Electrical device comprising at least one cementitious material

Abstract

The invention relates to an electrical device (1) comprising a coil (7) arranged within a cavity (5) of a housing (3), at least one composition comprising at least one dielectric fluid, preferably a dielectric liquid, and at least one material (12) in gel form, and wherein the ratio between the maximum volume occupied by the material (12) in gel form and the total volume of the cavity (5) is less than 50%. The invention also relates to the use of a material (12) in the form of a gel for preventing and / or minimizing leaks in a composition (9) comprising at least one dielectric fluid in an electrical device (1), in particular a transformer or a capacitor.

Description

Summary of the invention

[0001] The present invention relates to an electrical device comprising at least one coil arranged in a cavity of a housing, at least one composition comprising at least one dielectric fluid, preferably a dielectric liquid, and at least one material in gel form, wherein the ratio between the maximum volume occupied by the material in gel form and the total volume of the cavity is less than 50%.

[0002] The invention also relates to the use of a material in gel form for preventing and / or minimizing leakage of a composition comprising at least one dielectric fluid in an electrical device, in particular a capacitor or a transformer. Background Art

[0003] Electrical device or equipment, such as capacitor and transformer, comprises at least one coil and dielectric fluid, and they are arranged in the housing that can be conductive or insulating.The coil corresponding to the active part of electrical device is usually composed of the assembly of multiple layers, particularly one or more windings or stacked assembly, and the multiple layers are connected to each other, and continuously (in succession, successively) alternates between electronic conductive layer and electronic insulating layer.The coil can be impregnated with at least one dielectric fluid and be arranged in the housing or be immersed in the housing that has been filled with at least one dielectric fluid.As an illustration, the coil can correspond to being composed of polypropylene sheet and metal sheet, particularly aluminum sheet, impregnated with the winding of dielectric fluid for example with the oil of high dielectric constant, and the coil can be positioned inside the housing.

[0004] The housing, which has for example a substantially rectangular shape, is usually sealed at its ends by removable (detachable) closing means which are intended to ensure sealing and protection of the electrical device, in particular between its active components and the surrounding environment.

[0005] However, such electrical devices most often have a lifespan that can extend to a period of 30 or 50 years depending on their application. During their operation, external and / or internal stresses tend to cause thermal expansion and / or mechanical degradation of the enclosure of the housing, thereby compromising the sealing and mechanical strength of the active components of the electrical device and increasing the risk of dielectric fluid leakage to the surrounding environment.

[0006] In particular, when the housing is sealed with a welding device, the welding device may oxidize over time, resulting in the formation of rust spots, which may deteriorate the seal of the electrical device.

[0007] In other words, the degradation of these active components and the risk of dielectric fluid leakage, especially at the connectors between the active components and the electrical network, may increase over time, especially during the aging of the electrical equipment.

[0008] Dielectric fluid leaks cause a certain number of disadvantages, since they are not only detrimental to the electrical performance of the electrical equipment, causing high maintenance costs, but can also prove to be harmful to health and the environment.

[0009] Additionally, dielectric fluid leakage creates safety issues including the danger of flame propagation and acceleration in the event of a fire and housing rupture.

[0010] In order to overcome these drawbacks, solutions have been proposed which include completely coating the active components of the electrical device with a gellable composition or a polymerizable resin.

[0011] To this end, a method has been implemented which consists in introducing the active components of the electrical device into a housing and then pouring the gellable composition so as to completely fill the free space between the active components of the electrical device and the housing. Once the operation of filling the housing is completed, the gelling reaction is completely carried out at ambient temperature.

[0012] As a variant, a method is also implemented which consists in completely coating the active component of the electrical device in a polymerizable resin and then, once the polymerization is complete, introducing the assembly into the casing.

[0013] However, the electrical performance of the devices thus obtained has not proven to be entirely satisfactory. In particular, bubbles may form in the active components of the electrical devices, which may have a detrimental effect on their operation, reduce their dielectric strength and lead to poor impregnation of the films constituting the active components. Summary of the invention

[0015] In view of the foregoing, one of the objects of the present invention is therefore to prevent or even eliminate the risk of leakage of dielectric fluids in electrical devices, while maintaining satisfactory electrical performance.

[0016] In other words, one of the objects of the present invention is to propose an electrical device for which the risks of dielectric fluid leakage are minimized or even eliminated, even after ageing, while maintaining satisfactory electrical performances during its use.

[0017] In particular, the object of the invention is to propose an electrical device having good dielectric properties, in particular a satisfactory dielectric strength, which is also able to meet a certain number of standards, in particular hygienic, ecological and / or safety standards.

[0018] Therefore, a subject of the invention is in particular an electrical device comprising:

[0019] - a housing provided with a cavity, preferably a longitudinal cavity,

[0020] a coil comprising at least one dielectric fluid, preferably at least one combination of dielectric liquids and at least one material in gel form, said coil, at least one combination and at least one material in gel form being arranged inside said cavity,

[0021] - The maximum volume occupied by the material in gel form is less than 50% of the total volume of the cavity.

[0022] The electrical device according to the invention thus has satisfactory electrical performance and a reduced or even eliminated risk of dielectric fluid leakage, including after ageing thereof, in particular at increased DC voltages.

[0023] The electrical device according to the invention has in particular better electrical properties compared to an electrical device whose active components are dipped and / or immersed in a dielectric fluid are completely coated with a polymerizable resin or a gellable composition.

[0024] In particular, the risk of bubble formation during operation of the active components of the electrical device according to the invention is greatly reduced, or even eliminated, compared to electrical devices whose active components are completely coated with a polymerizable resin or a gellable composition.

[0025] Furthermore, the mechanical strength and sealing of the active components of the electrical device according to the invention have the advantage of being suitably protected from the surrounding environment.

[0026] In particular, the material in gel form enables effective protection of the most vulnerable areas of an electrical device while retaining the majority of the dielectric fluid inside the electrical device.

[0027] In particular, the material in gel form enables effective protection of the connections between active components of the electrical device and the electrical network, as well as the soldered parts of the electrical device.

[0028] Thus, the material in gel form enables effective control of thermal expansion within electrical equipment.

[0029] The material in gel form also makes it possible to reduce any thermal expansion phenomena induced by the surrounding environment on the active components of the electrical device; in particular, it also has the advantage of compensating for the thermal expansion and contraction of the dielectric fluid.

