Electrical apparatus comprising at least one gelled material

Abstract

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

Description

[0001] DESCRIPTION

[0002] TITLE: Electrical device comprising at least one gel material

[0003] The present invention relates to an electrical apparatus comprising at least one winding, at least one composition comprising at least one dielectric fluid, preferably a dielectric liquid, and at least one material in gel form, arranged inside the recess of a housing, and in which the ratio between the maximum volume occupied by the material in gel form and the total volume of the recess is less than 50%.

[0004] The invention also relates to the use of a material in gel form to prevent and / or minimize leaks of a composition comprising at least one dielectric fluid within an electrical device, in particular a capacitor or a transformer.

[0005] Electrical devices or equipment, for example electrical capacitors and transformers, comprise at least one winding and a dielectric fluid arranged in a housing which may be conductive or insulating. The winding, corresponding to the active parts of the electrical device, generally consists of an assembly, in particular of one or more windings or stacks, of several layers, connected together, successively alternating an electronically conductive layer and an electronically insulating layer. The winding may be impregnated with at least one dielectric fluid and arranged inside a housing or be immersed in a housing already filled with at least one dielectric fluid.For illustration, the winding may correspond to windings made of polypropylene sheets and metal sheets, in particular aluminum, impregnated with a dielectric fluid, for example an oil having a high dielectric constant, and be positioned inside a housing.

[0006] The housing, having for example a generally oblong shape, is commonly sealed at its ends using removable closing means intended to ensure the sealing and protection of electrical devices, in particular between the active parts of the electrical device and the surrounding environment.

[0007] However, such electrical devices most often have a lifespan of up to 30 or 50 years depending on their application. During their operation, external and / or internal stresses are likely to cause thermal expansion and / or mechanical deterioration of the housing closure means, thus altering the sealing and mechanical strength of the active parts of the electrical device and increasing the risks of leakage of the dielectric fluid into the surrounding environment.

[0008] In particular, when the housing is sealed with soldering means, these can oxidize over time, leading to the formation of rust spots which can degrade the sealing of electrical devices.

[0009] In other words, the degradation of these active parts and the risks of dielectric fluid leaks, particularly at the connectors between the active parts and the electrical network, are likely to increase over time, particularly as electrical devices age.

[0010] Dielectric fluid leaks pose a number of disadvantages as they are not only detrimental to the electrical performance of electrical devices, leading to high maintenance costs, but they can also be harmful to health and the environment.

[0011] Furthermore, dielectric fluid leaks pose additional safety concerns, including the dangers of flame propagation and acceleration in the event of a fire and rupture of the casing.

[0012] In order to overcome these drawbacks, solutions have been proposed, consisting of completely coating the active parts of electrical devices in a gellable composition or a polymerizable resin.

[0013] For this purpose, a process has already been implemented consisting of introducing the active parts of an electrical device into a housing and then pouring a gellable composition so as to completely fill the free spaces located between the active parts of the electrical device and the housing. Once the housing filling operation is complete, a gelling reaction takes place completely at room temperature.

[0014] Alternatively, a process has also been implemented consisting of completely coating the active parts of the electrical device in a polymerizable resin and then, once polymerization is complete, introducing the assembly into a housing.

[0015] However, the electrical performance of the equipment thus obtained is not entirely satisfactory. Indeed, air bubbles are likely to form in the active parts of electrical devices, which can have harmful effects on their operation, degrade their dielectric strength and lead to poor impregnation of the film constituting the active parts.

[0016] In view of the above, one of the objectives of the present invention is therefore to prevent, or even eliminate, the risks of leaks of the dielectric fluid in an electrical apparatus while maintaining satisfactory electrical performance. In other words, one of the aims of the present invention is to provide an electrical apparatus for which the risks of leaks of the dielectric fluid are minimized, or even eliminated, even after aging, while maintaining satisfactory electrical performance during its use.

[0017] In particular, the invention aims to propose an electrical device having good dielectric performance, in particular satisfactory dielectric strength, which is also capable of meeting a certain number of criteria, in particular health, ecological and / or safety criteria.

[0018] The present invention therefore relates in particular to an electrical device comprising: a housing provided with a recess, preferably longitudinal, a winding, at least one composition comprising at least one dielectric fluid, preferably a dielectric liquid, and at least one material in gel form arranged inside the recess, the material in gel form occupying a maximum volume less than 50% of the total volume of the recess.

[0019] The electrical device according to the invention thus has satisfactory electrical performance as well as reduced or even eliminated risks of leaks of the dielectric fluid, including after its aging, in particular under increasing direct voltages.

[0020] The electrical device according to the invention has in particular better electrical performance than electrical devices whose active parts, impregnated and / or immersed in a dielectric fluid, are completely coated in a polymerizable resin or a gellable composition.

[0021] Indeed, the risks of air bubbles forming in the active parts of the electrical device according to the invention during its operation are greatly reduced, or even eliminated, compared to electrical devices whose active parts are completely coated in a polymerizable resin or a gellable composition.

[0022] Furthermore, the mechanical strength and the sealing of the active parts of the electrical device according to the invention have the advantage of being suitably protected from the surrounding environment.

[0023] In particular, the gelled material effectively protects the most fragile areas of the electrical device while retaining a major part of the dielectric fluid inside the electrical device. In particular, the gelled material effectively protects the connections between the active parts of the electrical device and the electrical network as well as the soldered parts of the electrical device.

[0024] Thus, the gel-like material effectively controls thermal expansion within the electrical device.

