A subsea high-voltage electric power distribution facility

Abstract

A subsea high-voltage electric power distribution facility (201, 301) comprising a plurality of first mounting arrangements (50a, 350a) at respective first positions (40a, 340a), a support base (203, 303) installed on the seabed, comprising a plurality of second mounting arrangements (50b, 350b) at respective second positions (40b, 340b) A plurality of subsea termination assemblies (210, 310) are connected to respective subsea cables (211, 311) and engaging with first mounting arrangements. A subsea high-voltage power distribution assembly (205, 305) is supported on the support base. Switchgear modules (209, 309) engage with second mounting arrangements, wherein the respective switchgear modules connect to respective subsea termination assemblies (210, 310) with first wet-mate connectors (212, 312) and to the subsea high-voltage power distribution assembly (205, 305) with second wet-mate connectors (214, 314). The respective switchgear modules are retrievable from their engagement with the second mounting arrangement (50b, 350b) and the respective subsea termination assemblies are compatible with the second mounting arrangements.

Description

A SUBSEA HIGH-VOLTAGE ELECTRIC POWER DISTRIBUTION FACILITYTechnical Field

[0001] The present invention relates to subsea distribution of electric high voltage power. In particular, it concerns power distribution solutions suitable for offshore power plants, such as wind farms.Background Art

[0002] Electric subsea power distribution has been applied for many years for various purposes. For instance, it is used for power supply of subsea equipment, such as gas compressors.

[0003] In recent years, with the development of offshore wind power facilities, one needs cost-effective and reliable solutions for collecting the produced electric power and transmitting it to shore. This is done with subsea cables, both for collecting power from each respective wind turbine, and for transmitting the collected power to shore.

[0004] Several subsea cables, often referred to as inter-array cables, collect power from several offshore turbines, such that the accumulated power can be transmitted further through a single subsea cable. To do this, the inter-array cables are connected to a subsea high-voltage electric power distribution facility at the seabed. The facility has a subsea high-voltage electric power distribution assembly, which includes a switchgear assembly and sometimes a subsea transformer. The latter type of distribution assembly is often referred to as a collector or a substation.

[0005] The distribution assemblies have a switchgear arrangement so that the electric connection to a subsea cable can be broken. This can typically occur during malfunction of a subsea cable or wind turbine, or during other maintenance.

[0006] To connect the subsea cables to the subsea high-voltage electric power distribution assembly, the respective subsea cables are terminated with a subsea termination assembly (STA). The STAs are configured to be landed and installed with the subsea high-voltage electric power distribution assembly, such that the subsea cables are connected to the distribution assembly.

[0007] This is discussed in Norwegian patent application publication N020240200, where the STAs are referred to as collection terminals and export terminals.

[0008] Publication US2013286550A1 discloses a subsea power distribution system, where circuit breakers are arranged subsea. A circuit breaker module assembly is landed centrally between respective cable harness assemblies. The respective cable harness assemblies connect to the circuit breaker module assembly by actuation of wet mate connectors after installation subsea.

[0009] W02024208820 presents a solution where umbilical termination modules for a power distribution system are retrievable. The umbilical termination modules are provided with switchgears. In one embodiment, the umbilical termination module is made of two separate modules. One of the umbilical termination modules comprises the switchgear and connects between a subsea transformer module and the other umbilical termination module with wet-mate connectors. This facilitates repair and maintenance of the switchgear. However, during such repair and maintenance, power cannot flow through the umbilical termination module, since it is not connected to the transformer module.Summary of invention

[0010] There is disclosed a subsea high-voltage electric power distribution facility comprising a plurality of first mounting arrangements at respective first positions. It further comprises a support base installed on the seabed, comprising a plurality of second mounting arrangement at respective second positions. It further comprises a plurality of subsea termination assemblies connected to respective subsea cables and engaging with first mounting arrangements. It also comprises a subsea high- voltage power distribution assembly supported on the support base. It further has plurality of switchgear modules engaging with second mounting arrangements, wherein the respective switchgear modules connect to respective subsea termination assemblies with first wet-mate connectors and to the subsea high-voltage power distribution assembly with second wet-mate connectors. The respective switchgear modules are retrievable from their engagement with the second mounting arrangement and the respective subsea termination assemblies are compatible with the second mounting arrangements.

[0011] When stating that the subsea termination assemblies (STA) are compatible with the second mounting arrangements, it is meant that when installed with engagement with the second mounting arrangements, they are in condition to connect to the subsea high-voltage power distribution assembly (“distribution assembly”). In other words, a subsea termination assembly can take the position of a retrieved switchgear module and be connected to the distribution assembly. Due to the engagement with the second mounting arrangement, the STA will be aligned for wet-mating with the distribution assembly. The connection can typically occur with a stroke tool and the wet-mate connector parts are already sufficiently aligned with their opposite connector part. In this way, even if the operator retrieves a switchgear module, such as for repair or maintenance, the operator can still use the STA.

[0012] The subsea cables can for instance be connected to offshore wind turbines. In such embodiments, the subsea high-voltage electric power distribution facility can transmit electric power generated by the offshore wind turbines through an export cable, for instance to shore.

