Method for manufacturing an uv-cured composite insulator

Abstract

 The present invention is concerned with the curing of electrical insulators, and particular with improving the curing of electrical insulators.
A method (100) of manufacturing an electrical insulator for high voltage or high current applications utilizing UV-curing is provided comprising the steps of providing fibres (202), impregnating the fibres (202) with an UV-curable matrix (203) by an impregnation device (201, 101), forming a tubular electrical insulator by using the fibres (202, 102), and curing the UV-curable matrix (203) by exposing the impregnated fibres (202) to UV-radiation (206) emitted from an UV-light source (205, 103).

Description

FIELD OF THE INVENTION

[0001] The invention relates to electrical insulators. In particular, the invention relates to a method of manufacturing an electrical insulator for high voltage or high current applications utilizing UV curing, and to a tubular electrical insulator for high voltage or high current applications manufactured according to the method.

BACKGROUND OF THE INVENTION

[0002] In the field of medium and high voltage applications fibre impregnated hollow core insulators are widely used.

[0003] The manufacturing process of a hollow core insulator may consist of three steps. In step 1 the fibres (rovings or fabrics) are soaked with a polymeric resin in an impregnation bath. Afterwards (step 2) they are wound to a rotating mandrel until the required wall thickness is achieved. Finally (step 3), the obtained composite, in which the impregnating resin is still liquid and needs to be cured, is placed in a hot oven for the thermally induced cross-linking process.

[0004] In order to have a homogeneous resin distribution, within the whole composite, the mandrel has to be rotated also in the oven. The complete cure can take from few hours up to one day depending on the size of the manufactured piece and on the curing kinetics of the polymeric resin.

SUMMARY OF THE INVENTION

[0005] It may be seen as an object of the invention to provide for an improved flexible and efficient manufacturing process of an electrical insulator.

[0006] This object is achieved by a method of manufacturing an electrical insulator for high voltage or high current applications utilizing UV-curing, and by a tubular electrical insulator for high voltage or high current applications manufactured according to the method according to the independent claims. Further embodiments are evident from the dependent claims.

[0007] According to one embodiment of the invention, a method of manufacturing an electrical insulator for high voltage or high current applications utilizing UV-curing is provided, comprising the steps of providing fibres, impregnating the fibres with an UV-curable matrix by an impregnation device, forming a tubular electrical insulator by using the fibres, and curing the UV-curable matrix by exposing the impregnated fibres to UV-radiation emitted from an UV light source.

[0008] The UV-curable matrix, a comparably soft constituent, may embed comparably strong and stiff components, for example in elongated form, such as the above mentioned fibres, forming a composite. The composite is a mix of fibres and the matrix. The matrix is designed for mechanically and/or chemically cross-linking at least one component such as an organic component, for example one of a polymeric resin, a vinyl ester, a polyurethane, an epoxy resin, an acrylic resin, an anhydride, an amine, an acrylate system, a methacrylate system, a styrene, an unsaturated polyester, a vinyl ether, an unsaturated ester, an imide, a cinnamate system, a chalcone system, a stilbazolium system, and a combination thereof, when being cured forming a fibre/matrix mixture or composite. Such a composite may show marked anisotropy meaning that their properties vary significantly when measured in different directions, for example because possible fibres are aligned in particular directions.

[0009] Such an insulator may for example be used for insulating the windings of a transformer and/or may be used to embed an electric switch gear or metal oxide surge arresters for high voltage.

[0010] Such a manufacturing method may provide a higher flexibility and efficiency on manufacturing an electrical insulator because of the possibility to manufacture a multiple layer structure and because of no material losses due to dripping. In some case of conventional manufacturing material losses can be approximately 10% of the matrix compared to a manufacturing process without UV-curing with material loss due to dripping because the impregnation matrix is liquid until a thermal induced cross-linking process starts. In the case of manufacturing without UV curing, dripping matrix is collected and reused. For sensitive applications this can be dangerous because of an additional risk of contamination and trapped air bubbles.

[0011] Thermal curing of wet wound insulators may be replaced by UV-curing or a combination of UV-curing and thermal curing according to such a method. The method is characterized by simplicity, enables to have a more flexible design of the electrical insulator, reduced volatile organic compound (VOC) emission, if required, and reduced material losses.

[0012] Furthermore, complicated and expensive hot air ovens to thermally cure the windings of the insulator around the mandrel, wherein the mandrel has to be continuously rotated in order to ensure a thermal cross-linking, is not needed anymore using the above mentioned method utilizing UV-curing.

[0013] A short solidification time of liquid matrix may be enabled by such a method as well as essentially no material losses because no dripping occurs. Furthermore emissions of VOCs such as anhydrides due to evaporation which could lead to allergisation of the workers and environmental issues are avoidable, if required, using the above mentioned method.

[0014] Another advantage of such a method is that an occupation time of a mandrel can be reduced because the long thermal curing step may be omitted. High throughputs without numerous expensive mandrels may be provided by a manufacturing of the electric insulator due to the method because the electrical insulator can be manufactured without any time losses and without any time intervals continuously.

[0015] Such a method provides for an easy change of fibre types and/or matrix types within the production of the same insulator as the liquid may not be liquid during the winding process. Therefore, a multiple layer structure can be achieved which gives more flexibility in the optimization of the insulator properties, e.g. enabling to have a chemical resistant inner and/or outer layer and a high mechanical performance material in the bulk. Inhomogeneity and mixture of different matrix types may be dissolved or be minimized.

