EP2942787A1 - Electrical bushing - Google Patents
Electrical bushing Download PDFInfo
- Publication number
- EP2942787A1 EP2942787A1 EP14188027.8A EP14188027A EP2942787A1 EP 2942787 A1 EP2942787 A1 EP 2942787A1 EP 14188027 A EP14188027 A EP 14188027A EP 2942787 A1 EP2942787 A1 EP 2942787A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- heat
- bushing
- pipe
- conductor
- central
- 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.)
- Withdrawn
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Classifications
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- 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
- H01B17/54—Insulators or insulating bodies characterised by their form having heating or cooling devices
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D15/00—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies
- F28D15/02—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/02—Casings
- H01F27/04—Leading of conductors or axles through casings, e.g. for tap-changing arrangements
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D21/00—Heat-exchange apparatus not covered by any of the groups F28D1/00 - F28D20/00
- F28D2021/0019—Other heat exchangers for particular applications; Heat exchange systems not otherwise provided for
- F28D2021/0028—Other heat exchangers for particular applications; Heat exchange systems not otherwise provided for for cooling heat generating elements, e.g. for cooling electronic components or electric devices
- F28D2021/0029—Heat sinks
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- 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
Definitions
- the present disclosure relates to an electrical bushing comprising a heat-pipe.
- a bushing is a hollow electrical insulator through which a conductor may pass.
- Bushings are used where high voltage lines must pass through a wall or other surface, on switchgear, transformers, circuit breakers and other high voltage equipment.
- a bushing is e.g. used for passing a high voltage line from an oil-filled transformer, whereby the bushing is an oil-to-air bushing with a part in oil in the transformer and a part in air outside of the transformer.
- Other bushings are air-to-air bushings e.g. passing high voltage lines through a wall.
- Resistive heat losses in a bushing arise evenly along the conductor.
- the heat is primarily dissipated to the environment at the upper and lower ends of the bushing.
- the heat is transported from the central part to the ends by conduction and sometimes by convection. Even though it is rarely used, it is also known that the heat can be transported by an evaporating medium, a so called heat pipe.
- a thicker conductive rod can be used to reduce the current density and thereby reduce the heat generated.
- a thicker rod leads to increased material consumption and cost.
- a heat pipe is a heat-transfer device that combines the principles of both thermal conductivity and phase transition to efficiently manage the transfer of heat between a hot interface and a cooler interface.
- the function of a heat pipe is to evaporate a liquid at the hot interface of the pipe and to condense it at the cooler interface where the heat is to be dissipated.
- a given bushing with a defined central space for a conductor has different current carrying capacity due to heat generation depending on what size conductor it is provided with.
- a flexible conductor gives comparatively low current carrying capacity and a solid rod or tube conductor gives higher capacity.
- copper conductors give higher capacity than aluminium.
- the same basic bushing can be given various current ratings depending on which conductor it is equipped with. If the bushing is provided with a heat-pipe, the rating can also be increased.
- a bushing can handle a higher current, without the need to use a larger conductor, if the conductor is equipped with a heat-pipe.
- a heat-pipe renders the bushing more expensive to produce and may not be needed for regular bushings. Instead, special bushings with heat pipes are produced especially for applications where such improved heat transfer is needed.
- CN 101369483 discloses a heat pipe bushing for transformers, comprising a conductive pipe, a radiator, a main insulating layer, an insulating sleeve and a connecting bushing.
- the conductive pipe is a hollow metal pipe that is connected to the radiator at one end and filled with environmentally-friendly, non-combustible cooling liquid.
- the exterior of the conductive pipe is wrapped with the main insulating layer, and the insulating sleeve and the connecting flange are installed on the exterior of the main insulating layer.
- the radiator is a hollow metal cavity whose internal cavity is connected to hollow cavity of the conductive pipe.
- the cooling liquid absorbs the heat generated by the conductive pipe and evaporates into gas, which rises to the radiator for external heat discharge; following this, it is condensed upon cooling and reflows to the conductive pipe.
- WO 2007/107119 discloses a current carrier combined with heat-pipe which comprises a fluid with low boiling point.
- the current carrier can be used for the bushing of electrical equipment, the primary winding of a current transformer, a great current bus and so on.
- EP 2 704 157 discloses an electrical insulator bushing wherein the conductor comprises a cavity extending longitudinally along the conductor and having an opening at one end.
- the cavity is arranged for accommodating a heat-pipe.
- the cavity is arranged for allowing the heat-pipe to be introduced into and removed from said cavity via its opening.
- an electrical bushing comprising an electrically insulating sleeve having a central longitudinal through hole surrounding a central longitudinal axis of the bushing.
- the bushing also comprises a tubular electrical conductor positioned through the central longitudinal through hole of the sleeve and defining a central longitudinal cavity around and along the longitudinal axis inside the tubular conductor.
- the bushing comprises at least one heat-pipe comprising a heat transfer fluid enclosed in a heat conducting pipe for transferring heat along the bushing.
- the heat-pipe is longitudinally arranged and positioned in the central longitudinal cavity.
- an electrical device comprising an embodiment of the bushing of the present disclosure.
