Patent Publication Number: US-2020283103-A1

Title: Offshore substation topside

Description:
FIELD 
     The present invention relates to a method of manufacturing an offshore substation topside and to an offshore substation topside 
     BACKGROUND 
     Wind power has been proven as a highly effective way of producing renewable energy. However due to the high population density of many parts of the developed world there is a limit to the number of wind turbines which may be erected on land. 
     Much attention has therefore been devoted to offshore wind farms, as they may effectively utilize the vast sea areas that are difficult to use for alternative purposes. It is however a complicated process not only to produce wind electricity offshore but also to transport the generated electricity towards land. 
     A central part of an offshore wind farm is the offshore substation. The offshore substation receives the electricity generated by the wind turbines and increases the voltage before delivering the electricity to export cables. 
     The offshore substation topside is typically arranged on an offshore support structure such as a multi-legged fixed bottom structure e.g. a jacket. Traditionally, offshore substation topsides are manufactured in one piece and lifted onto the offshore support structure by a heavy lifting vessel. 
     The offshore substation topside must be designed to the specific needs of the specific offshore wind farm where it is to be used. The design and manufacture of an offshore substation topside is therefore a very time consuming and costly process that may take years to complete. 
     It has become clear as a result of the global effort to reduce CO 2  emissions that new offshore wind farms must be put into services at a significantly higher pace than previously. 
     There is therefore a need for a simpler and faster method of manufacturing an offshore substation topside. 
     SUMMARY 
     According to a first aspect, the invention relates to a method of manufacturing an offshore substation topside for assisting in transporting electricity generated by an offshore wind farm to land, the offshore wind turbine farm being arranged at a first location, the offshore substation topside being supported by an offshore support structure and comprising a first set of gas insulated switch gears, GIS, a second set of GIS, and a transformer, wherein the first set of GIS are adapted to receive AC current generated by at least a part of the wind turbines of the offshore wind farm and deliver the AC current to the transformer, the transformer being configured to increase the voltage of the AC current generated by the at least part of the wind turbine and deliver the AC current with the increased voltage to the second set of GIS, the second set of GIS being configured to provide the AC current with the increased voltage to one or more export cables for transporting the AC current towards the shore, wherein the offshore substation topside further comprises a first deck and a first block arranged on the first deck, wherein the first block comprises a plurality of modules including a first module and a second module, each module of the plurality of modules comprises one or more standardized sections selected from a group of standardized section, each standardized section comprises a self-supporting frame, and wherein the first module of the plurality of modules is manufactured at a second location, the first module and the second module of the plurality of modules having at least one standardized section in common, and the plurality of modules being assembled into the first block at a location remote from the second location. 
     Consequently, by using standardized sections where productions and assembly is distributed between a plurality of locations a simple and efficient way of manufacturing an offshore substation topside is provided. 
     The offshore support structure may be multi-legged fixed bottom structure e.g. a jacket, a monopile, a compliant tower, a gravity structure or a floating structure for an offshore structure such as a TLP (tension leg platform), a Semi-Submersible, a spar platform or a tri-pile. An offshore wind farm may comprise more than one offshore substation. Preferably, the first block comprises more than two modules e.g. at least 4, or 6 modules. The standardized sections may be welded, bolted or stabbed together to form a module. Correspondingly, the modules e.g. the first module and the second module may be welded, bolted or stabbed together to form the first block. The group of standardized sections may comprise a first subgroup of standardized sections having a first height and a second group of standardized section having a second height. The group of standardized sections may further comprise a third subgroup of standardized sections having a third height. The first height may be higher than the second height, and the second height may be higher than the third height. As an example the first height may be between 5.8 and 6.7 meter e.g. 6.2 meter, the second height may be between 4.7 and 5.7 meter e.g. 5.2 meter, and the third height may be between 3.5 and 4.5 meter e.g. 4.0 meter. The first group of standardized sections may be adapted for forming modules suitable for housing high voltage, HV GIS e.g. GIS capable of handling voltages at or above 120 kV. The second group of standardized sections may be adapted for forming modules suitable for housing medium voltage, MV GIS e.g. GIS capable of handling voltages between 20 and 120 kV. The third group of standardized sections may be adapted for forming modules suitable for housing low voltage distribution systems, and LV equipment such as SCADA equipment. 
