EP4625446A1 - Bushing and electrical apparatus - Google Patents

Bushing and electrical apparatus

Info

Publication number
EP4625446A1
EP4625446A1 EP24166820.1A EP24166820A EP4625446A1 EP 4625446 A1 EP4625446 A1 EP 4625446A1 EP 24166820 A EP24166820 A EP 24166820A EP 4625446 A1 EP4625446 A1 EP 4625446A1
Authority
EP
European Patent Office
Prior art keywords
main part
bushing
flange
ribs
projecting ribs
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP24166820.1A
Other languages
German (de)
French (fr)
Inventor
Jan Czyzewski
Robert Platek
Cenk Kurtulus
Orhan Akbas
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hitachi Energy Ltd
Original Assignee
Hitachi Energy Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hitachi Energy Ltd filed Critical Hitachi Energy Ltd
Priority to EP24166820.1A priority Critical patent/EP4625446A1/en
Priority to PCT/EP2025/055185 priority patent/WO2025201785A1/en
Publication of EP4625446A1 publication Critical patent/EP4625446A1/en
Pending legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B17/00—Insulators or insulating bodies characterised by their form
    • H01B17/26—Lead-in insulators; Lead-through insulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B17/00—Insulators or insulating bodies characterised by their form
    • H01B17/32—Single insulators consisting of two or more dissimilar insulating bodies
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B17/00—Insulators or insulating bodies characterised by their form
    • H01B17/34—Insulators containing liquid, e.g. oil