- the need to redesign the bushing to allow the presence of one or more heat-pipes is reduced or eliminated.
- the central longitudinal space is utilized in accordance with the present invention.
- the bushing of the present invention may be used for a transformer, as exemplified herein, but the inventive bushing may alternatively be used for other electrical devices, especially fluid-filled (e.g. oil) electrical devices, such as electrical motors or switches.
- fluid-filled electrical devices such as electrical motors or switches.
- FIG. 1 is a schematic illustration of a transformer 8 where a bushing 1 is used for conducting an electrical current (I, U) through the casing of the transformer 8.
- the transformer may be an oil-filled transformer, e.g. filled with mineral oil or an ester-based oil.
- the transformer may be a high-voltage power transformer, whereby a high-voltage current is passed from the transformer through the conductor of the bushing 1.
- the bushing 1 may thus have an inner oil-immersed part at a lower end of the bushing inside the transformer 8, and an outer part in air at an upper end of the bushing outside of the transformer, or the outer part may also be fluid-filled.
- the bushing by means of its conductor, may conduct current from e.g. a winding of the transformer, through the casing of the transformer and to e.g. an air-borne line of a power distribution network, the bushing 1 insulating the current from the casing and any other external structures.
- FIG. 2 schematically illustrates an embodiment of a bushing 1 of the present invention.
- the bushing 1 is schematically shown in a longitudinal section along the central longitudinal axis 5 of the bushing.
- the bushing 1 of figure 1 is a tubular or essentially cylindrical device wherein a electrically insulating sleeve 2 forms an envelope surface surrounding the bushing in its longitudinal direction in parallel with the longitudinal axis 5.
- the sleeve insulates a tube/pipe formed electrical conductor 3 from external structures, such as a wall through which the bushing is to be arranged.
- the conductor 3 is arranged within and through a longitudinal central through hole 4 of the sleeve, through which hole 4 also the central longitudinal axis 5 runs.
- any concentric tubular space formed between the sleeve 2 and the conductor pipe 3 may comprise a capacitor core and/or be filled with e.g. oil, gas or vacuum.
- the conductor 3 is configured to conduct an electrical current (AC or DC) through the bushing 1 (in the figure this is schematically illustrated by a current (I, U) entering at the lower end of the bushing and exiting at the upper end of said bushing, but the opposite direction, or an alternating current is of course also possible).
- the conductor 3 is in the form of a hollow tube or cylinder, forming a central space or cavity 9 through which the central longitudinal axis 5 passes.
- This central space 9 can be used for different things, such as a draw rod or the like, and/or for accommodating longitudinal heat-pipe(s) 6 in accordance with the present invention for transporting heat from within the bushing out towards at least one of the ends of the bushing.
- a draw rod or the like there may positioned at least one, typically eccentrically located, heat-pipe 6 extending longitudinally along the conductor 3.
- the heat-pipe 6 illustrated in the figure comprises a heat-conducting pipe 10, and a condenser 7 extending outside of the bushing 1.
- the heat-pipe 6 of the embodiment of figure 2 is eccentrically located and does not intersect the central longitudinal axis 5 to not interfere with e.g. a draw rod used.
- the heat pipe 6 comprises one or more condenser(s) 7, but in other embodiments no dedicated condenser is used (the fluid condensing in a cooler part of the pipe 10).
- the heat-pipe 6 may be any type of heat-pipe.
- the heat-pipe may, as illustrated in the figures herein, use gravity induced return of the condensed heat transfer fluid, or a wick may be used to return the condensed fluid (e.g. if the heat-pipe/bushing is not vertically enough positioned for gravity return to be effective).
- the heat-pipe 6 may be a loop heat-pipe (also called a thermo siphon).
- each condenser 7 is comprised exclusively in one heat pipe, but it is also contemplated that a condenser 7 may be comprised in a plurality of heat pipes (heat-pipes 6 sharing the same condenser 7).
- the condenser 7 is conveniently positioned at the end of the bushing 1 intended to be an upper end of the bushing when in use.
- it may be convenient to arrange condensers 7 at both ends of the bushing e.g. allowing a heat pipe 6 to be connected to a condenser 7 at each end of the bushing 1, or allowing one heat pipe 6 to be connected to a condenser at an end of the bushing and another heat pipe to be connected to a condenser at another (opposite) end of said bushing.
- the conductor 3 is configured for conducting electrical current through the bushing 1.
- the conductor is made of an electrically conducting material, e.g. a metal such as copper.
- the conductor 3 conveniently comprises an electrically conducting tube since the skin effect results in the current only travelling at the surface of a conductor whereby a tube can be used to save conducting material as well as accommodating heat-pipes 6 in accordance with the present invention.
- the sleeve 2 is made of an electrically insulating material, e.g. rubber such as silicon rubber, plastic, glass or a ceramic such as porcelain, or combinations thereof.
- the function of the sleeve 2 is to insulate the conductor 3 from e.g. a wall (e.g. a casing of a power transformer as in figure 1 ) which the bushing 1 is intended to pass through.
- the sleeve may comprise an insulating capacitor core which may be formed by an insulating material or material combination e.g. including plastics, paper, oil etc.
