Pressure compensator and subsea transformer system

Abstract

In at least one embodiment, the pressure compensator (1) is configured for subsea-use and comprises: - a first bellows chamber (21) configured to be filled with a first insulation liquid (61), - an electrical equipment (3) placed in the first bellows chamber (21), and - electrical feedthroughs (4) connecting the electrical equipment (3) with an exterior of the pressure compensator (1).

Description

[0001] P2024,0539 WO N2 / P240007WO02 May15,2025 -1 - Description PRESSURE COMPENSATOR AND SUBSEA TRANSFORMER SYSTEMA pressure compensator is provided. Moreover, a sub seatransformer system comprising such a pressure compe nsator isalso provided. DocumentCN 108305748 B relatesto an integrated corrugatedtube type underwater transformer. The transformer c omprises ashell, corrugated tubes, a base, guiding columns an d atransformer winding; the shell is arranged on the b ase; thecorrugated tubesare integrated in the middle part oftheshell to form a corrugated tube type pressure compe nsator;fourguiding columnsare arranged on the periphery in theshell at intervals; the transformer winding is moun ted in theshell;and connecting-inserting partsare arranged on the two sidesofthe bottom ofthe shellrespectively.Document EP 3241983 A1 discloses a compartment fo r a subseadevice that comprises a pressure compensator defini ng aninner enclosure of the compartment, the inner enclo surehaving a variable volume, wherein the inner enclosu re issuitable for housing at least an electrical or hydr auliccomponent of the subsea device housed inside the in nervolume.Document US 6456179 B1 discloses a container with an oilimmersed core and windings that has corrugated wall s. Bushinginsulators have pressure-resistant and water-resist ant cableshoes.A tankencompassesanothercontainerfilled withinsulating oil and has pressure-resistant cable bus hing andconnectors for electrical connections of the transf ormer. P2024,0539 WO N2 / P240007WO02 May15,2025 -2 - DocumentsWO 2015 / 104050 A1,WO 2021 / 185720 A1 and US 2015 / 0167704 A1 referto subsea installations.Document US 2011 / 0203379 Al refers to a subsea pres surecompensator.A problem to be solved is to provide a subsea trans formersystem that has a reduced number of separate compon ents.Thisobjectisachieved,interalia,bya pressurecompensator and by a subsea transformer system as d efined inthe independent claims. Exemplary further developme ntsconstitute the subject-matter of the dependent clai ms.For example, the pressure compensator is for subsea use,especiallyin saltwater.The pressure compensator comprisesa first bellows chamber to be filled with a first i nsulationliquid, an electrical equipment, or any other equip ment wherelikewise fluid compensation and / or cooling and / or i nsulationis needed, placed in the first bellows chamber, andelectrical feedthroughs connecting the electrical e quipmentwith an exteriorofthe pressure compensator.The pressure compensator can be used in a subsea tr ansformersystem. Thus, a subsea transformer system with a mi nimizednumberofcomponentscan be achieved,forexample.Normally, liquid filled subsea transformers have ta nk andexternal pressure compensators to equalize the inte rnalpressure close to the surrounding water pressure. A uxiliarypower transformers are usually placed inside a cont rol pod P2024,0539 WO N2 / P240007WO02 May15,2025 -3 -but in case of an auxiliary transformer failure the completepod hasto be retrieved,forexample.As described herein, the transformer or any other l iquid-immersed and / or cooling-requiring device and pressu recompensation functions have been combined into a sa me vesselhaving double-barrier feature, for example. In othe r words,the transformer active part with / or any other elect ricaldevice, that is, the electrical equipment, is put i nside ofthe pressure compensator. In this solution, there a re lesscomponents.The parasite liquid volume of the compensator can t hus beused to immerse the electrical equipment, like a tr ansformeractive part. With suitable wet-mate subsea connecto rs, thepressure compensator is a separately retrievable un it and / ora nearby control pod can be retrieved without the p ressurecompensator.The double-barrierrequirementcan be fulfilled.Additionally, the compensating position can be visu allymonitored by a remote operate vehicle, ROV, or with simpleposition monitoring.In addition to the before named, the pressure compe nsatordescribed herein can fulfil the new coming IEC subs eastandard IEC 61886-2 Subsea equipment - Part 2: Pow ertransformers, even though an electrical power the p ressurecompensator with the electrical device is configure d for maybe below e.g.50 kVA.Subsea connectors can be single-barrier bulkhead co nnectorswith termination chamber separately to fulfil doubl e-barrierfunctionality to main liquid volume or double-barri erconnectors penetrating directly to a main liquid vo lume, for P2024,0539 WO N2 / P240007WO02 May15,2025 -4 -example. Termination chamber can be compensated wit hdedicated compensator or with a connection to the m ainpressure compensatorintermediate space. According to atleastone embodiment,the pressurecompensator is configured for subsea use. This mean s, forexample, that the pressure compensator is made on a n exteriorwith materials that withstand corrosion resulting f rom saltwater. In addition, the pressure compensator may beconfigured to be put in deep water, for example, at a depthofatleast0.1 km orofatleast0.5 km and / orof atmost5 km or of at most 2 km. That is, the pressure comp ensator isconfigured to be operated at comparably high enviro nmentalpressures and possibly still being waterproof. Henc e, ifpresent,anyvalvesorcavitiesare configured for pressurechanges and absolute pressures from atmospheric pre ssure tosubsea pressure. In