Definitions

  • the present disclosure relates to a bushing and a liquid insulated electrical apparatus comprising the bushing.
  • the electrical apparatus may be a transformer or a switchgear, for example.
  • a bushing for example enables a conductor to pass through a wall of an electrical apparatus, providing electrical insulation between the conductor and the wall.
  • Embodiments of the disclosure relate to a bushing.
  • the bushing is configured for a liquid insulated electrical apparatus.
  • the bushing comprises an electrical conductor.
  • the bushing comprises an insulator body.
  • the electrical conductor extends through the insulator body.
  • the insulator body comprises a main part.
  • the main part can be also referred to as insulator core.
  • the insulator body comprises a plurality of projecting ribs.
  • the main part comprises a hollow cylinder shape.
  • the conductor extends through this hollow cylinder.
  • the projecting ribs each project radially inwards from the main part.
  • the projecting ribs are internal ribs.
  • the projecting ribs comprise a main extension along a longitudinal axis of the conductor.
  • the projecting ribs are configured to mechanically support the main part of the insulator body.
  • the projecting ribs are configured to transfer forces along the longitudinal axis. Thereby the main part is reinforced.
  • the projecting ribs allow, for example, a thin wall structure of the main part.
  • the insulator body can be formed with a reduced material usage.
  • the thin wall structure of the thermoplastic material makes the time needed for heat transfer through the wall thickness short, in particular the time needed to cool down the molten thermoplastic material until it solidifies in the mold.
  • the thin-walled main part with the reinforcing internal projecting ribs realize a reduced external circumference of insulator body. This increases the electric resistance of the surface of the insulator body 110 and decreases the surface leakage currents in operation, for example.
  • the outer side is more resistant against dust and particles contamination than a design with outer ribs. Such contamination on the outer side 129 would lead to a local reduction of an electric resistance of the surface of the insulator, thus increasing the leakage current and potentially causing surface discharges or a flashover. This is avoided by the internal reinforcement ribs. For example, with the outer side without reinforcement structures it is easier to clean the outer side.
  • the insulator body in particular the main part and the projecting ribs, are made out of a thermoplastic material.
  • the insulator body, in particular the main part, and the projecting ribs comprise a thermoplastic material.
  • the main part and the projecting ribs consist of a thermoplastic material.
  • the thermoplastic material is an electrically insulating material.
  • the thermoplastic material comprises a high elastic modulus and mechanical strength, even at elevated temperatures, and is resistant to thermal degradation. It is also resistant to chemical degradation, in particular by electric insulation liquids, for example by transformer oil and natural or synthetic esters.
  • the thermoplastic material is at least one of polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polyphthalamide (PPA), polyethersulfone (PES), polyetherimide (PEI), polyamide (PA), and semi-aromatic polyamide.
  • the main part and/or the projecting ribs comprise a glass fiber reinforcement.
  • the thermoplastic material is reinforced by the glass fiber filler.
  • the thermoplastic material is one of the listed polymeric materials filled with glass fibers.
  • ceramic materials can be omitted.
  • the projecting ribs provide sufficient stability such that thermoplastic material can be used instead of ceramic material.
  • the projecting ribs extend longitudinally elongated along the longitudinal axis.
  • the projecting ribs extend along the conductor.
  • the projecting ribs face the conductor without being in direct contact with the conductor.
  • the projecting ribs radially extend between an inner side of the main part and the conductor.
  • Each of the projecting ribs is longer along the longitudinal axis than along the two other spatial directions running transverse to it.
  • each projecting rib comprises a rib thickness transverse to the direction of projection.
  • Each projecting rib extends longer along the longitudinal axis than along the direction of projection and longer than the rib thickness.
  • the rib thickness and an extension along the direction of projection is shorter than the extension along the longitudinal axis. This elongated extension along the longitudinal axis enables a reliable reinforcement.
  • the bushing comprises a conductor seal.
  • the conductor seal is arranged axially between an upper part and a lower part of the two or more parts.
  • the upper part is fixed to the electrical conductor such that the upper part exerts a force on the conductor seal towards the lower part.
  • the upper part is formed inclined downward to overlap the lower part at least in part.
  • the inner surface of the conductor seal matches the conductor and the outer surface matches the insulator body.
  • the upper part is used to provide a seal compressing force along the longitudinal axis.
  • the conductor seal is fixed between the lower part and the upper part by the force exerted between the upper part and the lower part.
  • the lower part is supported on a wall of the electrical apparatus.
  • the upper part is fixed to the electrical conductor such that the lower part and the upper part with the conductor seal in between are pressed against each other.
  • the two or more separate parts of the main part are made of thermoplastic.
  • all of the separate parts are made of thermoplastic, or just some of the separate parts are made of thermoplastic.
  • the upper part is made of thermoplastic.
  • the main part is an injection molded body.
  • the two or more separate parts each are injection molded bodies. Injection molding realizes a simple, cost-effective and material-saving production of the main part.
  • the main part comprises a longer extension along the axial direction than the inner part. This enables a long creepage length inside the electrical apparatus. Thus, a reliable electric insulation is realized.
  • the outer flange is configured to hold a gasket. This ensures that the gasket is reliably held in place.
  • the bushing and the electrical apparatus are reliably sealed against fluids.
  • a plurality of flange ribs is arranged between the outer flange and the main part.
  • the flange ribs project radially outwards from the main part.
  • the flange ribs reinforce the flange and thereby limit a flange detection.
  • the position of the flange ribs between the main part and the outer flange enables the surface resistance of the insulator body to be increased because the length of the outer circumference of the main part can be reduced.
  • At least a part of the flange ribs is configured to hold the gasket.
  • the gasket is reliably held in place, even during transport before being mounted on the electrical apparatus.
  • the outer flange comprises an opening.
  • An elongated mounting element can protrude through the opening to fix the main part to the electrical apparatus.
  • no additional clamps are necessary to mount the bushing on the electrical apparatus.
  • a threaded stud welded to the wall of the electrical apparatus and extending through the opening and a nut threaded on the stud holds the flange in place.
  • the projecting ribs each comprise the rib thickness transverse to the device of projection with a value of 0.5 mm or more and 10 mm or less.
  • the rib thickness is between 25% and 100% of the wall thickness.
  • the rib thickness is the same size or smaller than the wall thickness.
  • reliable reinforcement and material-saving manufacturing are possible.
  • the ribs 130 are tapered towards the conductor, in particular to simplify removal from the mold during manufacturing.
  • the liquid insulated electrical apparatus comprises the bushing according to one of the embodiments described herein or according to any combination of the described embodiments.
  • the liquid insulated electrical apparatus comprises a wall in which the bushing is installed. The bushing enables the conductor to pass through the wall and provides an electrical insulation between the conductor and the wall.
  • the electrical apparatus may be a low voltage apparatus, a medium voltage apparatus and/or a high voltage apparatus.
  • the electrical apparatus is a transformer or another electrical apparatus.
  • the electrical apparatus comprises a tank in which one or more electrical functional elements are located.
  • a winding such as a transformer winding, may be located in the tank.
  • the tank is filled by an insulating liquid.
  • the projecting ribs extend axially across the wall.
  • the projecting ribs extends from an outside of the tank to an inside of the tank of the electrical apparatus.
  • the projecting ribs extend transverse to the wall. This enables a reliable reinforcement of the insulator body along the entire extension of the insulator body.
  • Figures 1 to 10 schematically show different embodiments of a bushing and an electrical apparatus.
  • the embodiments of Figures 1 to 5 and 9 in particular are applicable for low voltage bushings 100.
  • the embodiments of Figures 6 to 8 and 10 in particular are applicable for medium voltage bushings 100.
  • Ratings may cover AC or DC voltages.
  • a range from 0.1kV to 72.5kV, in particular from lkV to 3.6kV is referred to as low voltage.
  • a range from 3kV to 72.5kV is referred to as medium voltage (MV), in particular lager than 3.6 kV.
  • current rating is from 100 A to 10000 A.
  • Figures 1 , 3 , 4 and 5 each show a horizontal section on the left-hand side along line A-A of the right-hand side, which shows part of a vertical section.
  • Figure 1 schematically shows an embodiment of the bushing 100 installed in a wall 201 of an electrical apparatus 200.
  • the electrical apparatus 200 for example is a liquid insulated electrical apparatus like a transformer or a reactor.
  • An insulating liquid 103 is arranged in a tank which is bounded by the wall 201.
  • the bushing 100 provides an electrical connection of the electrical apparatus 200 through the wall 201 from an outside to an inside.
  • the wall 201 may be on earth potential or at least on an electrical potential that is potentially different from the potential of a conductor 101 of the bushing 100.
  • An insulator body 110 of the bushing 100 provides an electrical insulation between the wall 201 and the electrical conductor 101.
  • the bushing 100 comprises a rotationally symmetrical and/or mirror-symmetrical shape.
  • the insulator body 110 surrounds the electrical conductor 101.