- Such a condenser core may extend along and in parallel with the cavity 9 (or the heat-pipe 6 therein) at least partly, where other parts of the longitudinal extension of the cavity (or the heat-pipe formed therein) may be covered/insulated by another medium e.g. a gas.
- the sleeve 2 has a longitudinal through hole or opening 4 along the central longitudinal axis 5 of the bushing 1, the sleeve thus surrounding but not intersecting said central longitudinal axis 5 of the bushing.
- the bushing 1 of the present invention may be beneficial in both direct current (DC) and alternating current (AC) applications.
- the one or more heat-pipes 6 arranged in the central cavity 9 in the tube conductor 3 may conveniently be detachable, as mentioned herein, to improve the range of the power rating of the bushing by allowing adjustment of the number of heat-pipes used, and to reduce the cost and complexity of producing the conductor 3 since it may not need to be custom made with heat-pipes.
- the heat-pipes may be detachable one by one, but it may be more convenient if the heat-pipes are connected to each other and detachable together as a cassette/unit. However, in some embodiments, the heat-pipes may be non-detachable and formed with or permanently attached to the tube conductor 3.
- the heat pipes are not formed within the conductor 3 but are distinct therefrom within the central cavity 9, typically at and along the inner surface of the conductor tube 3. More than one heat-pipe 6 may conveniently be used, in order to cool the conductor 3 around its circumference, e.g. between 4 and 12 heat-pipes equally distributed around the circumference of the conductor tube 3.
- the size of the heat-pipes may vary greatly depending on the application.
- the heat-pipes extend essentially along the whole bushing 1 and have an inner diameter which is large enough to allow liquid heat transfer fluid to circulate in the opposite direction of the gaseous fluid in the heat-pipe 6, while still being small enough to fit inside the central space 9.
- each heat-pipe may have an inner diameter of between 10 and 50 mm, and a length of between 1 and 20 m.
- the bushing 1 also comprises comprising a heat conducting condenser 7 (i.e. a condenser made from a heat conducting material) which is part of the heat-pipe 6 and typically extends outside of the cavity 9.
- a heat conducting condenser 7 i.e. a condenser made from a heat conducting material
- the heat transfer fluid may thus vaporize down inside the cavity 9 where the conductor 3 may have a hot spot, and rise to the condenser 7 where it can be cooled and condensed, dissipating the heat, more efficiently than if the heat heat-pipe 6 was completely contained in the central space 9 of the conductor.
- a condenser 7 may not be needed and in those embodiments the heat pipe 6 can be used for transporting heat from a hot spot of the conductor 3 to a cooler part of the bushing 1 (e.g. still inside the central space 9 in the conductor 3).
- the heat-pipe 6 is eccentrically located inside the conductor 3 such that the heat-pipe 6 does not intersect the central longitudinal axis 5 of the bushing 1. It may be an advantage to use an eccentrically located heat-pipe in a bushing since this allows the central part of the central space 9 of the tube-formed conductor 3 (the space along the central longitudinal axis of the bushing) to be free for other uses.
- An example of a convenient use of the central space includes a centric draw rod arranged for connecting an electricity line/cable to an end of the bushing conductor 3 at a first end of the bushing from the side of the opposite second end of the bushing.
- a heat pipe 6 is an efficient way of cooling a bushing by transferring heat formed by resistance within the bushing 1, from the bushing to an ambient medium or to another part (typically cooler part) of the bushing 1. That the heat-pipe 6 is eccentric means that it is not positioned in or at the central longitudinal axis 5 of the bushing. Thus, the heat-pipe 6 does not intersect the central longitudinal axis 5 of the bushing.
- the heat-pipe 6 extends longitudinally along at least a part of the longitudinal extension of the bushing 1, such that the heat pipe can transfer heat from one longitudinal position where it is desired to lower the temperature (typically an inner position of the bushing) to another longitudinal position (typically an outer position of the bushing, possibly even beyond an end of the sleeve 2 since the sleeve also insulates heat).
- a problem with using the whole hollow cavity 9 of the conductor pipe 3 as a heat pipe is that this cavity 9 then cannot be used for other parts of, or associated with, the bushing 1.
- This central cavity 9 is often needed for other purposes, e.g. to arrange a draw rod which holds a bottom contact connected to the bushing end, electrically connecting the winding of the transformer with the bushing conductor.
- distinct (and possibly detachable) heat-pipes positioned in the central space 9, in accordance with the present invention are advantageous.
- Figure 3 schematically illustrates an embodiment of a conductor 3.
- the conductor is shown in a cross-section perpendicular to the longitudinal axis 5.
- the conductor 3 is a pipe of an electrically conducting material having a longitudinal central cavity/space, e.g. a through hole, 9.
- a longitudinal cavity 9 of the conductor tube 3 a plurality of longitudinally arranged heat-pipes 6 are positioned.
- the bushing may be configured for accommodating any number of heat-pipes, according to different embodiments of the present invention.
- the central cavity 9 is typically at least partly liquid-filled, e.g. with a conventional transformer oil, and the heat-pipe 6 may be at least partly immersed in said liquid.