[0013] In some embodiments, the number of subsea termination assemblies can correspond to the number of switchgear modules. However, in other embodiments there may more subsea termination assemblies than switchgear modules. For instance, two subsea termination assemblies can connect to one switchgear module.

[0014] According to some embodiments, the respective subsea termination assemblies comprise a first connector part of the respective first wet-mate connectors and the subsea high-voltage power distribution assembly comprises first connector parts of the second wet-mate connectors. The respective switchgear modules comprise a second connector part of the respective first wet-mate connectors and a second connector part of the respective second wet-mate connectors. Furthermore, the respective first connector parts of the first wet-mate connectors are configured to mate with the respective first connector parts of the second wet-mate connectors.

[0015] Thus, when a switchgear module is retrieved, the STA that was previously connected to the removed switchgear module can be moved to the previous position of the removed switchgear module and can be connected to the distributionassembly with a wet-mate connector. This wet-mate connector is constituted by the remaining connector parts of the first and second wet-mate connectors.

[0016] In some embodiments, the respective subsea termination assemblies comprise first landing guiding arrangements and the respective switchgear modules comprise second landing guiding arrangements. The first landing guiding arrangements are configured to provide alignment of the respective subsea termination assemblies when engaging the second mounting arrangements.

[0017] With the statement “provide alignment of the respective subsea termination assemblies" , it is meant that the subsea termination assemblies will become aligned such that they can connect to the distribution assembly (with wet-mate connector).

[0018] Furthermore, in some embodiments the respective switchgear modules comprise the first mounting arrangements. In such embodiments, when a switchgear module is installed on the support base, an STA can land on the switchgear module when connecting electrically to the switchgear module.

[0019] In other embodiments, the support base comprises the first mounting arrangements. In such embodiments, the respective STAs can thus land on the support base when connecting to the switchgear modules.

[0020] The subsea high-voltage power distribution assembly can in some embodiments comprise a subsea transformer.

[0021] The high-voltage power distribution assembly can be a collector configured to collect electric power from the subsea termination assemblies and transmit the electric power through an export cable.

[0022] In some embodiments, the subsea high-voltage electric power distribution facility further comprises rails on which the subsea termination assemblies and the switchgear modules are supported. The subsea termination assemblies are slidable on the rails between the first and second positions. The rails can be a part of or my be supported by the support base.

[0023] There is also disclosed a method of servicing a subsea high-voltage electric power distribution facility as discussed above. The method comprises the steps of a) disconnecting a switchgear module from the connected subsea termination assembly and the subsea high voltage power distribution assembly by disconnectingthe first and second wet-mate connectors; b) retrieving the disconnected switchgear module to surface; c) moving the disconnected subsea termination assembly from its engagement with the first mounting arrangement to an engagement with the second mounting arrangement; and d) after step c), electrically connecting the moved subsea termination assembly to the subsea high voltage power distribution assembly.

[0024] With this method, the operator can continue to transmit electric power through the moved subsea termination assembly when the switchgear module is not installed.

[0025] In some embodiments of this method, the moved subsea termination assembly comprises a first wet-mate connector part of a first wet-mate connector and the subsea high voltage power distribution assembly comprises a first connector part of a second wet-mate connector. Furthermore, step d) comprises connecting the first connector part of the first wet-mate connector to the the first connector part of the second wet-mate connector.

[0026] There is also disclosed a subsea high-voltage electric power distribution facility comprising a plurality of wet mate connectors with respective first wet mate connector parts and second wet mate connector parts, a subsea high-voltage power distribution assembly comprising the second wet mate connector parts, and an enclosure with penetrators connected to the second wet mate connector parts. The enclosure further comprises a dielectric fluid and high-voltage cabling connected to said penetrators. Furthermore, a plurality of subsea termination assemblies is connected to respective subsea cables and comprise the first wet mate connector parts. The respective subsea termination assemblies further comprise a switchgear.

[0027] With such a subsea high-voltage electric power distribution facility, the subsea high-voltage power distribution assembly does not need to have switchgears. Consequently, if a switchgear malfunctions and needs to be retrieved to surface for repair or replacement, the operator needs only to retrieve one subsea termination assembly (STA). I.e. the operator does not need to retrieve the entire subsea high- voltage electric power distribution assembly. Furthermore, the operator can maintain operation during such repair or replacement.

[0028] In some embodiments, the subsea high-voltage power distribution assembly can comprise a subsea transformer. The subsea high-voltage power distribution assembly is then often referred to as a subsea substation.

[0029] The subsea termination assemblies can connect to a plurality of offshore wind turbines.

[0030] The connection between the second wet mate connector parts and the penetrators of the subsea high-voltage power distribution assembly can in some embodiments be without a jumper, i.e. be jumperless.

[0031] In some embodiments, the respective subsea termination assemblies can comprise a subsea termination assembly enclosure filled with a dielectric fluid, wherein the subsea termination assembly enclosure encloses said switchgears.

[0032] The respective subsea termination assemblies may further comprise a main structure. Furthermore, a landing guiding means, a lifting interface, and the subsea termination assembly enclosure can be attached to the main structure. It shall be understood that the term attached to herein means directly or indirectly attached to.