[0016] Further advantages of such a method utilizing UV-curing instead of thermal curing are a faster curing, reduced material losses, a variable layer structure, a more simplified manufacturing processing, a more flexible design of the electrical insulator and a reduced emission of volatile organic compounds (VOC) because there may be no need of anhydrides, amines, polyesters, if required, as curing can be achieved by the in situ curing of matrix impregnated fibres by means of UV radiation. Optionally the solid insulator can be afterwards thermally post-cured to ensure full cure.

[0017] Such a method enables a higher variability on designing the composite insulator as it is possible to manufacture a multiple layer structure. If thermal post curing is applied or needed, no continuous rotation of the mandrel is needed during the thermal curing.

[0018] According to an embodiment of the invention the above mentioned formed tubular electrical insulator may be hollow.

[0019] According to another embodiment of the invention the tubular electrical insulator may be have at least partially the form of a shell.

[0020] According to another embodiment of the invention the insulation thickness and/or wall thickness may vary along a longitudinal axis and/or a radial axis of the tubular electrical insulator.

[0021] According to another embodiment of the invention the form of the cross-section of the tubular electrical insulator may be at least partly circular, rectangular, triangular, cylindrical, poliangular, and combinations thereof.

[0022] According to another embodiment of the invention the form of the cross section of the tubular electrical insulator may be non-circular.

[0023] According to another embodiment of the invention the form and/or size of the cross section of the tubular electrical insulator may vary along the longitudinal axis of the tubular electrical insulator.

[0024] According to another embodiment of the invention an electrical insulator may be manufactured using a UV-curable matrix to impregnate the fibres. After impregnation, the matrix may be exposed to an UV-light source, which may be placed directly after the impregnation bath and/or along the mandrel. The reactivity of the matrix may be controlled in a way that the liquid state is long enough to obtain strong and void-free interface between the individual plies.

[0025] Due to the good mechanical performance and to the good price performance ratio, glass fibres are often preferred as fillers. Alternatively aramid, basalt, polyethylene naphthalate (PEN) or polyethylene teraphthalate (PET) fibres can also be used. As impregnation matrix a thermally curable anhydride/epoxy or amine/epoxy matrix system is often used, as it allows obtaining electrical insulators with good mechanical and electrical properties.

[0026] According to another embodiment of the invention, additionally a reactivity and a viscosity of the matrix may be controlled, and the mandrel and an impregnation bath may be heated or cooled accordingly.

[0027] According to another exemplary embodiment, the winding process may be divided in different steps in which the UV-curable matrix and/or the fibres may be changed. A corrosion or heat resistant matrix/fibre system may be used for example to form an inner layer of about 1 mm thickness and can be cured in situ. Subsequently, another matrix-/fibre system which has high mechanical performance may be used. At the end again another matrix/fibre may be used in order to obtain, as outer shell, a UV-resistant layer.

[0028] According to another exemplary embodiment already impregnated fibres, such as pre-impregnated fibres, can be wound around a mandrel and UV-cured. The fibres may be impregnated by a bath or may already be pre-impregnated and wound on another mandrel before being wound from the other mandrel around the mandrel for manufacturing the electric insulator and the UV-curing of the fibres at the mandrel. The UV-curing may also take place at the other mandrel which enables to omit the step of winding the pre-impregnated fibres from the other mandrel to the mandrel.

[0029] According to another exemplary embodiment the UV-curing can proceed parallel to the winding.

[0030] According to another embodiment of the invention the fibres can be wound around the mandrel, impregnated at the mandrel, and afterwards UV-cured.

[0031] According to another embodiment of the invention, the UV-light source may be arranged at a winding head that is movable along the mandrel, for example next to an eye such as a fibre payout eye, through which the fibres are directed to the mandrel before the winding to the mandrel. The UV-light source may have a length of 10-20 cm or may be as long as the mandrel, for example 2-10 m, for example by using multiple UV bulbs. For fast curing system even a spot-light source or a UV light emitting diode can be used as UV source. The UV-light source may emit UV-radiation continuously or in certain time intervals such as 1 second to 1 minute.

[0032] According to another embodiment of the invention, the UV-light source is arranged along the mandrel.

[0033] According to another embodiment of the invention, the fibres or the fibre rovings may have a thickness of about 15-200 µm and a width of about 1-5 mm.

[0034] According to another embodiment of the invention several rovings of 2 to 48 single rovings may be wound on the mandrel together in one step. The rovings may form a band with a width of 1 cm to 10 cm.

[0035] According to another embodiment of the invention, there can be used fibre types such as woven fabrics instead of fibres. The woven fabrics may have the form of a tape of a range of 1cm to 15cm in width in order to be able to wind the woven fabrics in a certain angle around the mandrel or may have the form of a fabric to wind the woven fabrics in one step along the complete mandrel length.

[0036] According to another embodiment of the invention, the electrical insulator is selected from the group consisting of a composite insulator, a hollow composite insulator, a hollow core insulator, a chamber insulator, a dry transformer, and a driver insulator. The insulator may be used for bushings, as a surge arrestor or as a gas fill insulator.

[0037] According to another embodiment of the invention, the method is a continuous method wherein the fibres are wound with a velocity of 0,1-1 m/s.

[0038] According to another embodiment of the invention, the forming of the tubular electrical insulator comprises the step of winding the fibres around the mandrel.

[0039] According to another embodiment of the invention, the forming of the method further comprises the steps of arranging at least one device on a first layer of the wound fibres and winding a second layer of fibres such that the at least one device is covered at least partially by the second layer of fibres such that the at least one device may be integrated in the tubular electrical insulator.