addition, the pressure compensa tor may beconfigured for typical temperatures present in subs eaconditions,like around 4 °C.According to at least one embodiment, the first bel lowschamber is configured to be filled with a first ins ulationliquid. For example, the first insulation liquid is atransformer insulation liquid, like a transformer o il. Thefirst insulation liquid may be the only fluid prese nt in thefirst bellows chamber. The term ‘fluid’ may refer t o anyliquid and gas and mixture thereof. Especially, the firstbellows chamber may be free of any gases or free of anysignificantamountofgases.For example, the term ‘bellows chamber’ or “bellows ’ meansthat it is an elastic vessel that can be compressed whenpressure is applied to the outside of the vessel, o r P2024,0539 WO N2 / P240007WO02 May15,2025 -5 - correspondinglyextended underdecreased pressure;respectively, it is compressed or extended when the volume ofthe inner liquid changes due to temperature changes . When thepressure isreleased to normalpressure,like 1013 hPa,thevessel will return to its original shape when the t emperatureof the fluid is same as originally, provided the ma terial hasnot been stressed past its yield strength. The bell owschamber may be used to deform under pressure and to provide ahermeticsealthatallowsmovement.According to at least one embodiment, the electrica lequipmentispartiallyorcompletelyplaced in the firstbellows chamber. For example, the electrical equipm ent is indirect contact with the first insulation liquid whe n thepressure compensator is filled with the first insul ationliquid. Thus, the electrical equipment may not be p rovidedwith an extra encasing. Hence, the first insulation liquidcan be used, for example, for electrically insulati ng and / orcooling the electricalequipment.It is possible that there is just one electrical eq uipment orthat there is a plurality of electrical equipments, that is,a pluralityofdistinctelectricaldevices.In the following,however, for simplicity only one electrical equipme nt ismentioned although there can be more than one elect ricalequipment.According to at least one embodiment, the electrica lfeedthroughsconnectthe electricalequipmentwith an exteriorofthe pressure compensator.The exterior is,forexample, an electric wiring outside the pressure co mpensator.It is possible that the electrical feedthroughs areconfigured to be in direct contact with seawater at an end P2024,0539 WO N2 / P240007WO02 May15,2025 -6 -remote from the electrical equipment. The electrica lfeedthroughs may be configured to provide electrica linsulation against seawater at the voltages the ele ctricalequipmentisconfigured to workwith. According to atleastone embodiment,the pressurecompensator further comprises a first carrier plate . Forexample,the firstcarrierplate isa plane plate. Inintended use, the first carrier plate may be mechan icallystable and rigid,thatis,the firstcarrierplate maynotsignificantly deform in the intended use of the pre ssurecompensator. Otherwise, the first carrier plate may also havea non-planarshape,like a dome shape.According to at least one embodiment, the first car rier plateis configured to be horizontally arranged. That is, inintended use a normal vector to the first carrier p late maybe aligned vertically,thatis,in parallelwith a vectorofgravity. This applies, for example, with a toleranc e of atmost 20° or of at most 10° or of at most 5°. Otherw ise, thefirst carrier plate may be configured to be arrange dvertically or obliquely, that is, in principle in a ny otherdirection.According to at least one embodiment, the first car rier plateisconfigured to be arranged in a fixed manner.In otherwords, the first carrier plate is not a movable par t.According to at least one embodiment, the electrica lequipment is carried by the first carrier plate. It ispossible that the first carrier plate is the only r igidcomponentofthe pressure compensatoratwhich the electricalequipment is mounted. Thus, the electrical equipmen t may only P2024,0539 WO N2 / P240007WO02 May15,2025 -7 - be in directcontactwith the firstcarrierplate, the firstinsulating liquid upon being filled in the first be llowschamber, and the feedthroughs. The feedthroughs, ho wever, maynot be configured to bear any significant mechanica l forcesresulting from the electrical equipment. Technicall y, theelectrical equipment could be on the bottom plate b ut itwould yield mechanical stress for the wiring due to themovement. Forexample,the electricalequipmenthangson the firstcarrier plate. That is, the electrical equipment is mountedon a bottom side of the first carrier plate. Altern atively,the electrical equipment seats on the first carrier plate.That is, the electrical equipment is mounted on a t op side ofthe first carrier plate. As used herein, a ‘top sid e’ faces asea surface,and a ‘bottom side’facesa seafloor.According to at least one embodiment, the first car rier plateforms part of the first bellows chamber. For exampl e, thefirst carrier plate forms a top side of the first b ellowschamber, especially when the electrical equipment h angs onthe first carrier plate. Otherwise, the first carri er platemay form a bottom side of the first bellows chamber ,especially when the electrical equipment seats on t he firstcarrierplate. According to atleastone embodiment,the pressurecompensator further comprises a second carrier plat e.Analogouslyto the firstcarrierplate,the second carrier plate can be a rigid and / orplane plate and maybe configuredto be horizontally arranged, or also in an arbitrar ydirection.Otherwise,the second carrierplate may also have a non-planarshape,like a dome shape. P2024,0539 WO N2 / P240007WO02 May15,2025 -8 -According to at least one embodiment, the second ca rrierplate isarranged in a movable manner.Thatis,in theintended use of the pressure compensator the