Assembly and method for installing a subsea cable

Abstract

An assembly for installing a subsea cable, the assembly comprising a submersible apparatus and a submersible cable holder comprising the subsea cable, the subsea cable being connectable to the submersible apparatus through the connector for transmission of electric power and/or data to the submersible apparatus; wherein the assembly is configured to install the subsea cable while the submersible apparatus is electrically powered through said subsea cable. And a method for installing a subsea cable with a submersible apparatus, the method comprising: supplying electric power and/or transmitting data through the subsea cable to the submersible apparatus; and laying the subsea cable in a sea with the submersible apparatus.

Claims

1. An assembly (400) for installing a subsea cable (304), the assembly (400) comprising: a submersible apparatus (200) comprising a deck (201), at least one connector (202), and moving means (208); and a submersible cable holder (300) comprising the subsea cable (304), the subsea cable (304) being connectable to the submersible apparatus (200) through the at least one connector (202) for transmission of at least one of electric power and data to the submersible apparatus (200), and the submersible cable holder (300) being configured to be loaded on and unloaded from the deck (201); wherein the assembly (400) is configured to install the subsea cable (304) while the submersible apparatus (200) is electrically powered through the subsea cable (304).

2. The assembly (400) of claim 1, wherein a first end of the subsea cable (304) is connected to a power source of a facility (101,102) so that the at least one of electric power and data may be delivered to the submersible apparatus (200) upon connection of a second end of the subsea cable (304) to a connector of the at least one connector (202) of the submersible apparatus (200).

3. The assembly (400) of claim 1, wherein the submersible apparatus (200) is configured to transmit and receive data through the subsea cable (304).

4. The assembly (400) of claim 1, wherein the submersible apparatus (200) further comprises means (206) for digging a trench.

5. The assembly (400) of claim 1, wherein the submersible apparatus (200) further comprises at least one battery, the submersible apparatus (200) being configured to obtain electric power from the at least one battery.

6. The assembly (400) of claim 1, wherein the submersible apparatus (200) further comprises means for wireless data transmission and reception, the submersible apparatus (200) at least one of: being configured to transmit and receive data through said means, and the at least one connector comprises: a first connector (202) for connection of the subsea cable (304) and a second connector (215) for connection of a cable for data and power transmission to a device not part of the assembly.

7. The assembly (400) of claim 1, wherein the submersible apparatus (200) further comprises means (203) for manipulating at least one of: the cable (304), a cable connector, a cable accessory, or an obstacle on a seabed.

8. The assembly (400) of claim 1, wherein at least one of the submersible apparatus (200) and the submersible cable holder (300) comprises means for changing a buoyancy of the submersible apparatus (200) or the submersible cable holder (300), respectively.

9. The assembly (400) of claim 1, wherein the submersible apparatus (200) further comprises an acoustic positioning system for sensing subsea acoustic beacons.

10. A method for installing a subsea cable (304) with a submersible apparatus (200), the method comprising: at least one of supplying electric power and transmitting data through the subsea cable (304) to the submersible apparatus (200); digging a trench (604) in a seabed (600) with the submersible apparatus (200) and laying the subsea cable (304) in the trench with the submersible apparatus (200).

11. The method of claim 10, wherein a first end of the subsea cable (304) is connected to a power source of a facility (101,102) and a second end is connected to the submersible apparatus (200).

12. The method of claim 10, further comprising loading a submersible cable holder (300) on the submersible apparatus (200), the submersible cable holder comprising the subsea cable (304).

13. The method of claim 10, further comprising at least one of transmitting data to and receiving data from the submersible apparatus (200) through the subsea cable (304).

14. The method of claim 10, further comprising introducing part of the subsea cable (304) in a carrying means, the carrying means comprising two unassembled tubes (615,616) being configured to be hoisted from a facility (601,611).

15. The method of claim 14, wherein the two unassembled tubes (615,616) are configured to receive the subsea cable (304) while the first part is contacting the seafloor (600) such that the subsea cable (304) forms a U shape between the two unassembled tubes (615,616).

