG. 3 may illustrate the first position proximate to the hang off balcony 510. A side of the routing unit 102 adjacent to the supporting post 101 may be provided with a bracket 310 having a rack profile 312 extending along the length of the routing unit 102. A motor-driven toothed wheel 320 may be rotatably mounted on the routing unit 102 and forms an interlocking mesh with the corresponding teeth of the rack profile 312. The bracket 310 is further provided with a guide roller 330 extending from the bracket 310 and contacting the supporting post 101. The toothed wheel 320 is designed to rotate, via power supplied by the motor, to move the routing unit 102 relative to the supporting post 101. Alternatively, the bracket 310 can be provided on the supporting post 101, with the wheel 320 provided on the routing unit 102. The actuator 300 and hoisting device 400 discussed herein are examples of a means structured to provide a relative movement between the routing unit 102 and the power cable 10. The means may be further configured to rotate the routing unit 102 around an axis parallel to the sea level 40. This may facilitate the routing of the power cable 10 into the routing unit 102 because the lower end of the routing unit 102 can be swung around an axis parallel to the sea level 40. The offshore structure may be further provided with a locking means for locking a relative movement between the routing unit 102 and the power cable 10. The locking means may comprise any known apparatus suitable to selectively restrict movement between the two components, such as a retractable tab and a receiving slot arranged on the first end 12 of the power cable 10 and the routing unit 102 respectively. The locking means may be for example a wedge, or a clamp, or a holder. The relative movement provided by means 300, 400, structured to provide the relative movement, and prevented by the locking means is in reference to a substantially vertical relative movement between the guide unit 102 and power cable 10. Alternatively, the relative movement may be in a direction along the longitudinal length of the guide unit 102. There may, however, be an additional horizontal relative movement between the power cable 10 and the guide unit 102 due to wind and / or tidal forces. While the present invention can provide / prevent a relative movement vertically or in a direction of the guide unit 102, the power cable 10 may still be capable of being displaced horizontally inside the guide unit 102 such that a part of the power cable 10 is engageable with the guide unit 102. FIG. 4 illustrates an arrangement designed to allow the power cable 10 to be positioned and readily attachable to the offshore structure 100. This is done without the first end 12 of the power cable 10 coming in contact with the seawater. A hang off balcony 510 may be provided at a third position. The third position may be the same as, or proximate to, the first position. The third position may be proximate and vertically below the first position. The third position is completely above the sea level 40. The hang off balcony 510 may extend towards free-end remote from the offshore structure 100 in an orientation that is substantially parallel to the sea level 40. In the vicinity of the offshore structure 100 there may be a vessel 520, such as a ship, having a vessel post 530. The vessel 520 may carry at least a part of the power cable 10 to be connected to the offshore structure 100. A transfer apparatus 500 may be provided between the vessel 520 and the offshore structure. In FIG. 4 the transfer apparatus 500 comprises a zip line arrangement having a zip line cable 540 extending between two removably attachable connections 501, 502. The first connection 501 is located on the offshore structure 100 and may be positioned proximate and above the hang off balcony 510. The second connection 502 may be positioned directly on the vessel 520, or an appropriate vessel post 530. As illustrated, arranged on the zip line cable 540 is a cable mounting device 550 having a connecting portion removably attachable to the first end 12 of the power cable 12. A cable drive unit may be arranged on the cable mounting device 550, and configured to move the cable mounting device 550 along the zip line 540. The cable drive unit may comprise a motor and a chassis or framework having a modular subassembly of wheels driven by the motor. Furthermore, a zip line drive unit may be arranged on the zip line 540 and configured to pull the zip line 540, such that the cable mounting device 550 mounted thereon can move towards or away from the offshore structure. The transfer apparatus 500 may be structured to move the first end 12 of the power cable 10 from the vessel 520 to the third position, or directly to the first position. Alternatively, rather than positioning the power cable 10 via the transfer apparatus 500, the power cable 10 may be lifted into place, for example by a crane arm / winch. Both the first and second connections 501, 502 may include a driving arrangement structured to move the connections vertically along their corresponding post. Furthermore, the connecting portion of the cable mounting device 550 may be adjustable, such that the connecting portion can extend / retract to raise / lower the power cable 10 relative to the cable mounting device 550. These functionalities allow more