[0030] The electrical device according to the invention therefore has the advantage of being able to meet a certain number of standards, such as hygiene, ecological and / or safety standards, including after its aging at increased DC voltage, while ensuring satisfactory electrical performance, in particular while showing high dielectric properties, such as good dielectric strength, and better resistance to partial discharges.

[0031] Another subject of the invention is the use of a material in gel form for preventing and possibly eliminating leakage of a composition comprising at least one dielectric fluid in an electrical device as defined above.

[0032] Another subject of the invention is a method for producing an electrical device as described above.

[0033] Other subjects, features, aspects and advantages of the present invention will become more apparent from reading the following description and examples.

[0034] In the following, unless otherwise indicated, the limits of the numerical range are included in the range, especially in the expressions "between" and "ranging from to".

[0035] In addition, the expressions "at least one" and "at least" used in the present specification are equivalent to the expressions "one or more" and "greater than or equal to", respectively.

[0036] Electrical equipment

[0037] Electrical equipment refers to any type of electrical equipment, whether a transformer, an electrostatic storage device, an electrical power transmission element or an electrical connection element, such as power transformers, distribution transformers, traction transformers, measuring transformers, special transformers, circuit breakers, capacitors, shunts, bushings, load tap changers, etc., only mentioning the main electrical equipment or equipment including at least one dielectric fluid.

[0038] Preferably, the electrical device is selected from the group consisting of transformers, in particular measuring transformers, capacitors, bushings and on-load tap changers.

[0039] More preferably, the electrical device is selected from measuring transformers and capacitors, in particular capacitors, especially low-voltage capacitors, medium-voltage capacitors and high-voltage capacitors.

[0040] According to the invention, the coil, the composition comprising at least one dielectric fluid and the material in gel form are arranged in the cavity of the housing and the material in gel form occupies a maximum volume of less than 50% relative to the total volume of the cavity.

[0041] Preferably, the material in gel form occupies a maximum volume less than or equal to 40%, more preferably less than or equal to 30%, even more preferably less than or equal to 20% and more particularly less than or equal to 15%, relative to the total volume of the cavity of the housing.

[0042] In other words, the ratio between the maximum volume occupied by the material in gel form and the total volume of the cavity is less than 50%, preferably less than or equal to 40%, more preferably less than or equal to 30%, even more preferably less than or equal to 20%, and more particularly less than or equal to 15%.

[0043] Even more preferably, the material in gel form occupies a maximum volume less than or equal to 20%, more particularly less than or equal to 15%, relative to the total volume of the cavity.

[0044] The housing may have any type of geometric shape, preferably a cylindrical or rectangular shape.

[0045] The housing may be conductive or insulating and may be made of all types of materials.

[0046] The housing may be made of ceramics, such as porcelain, of a metallic material, in particular a ferrous metal, in particular steel or stainless steel, or a non-ferrous metal.

[0047] According to the invention, the cavity can have any type of geometry.

[0048] The cavity is therefore in particular a cavity which can have all types of geometries.

[0049] According to a general feature of the invention, the cavity may have at least one longitudinal portion.

[0050] According to a preferred feature of the invention, the cavity may consist of said longitudinal portion. In this case, the cavity is longitudinal.

[0051] Alternatively, the cavity may have other types of geometries, such as a U-shape.

[0052] In this case, the cavity has two longitudinal portions which are spaced apart from one another and are connected to one another via a transverse portion.

[0053] Advantageously, the cavity is a longitudinal cavity.

[0054] According to the present invention, one end of the cavity corresponds to a distal portion of the cavity, and the distal portion is open on at least one end surface of the housing to form an opening.

[0055] In other words, the cavity comprises at least one end, in particular one or two ends, which are open on at least one end face of the housing, thereby forming at least one opening, preferably one or two openings.

[0056] According to a preferred embodiment, the cavity has at least one longitudinal section which comprises at least one end which is open on at least one end face of the housing.

[0057] In other words, according to this embodiment, the cavity has at least one longitudinal section which is provided with at least one end which is open on at least one end face of the housing.

[0058] Preferably, the cavity is a longitudinal cavity comprising at least one end open on at least one end face of the housing.

[0059] Preferably, the cavity is a longitudinal cavity comprising one end which is open on an end face of the housing.

[0060] Preferably, the cavity is a longitudinal cavity comprising two ends open at two opposite end faces of the housing.

[0061] According to another embodiment, the cavity has a U-shape, i.e. has two longitudinal parts spaced apart from each other and connected to each other by a transverse part, and comprises two ends open on the same end face of the shell, thereby forming two openings appearing side by side on the same end face of the shell.

[0062] In particular, in this case, each longitudinal part comprises one end which is open on the same end face of the housing.

[0063] Advantageously, the material in gel form is located at least at least at one end of the cavity, which enables more effective protection of the mechanical strength and sealing of the coil, in particular the active parts of the electrical device relative to the surrounding environment, and further reduces the risks of dielectric fluid leakages, or even eliminates them.

[0064] Preferably, the material in gel form is located at least at least one end of the cavity, more preferably at least both ends of the cavity.

[0065] Preferably, the material in gel form is located at least at least one end of the longitudinal cavity, more preferably at both ends of the longitudinal cavity.

[0066] In other words, the material in gel form is distributed, in particular within the electrical device according to the invention, in at least one end of the cavity, preferably at one end or both ends of the longitudinal cavity.

[0067] In particular, at least 10 wt. %, or at least 50 wt. %, or at least 90 wt. %, or at least 92 wt. %, or at least 94 wt. %, or at least 96 wt. %, or at least 98 wt. % of the total weight of the material in gel form is located at at least one of the ends of the cavity, preferably at least at both ends of the longitudinal cavity.

[0068] Preferably, the material in gel form is located between at least one end surface of the housing and the dielectric fluid.

[0069] Preferably, the material in gel form is not in contact with the coil.

[0070] The electrical device according to the invention therefore has the advantage of limiting the contact between the coil and the material in gel form.

[0071] In this way, the risk of air bubbles forming within the coil, which could prevent the proper functioning of the electrical device, is reduced or even eliminated.

[0072] Advantageously, the material in gel form at least at one of the ends of the longitudinal cavity of the housing, preferably at both ends of the longitudinal cavity of the housing, is not in contact with the coil.

[0073] According to one embodiment, the material in gel form may be at least partially located between the composition comprising at least one dielectric fluid and the pores of the cavity, that is to say, between the composition comprising at least one dielectric fluid and the inner surface of the cavity. In this case, the material in gel form particularly adheres to the pores of the cavity.