second carrierplate maymove atleastattimes.Forexample,the secondcarrier plate may move during a volume compensation of a maintankofa transformersystem.According to at least one embodiment, the second ca rrierplate formspartofthe firstbellowschamber.For example,the second carrier plate forms the bottom side of t he firstbellows chamber, especially when the electrical equ ipmenthangs on the first carrier plate. Otherwise, the se condcarrier plate may form a top side of the first bell owschamber, especially when the electrical equipment s eats onthe firstcarrierplate. According to atleastone embodiment,the pressure compensatorfurthercomprisesa supportframe.For example,the support frame carries the first bellows chamber . That is,for example, the first carrier plate rests on the s upportframe.Bymeansofthe supportframe,the pressure compensatormaybe positioned in the system.According to at least one embodiment, part of the f irstbellows chamber is mounted movably at the support f rame. Forexample,said partisthe second carrierplate.According to at least one embodiment, the first bel lowschamber comprises an interior side wall. For exampl e, theinterior side wall connects the first and second ca rrierplates. Thus, the first bellows chamber may be defi ned by thefirst and second carrier plates together with the i nterior P2024,0539 WO N2 / P240007WO02 May15,2025 -9 -side wall. The interior side wall may be of tubular shape ormay have the shape of a cube jacket. It is possible that theinterior side wall is deformable, for example, to c ompensatefor a movement of the second carrier plate. For exa mple, theinterior side wall is made of a steel sheet or mult iplesheets.According to at least one embodiment, the support f ramecomprises one or a plurality of support rods. The a t leastone support rod may ensure correct positions of the first andsecond carrier plates relative to one another. By w ay ofexample, there is one support rod or there are thre e supportrods or there are four support rods or there are si x supportrods.According to at least one embodiment, the second ca rrierplate is movably mounted at the at least one suppor t rod. Forexample, the at least one support rod is configured to guidethe second carrierplate when moving.The atleast one supportrod maythusbe a guidance rail.According to at least one embodiment, the support r odsconstitute legsofthe pressure compensator.Thus, the pressure compensatormayreston the supportrods. Forsecurerest, the support rods may have an adjustable lengt h and / ormay have hinges and / or may have connectors to be pl acedand / or fixed, for example, in the transformer syste m.According to at least one embodiment, the electrica lequipmentispartlyorcompletelyarranged between the firstcarrier plate and the second carrier plate. For exa mple, thefirst and second carrier plates are arranged in par allel witheach other. P2024,0539 WO N2 / P240007WO02 May15,2025 -10 -For example, the second carrier plate is configured to bebelow the firstcarrierplate and,thus,forming a bottomside of the pressure compensator, for example. Othe rwise, thesecond carrierplate isconfigured to be above the firstcarrier plate and, thus, forming a top side or part of a topside of the pressure compensator and / or of the firs t bellowschamber. In this context, ‘above’ and ‘below’ refer to thedirection of gravity. That is, ‘below’ means closer toEarth’s center of mass and ‘above’ means more dista nt toEarth’s center of mass. Hence, the first and / or sec ondcarrierplatesmaybe aligned horizontallyso that the firstand / or second carrier plate can optionally be align edhorizontally wherein the second carrier plate faces groundand the firstcarrierplate facesheaven.According to at least one embodiment, the first car rier plateand the second carrier plate are congruent, seen in top view.For example, this applies with a tolerance of at mo st 20% orat most 10% or at most 5% of an area content of the firstcarrier plate. However, in the carrier plates do no tnecessarilyhave to be congruent. According to atleastone embodiment,the pressurecompensator further can comprise a connection chamb er. Forexample,the connection chamberisattached to the first bellowschamber.Bywayofexample,the connection chamberis mounted atop the firstcarrierplate,orthe first carrierplate is mounted atop the connection chamber. Possi bly, theconnection chamber may rest on the first connection plate orvice versa. P2024,0539 WO N2 / P240007WO02 May15,2025 -11 -According to at least one embodiment, one or some o r all ofthe electrical feedthroughs comprises a first conne ctor and asecond connector. These connectors may be electrica lconnectors, like plugs. There may be male and femal econnectors.According to at least one embodiment, the first and secondconnectors are located and are correspondingly conn ected witheach other in the connection chamber. Hence, the co nnectionchamber may provide an additional hull around the c onnectors.According to at least one embodiment, the connectio n chamberis configured to be exposed to seawater. Hence, theconnection chamber may form part of an exterior hul l of thepressure compensator. According to atleastone embodiment,the pressurecompensator further comprises a second bellows cham ber. Forexample, the first bellows chamber is arranged in t he secondbellowschamber.Hence,the second bellowschamber mayprovide a hull around the first bellows chamber. He nce, thesecond bellowschambermayprovide some protection forthefirst bellows chamber against environmental effects , likecorrosion. The external bellow can be self-compensa ted orprovided with a dedicated separate compensator.According to at least one embodiment, the second be llowschamberisdefined bythe firstand second carrier platesandby an exterior side wall between the first and seco nd carrierwalls. The first and second bellows