[0040] According to another embodiment of the invention, the at least one device is a device selected from the group consisting of a metal layer, a metal grid, an active sensor, a passive sensor, an aluminium layer, a metal foil, and an aluminium foil.

[0041] According to another embodiment of the invention, the at least one device is a device selected from the group consisting of a metal conductor, a metal wire, a copper wire, an aluminium wire, an insulated copper wire, and an insulated aluminium wire.

[0042] According to another embodiment of the invention, the at least one device is a device selected from the group consisting of a semi-conductive layer, consisting of semi conductive materials containing for example metal oxide ceramics, Silicone carbide, graphite or other semi-conductive materials.

[0043] According to another embodiment the above mentioned method further comprises the steps of providing matrix, forming a first layer of a tubular electrical insulator by UV-curing and/or thermal curing the matrix.

[0044] According to another embodiment of the invention, the UV-curing and/or thermal curing may take place after winding the fibres around the mandrel.

[0045] According to another embodiment of the invention, the UV-curing and/or thermal curing may take place after winding the fibres around the wound fibres and the thereon arranged at least one device.

[0046] According to another embodiment of the invention, the at least one device may be wound around the wound fibres at the mandrel.

[0047] According to another embodiment of the invention, the at least one device may be wound around a mandrel in a first step, and fibres may be wound around the mandrel with the wound at least one device in a second step. Afterwards, in a third step, further fibres may be wound around the layer of wound fibres.

[0048] According to another embodiment of the invention, a plurality of layers of fibres may be wound around the mandrel before arranging the at least one device at the wound fibres and after arranging the at least one device at the wound fibres.

[0049] According to another embodiment of the invention, an integrated at least one device is wound around a first layer of fibres and forms a spiral embedded in the UV-cured insulation.

[0050] According to another embodiment the at least one device is a coil of a transformer.

[0051] According to another embodiment the at least one device is a field control electrode.

[0052] According to another embodiment of the invention, the fibres are impregnated at the mandrel during the winding of the fibres around the mandrel.

[0053] According to another embodiment of the invention, the fibres are impregnated before the winding.

[0054] According to another embodiment of the invention, the fibres are pre-impregnated at a first position before the winding and impregnated at a second position at the mandrel during the winding.

[0055] According to another embodiment of the invention, the impregnation device is an impregnation bath.

[0056] According to another embodiment of the invention, the method further comprises the step of thermally curing the UV-curable matrix by a thermal source.

[0057] According to another embodiment of the invention, the thermal curing proceeds after the UV-curing.

[0058] According to another embodiment of the invention partly thermal curing is carried out before the UV-curing.

[0059] According to another embodiment of the invention, at least a first percentage of the UV-radiation is directed towards the fibres at a first position before the fibres are wound around the mandrel.

[0060] According to another embodiment of the invention, at least a second percentage of the UV-radiation is directed at a second position at the mandrel.

[0061] According to another embodiment of the invention, the UV-light source is movable along the mandrel and along the fibres before the fibres are wound around the mandrel.

[0062] According to another embodiment of the invention, the method further comprises the step of controlling a reactivity of the matrix such that a liquid state of the matrix is long enough to obtain a strong and void-free interface between individual plies of impregnated fibres.

[0063] According to another embodiment of the invention, the method further comprises the step of controlling at least one of a reactivity and a viscosity of the matrix by controlling the temperature of the mandrel and the impregnation device.

[0064] According to another embodiment of the invention, the method further comprises the steps of winding first fibres which are impregnated by a first UV-curable matrix around the mandrel, curing the first UV-curable matrix by exposing the first impregnated fibres to the UV-radiation, winding second fibres which are impregnated by a second UV-curable matrix around the mandrel, curing the second UV-curable matrix by exposing the second impregnated fibres to the UV-radiation, winding third fibres which are impregnated by a third UV-curable matrix around the mandrel, and curing the third UV-curable matrix by exposing the third impregnated fibres to the UV-radiation.

[0065] According to another embodiment of the invention, the first impregnated fibres form, in combination with the impregnating first UV-curable matrix, at least one of a corrosion resistive layer and a heat protection layer. The second impregnated fibres form, in combination with the impregnating second UV-curable matrix, a mechanical stabilizing layer, wherein the third impregnated fibres form, in combination with the impregnating second UV-curable matrix, an UV-resistant layer.

[0066] According to another embodiment of the invention, the matrix is one of the group comprising a vinyl ester, a polyurethane, an epoxy resin, an acrylic resin, an anhydride resin matrix, an amine resin matrix, an acrylate system, a methacrylate system, a styrene, an unsaturated polyester, a vinyl ether, an unsaturated ester, an imide, a cinnamate system, a chalcone system, a stilbazolium system, a polymeric resin, and combinations thereof.

[0067] According to another embodiment of the invention, the fibres are one of the group comprising glass fibres, polyesters, basalt, aramids in form of one of strands, fabrics, fleece, roving, and filaments.

[0068] According to another embodiment of the invention the electrical insulator is the insulator of a transformer.

[0069] According to another embodiment of the invention, a device for manufacturing an electrical insulator according to the method of one of the preceding embodiments is provided, comprising an impregnating device, for impregnating fibres with an UV-curable matrix, a mandrel for winding the fibres, and an UV-light source for emitting UV-radiation to the impregnated fibres for curing the UV-curable matrix.

[0070] According to another exemplary embodiment, a plurality of units providing single fibres that are wound to a single fibre thread or filament consisting of a plurality of fibres is provided.