[0033] There is also disclosed herein a high-voltage subsea termination assembly comprising a wet-mate connector part of a wet-mate connector and a switchgear connected to the wet-mate connector part.

[0034] In some embodiments, the high-voltage subsea termination assembly can further comprise a subsea termination assembly enclosure filled with a dielectric fluid, wherein the subsea termination assembly enclosure encloses the switchgear.

[0035] The dielectric fluid can typically be oil.

[0036] The high-voltage subsea termination assembly may further comprise a landing guiding means, a lifting interface, a subsea termination assembly jumper connecting the switchgear to the wet mate connector part, and a main structure supporting the wet mate connector part, the landing guiding means, the lifting interface, and the switchgear.

[0037] The high-voltage subsea termination assembly (STA) also advantageously includes penetrators extending through the walls of the STA enclosure.

[0038] Also disclosed herein is a method of repairing or replacing a switchgear of a subsea high-voltage electric power distribution facility which is installed on the seabed, and which comprises a subsea high-voltage power distribution assembly that connects to a plurality of subsea termination assemblies that connect subsea cables to the subsea high-voltage power distribution assembly. The method comprises the following steps: i) disconnecting a wet mate connector by moving a first wet mate connector part out of engagement with a second wet mate connector part of the wet mate connector, wherein the first wet mate connector part is part of one of said subsea termination assemblies and the second wet mate connector part is part of the subsea high-voltage power distribution assembly; ii) retrieving the said one of said subsea high-voltage power distribution assemblies to surface; iii) installing a subsea termination assembly with a functioning switchgear at the subsea high-voltage electric power distribution facility; and iv) connecting the first wet mate connector part of the subsea termination assembly of step iii) to the second wet mate connector part.

[0039] The skilled person will appreciate that the malfunctioning switchgear of the STA that is retrieved to surface may be repaired or may be replaced with another switchgear.

[0040] With this method, the operator can still operate the subsea high-voltage electric power distribution facility while repairing or replacing the malfunctioning switchgear. Furthermore, since the STA is much smaller and lighter than the subsea HV power distribution assembly, the equipment needed to perform this operation (i.e. retrieve the STA) will be lighter and smaller than what would be needed for retrieving the entire subsea HV power distribution assembly.

[0041] It shall be understood that this method may involve an STA as discussed herein or a subsea high-voltage electric power distribution facility as discussed herein.

[0042] With the term high voltage is herein meant voltages above 10 kV.

[0043] The switchgear is considered any arrangement suitable for breaking or closing an electric circuit, such as a disconnector or a breaker,Detailed description of the invention

[0044] While various features have been discussed in general terms above, some more detailed and non-limiting examples will be discussed in the following with reference to the drawings, in whichFig. 1 is a schematic side-view of a subsea high-voltage power distribution facility;Fig. 2 is a schematic side-view of the facility of Fig. 1 , wherein a switchgear module is being lifted off and away from the facility;Fig. 3 is a schematic side-view of the facility of Fig. 1 and Fig. 2, wherein an STA module has been moved to the previous position of the switchgear module;Fig. 4 is a schematic top-view of the facility, showing two of four switchgear modules having been removed;Fig. 5 is a schematic side-view of another embodiment of a subsea high-voltage power distribution facility, wherein a switchgear module is being lifted off and away from the facility;Fig. 6 is a schematic side-view of the facility of Fig. 5, showing an STA module being lowered onto the previous position of the removed switchgear module;Fig. 7 is a sideview of a subsea high-voltage power distribution assembly and a switchgear module which is about to be installed;Fig. 8 is an enlarged sideview of the equipment shown in Fig. 7, and a subsea termination assembly being installed;Fig. 9 corresponds to Fig. 8, however with the subsea termination assembly in an installed state;Fig. 10 is a side view showing an STA connected directly to the distribution assembly;Fig. 11 is an enlarged perspective view of a part of the subsea high-voltage power distribution assembly;Fig. 12 is a schematic diagram of a subsea high-voltage power distribution facility according to prior art;Fig. 12a is a schematic diagram of a subsea termination assembly according to prior art;Fig. 13 is a schematic diagram of another subsea high-voltage power distribution facility according to prior art;Fig. 14 is a schematic diagram of a novel subsea high-voltage power distribution facility;Fig. 14a is a schematic diagram of a novel subsea termination assembly;Fig. 15 is a schematic diagram of another novel subsea high-voltage power distribution facility;Fig. 16 is a simplified, schematic perspective view of a novel subsea termination assembly; andFig. 17 is a schematic side view of a novel subsea termination assembly.

[0045] Fig. 1 depicts a schematic diagram of a subsea high-voltage power distribution facility 201 . It has a support base 203, such as a template or a mudmat. The support base 203 supports a subsea HV power distribution assembly 205 (in the following referred to as “distribution assembly). In the shown embodiment, the distribution assembly 205 is a subsea transformer. In other embodiments, it may be a collector, configured to collect electric power from a number of sources and transmit it through one cable or at least a lower number of cables. An export cable 204 connects to the distribution assembly 5. The export cable 204 can for instance extend to shore.