16. The method of claim 15, wherein the facility (601,611) comprises a lifting mechanism (617) and an elongated flexible element (630) connected to the lifting mechanism (617), and wherein the carrying means is configured to be secured to the elongated flexible element (630).

17. The method of claim 10, further comprising introducing part of the subsea cable (304) in a carrying means, the carrying means comprising a hollow device (620) with a semi-circular shape and configured to be hoisted from a facility (601,611).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) To complete the description and in order to provide for a better understanding of the invention, a set of drawings is provided. Said drawings form an integral part of the description and illustrate an embodiment of the invention, which should not be interpreted as restricting the scope of the invention, but just as an example of how the invention can be carried out. The drawings comprise the following figures:

(2) FIG. 1 is a representation of an offshore wind farm.

(3) FIG. 2 is a submersible apparatus of an assembly for installing a subsea cable in accordance with an embodiment of the invention.

(4) FIG. 3 is a submersible cable holder of an assembly for installing a subsea cable in accordance with an embodiment of the invention.

(5) FIG. 4 is an assembly for installing a subsea cable in accordance with an embodiment of the invention.

(6) FIG. 5 is a representation of several vessels towing cable holders and an assembly.

(7) FIGS. 6A-6D are representations of the installation of a submarine cable in accordance with embodiments of the invention.

(8) FIG. 7 is a representation of the installation of a submarine export cable in accordance with an embodiment of the invention.

DESCRIPTION OF A WAY OF CARRYING OUT THE INVENTION

(9) FIG. 1 shows, in a perspective view, an offshore wind farm located in the sea. A substation 101 collects the electric power of each wind turbine 102 through the cables 104a-104c (connecting the substation 101 to the first wind turbine of each branch) and 105 (connecting two consecutive wind turbines 102 of a same branch) and transfers the combined electric power to a facility on land, for example, through the export cable 103; that is, the cable/s 103 may interconnect the substation 101 to the electrical grid that may be on land. The cables 103, 104a-104c and 105 may be laid on the seafloor or be introduced in trenches.

(10) FIG. 2 shows the submersible apparatus 200 for laying a cable in a trench in accordance with an embodiment of the invention. The submersible apparatus 200 comprises a deck 201, a connector 202, means 203 for manipulating a cable, cable accessories, or subsea obstacles (e.g. rocks or plants), funneling means 205, means 206 for digging a trench (e.g. one or more of pre-lay trenching tools such as dredgers and V-shape ploughs, water jetting tools such as one or more jetting blades, jet sledge, hydro plough, vertical injector or mass flow excavation tools, ploughing tools such as cable ploughs and vibration ploughs, mechanical cutting tools such as chain cutters or rock wheel cutters, venture systems, or other tools commonly used in the art of installing subsea cable), watertight compartments 207, moving means 208, a plurality of hydraulic cylinders 209, a support 210 for the drum of a submersible cable holder, means 211 for controlling tension in the cable to be installed, and a system for wireless data transmission and reception.

(11) The submersible apparatus 200 may advantageously be powered through the cable 304, which is installed by an assembly (such as the one of FIG. 4) that comprises the submersible apparatus 200 and a submersible cable holder 300, when the cable is connected to the connector 202.

(12) The cable which is to be laid out and connected to the connector 202 is held in a submersible cable holder 300, such as the one depicted in FIG. 3, loadable on the apparatus 200, that is, which may be loaded on the apparatus. In particular, the deck 201 of the submersible apparatus 200 is configured to support loading of the submersible cable holder 300. The plurality of hydraulic cylinders 209 may lift a submersible cable holder 300 that is lying, for example, on the seafloor, and load it on the deck 201.

(13) The means 203 for manipulating the cable comprise an arm which, in some embodiments, is extensible. Said arm comprises a first end securely fastened to the structure of the apparatus 200, and a second end including a tool for cable manipulation such as the ring-shaped tool 204.

(14) The moving means 208 include a plurality of tracks that provide sufficient grip on irregular surfaces, such as the seabed, so as to permit the movement of the apparatus and, thus, the assembly comprising the submersible apparatus 200.