     In some embodiments the offshore substation topside further comprises a second block arranged on the first deck, wherein the first block comprises a first group of modules comprising standardized sections selected from a first subgroup of standardized sections, the second block comprises a second group of modules comprising standardized section selected from a second subgroup of standardized sections, and wherein the first set of GIS are being arranged inside the second group of modules of the second block and the second set of GIS are being arranged inside the first group of modules of the first block. 
     This allows the offshore substation topside to efficiently be adapted to a specific offshore wind farm. 
     In some embodiments the first module is arranged adjacent to the second module. 
     In some embodiments the first block further comprises a first standardized interface module configured to interface with a group of central systems and thereby provide connectivity for subsystems of the plurality of modules to the central systems. 
     Consequently, by using a standardized interface module an effective way of providing connectivity to central system is provided. The use of standardized interface modules may further allow the standardized sections to be even further standardized as they to a lesser degree need to be adapted for connecting to central systems of the offshore substation topside. 
     In some embodiments, the central systems comprise a ventilation system for providing ventilation, an electrical system for providing electricity to equipment in the plurality of modules and/or fire extinguishing system. 
     In some embodiment the first module and the second module each comprises a ventilation subsystem for providing ventilation to the modules, the ventilation subsystem comprises a main ventilation tube extending along a first common central axis, the main ventilation tube of the ventilation subsystem of the first module having an inlet and an outlet, the main ventilation tube of the ventilation subsystem of the second module having an inlet, and wherein the inlet of the main ventilation tube of the ventilation subsystem of the second module is being connected to the outlet of the main ventilation tube of the ventilation subsystem of the first module when the plurality of modules is being assembled into the first block. 
     Consequently, by providing the individual modules with ventilation subsystems that are adapted to be connected, the process of assembling a block may be further streamlined. 
     The main ventilation tubes of the individual modules may be connected to each other using matching flanges or bellow connectors. The ventilation subsystem of a module may further comprise one or more ventilation outlets for ventilating the module. 
     In some embodiments the first module is being arranged adjacent to the first standardized interface module, the first standardized interface module comprising a main ventilation tube having an inlet connected to a ventilation tube of a central ventilation system of the offshore substation and an outlet and wherein the outlet is being connected to the inlet of the main ventilation tube of the ventilation subsystem of the first module when the plurality of modules is being assembled into the first block. 
     In some embodiments prior to assembly of the first module and the second module, the ventilation subsystem of the first module is tested at the first location and the ventilation subsystem of the second module is tested at another location different from the first location. 
     Consequently, by testing the ventilation subsystems at different location (preferably where the modules are built) the risk of errors of the ventilation subsystem of the first block may be lowered. This will further reduce the risk of any delays when assembling the first block. 
     In some embodiments the first standardized interface module is arranged centrally on the first deck. 
     In some embodiments the first module and the second module comprise an electrical subsystem for providing electricity to equipment arranged in the modules, the electrical subsystem of the first module comprises a first main electrical connector and a second main electrical connector, the electrical subsystem of the second module comprises a first main electrical connector, wherein first main electrical connector and the second main electrical connector of the first module and the first main electrical connector of the second module are arranged along a second common central axis and the second main electrical connector of the first module is being connected electrically to the first main electrical connector of the second module when the plurality of modules is being assembled into the first block. 
     Consequently, by providing the individual modules with electrical subsystems that are adapted to be connected the process of assembling a block may be further streamlined. 
     The electrical subsystems are configured to provide equipment within the individual modules with power such as lightning equipment, computer equipment and the like. Preferably all modules of the first block comprise an electrical subsystem e.g. at least 4 or 6 modules of the first block. 
     In some embodiments the electrical subsystem of the second module further comprises a second main electrical connector arranged along the second common central axis. 
     In some embodiments the first standardized interface module comprises an electrical subsystem connected to a main electrical system of the offshore substation, the electrical subsystem of the first standardized interface module comprises a first main electrical connector being connected to first electrical connector of the electrical subsystem of the first module when the plurality of modules is being assembled into the first block. 
     Consequently, by using a standardized interface module to provide electricity to the electrical subsystems of the modules, the electrical subsystems of the modules may be designed without the need of adapting them to the specific main electrical system of the offshore substation. 
