Bushing and electrical apparatus

Abstract

A bushing (100) for a liquid-insulated electrical apparatus (200) is disclosed. The bushing (100) comprises an electrical conductor (101) and an insulator body (110) through which the electrical conductor (101) extends, wherein the insulator body (110) comprises a main part (112) and a plurality of projecting ribs (130), wherein the main part (112) comprises a hollow cylinder shape (113) and wherein the projecting ribs (130) each project radially inwards from the main p art (112) and wherein the projecting ribs (130) comprise a each a main extension (131) along a longitudinal axis (102) of the conductor (101) and a free end (135) facing the electrical conductor (101).

Description

[0001] P2024,0078 WO N / P230197WO01 February26,2025 -1 - Description Bushing and electricalapparatusThe present disclosure relates to a bushing and a l iquidinsulated electrical apparatus comprising the bushi ng. Theelectrical apparatus may be a transformer or a swit chgear,forexample.A bushing for example enables a conductor to pass t hrough awall of an electrical apparatus, providing electric alinsulation between the conductorand the wall. US 2010 / 284133 A1 relatesto a method ofproducing an electricpowerdevice including a tubularshellof anelectrically insulating polymer in which there is p rovided ascreen of an electrically conducting material, wher ein thescreen is placed in a mould, the mould is filled wi th aresin, and the resin is permitted to solidify in th e mould.The screen is positioned in the mould such that a p eripheralsurface thereof is in supporting contact with a par t of themould. WO 2007 / 065912 A1 relatesto a bushing forenergydistribution and transmission has an insulating bod y in whicha high-voltage contact bolt is at least partially e mbedded,and having a flange, which is connected to the insu latingbody, for fixing the bushing in a through-opening o f acontainerwallatground potential.The insulating bodyhasan inner wall region, which, owing to the injection -molding,bearsflatagainstthe high-voltage contactbolts, and anouter wall region, which is connected to the flange and isconnected to the inner wall region via a connecting section. P2024,0078 WO N / P230197WO01 February26,2025 -2 -US 2179356 A relates to a bushing with an outside insulatorbeing disposed substantially concentric with a cent ralinsulator.SE 506172 C2 relates to an insulator. The insulato r consistsof a tube which is made from a thermoplastic weldab lematerial. A number of pre-fabricated bushings are a ppliedabout the tube. The bushings are made from a rubbe r-likematerial,such ase.g.silicone rubber. Itisdesirable to provide a bushing thatprovides a reliable operation. Embodimentsofthe disclosure relate to a bushing. In particular,the bushing isconfigured fora liquid insulated electricalapparatus. The bushing comprisesan electricalconductor.The bushingcomprises an insulator body. The electrical conduct or extendsthrough the insulator body. The insulator body comp rises amain part. The main part can be also referred to as insulatorcore. The insulator body comprises a plurality of p rojectingribs. The main part comprises a hollow cylinder sha pe. Theconductorextendsthrough thishollow cylinder.Inparticular, the main part comprises one single holl owcylinder, from with the projecting ribs project inw ards. Theprojecting ribseach projectradiallyinwardsfrom the mainpart. The projecting ribs are internal ribs. The pr ojectingribs comprise a main extension along a longitudinal axis ofthe conductor. The projecting ribs each have a free endfacing away from the main part. The inwardly projec ting endofthe projecting ribsisfree and,in particular, isnot covered byanotherhollow cylinder.The electrical conductorand the free ends of the projecting ribs are direct ly P2024,0078 WO N / P230197WO01 February26,2025 -3 - opposite each other,in particularwithoutanother partofthe insulating body between them. The free ends are directlyfacing the electrical conductor. The free ends allo winsulating liquid to circulate between the conducto r and theprojecting ribs, in particular between the free end s and theconductor, in particular also between the ribs them selves.This allows for a cost-effective manufacturing of t heinsulatorbodyand the bushing.For example, the insulator body is arranged at a di stancefrom the electricalconductorand isnotin direct contact with the electricalconductor.For example, the main body is arranged at least for the mostpart at a distance from the electrical conductor an d is notin direct contact with the electrical conductor. Fo r example,a proportion of10% orlessofthe main bodyisin directcontact with the electrical conductor along the lon gitudinalaxis.Forexample,a portion of90% ormore ofthe main body isspaced from the electricalconductoralong thelongitudinal axis. In particular, the free ends are arrangedata distance from the conductor,atleastmostof the freeends, in particular at least 90% of the free ends i s arrangedata distance from the conductor.For example, the projecting ribs are spaced apart f rom theelectrical conductor. The free ends of the projecti ng ribsare each arranged spaced apartfrom the electrical conductor.A free space is between the electrical conductor an d the freeends.The free space isconfigured such thatin anoperational condition oil or another liquid can cir culatebetween the electricalconductorand the insulator body,inparticular between the projecting ribs and the elec tricalconductor. For example, during use, the oil is in d irectcontact with the electrical conductor and the proje cting P2024,0078 WO N / P230197WO01 February26,2025 -4 -ribs. The oil is used for cooling, for example. The freespace enables a sufficiently good circulation of th e oilbetween the electricalconductorand the insulator bodyand thusenablesan improved heatexchange. The projecting ribsare configured to mechanically supportthe main part of the insulator body. The projecting ribs areconfigured to transfer forces along the longitudina l axis.Thereby the main part is reinforced. The projecting ribsallow, for example, a thin wall structure of the ma in part.The insulator body can be formed with a reduced mat erialusage. The thin wall structure of the thermoplastic materialmakes the time needed for heat transfer through the wallthickness short, in particular the time needed to c ool downthe molten thermoplastic material until it solidifi es in themold.The thin-walled main part with the reinforcing inte rnalprojecting ribs realize a reduced external circumfe rence ofinsulator body. This increases the electric resista nce of thesurface of the insulator body and decreases the sur faceleakage currents in operation, for