[0071] According to another embodiment of the invention, the impregnation device is movable in a direction along the mandrel and in a direction of the fibres before being wound around the mandrel, for example perpendicular to the direction along the mandrel.

[0072] According to another embodiment of the invention, the mandrel is movable in a direction along the mandrel and in a direction of the fibres before being wound around the mandrel, for example perpendicular to the direction along the mandrel.

[0073] According to another embodiment of the invention, the UV-light source is movable in a direction along the mandrel and in a direction of the fibres before being wound around the mandrel, for example perpendicular to the direction along the mandrel.

[0074] According to another embodiment of the invention, the device further comprises a thermal source for thermally curing the UV-curable matrix.

[0075] According to another embodiment of the invention, the thermal source is movable along the mandrel and along the impregnated fibres before the fibres are wound to the mandrel.

[0076] According to another embodiment of the invention, the device further comprises a first direction unit for directing at least a first percentage of the UV-radiation towards the fibres, before the fibres are wound to mandrel, and a second direction unit for directing at least a second percentage of the UV-radiation towards the mandrel.

[0077] According to another embodiment of the invention, the first direction unit is movable in a direction along the mandrel and in a direction along the fibres before the fibres are wound around the mandrel, for example perpendicular to the direction along the mandrel.

[0078] According to another embodiment of the invention, the first direction unit is rotatable such that it may direct UV-radiation to the fibres before the fibres are wound around the mandrel and at the mandrel with the wound fibres.

[0079] According to another embodiment of the invention, the second direction unit is movable in a direction along the mandrel and in a direction along the fibres before the fibres are wound around the mandrel, for example perpendicular to the direction along the mandrel.

[0080] According to another embodiment of the invention, the second direction unit is rotatable such that it may direct UV-radiation to the fibres before the fibres are wound around the mandrel and at the mandrel with the wound fibres.

[0081] According to another embodiment of the invention, the first and second direction units form a single direction unit for directing the at least first percentage and the at least second percentage of the UV-radiation towards the mandrel and/or the fibres before the fibres are wound around the mandrel.

[0082] According to another embodiment of the invention, the device further comprises a first controlling unit for controlling at least one of a reactivity and a viscosity of the UV-curable matrix by controlling a temperature of the mandrel and the impregnating device, and comprises a second controlling unit for controlling the impregnating device, the mandrel, and the UV-light source in such a way, that UV-curable matrices and fibres are impregnated, wound and cured to layers with different characteristics, such as corrosion and heat protective, mechanically stabilizing, UV-resistance. The layers may be manufactured and arranged one after another.

[0083] According to another embodiment of the invention, the first and second controlling unit can be one controlling unit.

[0084] According to another embodiment of the invention a tubular electrical insulator for high voltage or high current applications is manufactured according to the method of one of the preceding embodiments.

[0085] According to another embodiment of the invention the tubular electrical insulator comprises a photoinitiator and by-products resulting from the chemical reaction of the photoinitiator with the UV-radiation. The UV-cured matrix and the fibres of the tubular electrical insulator are selected from the UV-curable matrices according to one of the above mentioned embodiments. The photoinitiator is designed for initiating polymerization of the UV-cured matrix and the fibres.

[0086] The photoinitiator is selected from the group comprising sulfonium salts, iodonium salts, triflates, sulfonates, aryl-alkyl ketones, benzophenone, benzophenone derivates, quinones, camphorquinone, xanthone, xanthone derivates, thioxanthone, thioxanthone derivates, fluorenone derivates, benzyl, benzyl derivates, and combinations thereof. The by-products are common by-products resulting from the chemical reaction involving a photoinitiator as mentioned above.

[0087] These and other aspects of the present invention will become apparent from and elucidated with reference to the embodiments described hereafter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0088] The subject-matter of the invention will be explained in more detail in the following text with reference to exemplary embodiments which are illustrated in the attached drawings.

Fig. 1A shows a flow-chart of a method of manufacturing an electrical insulator for high voltage or high current applications utilizing UV-curing according to an embodiment of the invention.

Fig. 1B shows another flow-chart of a method of manufacturing an electrical insulator for high voltage or high current application utilizing UV-curing according to another embodiment of the invention.

Fig. 2A schematically shows a device for manufacturing an electrical insulator according to the methods of Fig. 1A and Fig. 1B according to an embodiment of the invention.

Fig. 2B schematically shows a sectional view of the device for manufacturing an electrical insulator of Fig. 2A according to an embodiment of the invention.

Fig. 2C schematically shows a device for manufacturing an electrical insulator according to another embodiment of the invention.

Fig. 2D schematically shows a device of manufacturing an electrical insulator according to another embodiment of the invention.

Fig. 2E schematically shows a device of manufacturing an electrical insulator according to another embodiment of the invention.

[0089] The reference symbols used in the drawings, and their meanings, are listed in summary form and a list of reference symbols. In principle, identical parts are provided with the same reference symbols in the figures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0090] Fig. 1A shows a method 100 of manufacturing an electrical insulator for high voltage or high current applications utilizing UV-curing with the steps of providing fibres, impregnating the fibres with an UV-curable matrix by an impregnation device 101, forming a tubular electrical insulator by using the fibres 102, curing the UV-curable matrix by exposing the impregnated fibres to UV-radiation emitted from an UV-light source 103, thermally curing the UV-curable matrix by a thermal source 104, and controlling at least one of the reactivity and a viscosity of the matrix by controlling the temperature of the mandrel and the impregnation device 105.