     In some embodiments prior to assembly of the first module and the second module, the electrical subsystem of the first module is tested at the first location and the electrical subsystem of the second module is tested at another location different from the first location. 
     This allows for failures in the electrical subsystems of the modules to be detected before they are assembled into the first block. 
     In some embodiment the first module and the second module each comprises a fire extinguishing subsystem for extinguishing fires in the modules, the fire extinguishing subsystem comprises a fire pipe for transporting a fire extinguishing fluid, the fire pipe extending along a fifth common central axis, the fire pipe of the fire extinguishing subsystem of the first module having an inlet and an outlet, the fire pipe of the fire extinguishing subsystem of the second module having an inlet, and wherein the inlet of the fire pipe of the fire extinguishing subsystem of the second module is being connected to the outlet of the fire pipe of the fire extinguishing subsystem of the first module when the plurality of modules is being assembled into the first block. 
     Consequently, by providing the individual modules with fire extinguishing subsystems that are adapted to be connected, the process of assembling a block may be further streamlined. 
     All modules of a block may be provided with fire extinguishing subsystems. The fire extinguishing subsystems of the individual modules may further comprise one or more fire extinguishing sprinkler. The fire extinguishing subsystems of the individual modules may further comprise one or more fire detectors either arranged together with a fire extinguishing sprinkler or as an individual unit. The fire extinguishing fluid may be any fluid suitable for extinguishing fires e.g. halogen or water. The fire pipes of the individual modules may be connected to each other using matching flanges or bellow connectors. 
     In some embodiments, the first standardized interface module comprises a fire pipe fluidly connected to a tank of fire extinguishing fluid of the offshore substation topside, the fire pipe having an outlet, and wherein the outlet is being connected to the inlet of the fire pipe of the first module when the plurality of modules is being assembled into the first block. 
     In some embodiments the fire extinguishing subsystem of the first module and the second module each comprises a fire detector communicatively coupled to a central fire control unit, wherein the fire control unit is configured to, responsive to a fire detected by one or more fire detectors, take an action to extinguish the fire and/or prevent it from spreading. 
     The central fire control unit may be configured to stop at least a part of the ventilation system, activate fire sprinklers, and/or close fire doors between the individual modules. Preferably all modules of the first block comprise a fire detector communicatively coupled to the central fire control unit. The fire detectors may be wired or wireless communicatively coupled to the central fire control unit. 
     In some embodiments prior to assembly of the first module and the second module, the fire extinguishing subsystem of the first module is tested at the first location and the fire extinguishing subsystem of the second module is tested at another location different from the first location. 
     Consequently, by testing the fire extinguishing subsystems at different location (preferably where the modules are built) the risk of errors of the fire extinguishing subsystem of the first block may be lowered. This will further reduce the risk of any delays when assembling the first block. 
     In some embodiments the ventilation subsystem of the first module and second module each comprises a valve communicatively coupled to the central fire control unit, and wherein the central fire control unit is further configured to detect the location of a fire and responsive to the detected location close valves of one or more ventilation subsystems to stop ventilation of modules being in fire. 
     Consequently, at least some of the modules not being in fire may still be ventilated. This may be important since it may take some time to put the offshore substation topside in an emergency state. Thus by ventilating at least some of the non-affected modules the equipment in those modules may be protected from damage. 
     All ventilation subsystems may be provided with a valve communicatively coupled to the central fire control unit. The valve is preferably arranged down stream of any ventilation outlets and thereby configured to close of ventilation for modules arranged downstream. 
     In some embodiments the plurality of module of the first block further comprises a third module and a fourth module, the third and the fourth module each having at least one standardized section in common, and wherein the third module is arranged on top of the first module, and the fourth module is arranged on top of the second module, the self-supporting frames of the standardized sections of first module being further configured to support the weight of the third module, and the self-supporting frames of the standardized sections of the second module being further configured to carry the weight of the fourth module. 
     In some embodiments the first block further comprises a second standardized interface module, the second standardized interface module being arranged on top of the first standardized interface module and being configured to interface with the first standardized interface module. 