[0074] In this way, the material in gel form may be sandwiched at least in position between the composition comprising at least one dielectric fluid and the pores of the cavity.

[0075] The layer of material in gel form partially sandwiched between the pores of the cavity and the composition comprising at least one dielectric fluid may in particular have a thickness of at least 100 μm, preferably ranging from 100 to 20000 μm, in particular ranging from 1000 to 10000 μm.

[0076] According to this embodiment, the material in gel form may be located at one of the ends of the cavity, preferably at one or both ends of the longitudinal cavity, and may additionally be partially or completely sandwiched between the composition comprising at least one dielectric fluid and the pores of the cavity.

[0077] In addition, according to this embodiment, the chemical properties of the material in gel form can be different when the material in gel form is positioned on one of the distal portions of the cavity and when the material in gel form is positioned between the hole in the cavity and the dielectric fluid. Preferably, the chemical properties are the same when it is positioned on one of the distal portions of the cavity and when it is positioned between the hole in the cavity and the composition comprising at least one dielectric fluid.

[0078] In addition, according to this embodiment, at least 50 weight %, or at least 90 weight %, or at least 92 weight %, or at least 94 weight %, or at least 96 weight %, or at least 98 weight %, or at least 99 weight % of the total weight of the material in gel form may be located at at least one end of the cavity, preferably at one end or both ends of the longitudinal cavity, and 50 weight % or less, or 10 weight % or less, or 8 weight % or less, or 6 weight % or less, or 4 weight % or less, or 2 weight % or less, or 1 weight % or less of the total weight of the material in gel form is partially located between the composition comprising at least one dielectric fluid and the pores of the cavity.

[0079] According to a preferred embodiment, the composition comprising at least one dielectric fluid is at least partially in direct contact with the cavity, preferably with the pores of the cavity.

[0080] In other words, the composition comprising at least one dielectric fluid is in direct contact with the cavity at least in places, ie the dielectric fluid has one or more contact surfaces with the cavity, in particular with the pores of the cavity.

[0081] Thus, at these contact surfaces, the composition comprising at least one dielectric fluid is not separated from the cavity by the material in gel form according to the invention.

[0082] According to an advantageous embodiment, the composition comprising at least one dielectric fluid is in direct and complete contact with the pores of the cavity.

[0083] The electrical device thus obtained has particularly improved electrical properties while preventing leakage of the dielectric fluid, making it the most reliable from an ecological, hygienic and safety point of view (especially in the event of a fire).

[0084] Preferably, the cavity is longitudinal and the material in gel form is located at one of the ends of the cavity, preferably at both ends of the cavity.

[0085] More preferably, the gel-form material is located at one of the ends of the longitudinal cavity, preferably at both ends of the longitudinal cavity, and the composition including at least one dielectric fluid is in full direct contact with the aperture of the longitudinal cavity (i.e., with the inner surface of the longitudinal cavity of the housing).

[0086] In other words, over the entire inner surface of the cavity, the composition comprising at least one dielectric fluid is not separated from the cavity by the space filled with the material in gel form according to the invention.

[0087] Preferably, the gel form material is located at at least one end of the cavity, preferably at one or both ends of the longitudinal cavity, and may be in any form suitable for preventing leakage of the dielectric fluid and may have a thickness in the range of 1 to 100 mm, preferably in the range of 5 to 50 mm.

[0088] Advantageously, the material in gel form takes the form of a plug which may have a thickness in the range 1 to 100 mm, preferably in the range 5 to 50 mm.

[0089] Alternatively, the cavity has a U-shape. In this case, the cavity has two longitudinal portions spaced apart from each other and connected to each other by a transverse portion, and comprises two ends open on the same end face of the housing, and the material in gel form is located at least at one of the ends of the cavity, preferably at both ends of the cavity.

[0090] Preferably, in the cavity, the material in gel form occupies less than or equal to 30% of the maximum volume and the composition comprising at least one dielectric fluid, preferably a dielectric liquid, occupies greater than or equal to 70% of the volume.

[0091] More preferably, in the cavity, the material in gel form occupies less than or equal to 20% of the maximum volume and the composition comprising at least one dielectric fluid, preferably a dielectric liquid, occupies greater than or equal to 80% of the volume.

[0092] In the context of the present invention, a coil corresponding to an active component of the electrical device positioned inside the cavity of the housing may be impregnated with and / or immersed (ie, bathed) in at least one dielectric fluid.

[0093] According to a preferred feature of the invention, the coil is immersed in at least one dielectric fluid.

[0094] According to another preferred feature, the coil is impregnated with at least one dielectric fluid by means of an impregnation process which can be carried out before or after the coil is introduced into the cavity of the housing, that is to say therefore inside or outside the cavity.

[0095] According to another preferred feature, the coil is first impregnated with at least one dielectric fluid and then immersed in at least one dielectric fluid inside the cavity of the housing. In other words, the coil can be impregnated with at least one dielectric fluid outside the housing by means of an impregnation process, and then, once the impregnation is complete, the coil can then be immersed in at least one dielectric fluid filling the cavity of the housing. In this case, the dielectric fluids used for impregnation and immersion can be the same or different, preferably the same.

[0096] According to a general characteristic, the material in gel form is immiscible with the composition comprising the dielectric fluid.

[0097] For purposes of the present invention, the material in gel form and the composition comprising the dielectric fluid are separate and immiscible with each other.

[0098] For the purposes of the present invention, the term "immiscible" is understood to mean that the material in gel form has a solubility of less than 0.1 wt% in a composition comprising a dielectric fluid in the temperature range of -60 to 150°C, preferably -30 to 120°C.

[0099] The material in gel form may have a dielectric constant having a value less than or equal to 10, preferably less than or equal to 6, more preferably less than or equal to 4.

[0100] The material in gel form may have heat resistance in a temperature range of 50 to 200°C, particularly in a temperature range of 40 to 90°C.

[0101] Preferably, the material in gel form is a resin selected from the group consisting of silicone resin, polyurethane resin, polyester resin, polystyrene resin, polyethylene resin and mixtures thereof.

[0102] More preferably, the gel-form material is a resin selected from the group consisting of silicone resins, polyurethane resins and mixtures thereof.

[0103] Even more preferably, the material in gel form is a resin chosen from silicone resins.