precise positioning of the power cable 10 once it is proximate to the offshore structure 100. Any of the cable mounting device 550, first connection 501, second connection 502, zip line drive unit, and cable drive unit may be coupled to a controller such that they are remotely operable. An example operation of the system will now be described in reference to the figures, especially FIGs. 4 to 10. Beginning with FIG. 4, a transfer apparatus 500 having the zip line arrangement is provided, and the power cable 10 is provided on the vessel 520. The first end 12 of the power cable 10 is fixed onto the connecting portion of the cable mounting device 550. The cable mounting device 550 transports the power cable 10 from the vessel 520 to the offshore structure in the first position, denoted by label ‘A’. As depicted in FIGs 5-6, the power cable 10 may then be lowered, via the driving arrangement on the first connection 501 and / or the adjustable connecting portion of the cable mounting device 550, until the power cable 10 is coupled with the hang off balcony 510 via appropriate means, in the third position. This allows the load of the power cable 10 to be transferred from the zip line arrangement to the hang off balcony 510. The first end 12 of the power cable 10 is hereby held in the third position, denoted by label ‘B’. Alternatively, the power cable 10 can be directly provided at the third position by the zip line arrangement. To complete the load transfer, the cable mounting device 550 is detached from the power cable 10. As shown in FIGs. 7A and 7B, the pulling element of the hoisting device 400 is then lowered through the routing unit 102 unit, and secured to the power cable 10. Moving on to FIG. 8, the lower end of the routing unit 102 is secured with a connecting means provided on the power cable 10, such as a bend stiffener connector 20. If the optional hang off balcony 510 is present with the power cable 10 attached thereto, there are alternative steps of activating the actuator 300, moving the routing unit 102 from the first position to the third position, securing the routing unit 102 to the connecting means, and detaching the power cable 10 from the hang off balcony 510. Next, the actuator 300 is (re)activated. As shown in FIG. 9A and 9B, the routing unit 102 is thereby moved downwards relative to the supporting post 101 towards the second position. Simultaneously, or as separate steps, the hoisting device 400 pulls the first end 12 of the power cable 10 through the routing unit 102, until the first end 12 emerges from an opening at the upper end of the routing unit 102. The locking means is activated to prevent further movement of the power cable 10 relative to the routing unit, and the hoisting device 400 is detached from routing unit 100. Finally, the routing unit is held in the second position, see for example FIG. 10, and the power cable 10 is electrically coupled to the offshore structure 100. FIG. 11 is an example system wherein the routing unit 102, shown to be in the first position, is in the form of a bell mouth. The hang off balcony 510 may further operate as a working platform to allow a worker to conveniently access the routing unit 102 and the power cable 10. Since the routing unit 102 is movably attached to the offshore structure 100, the bell mouth can be raised for installation and connection of the power cable 10 and then subsequent lowered into the normal installed position when the offshore structure is normally operating or ready for operation. The power cable 10 may be an electric power cable. However, this disclosure is not limited to only electric power cables. The power cable 10 may be any flexible connecting member used in subsea applications, for example a flexible pipeline, a tension cable, an attachment cable, a communication cable, and / or a chain. The arrangement of the present invention provides numerous advantages over known prior art. A problem with past arrangements is that they require the use of wet mate connectors because the power cables engage with the lower end of the routing units proximate to sea level, thus there is a need for connectors that can operate in underwater conditions. However, wet-mate connectors are relatively expensive in comparison to dry-mate connectors. The present invention provides a means to perform a dry mate connection at a position substantially spaced and vertically above sea level. This is particularly advantageous because dry mating is relatively inexpensive compared to wet mate connections. Furthermore, there is a greater selection of dry mate connectors to choose from, whereas the options when selecting wet mate connectors are more limited. The system and method for transferring the first end 12 of the power cable 10 described herein, as well as the system and method for connecting the power cable 10 to the offshore structure 100 described herein, allow for the transfer and connection to be done completely above the sea level, and in addition allow for the transfer and connection to be done in shallow waters without damaging the power cable on the sea bed. It will be apparent to those skilled in the art that various modifications and variations can be made to the system and method described herein. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed system and method. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.