[0091] According to the method of Fig. 1A already impregnated fibres or pre-impregnated fibres can be wound around a mandrel and UV-cured, wherein the curing can proceed parallel to the winding. Furthermore the fibres can be wound around the mandrel, impregnated at the mandrel and afterwards UV-cured.

[0092] The UV-light source may be arranged at a winding head movable along the mandrel, next to an eye, for example a fibre payout eye, through which the fibres may be directed before the winding to the mandrel. The UV-light source may have a length of 10-20 cm or may be as long as the mandrel, for example 2-10 m, for example by using multiple UV bulbs. For fast curing system a spot-light source or a UV light emitting diode may be used as UV source. The UV-light source may emit UV-radiation continuously or inserted time intervals such as 1 second to 1 minute.

[0093] The UV-light source may be arranged along the mandrel.

[0094] Fibres, or fibre rovings may have a thickness of about 15-200 µm and a width of about 1-3 mm. Alternatively there can be used fibres types such as woven fabrics. Instead of winding single rovings around the mandrel several rovings of 2 to 48 single rovings may be wound on the mandrel together in one step. The rovings may form a band with a width of 1 cm to 10 cm.

[0095] The electrical insulator may be selected from the group consisting of a composite insulator, a hollow composite insulator, a hollow core insulator, a chamber insulator, a dry insulator, and a driver insulator and may be used for bushings, as a surge arrestor, a transformer or as a gas fill insulator.

[0096] The method according to Fig. 1A and according to Fig. 1B may be a continuous method wherein the fibres may be wound with a velocity of 0.1 - 1 m/s.

[0097] The fibres may be wound according to the method with a respectively higher velocity, such as 2 m/s, for example.

[0098] The forming of the tubular electrical insulator 102 may comprise the steps of winding the fibres around the mandrel, arranging at least one device on a first layer of the wound fibres such that the at least one device is covered at least partially by the second layer of fibres (202) such that the at least one device may be integrated in the tubular electrical insulator.

[0099] The at least one device may be a device selected from the group consisting of a metal layer, a metal grid, an active sensor, a passive sensor, an aluminium layer, a metal foil, a coil of a transformer, a field control electrode, and an aluminium foil. The UV-curing and also thermal curing may take place after winding the fibres around the mandrel. The UV-curing and/or thermal curing may take place after winding the fibres around the wound fibres and the thereon arranged at least one device. The at least one device may be wound around the wound fibres at the mandrel.

[0100] In a first step the at least one device may be wound around a mandrel, in a second step fibres may be wound around the mandrel with the wound at least one device, and in a third step further fibres may be wound around the layer of wound fibres.

[0101] A plurality of layers of fibres may be wound around the mandrel before arranging the at least one device at the wound fibres and also after arranging the at least one device at the wound fibres.

[0102] Fig. 1B shows another method of manufacturing an electrical insulator for high voltage or high current applications utilizing UV-curing, comprising the following steps: Providing fibres, impregnating the fibres with an UV-curable matrix by an impregnation device 101, forming a tubular electrical insulator by using the fibres 102, curing the UV-curable matrix by exposing the impregnated fibres to UV-radiation emitted from a UV-light source 103, thermally curing the UV-curable matrix by a thermal source 104, controlling at least one of a reactivity and a viscosity of the matrix by controlling the temperature of the mandrel and the impregnation device 105, winding first fibres which are impregnated by a first UV-curable matrix around the mandrel 106, curing the first UV-curable matrix by exposing the first impregnated fibres to UV-radiation 107, winding second fibres which are impregnated by a second UV-curable matrix around the mandrel 108, curing the second UV-curable matrix by exposing the second impregnated fibres to the UV-radiation 109, winding third fibres which are impregnated by a third UV-curable matrix around the mandrel 110, and curing the third UV-curable matrix by exposing the third impregnated fibres to the UV-radiation 111.

[0103] The method of Fig. 1B can also comprise the step of controlling a reactivity of the matrix such that a liquid state of the matrix is long enough to obtain a strong and void-free interface between individual plies of impregnated fibres.

[0104] The UV-light source of Fig. 1A and Fig. 1B may be movable around the mandrel and along the fibres before the fibres are wound around the mandrel.

[0105] The thermal curing may take place after the UV-curing, for example there may be a partly thermal curing before the UV-curing.

[0106] The fibres may be impregnated at the mandrel during the winding of the fibres around the mandrel.

[0107] The fibres may be impregnated before the winding, for example pre-impregnated at a first position before the winding and impregnated at a second position at the mandrel during the winding.

[0108] The methods of Fig. 1A and Fig. 1B may be designed such that at least a first percentage of the UV-radiation is directed towards the fibres at a first position before the fibres are wound around the mandrel, and wherein at least the second percentage of the UV-radiation is directed at a second position at the mandrel.

[0109] The first impregnated fibres may form, in combination with the impregnated first UV-curable matrix, at least one of a corrosion resistive layer and a heat protection layer. The second impregnated fibres may form, in combination with the impregnating second UV-curable matrix, a mechanical stabilizing layer. The third impregnated fibres may form, in combination with the impregnating third UV-curable matrix, an UV-resistant layer.

[0110] The matrix may be one of the group comprising a vinyl ester, a polyurethane, an epoxy resin, an acrylic resin, an anhydride, an amine, an acrylate system, a methacrylate system, a styrene, an unsaturated polyester, a vinyl ether, an unsaturated ester, an imide, a cinnamate system, a chalcone system, a stilbazolium system, a polymeric resin, and combinations thereof.

[0111] The UV-curable matrix 203 may comprise a photoinitiator. The photoinitiator is designed for initiating polymerization of the UV-cured matrix 203 and the fibres 202.