chambers may be alignedconcentricallyoralso non-concentricallyrelative to one another. P2024,0539 WO N2 / P240007WO02 May15,2025 -12 -According to at least one embodiment, the second be llowschamberisconfigured to be in directcontactwith seawater.For example, the exterior side wall is made of a sa lt-resistant material, like rubber or another elastome r.According to atleastone embodiment,the pressurecompensator further comprises a supplementary press urecompensator. For example, a first intermediate volu me betweenthe first bellows chamber and the second bellows ch amber isconfigured to be filled with a second insulation li quidand / or the connection chamber encloses a second int ermediatevolume that is configured to be filled with a thirdinsulation liquid.In thiscase,the supplementary pressurecompensator may be configured to compensate for var iations ofthe first intermediate volume and / or the second int ermediatevolume. The corresponding intermediate volume may b e smallerthan a volume of the first bellows chamber. For exa mple, saidintermediate volumesdifferfrom the volume ofthe firstbellows chamber by at least a factor of two or by a t least afactor of five and / or at most by a factor of 10 2 or at mostby a factor of 10. For example, the supplementary p ressurecompensator is mounted on the first carrier plate a nd / or ismounted at the connection chamber. Especially the s econdintermediate volume may also be referred to as a te rminationvolume, the first intermediate volume may also be r eferred tosimplyasintermediate volume.According to at least one embodiment, one or some o r all ofthe electricalfeedthroughsemergesfrom the first bellows chamberwhere the firstbellowschamberisexposed toseawater. Thus, the electrical feedthroughs may dir ectlyleave the pressure compensator at the first carrier plate P2024,0539 WO N2 / P240007WO02 May15,2025 -13 -without any connection chamber if they are double-b arrierconfigured,forexample. According to atleastone embodiment,the pressurecompensator further comprises a visual indicator. F orexample, the visual indicator is configured to visu alize acompression state of the first bellows chamber to t heexterior of the pressure compensator. The visual in dicatormay be based on optical, mechanical, hydraulic and / orelectricprinciples.According to at least one embodiment, the visual in dicatorcomprises a scale and an indication part movable re lative toone another. By means of the scale and the indicati on part,for example, a relative position of the second carr ier platerelative to the support rods may be indicated. Othe rwise, thevisual indicator may be based on an electrical indi cation,like providing electrical data for deriving the com pressionstate.According to at least one embodiment, the electrica lequipment comprises or consists of one or of a plur ality ofthe following components:a transformer,a circuit breaker,an inductor, a capacitor and / or a resistor or any e quipmentwhere likewise fluid compensation and / or cooling an d / orinsulation isneeded.According to at least one embodiment, the electrica lequipmentisconfigured forhandling an electrical powerofat most 2 kVA or of at most 10 kVA or of at most 50 kVA.Alternatively or additionally, said electrical powe r is atleast 1 kVA or is at least 2 kVA or is at least 5 k VA. P2024,0539 WO N2 / P240007WO02 May15,2025 -14 -According to at least one embodiment, a weight of t heelectrical equipment is at most 500 kg or is at mos t 300 kgor is at most 200 kg. Alternatively or additionally , saidweightisatleast50 kg orisatleast100 kg.According to at least one embodiment, an overall vo lume ofthe first bellows chamber is at least 20 l or is at least 50l or is at least 150 l. Alternatively or additional ly, saidoverall volume is at most 2 m 3 or is at most 1 m 3 or is atmost 0.5 m 3. The overall volume may be the volume of thefirst liquid plus the volume of the at least one el ectricalequipment.A subsea transformer system is additionally provide d. Thesubsea transformer system comprises a pressure comp ensator asindicated in connection with at least one of the ab ove-statedembodiments. Features of the pressure compensator a retherefore also disclosed for the subsea transformer systemand vice versa. In atleastone embodiment,the subsea transformer systemcomprises a main tank, a power transformer in the m ain tank,a pressure compensator and a rack. The rack carries the maintankand the pressure compensator. Forexample,the subsea transformersystem further comprisesa main compensator to compensate for volume changes of themain tank. Otherwise, this task may be fulfilled by thepressure compensator in which the electric componen t orcomponentsis / are located.The pressure compensator can also be a standalone d evice,separately retrievable for maintenance, for instanc e, or can P2024,0539 WO N2 / P240007WO02 May15,2025 -15 -be a fixed part of any other system, not necessaril yconnected to a larger subsea power transformer unit .A pressure compensator and a subsea transformer sys temdescribed herein are explained in greater detail be low by wayof exemplary embodiments with reference to the draw ings.Elements which are the same in the individual figur es areindicated with the same reference numerals. The rel ationshipsbetween the elements are not shown to scale, howeve r, butrather individual elements may be shown exaggerated ly largeto assistin understanding. In the figures:Figures 1 to 3 show schematic cross-sectional views ofexemplaryembodimentsofpressure compensators described herein,Figure 4 shows schematic perspective representation s of anexemplaryembodimentofa pressure compensator described herein,Figure 5 shows a schematic perspective cross-sectio nal viewofthe pressure compensatorofFigure 4, Figures6 and 7 show a schematicbottom view and a schematic top view,respectively,ofthe