  • the electrical conductor 101 extends through the insulator body 110 along a longitudinal axis 102.
  • the electrical conductor 101 extends elongated along the longitudinal axis 102.
  • a part of the insulator body 110 is exposed to the air environment, typically outdoor environment, and another part of the insulator body 110 is immersed in the insulating liquid 103 of the apparatus 200.
  • the insulator body comprises a plurality of projecting ribs 130.
  • the projecting ribs 130 are arranged on the inner side 114 of the main part 112.
  • the main part 112 and the projecting ribs 130 are formed as a single piece.
  • the projecting ribs 130 each comprise a main extension 131 which extends in a direction along the longitudinal axis 102.
  • the projecting ribs 130 extend elongated along the longitudinal axis 102.
  • the insulator body 110 is made of thermoplastic material 115.
  • the insulator body 110 with the hollow cylinder shape 113 and the projecting ribs 130 for example is manufactured by a single injection molding process.
  • the insulator body 110 comprises a flange 118 which radially projects outwards from outer side 129 of the main part 112.
  • the outer side 129 is arranged radially opposite the inner side 114.
  • the flange 118 is configured to provide a mounting of the bushing 100 to the wall 201.
  • a gasket 160 is arranged between the flange 118 and the wall 201 to provide a fluid-tight connection.
  • the main part 112 comprises an upper part 121 and a lower part 122.
  • the lower part 122 comprises the hollow cylinder shape 113 and the projecting ribs 130 as well as the flange 118.
  • the upper part 121 is arranged on an end of the lower part 122 facing away from the wall 201 along the longitudinal axis 102.
  • the upper part 121 is inclined with respect to the longitudinal axis 102 and overlaps the lower part 122 in part. Thus, the upper part forms a weather shed and extends the creepage path along the outer side 129.
  • the upper part 121 is fixed to the conductor 101 by a holder 126.
  • the lower part 122 is arranged on the wall 201.
  • a conductor seal 140 is arranged on the conductor 101 and pressed vertically along the longitudinal axis 102 against a seal seat 125 of the lower part 122 by the upper part 121. This compression force 105 is maintained by fixing the upper part 121 with the holder 126 at the conductor 101.
  • a gap 109 is arranged axially between the upper part 121 and the lower part 122.
  • the transition between the upper part 121 and the lower part 122 is sealed via the conductor seal 140.
  • the conductor 101 is supported via an insulating support 107 at the wall 201.
  • the main part 112 extends elongated over the wall 201 towards the support 107 along the longitudinal axis 102.
  • the projecting ribs 130 extend over the wall 201 along the longitudinal axis 102.
  • the main part 112 is reinforced by the projecting ribs 130 also inside the tank of the electrical apparatus 200. This allows a better resistance against the cantilever force 104.
  • An end 127 of the main part 112 facing away from the seal seat 125 along the longitudinal axis 102 protrudes over the projecting ribs 130 along the longitudinal axis 102. The length of this protrusion is large enough to prevent an electric flashover to happen in the insulating liquid 103 between the tank wall 201 and the conductor 101 of the bushing 100.
  • the flange ribs 130 enable a robust mechanical structure against flange deflection of the flange 118 under the cantilever force 104 and the compression forces 105, 106.
  • the arrangement of the projecting ribs 130 on the inner side 114 of the main part 112 makes the outer side 129 smoother. Thereby a contamination collection is reduced.
  • FIG 3 shows an embodiment of the bushing 100 which corresponds to the embodiment of Figure 1 .
  • flange ribs 170 are provided.
  • the flange ribs 170 are arranged at the flange 118 to support the flange 118 against a bending and/or deformation.
  • the flange ribs 170 are radially arranged between the outer side 129 and the flange 118 on a side of the flange 118 facing the wall 201.
  • the flange ribs 170 can be elongated along the longitudinal axis 102 to provide a support and fixation for the gasket 160.
  • at least some of the flange ribs 170 are elongated to hold the gasket 160 in an unmounted state, such that a detachment of the gasket 160 from the flange 118 can be avoided.
  • the projecting ribs 130 and the flange ribs 117 are shown radially aligned. It is also possible to provide an offset arrangement of the flange ribs 170 and the projecting ribs 130.
  • the flange ribs 170 provide a robust mechanical structure against flange deflection under cantilever forces 104, and under compression forces 105, 106.
  • the placement of the flange ribs 170 on the side of the flange 118 facing the wall 201 contributes to a smooth outer area of the flange 118, which helps to avoid contamination.
  • Figure 4 shows an embodiment of the bushing 100 which corresponds substantially to the embodiment of Figure 3 .
  • the insulator body 110 additionally comprises an inner part 117.
  • the inner part 117 comprises a hollow cylinder shape and is coaxially arranged with the main part 112.
  • the inner part 117 provides additional rigidity, in particular against the compression 105, 106. Further, the inner part 117 may constitute an additional barrier for electric insulation between the conductor 101 and the wall 201.
  • the projecting ribs 130 radially extend between the main part 112 and the inner part 117.
  • FIG. 4 shows the inner part 117 and the flange rib 170. According to a further embodiment, the inner part 117 is provided and the flange rib 170 is omitted.
  • Figure 5 shows an embodiment with elongated flange ribs 170 which serve as holders for the gasket 160, as already mentioned above.
  • four of the flange ribs 170 are elongated to hold the gasket 160.
  • this number is just an exemplary number. It is possible to have less elongated flange ribs 170 as holders for the gasket 160 or more than four elongated flanges 170.
  • the elongated flange ribs 170 keep the gasket 160 in place and centred during installation on the wall 201 and also during operation.
  • Figures 6 to 8 show embodiments of the bushing 100 with the main part realized in one single piece.
  • the upper part 121 as for example shown in Figures 1 to 5 , is replaced by a hood 128.
  • the hood 128 is, for example, not made of thermoplastic material.
  • the hood 128 for example comprises an electrically conductive material, for example metal.
  • the conductor seal 140 is pressed between the hood 128 and the seal seat 125 of the main part 112.
  • the hood 128 is fixed to the conductor 101.
  • the main part 112 comprises weather sheds 116.
  • the weather sheds extend the creepage path.
  • the weather sheds 116 are formed as integral parts of the main part 112.
  • the main part 112, with the projecting ribs 130 and the weather sheds 116, is formed as one single piece.
  • Figures 6 to 8 exemplarily show two weather sheds 116. It is also possible to provide just one single weather shed 116 or more than two weather sheds 116, for example three or more.
  • the weather sheds 116 radially project outwards on the outer side 129 of the main body 112.
  • the projecting ribs 130 and the weather sheds 116 are arranged radially opposite each other.
  • the insulator body 110 is fixed to the wall 201 by a flange clamp 111.
  • the flange clamp 111 is a separate part which is fixed to the wall 201, for example by a screw connection and exerts a force on the flange 118.
  • de-airing is incorporated in the conductor 101 to degas the inner volume of the bushing 100 when installed on the apparatus 200 and filled with insulating liquid 103.
  • an additional metallic intermediate ring is arranged between the main part 112 and the hood 128. The conductor seal 140 is compressed between this ring and the hood 128. De-airing is provided in the ring in this embodiment.
  • the electrical conductor 101 extends only partly along the main part 112.
  • An electrically conductive conductor extension 108 is electrically and mechanically connected with the conductor 101 and extends further longitudinally across the wall 201. It is possible that a longer electrical conductor 101 which extends further across the wall 201 is provided and the conductor extension 108 is omitted. For example, the conductor 101 extends through the whole axial length of the main part 112.
  • the main part 112 extends axially across the wall 201 to provide an electrical insulation inside the tank in the liquid 103.
  • the end 127 of the main part 112 extends longer into the tank in the medium voltage bushings than in the low voltage bushings according to Figures 1 to 5 .
  • the flange 118 comprises an opening 120 through which a mounting element 123 extends.
  • the mounting interface is integrated in the flange 118.
  • the main part 112 made out of the thermoplastic material provides the mounting interface for fixing the bushing 100 to the wall 201.
  • the main body 111 comprises additional flange ribs 170.
  • the additional flange ribs 170 are arranged to provide additional mechanical reinforcement to the flange 118.
  • the flange 118 with the opening 120 which serves as a mounting interface incorporates the mounting interface in the thin wall thermoplastic structure of the main part 112.
  • the additional flange ribs 170 and the mounting interface of the flange 118 are located in an area that is shielded from exposure to electric fields by a suitable shielding structure (not explicitly shown). Thus, if contamination gets collected in the area of the opening 120, it does not have a negative influence on the insulation properties of the insulator body 110.
  • the opening 120 and/or the flange ribs 170 are positioned in an area screened from electric field stress by appropriate shielding structure (not explicitly shown), so that, in case contamination gets collected in that area, it does not have negative influence on the insulation properties of the insulator body 110.
  • Figure 8 shows an embodiment with the main part 112 according to Figure 6 with additional corrugations 134 on the main part 112 inside the tank in the liquid 103.
  • further projecting ribs 133 are arranged on the inner part 117 which is provided corresponding to the inner part 117 as shown in Figure 4 .
  • the further projecting ribs 133 project radially inward towards the conductor 100 from the inner part 117.
  • the further projecting ribs 133 are elongated along the longitudinal axis 102 like the projecting ribs 130.
  • the further projecting ribs 133 and the inner part 117 provide more mechanical resistance against cantilever forces 104, even with a larger longitudinal length of the insulator body 110. Furthermore, a second barrier for electric insulation between the conductor 101 and the tank wall 201 is provided.