[0112] The photoinitiator is selected from the group comprising sulfonium salts, iodonium salts, triflates, sulfonates, aryl-alkyl ketones, benzophenone, benzophenone derivates, quinones, camphorquinone, xanthone, xanthone derivates, thioxanthone, thioxanthone derivates, fluorenone derivates, benzyl, benzyl derivates, and combinations thereof.

[0113] The UV-curable matrix 203 may comprise a thermal catalyst for reinforcing the composite of the UV-curable matrix 203 and the fibres 202.

[0114] The fibres 202 may be one of the group consisting of glass fibres, polyesters, basalts, aramids in form of one of strands, fabrics, fleece, roving, and filaments.

[0115] Fig. 2A shows a device 200 for manufacturing an electrical insulator according to the methods of Fig. 1A and Fig. 1B, comprising an impregnating device 201 for impregnating fibres 202 with an UV-curable matrix 203, a mandrel 204 for winding the fibres 202, and an UV-light source 205 for emitting UV-radiation 206 to the impregnated fibres 202 for curing the UV-curable matrix 203.

[0116] Before the fibres 202 are impregnated, and wound around the mandrel 204, the fibres may be wound around another mandrel 216. A plurality of units (not shown) providing single fibres may wind the single fibres to one fibre thread 202 or filament 202.

[0117] A thermal source 208 may be applied for thermally curing the UV-curable matrix 203 and may be arranged at the mandrel 204 to provide thermal curing after the impregnated fibres 202 are wound around the mandrel 204. The thermal source 208 may be movable along the mandrel 204 and along the fibres 202 before they are wound around the mandrel 204.

[0118] After being wound of the mandrel 216 the fibres 202 pass an impregnation device 201 such as an impregnation bath 202 with an UV-curable matrix 203 are impregnated by the UV-curable matrix 203 and a afterwards directed to an eye 219, such as a fibre payout eye 219, of a movable winding head 218. The fibres 202 are directed through the eye 219 to be wound around the mandrel 204. The winding head 218 is movable in an X-direction along the mandrel 204 and in a Z-direction along the fibres 202 before the fibres 202 are wound around the mandrel, for example a Z-direction vertical to the longitudinal direction of the mandrel 204. The mandrel 204 may have a length of 2-10 m. The UV-light source 205 is arranged at the winding head 218 and is designed for emitting UV-radiation 206 towards the fibres at a first position before the fibres 202 are wound around the mandrel 204. The UV-light source 205 is also designed for emitting UV-radiation 206 in a direction at a second position towards the mandrel 204.

[0119] The winding head 218 is movable along the mandrel 204 and along the fibres 202 before the fibres 202 are wound around the mandrel 204.

[0120] A first controlling unit 214 for controlling at least one of a reactivity and a viscosity of the UV-curable matrix 203 of the impregnation bath 201 is applied to control a temperature of the mandrel 204 and the impregnation device 201.

[0121] A second controlling unit 215 is designed for controlling the impregnation device 201, the winding head 218, the UV-light source 205, the mandrel 216, and the mandrel 204 in such a way, that UV-curable matrices 203 and fibres 202 are impregnated, wound and cured to layers with different characteristics, such as corrosion and heat protective, mechanically stabilizing, and UV-resistance. The layers (see Fig. 2B) are manufactured and arranged one after another.

[0122] Fig. 2B shows a cross-sectional view of the device 200 for manufacturing an electrical insulator of Fig. 2A.

[0123] First fibres 2201, second fibres 2211 and third fibres 2221 are wound around a mandrel 216. From the mandrel 216 the first fibres 2201 pass an impregnation device 201 with a first UV-curable matrix 2031 and are impregnated by the first UV-curable matrix 2031 before passing through the eye 219 of the winding head 218. The first UV-curable matrix 2031 is then cured by exposing the first impregnated fibres 2201 to the UV-radiation 206 emitted by the UV-radiation source 205 at the winding head 218, and afterwards the cured first UV-curable matrix 2031 and the fibres are wound around the mandrel 204. Furthermore the wound and impregnated first fibres 2201 may comprise a first UV-curable matrix 2031 that may be thermally cured by a thermal source 208. The first fibres 2201 form, in combination with the impregnated first UV-curable matrix 2031, at least one of a corrosion resistive layer and a heat protection layer 2202.

[0124] In a next step second fibres 2211 are wound from the mandrel 216, pass the impregnation bath 201 and are impregnated by a second UV-curable matrix 2032 before passing through the eye 219 of the movable winding head 218 and being exposed to the UV-radiation 206 emitted by the UV-light source 205. The impregnated second fibres 2211 are then wound around the mandrel 204. Afterwards the second UV-curable matrix 2032 of the wound second fibres 2211 may be thermally cured by the thermal source 208. The second impregnated fibres 2211 form, in combination with the impregnating second UV-curable matrix 2032, a mechanically stabilizing layer 2212.

[0125] In a third step the third fibres 2221 are wound from the mandrel 216, pass the impregnating bath 201 and are impregnated by a third UV-curable matrix 2033 before passing through the eye 219 of the winding head 218 and being exposed to the UV-radiation 206 emitted by the UV-light source 205. Afterwards the third UV-curable matrix 2033 of the wound third fibres 2221 may be thermally cured by the thermal source 208. The third impregnated fibres 2221 form, in combination with the impregnated third UV-curable matrix 2033, an UV-resistive layer 2222.

[0126] Fig. 2C is a schematic view of a device 200 for manufacturing an electrical insulator according to the methods of Fig. 1A and Fig. 1B.