pressure compensatorofFigures4 and 5,Figure 8 shows schematic perspective representation s of anexemplaryembodimentofa pressure compensator described herein, P2024,0539 WO N2 / P240007WO02 May15,2025 -16 -Figure 9 shows a schematic perspective cross-sectio nal viewofthe pressure compensatorofFigure 8, Figures10 and 11 show a schematicbottom view and a schematictop view,respectively,ofthe pressure compensatorofFigures8 and 9,Figure 12 shows a schematic cross-sectional view of anexemplaryembodimentofa subsea transformer system comprising a pressure compensatordescribed herein. Figure 13 showsa schematicperspective view ofan exemplary embodimentofan electronicequipmentforpressure compensatorsdescribed herein,andFigure 14 shows a schematic side view of an exempla ryembodimentofa visualindicatorforpressure compensatorsdescribed herein.Figure 1 illustrates an exemplary embodiment of a p ressurecompensator 1. The pressure compensator 1 comprises a firstbellows chamber 21 and an electric equipment 3. For example,the electric equipment 3 is an auxiliary transforme rconfigured fora relativelylow electricpowerof, forexample, at most 50 kVA. The electric equipment 3 i scompletely arranged in the first bellows chamber 21 . Althoughonly one electric equipment 3 is shown, there can b e apluralityofelectricequipments3,also different kindsof electricequipments3.The first bellows chamber 21 is configured to be fi lled witha first insulation liquid 61, like transformer liqu id oil. P2024,0539 WO N2 / P240007WO02 May15,2025 -17 -The first bellows chamber 21 may be an elastic vess el thatcan adapt its enclosed volume to an exterior presse r due tobeing submerged in sea water8,forexample.Thus, aninterior pressure of the first bellows chamber 21 m ay be thesame or approximately the same as an exterior press ure nextto the first bellows chamber 21 and / or the pressurecompensator 1. The first bellows chamber 21 may thu s define asealed volume in which the firstinsulation liquid 61 is contained.Further, the pressure compensator 1 includes electr icalfeedthrough 4. The electrical feedthroughs 4 connec t theelectric equipment 3 with an exterior of the pressu recompensator 1, for example, with a wiring providing power forthe electric equipment 3 and providing electrical c ontactwith a component fed by the electric equipment 3, n ot shown.In Figure 2, another example of the pressure compen sator 1 isillustrated. In this example, the pressure compensa tor 1includesa second bellowschamber22.Forexample, the firstbellows chamber 21 is located within the second bel lowschamber22.Thatis,the second bellowschamber22 canprovide a second hull around the first bellows cham ber 21.Hence, there can be an intermediate volume 541 betw een thefirst bellows chamber 21 and the second bellows cha mber 22.Thus,an exteriorside wall26 and a bottom ofthe pressurecompensator 1 may be made of the second bellows cha mber 22,and an interiorside wall25 and a top maybe made ofthefirst bellows chamber 21 and the first carrier plat e 23,respectively. For example, the second bellows chamb er 22,that is, the intermediate volume 541 between the hu lls of thebellows chambers 21, 22, can be filled with a secon d P2024,0539 WO N2 / P240007WO02 May15,2025 -18 - insulation liquid 62.The second insulation liquid 62 can bea transformer liquid as well. Especially, the secon dinsulation liquid 62 and the first insulation liqui d 61 canbe the same substance.Other than shown, the second bellows chamber 22 may run allaround the first bellows chamber 21. As depicted in Figure 2,the first and second bellows chambers 21, 22 may sh are afirst carrier plate 23 as a common wall. For exampl e, thefirstcarrierplate 23 isa plane metalplate,for example,made of steel. It is possible, that the electric eq uipment 3is mounted on the first carrier plate 23 in a hangi ng manner.That is, the electric equipment 3 is applied on a b ottom sideof the first carrier plate 23. The electrical feedt hroughs 4may be mounted on a top side of the first carrier p late 23.For example, the electrical feedthroughs 4 are wet- mateconnectors complying with IEC subsea standard IEC 6 1886-2:Subsea equipment. Also the overall pressure compens ator 1 maycomplywith said standard.Such a second bellows chamber 22 and / or such electr icalfeedthroughs 4 can also be present in all other emb odiments.Otherwise, the same as to Figure 1 may also apply t o Figure2,and vice versa.According to Figure 3, the first carrier plate 23 f orms thebottom of the pressure compensator 1. Thus, the ele ctricequipment 3 rests on the top side of the first carr ier plate23.As in all other examples it is possible that the el ectricequipment 3 is distant from the side walls 25 of th e first P2024,0539 WO N2 / P240007WO02 May15,2025 -19 -bellows chamber 21 and that it is thus also distant from thesecond bellowschamber22.Optionally, the electrical feedthroughs 4 may run t hrough theside wall 25 of the first bellows chamber 21 and, i f present,also through the side walls 26 of the second bellow s chamber22. Otherwise,the same asto Figures1 and 2 mayalso applyto Figure 3,and vice versa. In Figures4 to 7,anotherexample ofthe pressurecompensator 1 is illustrated in various representat ions. Thepressure compensator 1 comprises both the first bel lowschamber 21 and the second bellows chamber 22, for e xample, ina concentricmanner.Both side walls25,26 maybe in the mannerofa corrugated sheet,forexample.Between the sidewalls 25, 26 and, thus, between the first bellows c hamber 21and the second bellows chamber 22 there is again th eintermediate volume 541.The interior side wall 25 can be made of steel whil e theexterior side wall 26 can be made of a material res istant tosaltwater,forexample,an elastomerlike rubber.In this example, the pressure compensator 1 further comprisesa support frame 5. The first carrier plate 