example. The out er side ismore resistant against dust and particles contamina tion thana design with outer ribs. Such contamination on the outerside would lead to a local reduction of an electricresistance of the surface of the insulator, thus in creasingthe leakage current and potentially causing surfacedischarges or a flashover. This is avoided by the i nternalreinforcement ribs. For example, with the outer sid e withoutreinforcementstructuresitiseasierto clean the outer side. P2024,0078 WO N / P230197WO01 February26,2025 -5 - Forexample,the insulatorbody,in particularthe main partand the projecting ribs, are made out of a thermopl asticmaterial. In particular, the insulator body, in par ticularthe main part,and the projecting ribs,comprise a thermoplasticmaterial.Forexample,the main part and theprojecting ribs consist of a thermoplastic material . Thethermoplastic material is an electrically insulatin gmaterial. In particular, the thermoplastic material comprisesa high elastic modulus and mechanical strength, eve n atelevated temperatures,and isresistantto thermaldegradation. It is also resistant to chemical degra dation, inparticular by electric insulation liquids, for exam ple bytransformeroiland naturalorsyntheticesters.For example, the thermoplastic material is at least one ofpolyether ether ketone (PEEK), polyphenylene sulfid e (PPS),polyphthalamide (PPA), polyethersulfone (PES), poly etherimide(PEI), polyamide (PA), and semi-aromatic polyamide. Forexample, the main part and / or the projecting ribs c omprise aglassfiberreinforcement.Thus,the thermoplastic materialis reinforced by the glass fiber filler. For exampl e, thethermoplastic material is one of the listed polymer icmaterials filled with glass fibers. In particular, ceramicmaterials can be omitted. The projecting ribs provi desufficient stability such that thermoplastic materi al can beused instead ofceramicmaterial.The projecting ribs extend longitudinally elongated along thelongitudinal axis. The projecting ribs extend along theconductor.In particular,the projecting ribsface the conductorwithoutbeing in directcontactwith the conductor.The projecting ribs radially extend between an inne r side ofthe main part and the conductor. Each of the projec ting ribs P2024,0078 WO N / P230197WO01 February26,2025 -6 -is longer along the longitudinal axis than along th e twootherspatialdirectionsrunning transverse to it. Forexample, each projecting rib comprises a rib thickn esstransverse to the direction of projection. Each pro jectingrib extends longer along the longitudinal axis than along thedirection of projection and longer than the rib thi ckness.The rib thickness and an extension along the direct ion ofprojection isshorterthan the extension along thelongitudinal axis. This elongated extension along t helongitudinal axis enables a reliable reinforcement.The bushing realizes a mechanically robust insulato r bodyusing less material, which can be manufactured in a shortertime. The main part comprises the projecting ribs w hich forexample keep the conductor centred and reinforce th einsulator body against compression forces and trans ferscompression forces to an outer side of the main par t, forexample to a flange.According to an embodiment, the main part is formed in onepiece. Alternatively, the main part comprises two o r moreseparate parts.The two ormore separate partsare forexample stacked along the longitudinal axis. By pro viding themain part in one single piece, manufacturing and mo unting ofthe bushing can be quick and easy. Providing the ma in partwith two or more separate parts for example enables a greaterfreedom of design. Different functionalities can be realizedin different parts of the two or more separate part s.According to an embodiment, the bushing comprises a conductorseal. The conductor seal is arranged axially betwee n an upperpart and a lower part of the two or more parts. The upperpart is fixed to the electrical conductor such that the upper P2024,0078 WO N / P230197WO01 February26,2025 -7 -part exerts a force on the conductor seal towards t he lowerpart. The upper part is formed inclined downward to overlapthe lowerpartatleastin part.The innersurface ofthe conductorsealmatchesthe conductorand the outer surface matchesthe insulatorbody.The upper part is used to provide a seal compressin g forcealong the longitudinalaxis.The conductorsealis fixedbetween the lower part and the upper part by the fo rceexerted between the upperpartand the lowerpart. Forexample, the lower part is supported on a wall of t heelectrical apparatus. The upper part is fixed to th eelectrical conductor such that the lower part and t he upperpart with the conductor seal in between are pressed againsteach other. According to embodiments,the two ormore separate partsofthe main part are made of thermoplastic. For exampl e, all ofthe separate parts are made of thermoplastic, or ju st some ofthe separate parts are made of thermoplastic. In pa rticular,the upperpartismade ofthermoplastic.According to an embodiment, the main part is an inj ectionmolded body.Forexample,the two ormore separate partseachare injection molded bodies. Injection molding real izes asimple, cost-effective and material-saving producti on of themain part.According to an embodiment, the bushing comprises a weathershed. The weather shed is, for example, an integral part ofthe main part. The weather shed, for example, incre ases thecreepage length of the bushing. This ensures adequa teelectricalinsulation even with a moisture covered surface, P2024,0078 WO N / P230197WO01 February26,2025 -8 -for example. Due to the design of the main part whi ch, forexample, is made of thermoplastic, the weather shed can beeasilyintegrated into the main part.Forexample, theweather shed projects radially in the opposite dire ction tothe projecting ribs.Itispossible thatmore than oneweather shed is provided as an integral part of the mainbody.According to an embodiment, the bushing comprises a n outercover. The cover covers an outward facing portion o f the mainpart. A majority, for example more than 75%, more t han 80%,more than 90% or more than 95% of the outer surface of themain part exposed to air and / or arranged outside th eapparatusiscovered bythe cover.Anotherpartof thesurface of the main part which is exposed to the in sulatingliquid inside the apparatusisalso notcovered by the cover.For example, the outer cover is made of an elastome ricmaterial. The outer cover is fixed to the main part . Theouter cover adheres firmly to the main part. The ou ter covercovers the main part at least partly. The outer cov er housesthe main part at least partly. The cover can also b e referredto as housing or insulating housing. For example, t