[0127] Fibres 202 which are wound around the mandrel 216 are guided by an eye 219 of a winding head 218 to another mandrel 204 and wound around the mandrel 204. At the head 218 is arranged an UV-light source 205 which emits UV-radiation 206 to the fibres 202 before being wound around the mandrel and at the wound fibres 202 at the mandrel 204. The head 218 and the UV-light source 205 are movable in a X-direction along the mandrel as well as in a Z-direction towards the fibres 202 before the fibres 202 are wound around the mandrel 204, for example in a direction perpendicular to the X-direction along the mandrel 204. The fibres 202 are pre-impregnated by an UV-curable matrix. The pre-impregnated fibres are wound around a mandrel 216 before being wound around the mandrel 204. The UV-curing of the UV-curable matrix may also be carried out directly at the mandrel 216 with the pre-impregnated fibres 202 wound around the mandrel 216.

[0128] The UV-cured UV-curable matrix of the wound fibres 202 may be thermally cured by a thermal source 208 which is arranged along the mandrel 204. The thermal source 208 may be movable in a direction along the mandrel 204 and in a direction along the fibres 202 before they are wound around the mandrel 204 according to the embodiments of Fig 2A to Fig. 2D.

[0129] The first controlling unit 214 is applied for controlling the temperature of the mandrel 204 for controlling a reactivity of the UV-curable matrix being already applied at the pre-impregnated fibres 202.

[0130] A second controlling unit 215 is adapted for controlling the mandrel 204, the mandrel 216, the winding head 218, and the UV-light source 205 in such a way, that UV-curable matrices and the pre-impregnated fibres 202 are wound and cured to layers with different characteristics, such as corrosion, and heat protective, mechanical stabilizing and UV-resisting layers, wherein the layers are manufactured and arranged one after another (see Fig. 2B).

[0131] Fig. 2D schematically shows a device 200 for manufacturing an electrical insulator according to the methods of Fig. 1A and Fig. 1B. Pre-impregnated fibres are re-wound from the mandrel 216 and are directed through an eye 219 of a winding head 218 at which an UV-light source 205 is arranged. The winding head 218 guides the pre-impregnated fibres 202 to a mandrel 204 in such a way, that the pre-impregnated fibres are wound around the mandrel 204.

[0132] A first directing unit 209 is applied for directing at least a first percentage of the UV-radiation 210 emitted by the UV-light source towards the fibres 202 at a first position 210 before the fibres 202 are wound around the mandrel 204.

[0133] A second direction unit 211 is applied for directing at least a second percentage of the UV-radiation 212 emitted by the UV-light source 205 at a second position 212 at the mandrel after the pre-impregnated fibres 202 are wound around the mandrel 212. The UV cured UV-curable matrix of the wound fibres 202 may be thermally post-cured by a thermal source 208 which is arranged along the mandrel.

[0134] The first direction unit 209 and the second direction unit 211 are movable in a X-direction along the mandrel 204 and in a Z-direction along the fibres 202 before the fibres are wound around the mandrel 204, for example perpendicular to the X-direction along the mandrel 204.

[0135] The first direction unit 209 and the second direction unit 211 are rotatable such that they may direct UV-radiation 210, 212 individually to the fibres 202 before the fibres 202 are wound around the mandrel 202 and at the mandrel 204 with the wound fibres 202.

[0136] The first direction unit 209 and second direction unit 211 may form a single direction unit for directing the at least first percentage of UV-radiation 210 and the at least second percentage of UV-radiation 212 towards the mandrel 204 and/or the fibres 202 before the fibres 202 are wound around the mandrel 204.

[0137] A first controlling unit 214 is designed for controlling the reactivity of the pre-impregnated fibres 202, especially the UV-curable matrix of the pre-impregnated fibres 202, by controlling a temperature of the mandrel 204. A second controlling unit 215 is designed for controlling the mandrel 216, the mandrel 204, the UV-light source 205, the winding head 218, the thermal source 208, the first direction unit 209, and the second direction unit 211 in such a way, that UV-curable matrices with the pre-impregnated fibres 202 are wound and cured to layers for example with different characteristics, such as corrosion and heat protection, mechanical stabilizing, and UV-resistance, wherein the layers are manufactured and arranged one after another (see Fig. 2B).

[0138] The first direction unit 209 and the second direction unit 211 may be selected of the group consisting of a reflector, an UV reflecting matrix, and an UV-reflecting grid.

[0139] Fig. 2E shows a schematic presentation of a device 200 for manufacturing an electrical insulator according to the methods of Fig. 1A and Fig. 1B comprising a mandrel 216 onto which fibres 202 are wound. The wound fibres 202 are re-wound from the mandrel 216 and guided by a winding head 218 through an eye 219 to be wound around another mandrel 204. The movable head 219 is movable along the mandrel 204 in an X-direction. The fibres 202 after being wound around the mandrel 204, impregnated by an impregnation device 201 with an UV-curable matrix 203 directly at the mandrel 204. After the impregnation, the UV-curable matrix of the wound fibres is UV-cured by UV-radiation 206 emitted by an UV-light source 205 which is arranged along the mandrel. The impregnation device 201 is also arranged along the mandrel 204.

[0140] A first controlling unit 214 is adapted for controlling at least one of a reactivity and a viscosity of the UV-curable matrix 203 by controlling a temperature of the mandrel 204 and of the impregnation device 201.