Landscapes

  • Insulators (AREA)

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 part (112) and wherein the projecting ribs (130) comprise a main extension (131) along a longitudinal axis (102) of the conductor (101).

Description

  • The present disclosure relates to a bushing and a liquid insulated electrical apparatus comprising the bushing. The electrical apparatus may be a transformer or a switchgear, for example.
  • A bushing for example enables a conductor to pass through a wall of an electrical apparatus, providing electrical insulation between the conductor and the wall.
  • It is desirable to provide a bushing that provides a reliable operation.
  • Embodiments of the disclosure relate to a bushing. In particular, the bushing is configured for a liquid insulated electrical apparatus.
  • The bushing comprises an electrical conductor. The bushing comprises an insulator body. The electrical conductor extends through the insulator body. The insulator body comprises a main part. The main part can be also referred to as insulator core. The insulator body comprises a plurality of projecting ribs. The main part comprises a hollow cylinder shape. The conductor extends through this hollow cylinder. The projecting ribs each project radially inwards from the main part. The projecting ribs are internal ribs. The projecting ribs comprise a main extension along a longitudinal axis of the conductor.
  • The projecting ribs are configured to mechanically support the main part of the insulator body. The projecting ribs are configured to transfer forces along the longitudinal axis. Thereby the main part is reinforced. The projecting ribs allow, for example, a thin wall structure of the main part. The insulator body can be formed with a reduced material usage. The thin wall structure of the thermoplastic material makes the time needed for heat transfer through the wall thickness short, in particular the time needed to cool down the molten thermoplastic material until it solidifies in the mold.
  • The thin-walled main part with the reinforcing internal projecting ribs realize a reduced external circumference of insulator body. This increases the electric resistance of the surface of the insulator body 110 and decreases the surface leakage currents in operation, for example. The outer side is more resistant against dust and particles contamination than a design with outer ribs. Such contamination on the outer side 129 would lead to a local reduction of an electric resistance of the surface of the insulator, thus increasing the leakage current and potentially causing surface discharges or a flashover. This is avoided by the internal reinforcement ribs. For example, with the outer side without reinforcement structures it is easier to clean the outer side.
  • For example, the insulator body, in particular the main part and the projecting ribs, are made out of a thermoplastic material. In particular, the insulator body, in particular the main part, and the projecting ribs, comprise a thermoplastic material. For example, the main part and the projecting ribs consist of a thermoplastic material. The thermoplastic material is an electrically insulating material. In particular, the thermoplastic material comprises a high elastic modulus and mechanical strength, even at elevated temperatures, and is resistant to thermal degradation. It is also resistant to chemical degradation, in particular by electric insulation liquids, for example by transformer oil and natural or synthetic esters.
  • For example, the thermoplastic material is at least one of polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polyphthalamide (PPA), polyethersulfone (PES), polyetherimide (PEI), polyamide (PA), and semi-aromatic polyamide. For example, the main part and/or the projecting ribs comprise a glass fiber reinforcement. Thus, the thermoplastic material is reinforced by the glass fiber filler. For example, the thermoplastic material is one of the listed polymeric materials filled with glass fibers. In particular, ceramic materials can be omitted. The projecting ribs provide sufficient stability such that thermoplastic material can be used instead of ceramic material.
  • The projecting ribs extend longitudinally elongated along the longitudinal axis. The projecting ribs extend along the conductor. In particular, the projecting ribs face the conductor without being in direct contact with the conductor. The projecting ribs radially extend between an inner side of the main part and the conductor. Each of the projecting ribs is longer along the longitudinal axis than along the two other spatial directions running transverse to it. For example, each projecting rib comprises a rib thickness transverse to the direction of projection. Each projecting rib extends longer along the longitudinal axis than along the direction of projection and longer than the rib thickness.
  • The rib thickness and an extension along the direction of projection is shorter than the extension along the longitudinal axis. This elongated extension along the longitudinal axis enables a reliable reinforcement.
  • The bushing realizes a mechanically robust insulator body using less material, which can be manufactured in a shorter time. The main part comprises the projecting ribs which for example keep the conductor centred and reinforce the insulator body against compression forces and transfers compression forces to an outer side of the main part, for example to a flange.
  • According to an embodiment, the main part is formed in one piece. Alternatively, the main part comprises two or more separate parts. The two or more separate parts are for example stacked along the longitudinal axis. By providing the main part in one single piece, manufacturing and mounting of the bushing can be quick and easy. Providing the main part with two or more separate parts for example enables a greater freedom of design. Different functionalities can be realized in different parts of the two or more separate parts.
  • According to an embodiment, the bushing comprises a conductor seal. The conductor seal is arranged axially between an upper part and a lower part of the two or more parts. The upper part is fixed to the electrical conductor such that the upper part exerts a force on the conductor seal towards the lower part. The upper part is formed inclined downward to overlap the lower part at least in part. The inner surface of the conductor seal matches the conductor and the outer surface matches the insulator body.
  • The upper part is used to provide a seal compressing force along the longitudinal axis. The conductor seal is fixed between the lower part and the upper part by the force exerted between the upper part and the lower part. For example, the lower part is supported on a wall of the electrical apparatus. The upper part is fixed to the electrical conductor such that the lower part and the upper part with the conductor seal in between are pressed against each other.
  • According to embodiments, the two or more separate parts of the main part are made of thermoplastic. For example, all of the separate parts are made of thermoplastic, or just some of the separate parts are made of thermoplastic. In particular, the upper part is made of thermoplastic.
  • According to an embodiment, the main part is an injection molded body. For example, the two or more separate parts each are injection molded bodies. Injection molding realizes a simple, cost-effective and material-saving production of the main part.
  • According to an embodiment, the bushing comprises a weather shed. The weather shed is, for example, an integral part of the main part. The weather shed, for example, increases the creepage length of the bushing. This ensures adequate electrical insulation even with a moisture covered surface, for example. Due to the design of the main part which, for example, is made of thermoplastic, the weather shed can be easily integrated into the main part. For example, the weather shed projects radially in the opposite direction to the projecting ribs. It is possible that more than one weather shed is provided as an integral part of the main body.
  • According to an embodiment, the bushing comprises an outer cover. The cover covers an outward facing portion of the main part. A majority, for example more than 750, more than 80%, more than 90% or more than 950 of the outer surface of the main part exposed to air and/or arranged outside the apparatus is covered by the cover. Another part of the surface of the main part which is exposed to the insulating liquid inside the apparatus is also not covered by the cover.
  • For example, the outer cover is made of an elastomeric material. The outer cover is fixed to the main part. The outer cover adheres firmly to the main part. The outer cover covers the main part at least partly. The outer cover houses the main part at least partly. The cover can also be referred to as housing or insulating housing. For example, the elastomeric material is silicone rubber or comprises silicone rubber. For example, the outer cover provides a hydrophobic surface. The outer surface of the outer cover does not easily collect contamination and is effectively cleaned by rainwater during operation or in a cleaning procedure provided when servicing the bushing.
  • According to an embodiment, the bushing comprises a weather shed which is an integral part of the outer cover. For example, the weather shed is completely formed out of the elastomeric material. It is also possible that the weather shed comprises a protrusion of the main part, which is covered by the outer cover, such that the weather shed is formed by the main part and the outer cover together.
  • According to an embodiment, the outer cover comprises a chemical coupling agent in the elastomeric material to form a chemical bond between the outer cover and the main part. For example, the outer cover is made of a so-called self-adhesive silicone rubber, in particular a so-called cured liquid silicone rubber containing chemical coupling agents able to form chemical bond between the surface of the thermoplastic material of the main body and the crosslinked silicone rubber material. In this case, no addition primer or other auxiliary materials are necessary to form the chemical bond between the outer cover and the main part. The chemical coupling agent as part of the elastomeric material forms the chemical bond to the main part, in particular to the thermoplastic material of the main part. Thus, it is sufficient to apply the elastomeric material including the chemical coupling agent in a liquid state on the main part. The chemical bond is formed during curing of the elastomeric material.