23 may b e part ofthe support frame 5 or may be integrated in the sup port frame5. Moreover, there is a second carrier plate 24 opp osite thefirst carrier plate 23. The side walls 25, 26 run b etween thetwo planar carrier plates 23, 24. Thus, the carrier plates23, 24 laterally protrude from the second bellows c hamber 22allaround,forexample. P2024,0539 WO N2 / P240007WO02 May15,2025 -20 - The electricalequipment3 ismounted on the first carrierplate 23 in a hanging manner. To do so, the first c arrierplate 23 may comprise a panel 58 and a base 59. For example,the side walls 25, 26 are fixed at the base 59. Hen ce, thepanel 58 can be placed onto the first bellows chamb er 21 andatthe same time the electricalequipment3 can be putintothe first bellows chamber 21. For example, the pane l 58 iscoupled with the base 59 in a reversible manner, fo r example,using a sealand bolts,notshown. Asan option,there isone orthere isa plurality ofmaintenance accesses 55 in the base 59 or otherwise in thepanel58.Bymeansofthe maintenance accesses55, the firstinsulation liquid 61 may be filled into the first b ellowschamber 21, for example. Alternatively, the connect ionchamber7 can be compensated to the second bellows chamber 22.Moreover, the pressure compensator 1 comprises a co nnectionchamber 7. The connection chamber 7 encloses a term inationvolume 542. The connection chamber 7 may be made of steel andis in particular filled with a third insulation liq uid 63which can be the same substance as the first and se condinsulation liquids61,62,forexample,thatis,atransformer insulation liquid. However, the third i nsulationliquid 63 may also be a different liquid. In this c ase, forthe electrical feedthroughs 4 it is possible to use dry-mateconnectors as the connection chamber 7 provides a s econdhull.For example, adjacent to the termination volume 542 there isa first connector 41 configured as a low-voltage de vice, for P2024,0539 WO N2 / P240007WO02 May15,2025 -21 -example, for a low-voltage side of a transformer as theelectrical equipment 3, and there is a second conne ctor 42configured as a high-voltage device, for a high-vol tage sideofthe electricalequipment3,forexample.In the connection chamber7,there mayoptionallybe an intermediate wiringbetween connector parts at the panel 58 and connect or partsat a hull of the connection chamber 7, not shown, f orexample, between the different parts of the first a nd secondconnectors41,42. The hullofthe connection chamber7 maybe rigid, thatis, may notconfigured forcompensating volume changes oftheconnection chamber 7 due to pressure changes. Other wise, thehull of the connection chamber 7 may be at least pa rtly offlexible manner, for example, may be formed as an e lasticcorrugated sheet.Optionally, the pressure compensator 1 further comp rises asupplementarypressure compensator53.Bymeansof thesupplementary pressure compensator 53, changes of t heintermediate volume 541 and / or of the termination v olume 542due to temperature changes and / or external pressure changescan be compensated for. For example, by means of th esupplementary pressure compensator 53 volume change s of thetermination volume 542 are compensated for; for thi s purpose,the termination volume 542 can be connected with th esupplementary pressure compensator 53 by means of a pipe 271.Volume changes of the bellows 21, 22 and especially of theintermediate volume 541 may be compensated for by d eformationofthe elasticside walls25,26.Optionally, there is no supplementary pressure comp ensator53. In this case, the volumes 541, 542 may hydrauli cally be P2024,0539 WO N2 / P240007WO02 May15,2025 -22 -connected with each other by a connection means, li ke anotherpipe or an opening, not illustrated, and the interm ediatevolume 541 may thus serve as a pressure compensatio n volumeforthe termination volume 542. Asa furtheroption,the supportframe 5 comprises a pluralityofsupportrods51,forexample,fourof thesupport rods 51. The support rods 51 may fixedly be connectedwith he first carrier plate 23. However, the second carrierplate 24 can slide along the support rods 51 and is guided bythe supportrods51 so thatvolume compensation of the firstand second bellows chambers 21, 22 is enabled by gu idedmovement of the second carrier plate 24 along a dir ection ofmovement28.For example, the supplementary pressure compensator 53 ismounted at the connection chamber 7. Otherwise, the optionalsupplementary pressure compensator 53 can also be m ounted atthe support frame 5, especially if there is no conn ectionchamber 7 or if there is only a relatively small co nnectionchamber7.Optionally, the support rods 51 each comprise a ped estal 57.Itispossible thatthe pressure compensator1 can be mountedonto a rack 12 of a subsea transformer system 10, c omparealso Figure 12. Thus, the pedestals 57 may comprise fixingmeans like hinges and / or screw threads. Moreover, t hepedestals 57 may allow a length adjustment of the s upportrods 51 and, thus, horizonal alignment of the press urecompensator1,ifneeded.As a further option, there may be movement limitati ons 56 atthe support rods 51. By means of the movement limit ations 56, P2024,0539 WO N2 / P240007WO02 May15,2025 -23 -movement of the second carrier plate 24 along the d irection28 can be restricted so that damage to the second c arrierplate 24,the side walls25,26 and the electrical equipment3 due to excess movement can be prevented. The move mentlimitations56 maybe metallicorplasticparts.Figures 4 to 7 are drawn true to scale; the size an d lengthproportions in said Figures may thus apply individu ally or inany combination as shown, for example, with a toler ance of atmost a factor of three or of at most a factor of tw o or of atmost a factor of 1.2. The same may apply for Figure s 8 to 11.Otherwise, the same as to Figures 1 to 3 may also a pply toFigures4 to 7,and