heelastomeric material is silicone rubber or comprise s siliconerubber. For example, the outer cover provides a hyd rophobicsurface.The outersurface ofthe outercoverdoes noteasilycollect contamination and is effectively cleaned by rainwaterduring operation or in a cleaning procedure provide d whenservicing the bushing.According to an embodiment, the bushing comprises a weathershed which isan integralpartofthe outercover. For example,the weathershed iscompletelyformed out ofthe P2024,0078 WO N / P230197WO01 February26,2025 -9 - elastomericmaterial.Itisalso possible thatthe weathershed comprises a protrusion of the main part, which iscovered by the outer cover, such that the weather s hed isformed by the main part and the outer cover togethe r.According to an embodiment, the outer cover compris es achemical coupling agent in the elastomeric material to form achemicalbond between the outercoverand the main part.Forexample, the outer cover is made of a so-called sel f-adhesivesilicone rubber, in particular a so-called cured li quidsilicone rubber containing chemical coupling agents able toform chemical bond between the surface of the therm oplasticmaterial of the main body and the crosslinked silic one rubbermaterial. In this case, no addition primer or other auxiliarymaterials are necessary to form the chemical bond b etween theouter cover and the main part. The chemical couplin g agent aspart of the elastomeric material forms the chemical bond tothe main part, in particular to the thermoplastic m aterial ofthe main part.Thus,itissufficientto applytheelastomeric material including the chemical couplin g agent ina liquid state on the main part.The chemicalbond isformed during curing ofthe elastomericmaterial.The combination of the use of the thermoplastic for the mainpart, the elastomeric material for the cover and th e chemicalbond to fix the main part and the cover to each oth er, forexample makesthe manufacturing processeasierand faster.Inparticular, the thermoplastic has desired and prese t surfacepropertiesdirectlyafterthe molding process.Self-adhesive elastomeric material in particular is suitablefor low voltage usage. Faster manufacturing and low costs arerealized to create a bond between the elastomeric m aterial P2024,0078 WO N / P230197WO01 February26,2025 -10 - and the thermoplastic.Forexample,the bond might notbe asstrong as with the use of a separate primer but str ong enoughfor the requirements and needs by a low voltage usa ge. Inparticular, the use of thermoplastic for the main p art allowsthe use of self-adhesive elastomeric material, beca use thesetwo materials bond together even without a separate primer.According to an embodiment, a primer layer is provi dedbetween the main part and the outer cover. The prim er layerforms a chemical bond to the main part and a furthe r chemicalbond to the outer cover. The primer layer enables t he use ofan elastomeric material without a chemical coupling agent.The primer layer is formed on the main part and for ms achemical bond to the main part. The elastomeric mat erial ofthe outercoverisapplied on the primerlayerand the furtherchemicalbond between the primerlayerand the outercover is formed. Thus, the primer layer enables a f ixing ofthe outer cover and the main part together by chemi cal bonds.According to an embodiment, the main part comprises an outerflange. The outer flange projects radially outwards from themain part.The outerflange isan integralpartof the main part.The flange providesa mounting interface for thebushing to the electrical apparatus. For example, t he bushingis fixed to the electrical apparatus at the outer f lange.According to an embodiment, the outer flange is con figured tohold a gasket. This ensures that the gasket is reli ably heldin place.The bushing and the electricalapparatus are reliablysealed againstfluids. P2024,0078 WO N / P230197WO01 February26,2025 -11 -According to an embodiment, a plurality of flange r ibs isarranged between the outer flange and the main part . Theflange ribs project radially outwards from the main part. Theflange ribsreinforce the flange and therebylimit a flange detection.The position ofthe flange ribsbetween the mainpart and the outer flange enables the surface resis tance ofthe insulator body to be increased because the leng th of theouter circumference of the main part can be reduced .According to an embodiment,atleasta partofthe flangeribs is configured to hold the gasket. Thus, the ga sket isreliably held in place, even during transport befor e beingmounted on the electricalapparatus.According to an embodiment, the outer flange compri ses anopening. An elongated mounting element can protrude throughthe opening to fixthe main partto the electrical apparatus.Thus, no additional clamps are necessary to mount t he bushingon the electrical apparatus. For example, a threade d studwelded to the wallofthe electricalapparatusand extending through the opening and a nutthreaded on the stud holdsthe flange in place.According to an embodiment, the main part extends a xiallybelow the outer flange. This improves insulation an d forcescan be reliablydissipated to the outerflange.Inparticular, the projecting ribs extend axially belo w theouter flange. Thus, reinforcement is provided in th e area ofthe outerflange where the bushing issupported on the wall ofthe electricalapparatus.Forces,in particular cantileverforces, can be reliably absorbed and distributed by theprojecting ribs. Deformation of the main part in th e area ofthe flange due to the forcescan be avoided. P2024,0078 WO N / P230197WO01 February26,2025 -12 -According to an embodiment, the insulator body comp risesthree projecting ribs or more. In particular, the i nsulatorcomprises more than five projecting ribs, more than sevenprojecting ribs,more than nine projecting ribsor more than11 projecting ribs. In particular, the number of pr ojectingribs depends on the diameter of the bushing. For ex ample, thenumber of ribs is not less than 3, in particular si x ribs ormore and 12 ribs or less. According to examples, th einsulatorbodycomprisesmore than 12 ribs.According to an embodiment, the projecting ribs eac h comprisethe rib thickness transverse to the device of proje ction witha value of 0.5 mm or more and 10 mm or less. For ex ample, therib thickness is between 25% and 100% of the wall t hickness.In particular, the rib thickness is the same size o r smallerthan the wall thickness. Thus, reliable reinforceme nt andmaterial-saving manufacturing are possible. Accordi ng toexamples, the ribs 130 are tapered towards the cond uctor, inparticular to simplify removal from the mold duringmanufacturing.Further embodiments of the disclosure relate to a l iquidinsulated electrical