  • The combination of the use of the thermoplastic for the main part, the elastomeric material for the cover and the chemical bond to fix the main part and the cover to each other, for example makes the manufacturing process easier and faster. In particular, the thermoplastic has desired and preset surface properties directly after the molding process.
  • Self-adhesive elastomeric material in particular is suitable for low voltage usage. Faster manufacturing and low costs are realized to create a bond between the elastomeric material and the thermoplastic. For example, the bond might not be as strong as with the use of a separate primer but strong enough for the requirements and needs by a low voltage usage. In particular, the use of thermoplastic for the main part allows the use of self-adhesive elastomeric material, because these two materials bond together even without a separate primer.
  • According to an embodiment, a primer layer is provided between the main part and the outer cover. The primer layer forms a chemical bond to the main part and a further chemical bond to the outer cover. The primer layer enables the use of an elastomeric material without a chemical coupling agent. The primer layer is formed on the main part and forms a chemical bond to the main part. The elastomeric material of the outer cover is applied on the primer layer and the further chemical bond between the primer layer and the outer cover is formed. Thus, the primer layer enables a fixing of the outer cover and the main part together by chemical bonds.
  • According to an embodiment, the main part comprises an inner part. The inner part comprises a hollow cylinder shape. The main part and the inner part are arranged coaxially. The inner part comprises a smaller diameter than the main part. The inner part enables additional reinforcement of the main part. For example, the projecting rib projects between the main part and the inner part. For example, further projecting ribs are arranged inside of the inner part.
  • According to an embodiment, the main part comprises a longer extension along the axial direction than the inner part. This enables a long creepage length inside the electrical apparatus. Thus, a reliable electric insulation is realized.
  • According to an embodiment, the main part comprises an outer flange. The outer flange projects radially outwards from the main part. The outer flange is an integral part of the main part. The flange provides a mounting interface for the bushing to the electrical apparatus. For example, the bushing is fixed to the electrical apparatus at the outer flange.
  • According to an embodiment, the outer flange is configured to hold a gasket. This ensures that the gasket is reliably held in place. The bushing and the electrical apparatus are reliably sealed against fluids.
  • According to an embodiment, a plurality of flange ribs is arranged between the outer flange and the main part. The flange ribs project radially outwards from the main part. The flange ribs reinforce the flange and thereby limit a flange detection. The position of the flange ribs between the main part and the outer flange enables the surface resistance of the insulator body to be increased because the length of the outer circumference of the main part can be reduced.
  • According to an embodiment, at least a part of the flange ribs is configured to hold the gasket. Thus, the gasket is reliably held in place, even during transport before being mounted on the electrical apparatus.
  • According to an embodiment, the outer flange comprises an opening. An elongated mounting element can protrude through the opening to fix the main part to the electrical apparatus. Thus, no additional clamps are necessary to mount the bushing on the electrical apparatus. For example, a threaded stud welded to the wall of the electrical apparatus and extending through the opening and a nut threaded on the stud holds the flange in place.
  • According to an embodiment, the main part extends axially below the outer flange. This improves insulation and forces can be reliably dissipated to the outer flange. In particular, the projecting ribs extend axially below the outer flange. Thus, reinforcement is provided in the area of the outer flange where the bushing is supported on the wall of the electrical apparatus. Forces, in particular cantilever forces, can be reliably absorbed and distributed by the projecting ribs. Deformation of the main part in the area of the flange due to the forces can be avoided.
  • According to an embodiment, the insulator body comprises three projecting ribs or more. In particular, the insulator comprises more than five projecting ribs, more than seven projecting ribs, more than nine projecting ribs or more than 11 projecting ribs. In particular, the number of projecting ribs depends on the diameter of the bushing. For example, the number of ribs is not less than 3, in particular six ribs or more and 12 ribs or less. According to examples, the insulator body comprises more than 12 ribs.
  • According to an embodiment, the projecting ribs each comprise the rib thickness transverse to the device of projection with a value of 0.5 mm or more and 10 mm or less. For example, the rib thickness is between 25% and 100% of the wall thickness. In particular, the rib thickness is the same size or smaller than the wall thickness. Thus, reliable reinforcement and material-saving manufacturing are possible. According to examples, the ribs 130 are tapered towards the conductor, in particular to simplify removal from the mold during manufacturing.
  • Further embodiments of the disclosure relate to a liquid insulated electrical apparatus. The liquid insulated electrical apparatus comprises the bushing according to one of the embodiments described herein or according to any combination of the described embodiments. The liquid insulated electrical apparatus comprises a wall in which the bushing is installed. The bushing enables the conductor to pass through the wall and provides an electrical insulation between the conductor and the wall.
  • The electrical apparatus may be a low voltage apparatus, a medium voltage apparatus and/or a high voltage apparatus. As an example, the electrical apparatus is a transformer or another electrical apparatus.
  • The electrical apparatus comprises a tank in which one or more electrical functional elements are located. For example, a winding, such as a transformer winding, may be located in the tank. The tank is filled by an insulating liquid.
  • According to an embodiment, the projecting ribs extend axially across the wall. The projecting ribs extends from an outside of the tank to an inside of the tank of the electrical apparatus. The projecting ribs extend transverse to the wall. This enables a reliable reinforcement of the insulator body along the entire extension of the insulator body.
  • Hereinafter, the bushing and the electrical apparatus will be explained in more detail with reference to the drawings on the basis of exemplary embodiments. The accompanying figures are included to provide a further understanding. In the figures, elements of the same structure and/or functionality may be referred by the same reference signs. It is to be understood that the embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale. Insofar as elements or components correspond to one another in terms of their function in different figures, the description thereof is not necessarily repeated for each of the following figures.
  • Figures 1 to 10 schematically show different embodiments of a bushing and an electrical apparatus.
  • The embodiments of Figures 1 to 5 and 9 in particular are applicable for low voltage bushings 100. The embodiments of Figures 6 to 8 and 10 in particular are applicable for medium voltage bushings 100. Ratings may cover AC or DC voltages. For example, a range from 0.1kV to 72.5kV, in particular from lkV to 3.6kV, is referred to as low voltage. For example, a range from 3kV to 72.5kV is referred to as medium voltage (MV), in particular lager than 3.6 kV. For example, current rating is from 100 A to 10000 A.
  • Figures 1, 3, 4 and 5 each show a horizontal section on the left-hand side along line A-A of the right-hand side, which shows part of a vertical section.
  • Figure 1 schematically shows an embodiment of the bushing 100 installed in a wall 201 of an electrical apparatus 200. The electrical apparatus 200, for example is a liquid insulated electrical apparatus like a transformer or a reactor. An insulating liquid 103 is arranged in a tank which is bounded by the wall 201.
  • The bushing 100 provides an electrical connection of the electrical apparatus 200 through the wall 201 from an outside to an inside. The wall 201 may be on earth potential or at least on an electrical potential that is potentially different from the potential of a conductor 101 of the bushing 100. An insulator body 110 of the bushing 100 provides an electrical insulation between the wall 201 and the electrical conductor 101. In particular, the bushing 100 comprises a rotationally symmetrical and/or mirror-symmetrical shape.
  • The insulator body 110 surrounds the electrical conductor 101. The electrical conductor 101 extends through the insulator body 110 along a longitudinal axis 102. The electrical conductor 101 extends elongated along the longitudinal axis 102. A part of the insulator body 110 is exposed to the air environment, typically outdoor environment, and another part of the insulator body 110 is immersed in the insulating liquid 103 of the apparatus 200.
  • The insulator body 110 comprises a main part 112. The main part 112 comprises a hollow cylinder shape 113, at least in a part. The main part 112 is coaxially arranged with the electrical conductor 101. For example, a center of the hollow cylinder shape 113 is the longitudinal axis 102.
  • The insulator body 110 comprises an inner side 114 which faces the electrical conductor 101. The inner side 114 extends along the longitudinal axis 102.
  • The insulator body comprises a plurality of projecting ribs 130. The projecting ribs 130 are arranged on the inner side 114 of the main part 112. In particular, the main part 112 and the projecting ribs 130 are formed as a single piece.
  • The projecting ribs 130 each comprise a main extension 131 which extends in a direction along the longitudinal axis 102.
  • The projecting ribs 130 extend elongated along the longitudinal axis 102.