[0104] For the purposes of the present invention, silicone is understood to mean any organosilicon polymer or oligomer of variable molecular weight obtained by polymerization and / or polycondensation of silanes, comprising at least one repeating unit in which silicon atoms are linked to one another via oxygen atoms (siloxane bond -Si-O-Si-).

[0105] The siloxane may be silicone, polysilane, polysilazane, polycarbosilane or polysilphenylene prepolymer.

[0106] Preferably, the material in gel form is silicone having a cone penetration measured according to standard ISO 2137 at a temperature of 25° C. in the range of 2 to 500 mm / 10, in particular in the range of 5 to 350 mm / 10.

[0107] Preferably, the material in gel form is a silicone resin, in particular made from a two-component mixture comprising component A and component B.

[0108] More preferably, the material in gel form is a silicone resin made from a mixture of two components in a weight ratio of 1 / 1, sold under the trade name BLUESIL ESA 6018-01A+BLUESIL ESA 6018-01B, notably having a viscosity of 530 mPa.s at a temperature of 23°C measured according to standard ISO 3219.

[0109] According to a general feature of the invention, the material in gel form and the composition comprising at least one dielectric fluid are in particular different, in particular the composition comprising at least one dielectric fluid is not in the form of a phase dispersed in the material in gel form.

[0110] For the purposes of the present invention, the term "dielectric fluid" means a fluid that does not conduct electricity (or conducts electricity only slightly) but allows the application of electrostatic forces.

[0111] According to a general feature of the invention, the dielectric fluid may be a dielectric gas, a dielectric liquid, or a mixture of a dielectric gas and a dielectric liquid.

[0112] Preferably, the dielectric fluid is a dielectric liquid.

[0113] The dielectric liquid may have a range of 1 to 51 mm measured at a temperature of 40° C. according to standard ISO 3104. 2 .s -1 , preferably in the range of 1 to 35 mm 2 .s -1 kinematic viscosity.

[0114] The dielectric fluid may be chosen from mineral oils, synthetic oils, in particular aromatic hydrocarbons, aliphatic hydrocarbons, silicone oils and synthetic esters, vegetable oils and natural esters, and mixtures thereof.

[0115] The synthetic oil is preferably selected from the group consisting of aromatic hydrocarbons, aliphatic hydrocarbons, silicone oils, synthetic esters and mixtures thereof.

[0116] Among the aromatic hydrocarbons, mention may in particular be made of alkylbenzenes, alkyldiphenylethanes such as phenylxylylethane (PXE), phenylethylphenylethane (PEPE), monoisopropylbiphenyl (MIPB), 1,1-diphenylethane (1,1-DPE), alkylnaphthalenes such as diisopropylnaphthalene (DIPN), methylpolyarylmethanes such as benzyltoluene (BT) and dibenzyltoluene (DBT), and mixtures thereof.

[0117] In the aromatic hydrocarbons, it is understood that at least one ring is aromatic and, optionally, one or more other rings present may be partially or fully unsaturated.

[0118] Among the aliphatic hydrocarbons, mention may especially be made of poly(alpha)olefins (PAOs), such as polyisobutylene (PIB) or olefins of vinylidene type, such as those sold, for example, by Soltex Inc.

[0119] Among the silicone oils, mention may be made in particular of linear silicone oils of the polydimethylsiloxane type, for example those marketed by Wacker under the trade name The ones that AK sells.

[0120] Among the synthetic esters, mention may especially be made of esters of the phthalic acid type, in particular alkyl phthalates, such as dioctyl phthalate (DOP) or diisononyl phthalate (DINP), sold for example by BASF.

[0121] Mention may also be made of esters produced by the reaction between a polyol and an organic acid, in particular an acid selected from saturated or unsaturated C4 to C22 organic acids. As non-limiting examples of such organic acids, mention may be made of undecanoic acid, heptanoic acid, octanoic acid, palmitic acid and mixtures thereof. Among the polyols that may be used to synthesize the above-mentioned esters, a non-limiting example that may be mentioned includes pentaerythritol.

[0122] Thus, synthetic esters resulting from the reaction between a polyol and an organic acid are e.g. Series of products, such as 7131, or series of products, such as those from M&I Materials DFK and DF7, or an ester from the Nycodiel series from Nyco.

[0123] Among the natural esters and vegetable oils, mention may in particular be made of the products resulting from oilseeds or other natural sources. By way of example and in a non-limiting manner, mention may be made of FR 3 sold by Cargill. TM or Envirotemp TM , or the Midel eN 1215 sold by M&I Manufacturers.

[0124] Among the vegetable oils, mention may also be made of rapeseed oil, corn oil, castor oil and soybean oil, and mixtures thereof.

[0125] Among the mineral oils, mention may especially be made of the paraffinic and naphthenic oils, such as the dielectric oils of the Nytro family sold by Nynas (in particular Nytro Taurus, Nytro Libra, Nytro 4000X and Nytro 10XN) and of the Diala family sold by Shell.

[0126] Preferably, the dielectric fluid is free of esters of the phthalic acid type, in particular alkyl phthalates, such as dibutyl phthalate and dioctyl phthalate.

[0127] Preferably, the dielectric fluid is a synthetic oil, in particular chosen from aromatic hydrocarbons.

[0128] Advantageously, the dielectric fluid is selected from methylpolyarylmethanes.

[0129] More advantageously, the dielectric fluid is chosen from a mixture based on benzyltoluene and, other than benzyltoluene, one or more aromatic compounds as described above, in particular dibenzyltoluene or 1,1-diphenylethane.

[0130] More advantageously, the dielectric fluid is a mixture comprising benzyltoluene and one or more aromatic compounds as described above, in particular dibenzyltoluene or 1,1-diphenylethane, other than benzyltoluene; benzyltoluene being present in a concentration greater than or equal to 30% by weight, preferably greater than or equal to 40% by weight, more preferably greater than or equal to 50% by weight, even more preferably greater than or equal to 60% by weight, relative to the total weight of the mixture.

[0131] More preferably, the mixture of benzyltoluene and dibenzyltoluene comprises from 70 to 85% by weight of benzyltoluene and from 15 to 30% by weight of dibenzyltoluene, relative to the total weight of the benzyltoluene / dibenzyltoluene mixture.

[0132] Even more preferably, the mixture of benzyltoluene and dibenzyltoluene comprises from 70 to 80% by weight of benzyltoluene and from 20 to 30% by weight of dibenzyltoluene, relative to the total weight of the benzyltoluene / dibenzyltoluene mixture.