     In some embodiments the third module and the fourth module each comprises a ventilation subsystem with a main ventilation tube extending a long a third common central axis, the main ventilation tube of the ventilation subsystem of the third module having an inlet and an outlet, the main ventilation tube of the ventilation subsystem of the fourth module having an inlet, and wherein the inlet of the main ventilation tube of the ventilation subsystem of the fourth module is being connected to the outlet of the main ventilation tube of the ventilation subsystem of the third module when the plurality of modules is being assembled into the first block. 
     In some embodiments the main ventilation tube of the first standardized interface module further comprises a second outlet, and wherein the second standardized interface module comprises a main ventilation tube having an inlet and an outlet, the inlet being connected to the second outlet of the main ventilation tube of the first standardized interface module and the outlet being connected to the inlet of the main ventilation tube of the ventilation subsystem of the third module when the plurality of modules is being assembled into the first block. 
     In some embodiments the first common central axis is parallel with the third common central axis. 
     In some embodiments the third module and the fourth module comprises an electrical subsystem for providing electricity to equipment arranged in the modules, the electrical subsystem of the third module comprising a first main electrical connector and a second main electrical connector, the electrical subsystem of the fourth module comprises a first main electrical connector, wherein the first main electrical connector and the second main electrical connector of the third module and the first main electrical connector of the fourth module are arranged along a fourth common central axis and the second main electrical connector of the third module is being connected electrically to the first main electrical connector of the fourth module when the plurality of modules of is being assembled into the first block. 
     In some embodiments the electrical subsystem of the first standardized interface module comprises a second main electrical connector, the second standardized interface module comprises an electrical subsystem comprising a first main electrical connector and a second main electrical connector, the first main electrical connector being connected to the second main electrical connector of the electrical subsystem of the first standardized interface module, and the second main electrical connector being connected to the first main electrical connector of the third module when the plurality of modules is being assembled into the first block. 
     In some embodiments the offshore substation topside further comprises a second block arranged opposite to the first block, wherein the second block comprises a plurality of modules including a first module and a second module, each module of the plurality of modules comprises one or more standardized sections. 
     In some embodiments the plurality of modules is being assembled into the first block at a location more proximal to the first location than the second location. 
     Consequently, by assembling the plurality of modules into the first block close to the first location (being the location of the offshore wind farm) transportation time of the first block may be reduced. This may furthermore reduce the risk that the first block becomes damaged during transportation. 
     In some embodiments the first deck is arranged on the offshore support structure before the first block is arranged on the first deck. 
     In some embodiments the plurality of modules is being transported by one or more ships to the offshore support structure and assembled into the first block offshore on the first deck at the offshore support structure. 
     Consequently, by assembling the first block offshore at the offshore support structure, even a large offshore substation may be constructed with only the assistance of smaller lifting vessels. This may be especially important when offshore wind farms are being built far from land or at a location where there is no nearby heavy lifting vessel. By providing the modules with subsystems that may be tested onshore, the offshore assembly time may be lowered. This may be important since offshore work is more complicate, dangerous and expensive than onshore work. 
     The plurality of modules may be raised onto the first deck one by one using a crane of a crane vessel. 
     According to a second aspect the invention relates to an offshore substation topside for assisting in transporting electricity generated by an offshore wind farm to land, the offshore substation topside being supported by an offshore support structure and comprising a first set of gas insulated switch gears, GIS, a second set of GIS, and a transformer, wherein the first set of GIS are adapted to receive AC current generated by at least a part of the wind turbines of the offshore wind farm and delivering the AC current to the transformer, the transformer being configured to increase the voltage of the AC current generated by the at least part of the wind turbine and deliver the AC current with the increased voltage to the second set of GIS, the second set of GIS being configured to provide the AC current with the increased voltage to one or more export cables for transporting the AC current towards the shore, wherein the offshore substation topside further comprises a first deck and a first block arranged on the first deck, wherein the first block comprises a plurality of modules including a first module and a second module, each module of the plurality of modules comprises one or more standardized sections selected from a group of standardized section, each standardized section comprises a self-supporting frame, and wherein the first module and the second module of the plurality of modules have at least one standardized section in common. 
     In some embodiments the offshore substation topside further comprises a second block arranged on the first deck, wherein the first block comprises a first group of modules comprising standardized sections selected from a first subgroup of standardized sections, the second block comprises a second group of modules comprising standardized section selected from a second subgroup of standardized sections, and wherein the first set of GIS are being arranged inside the second group of modules of the second block and the second set of GIS are being arranged inside the first group of modules of the first block. 