vice versa.Figures 8 to 11 describe another example of the pre ssurecompensator 1. Concerning the bellows chamber 21, 2 2, thecarrierplates23,24 and the supportframe 5,the same mayapply as to Figures 4 to 7. However, there is no co nnectionchamber7.Thus,the connectors4,41,42 directly emerge from the panel58 to the surrounding seawaterwhen thepressure compensator is submerged. Hence, the conne ctors 4,41,42 maybe wet-mate connectors.In Figures 4 to 7 and 8 to 11, respectively, the el ectricalequipment 3 is mounted in a hanging manner. However , it isalternatively also possible that the electrical equ ipment 3is mounted onto the first carrier plate 23 in a sea tingmanner, analogously to Figure 3. In this case, if p resent,the connection chamber 7 may be below the bellows c hambers21, 22. Optionally, the movably mounted second carr ier plate24 forms the top of the pressure compensator 1. Fur theroptionally, the second carrier plate 24 may be prov ided with P2024,0539 WO N2 / P240007WO02 May15,2025 -24 -the base 59 and the panel 58 instead of the first c arrierplate 23.If the electrical equipment 3 is mounted in a seati ng manner,it is also possible that the with the first carrie r plate 23being the electrical equipment 3 is just put onto t he secondcarrierplate 24 and using electricwiring between the first carrierplate 23 and the electricalfeedthroughs4 through the firstbellowschamber21 so thatonlyveryfew changesare required to the configuration as shown in Figur es 4 to 7and 8 to 11,respectively.Otherwise, the same as to Figures 1 to 7 may also a pply toFigures8 to 11,and vice versa.Concerning the first and second bellows chambers 21 , 22,reference isalso made to documentUS 2011 / 0203379 A1,the disclosure contentofwhich isherebyincorporated byreference, see especially Figure 1 and paragraphs 1 8 to 39 ofsaid document.In Figure 12, an example of a subsea transformer sy stem 10 isshown. The subsea transformer system 10 comprises a main tank13, a power transformer 11 in the main tank 13, the pressurecompensator 14 and the rack 12 carrying the main ta nk 13 andthe pressure compensator1.However, the pressure compensator 1 can also be a s tandalonedevice, separately retrievable for maintenance, for instance,or can be a fixed part of another system, not neces sarilyconnected to a largerpowertransformerunit. P2024,0539 WO N2 / P240007WO02 May15,2025 -25 -For example, the power transformer 11 is configured for anelectrical power of at least 0.1 MVA or of at least 0.5 MVAand / orofatmost5 MVA orofatmost2 MVA.Itis possible thatthe powertransformer11 isconfigured foran electricalpower that exceeds the electrical power the electri calequipment3 isconfigured forbyatleasta factor of10 orby at least a factor of 10 2 and / or by at most a factor of 10 4or by at most a factor of 10 3.It is possible that the main tank 13 and the pressu recompensator 1 are hydraulically separated component s despitebeing submerged in the seawater8.In otherwords, itispossible that no insulation liquid is exchanged bet ween themain tank 13 and the pressure compensator 1. In thi s case,for pressure compensation of the main tank 13 there can be amain compensator14 coupled to the main tank13 by meansofa pipe 27.Otherwise,itcould also be possible that thepressure compensator 1 serves as the main compensat or 14; inthis case, the main tank 13 and the pressure compen sator 1are hydraulically coupled, for example, by means of the pipe27 between them. These options are indicated in Fig ure 12with dashed lines. Otherwise,the same asto Figures1 to 11 mayalso applyto Figure 12,and vice versa.In Figure 13, an example of the electrical equipmen t 3 isillustrated. In this case, the electrical equipment 3 is atransformer configured for a relatively low electri c power.Thus, the electrical equipment 3 comprises windings 33 framedin a mechanical structure 32, for example, which co uldcomprise or could be made of soft iron, for example . Thewindings33 can be addressed bya wiring 31. P2024,0539 WO N2 / P240007WO02 May15,2025 -26 - Otherwise,the same asto Figures1 to 12 mayalso applyto Figure 13,and vice versa.Optionally, all embodiments of the pressure compens ator 1 mayinclude one or a plurality of visual indicators 52, compareFigure 14.Forexample,the visualindicator52 is composedof an indication part 522 which may be fixed, for e xample, atone of the support rods 51. A scale 521 can be fixe d on thesecond carrier plate 24 which is guided by the supp ort rods51. Otherwise, the scale 521 can be attached to therespective support rod 51 and the indication part 5 22 can becoupled to the second carrierplate 24.For checking the relative position of the second ca rrierplate 24 and, thus, the volume of the first bellows chamber21, in particular, a remote operate vehicle, ROV fo r short,carrying a camera can be used. Other than optical i ndicators52, electric and / or hydraulic indicators are possib le aswell. The componentsshown in the figuresfollow,unless indicatedotherwise, exemplarily in the specified sequence di rectly oneon top of the other. Components which are not in co ntact inthe figures are exemplarily spaced apart from one a nother. Iflines are drawn parallel to one another, the corres pondingsurfaces may be oriented in parallel with one anoth er.Likewise, unless indicated otherwise, the positions of thedrawn components relative to one another are correc tlyreproduced in the figures.The invention described here is not restricted by t hedescription on the basis of the exemplary embodimen ts. P2024,0539 WO N2 / P240007WO02 May15,2025 -27 -Rather, the invention encompasses any new feature a nd alsoany combination of features, which includes in part icular anycombination offeaturesin the patentclaims,even ifthisfeature or this combination itself is not explicitl yspecified in the patent claims or exemplary embodim ents.