[0133] The composition may also include one or more additives and / or fillers well known to those skilled in the art and, for example, selected in a non-limiting manner from antioxidants, passivators, pour point depressants (pour point depressants), decomposition inhibitors, aromas and flavorings, colorants, preservatives, and the like, and mixtures thereof.

[0134] Among the antioxidants that can be advantageously used, mention may be made, as non-limiting examples, of phenolic antioxidants such as butylated hydroxytoluene, butylated hydroxyanisole, tocopherol, and the acetates of these phenolic antioxidants, as well as amine antioxidants such as phenyl-α-naphthylamine, diamine antioxidants such as N,N′-di-(2-naphthyl)-p-phenylenediamine, and ascorbic acid and its salts, esters of ascorbic acid, alone or as a mixture of two or more thereof or in mixtures with other components such as green tea extract or coffee extract.

[0135] Very particularly suitable antioxidants are available from Brenntag under the trade name Commercially available antioxidants.

[0136] The passivating agent that can be used as additive in the composition that can be used within the scope of the present invention is of any type known to a person skilled in the art and is advantageously chosen from triazole derivatives, benzimidazoles, imidazoles, thiazoles or benzothiazoles. As examples and in a non-limiting manner, mention may be made of dioctylaminomethyl-2,3-benzotriazole and 2-dodecyldithioimidazole.

[0137] Among the pour point depressants that may be present in the compositions that can be used within the scope of the invention, mention may be made, by way of non-limiting examples, of sucrose fatty acid esters or acrylic acid polymers, such as poly(alkyl methacrylates) or poly(alkyl acrylates).

[0138] The preferred acrylic polymer is a polymer having a molecular weight of 50,000 g mol -1 Up to 500000 g mol -1 Examples of these acrylic polymers include polymers that may contain a linear alkyl group including 1 to 20 carbon atoms.

[0139] Among them, mention may be made, still as non-limiting examples, of poly(methyl acrylate), poly(methyl methacrylate), poly(heptyl acrylate), poly(heptyl methacrylate), poly(nonyl acrylate), poly(nonyl methacrylate), poly(undecy acrylate), poly(undecy methacrylate), poly(tridecyl acrylate), poly(tridecyl methacrylate), poly(pentadecyl acrylate), poly(pentadecyl methacrylate), poly(heptadecyl acrylate) and poly(heptadecyl methacrylate).

[0140] Examples of such pour point depressants are commercially available from Sanyo Chemical Industries Ltd under the trade name Aclube.

[0141] According to a very particularly preferred aspect, the composition according to the invention comprises at least one decomposition inhibitor as additive.

[0142] The decomposition inhibitor may be of any type known to the person skilled in the art and may in particular be chosen from carbodiimide derivatives, for example diphenylcarbodiimide, xylylcarbodiimide, bis(isopropylphenyl)carbodiimide or bis(butylphenyl)carbodiimide, but may also be chosen from phenyl glycidyl ethers or esters, alkyl glycidyl ethers or esters, 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, compounds of the anthraquinone family, for example β-methylanthraquinone sold under the name “BMAQ”, epoxide derivatives, for example vinylcyclohexene diepoxide, 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylhexanecarboxylate, phenol novolac type epoxy resins, bisphenol A diglycidyl ether epoxides, for example BADGE or CEL 2021P, in particular available from Whyte Chemicals.

[0143] The additive or additives optionally present in the composition according to the invention may be present in an amount ranging from 0.0001% to 5%, preferably from 0.001% to 3%, more preferably from 0.01% to 2%, by weight, relative to the total weight of the composition.

[0144] Preferably, the composition according to the invention comprises a mixture of benzyltoluene and one or more aromatic compounds as defined above other than benzyltoluene, in particular dibenzyltoluene or 1,1-diphenylethane, in particular marketed by Arkema under the trade name C101 and C101D is sold as SAS by JX Nippon ChemicalTexas Inc. sell.

[0145] Advantageously, the material in gel form is a resin chosen from silicone resins and the composition comprises a mixture of benzyltoluene and one or more aromatic compounds as defined above, other than benzyltoluene, in particular dibenzyltoluene or 1,1-diphenylethane, benzyltoluene being present in a mass concentration greater than or equal to 30% by weight, preferably greater than or equal to 40% by weight, more preferably greater than or equal to 50% by weight, even more preferably greater than or equal to 60% by weight, relative to the total weight of the mixture.

[0146] According to the invention, the term "coil" is understood to mean any assembly of a plurality of layers connected to one another alternately in succession (sequentially, in sequence) between electronically conductive layers and electronically insulating layers, in particular any winding or stack.

[0147] The electronically conductive layer is in particular a metal layer, for example an aluminum or copper layer, or a doubly metallized paper sheet. Preferably, the electronically conductive layer is an aluminum sheet.

[0148] The electronically insulating layer may be selected from paper, polyolefins, in particular polypropylene, polyester or mixtures thereof.

[0149] Preferably, the electronically insulating layer is a polyolefin layer, in particular a polypropylene layer.

[0150] Preferably, the coil is an assembly, in particular a winding, of an aluminium layer and a polyolefin layer, in particular a polypropylene layer.

[0151] Advantageously, the coil is an assembly of successive alternations between layers of aluminium and layers of polyolefins, in particular polypropylene, impregnated with at least one dielectric fluid, in particular chosen from a mixture of benzyltoluene and one or more aromatic compounds as defined above, other than benzyltoluene, in particular dibenzyltoluene or 1,1-diphenylethane, more precisely those mentioned above.

[0152] The coils may be wrapped in paper or kraft type paperboard.

[0153] According to an advantageous embodiment, the invention relates to a capacitor or a transformer, in particular a measuring transformer, comprising:

[0154] - a housing provided with a cavity, preferably a longitudinal cavity,

[0155] a coil, at least one composition comprising at least one dielectric fluid, preferably a dielectric liquid, and at least one material in gel form, said coil, at least one composition and said material in gel form being arranged inside said cavity,

[0156] - the maximum volume occupied by the material in gel form is less than 50%, preferably less than or equal to 40%, preferably less than or equal to 30%, more preferably less than or equal to 20%, even more preferably less than or equal to 15% of the total volume of the cavity.

[0157] According to this embodiment, the dielectric fluid is advantageously a mixture of benzyltoluene and one or more aromatic compounds as defined above other than benzyltoluene, in particular dibenzyltoluene or 1,1-diphenylethane, and the material in gel form is a silicone resin.