[0141] A second controlling unit 215 is adapted for controlling the impregnation device 201, the movable winding head 218, the mandrel 216, the mandrel 204, and the UV-light source 205 in such a way, that UV-curable matrices 203 and fibres 202 are impregnated, wound and cured to at least one layer or layers which different characteristics, such as a corrosion and a heat protective, mechanically stabilizing, UV-resistance, wherein the layers may be manufactured and arranged one after another (see Fig. 2B).

[0142] The first and the second controlling unit 214, 215 may be integrated to one controlling unit according to the embodiments of Fig. 2A to Fig. 2E.

[0143] While the invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description are to be considered illustrative or exemplary and not restricted; the invention is not limited to the disclosed embodiments.

[0144] Other variations of the disclosed embodiments may be understood and effected by those skilled in the art and practising the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

[0145] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single device for manufacturing an electrical insulator may fulfil the function of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures may not be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

LIST OF REFERENCE SYMBOLS

[0146] 

200

Device for manufacturing an electrical insulator

201

Impregnation device, impregnation bath

202

Fibres, impregnated fibres

203

UV-curable matrix

204

Mandrel

205

UV-light source

206

UV-radiation

208

Thermal source

209

First direction unit

210

First percentage of UV-radiation, first position

211

Second direction unit

212

Second percentage of UV-radiation, second position

214

First controlling unit

215

Second controlling unit

216

Mandrel

218

Winding head

219

Eye, fibres payout eye

2201

First fibres

2202

Corrosion resistive layer, heat protection layer

2211

Second fibres

2212

Mechanically stabilizing layer

2221

Third fibres

2222

UV-resistant layer

2031

First UV-curable matrix

2032

Second UV-curable matrix

2033

Third UV-curable matrix

X

X-direction, direction along the mandrel

Z

Z-direction, direction perpendicular to the direction along mandrel

Claims

1. Method (100) of manufacturing an electrical insulator for high voltage or high current applications utilizing UV-curing, the method (100) comprising the steps of:

Providing fibres (202);

Impregnating the fibres (202) with an UV-curable matrix (203) by an impregnation device (101);

Forming a tubular electrical insulator by using the fibres (202, 102);

Curing the UV-curable matrix (203) by exposing the impregnated fibres (202) to UV-radiation (206) emitted from an UV-light source (205, 103).

2. The method (100) of claim 1,
wherein the forming of the tubular electrical insulator (102) comprises the step of:

Winding the fibres (202) around a mandrel (204).

3. The method (100) of claim 2, the forming further comprising the steps of:

Arranging at least one device on a first layer of the wound fibres;

Winding a second layer of fibres (202) such that the at least one device is covered at least partially by the second layer of fibres (202).

4. The method (100) of claim 3,
wherein the at least one device is an electrically passive device.

5. The method (100) of claim 3,
wherein the at least one device is a field control electrode.

6. The method (100) of any one of claims 2 to 5,
wherein the fibres (202) are impregnated at the mandrel (204) during the winding of the fibres around the mandrel (204).

7. The method (100) of any one of claims 2 to 6,
wherein at least a first percentage (210) of the UV-radiation is directed towards the fibres at a first position (210) before the fibres (202) are wound around the mandrel (204).

8. The method (100) of any one of claims 2 to 7,
wherein at least a second percentage (212) of the UV-radiation is directed at a second position (212) at the mandrel (204).

9. The method (100) of any one of claims 2 to 8, further comprising the step of:

Controlling at least one of a reactivity and a viscosity of the matrix (203) by controlling the temperature of the mandrel (204) and the impregnation device (105).

10. The method (100) of any one of claims 2 to 9, further comprising the steps of:

Winding first fibres (2201) which are impregnated by a first UV-curable matrix (2031) around the mandrel (204, 106);

Curing the first UV-curable matrix (2031) by exposing the first impregnated fibres (2201) to the UV-radiation (206, 107);

Winding second fibres (2211) which are impregnated by a second UV-curable matrix (2032) around the mandrel (204, 108);

Curing the second UV-curable matrix (2032) by exposing the second impregnated fibres (2211) to the UV-radiation (206, 109);

Winding third fibres (2221) which are impregnated by a third UV-curable matrix (2033) around the mandrel (204, 110);

Curing the third UV-curable matrix (2033) by exposing the third impregnated fibres (2221) to the UV-radiation (206, 111).

11. The method (100) of claim 10,
wherein the first impregnated fibres (2201) form, in combination with the impregnating first UV-curable matrix (2031), at least one of a corrosion resistive layer and a heat protection layer (2202);
wherein the second impregnated fibres (2211) form, in combination with the impregnating second UV-curable matrix (2032), a mechanically stabilizing layer (2212);
wherein the third impregnated fibres (2221) form, in combination with the impregnating third UV-curable matrix (2033), an UV resistant layer (2222).

12. The method (100) of any one of claims 1 to 11,
wherein the matrix (203) is one of the group comprising a vinyl ester, a polyurethane, an epoxy resin, an acrylic resin, an anhydride, an amine, an acrylate system, a methacrylate system, a styrene, an unsaturated polyester, a vinyl ether, an unsaturated ester, an imide, a cinnamate system, a chalcone system, a stilbazolium system, a polymeric resin, and combinations thereof.

13. The method (100) of any one of claims 1 to 12, further comprising the step of:

Thermally curing the UV-curable matrix (203) by a thermal source (208, 104).

14. Tubular electrical insulator for high voltage or high current applications manufactured according to the method of any one of claims 1 to 13.

15. The tubular electrical insulator according to claim 14, comprising:

a photoinitiator and by-products resulting from the chemical reaction of the photoinitiator with the UV-radiation.

Drawing