     In some embodiments the first block comprises a first standardized interface module configured to interface with a group of central systems and thereby provide connectivity for subsystems of the plurality of modules to the central systems. 
     In some embodiment the first module and the second module each comprises a ventilation subsystem for providing ventilation to the modules, the ventilation subsystem comprises a main ventilation tube extending along a first common central axis, the main ventilation tube of the ventilation subsystem of the first module having an inlet and an outlet, the main ventilation tube of the ventilation subsystem of the second module having an inlet, and wherein the inlet of the main ventilation tube of the ventilation subsystem of the second module is connected to the outlet of the main ventilation tube of the ventilation subsystem of the first module. 
     In some embodiments the first module is being arranged adjacent to the first standardized interface module, the first standardized interface module comprising a main ventilation tube having an inlet connected to a ventilation tube of a central ventilation system of the offshore substation topside and an outlet connected to the inlet of the main ventilation tube of the ventilation subsystem of the first module. 
     In some embodiments the first module and the second module comprise an electrical subsystem for providing electricity to equipment arranged in the modules, the electrical subsystem of the first module comprises a first main electrical connector and a second main electrical connector, the electrical subsystem of the second module comprises a first main electrical connector, wherein first main electrical connector and the second main electrical connector of the first module and the first main electrical connector of the second module are arranged along a second common central axis and the second main electrical connector of the first module is being connected electrically to the first main electrical connector of the second module. 
     In some embodiments the first standardized interface module comprises an electrical subsystem connected to a main electrical system of the offshore substation topside, the electrical subsystem of the first standardized interface module comprises a first main electrical connector being connected to first electrical connector of the electrical subsystem of the first module. 
     In some embodiment the first module and the second module each comprises a fire extinguishing subsystem for extinguishing fires in the modules, the fire extinguishing subsystem comprises a fire pipe for transporting a fire extinguishing fluid, the fire pipe extending along a fifth common central axis, the fire pipe of the fire extinguishing subsystem of the first module having an inlet and an outlet, the fire pipe of the fire extinguishing subsystem of the second module having an inlet, and wherein the inlet of the fire pipe of the fire extinguishing subsystem of the second module is connected to the outlet of the fire pipe of the fire extinguishing subsystem of the first module. 
     In some embodiments, the first standardized interface module comprises a fire pipe fluidly connected to a tank of fire extinguishing fluid of the offshore substation topside, the fire pipe having an outlet, and wherein the outlet is connected to the inlet of the fire pipe of the first module. 
     In some embodiments the fire extinguishing subsystem of the first module and the second module each comprises a fire detector communicatively coupled to a central fire control unit, wherein the fire control unit is configured to, responsive to a fire detected by one or more fire detectors, take an action to extinguishing the fire and/or prevent it from spreading. 
     In some embodiments the ventilation subsystem of the first module and second module each comprises a valve communicatively coupled to the central fire control unit, and wherein the central fire control unit is further configured to detect the location of a fire and responsive to the detected location close valves of one or more ventilation subsystems to stop ventilation of modules being in fire. 
     In some embodiments the plurality of module of the first block further comprises a third module and a fourth module, the third and the fourth module each having at least one standardized section in common, and wherein the third module is arranged on top of the first module, and the fourth module is arranged on top of the second module, the self-supporting frames of the standardized sections of first module being further configured to support the weight of the third module, and the self-supporting frames of the standardized sections of the second module being further configured to carry the weight of the fourth module. 
     In some embodiments the first block further comprises a second standardized interface module, the second standardized interface module being arranged on top of the first standardized interface module and being configured to interface with the first standardized interface module. 
     According to a third aspect the invention relates to use of an offshore substation topside manufactured as disclosed in relation to the first aspect for assisting in transporting electricity generated by an offshore wind farm towards land. 