[0158] According to one embodiment, the present invention relates to an electrical device, comprising:

[0159] - a housing provided with a cavity, preferably a longitudinal cavity,

[0160] - at least one coil and at least one composition comprising at least one dielectric fluid, said coil and said composition being arranged inside said cavity,

[0161] - at least one plug formed of a material in gel form;

[0162] The electrical device further comprises a material in the form of a gel, said material being interposed between the composition comprising at least one dielectric fluid and the aperture of the cavity and being spaced apart from said plug.

[0163] According to this advantageous embodiment, the material in gel form interposed between the composition comprising the dielectric fluid and the pores of the cavity may be identical to or different from the material in gel form forming the plug, preferably identical.

[0164] According to this embodiment, the electrical device, the composition including the dielectric fluid, the coil and the cavity are as described above.

[0165] According to this embodiment, the material in gel form occupies less than 50% of the maximum volume relative to the total volume of the cavity.

[0166] According to this embodiment, the electrical device is preferably a capacitor or a transformer, in particular a measuring transformer.

[0167] According to an advantageous embodiment, the electrical device comprises:

[0168] - a housing provided with a cavity, preferably a longitudinal cavity, as described above,

[0169] a coil and at least one composition comprising at least one dielectric fluid, said coil and said composition being arranged in a cavity, as described above; at least the composition comprising said dielectric fluid being at least partially in direct contact with said cavity,

[0170] - A material in gel form, as described above, arranged inside the cavity and at least at one of the ends of said cavity.

[0171] According to this advantageous embodiment, the composition comprising the dielectric fluid shares at least one contact surface with the cavity, in particular at least with the pores of the cavity.

[0172] Preferably, according to this advantageous embodiment, the composition comprising the dielectric fluid is completely in direct contact with the pores of the cavity, ie in direct contact with one of the inner surfaces of the cavity.

[0173] According to this embodiment, the electrical device, the composition including the dielectric fluid, the coil and the cavity are as described above.

[0174] Preferably, according to this embodiment, the material in gel form occupies less than 50% of the maximum volume relative to the total volume of the cavity.

[0175] use

[0176] The invention also relates to the use of a material in gel form to prevent and possibly eliminate leakage of a composition comprising at least one dielectric fluid as defined above, in an electrical device as defined above.

[0177] In particular, the electrical device is a transformer, in particular a measuring transformer, or a capacitor.

[0178] In other words, the present invention relates to the use of a material in gel form to prevent and possibly eliminate leakage of a composition comprising at least one dielectric fluid, within an electrical device as defined above.

[0179] In other words, the present invention relates in particular to the use of a material in gel form to prevent and possibly eliminate leakage of a composition comprising at least one dielectric fluid in an electrical device comprising:

[0180] - a housing provided with a cavity, preferably a longitudinal cavity,

[0181] a coil and at least one composition comprising at least one dielectric fluid, preferably a dielectric liquid, said coil and said composition being arranged inside said cavity,

[0182] The material in the gel form is disposed within the cavity and occupies a maximum volume that is less than 50% of the total volume of the cavity.

[0183] method

[0184] Another subject of the invention is a method for producing an electrical device as described above.

[0185] Preferably, the method comprises:

[0186] - at least one step of inserting a coil as described above into the cavity of the housing,

[0187] - optionally, at least one step of impregnating said coil with a composition comprising at least one dielectric fluid as described above,

[0188] - at least one step of filling said cavity with a gellable composition,

[0189] - at least one step of gelling the gelable composition to obtain a material in gel form as described above;

[0190] The maximum volume occupied by the material in gel form is less than 50% of the total volume of the cavity.

[0191] More preferably, the method comprises:

[0192] - at least one step of inserting a coil as described above into the cavity of the housing,

[0193] - at least one step of impregnating said coil with a composition comprising at least one dielectric fluid as described above,

[0194] - at least one step of filling said cavity with a gellable composition,

[0195] - at least one step of gelling the gelable composition to obtain a material in gel form as described above;

[0196] The maximum volume occupied by the material in gel form is less than 50% of the total volume of the cavity.

[0197] The step of impregnating the coil may be performed before or after the step of inserting said coil into the cavity of the housing, preferably after the insertion step.

[0198] The gelling step may be carried out at a temperature ranging from 5°C to 70°C, preferably from 23°C to 70°C.

[0199] The step of filling the cavity with the gelable composition may be performed before the step of inserting the coil into the cavity, or after gelling the composition.

[0200] The filling step may comprise one or more, preferably one or two, steps of filling the cavity with the gellable composition.

[0201] The filling step may include depositing the gellable composition on at least one end of the cavity and / or partially or fully on the bore of the cavity.

[0202] Preferably, the method comprises:

[0203] i) at least one step of partially filling the cavity of said shell with a gellable composition,

[0204] ii) at least one step of gelling the gelable composition to obtain a material in gel form as described above,

[0205] iii) at least one step of inserting a coil as described above into a cavity of a housing,

[0206] iv) at least one step of impregnating the coil with a composition comprising at least one dielectric fluid as described above,

[0207] v) at least one step of filling the remainder of the shell cavity with the gellable composition,

[0208] vi) at least one step of gelling the gellable composition added in step v) to obtain a material in gel form as described above;

[0209] The maximum volume occupied by the material in gel form is less than 50% of the total volume of the cavity.

[0210] The partial filling step i) may comprise depositing the gellable composition on at least one end of the cavity and / or partially or completely on the bore of the cavity.

[0211] The gelling step ii) may be carried out at a temperature ranging from 5°C to 70°C, preferably from 23°C to 70°C.

[0212] The impregnation step iv) may be performed before or after the step iii) of inserting the coil into the cavity of the housing, preferably after the step iii).

[0213] The impregnation step may, for example, comprise:

[0214] - a step of impregnating the coil with a composition comprising a dielectric fluid at a temperature that may range from 5°C to 100°C, preferably from 23°C to 100°C, under reduced pressure for a period of time that may range from 48 hours to 200 hours, preferably from 48 hours to 150 hours,

[0215] - This may be followed by a step of cooling the coil to ambient temperature, for example to a temperature of 23°C.

[0216] The filling step v) may comprise depositing the gellable composition over the entire hole and / or on at least one end of the cavity other than the end of step i).