- the heat-pipes 6 may thus cool the conductor 3 by heat transfer via the liquid in the central cavity 9. Additionally, if a heat-pipe 6 is positioned in direct contact with the inside surface of the conductor tube 3, at least some of the cooling may be done also by direct heat transfer via the heat conducting pipe 10 of the heat-pipe 6 and the conductor tube 3.
- the number of heat-pipes 6 may vary greatly depending on design of the bushing/conductor and the need for heat exchange. Here, four heat-pipes 6 are shown as an example. Each of the heat-pipes 6 may be detachable, allowing the number of heat-pipes used to be adjusted in view of the cooling need of the bushing.
- the heat-pipes 6 may conveniently be essentially equidistantly distributed along the circumference of the conductor tube 3, along the inner wall of said tube 3, in order to achieve heat exchange relatively evenly around the conductor 3.
- Figure 4 illustrates an embodiment of a detachable heat pipe 6 configured for being inserted and/or withdrawn from the central through hole 9 of the pipe-formed conductor 3.
- a heat conducting pipe 10 forms a closed system enclosing the heat transfer fluid 11 therein.
- Figure 5 illustrates another embodiment of a detachable heat pipe configured for being inserted and/or withdrawn from the central through hole 9 of the pipe-formed conductor 3.
- a heat conducting pipe 10 forms a closed system together with a condenser 7, enclosing the heat transfer fluid 11 therein.
- the heat transfer fluid 11 may be any suitable fluid which has a boiling point at a desired operating temperature of the electrical conductor 3.
- the fluid may e.g. be water, an alcohol, a fluorinated alcohol or a fluorocarbon.
- the at least one heat-pipe 6 is detachable.
- the power-rating of the bushing may thus be changed, as discussed herein, and the heat-pipe may more easily be serviced or exchanged as needed.
- the at least one heat-pipe 6 is eccentrically positioned in the central cavity 9 such that it does not intersect the central axis 5.
- the central space may be used for other purposes, as discussed herein, without the heat-pipe being in the way.
- the at least one heat-pipe 6 is in direct longitudinal contact with the conductor 3, whereby the heat transfer between the heat-pipe and the conductor 3 may be improved.
- the central cavity 9 is at least partly liquid-filled such that the at least one heat-pipe 6 is at least partly immersed in said liquid. This may improve the heat transfer in the conductor 3 as well as the heat transfer between the heat-pipe and the conductor 3.
- the heat-pipe 6 comprises a condenser 7 extending beyond the sleeve 2.
- the heat-pipe may extend at one (typically upper) end, beyond (above) the sleeve 2, and typically also beyond the conductor 3, in order to more easily cool down and condense the heat transfer fluid away from the heat insulating effect of the sleeve 2.
- the condenser 7 may be formed inside the central space 9 in a cooler part of the bushing 1.
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Abstract
The present disclosure relates to an electrical bushing 1. The bushing comprises an electrically insulating sleeve 2 having a central longitudinal through hole 4 surrounding a central longitudinal axis 5 of the bushing. The bushing also comprises a tubular electrical conductor 3 positioned through the central longitudinal through hole of the sleeve and defining a central longitudinal cavity 9 around and along the longitudinal axis inside the tubular conductor. Also, the bushing comprises at least one heat-pipe 6 comprising a heat transfer fluid enclosed in a heat conducting pipe 10 for transferring heat along the bushing. The heat-pipe is longitudinally arranged and positioned in the central longitudinal cavity.
Description
- The present disclosure relates to an electrical bushing comprising a heat-pipe.
- A bushing is a hollow electrical insulator through which a conductor may pass. Bushings are used where high voltage lines must pass through a wall or other surface, on switchgear, transformers, circuit breakers and other high voltage equipment. A bushing is e.g. used for passing a high voltage line from an oil-filled transformer, whereby the bushing is an oil-to-air bushing with a part in oil in the transformer and a part in air outside of the transformer. Other bushings are air-to-air bushings e.g. passing high voltage lines through a wall.
- Resistive heat losses in a bushing arise evenly along the conductor. The heat is primarily dissipated to the environment at the upper and lower ends of the bushing. The heat is transported from the central part to the ends by conduction and sometimes by convection. Even though it is rarely used, it is also known that the heat can be transported by an evaporating medium, a so called heat pipe. In order to prevent high temperature rise of the conductive rod, a thicker conductive rod can be used to reduce the current density and thereby reduce the heat generated. However a thicker rod leads to increased material consumption and cost.
- A heat pipe is a heat-transfer device that combines the principles of both thermal conductivity and phase transition to efficiently manage the transfer of heat between a hot interface and a cooler interface. The function of a heat pipe is to evaporate a liquid at the hot interface of the pipe and to condense it at the cooler interface where the heat is to be dissipated.