apparatus. The liquid insulate delectrical apparatus comprises the bushing accordin g to oneof the embodiments described herein or according to anycombination of the described embodiments. The liqui dinsulated electricalapparatuscomprisesa wallin which thebushing is installed. The bushing enables the condu ctor topass through the wall and provides an electrical in sulationbetween the conductorand the wall. P2024,0078 WO N / P230197WO01 February26,2025 -13 -The electrical apparatus may be a low voltage appar atus, amedium voltage apparatus and / or a high voltage appa ratus. Asan example, the electrical apparatus is a transform er oranotherelectricalapparatus. The electricalapparatuscomprisesa tankin which one ormore electrical functional elements are located. Fo r example,a winding, such as a transformer winding, may be lo cated inthe tank. The tank is filled by an insulating liqui d.According to an embodiment, the projecting ribs ext endaxially across the wall. The projecting ribs extend s from anoutside of the tank to an inside of the tank of theelectrical apparatus. The projecting ribs extend tr ansverseto the wall.Thisenablesa reliable reinforcement oftheinsulator body along the entire extension of the in sulatorbody.Hereinafter, the bushing and the electrical apparat us will beexplained in more detail with reference to the draw ings onthe basis of exemplary embodiments. The accompanyin g figuresare included to provide a further understanding. In thefigures, elements of the same structure and / or func tionalitymay be referred bythe same reference signs.Itis to beunderstood that the embodiments shown in the figure s areillustrative representations and are not necessaril y drawn toscale. Insofar as elements or components correspond to oneanother in terms of their function in different fig ures, thedescription thereof is not necessarily repeated for each ofthe following figures.Figures 1 to 10 schematically show different exampl es of abushing and an electricalapparatus. P2024,0078 WO N / P230197WO01 February26,2025 -14 -The embodiments of Figures 1 to 5 and 9 in particul ar areapplicable for low voltage bushings 100. The embodi ments ofFigures6 to 8 and 10 in particularare applicable formediumvoltage bushings 100. Ratings may cover AC or DC vo ltages.For example, a range from 0.1kV to 72.5kV, in parti cular from1kV to 3.6kV, is referred to as low voltage. For ex ample, arange from 3kV to 72.5kV is referred to as medium v oltage(MV), in particular lager than 3.6 kV. For example, currentrating isfrom 100 A to 10000 A.Figures 1, 3, 4 and 5 each show a horizontal sectio n on theleft-hand side along line A-A of the right-hand sid e, whichshowspartofa verticalsection.Figure 1 schematically shows an embodiment of the b ushing 100installed in a wall201 ofan electricalapparatus 200.Theelectrical apparatus 200, for example is a liquid i nsulatedelectrical apparatus like a transformer or a reacto r. Aninsulating liquid 103 is arranged in a tank which i s boundedby the wall 201. For example, the insulating liquid 103 is anoil195.The bushing 100 provides an electrical connection o f theelectricalapparatus200 through the wall201 from an outsideto an inside. The wall 201 may be on earth potentia l or atleast on an electrical potential that is potentiall ydifferentfrom the potentialofa conductor101 of thebushing 100. An insulator body 110 of the bushing 1 00providesan electricalinsulation between the wall 201 andthe electrical conductor 101. In particular, the bu shing 100comprisesa rotationallysymmetricaland / ormirror- symmetricalshape. P2024,0078 WO N / P230197WO01 February26,2025 -15 -The insulator body 110 surrounds the electrical con ductor101. The electrical conductor 101 extends through t heinsulator body 110 along a longitudinal axis 102. T heelectrical conductor 101 extends elongated along th elongitudinal axis 102. A part of the insulator body 110 isexposed to the airenvironment,typicallyoutdoorenvironment, and another part of the insulator body 110 isimmersed in the insulating liquid 103 of the appara tus 200.The insulator body 110 comprises a main part 112. T he mainpart112 comprisesa hollow cylindershape 113,at leastin a part.The main part112 iscoaxiallyarranged with the electricalconductor101.Forexample,a centerof the hollow cylindershape 113 isthe longitudinalaxis102. The insulatorbody110 comprisesan innerside 114 which facesthe electricalconductor101.The innerside 114 extendsalong the longitudinalaxis102.The insulator body comprises a plurality of project ing ribs130. The projecting ribs 130 are arranged on the in ner side114 of the main part 112. In particular, the main p art 112and the projecting ribs130 are formed asa single piece.Theprojecting ribs 130 project each from the inner sid e 114 to afree end 135. The free end 135 is arranged at a dis tance tothe electrical conductor 101, such that a free spac e 190 isprovided between the insulator body 110 and the ele ctricalconductor 101. The free end 135, which faces the el ectricalconductor 101, is arranged spaced apart from the el ectricalconductor 101. In particular, the free space 190 is providedbetween the free ends 135 of the projecting ribs 13 0 and theelectrical conductor 101. The oil 195 or another li quid 103 P2024,0078 WO N / P230197WO01 February26,2025 -16 -which is provided inside the electrical apparatus 2 00 forcooling and / or insulation can circulate between the insulatorbody 110 and the electrical conductor 101 in the fr ee space190, in particular between the free ends 135 of theprojecting ribs 130 and the electrical conductor 10 1. Thefree space 190 allows good heat exchange between th econductor 101 and the oil 195 as the oil 195 can ci rculatearound the electrical conductor 101 in the free spa ce 190.The projecting ribs 130 each comprise a main extens ion 131which extends in a direction along the longitudinal axis 102.The projecting ribs130 extend elongated along the longitudinalaxis102.The projecting ribs 130 each project radially towar ds theconductor 101 from the inner side 114. The projecti ng ribs130 are radially arranged around the electrical con ductor101. The projecting ribs 130 radially extend from t he innerside 114 towards the conductor 101, for example wit houtdirectlytouching the conductor101.The projecting ribs 130 reinforce the insulator bod y 110. Asshown in Figure 2, different forces like a cantilev er force104, a compression force 105 and a further compress ion force106 act on the bushing 100 and the insulator body 1 10. Theprojecting ribs 130 strengthen the insulator body 1 10 againstdeformation due to the forces 104, 105, 106. The de sign ofthe insulator body 110 with the projecting ribs 130 allows athin wallstructure ofthe