(15) It should be noted that although not shown on FIG. 2, in some embodiments of the invention the submersible apparatus 200 may include further moving means such as propulsion means for moving underwater or on the water surface.

(16) The submersible apparatus 200 may also be provided with buoyancy means (not shown) known in the art which permit adjusting its floatability, and thus increase/decrease the depth of the apparatus so as to arrive to the seabed or the surface. The buoyancy means may be included within the watertight compartment 207 which, moreover, may store at least one battery, for example. The submersible apparatus 200 also comprises means for changing the buoyancy of the buoyancy means, for instance upon reception of instructions through the cable to be installed or the system for wireless data transmission and reception.

(17) FIG. 3 is a submersible cable holder 300 in accordance with an embodiment of the invention. The submersible cable holder 300 may provide the cable 304 to be installed to a submersible apparatus 200 like the one shown in FIG. 2. The cable holder 300 comprises a support platform 301, a buoyancy tank 302 including buoyancy means, a drum 303 comprising the cable 304 in a rolled form, a plurality of legs 306, and a system for wireless data transmission and reception. The support platform 301 prevents the whole cable holder 300 from sinking below the seafloor when said seafloor is soft, and it further eases the loading of the cable holder 300 on the submersible apparatus 200. The support platform 301 may be detached from the buoyancy tank 302 when it is loaded on the deck 201 of the submersible apparatus 200.

(18) Prior to loading the cable holder 300 on the submersible apparatus 200, the cable 304 is rolled on the drum 303, and preferably a first end (not shown) of the cable 304 is connected to a power source which may be, for example, a substation 101 of an offshore wind farm. The cable 304 may be rolled on the drum 303 after connection of the cable to the power source, or before making said connection.

(19) A second end of the cable 304 may be provided with the plug 305 that fits into the connector 202, thus making possible the connection between the cable 304 and the submersible apparatus 200, and hence supply electric power (transmitted from the power source) and/or transmit data to the submersible apparatus through said cable 304.

(20) The submersible cable holder 200 also comprises means for changing the buoyancy of the buoyancy tank 302, for instance upon reception of instructions from the submersible apparatus 200 when they form an assembly, or through the system for wireless data transmission and reception.

(21) FIG. 4 is an assembly 400 for installing a cable on a seabed or in a trench in accordance with an embodiment of the invention. The assembly 400 may also make the connection between the submarine cable laid out and endpoints such as power sources of facilities or fixed platforms thereby interconnecting both facilities or platforms.

(22) The assembly 400 comprises a submersible apparatus 200 and a submersible cable holder 300 mounted on the deck 201 of the submersible apparatus 200; the cable holder 300 is detached from its support platform 301 while the cable holder 300 is being loaded on the apparatus 200. When the submersible apparatus 200 is not provided with means 206 for digging a trench or said means are not used, the assembly 400 may lay the cable directly on the seabed without carrying out any trenching.

(23) The means 203 for manipulating the cable unroll the cable 304 held in the drum of the cable holder 300 and orient it towards the funneling means 205; the funneling means 205, in turn, orient the cable towards the means 211 for controlling tension, after which the cable 304 is introduced in the trench or laid on the seabed if no trench is dug (e.g. when the submersible apparatus of the assembly does not include means for digging a trench).

(24) While the plug 305 of the cable 304 is plugged in the connector 202 (not illustrated in FIG. 4), the cable 304 may supply electric power to the assembly 400 as long as the other end of the cable 304 is connected to a power source. Similarly, the cable 304 may transmit data to and/or receive data from the submersible apparatus 200 through the cable since, in many cases, the same cable includes optical fibers for data transmission and reception.

(25) Further, the submersible apparatus 200 of the assembly 400 may have an additional connector 215 which may be in the form of a socket or a plug. The connector 215 may receive a wet-mate connector 216, for example, so as to transmit and/or receive power and/or data to/from another apparatus.