- A given bushing with a defined central space for a conductor has different current carrying capacity due to heat generation depending on what size conductor it is provided with. Typically a flexible conductor gives comparatively low current carrying capacity and a solid rod or tube conductor gives higher capacity. In the same way copper conductors give higher capacity than aluminium. The same basic bushing can be given various current ratings depending on which conductor it is equipped with. If the bushing is provided with a heat-pipe, the rating can also be increased. Thus, a bushing can handle a higher current, without the need to use a larger conductor, if the conductor is equipped with a heat-pipe. However, a heat-pipe renders the bushing more expensive to produce and may not be needed for regular bushings. Instead, special bushings with heat pipes are produced especially for applications where such improved heat transfer is needed.
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CN 101369483 (application numberCN 2008 10115462.2 -
WO 2007/107119 discloses a current carrier combined with heat-pipe which comprises a fluid with low boiling point. The current carrier can be used for the bushing of electrical equipment, the primary winding of a current transformer, a great current bus and so on. -
EP 2 704 157 - It is an objective of the present invention to provide an improved electrical bushing comprising a heat-pipe for cooling the conductor in the bushing.
- According to an aspect of the present invention, there is provided an electrical bushing. The bushing comprises an electrically insulating sleeve having a central longitudinal through hole surrounding a central longitudinal axis of the bushing. The bushing also comprises a tubular electrical conductor positioned through the central longitudinal through hole of the sleeve and defining a central longitudinal cavity around and along the longitudinal axis inside the tubular conductor. Also, the bushing comprises at least one heat-pipe comprising a heat transfer fluid enclosed in a heat conducting pipe for transferring heat along the bushing. The heat-pipe is longitudinally arranged and positioned in the central longitudinal cavity.
- According to an aspect of the present invention, there is provided an electrical device comprising an embodiment of the bushing of the present disclosure.
- By positioning the heat-pipe in the central longitudinal space or cavity inside the tubular conductor, the need to redesign the bushing to allow the presence of one or more heat-pipes is reduced or eliminated. Thus, the central longitudinal space is utilized in accordance with the present invention.
- Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated. The use of "first", "second" etc. for different features/components of the present disclosure are only intended to distinguish the features/components from other similar features/components and not to impart any order or hierarchy to the features/components.
- Embodiments will be described, by way of example, with reference to the accompanying drawings, in which:
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Fig 1 is a schematic side view of a transformer with an embodiment of a bushing of the present invention. -
Fig 2 is a schematic longitudinal section of an embodiment of a bushing of the present invention. -
Fig 3 is a schematic cross-sectional view of an embodiment of a conductor in accordance with the present invention. -
Fig 4 is a schematic longitudinal section of an embodiment of a detachable heat pipe in accordance with the present invention. -
Fig 5 is a schematic longitudinal section of another embodiment of a detachable heat pipe in accordance with the present invention. - Embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments are shown. However, other embodiments in many different forms are possible within the scope of the present disclosure. Rather, the following embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like numbers refer to like elements throughout the description.
- The bushing of the present invention may be used for a transformer, as exemplified herein, but the inventive bushing may alternatively be used for other electrical devices, especially fluid-filled (e.g. oil) electrical devices, such as electrical motors or switches.
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Figure 1 is a schematic illustration of atransformer 8 where abushing 1 is used for conducting an electrical current (I, U) through the casing of thetransformer 8. The transformer may be an oil-filled transformer, e.g. filled with mineral oil or an ester-based oil. The transformer may be a high-voltage power transformer, whereby a high-voltage current is passed from the transformer through the conductor of thebushing 1. Thebushing 1 may thus have an inner oil-immersed part at a lower end of the bushing inside thetransformer 8, and an outer part in air at an upper end of the bushing outside of the transformer, or the outer part may also be fluid-filled. The bushing, by means of its conductor, may conduct current from e.g. a winding of the transformer, through the casing of the transformer and to e.g. an air-borne line of a power distribution network, thebushing 1 insulating the current from the casing and any other external structures. -
Figure 2 schematically illustrates an embodiment of abushing 1 of the present invention. Thebushing 1 is schematically shown in a longitudinal section along the centrallongitudinal axis 5 of the bushing. Thebushing 1 offigure 1 is a tubular or essentially cylindrical device wherein a electrically insulatingsleeve 2 forms an envelope surface surrounding the bushing in its longitudinal direction in parallel with thelongitudinal axis 5. The sleeve insulates a tube/pipe formedelectrical conductor 3 from external structures, such as a wall through which the bushing is to be arranged. Theconductor 3 is arranged within and through a longitudinal central throughhole 4 of the sleeve, through whichhole 4 also the centrallongitudinal axis 5 runs. Any concentric tubular space formed between thesleeve 2 and theconductor pipe 3 may comprise a capacitor core and/or be filled with e.g. oil, gas or vacuum. Theconductor 3 is configured to conduct an electrical current (AC or DC) through the bushing 1 (in the figure this is schematically illustrated by a current (I, U) entering at the lower end of the bushing and exiting at the upper end of said bushing, but the opposite direction, or an alternating current is