     The different aspects of the present invention can be implemented in different ways including methods of manufacturing an offshore substation topside and offshore substation topsides described above and in the following, each yielding one or more of the benefits and advantages described in connection with at least one of the aspects described above, and each having one or more preferred embodiments corresponding to the preferred embodiments described in connection with at least one of the aspects described above and/or disclosed in the dependant claims. Furthermore, it will be appreciated that embodiments described in connection with one of the aspects described herein may equally be applied to the other aspects. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or additional objects, features and advantages of the present invention, will be further elucidated by the following illustrative and non-limiting detailed description of embodiments of the present invention, with reference to the appended drawings, wherein: 
         FIG. 1  shows a schematic view of an offshore substation platform according to an embodiment of the present invention. 
         FIG. 2  shows schematically an offshore substation topside according to an embodiment of the present invention. 
         FIG. 3 a    shows a schematic drawing of a group of standardized sections seen from the side according to an embodiment of the present invention. 
         FIG. 3 b    shows a schematic drawing of modules assembled by the group of standardized sections shown in  FIG. 3   a.    
         FIG. 4  shows a schematic drawing of a module according to an embodiment of the present invention. 
         FIG. 5  shows a flowchart of a method of manufacturing an offshore substation topside according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, reference is made to the accompanying figures, which show by way of illustration how the invention may be practiced. 
       FIG. 1  shows schematically an offshore substation platform for assisting in transporting electricity generated by an offshore wind farm to land according to an embodiment of the invention. The offshore substation platform comprises an offshore substation topside and an offshore support structure. The offshore substation platform is seen from the side. The offshore substation topside being supported by the offshore support structure being a jacket  191  in this embodiment. The offshore substation comprises a first set of gas insulated switch gears, GIS  140 - 143 , a second set of GIS (not shown), and a transformer (not shown), wherein the first set of GIS  140 - 143  are adapted to receive AC current generated by at least a part of the wind turbines of the offshore wind farm and deliver the AC current to the transformer, the transformer being configured to increase the voltage of the AC current generated by the at least part of the wind turbine and deliver the AC current with the increased voltage to the second set of GIS. The second set of GIS being configured to provide the AC current with the increased voltage to one or more export cables for transporting the AC current towards the shore. The offshore substation topside further comprises a first deck  101  and a first block  100  arranged on the first deck  101 . The first block  100  comprises a plurality of modules  110 - 116  including a first module  110 , a second module  111 , a third module  112 , a fourth module  113 , a fifth module  114 , a sixth module  115 , and a seventh module  116 . Each module of the plurality of modules  110 - 116  comprises one or more standardized sections selected from a group of standardized sections, each standardized section comprises a self-supporting frame. In this embodiment, the first module  110 , the fourth module  113  and the fifth module  114  each have two standardized sections, and the second module  111 , the third module  112 , sixth module  115 , and the seventh module  116  each have a single standardized section. In this embodiment, the first module  110 , the second module  111 , the third module  112 , and the fourth module  113  have one standardized section in common, and the first module  110  and the fourth module  113  have two standardized sections in common. Correspondingly, the fifth module, the sixth module  115  and the seventh module  116  have one standardized section in common. In this embodiment a first GIS  140  of the first set of GIS is arranged inside the first module  110 , a second GIS  141  of the first set of GIS is arranged inside the second module  111 , a third GIS  142  of the first set of GIS is arranged inside the third module  112 , and a fourth GIS  143  of the first set of GIS is arranged inside the fourth module  113 . Each GIS of the first group of GIS  140 - 143  is connected to a plurality of offshore wind turbines via their respective cable  170 - 173 . In this embodiment, the first GIS  140  and the fourth GIS  143  are larger than the second GIS  141  and the third GIS  142 . Thus, the first GIS  140  and the fourth GIS  143  may be connected to more offshore wind turbines and/or larger offshore wind turbines than the second GIS  141  and the third GIS  142 . However, in other embodiment all GIS of the first group of GIS may be of equal size. In this embodiment, the fifth, sixth and seventh module  114 - 116 , are arranged on top of the first, second, third and fourth module  110 - 113 . Thus, the self-supporting frame of the standardized sections of the first, second, third and fourth module  110 - 113  is further adapted to support a module arranged on top of it. The fifth, sixth and seventh module  114 - 116  may house SCADA equipment  144  or the like. The first block  100  comprises further four standardized interface modules  130 - 133 . The standardized interface modules  130 - 133  are configured to interface with a group of central systems  160  and thereby provide connectivity for subsystems of the modules  110 - 116  to the central systems  160 . The central systems may comprise a ventilation system for providing ventilation and/or an electrical system for providing electricity to equipment in the plurality of modules  110 - 116 . By providing the first block with interface modules  130 - 133  the remaining modules may be further standardized as there is no need to adapt their subsystems to the central systems of the offshore substation topside. The standardized interface modules  130 - 133  may be provided with ventilation tubes and/or electrical cables  150 - 151  for providing the connectivity. 