[0002] P2024,0539 WO N2 / P240007WO02 May15,2025 -28 - ListofReference Signs 1 pressure compensator 21 firstbellowschamber 22 second bellowschamber 23 firstcarrierplate 24 second carrierplate 25 interiorside wall 26 exteriorside wall 27 pipe 271 pipe 28 direction ofmovement 3 electricalequipment 31 wiring 32 mechanicalstructure 33 winding 4 electricalfeedthrough 41 firstconnector 42 second connector 5 supportframe 51 supportrod 52 visualindicator 521 scale 522 indication part 53 supplementarypressure compensator 541 firstintermediate volume542 termination volume (second intermediate volume)55 maintenance access 56 movement limitation 57 pedestal 58 panel 59 base 61 firstinsulation liquid P2024,0539 WO N2 / P240007WO02 May15,2025 -29 - 62 second insulation liquid 63 third insulation liquid 7 connection chamber 8 seawater 10 subsea transformersystem 11 powertransformer 12 rack 13 main tank 14 main compensator

Claims

P2024,0539 WO N2 / P240007WO02 May15,2025 -30 - PatentClaims1. A pressure compensator (1) configured for subsea -usecomprising:- a first bellows chamber (21) configured to be fil led with afirstinsulation liquid (61),- an electrical equipment (3) placed in the first b ellowschamber(21),and- electrical feedthroughs (4) connecting the electr icalequipment (3) with an exterior of the pressure comp ensator(1),- a connection chamber (7) attached to the first be llowschamber(21),- a second bellows chamber (22) configured to be in directcontactwith seawater(8),and -a pipe connecting the connection chamber(7)and the secondbellows chamber (22) without presence of a suppleme ntarypressure compensator, wherein- at least one of the electrical feedthroughs (4) c omprises afirst connector (41) and a second connector (42) be ingconnected in the connection chamber(7),- the connection chamber (7) is configured to be ex posed toseawater(8),and- the first bellows chamber (21) is arranged in the secondbellowschamber(22).

2. The pressure compensator (1) according to the pr ecedingclaim,further comprising a first carrier plate (23) confi gured tobe horizontallyarranged in a fixed manner, wherein the electricalequipment(3)iscarried by the first carrierplate (23),P2024,0539 WO N2 / P240007WO02 May15,2025 -31 - wherein the firstcarrierplate (23)formspartof the first bellowschamber(21).

3. The pressure compensator (1) according to any on e of thepreceding claims,further comprising a second carrier plate (24) conf igured tobe horizontallyarranged in a movable manner,wherein the second carrier plate (24) forms part of the firstbellowschamber(21).

4. The pressure compensator (1) according to any on e of thepreceding claims,further comprising a support frame (5) carrying the firstbellowschamber(21),wherein part of the first bellows chamber (21) is m ountedmovablyatthe supportframe (5). 5.The pressure compensator(1)according to claim 3 and according to the preceding claim,wherein the support frame (5) comprises one or a pl urality ofsupportrods(51),wherein the second carrier plate (24) is movably mo unted atthe support rods (51) so that the support rods (51) areconfigured to guide the second carrier plate (24) w henmoving. 6.The pressure compensator(1)according to claim 2 and according to the preceding claim,wherein the electrical equipment (3) is arranged be tween thefirst carrier plate (23) and the second carrier pla te (24),wherein the pressure compensator(1)isconfigured to beplaced in an upright position so that the second ca rrierplate (24) is configured to be below the first carr ier plateP2024,0539 WO N2 / P240007WO02 May15,2025 -32 - (23),seen along a direction ofgravity,wherein the first carrier plate (23) and the second carrierplate (24)are congruent,seen in top view,wherein the second carrier plate (24) is configured to bebelow the firstcarrierplate (23). 7.The pressure compensator(1)according to claim 6,wherein the electrical equipment (3) is arranged be tween thefirst carrier plate (23) and the second carrier pla te (24),wherein the second carrier plate (24) is configured to beabove the firstcarrierplate (23),seen along the direction ofgravity,wherein the support rods (51) are configured to gui de thesecond carrier plate (24) along the direction of gr avity.

8. The pressure compensator (1) according to the pr ecedingclaim,wherein the support rods (51) each comprise a pedes tal (57),wherein each of the pedestals (57) comprises a fixi ng means,and wherein the pedestals(57)are configured to allow foralength adjustment of the support rods (51) and hori zonalalignmentofthe pressure compensator(1).

9. The pressure compensator (1) according to any on e of thepreceding claims,wherein at least one of the electrical feedthroughs (4)emerges from the first bellows chamber (21) where t he firstbellowschamber(21)isexposed to seawater(8).

10. The pressure compensator (1) according to any o ne of thepreceding claims,further comprising a visual indicator (52) configur ed toP2024,0539 WO N2 / P240007WO02 May15,2025 -33 - visualize a compression state ofthe firstbellows chamber(21) to the exterior of the pressure compensator (1 ),wherein the visual indicator (52) comprises a scale (521) andan indication part (522) movable relative to one an other.

11. The pressure compensator (1) according to any o ne of thepreceding claims,wherein the electrical equipment (3) comprises at l east oneof a transformer, a circuit breaker, an inductor, acapacitor,ora resistor, wherein the electricalequipment(3)isconfigured for handling an electricalpowerofup to 50 kVA.

12. The pressure compensator (1) according to any o ne of thepreceding claims,wherein there is an intermediate volume (541) betwe en thefirst bellows chamber (21) and the second bellows c hamber(22) and the connection chamber (7) encloses a term inationvolume (542),wherein the intermediate volume (541) and the termi nationvolume (542)are hydraulicallyconnected with each otherbyaanother pipe or an opening, so that the intermediat e volume(541) is configured to serve as a pressure compensa tionvolume forthe termination volume (542).

13. The pressure compensator (1) according to any o ne of thepreceding claims,wherein the connection chamber (7) is filled with a thirdinsulation liquid (63)which isthe same substance asthe firstinsulation liquid (61,62).

14. The pressure compensator (1) according to any o ne of thepreceding claims,P2024,0539 WO N2 / P240007WO02 May15,2025 -34 -wherein the electrical feedthroughs (4) are wet-mat econnectors.

15. A subsea transformer system (10) comprising a m ain tank(13), a power transformer (11) in the main tank (13 ), apressure compensator (1) according to any one of th epreceding claims, a main compensator (14) configure d tocompensate for volume changes of the main tank (13) , and arack(12),wherein the rack (12) carries the main tank (13), t he maincompensator(14)and the pressure compensator(1).

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