of course also possible). In the embodiment of the figure, theconductor 3 is in the form of a hollow tube or cylinder, forming a central space orcavity 9 through which the centrallongitudinal axis 5 passes. Thiscentral space 9 can be used for different things, such as a draw rod or the like, and/or for accommodating longitudinal heat-pipe(s) 6 in accordance with the present invention for transporting heat from within the bushing out towards at least one of the ends of the bushing. Within thecentral space 9, there may positioned at least one, typically eccentrically located, heat-pipe 6 extending longitudinally along theconductor 3. The heat-pipe 6 illustrated in the figure comprises a heat-conductingpipe 10, and acondenser 7 extending outside of thebushing 1. The heat-pipe 6 of the embodiment offigure 2 is eccentrically located and does not intersect the centrallongitudinal axis 5 to not interfere with e.g. a draw rod used. In the embodiment of the figure, theheat pipe 6 comprises one or more condenser(s) 7, but in other embodiments no dedicated condenser is used (the fluid condensing in a cooler part of the pipe 10). The heat-pipe 6 may be any type of heat-pipe. The heat-pipe may, as illustrated in the figures herein, use gravity induced return of the condensed heat transfer fluid, or a wick may be used to return the condensed fluid (e.g. if the heat-pipe/bushing is not vertically enough positioned for gravity return to be effective). Also, the heat-pipe 6 may be a loop heat-pipe (also called a thermo siphon). There may be acondenser 7 at an end of thebushing 1, preferably extending longitudinally beyond thesleeve 2 in order to improve heat dissipation. If thecondenser 7 is positioned at an upper end of thebushing 7, condensed fluid may flow back into the cavity part of the heat pipe (to once again be evaporated) e.g. by act of gravity or a wick. In some embodiments, eachcondenser 7 is comprised exclusively in one heat pipe, but it is also contemplated that acondenser 7 may be comprised in a plurality of heat pipes (heat-pipes 6 sharing the same condenser 7). In view of gravity, as mentioned above, thecondenser 7 is conveniently positioned at the end of thebushing 1 intended to be an upper end of the bushing when in use. However, in some embodiments, it may be convenient to arrangecondensers 7 at both ends of the bushing, e.g. allowing aheat pipe 6 to be connected to acondenser 7 at each end of thebushing 1, or allowing oneheat pipe 6 to be connected to a condenser at an end of the bushing and another heat pipe to be connected to a condenser at another (opposite) end of said bushing. - The
conductor 3 is configured for conducting electrical current through thebushing 1. Thus, at least a part of the conductor is made of an electrically conducting material, e.g. a metal such as copper. In high-voltage applications, especially for alternating current (AC), theconductor 3 conveniently comprises an electrically conducting tube since the skin effect results in the current only travelling at the surface of a conductor whereby a tube can be used to save conducting material as well as accommodating heat-pipes 6 in accordance with the present invention. - The
sleeve 2 is made of an electrically insulating material, e.g. rubber such as silicon rubber, plastic, glass or a ceramic such as porcelain, or combinations thereof. The function of thesleeve 2 is to insulate theconductor 3 from e.g. a wall (e.g. a casing of a power transformer as infigure 1 ) which thebushing 1 is intended to pass through. In some embodiments, the sleeve may comprise an insulating capacitor core which may be formed by an insulating material or material combination e.g. including plastics, paper, oil etc. Such a condenser core may extend along and in parallel with the cavity 9 (or the heat-pipe 6 therein) at least partly, where other parts of the longitudinal extension of the cavity (or the heat-pipe formed therein) may be covered/insulated by another medium e.g. a gas. Thesleeve 2 has a longitudinal through hole oropening 4 along the centrallongitudinal axis 5 of thebushing 1, the sleeve thus surrounding but not intersecting said centrallongitudinal axis 5 of the bushing. - The
bushing 1 of the present invention may be beneficial in both direct current (DC) and alternating current (AC) applications. - The one or more heat-
pipes 6 arranged in thecentral cavity 9 in thetube conductor 3 may conveniently be detachable, as mentioned herein, to improve the range of the power rating of the bushing by allowing adjustment of the number of heat-pipes used, and to reduce the cost and complexity of producing theconductor 3 since it may not need to be custom made with heat-pipes. The heat-pipes may be detachable one by one, but it may be more convenient if the heat-pipes are connected to each other and detachable together as a cassette/unit. However, in some embodiments, the heat-pipes may be non-detachable and formed with or permanently attached to thetube conductor 3. However, it is noted that in accordance with the present invention, the heat pipes are not formed within theconductor 3 but are distinct therefrom within thecentral cavity 9, typically at and along the inner surface of theconductor tube 3. More than one heat-pipe 6 may conveniently be used, in order to cool theconductor 3 around its circumference, e.g. between 4 and 12 heat-pipes equally distributed around the circumference of theconductor tube 3. The size of the heat-pipes may vary greatly depending on the application. Typically, the heat-pipes extend essentially along thewhole bushing 1 and have an inner diameter which is large enough to allow liquid heat transfer fluid to circulate in the opposite direction of the gaseous fluid in the heat-pipe 6, while still being small enough to fit inside thecentral space 9. Thus, as an example, each heat-pipe may have an inner diameter of between 10 and 50 mm, and a length of between 1 and 20 m. - In some embodiments, the
bushing 1 also comprises comprising a heat conducting condenser 7 (i.e. a condenser made from a heat conducting material) which is part of the heat-pipe 6 and typically extends outside of thecavity 9. By using a condenser, the heat transfer from theconductor 3 to the outside of thebushing 1 may be improved. The heat transfer fluid may thus vaporize down inside thecavity 9 where theconductor 3 may have a hot spot, and rise to thecondenser 7 where it can be cooled and condensed, dissipating the heat, more efficiently than if the heat heat-pipe 6 was completely contained in thecentral space 9 of the conductor. It is noted, however, that in some embodiments, acondenser 7 may not be needed and in those embodiments theheat pipe 6 can be used for transporting heat from a hot spot of theconductor 3 to a cooler part of the bushing 1 (e.g. still inside thecentral space 9 in the conductor 3). - In some embodiments, the heat-