insulatorbody110 with a reducedwall thickness 124. For example, the wall thickness 124comprises a value of 10 mm or less, for example 6 m m or less.In particular, the insulator body 110 comprises one singlehollow cylindrical sleeve 113 and the projecting ri bs 130. P2024,0078 WO N / P230197WO01 February26,2025 -17 -For example, the insulator body 110 comprises no ad ditionalsecond sleeve, which is coaxially arranged to the s leeve 113.The projecting ribs 130 are arranged between the el ectricalconductor 101 and the hollow cylindrical sleeve 113 .The insulator body 110 is made of thermoplastic mat erial 115.The insulator body 110 with the hollow cylinder sha pe 113 andthe projecting ribs 130 for example is manufactured by asingle injection molding process.The insulator body 110 comprises a flange 118 which radiallyprojects outwards from outer side 129 of the main p art 112.The outer side 129 is arranged radially opposite th e innerside 114. The flange 118 is configured to provide a mountingofthe bushing 100 to the wall201.Forexample,a gasket160is arranged between the flange 118 and the wall 201 toprovide a fluid-tightconnection. The projecting ribs130 are arranged in an area of the flange 118.The projecting ribs130 extend longitudinally overthe flange 118.Thisallowsa reliable transferofthe verticalcompression force 105 along the main part 112 towar ds theflange 118. The extension of the projecting ribs 13 0 acrossthe flange 118 reinforce the flange attachment to t he mainpart 112 and limits a deflection of the flange 118. Theflange 118 is connected to the main part 112 at a c onnection119. The projecting ribs 130 extend over the connec tion 119on the innerside 114.In the embodiments of Figures 1 to 5, the main part 112comprises an upper part 121 and a lower part 122. T he lowerpart 122 comprises the hollow cylinder shape 113 an d theprojecting ribs130 aswellasthe flange 118. P2024,0078 WO N / P230197WO01 February26,2025 -18 -The upper part 121 is arranged on an end of the low er part122 facing away from the wall 201 along the longitu dinal axis102. The upperpart121 isinclined with respectto thelongitudinal axis 102 and overlaps the lower part 1 22 inpart. Thus, the upper part forms a weather shed and extendsthe creepage path along the outerside 129.The upper part 121 is fixed to the conductor 101 by a holder126. During manufacturing, the lower part 122 is ar ranged onthe wall 201. A conductor seal 140 is arranged on t heconductor 101 and pressed vertically along the long itudinalaxis102 againsta sealseat125 ofthe lowerpart 122 bytheupper part 121. This compression force 105 is maint ained byfixing the upper part 121 with the holder 126 at th econductor101.A gap 109 is arranged axially between the upper par t 121 andthe lower part 122. The transition between the uppe r part 121and the lowerpart122 issealed via the conductor seal140.Inside the tank, the conductor 101 is supported via aninsulating support 107 at the wall 201. The main pa rt 112extends elongated over the wall 201 towards the sup port 107along the longitudinal axis 102. For example, the p rojectingribs 130 extend over the wall 201 along the longitu dinal axis102. Thereby, the main part 112 is reinforced by th eprojecting ribs 130 also inside the tank of the ele ctricalapparatus 200. This allows a better resistance agai nst thecantilever force 104. An end 127 of the main part 1 12 facingawayfrom the sealseat125 along the longitudinal axis102 P2024,0078 WO N / P230197WO01 February26,2025 -19 -protrudes over the projecting ribs 130 along the lo ngitudinalaxis 102. The length of this protrusion is large en ough toprevent an electric flashover to happen in the insu latingliquid 103 between the tank wall 201 and the conduc tor 101 ofthe bushing 100.The flange ribs 130 enable a robust mechanical stru ctureagainst flange deflection of the flange 118 under t hecantilever force 104 and the compression forces 105 , 106. Thearrangement of the projecting ribs 130 on the inner side 114of the main part 112 makes the outer side 129 smoot her.Therebya contamination collection isreduced.Figure 3 shows an embodiment of the bushing 100 whi chcorresponds to the embodiment of Figure 1. Addition ally,flange ribs 170 are provided. The flange ribs 170 a rearranged at the flange 118 to support the flange 11 8 againsta bending and / or deformation. The flange ribs 170 a reradially arranged between the outer side 129 and th e flange118 on a side of the flange 118 facing the wall 201 . As shownin Figure 5, the flange ribs 170 can be elongated a long thelongitudinal axis 102 to provide a support and fixa tion forthe gasket 160. For example, at least some of the f lange ribs170 are elongated to hold the gasket 160 in an unmo untedstate, such that a detachment of the gasket 160 fro m theflange 118 can be avoided.The projecting ribs 130 and the flange ribs 117 are shownradially aligned. It is also possible to provide an offsetarrangement of the flange ribs 170 and the projecti ng ribs130. P2024,0078 WO N / P230197WO01 February26,2025 -20 -The flange ribs 170 provide a robust mechanical str uctureagainst flange deflection under cantilever forces 1 04, andunder compression forces 105, 106. The placement of theflange ribs 170 on the side of the flange 118 facin g the wall201 contributes to a smooth outer area of the flang e 118,which helpsto avoid contamination.Figure 4, which may be helpful to better understand theinvention, shows an example of the bushing 100. Acc ording tothe embodimentofFigure 4,the insulatorbody110additionally comprises an inner part 117. According to theembodiment of Figure 4, the projecting ribs 130 hav e no freeends 135 and do not directly face the electrical co nductor101 due to the inner part 117. The inner part 117 c omprises ahollow cylinder shape and is coaxially arranged wit h the mainpart 112. The inner part 117 provides additional ri gidity, inparticular against the compression 105, 106. Furthe r, theinner part 117 may constitute an additional barrier forelectric insulation between the conductor 101 and t he wall201. The projecting ribs 130 radially extend betwee n the mainpart112 and the innerpart117.The embodiment of Figure 4 shows the inner part 117 and theflange rib 170.According to a furtherembodiment, the innerpart 117 is provided and the flange rib 170 is omit ted.Figure 5 showsan embodimentwith elongated flange ribs170which serve as holders for the gasket 160, as alrea dymentioned above. In the shown embodiment, four of t he flangeribs 170 are elongated to hold the gasket 160. Of c ourse,this number is just an exemplary number. It is poss ible tohave lesselongated flange ribs170 asholdersfor the gasket160 or more than four elongated flanges 170. The el ongated