(26) The assembly 400 can install subsea cables 104a-104c starting from the position of the substation 101 and ending at the position of the wind turbine of a branch that is farthest from the substation 101. For example, for installing cable 104c, the submersible apparatus 200 loads a cable holder 300 near the substation 101. The cable 304 held in the drum 303 of the cable holder 300, which has a first end connected to a power source of the substation 101 (e.g. an auxiliary electrical grid), has the second end connected to the connector 202 of the submarine apparatus 200 so that it delivers electric power to it. Thus, the apparatus 200 lays out the cable 304 from the substation 101 to the wind turbine 102a (as seen in FIG. 1) while being energized through the same cable 304.

(27) Further, the assembly 400 can install cables 105 (inter-array cables) starting from the last wind turbine of a branch that is already connected (directly or indirectly) to the substation 101. For instance, with reference to FIG. 1, when the branch of cable 104a is to be installed, the assembly 400 first installs cable 104a in order to interconnect the substation 101 with the first wind turbine; the assembly 400 then installs the cable 105a, then the cable 105b, and lastly the cable 105c. In this sequence, the assembly 400 may be powered with the cable it installs while it lays out the cables 104a, 105a-105c.

(28) In another example, when the wind turbine 102a is already connected to the substation 101, the assembly 400 installs the cable 304 between the wind turbines 102a-102b, then the cable between the turbines 102b-102c, and finally the cable between the wind turbines 102c-102d; this sequence also permits the assembly 400 to be energized, during most of the time, through the cables it installs.

(29) In both cases, the assembly 400 may receive the power supplied by the substation 101 or a wind turbine 102 (which has electric power) in order to perform most of the installing tasks. The assembly 400 may keep the usage of the at least one battery to a minimum since it may rely on the energy stored therein when no cable is being installed (e.g. while returning to a substation 101, while unmounting a cable holder 300 and/or mounting another cable holder 300, etc.), and further the at least one battery may be recharged while electric power is being supplied to the assembly 400 through the cable 304.

(30) FIG. 5 is a schematic representation of vessels 500 towing an assembly 400 and submersible cable holders 300.

(31) The vessels 500 tow (with towing means known in the art) from harbor to, for example, a substation 101 of an offshore wind farm one or more assemblies 400, cable holders 300 and/or submersible apparatuses 200. Preferably, the towed devices comprise buoyancy means. Each of the cable holders 300 may comprise a cable held in its drum prior to being towed so as to ease the installation of the subsea cables.

(32) In some cases, any of the assemblies 400, submersible cable holders 300 and/or submersible apparatuses 200, may tow other assemblies, submersible cable holders and/or submersible apparatuses.

(33) FIG. 6A shows the installation of a submarine cable 304. The submersible apparatus of the assembly 400 loads a submersible cable holder near the facility 601 (e.g. substation, wind turbine, etc.) which is partially underwater (i.e. one part below the surface of the sea, and one part above the surface of the sea). The cable holder already comprises a cable 304 which includes a first end connected to a power source of the facility 601. In this sense, the first end of the cable is made go through a J-tube 603 (in an I-tube 602) with the aid of a messenger wire (not illustrated). Thus, by the time the cable holder 300 is to be loaded on the submersible apparatus, part of the cable 304 is already unrolled and introduced in the J-tube 603 so that it may be connected to the power source of the facility 601; the remaining part of the cable 304 is held in the drum of the cable holder 300 and may lay on the seafloor 600 until the apparatus loads it on its deck. The assembly 400 may then install the cable 304.

(34) Therefore, the facility 601 energizes the assembly 400 through the cable 304. The assembly 400 digs a trench 604 in the seafloor and introduces the cable 304 in it while the assembly moves in a forward motion. The means for manipulating the cable unrolls the cable 304 from the drum 303 and orients it towards the funneling means 205 so that it is introduced through the tension controller 211 and in the trench 604. The same cable 304 installed may be used to transmit operating instructions to and data from the assembly 400 so as to perform any of or all these tasks.

(35) FIG. 6B shows the operation of the assembly 400 when it arrives to another facility 611 (e.g. wind turbine) where the installation of the cable 304 must be completed. The means 203 unrolls the cable 304 in excess so that the cable may be manipulated in the facility 611 and introduced in, for example, J-tubes 603.