pipe 6 is eccentrically located inside theconductor 3 such that the heat-pipe 6 does not intersect the centrallongitudinal axis 5 of thebushing 1. It may be an advantage to use an eccentrically located heat-pipe in a bushing since this allows the central part of thecentral space 9 of the tube-formed conductor 3 (the space along the central longitudinal axis of the bushing) to be free for other uses. An example of a convenient use of the central space includes a centric draw rod arranged for connecting an electricity line/cable to an end of thebushing conductor 3 at a first end of the bushing from the side of the opposite second end of the bushing. To use aheat pipe 6 is an efficient way of cooling a bushing by transferring heat formed by resistance within thebushing 1, from the bushing to an ambient medium or to another part (typically cooler part) of thebushing 1. That the heat-pipe 6 is eccentric means that it is not positioned in or at the centrallongitudinal axis 5 of the bushing. Thus, the heat-pipe 6 does not intersect the centrallongitudinal axis 5 of the bushing. The heat-pipe 6 extends longitudinally along at least a part of the longitudinal extension of thebushing 1, such that the heat pipe can transfer heat from one longitudinal position where it is desired to lower the temperature (typically an inner position of the bushing) to another longitudinal position (typically an outer position of the bushing, possibly even beyond an end of thesleeve 2 since the sleeve also insulates heat). A problem with using the wholehollow cavity 9 of theconductor pipe 3 as a heat pipe is that thiscavity 9 then cannot be used for other parts of, or associated with, thebushing 1. Thiscentral cavity 9 is often needed for other purposes, e.g. to arrange a draw rod which holds a bottom contact connected to the bushing end, electrically connecting the winding of the transformer with the bushing conductor. Thus, distinct (and possibly detachable) heat-pipes positioned in thecentral space 9, in accordance with the present invention, are advantageous. -
Figure 3 schematically illustrates an embodiment of aconductor 3. The conductor is shown in a cross-section perpendicular to thelongitudinal axis 5. According to the embodiment offigure 3 , theconductor 3 is a pipe of an electrically conducting material having a longitudinal central cavity/space, e.g. a through hole, 9. In thelongitudinal cavity 9 of theconductor tube 3, a plurality of longitudinally arranged heat-pipes 6 are positioned. It should be noted that the bushing may be configured for accommodating any number of heat-pipes, according to different embodiments of the present invention. Thecentral cavity 9 is typically at least partly liquid-filled, e.g. with a conventional transformer oil, and the heat-pipe 6 may be at least partly immersed in said liquid. The heat-pipes 6 may thus cool theconductor 3 by heat transfer via the liquid in thecentral cavity 9. Additionally, if a heat-pipe 6 is positioned in direct contact with the inside surface of theconductor tube 3, at least some of the cooling may be done also by direct heat transfer via theheat conducting pipe 10 of the heat-pipe 6 and theconductor tube 3. The number of heat-pipes 6 may vary greatly depending on design of the bushing/conductor and the need for heat exchange. Here, four heat-pipes 6 are shown as an example. Each of the heat-pipes 6 may be detachable, allowing the number of heat-pipes used to be adjusted in view of the cooling need of the bushing. The heat-pipes 6 may conveniently be essentially equidistantly distributed along the circumference of theconductor tube 3, along the inner wall of saidtube 3, in order to achieve heat exchange relatively evenly around theconductor 3. -
Figure 4 illustrates an embodiment of adetachable heat pipe 6 configured for being inserted and/or withdrawn from the central throughhole 9 of the pipe-formedconductor 3. Aheat conducting pipe 10 forms a closed system enclosing theheat transfer fluid 11 therein. -
Figure 5 illustrates another embodiment of a detachable heat pipe configured for being inserted and/or withdrawn from the central throughhole 9 of the pipe-formedconductor 3. Aheat conducting pipe 10 forms a closed system together with acondenser 7, enclosing theheat transfer fluid 11 therein. - The
heat transfer fluid 11 may be any suitable fluid which has a boiling point at a desired operating temperature of theelectrical conductor 3. The fluid may e.g. be water, an alcohol, a fluorinated alcohol or a fluorocarbon. - In some embodiments of the present invention, the at least one heat-
pipe 6 is detachable. The power-rating of the bushing may thus be changed, as discussed herein, and the heat-pipe may more easily be serviced or exchanged as needed. - In some embodiments of the present invention, the at least one heat-
pipe 6 is eccentrically positioned in thecentral cavity 9 such that it does not intersect thecentral axis 5. Thus, the central space may be used for other purposes, as discussed herein, without the heat-pipe being in the way. - In some embodiments of the present invention, the at least one heat-
pipe 6 is in direct longitudinal contact with theconductor 3, whereby the heat transfer between the heat-pipe and theconductor 3 may be improved. - In some embodiments of the present invention, the
central cavity 9 is at least partly liquid-filled such that the at least one heat-pipe 6 is at least partly immersed in said liquid. This may improve the heat transfer in theconductor 3 as well as the heat transfer between the heat-pipe and theconductor 3. - In some embodiments of the present invention, the heat-
pipe 6 comprises acondenser 7 extending beyond thesleeve 2. Thus, the heat-pipe may extend at one (typically upper) end, beyond (above) thesleeve 2, and typically also beyond theconductor 3, in order to more easily cool down and condense the heat transfer fluid away from the heat insulating effect of thesleeve 2. Alternatively, thecondenser 7 may be formed inside thecentral space 9 in a cooler part of thebushing 1. - The present disclosure has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the present disclosure, as defined by the appended claims.