[0217] Other features and advantages of the invention will become more apparent from a detailed examination of the embodiments by means of a non-limiting example of an electrical device according to the invention and illustrated by means of the accompanying drawings, in which Figure 1 A cross-sectional view of a capacitor according to the present invention is shown. BRIEF DESCRIPTION OF THE DRAWINGS

[0218] As shown in the individual figures, the electrical device extends along a longitudinal general axis XX'. Figure 1 In FIG. 1 , the electrical device 1 is shown in a supposedly horizontal position.

[0219] As a variant, the electrical device 1 can also be in a vertical position.

[0220] The electrical device 1 comprises a housing 3, which is schematically shown here. The housing 3 may be electrically insulating, for example made of a ceramic material, such as porcelain, or electrically conductive, for example made of a metallic material, in particular a ferrous metal.

[0221] Shell 3 Figure 1 It is shown as a rectangular shape, but it can have any type of geometric shape.

[0222] The housing 3 is provided with a longitudinal cavity 5. In the exemplary embodiment shown, the cavity 5 is through in the axial direction. The cavity 5 has two ends 5a and 5b, which are open on the end faces 3a, 3b of the housing 3, respectively, thereby forming two openings.

[0223] Alternatively, the cavity 5 may not be through-going. In this case, the cavity 5 has a single end that is open only on one of the two end faces 3 a, 3 b of the housing 3 .

[0224] As another alternative, the cavity 5 has a U-shape. In this case, the cavity 5 has two longitudinal portions spaced apart from each other and connected to each other by a transverse portion, and comprises two ends 5a and 5b open on the same end faces 3a and 3b of the housing 3 .

[0225] The electrical device 1 further comprises a coil 7 arranged inside the cavity 5 and immersed in a composition 9 comprising a dielectric fluid.

[0226] As a variant, the coil 7 may be impregnated with the composition 9 on some or all of its surface by an impregnation process that can be carried out before or after the introduction of the coil 7 into the cavity 5 of the housing 3 , that is to say therefore inside or outside the cavity 5 .

[0227] As another variant, the coil 7 may first be impregnated with the composition 9 on all or part of its surface outside the cavity 5 by an impregnation process, and then the coil 7 may be inserted into the cavity 5 previously filled with the composition 9 .

[0228] The impregnation process may, for example, include:

[0229] - a step of impregnating the coil 7 with the composition 9 under reduced pressure at a temperature that may range from 5°C to 100°C, preferably from 23°C to 100°C, for a period of time that may range from 48 hours to 200 hours, preferably from 48 hours to 150 hours,

[0230] - The coil 7 can then be cooled to a temperature of 23°C.

[0231] As mentioned above, the coil 7 is preferably a winding alternating continuously between layers of aluminium and layers of polyolefin, for example consisting of alternating continuous sheets of aluminium and sheets of polyolefin, in particular polypropylene.

[0232] As mentioned above, the composition 9 comprises a dielectric fluid, which is preferably a dielectric liquid and is advantageously a mixture of benzyltoluene and one or more aromatic compounds as defined above other than benzyltoluene, in particular dibenzyltoluene or 1,1-diphenylethane.

[0233] Advantageously, composition 9 is available from Arkema under the trade name C101 and C101D or sold by JXNippon Chemical Texas Inc under the trade name SAS sell.

[0234] like Figure 1 As shown, the composition 9 is arranged in full direct contact with the hole of the cavity 5 .

[0235] In other words, the composition 9 is not separated from the pores of the cavity 5 by empty spaces or free (open) spaces.

[0236] The electrical device 1 further comprises a material 12 in the form of a gel which is immiscible with the composition 9. The material 12 is different from the composition 9. The material 12 is preferably selected from silicone resins, polyurethane resins, polyester resins, polystyrene resins and polyethylene resins and mixtures thereof.

[0237] Advantageously, the material 12 in gel form is a resin chosen from silicone resins, polyurethane resins and mixtures thereof.

[0238] More preferably, the material 12 in gel form is selected from silicone.

[0239] A material 12 in gel form is arranged in the cavity 5 of the housing. The material 12 in gel form is in contact with the pores of the cavity 5.

[0240] As shown in the individual figures, the material 12 in gel form occupies a maximum volume less than or equal to 20% relative to the total volume of the cavity 5. In other words, the ratio between the maximum volume occupied by the material 12 in gel form and the total volume of the cavity is less than or equal to 20%.

[0241] According to the invention, the material 12 in gel form may also occupy a greater volume in the cavity 5 , in particular a maximum volume of less than 50% relative to the total volume of the cavity 5 .

[0242] As shown in the single figure, the material 12 in gelled form is located at each end 5a and 5b of the cavity 5. In particular, the material 12 is located between the two end faces 3a and 3b of the housing 3 and the composition 9. In this example, the material 12 in gelled form thus takes the form of two blocks or plugs 12a, 12b. Thus, the material 12 in gelled form blocks the cavity 5.

[0243] The inner surface of each plug 12 a , 12 b formed of a material 12 in gel form is in contact with the composition 9 .

[0244] In particular, the material 12 is not in contact with the coil 7 , ie with the active components of the electrical device 1 .

[0245] The positioning of the material 12 thus makes it possible to effectively prevent leakage of the composition 9 comprising the dielectric fluid and ensure protection of the coil 7 with respect to the external environment, in particular the mechanical strength and sealing of the coil 7 are effectively maintained, including during aging of the electrical device 1 .

[0246] exist Figure 1 In the embodiment, the material 12 is positioned at both ends 5a and 5b of the longitudinal cavity 5, but as a variation, the material 12 may be positioned only at one of the ends of the cavity 5, in particular when the cavity 5 has only one end, which is open only on one end face 5a or 5b, thereby forming an opening.

[0247] The positioning of the material 12 makes it possible to prevent the risk of the material 12 coming into contact with the coil 7 , thereby minimizing the formation of air bubbles.

[0248] The electrical device 1 further comprises closing devices 15, each of which is fastened to one end of the housing. The closing devices 15 are separate from the material 12. The closing devices 15 are removably fastened to the housing by any suitable means, here using threads.

[0249] Therefore, the electrical device 1 according to the invention has improved electrical properties, in particular good dielectric strength and better resistance to partial discharges.

[0250] Furthermore, the risk of dielectric fluid leakage in the electrical device 1 is reduced or even eliminated, including after ageing thereof, in particular at increased DC voltages.