[0046] Also supported by the support base 203 is a plurality of subsea termination assemblies (STA’s) 210. To each STA 210 there is connected a subsea cable 211. The subsea cables 211 can for instance be connected to offshore wind turbines.

[0047] The STAs 210 connect to the distribution assembly 205 via a switchgear module 209. The switchgear module 209 can be connected to and disconnected from the distribution assembly 205 and the STA 210 by means of wet-mate connectors.

[0048] A first wet-mate connector 212 is arranged between the STA 210 and the switchgear module 209. The first wet-mate connector 212 has a first connector part 212a attached to the STA 210 and a second connector part 212b attached to the switchgear module 209.

[0049] A second wet-mate connector 214 is arranged between the switchgear module 209 and the distribution assembly 205. The second wet-mate connector 214 has a first connector part 214a attached to the distribution assembly 205 and a second connector part 214b attached to the switchgear module 209.

[0050] It will be appreciated that the schematic figures are single-line diagrams, such that, for example, even if only one wet-mate connector is depicted, in a practical embodiment there may be several. For instance, for a three-phase system, there would be three wet-mate connectors where only one is shown in the figures.

[0051] In some instances, for instance if the switchgear module 209 malfunctions or needs maintenance, it can be disconnected from the STA 210 and from the distribution assembly 205. Disconnection can for instance take place with an ROV (not shown) or actuators (not shown) configured to operate the first and second wetmate connectors 212, 214. After disconnection, the switchgear 209 can be raised to surface. Fig. 2 illustrate the switchgear module 209 being retrieved to a not shown surface vessel.

[0052] To enable operation of the STA 210, which previously was connected to the distribution assembly 205 via the switchgear module 209, the STA 210 can be moved towards and can be connected to the distribution assembly 205. This is shown in Fig. 3. In this situation, the first connector part 212a of the first wet-mate connector 212 connects to the first connector part 214a of the second wet-mate connector 214.

[0053] When the STA 210 is in its original position, i.e. a first position 40a, it is in engagement with a first mounting arrangement 50a. Then, when it is moved to the position where it connects directly to the distribution assembly 205, a second position 40b, as shown in Fig. 3, it is in engagement with a second mounting arrangement50b. The first and second mounting arrangements 50a, 50b are merely schematically illustrated. They can typically include inclined guide faces, guide funnels that receive guide pins, or similar components used to ensure that the STA 210 and the switchgear module 209 is correctly positioned when in the installed state. Correct position of the STA 210 and the switchgear module 209 must be ensured to enable operation of the first and second wet-mate connectors 212, 214.

[0054] Fig. 4 depicts the subsea HV power distribution system 201 schematically from above. In the situation shown in Fig. 4, two of four original switchgear modules 209 has been removed. One STA 210 has been moved and connected directly to the distribution assembly 205. First and second mounting arrangements 50a, 50b are schematically shown.

[0055] In the embodiment depicted with Fig. 1 to Fig. 4, the subsea HV power distribution facility 201 comprises rails 216 on which the STAs 210 and switchgear modules 209 are supported. The STAs 210 are configured to slide on the rails 216 so that they can move between the position shown in Fig. 2 and the position shown in Fig. 3, i.e. towards or away from the distribution assembly 205. To provide this movement, the operator may use a stroke tool or another type of actuator.

[0056] To avoid that the subsea cable 211 prevents the movement of the STA 210, the subsea cable 211 can have a curved shape, such as an S-shape or a U-shape (not shown), proximate to STA 210.

[0057] As shown in Fig. 3, the moved STA 210 connects directly to the distribution assembly 205.

[0058] While the embodiment discussed above includes rails 216 to enable a horizontal movement of the STA 210, the embodiment depicted in Fig. 5 and Fig. 6 has another solution.

[0059] The situation shown in Fig. 5 corresponds to the situation shown in Fig. 2, which was discussed above. Instead of sliding the STA 210 from the first position 40a to the second position 40b, the STA 210 is lifted. I.e. the STA 210 is lifted away from the first position 40a and landed at the second position 40b.

[0060] In this embodiment, the first and second mounting arrangements 50a, 50b comprise funnels. The funnels are fixed with respect to the support base 203.Furthermore, the STA 210 comprises a first landing guide arrangement 150a and the switchgear module 209 comprises a second landing guide arrangement 150b. In the shown embodiment, the first and second landing guide arrangements 150a, 150b comprise downwardly protruding cone elements. The cone elements are configured to engage with the first and second alignment elements 50a, 50b when landing. This will ensure proper positioning of the STA 210 and of the switchgear module 209 when landing on the support base 203.

[0061] As the skilled person will appreciate, other types of alignment elements and landing guide arrangements are possible. For instance, guide posts can extend upwards from the support base 203 and can interact with guide apertures attached to the switchgear module 209 and the STA 210.