Claims (9)
- An electrical bushing (1) comprising:an electrically insulating sleeve (2) having a central longitudinal through hole (4) surrounding a central longitudinal axis (5) of the bushing;a tubular electrical conductor (3) positioned through the central longitudinal through hole (4) of the sleeve and defining a central longitudinal cavity (9) around and along the longitudinal axis (5) inside the tubular conductor; andat least one heat-pipe (6) comprising a heat transfer fluid (11) enclosed in a heat conducting pipe (10) for transferring heat along the bushing (1), being longitudinally arranged and positioned in the central longitudinal cavity (9).
- The bushing of claim 1, wherein the at least one heat-pipe (6) is detachable.
- The bushing of claim 1 or 2, wherein the at least one heat-pipe (6) is eccentrically positioned in the central cavity (9) such that it does not intersect the central axis (5).
- The bushing of any preceding claim, wherein the at least one heat-pipe (6) is in direct longitudinal contact with the conductor (3).
- The bushing of any preceding claim, wherein the central cavity (9) is at least partly liquid-filled such that the at least one heat-pipe (6) is at least partly immersed in said liquid.
- The bushing of any preceding claim, wherein the heat-pipe (6) comprises a condenser (7) extending beyond the sleeve (2).
- An electrical device (8) comprising the bushing (1) of any preceding claim.
- The electrical device of claim 7, wherein the electrical device is a power transformer.
- The electrical device of claim 7 or 8, wherein the electrical device is liquid-filled.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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EP14188027.8A EP2942787A1 (en) | 2014-10-08 | 2014-10-08 | Electrical bushing |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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EP14188027.8A EP2942787A1 (en) | 2014-10-08 | 2014-10-08 | Electrical bushing |
Publications (1)
Publication Number | Publication Date |
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EP2942787A1 true EP2942787A1 (en) | 2015-11-11 |
Family
ID=51660385
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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EP14188027.8A Withdrawn EP2942787A1 (en) | 2014-10-08 | 2014-10-08 | Electrical bushing |
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Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5178399U (en) * | 1974-12-18 | 1976-06-21 | ||
JPS528496A (en) * | 1975-07-09 | 1977-01-22 | Hitachi Ltd | Cooling device of bushing |
JPS52107398U (en) * | 1976-02-12 | 1977-08-16 | ||
JPS56141316U (en) * | 1980-03-26 | 1981-10-26 | ||
JPS5755125U (en) * | 1980-09-18 | 1982-03-31 | ||
WO2007107119A1 (en) | 2006-03-21 | 2007-09-27 | Beijing Ruiheng Super High Voltage Electrical Equipment Research Institute | Current carrier combined with heat-pipe |
CN101369483A (en) | 2008-06-24 | 2009-02-18 | 中国科学院电工研究所 | Heat pipe type transformer tube |
EP2704157A1 (en) | 2012-12-19 | 2014-03-05 | ABB Technology Ltd | Electrical insulator bushing |
-
2014
- 2014-10-08 EP EP14188027.8A patent/EP2942787A1/en not_active Withdrawn
Patent Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5178399U (en) * | 1974-12-18 | 1976-06-21 | ||
JPS528496A (en) * | 1975-07-09 | 1977-01-22 | Hitachi Ltd | Cooling device of bushing |
JPS52107398U (en) * | 1976-02-12 | 1977-08-16 | ||
JPS56141316U (en) * | 1980-03-26 | 1981-10-26 | ||
JPS5755125U (en) * | 1980-09-18 | 1982-03-31 | ||
WO2007107119A1 (en) | 2006-03-21 | 2007-09-27 | Beijing Ruiheng Super High Voltage Electrical Equipment Research Institute | Current carrier combined with heat-pipe |
CN101369483A (en) | 2008-06-24 | 2009-02-18 | 中国科学院电工研究所 | Heat pipe type transformer tube |
EP2704157A1 (en) | 2012-12-19 | 2014-03-05 | ABB Technology Ltd | Electrical insulator bushing |
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