P2024,0078 WO N / P230197WO01 February26,2025 -21 -flange ribs 170 keep the gasket 160 in place and ce ntredduring installation on the wall 201 and also duringoperation. Figures6 to 8 show embodimentsofthe bushing 100 with themain part realized in one single piece. The upper p art 121,as for example shown in Figures 1 to 5, is replaced by a hood128. The hood 128 is, for example, not made of ther moplasticmaterial. The hood 128 for example comprises an ele ctricallyconductive material, for example metal. The conduct or seal140 is pressed between the hood 128 and the seal se at 125 ofthe main part 112. The hood 128 is fixed to the con ductor101.The embodiments of Figures 6 to 8 in particular areapplicable for medium voltage bushings 100. A longe r creepagepath is realized by the shape of the insulator body 110.The main part112 comprisesweathersheds116.The weathersheds extend the creepage path. For example, the we athersheds116 are formed asintegralpartsofthe main part112.The main part 112, with the projecting ribs 130 and theweathersheds116,isformed asone single piece.Figures 6 to 8 exemplarily show two weather sheds 1 16. It isalso possible to provide just one single weather sh ed 116 ormore than two weathersheds116,forexample three ormore. The weathersheds116 radiallyprojectoutwardson the outer side 129 ofthe main body112.The projecting ribs 130 andthe weather sheds 116 are arranged radially opposit e eachother. P2024,0078 WO N / P230197WO01 February26,2025 -22 - The insulatorbody110 isfixed to the wall201 by a flange clamp 111.The flange clamp 111 isa separate part which isfixed to the wall 201, for example by a screw conne ction andexertsa force on the flange 118.According to embodiments, de-airing is incorporated in theconductor 101 to degas the inner volume of the bush ing 100when installed on the apparatus 200 and filled withinsulating liquid 103. Alternatively, an additional metallicintermediate ring is arranged between the main part 112 andthe hood 128.The conductorseal140 iscompressed betweenthis ring and the hood 128. De-airing is provided i n the ringin thisembodiment.The electrical conductor 101 extends only partly al ong themain part 112. An electrically conductive conductor extension108 is electrically and mechanically connected with theconductor 101 and extends further longitudinally ac ross thewall 201. It is possible that a longer electrical c onductor101 which extends further across the wall 201 is pr ovided andthe conductor extension 108 is omitted. For exampl e, theconductor 101 extends through the whole axial lengt h of themain part112.The main part 112 extends axially across the wall 2 01 toprovide an electrical insulation inside the tank in theliquid 103.In particular,the end 127 ofthe main part112 extendslongerinto the tankin the medium voltage bushingsthan in the low voltage bushings according to Figur es 1 to 5.Figure 7 shows an embodiment of the bushing 100 wit h adifferent mounting of the bushing 100 to the wall 2 01 thanshown in Figures6 and 8. P2024,0078 WO N / P230197WO01 February26,2025 -23 -The flange 118 comprises an opening 120 through whi ch amounting element123 extends.Thus,the additional flangeclamp 111 can be omitted. The mounting interface isintegrated in the flange 118. Thus, the main part 1 12 madeout of the thermoplastic material provides the moun tinginterface for fixing the bushing 100 to the wall 20 1.The main body111 comprisesadditionalflange ribs 170.The additionalflange ribs170 are arranged to provide additionalmechanical reinforcement to the flange 118. The fla nge 118with the opening 120 which serves as a mounting int erfaceincorporates the mounting interface in the thin wal lthermoplastic structure of the main part 112. The a dditionalflange ribs 170 and the mounting interface of the f lange 118are located in an area that is shielded from exposu re toelectric fields by a suitable shielding structure ( notexplicitly shown). Thus, if contamination gets coll ected inthe area of the opening 120, it does not have a neg ativeinfluence on the insulation properties of the insul ator body110.For example, the opening 120 and / or the flange ribs 170 arepositioned in an area screened from electricfield stressbyappropriate shielding structure (not explicitly sho wn), sothat,in case contamination getscollected in that area,it doesnothave negative influence on the insulation properties ofthe insulatorbody110.The main body 112 with the integrated mounting feat ure on theouter flange 118 has less components by avoiding th e flangeclamp 111 and a robustmechanicstructure. P2024,0078 WO N / P230197WO01 February26,2025 -24 -Figure 8 shows an embodiment with the main part 112 accordingto Figure 6 with additional corrugations 134 on the main part112 inside the tank in the liquid 103. In addition, furtherprojecting ribs133 are arranged on the innerpart 117 which isprovided corresponding to the innerpart117 as shown in Figure 4.The further projecting ribs 133 project radially in wardtowardsthe conductor100 from the innerpart117. Thefurther projecting ribs 133 are elongated along thelongitudinal axis 102 like the projecting ribs 130. Thefurtherprojecting ribscomprise each the free end 135.Theprojecting ribs 130 have no free ends 135 and do no t directlyface the electricalconductor101 due to the inner part117. The furtherprojecting ribs133 and the innerpart 117provide more mechanical resistance against cantilev er forces104,even with a largerlongitudinallength ofthe insulatorbody 110. Furthermore, a second barrier for electri cinsulation between the conductor 101 and the tank w all 201 isprovided.The inner part 117 is shorter along the longitudina l axis 102than the main part112.In particular,the further projectingribs 133 and the projecting ribs 130 are shorter th an theinner part 117 and the man part 112. Thus, a long c reepagelength in the liquid 103 is provided for a reliable electricinsulation.The corrugations 134 are formed to further extend t hecreepage length in the insulating liquid 103. P2024,0078 WO N / P230197WO01 February26,2025 -25 -Figures 9 and 10 show embodiments of the bushing 10 0 with anadditional outer cover 150. The outer cover 150 can becombined with the embodiments of Figures 1 to 5, ac cording towhich the main part 112 comprises a plurality of se parateparts, as shown in Figure 9. The outer cover 150 ca n also beprovided at the other embodiments as shown in Figur es 6 to 8,according to which the main part 112 is provided by onesingle piece. This is exemplarily shown in Figure 1 0.The outer cover 150 comprises an elastomeric materi al 151 orconsists of the elastomeric material 151. For examp le, theelastomeric material 151 is silicone rubber which p rovides ahydrophobicsurface.The