[0062] Notably, the the first landing guide arrangement 150a the STA 210 will fit with both the first mounting arrangement 50a at the first position 40a and with the second second mounting arrangement 50b at the second position 40b. In other words, the first landing guiding arrangement 150a, of the STA 210, is compatible with the first mounting arrangement 50a and with the second mounting arrangement 50b. In this way, to move the STA 210 from the initial first position 40a shown in Fig. 5 to the second position 40b, adjacent the distribution assembly 205, the operator can lift the STA 210 off from the first mounting arrangement 50a and put it back down, engaging with the second mounting arrangement 50b at the second position 40b. The first connector part 212a of the first wet-mate connector 212 will then be aligned and ready to connect to the first connector part 214a of the second wet-mate connector 214.

[0063] To enable the lifting and movement of the STA 210 between the first and second positions 40a, 40b, the subsea cable 211 can advantageously have an S- shape or a U-shape (not shown).

[0064] With this embodiment, depicted in and discussed above with reference to Fig. 5 and Fig. 6, one will not need an actuator or the like to move the STA 210. However, the operator will need a lifting arrangement, such as a crane on a surface vessel (not shown).

[0065] Fig. 7 shows a subsea high-voltage electric power distribution facility 301 being installed. It comprises a subsea high-voltage power distribution assembly 305(herein also referred to as “distribution assembly”) supported on a support base 303 at the seabed. The distribution assembly 305 has a first connector part 314a of a second wet-mate connector 314 (Fig. 8).

[0066] Also shown in Fig. 7 is a switchgear module 309, which is about to be installed next to the distribution assembly 305. The switchgear module 309 has a second connector part 314b of the second wet-mate connector 314 (Fig. 8).

[0067] The switchgear module 309 comprises a framework 309a and a switchgear 309b. Jumpers 306 extend between the switchgear 309b and the second connector part 314b of the second wet-mate connector 314.

[0068] Two guideposts 302 are installed, protruding upwards from the support base 303. The switchgear module 309 will engage the guideposts 302 during landing.

[0069] When landing on the support base 303, the switchgear module 309 will engage with a second mounting arrangement 350b which is fixed with respect to the support base 303. In particular, the switchgear module 309 comprises a second landing guiding arrangement 450b which is configured to engage with the second mounting arrangement 350b. The second mounting arrangement 350b is arranged at a second position 340b. The engagement between the switchgear module 309 and the second mounting arrangement 350b will ensure that the first and second connector parts 314a, 314b of the second wet-mate connector 314 are aligned so that they can mate.

[0070] Similar to the embodiment shown in Fig. 4, there is a plurality of second mounting arrangements 350b (as also appears from Fig. 11 ).

[0071] An export cable 304 connects to the distribution assembly 305. The export cable 304 can for instance extend to shore.

[0072] Fig. 8 shows the switchgear module 309 in a landed position. The second connector part 314b has been moved, such as with a stroke tool (not shown), into connected engagement with the first connector part 314a of the second wet-mate connector 314.

[0073] Also shown in Fig. 8 is a subsea termination assembly (STA) 310, which is about to be landed and secured to the switchgear module 309. The STA 310 and theswitchgear module 309 both comprise guiding means 308 that engage during landing of the STA 310.

[0074] The STA 310 comprises a first connector part 312a of a first wet-mate connector 312 (Fig. 9), while the switchgear module 309 comprises a second connector part 312b of the first wet-mate connector 312. The STA 310 is connected to a subsea cable 311 .

[0075] Furthermore, the switchgear module 309 comprises a first mounting arrangement 350a that engages with the STA 310 when landing. The STA 310 comprises a first landing guiding arrangement 450a that engages with the first mounting arrangement 350a of the switchgear module 309. This ensures alignment between the landed STA 310 and the switchgear module 309, such that the first connector part 312a and the second connector part 312b of the first wet-mate connector 312 can connect after landing. The first mounting arrangement 350a is arranged at a first position 340a.

[0076] Fig. 9 depicts the landed state of the STA 310, with the first wet-mate connector 312 in a connected state. In this state, the subsea cable 311 is electrically connected to the distribution assembly 305 through the switchgear module 309.

[0077] Fig. 10 depicts a situation where the switchgear module 309 has been retrieved to surface, such as for inspection or maintenance. The STA 310 is then landed on the support base 303 with engagement with the second mounting arrangement 350b. In this position, the first connector part 312a of the first wet-mate connector 312 can connect with the first connector part 314a of the second wet-mate connector 314.

[0078] The operator thus has the possibility of retrieving the switchgear module 309, while still connecting the subsea cable 311 to the distribution assembly 305.

[0079] Fig. 11 depict the embodiment shown in Fig. 7 to Fig. 10 with a perspective view. In this embodiment, four switchgear modules 309 can be landed on the support base 303 and connect to the distribution assembly 305. I.e. the support base 303 comprises four second mounting arrangements 350b. Only one switchgear module 309 is shown in Fig. 11. An STA 310 has landed on the switchgear module 309.

[0080] Fig. 12 depicts a schematic diagram of a subsea high-voltage power distribution facility 101 according to the prior art. A support base 103, such as a mudmat, is schematically shown with the dashed line. The subsea HV power distribution facility 101 further comprises a subsea HV power distribution assembly 105 (herein also referred to as “distribution assembly”).