     Correspondingly, the modules  110 - 116  may be provided with ventilation tubes and/or electrical cables  152 - 153  configured to receive air and/or electricity from the standardized interface modules  130 - 133 . 
       FIG. 2  shows schematically an offshore substation topside  200  according to an embodiment of the present invention. The offshore substation topside  200  is seen from the top. The offshore substation topside comprises a first block  201  and a second block  202 . The first block  201  comprises four modules  210 - 213  where each module comprises one or more standardized sections (not shown). Correspondingly, the second block  202  comprises four modules  220 - 223  where each module comprises one or more standardized sections (not shown). The offshore substation topside  200  comprises a first set of GIS  214 - 217 , a second set of GIS  224 - 227 , and two transformers  203 - 204 . The first set of GIS  214 / 217  is arranged inside the modules  210 - 213  of the first block  201  and is adapted to receive AC current generated by at least a part of the wind turbines of an offshore wind farm and further deliver the AC current to the two transformers  203 - 204 . The two transformers  203 - 204  are arranged outside and are configured to increase the voltage of the AC current generated by the at least part of the wind turbine and deliver the AC current with the increased voltage to the second set of GIS  224 - 227 . The second set of GIS  224 - 227  is arranged inside the modules  220 - 223  of the second block  202  and is configured to provide the AC current with the increased voltage to one or more export cables for transporting the AC current towards the shore. The offshore substation topside  200  may further comprise a shunt reactor  205  and a shunt reactor transformer  206 . 
       FIG. 3 a    shows a schematic drawing of a group of standardized sections seen from the side according to an embodiment of the invention. The group of standardized sections comprises a first subgroup of standardized sections  312  having a first height, a second group of standardized section  311  having a second height, and a third subgroup of standardized sections  310  having a third height. In this embodiment the first subgroup  312  comprises two standardized sections  305 - 306 , the second subgroup  311  comprises two standardized sections  303 - 304 , and the third subgroup  310  comprises two standardized sections  301 - 302 . The first height may be higher than the second height, and the second height is higher than the third height. As an example the first height may be between 5.8 and 6.7 meter e.g. 6.2 meter, the second height may be between 4.7 and 5.7 meter e.g. 5.2 meter, and the third height may be between 3.5 and 4.5 meter e.g. 4.0 meter. The first group of standardized sections may be adapted for forming modules suitable for housing high voltage, HV GIS e.g. GIS capable of handling voltages at or above 120 kV. The second group of standardized sections may be adapted for forming modules suitable for housing medium voltage, MV GIS e.g. GIS capable of handling voltages between 20-120 kV. The third group of standardized sections may be adapted for forming modules suitable for housing low voltage, LV, equipment such as SCADA equipment. 
       FIG. 3 b    shows a schematic drawing of modules assembled by the group of standardized sections shown in  FIG. 3 a   . Shown is a first module  320 , a second module  321 , a third module  322 , and a fourth module  323 . The first module  320  has two identical sections  301  selected from the third subgroup  310 , the second module has a first section  301  and a second section  302  selected from the third subgroup of sections, the third module  322  has two identical sections  304  selected from the second subgroup of sections  311 , and the third module  323  has a single section  323  selected from the first subgroup of sections  312 . 