  • The projecting ribs 130 each project radially towards the conductor 101 from the inner side 114. The projecting ribs 130 are radially arranged around the electrical conductor 101. The projecting ribs 130 radially extend from the inner side 114 towards the conductor 101, for example without directly touching the conductor 101.
  • The projecting ribs 130 reinforce the insulator body 110. As shown in Figure 2, different forces like a cantilever force 104, a compression force 105 and a further compression force 106 act on the bushing 100 and the insulator body 110. The projecting ribs 130 strengthen the insulator body 110 against deformation due to the forces 104, 105, 106. The design of the insulator body 110 with the projecting ribs 130 allows a thin wall structure of the insulator body 110 with a reduced wall thickness 124. For example, the wall thickness 124 comprises a value of 10 mm or less, for example 6 mm or less.
  • The insulator body 110 is made of thermoplastic material 115. The insulator body 110 with the hollow cylinder shape 113 and the projecting ribs 130 for example is manufactured by a single injection molding process.
  • The insulator body 110 comprises a flange 118 which radially projects outwards from outer side 129 of the main part 112. The outer side 129 is arranged radially opposite the inner side 114. The flange 118 is configured to provide a mounting of the bushing 100 to the wall 201. For example, a gasket 160 is arranged between the flange 118 and the wall 201 to provide a fluid-tight connection.
  • The projecting ribs 130 are arranged in an area of the flange 118. The projecting ribs 130 extend longitudinally over the flange 118. This allows a reliable transfer of the vertical compression force 105 along the main part 112 towards the flange 118. The extension of the projecting ribs 130 across the flange 118 reinforce the flange attachment to the main part 112 and limits a deflection of the flange 118. The flange 118 is connected to the main part 112 at a connection 119. The projecting ribs 130 extend over the connection 119 on the inner side 114.
  • In the embodiments of Figures 1 to 5, the main part 112 comprises an upper part 121 and a lower part 122. The lower part 122 comprises the hollow cylinder shape 113 and the projecting ribs 130 as well as the flange 118.
  • The upper part 121 is arranged on an end of the lower part 122 facing away from the wall 201 along the longitudinal axis 102.
  • The upper part 121 is inclined with respect to the longitudinal axis 102 and overlaps the lower part 122 in part. Thus, the upper part forms a weather shed and extends the creepage path along the outer side 129.
  • The upper part 121 is fixed to the conductor 101 by a holder 126. During manufacturing, the lower part 122 is arranged on the wall 201. A conductor seal 140 is arranged on the conductor 101 and pressed vertically along the longitudinal axis 102 against a seal seat 125 of the lower part 122 by the upper part 121. This compression force 105 is maintained by fixing the upper part 121 with the holder 126 at the conductor 101.
  • A gap 109 is arranged axially between the upper part 121 and the lower part 122. The transition between the upper part 121 and the lower part 122 is sealed via the conductor seal 140.
  • Inside the tank, the conductor 101 is supported via an insulating support 107 at the wall 201. The main part 112 extends elongated over the wall 201 towards the support 107 along the longitudinal axis 102. For example, the projecting ribs 130 extend over the wall 201 along the longitudinal axis 102. Thereby, the main part 112 is reinforced by the projecting ribs 130 also inside the tank of the electrical apparatus 200. This allows a better resistance against the cantilever force 104. An end 127 of the main part 112 facing away from the seal seat 125 along the longitudinal axis 102 protrudes over the projecting ribs 130 along the longitudinal axis 102. The length of this protrusion is large enough to prevent an electric flashover to happen in the insulating liquid 103 between the tank wall 201 and the conductor 101 of the bushing 100.
  • The flange ribs 130 enable a robust mechanical structure against flange deflection of the flange 118 under the cantilever force 104 and the compression forces 105, 106. The arrangement of the projecting ribs 130 on the inner side 114 of the main part 112 makes the outer side 129 smoother. Thereby a contamination collection is reduced.
  • Figure 3 shows an embodiment of the bushing 100 which corresponds to the embodiment of Figure 1. Additionally, flange ribs 170 are provided. The flange ribs 170 are arranged at the flange 118 to support the flange 118 against a bending and/or deformation. The flange ribs 170 are radially arranged between the outer side 129 and the flange 118 on a side of the flange 118 facing the wall 201. As shown in Figure 5, the flange ribs 170 can be elongated along the longitudinal axis 102 to provide a support and fixation for the gasket 160. For example, at least some of the flange ribs 170 are elongated to hold the gasket 160 in an unmounted state, such that a detachment of the gasket 160 from the flange 118 can be avoided.
  • The projecting ribs 130 and the flange ribs 117 are shown radially aligned. It is also possible to provide an offset arrangement of the flange ribs 170 and the projecting ribs 130.
  • The flange ribs 170 provide a robust mechanical structure against flange deflection under cantilever forces 104, and under compression forces 105, 106. The placement of the flange ribs 170 on the side of the flange 118 facing the wall 201 contributes to a smooth outer area of the flange 118, which helps to avoid contamination.
  • Figure 4 shows an embodiment of the bushing 100 which corresponds substantially to the embodiment of Figure 3. According to the embodiment of Figure 4, the insulator body 110 additionally comprises an inner part 117. The inner part 117 comprises a hollow cylinder shape and is coaxially arranged with the main part 112. The inner part 117 provides additional rigidity, in particular against the compression 105, 106. Further, the inner part 117 may constitute an additional barrier for electric insulation between the conductor 101 and the wall 201. The projecting ribs 130 radially extend between the main part 112 and the inner part 117.
  • The embodiment of Figure 4 shows the inner part 117 and the flange rib 170. According to a further embodiment, the inner part 117 is provided and the flange rib 170 is omitted.
  • Figure 5 shows an embodiment with elongated flange ribs 170 which serve as holders for the gasket 160, as already mentioned above. In the shown embodiment, four of the flange ribs 170 are elongated to hold the gasket 160. Of course, this number is just an exemplary number. It is possible to have less elongated flange ribs 170 as holders for the gasket 160 or more than four elongated flanges 170. The elongated flange ribs 170 keep the gasket 160 in place and centred during installation on the wall 201 and also during operation.
  • Figures 6 to 8 show embodiments of the bushing 100 with the main part realized in one single piece. The upper part 121, as for example shown in Figures 1 to 5, is replaced by a hood 128. The hood 128 is, for example, not made of thermoplastic material. The hood 128 for example comprises an electrically conductive material, for example metal. The conductor seal 140 is pressed between the hood 128 and the seal seat 125 of the main part 112. The hood 128 is fixed to the conductor 101.
  • The embodiments of Figures 6 to 8 in particular are applicable for medium voltage bushings 100. A longer creepage path is realized by the shape of the insulator body 110.
  • The main part 112 comprises weather sheds 116. The weather sheds extend the creepage path. For example, the weather sheds 116 are formed as integral parts of the main part 112. The main part 112, with the projecting ribs 130 and the weather sheds 116, is formed as one single piece.
  • Figures 6 to 8 exemplarily show two weather sheds 116. It is also possible to provide just one single weather shed 116 or more than two weather sheds 116, for example three or more.
  • The weather sheds 116 radially project outwards on the outer side 129 of the main body 112. The projecting ribs 130 and the weather sheds 116 are arranged radially opposite each other.
  • The insulator body 110 is fixed to the wall 201 by a flange clamp 111. The flange clamp 111 is a separate part which is fixed to the wall 201, for example by a screw connection and exerts a force on the flange 118.
  • According to embodiments, de-airing is incorporated in the conductor 101 to degas the inner volume of the bushing 100 when installed on the apparatus 200 and filled with insulating liquid 103. Alternatively, an additional metallic intermediate ring is arranged between the main part 112 and the hood 128. The conductor seal 140 is compressed between this ring and the hood 128. De-airing is provided in the ring in this embodiment.
  • The electrical conductor 101 extends only partly along the main part 112. An electrically conductive conductor extension 108 is electrically and mechanically connected with the conductor 101 and extends further longitudinally across the wall 201. It is possible that a longer electrical conductor 101 which extends further across the wall 201 is provided and the conductor extension 108 is omitted. For example, the conductor 101 extends through the whole axial length of the main part 112.
  • The main part 112 extends axially across the wall 201 to provide an electrical insulation inside the tank in the liquid 103. In particular, the end 127 of the main part 112 extends longer into the tank in the medium voltage bushings than in the low voltage bushings according to Figures 1 to 5.
  • Figure 7 shows an embodiment of the bushing 100 with a different mounting of the bushing 100 to the wall 201 than shown in Figures 6 and 8.
  • The flange 118 comprises an opening 120 through which a mounting element 123 extends. Thus, the additional flange clamp 111 can be omitted. The mounting interface is integrated in the flange 118. Thus, the main part 112 made out of the thermoplastic material provides the mounting interface for fixing the bushing 100 to the wall 201.