(36) A carrying means, which may be a hollow device 620 and have semi-circular shape, may be used to hoist the cable up from the seabed 600 and towards the platform 614 of the facility 611. The hollow device 620 may have the appropriate radius to ensure the cable is hoisted up without risk of bending more than its allowable bending radius. With this carrying means, the cable needs not be cut until an entire array cable (connecting several turbines) has been completely laid out. This allows transmitting data and power through said cable to the assembly 400 throughout the operation. The cable may be cut (for example for splicing and connecting to the turbine's electrical equipment) anytime after the complete installation of an array cable. Moreover, this operation may be conducted entirely above water.

(37) FIG. 6C shows another embodiment of the invention where the method to install the cable comprises the use of different carrying means to hoist the cable up towards the platform of the facility 611. In this embodiment, said carrying means comprises at least one unassembled tube or elongated element, and preferably two such tubes or elongated elements 615, 616. Each element can be split open lengthwise and one part of the tubes or elongated elements 616 can be laid on the seafloor with its open side upwards. A rope, chain or the like 630 may attach said part of the tubes 616 to a winch 617 on the platform of the facility 611, this way said part on the seafloor may be lifted to a vertical position so that it may be reassembled (i.e. joined together) with the other part 615 of the tubes or elongated elements.

(38) The assembly 400 is operated to pass near the elongated element on the seafloor, and the means 203 for manipulating the cable 304 insert said cable in the parts 616 of the tubes or elongated elements 616 on the seafloor through their opening.

(39) FIG. 6D illustrates how, in some embodiments of the invention, the part 616 of the tube or elongated element 616 that was laid on the seafloor may be hoisted back to an upright position by the winch 617 on the facility 611 pulling on the rope, chain or the like 630. The tubes 615, 616 or elongated elements may be articulated 618, for example at their lower end, in order to facilitate the assembly and disassembly of the two parts of said tubes or elongated elements 615, 616.

(40) With this carrying means also, the cable needs not be cut until the installation of an entire array cable, connecting several turbines, is completed. This allows transmitting data and power through said cable to the assembly 400 throughout the entire operation. The cable may be cut (for example for splicing and connecting to the turbine electrical equipment) anytime after the installation of an array cable is completed, and this operation may be conducted entirely above water.

(41) When the facility 611 is the last wind turbine of a branch in a wind farm, the submersible apparatus may unload the cable holder and make its way back to the substation using the at least one battery, while being controlled through a hydrophone or an antenna, for example.

(42) FIG. 7 illustrates how to connect a first cable 702a that is being laid out to another cable 702b in accordance with an embodiment of the invention. The connection of the cables may form an export cable for transporting electric power from an offshore wave farm or wind farm, for instance, to an electrical grid on land.

(43) After laying the cable 702a on the seafloor or in a trench, an end of the cable is raised to the platform 701 (e.g. using messenger wires). A submersible cable holder 300 comprising the cable 702b (to which the cable 702a will be connected) is positioned close to the platform 701 so that connection of cables 702a, 702b is simplified. Once an end of each cable is arranged on the platform 701, an operator may proceed to connect the cables using the plugs and connectors 703a and 703b provided in the cables in some embodiments, or splicing the cables together, for instance.

(44) In other embodiments, a vessel is used instead of the platform 701, for example.

(45) In yet other embodiments, the connection is executed without operators on-site. In this case underwater connectors may be used, and the assembly 400 is controlled remotely.

(46) In this text, the term comprises and its derivations (such as comprising, etc.) should not be understood in an excluding sense, that is, these terms should not be interpreted as excluding the possibility that what is described and defined may include further elements, steps, etc. The terms seabed and seafloor have been used indistinctly to refer to the floor of the sea or the ocean.

(47) The invention is obviously not limited to the specific embodiment(s) described herein, but also encompasses any variations that may be considered by any person skilled in the art (for example, as regards the choice of materials, dimensions, components, configuration, etc.), within the general scope of the invention as defined in the claims.