elastomeric material 151 is chemically bonded t o thethermoplastic material 115 of the main part 112. Th e chemicalbond provides a cohesive connection between the ela stomericmaterial 151 of the cover 150 and the thermoplastic material115 of the main part 112. In particular, the connec tioncannotbe detached non-destructively.The elastomeric material 151 and the outer cover 15 0 providesa hydrophobicity recovery and hydrophobicity transf erproperties, which make the hydrophobic nature of it s surfacepersist during most of the time of operation of the bushing,also in polluted environments, thus minimizing leak agecurrents running along the surface of the main part 112 inwetconditions.Thus,the probabilityofa surface dischargeand / or electrical breakdown is reduced by the cover 150. Theprocessofhydrophobicityrecovery,afteran event renderingthe silicone rubber surface less hydrophobic or eve nhydrophilic, such as activity of plasma generated b yneighboring electricarcoran extreme rainfallof long P2024,0078 WO N / P230197WO01 February26,2025 -26 -duration, is described, for example, in D. Bodas an d C. Khan-Malek, Sens. Actuators B: Chem. vol. 123, p. 368 (2 007). Theprocess of hydrophobicity transfer, i.e., transferr ing thehydrophobicpropertiesofthe silicone rubberonto thepollution layers accumulating on its surface during serviceofthe insulator,isdescribed,forexample,in A. Hergert, etal.,IEEE Trans.Dielectr.Electr.Insul.,vol. 24,no.2, p.1057 (2017). The elastomericmaterial151 forexample isone of moldableor extrudable liquid silicone rubber, high consiste ncyrubber, and high temperature vulcanization silicone rubber.For example, the curable elastomeric material 151 i s appliedin liquid form and then hardens to form the cover 1 50.Self-adhesive silicone rubber can be used to produc e theouter cover 150. Without being bound to it, example s forself-adhesive silicone rubber are described in EP 0 497349,US 4,742,103,EP 0493791 A1,EP 0497349 B1,US 5,595,826,EP 0875536 B1, US 6,743,515 B1, US 2003 / 0236380 A 1, and US2005 / 0089696A1, the contents of which are hereby in corporatedby reference. Other examples include SILASTIC™ SA 9 940compositions from Dow Chemical Company, Silopren™ L SR 2740from Momentive Performance Materials Inc., or ELAST OSIL® LR3070 grades from Wacker Chemie AG. The self-adhesiv e siliconerubber contains chemical coupling agents to form th e chemicalbond between the outer side 129 of the thermoplasti c material115 of the main part 112 and the solidified silicon e rubber.In particular, silane-based agents chemically react ive bothwith the surface ofthe thermoplasticmaterial115 and withthe other components of the elastomeric material 15 1, inparticular the silicone rubber mixture and / or other P2024,0078 WO N / P230197WO01 February26,2025 -27 -constituents of the curable elastomer composition f orming theelastomeric material, in particular the curable sil iconeelastomer composition, are provided to establish th e chemicalbond.As shown in Figure 9, the upper part 121 is covered by theouter cover 150 on an outward-facing side as well a s on a aninward-facing side facing the conductor 101. The lo wer part122 iscovered bythe outercover150 on the outer side 129.The cover is arranged such that, for example, all s urfaces ofthe main part 121 exposed to the environment, in pa rticularthe airenvironment,are covered bythe cover150.The cover 150 in particular comprises in most parts the samethickness 182 perpendicular to the surface of the u pper part121 and the lower part 122 within normal tolerances of forexample 5%.Forexample,the thicknessisconstant and the same in mostofthe cover150,forexample in more than 75%,more than 80%, more than 90% or more than 95% of th e cover150.Forexample,a thickness182 ofthe cover150 transverseto outer site 129 of the main part 112 is between 0 .5 mm and5 mm. The thickness may be different in the corners , forexample at the connection 119, or at the ends of th e cover150.Figure 10 shows the outer cover 150 which forms wea ther sheds152. The weather sheds 152 are made out of the elas tomericmaterial151.The outercover150 coversthe outer side 129 ofthe main part112 and additionallyprovidesthe weathersheds 152. Two weather sheds 152 are shown in Figur e 10. Itisalso possible thatonlyone single weathershed 152 is formed outofthe elastomericmaterial151 ormore than twoweather sheds 152 are formed out of the elastomeric material P2024,0078 WO N / P230197WO01 February26,2025 -28 -151, for example three or more weather sheds 152. T he weathersheds 152 provide an elongated creepage length. The thin wallthermoplastic main part 112 can be used and additio nally theweathersheds152 can be easilyprovided.The different features of the different embodiments accordingto Figures1 to 10 can be combined with each other in anycombination. For example, the outer cover 150 can b e providedat any of the embodiments according to Figures 1 to 8. Everyfeature described with respect to one of the embodi ments isalso disclosed herein with respect to the other emb odiments,even if the respective feature is not explicitly me ntioned inthe context of the specific embodiment. For example , thebushing 100 according to thisdisclosure comprises atleastone or more of the following in any combination: th e innerpart 117 attached to the inner edges of the ribs 13 0 foradding more withstand to the vertical compression f orces 105,one or mor weather sheds 116, 152 attached to the a ir-end ofthe main part 112 of the insulator body 110 for pro vidingelectric insulation between the conductor 108 and t he tankwall 201, flange mounting features integrated in th e thin-wall structure of the main part 112 like the openin g 120,corrugations 134 on the oil-end of the main part 11 2 toincrease the creepage length ofthe oilend ofthe bushing100, oil-end extension of the inner part 117 for pr ovidingadditional insulation on the oil end, extensions of theflange ribs 170 forming gasket holders to precisely centerthe gasket 160 and to hold it together with the ins ulatorbody 110 when assembling the bushing 100 on the app aratus200, and the cover 150 molded out of silicone rubbe r on theair end of the main part 112 with hydrophobic surfa ce andchemicallybonded to the main part112. P2024,0078 WO N / P230197WO01 February26,2025 -29 -The bushing 100 with the projecting ribs 130 provid es areliable reinforcementagainstdeflection.A shortmanufacturing process time and low material consump tion ispossible.The projecting ribs130 provide a robust mechanicalstructure, in particular against the compression fo rces 105,106 and the cantilever force 104 both at elastic lo ads (shorttime) and against creep (long time). Thus, a reliab le bushing100 isprovided.