  • The main body 111 comprises additional flange ribs 170. The additional flange ribs 170 are arranged to provide additional mechanical reinforcement to the flange 118. The flange 118 with the opening 120 which serves as a mounting interface incorporates the mounting interface in the thin wall thermoplastic structure of the main part 112. The additional flange ribs 170 and the mounting interface of the flange 118 are located in an area that is shielded from exposure to electric fields by a suitable shielding structure (not explicitly shown). Thus, if contamination gets collected in the area of the opening 120, it does not have a negative influence on the insulation properties of the insulator body 110.
  • For example, the opening 120 and/or the flange ribs 170 are positioned in an area screened from electric field stress by appropriate shielding structure (not explicitly shown), so that, in case contamination gets collected in that area, it does not have negative influence on the insulation properties of the insulator body 110.
  • The main body 112 with the integrated mounting feature on the outer flange 118 has less components by avoiding the flange clamp 111 and a robust mechanic structure.
  • Figure 8 shows an embodiment with the main part 112 according to Figure 6 with additional corrugations 134 on the main part 112 inside the tank in the liquid 103. In addition, further projecting ribs 133 are arranged on the inner part 117 which is provided corresponding to the inner part 117 as shown in Figure 4.
  • The further projecting ribs 133 project radially inward towards the conductor 100 from the inner part 117. The further projecting ribs 133 are elongated along the longitudinal axis 102 like the projecting ribs 130.
  • The further projecting ribs 133 and the inner part 117 provide more mechanical resistance against cantilever forces 104, even with a larger longitudinal length of the insulator body 110. Furthermore, a second barrier for electric insulation between the conductor 101 and the tank wall 201 is provided.
  • The inner part 117 is shorter along the longitudinal axis 102 than the main part 112. In particular, the further projecting ribs 133 and the projecting ribs 130 are shorter than the inner part 117 and the man part 112. Thus, a long creepage length in the liquid 103 is provided for a reliable electric insulation.
  • The corrugations 134 are formed to further extend the creepage length in the insulating liquid 103.
  • Figures 9 and 10 show embodiments of the bushing 100 with an additional outer cover 150. The outer cover 150 can be combined with the embodiments of Figures 1 to 5, according to which the main part 112 comprises a plurality of separate parts, as shown in Figure 9. The outer cover 150 can also be provided at the other embodiments as shown in Figures 6 to 8, according to which the main part 112 is provided by one single piece. This is exemplarily shown in Figure 10.
  • The outer cover 150 comprises an elastomeric material 151 or consists of the elastomeric material 151. For example, the elastomeric material 151 is silicone rubber which provides a hydrophobic surface.
  • The elastomeric material 151 is chemically bonded to the thermoplastic material 115 of the main part 112. The chemical bond provides a cohesive connection between the elastomeric material 151 of the cover 150 and the thermoplastic material 115 of the main part 112. In particular, the connection cannot be detached non-destructively.
  • The elastomeric material 151 and the outer cover 150 provides a hydrophobicity recovery and hydrophobicity transfer properties, which make the hydrophobic nature of its surface persist during most of the time of operation of the bushing, also in polluted environments, thus minimizing leakage currents running along the surface of the main part 112 in wet conditions. Thus, the probability of a surface discharge and/or electrical breakdown is reduced by the cover 150. The process of hydrophobicity recovery, after an event rendering the silicone rubber surface less hydrophobic or even hydrophilic, such as activity of plasma generated by neighboring electric arc or an extreme rainfall of long duration, is described, for example, in D. Bodas and C. Khan-Malek, Sens. Actuators B: Chem. vol. 123, p. 368 (2007). The process of hydrophobicity transfer, i.e., transferring the hydrophobic properties of the silicone rubber onto the pollution layers accumulating on its surface during service of the insulator, is described, for example, in A. Hergert, et al., IEEE Trans. Dielectr. Electr. Insul., vol. 24, no. 2, p. 1057 (2017).
  • The elastomeric material 151 for example is one of moldable or extrudable liquid silicone rubber, high consistency rubber, and high temperature vulcanization silicone rubber. For example, the curable elastomeric material 151 is applied in liquid form and then hardens to form the cover 150.
  • Self-adhesive silicone rubber can be used to produce the outer cover 150. Without being bound to it, examples for self-adhesive silicone rubber are described in EP 0 497 349 , US 4,742,103 , EP 0 493 791 A1 , EP 0 497 349 B1 , US 5,595,826 , EP 0 875 536 B1 , US 6,743,515 B1 , US 2003/0236380 A1 , and US 2005/0089696A1 , the contents of which are hereby incorporated by reference. Other examples include SILASTIC™ SA 9940 compositions from Dow Chemical Company, Silopren™ LSR 2740 from Momentive Performance Materials Inc., or ELASTOSIL® LR 3070 grades from Wacker Chemie AG. The self-adhesive silicone rubber contains chemical coupling agents to form the chemical bond between the outer side 129 of the thermoplastic material 115 of the main part 112 and the solidified silicone rubber. In particular, silane-based agents chemically reactive both with the surface of the thermoplastic material 115 and with the other components of the elastomeric material 151, in particular the silicone rubber mixture and/or other constituents of the curable elastomer composition forming the elastomeric material, in particular the curable silicone elastomer composition, are provided to establish the chemical bond.
  • As shown in Figure 9, the upper part 121 is covered by the outer cover 150 on an outward-facing side as well as on a an inward-facing side facing the conductor 101. The lower part 122 is covered by the outer cover 150 on the outer side 129. The cover is arranged such that, for example, all surfaces of the main part 121 exposed to the environment, in particular the air environment, are covered by the cover 150.
  • The cover 150 in particular comprises in most parts the same thickness 182 perpendicular to the surface of the upper part 121 and the lower part 122 within normal tolerances of for example 50. For example, the thickness is constant and the same in most of the cover 150, for example in more than 750, more than 80%, more than 90% or more than 950 of the cover 150. For example, a thickness 182 of the cover 150 transverse to outer site 129 of the main part 112 is between 0.5 mm and 5 mm. The thickness may be different in the corners, for example at the connection 119, or at the ends of the cover 150.
  • Figure 10 shows the outer cover 150 which forms weather sheds 152. The weather sheds 152 are made out of the elastomeric material 151. The outer cover 150 covers the outer side 129 of the main part 112 and additionally provides the weather sheds 152. Two weather sheds 152 are shown in Figure 10. It is also possible that only one single weather shed 152 is formed out of the elastomeric material 151 or more than two weather sheds 152 are formed out of the elastomeric material 151, for example three or more weather sheds 152. The weather sheds 152 provide an elongated creepage length. The thin wall thermoplastic main part 112 can be used and additionally the weather sheds 152 can be easily provided.
  • The different features of the different embodiments according to Figures 1 to 10 can be combined with each other in any combination. For example, the outer cover 150 can be provided at any of the embodiments according to Figures 1 to 8. Every feature described with respect to one of the embodiments is also disclosed herein with respect to the other embodiments, even if the respective feature is not explicitly mentioned in the context of the specific embodiment. For example, the bushing 100 according to this disclosure comprises at least one or more of the following in any combination: the inner part 117 attached to the inner edges of the ribs 130 for adding more withstand to the vertical compression forces 105, one or mor weather sheds 116, 152 attached to the air-end of the main part 112 of the insulator body 110 for providing electric insulation between the conductor 108 and the tank wall 201, flange mounting features integrated in the thin-wall structure of the main part 112 like the opening 120, corrugations 134 on the oil-end of the main part 112 to increase the creepage length of the oil end of the bushing 100, oil-end extension of the inner part 117 for providing additional insulation on the oil end, extensions of the flange ribs 170 forming gasket holders to precisely center the gasket 160 and to hold it together with the insulator body 110 when assembling the bushing 100 on the apparatus 200, and the cover 150 molded out of silicone rubber on the air end of the main part 112 with hydrophobic surface and chemically bonded to the main part 112.
  • The bushing 100 with the projecting ribs 130 provides a reliable reinforcement against deflection. A short manufacturing process time and low material consumption is possible. The projecting ribs 130 provide a robust mechanical structure, in particular against the compression forces 105, 106 and the cantilever force 104 both at elastic loads (short time) and against creep (long time). Thus, a reliable bushing 100 is provided.
    • Reference Signs
    • 100
    bushing
    101
    electrical conductor
    102
    longitudinal axis
    103
    liquid
    104
    cantilever force
    105
    compression force
    106
    further compression force
    107
    support
    108
    conductor extension
    109
    gap
    110
    insulator body
    111
    flange clamp
    112
    main part
    113
    hollow cylinder shape
    114
    inner side
    115
    thermoplastic material
    116
    weather shed
    117
    inner part
    118
    outer flange
    119
    connection
    120
    opening
    121
    upper part
    122
    lower part
    123
    mounting element
    124
    wall thickness
    125
    seal seat
    126
    holder
    127
    end
    128
    hood
    129
    outer side
    130
    projecting rib
    131
    main extension
    132
    rib thickness
    133
    further projecting rib
    134
    corrugation
    140
    conductor seal
    150
    outer cover
    151
    elastomeric material
    152
    weather shed
    160
    gasket
    170
    flange rib
    182
    cover thickness
    200
    electrical apparatus
    201
    wall