[0251] The following examples serve to illustrate the invention but are not limiting in nature. Example

[0252] 1. Check the tightness of the gel

[0253] Use 5mL C101 fills a clear glass test tube, and then fills a clear glass test tube with 1 mL Bluesil ESA6018-01A + 1 mL Bluesil ESA 6018-01B (two products sold by ELKEM) to form a silicone gel. The test tube is then placed in an oven at 40°C for 3 hours. At the end of this step, the tube can be inverted without any liquid flowing.

[0254] 2. Determination of dielectric properties of a thin film capacitor according to an embodiment of the present invention.

[0255] Description of Film Capacitor Production

[0256] The coils are made of a crude polypropylene film of type PP2MAR 8.3 sold by BOLLORE Films Plastiques.

[0257] The housing used is a 250 cm2 enclosure at both ends. 3 Cylindrical shell.

[0258] Two capacitors are created.

[0259] In the first case (housing No. 1 - invention), the housing is kept in a vertical (upright) position and then filled with 8 g of BLUESIL ESA 6018-01A and 8 g of BLUESIL ESA 6018-01B so as to form a gel layer in the lower part of the housing, i.e. at the bottom of the housing. The gelling is carried out at ambient temperature (i.e. a temperature of 23° C.) for a period of 20 hours.

[0260] The coil was then placed in the housing containing the gel layer at the bottom of the housing and heated with 200 g of C101 was subjected to an impregnation step for 5 days. At the end of this step and after cooling to ambient temperature, the gel component was added in a ratio of 8 g Bluesil ESA 6018-01A and 8 g Bluesil ESA 6018-01B to allow an impermeable gel to form on the surface. The housing was then closed. Gelation was carried out at ambient temperature for 20 hours.

[0261] The dissipation factor (tan δ) can then be measured.

[0262] In the second case (shell number 2 - comparison), at 90°C The coils were impregnated with C101 for 5 days, at the end of this step the excess was removed before placing the coils in the housing. The shell was then completely filled with 116 g of Bluesil ESA 6018-01A and 116 g of Bluesil ESA 6018-01B. Gelation was carried out at ambient temperature for 20 hours.

[0263] The dissipation factor (tan δ) can then be measured.

[0264] The results of tan δ measurements were then carried out at 20° C. and are shown in the table below. The values ​​obtained with shell No. 1 (value less than 0.001 after 60 minutes) are excellent and significantly better than those obtained with shell No. 2.

[0265] [Table 1]

[0266]

Claims

1. Electrical equipment, including: - a housing (3) provided with a cavity (5), - a coil (7) and at least one composition (9) comprising at least one dielectric fluid, said coil and said composition being arranged in said cavity (5); - a material (12) in gel form, arranged in the cavity (5) and occupying a maximum volume less than 50% of the total volume of the cavity (5).

2. The electrical device (1) according to claim 1, wherein the electrical device (1) is selected from the group consisting of transformers, in particular measuring transformers, capacitors, bushings and on-load tap changers, preferably measuring transformers and capacitors.

3. An electrical device (1) according to claim 1, wherein the maximum volume occupied by the material (12) in gel form is less than or equal to 40% of the total volume of the cavity (5), preferably less than or equal to 30% of the total volume of the cavity (5), more preferably less than or equal to 20% of the total volume of the cavity (5), more particularly less than or equal to 15% of the total volume of the cavity (5).

4. The electrical device (1) according to any of the preceding claims, wherein the material (12) in gel form is located at least at at least one end of the cavity (5), preferably at at least two ends of the cavity (5).

5. The electrical device (1) according to any one of the preceding claims, wherein the material (12) in gel form is not in contact with the coil (7).

6. Electrical device (1) according to any of the preceding claims, wherein the material (12) in gel form is at least partially located between the composition (9) comprising at least one dielectric fluid and the pores of the cavity (5).

7. The electrical device (1) according to any of the preceding claims, wherein the composition (9) comprising a dielectric fluid is at least partially in direct contact with the cavity (5), preferably completely in direct contact with the aperture of the cavity (5).

8. An electrical device (1) according to any of the preceding claims, wherein the cavity (5) includes a longitudinal portion, the longitudinal portion including at least one end (5a, 5b) open on at least one of the end faces (3a, 3b) of the housing (3), and the material (12) in gel form is located at least at least at least one end (5a, 5b) of the cavity (5), preferably at at least two ends (5a, 5b) of the cavity (5).

9. An electrical device (1) according to any one of the preceding claims, wherein a material (12) in gel form is located between one of the end faces (3a, 3b) of the housing (3) and the composition comprising the dielectric fluid (9).

10. The electrical device (1) according to any one of the preceding claims, wherein the material (12) in gel form is immiscible with the composition (9) comprising the dielectric fluid.

11. The electrical device (1) according to any one of the preceding claims, wherein the material (12) in gel form is a resin selected from the group consisting of silicone resins, polyurethane resins, polyester resins, polystyrene resins and polyethylene resins, preferably polyurethane resins, silicone resins and mixtures thereof, more preferably silicone resins.

12. An electrical device (1) according to any of the preceding claims, wherein the composition (9) comprises a dielectric fluid selected from the group consisting of mineral oils, synthetic oils, in particular aromatic hydrocarbons, aliphatic hydrocarbons, silicone oils and synthetic esters, vegetable oils and natural esters and mixtures thereof, preferably aromatic hydrocarbons.

13. The electrical device (1) according to any of the preceding claims, wherein the composition (9) comprises a dielectric fluid selected from the group consisting of a mixture of benzyltoluene and one or more aromatic compounds other than benzyltoluene, in particular dibenzyltoluene or 1,1-diphenylethane.

14. An electrical device (1) according to any of the preceding claims, wherein the coil (7) comprises a plurality of layers connected to one another, which alternate continuously between electronically conductive layers, preferably aluminum or copper layers, and electronically insulating layers, preferably paper layers or polyolefin layers, in particular polypropylene layers.

15. Use of a material (12) in gel form in an electrical device (1) according to any one of claims 1 to 14 for preventing and possibly eliminating leakage of a composition (9) comprising at least one dielectric fluid.

16. A method for manufacturing an electrical device (1) according to any one of claims 1 to 14, comprising: - at least one step of inserting a coil as described above into the cavity of the housing, - optionally, at least one step of impregnating said coil with a composition comprising at least one dielectric fluid as described above, - at least one step of filling said cavity with a gellable composition, - at least one step of gelling the gelable composition to obtain a material in gel form as described above; The maximum volume occupied by the material in gel form is less than 50% of the total volume of the cavity.

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