Claims

1. A system for connecting a power cable (10) to an offshore structure (100), the system comprising a routing unit (102) for the power cable (10) such that the power cable (10) is protected and in a position to be electrically connected to the offshore structure (100);characterised in that:the routing unit (102) is movably attached to the offshore structure (100) between at least two positions relative to the offshore structure (100);and the system further comprises an actuator (300) adapted to selectively move the routing unit (102) between: a first position in which the routing unit (102) is completely above sea level (40), where a relative lower end of the routing unit (102) is accessible from the offshore structure (100); and a second position, relatively lower than the first position, in which the lower end of the routing unit (102) is in a normal installed position relative the offshore structure (100).

2. The system according to claim 1, wherein a lower end of the routing unit (102) is proximate to the sea level (40) in the second position.

3. The system according to any one of the preceding claims,wherein the offshore structure (100) further comprises a hang off balcony (510) extending from the offshore structure (100) to a free end spaced from the offshore structure (100);wherein the hang off balcony (510) is substantially parallel to the sea level (40);wherein a lower end of the routing unit (102) is movable to a third position, the third position being proximate to and above the hang off balcony (510); andwherein the power cable (10) is attachable to the hang off balcony (510).

4. The system according to any one of the preceding claims, wherein the system further comprises a hoisting device (400), the hoisting device (400) having a pulling element attachable to the power cable (10) and configured to pull the power cable (10) through the routing unit (102).

5. The system according to any one of the preceding claims, wherein the system further comprises a transfer apparatus (500) configured to move the power cable (10) to the offshore structure (100), and further configured to align the power cable (10) such that the power cable (10) is proximate and vertically below an opening at the lower end of the routing unit (102).

6. The system according to claim 5, wherein the transfer apparatus (500) is a zip line arrangement having a zip line cable (540) extending between a first connection (501) on the offshore structure (100) at a position proximate and above the hang off balcony (510), and a second connection (502) positioned on a vessel (520); andwherein the zip line arrangement comprises a cable mounting device (550) on the zip line cable (540), the cable mounting device (550) configured to receive the power cable (10).

7. The system according to claim 6, wherein the first connection (501) comprises a driving arrangement configured to move the first connection (501) along a vertical length of the offshore structure (102).

8. The system according to any one of the proceeding claims, wherein the routing unit is selected from a group consisting of: an l-Tube, a J-Tube, a telescopic tube, a short tube element, a bell mouth, and a connector unit.

9. The system according to any one of the preceding claims, wherein a bend stiffener (20) is attachable to the power cable (10), and / or wherein the bend stiffener (20) is attachable to the routing unit (102).

10. The system according to any one of the preceding claims, wherein the second position of the routing unit (102) is at least partially below sea level (40).

11. The system according to any one of the preceding claims, wherein the offshore structure (100) is a floating offshore structure (100), and optionally wherein the floating offshore structure comprises a wind turbine (30).

12. The system according to any one of the preceding claims, wherein the offshore structure (100) further comprises a supporting post (101);wherein the routing unit (102) is movably attached to the supporting post (101); andwherein the supporting post (101) and the routing unit (102) each extend parallel to each other in a substantially perpendicular direction to the sea level (40).

13. A method for installing a power cable (10) to an offshore structure (100), the method comprising:providing a system according to any one of the preceding claims;providing a power cable (10);activating the actuator (300) to move the routing unit (102) to the first position;connecting the power cable (10) with the offshore structure (100) via the routing unit (102); andactivating the actuator (300) to move the routing unit (102) to the second position.

14. The method according to claim 13 when providing a system according to claim 4, wherein the step of connecting the power cable (10) to the offshore structure (100) via the routing unit (102) further comprises the steps of:attaching the pulling element to a first end (12) of the power cable (10); andpulling, via the pulling element, the power cable (10) through the routing unit (102); and / oradvancing the power cable (10) through the routing unit (102) by lowering the routing unit (102) while holding the power cable (10) with the pulling element.