Claims (15)

  1. A bushing (100) for a liquid-insulated electrical apparatus (200), the bushing (100) comprising 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 part (112) and wherein the projecting ribs (130) comprise a main extension (131) along a longitudinal axis (102) of the conductor (101).
  2. The bushing of claim 1, wherein the main part (112) is formed in one piece.
  3. The bushing of claim 1, wherein the main part (112) comprises two or more separate parts (121, 122) stacked along the longitudinal axis (102).
  4. The bushing of any one of the preceding claims, wherein the main part (112) is made of thermoplastic (115).
  5. The bushing of any one of the preceding claims, comprising an outer cover, wherein the outer cover (150) is made of an elastomeric material (151) and covers the main part (112) at least party, in particular comprising a weather shed (152), the weather shed (152) being an integral part of the outer cover (150).
  6. The bushing of any one of the preceding claims, wherein the main part (112) comprises an inner part (117) which comprises a hollow cylinder shape, wherein the main part (112) and the inner part (117) are arranged coaxially, and the inner part (117) comprises a smaller diameter than the main part.
  7. The bushing of any one of the preceding claims, wherein the main part (112) comprises an outer flange (118) that projects radially outwards from the main part (112), wherein the outer flange (118) is an integral part of the main part (112) .
  8. The bushing of claim 7, wherein a plurality of flange ribs (170) is arranged between the outer flange (118) and the main part (112), wherein the flange ribs (170) project radially outwards from the main part (112).
  9. The bushing of claim 8, wherein at least a part of the flange ribs (170) is configured to hold a gasket (160).
  10. The bushing of any one of claims 7 to 9, wherein the projecting ribs (130) extend axially across a connection (119) between the main part (112) and the outer flange (118).
  11. The bushing of any one of claims 7 to 10, wherein the outer flange (118) comprises an opening (120) through which an elongated mounting element (123) can protrude to fix the main part (112) to the electrical apparatus (200).
  12. The bushing of any one of claims 7 to 11, wherein the main part (112) extends axially below the outer flange (118).
  13. The bushing of any one of the preceding claims, wherein the projecting ribs (130) each comprises a rib thickness (132) transverse to the direction of projection of 0.5 mm to 10 mm, in particular the projecting ribs (130) each comprises a rib thickness (132) transverse to the direction of projection and the main part (112) comprises a wall thickness (124) along the radial direction, wherein the rib thickness (132) is between 25% and 100% of the wall thickness (124).
  14. A liquid-insulated electrical apparatus (200) comprising the bushing (100) according to any one of the preceding claims and a wall (201) in which the bushing (100) is installed.
  15. The apparatus of claim 14, wherein the projecting ribs (130) extend axially across the wall (201).
EP24166820.1A 2024-03-27 2024-03-27 Bushing and electrical apparatus Pending EP4625446A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP24166820.1A EP4625446A1 (en) 2024-03-27 2024-03-27 Bushing and electrical apparatus
PCT/EP2025/055185 WO2025201785A1 (en) 2024-03-27 2025-02-26 Bushing and electrical apparatus

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP24166820.1A EP4625446A1 (en) 2024-03-27 2024-03-27 Bushing and electrical apparatus

Publications (1)

Publication Number Publication Date
EP4625446A1 true EP4625446A1 (en) 2025-10-01

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Family Applications (1)

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EP (1) EP4625446A1 (en)
WO (1) WO2025201785A1 (en)

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