[0081] In the embodiment shown in Fig. 12, the distribution assembly 105 is in the form of a subsea substation. It comprises a transformer 107 and a switchgear assembly 108 connected to the transformer 107.

[0082] The subsea HV power distribution facility 101 further comprises a plurality of subsea termination assemblies (STA) 110. The STA 110 is an arrangement connected to the end of a subsea cable 111. Furthermore, the STA 110 is configured to be landed, such as on the support base 103, at the subsea HV power distribution facility 101 , so that the subsea cable 111 can be connected to the distribution assembly 105. Hence, the STA 110 is typically provided with lifting interfaces and guiding means (not shown) to facilitate the landing and installation at the seabed.

[0083] After landing of the STA 110, electric connection is made to the distribution assembly 105 by moving wet mate connectors 113 to a connected mode. The respective wet mate connectors 113 comprise a first wet mate connector part 113a and a second wet mate connector part 113b. These can be connected and disconnected subsea, when surrounded by the ambient water. Such connection and disconnection can typically take place by operation of an ROV (remotely operated vehicle) or an actuator arranged at the wet mate connector 113.

[0084] The switchgear assembly 108 comprises a plurality of switchgears 109. The switchgears 109, as well as the transformer 107, are arranged inside an enclosure 115 of the distribution assembly 105. The enclosure 115 is filled with a dielectric fluid, typically oil.

[0085] The wet mate connectors 113 connect to respective penetrators 117 with a jumper 119. The penetrators 117 extend through a wall of the enclosure 115 of the distribution assembly 105.

[0086] Schematically shown in Fig. 12 are also a plurality of offshore wind turbines 121 . The offshore wind turbines 121 connect to the STAs 110 with the subsea cables 111 , which in such embodiments are often referred to as inter-array cables.

[0087] The STA 110 is installed on the end of the subsea cable 111 before the STA 110 is installed subsea.

[0088] Fig. 13 schematically depicts another subsea HV power distribution facility 101 according to the prior art. In this embodiment, the subsea HV distribution assembly 105 is referred to as a collector. It does not comprise a subsea transformer. However, it comprises a switchgear assembly 108 with several switchgears 109.

[0089] Similar to the embodiment shown in Fig. 12, a plurality of STAs 110 are installed and connected to the distribution assembly 105 with wet mate connectors 113. The wet mate connectors 113 are connected to penetrators 117 extending through the wall of the enclosure 115.

[0090] Fig. 12a depicts a schematic diagram of an STA 110. It comprises a main structure 125 and a first wet mate connector part 113a. It is arranged on the end of a subsea cable 111. The main structure 125 can comprise guiding means for facilitating landing on the seabed and lifting interfaces for handling the STA 110.

[0091] While the above discussion with reference to Fig. 12, Fig. 13, and Fig. 12a presented solutions of the prior art, the following discussion will present novel solutions.

[0092] Fig. 14 depicts a schematic diagram of a novel subsea HV power distribution facility 1 , which in many respects resembles the one shown in Fig. 12. The skilled reader will recognize several components from the above discussion of prior art, for instance the subsea transformer 7 arranged inside the enclosure 15. High voltage (HV) cabling 16 is arranged inside the enclosure 15. The HV cabling 16 connects the subsea transformer 7 to the penetrators 17.

[0093] However, the subsea HV power distribution facility 1 comprise several STAs 10 that each have a switchgear 9. This removes the need for a switchgear assembly 108 as a part of the distribution assembly 5 (cf. prior art examples in Fig. 12 and Fig. 13).

[0094] Also differing from the prior art examples, in the embodiment shown in Fig.14, the wet mate connector 13 is rigidly connected to the distribution assembly 5. In particular, the second wet mate connector part 13b of the wet mate connector 13 is rigidly connected, directly or indirectly, to the penetrator 17. There may be additional interposed parts between the penetrator 17 and the second wet mate connector part 13b of the distribution assembly 5, but such possible parts are rigid (e.g. no flexible cable). This means that the electric connection between the second wet mate connector part 13b and the penetrator 17 is jumperless in the shown embodiment. The skilled reader will, however, appreciate that a jumper could be arranged between the second wet mate connector part 13b and the penetrator 17.

[0095] Fig. 15 depicts an embodiment that in many aspects resembles the prior art solution shown in Fig. 13. However, as with the example shown in Fig. 14, the STAs 10 comprise a switchgear 9. High voltage cabling, which in the shown embodiment is in the form of a bus bar 16, is arranged inside an enclosure 15 filled with a dielectric fluid, such as oil. The bus bar 16 connects to the penetrators 17.

[0096] By having the switchgears 9 in the respective STAs 10, the operator is enabled to repair a malfunctioning switchgear 9 simply by retrieving one STA 10 instead of retrieving the entire distribution assembly 5.

[0097] Another advantage with the STA 10 with the switchgear 9, is that switchgears 9 can be retrofitted to existing distribution assemblies 5, such as collectors or substations.

[0098] Fig. 14a depicts one STA 10. It is connected to the end of a subsea cable 11 . It has a schematically illustrated main structure 25 and a subsea termination assembly enclosure 12 (STA enclosure). The STA enclosure 12 is filled with oil and encloses the switchgear 9. Two penetrators 17 are arranged, extending through the walls of the STA enclosure 12. Opposite of the subsea cable 11 , with respect to the switchgear 9, is a first wet mate connector part 13a.