[0002] P2024,0078 WO N / P230197WO01 February26,2025 -30 - Reference Signs 100 bushing 101 electricalconductor 102 longitudinalaxis 103 liquid 104 cantileverforce 105 compression force 106 furthercompression force 107 support 108 conductorextension 109 gap 110 insulatorbody 111 flange clamp 112 main part 113 hollow cylindershape 114 innerside 115 thermoplasticmaterial 116 weathershed 117 innerpart 118 outerflange 119 connection 120 opening 121 upperpart 122 lowerpart 123 mounting element 124 wallthickness 125 sealseat 126 holder 127 end 128 hood 129 outerside 130 projecting rib P2024,0078 WO N / P230197WO01 February26,2025 -31 - 131 main extension 132 rib thickness 133 furtherprojecting rib 134 corrugation 135 free end 140 conductorseal 150 outercover 151 elastomericmaterial 152 weathershed 160 gasket 170 flange rib 182 coverthickness 190 free space 195 oil 200 electricalapparatus201 wall

Claims

P2024,0078 WO N / P230197WO01 February26,2025 -32 - Claims1. A bushing (100) for a liquid-insulated electrica lapparatus(200),the bushing (100)comprisingan electrical conductor (101) and an insulator body (110)through which the electrical conductor (101) extend s, whereinthe insulator body (110) comprises a main part (112 ) and aplurality of projecting ribs (130), wherein the mai n part(112) comprises a hollow cylinder shape (113) and w herein theprojecting ribs (130) each project radially inwards from themain part (112) and wherein the projecting ribs (13 0)comprise each a main extension (131) along a longit udinalaxis (102) of the conductor (101) and a free end (1 35) facingthe electricalconductor(101).

2. The bushing of claim 1, wherein the main part (1 12) isformed in one piece.

3. The bushing of claim 1, wherein the main part (1 12)comprises two or more separate parts (121, 122) sta cked alongthe longitudinalaxis(102). 4.The bushing ofanyone ofthe preceding claims, whereinthe main part (112) is made of thermoplastic (115).5.The bushing ofanyone ofthe preceding claims, comprisingan outer cover, wherein the outer cover (150) is ma de of anelastomeric material (151) and covers the main part (112) atleast party, in particular comprising a weather she d (152),the weather shed (152) being an integral part of th e outercover(150).P2024,0078 WO N / P230197WO01 February26,2025 -33 - 6.The bushing ofanyone ofthe preceding claims, wherein a free space (190)isarranged between the insulator body(110) and the electricalconductor(101). 7.The bushing ofanyone ofthe preceding claims, whereinthe main part (112) comprises an outer flange (118) thatprojects radially outwards from the main part (112) , whereinthe outer flange (118) is an integral part of the m ain part(112).

8. The bushing of claim 7, wherein a plurality of f lange ribs(170) is arranged between the outer flange (118) an d the mainpart (112), wherein the flange ribs (170) project r adiallyoutwardsfrom the main part(112). 9.The bushing ofclaim 8,wherein atleasta part oftheflange ribs (170) is configured to hold a gasket (1 60).

10. The bushing of any one of claims 7 to 9, wherei n theprojecting ribs (130) extend axially across a conne ction(119) between the main part (112) and the outer fla nge (118).

11. The bushing of any one of claims 7 to 10, where in theouter flange (118) comprises an opening (120) throu gh whichan elongated mounting element (123) can protrude to fix themain part(112)to the electricalapparatus(200).

12. The bushing of any one of claims 7 to 11, where in themain part (112) extends axially below the outer fla nge (118).

13. The bushing of any one of the preceding claims, whereinthe projecting ribs (130) each comprises a rib thic kness(132)transverse to the direction ofprojection of 0.5 mm toP2024,0078 WO N / P230197WO01 February26,2025 -34 -10 mm, in particular the projecting ribs (130) each comprisesa rib thickness (132) transverse to the direction o fprojection and the main part (112) comprises a wall thickness(124) along the radial direction, wherein the rib t hickness(132) is between 25% and 100% of the wall thickness (124).

14. A liquid-insulated electrical apparatus (200) c omprisingthe bushing (100) according to any one of the prece dingclaimsand a wall(201)in which the bushing (100) is installed.

15. The apparatus of claim 14, wherein the projecti ng ribs(130)extend axiallyacrossthe wall(201).

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