15. The method according to claim 13, when providing a system according to claim 5 or 6, wherein providing the power cable (10) is followed by the step of:transporting, via the transfer apparatus (500), the first end (12) of the power cable (10) to the third position.AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS:16Claims1. A system for connecting a power cable (10) to an offshore structure (100), the system comprising a routing unit (102) for the power cable (10) such that the power5 cable (10) is protected and in a position to be electrically connected to the offshore structure (100);characterised in that:the routing unit (102) is tubular and movably attached to the offshore structure (100) between at least two positions relative to the offshore structure (100);10 and the system further comprises an actuator (300) adapted to selectivelymove the routing unit (102) between: a first position in which the routing unit (102) is completely above sea level (40), where a relative lower end of the routing unit (102) is accessible from the offshore structure (100); and a second position, relatively lower than the first position, in which the lower end of the routing unit (102) is in a15 normal installed position relative the offshore structure (100).Cd2. The system according to claim 1, wherein a lower end of the routing unit (102) is proximate to the sea level (40) in the second position.20 3. The system according to any one of the preceding claims,wherein the offshore structure (100) further comprises a hang off balcony (510) extending from the offshore structure (100) to a free end spaced from the offshore structure (100);wherein the hang off balcony (510) is substantially parallel to the sea level25 (40);wherein a lower end of the routing unit (102) is movable to a third position, the third position being proximate to and above the hang off balcony (510); and wherein the power cable (10) is attachable to the hang off balcony (510).30 4. The system according to any one of the preceding claims, wherein the systemfurther comprises a hoisting device (400), the hoisting device (400) having a pulling element attachable to the power cable (10) and configured to pull the power cable (10) through the routing unit (102).

5. The system according to any one of the preceding claims, wherein the system further comprises a transfer apparatus (500) configured to move the power cable (10) to the offshore structure (100), and further configured to align the power cable (10) such that the power cable (10) is proximate and vertically below an opening at 5 the lower end of the routing unit (102).

6. The system according to claim 5,wherein the transfer apparatus (500) is a zip line arrangement having a zip line cable (540) extending between a first connection (501) on the offshore structure 10 (100) at a position proximate and above the hang off balcony (510), and a secondconnection (502) positioned on a vessel (520); andwherein the zip line arrangement comprises a cable mounting device (550) on the zip line cable (540), the cable mounting device (550) configured to receive the power cable (10).

157. The system according to claim 6, wherein the first connection (501) comprises a driving arrangement configured to move the first connection (501) along a vertical length of the offshore structure (102).20 8. The system according to any one of the proceeding claims, wherein the routingunit is selected from a group consisting of: an l-Tube, a J-Tube, a telescopic tube, a short tube element, a bell mouth, and a connector unit.

9. The system according to any one of the preceding claims, wherein a bend 25 stiffener (20) is attachable to the power cable (10), and / or wherein the bend stiffener (20) is attachable to the routing unit (102).

10. The system according to any one of the preceding claims, wherein the second position of the routing unit (102) is at least partially below sea level (40).3011. The system according to any one of the preceding claims, wherein the offshore structure (100) is a floating offshore structure (100), and optionally wherein the floating offshore structure comprises a wind turbine (30).3512. The system according to any one of the preceding claims, wherein the offshore structure (100) further comprises a supporting post (101);wherein the routing unit (102) is movably attached to the supporting post 5 (101); andwherein the supporting post (101) and the routing unit (102) each extend parallel to each other in a substantially perpendicular direction to the sea level (40).

13. A method for installing a power cable (10) to an offshore structure (100), the 10 method comprising:providing a system according to any one of the preceding claims;providing a power cable (10);activating the actuator (300) to move the routing unit (102) to the first position;15 connecting the power cable (10) with the offshore structure (100) via therouting unit (102); andactivating the actuator (300) to move the routing unit (102) to the second position.20 14. The method according to claim 13 when providing a system according to claim 4,wherein the step of connecting the power cable (10) to the offshore structure (100) via the routing unit (102) further comprises the steps of:attaching the pulling element to a first end (12) of the power cable (10); andpulling, via the pulling element, the power cable (10) through the routing unit25 (102); and / oradvancing the power cable (10) through the routing unit (102) by lowering the routing unit (102) while holding the power cable (10) with the pulling element.

15. The method according to claim 13, when providing a system according to claim 530 or 6, wherein providing the power cable (10) is followed by the step of:transporting, via the transfer apparatus (500), the first end (12) of the power cable (10) to the third position.

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