[0099] In the embodiment of the STA 10 shown in Fig. 14a, there is an STA jumper 14 connecting one of the penetrators 17 to the first wet mate connector part 13a. The STA jumper 14 provides flexibility, such that the first wet mate connector part 13a can be moved during connection or disconnection of the wet mate connector 13.

[0100] Fig. 16 depicts a simplified, schematic perspective view of an STA 10. A subsea cable 11 (of which a bend restrictor is shown in Fig. 16), such as an interarray cable, connects to the main structure 25 of the STA 10. The main structure 25 is in the shown embodiment is schematically shown as a box. However, it could for instance be a framework made up beams.

[0101] The STA 10 comprises a first wet mate connector part 13a of the wet mate connector 13. The first wet mate connector part 13a is supported by the main structure 25.

[0102] Also supported by the main structure 25 are landing guiding means 27, configured for guiding the STA 10 when landing subsea. In the shown embodiment, the landing guiding means 27 is in the form of guide sleeves adapted for receiving guide posts installed subsea. During landing or retrieval, the STA 10 can be lifted at the lifting interfaces 29 on the main structure 25, such as lift eyes.

[0103] Fig. 17 depicts the STA 10 with a simplified, schematic side-view. The switchgear 9 is supported by the main structure 25 and is merely schematically or symbolically illustrated.

[0104] The switchgear 9 is arranged inside the STA enclosure 12 which is filled with a dielectric fluid, typically oil. The STA jumper 14 connects between one of the penetrators 17 and the first wet mate connector part 13a.

[0105] While not shown in the embodiments discussed herein, the skilled person will appreciate that in some embodiments, the STA 10 could be connected to the subsea cable 11 with a dry mate connector (not shown).

Claims

Claims1 . A subsea high-voltage electric power distribution facility (201 , 301 ) comprising- a plurality of first mounting arrangements (50a, 350a) at respective first positions (40a, 340a);- a support base (203, 303) installed on the seabed, comprising a plurality of second mounting arrangements (50b, 350b) at respective second positions (40b, 340b);- a plurality of subsea termination assemblies (210, 310) connected to respective subsea cables (211 , 311 ) and engaging with first mounting arrangements (50a, 350a);- a subsea high-voltage power distribution assembly (205, 305) supported on the support base (203, 303);- a plurality of switchgear modules (209, 309) engaging with second mounting arrangements (50b, 350b), wherein the respective switchgear modules (209, 309) connect to respective subsea termination assemblies (210, 310) with first wet-mate connectors (212, 312) and to the subsea high-voltage power distribution assembly (205, 305) with second wet-mate connectors (214, 314); wherein the respective switchgear modules (209, 309) are retrievable from their engagement with the second mounting arrangement (50b, 350b) and wherein the respective subsea termination assemblies (210, 310) are compatible with the second mounting arrangements (50b, 350b).

2. A subsea high-voltage electric power distribution facility (201 , 301 ) according to claim 1 , wherein- the respective subsea termination assemblies (210, 310) comprise a first connector part (212a, 312a) of the respective first wet-mate connectors (212, 312);- the subsea high-voltage power distribution assembly (205, 305) comprises first connector parts (214a, 314a) of the second wet-mate connectors (214, 314);- the respective switchgear modules (209, 309) comprise a secondconnector part (212b, 312b) of the respective first wet-mate connectors (212, 312) and a second connector part (214b, 314b) of the respective second wet-mate connectors (214, 314); and wherein the respective first connector parts (212a, 312a) of the first wet-mate connectors (212, 312) are configured to mate with the respective first connector parts (214a, 314a) of the second wet-mate connectors (214, 314).

3. A subsea high-voltage electric power distribution facility (201 , 301 ) according to one of the preceding claims, wherein the respective subsea termination assemblies (210, 310) comprise first landing guiding arrangements (150a, 450a) and the respective switchgear modules (209, 309) comprise second landing guiding arrangements (150b, 450b), wherein the first landing guiding arrangements (150a, 450a) are configured to provide alignment of the respective subsea termination assemblies (210, 310) when engaging the second mounting arrangements (50b, 350b).

4. A subsea high-voltage electric power distribution facility (301 ) according to one of the preceding claims, wherein the respective switchgear modules (309) comprise the first mounting arrangements (350a).

5. A subsea high-voltage electric power distribution facility (201 ) according to one of claims 1 to 3, wherein the support base (203) comprises the first mounting arrangements (50a).

6. A subsea high-voltage electric power distribution facility (201 , 301 ) according to one of the preceding claims, wherein the subsea high-voltage power distribution assembly (205, 305) comprises a subsea transformer.

7. A subsea high-voltage electric power distribution facility (201 , 301 ) according to one of claims 1 to 5, wherein the high-voltage power distribution assembly (205, 305) is a collector configured to collect electric power from the subsea termination assemblies (210, 310) and transmit the electric power through an export cable (204, 304).