       FIG. 4  shows a schematic drawing of a module  401  according to an embodiment of the invention. The module  401  has a single standardized section having a self-supporting frame i.e. a frame capable of supporting the weight of the module. Thus the module does not need any external support frame or structure. The module comprises a ventilation subsystem for providing ventilation to the module, an electrical subsystem for providing electricity to equipment in the module  401 , and a fire extinguishing subsystem for extinguishing fires in the module  401 . The ventilation subsystem comprises a main ventilation tube  402  extending along a first common central axis  422 , the main ventilation tube  402  of the ventilation subsystem has an inlet  420  and an outlet  421 . The ventilation subsystem may further comprise a ventilation outlet  423 . The inlet  420  and the outlet  421  are configured to be connected to respective inlets/outlets of neighbouring modules e.g. by providing the inlet  420  and the outlet  421  with a flange or a bellow connector configured to be connected to a matching flange of a neighbouring module. The electrical subsystem comprises a first main electrical connector  430  and a second main electrical connector  431  arranged along a second common central axis  432 . The electrical subsystem may further comprise one or more power outlets  433 - 435  e.g. for providing electricity to lightning devices, computers and other electrical devices. The fire extinguishing subsystem comprises a fire pipe  404  for transporting a fire extinguishing fluid, the fire pipe extending along a fifth common central axis  442 , the fire pipe  404  of the fire extinguishing subsystem has an inlet  440  and an outlet  441 . The fire extinguishing subsystem may further comprise a fire extinguishing sprinkler  443  and a fire detector  444 . The inlet  440  and the outlet  441  are configured to be connected to respective inlets/outlets of neighbouring modules e.g. by providing the inlet  440  and the outlet  441  with a flange or a bellow connector configured to be connected to a matching flange of a neighbouring module. The electrical subsystem, the ventilation subsystem, and the fire extinguishing subsystem are preferably provided to the module during its manufacture, i.e. before the module is connected other modules and thereby assembled into a block. Furthermore, the electrical subsystem, the ventilation subsystem, and the fire extinguishing subsystem are preferably tested at location of or close to the location where the module  401  is manufactured e.g. away from the location where the module  401  is connected/attached to other modules to form the block. This allows any failures n subsystems of the modules to be detected before they are assembled into a block. 
       FIG. 5  shows a flowchart of a method of manufacturing an offshore substation topside according to an embodiment of the present invention. Firstly, in step  501  a plurality of modules is manufactured, where each module comprises one or more standardized sections. Preferably the plurality of modules is manufactured at a plurality of different locations, i.e. at different manufacturers and/or sub-suppliers. However, the plurality of modules may also be manufactured in a single factory. The plurality of modules is preferably provided with subsystems such as an electrical subsystem and/or an ventilation subsystem at the factory where they are produced. Next, in step  502  the plurality of modules is tested preferably at the factory where they have been manufactured. If the plurality of modules has been provided with subsystems then these subsystems may also be tested preferably at the factory where they are produced. This is done to make the assembly of the plurality of modules as simple and secure as possible. Next in step  503  at least some modules of the plurality of modules are transported from the location where they were manufactured to the location where they are going to be assembled into a block e.g. by a truck or a vessel (e.g. barge). The assembly location may be a location where one or more of the plurality of modules have been manufactured or a different location, i.e. a location where no modules have been manufactured. Then in step  504  the plurality of modules is assembled into one or more blocks e.g. by welding, bolting or stabbing the modules together. If the modules are provided with subsystems then the subsystems of the modules are also connected whereby the one or more blocks may directly be provided with a fully functional electrical system and/or a fully functional ventilation system. The plurality of modules may be assembled into one or more blocks on a deck of the offshore substation topside. Alternatively, the plurality of modules may be firstly be assembled into one or more blocks and then subsequently arranged on a deck of the offshore substation topside e.g. using crane. The assembly location is preferably a location relatively close to the location of the offshore wind farm whereby the transportation time of the deck and the one or more blocks may be reduced. In a preferred embodiment, the deck is firstly arranged on the offshore support structure, and the plurality of modules is then transported to the offshore support structure e.g. by vessel and then assembled into the first block offshore directly on top of the offshore support structure. This makes it possible to install an offshore substation topside without the need of a heavy lifting vessel capable of lifting an entire topside and/or deck with one or more blocks arranged thereon. This will potentially lower the costs especially when the offshore wind farm is being built at a location where there are no nearby heavy lifting vessels available. 
     Although some embodiments have been described and shown in detail, the invention is not restricted to them, but may also be embodied in other ways within the scope of the subject matter defined in the following claims. In particular, it is to be understood that other embodiments may be utilised and structural and functional modifications may be made without departing from the scope of the present invention. 
     In device claims enumerating several means, several of these means can be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims or described in different embodiments does not indicate that a combination of these measures cannot be used to advantage. 
     It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.