8. A subsea high-voltage electric power distribution facility (201 ) according to one of the preceding claims, further comprising rails (216) on which the subsea termination assemblies (210) and the switchgear modules (209) are supported, wherein the subsea termination assemblies (210) are slidable on the rails (216) between the first and second positions (40a, 40b).

9. A method of servicing a subsea high-voltage electric power distribution facility (201 , 301 ) according to one of the preceding claims, comprising a) disconnecting a switchgear module (209, 309) from the connected subsea termination assembly (210, 310) and the subsea high voltage power distribution assembly (205, 305) by disconnecting the first and second wet-mate connectors (212, 214, 312, 314); b) retrieving the disconnected switchgear module (209, 309) to surface; c) moving the disconnected subsea termination assembly (210, 310) from its engagement with the first mounting arrangement (50a, 350a) to an engagement with the second mounting arrangement (50b, 350b); and d) after step c), electrically connecting the moved subsea termination assembly (210, 310) to the subsea high voltage power distribution assembly (205, 305).

10. A method according to claim 9, wherein the moved subsea termination assembly (210, 310) comprises a first wet-mate connector part (212a, 312a) of a first wet-mate connector (212, 312) and the subsea high voltage power distribution assembly (205, 305) comprises a first connector part (214a, 314a) of a second wet-mate connector (214, 314), and wherein step d) comprises connecting the first connector part (212a, 312a) of the first wet-mate connector (212) to the first connector part (214a, 314a) of the second wet-mate connector (214, 314).11 . A subsea high-voltage electric power distribution facility (1 ) comprising- a plurality of wet mate connectors (13) with respective first wet mate connector parts (13a) and second wet mate connector parts (13b);- a subsea high-voltage power distribution assembly (5) comprising the second wet mate connector parts (13b), an enclosure (15) withpenetrators (17) connected to the second wet mate connector parts (13b), the enclosure (15) further comprising a dielectric fluid and high-voltage cabling (16) connected to said penetrators (17);- a plurality of subsea termination assemblies (10) connected to respective subsea cables (11 ) and comprising the first wet mate connector parts (13a); wherein the respective subsea termination assemblies (10) further comprise a switchgear (9).

12. A subsea high-voltage electric power distribution facility (1 ) according to claim 11 , wherein the subsea high-voltage power distribution assembly (5) comprises a subsea transformer (7).

13. A subsea high-voltage electric power distribution facility (1 ) according to claim 11 or claim 12, wherein the subsea termination assemblies (10) connect to a plurality of offshore wind turbines (21 ).

14. A subsea high-voltage electric power distribution facility (1 ) according to one of claims 11 to 13, wherein the connection between the second wet mate connector parts (13b) and the penetrators (17) of the subsea high-voltage power distribution assembly (5) is jumperless.

15. A subsea high-voltage electric power distribution facility (1 ) according to any one of claims 11 to 14, wherein the respective subsea termination assemblies (10) comprise a subsea termination assembly enclosure (12) filled with a dielectric fluid, wherein the subsea termination assembly enclosure (12) encloses said switchgears (9).

16. A subsea high-voltage electric power distribution facility (1 ) according to claim 15, wherein the respective subsea termination assemblies (10) further comprise a main structure (25) and wherein a landing guiding means (27), a lifting interface (29), and the subsea termination assembly enclosure (12) are attached to the main structure (25).

17. A high-voltage subsea termination assembly (10) comprising a wet-mate connector part (13a) of a wet-mate connector (13) and a switchgear (9) connected to the wet-mate connector part (13a).

18. A high-voltage subsea termination assembly (10) according to claim 17, further comprising a subsea termination assembly enclosure (12) filled with a dielectric fluid, wherein the subsea termination assembly enclosure (12) encloses the switchgear (9).

19. A high-voltage subsea termination assembly (10) according to one of claims 17 and 18, further comprising landing guiding means (27), a lifting interface (29), a subsea termination assembly jumper (14) connecting the switchgear (9) to the wet mate connector part (13a), and a main structure (25) supporting the wet mate connector part (13a), the landing guiding means (27), the lifting interface (29), and the switchgear (9).

20. A method of repairing or replacing a switchgear (9) of a subsea high-voltage electric power distribution facility (1 ) which is installed on the seabed, and which comprises a subsea high-voltage power distribution assembly (5) that connects to a plurality of subsea termination assemblies (10) that connect subsea cables (11 ) to the subsea high-voltage power distribution assembly (5), the method comprising i) disconnecting a wet mate connector (13) by moving a first wet mate connector part (13a) out of engagement with a second wet mate connector part (13b) of the wet mate connector (13), wherein the first wet mate connector part (13a) is part of one of said subsea termination assemblies (10) and the second wet mate connector part is part of the subsea high- voltage power distribution assembly (5); ii) retrieving the said one of said subsea high-voltage power distribution assemblies (10) to surface; iii) installing a subsea termination assembly (10) with a functioning switchgear (9) at the subsea high-voltage electric power distribution facility (1 ); and iv) connecting the first wet mate connector part (13a) of the subseatermination assembly (10) of step iii) to the second wet mate connector part (13b).

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