[0025] The gel material also helps to reduce possible thermal expansion phenomena caused by the surrounding environment on the active parts of the electrical device, in particular the gel material also has the advantage of compensating for the thermal expansion and shrinkage of the dielectric fluid.

[0026] The electrical apparatus according to the invention thus has the advantage of being able to meet a certain number of criteria, for example health, ecological and / or safety, including after its aging under increasing continuous voltages, while ensuring satisfactory electrical performance, in particular by displaying high dielectric performance, for example good dielectric strength, as well as better resistance to partial discharges.

[0027] The invention also relates to the use of a material in gel form to prevent, and possibly eliminate, leaks of a composition comprising at least one dielectric fluid in an electrical device as defined above.

[0028] Another object of the present invention lies in a method of manufacturing an electrical device as described above.

[0029] Other objects, characteristics, aspects and advantages of the invention will appear even more clearly on reading the description and examples which follow.

[0030] In what follows, and unless otherwise indicated, the limits of a domain of values ​​are included in this domain, notably in the expressions "between" and "ranging from... to...".

[0031] Furthermore, the expressions “at least one” and “at least” used in this description are respectively equivalent to the expressions “one or more” and “greater than or equal”.

[0032] Electrical appliance

[0033] Electrical apparatus means any type of electrical equipment, whether transformers, electrostatic storage equipment, electricity transmission elements or electrical connectors, such as power transformers, distribution transformers, traction transformers, measuring transformers, special transformers, circuit breakers, capacitors, distributors, bushings, load tap changers, and others, to name only the main electrical devices or equipment comprising at least one dielectric fluid.

[0034] Preferably, the electrical apparatus is chosen from the group consisting of transformers, in particular measuring transformers, capacitors, bushings and load tap changers.

[0035] More preferably, the electrical device is chosen from the group consisting of measuring transformers and capacitors, in particular capacitors, in particular low voltage capacitors, medium voltage capacitors and high voltage capacitors.

[0036] According to the present invention, the winding, the composition comprising at least one dielectric fluid and the material in gel form are arranged inside the recess of the housing, and the material in gel form occupies a maximum volume of less than 50% relative to the total volume of the recess.

[0037] 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 recess of the housing.

[0038] In other words, the ratio between the maximum volume occupied by the material in gelled form and the total volume of the recess 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%.

[0039] Even more preferably, the material in gelled 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 recess.

[0040] The case can have any type of geometric shape, preferably a cylindrical or rectangular shape.

[0041] The housing can be conductive or insulating and can be made of any type of material. The housing can be made of ceramic, for example porcelain, metallic material, especially ferrous metals, especially steel or stainless steel, or non-ferrous metals.

[0042] According to the present invention, the recess can have all types of geometric shapes.

[0043] Thus, the recess is in particular a cavity capable of presenting all types of geometric shapes.

[0044] According to a general characteristic of the invention, the recess may have at least one longitudinal part.

[0045] According to a preferred feature of the invention, the recess may consist of said longitudinal part. In this case, the recess is longitudinal.

[0046] Alternatively, the recess may have other types of geometric shapes, for example a U-shape.

[0047] In this case, the recess has two longitudinal parts spaced from each other and connected to each other by a transverse part.

[0048] Advantageously, the recess is a longitudinal recess.

[0049] According to the present invention, one end of the recess corresponds to the distal portion of the recess which opens onto at least one front face of the housing, thereby forming an opening.

[0050] In other words, the recess comprises at least one end, in particular one or two ends, opening onto at least one front face of the housing, thus forming at least one opening, preferably one or two openings.

[0051] According to a preferred embodiment, the recess has at least one longitudinal part comprising at least one end opening onto at least one front face of the housing.

[0052] In other words, according to this embodiment, the recess has at least one longitudinal part provided with at least one end opening onto at least one front face of the housing.

[0053] Preferably, the recess is a longitudinal recess comprising at least one end opening onto at least one front face of the housing.

[0054] Preferably, the recess is a longitudinal recess comprising an end opening onto a front face of the housing.

[0055] Preferably, the recess is a longitudinal recess comprising two ends opening onto the two opposite front faces of the housing.

[0056] According to another embodiment, the recess has a U shape, i.e. has two longitudinal parts, spaced from each other and connected to each other by a transverse part, and comprises two ends opening onto the same front face of the housing, thus forming two openings appearing side by side on the same front face of the housing.

[0057] In particular, in this case, each longitudinal part comprises an end opening onto the same front face of the housing.

[0058] Advantageously, the material in gel form is at least located at at least one end of the recess, which makes it possible to protect the winding more effectively, in particular the mechanical strength and sealing of the active parts of the electrical device with respect to the surrounding environment, and to further reduce the risks of leakage of the dielectric fluid, or even eliminate them.

[0059] Preferably, the gelled material is at least located at at least one end of the recess, more preferably at at least two ends of the recess.

[0060] Preferably, the gelled material is at least located at at least one end of a longitudinal recess, more preferably at both ends of a longitudinal recess.

[0061] In other words, the material in gelled form is found in particular distributed within the electrical device according to the invention in at least one of the ends of the recess, preferably at one or both ends of a longitudinal recess.

[0062] In particular at least 10% by weight, or at least 50% by weight, or at least 90% by weight, or at least 92% by weight, or at least 94% by weight, or at least 96% by weight, or at least 98% by weight, of the total weight of the material in gel form is located at at least one of the ends of the recess, preferably at least at both ends of a longitudinal recess.

[0063] Preferably, the gelled material is at least located between at least one of the front faces of the housing and the dielectric fluid.

[0064] Preferably, the gelled material is not in contact with the winding.

[0065] The electrical device according to the invention thus has the advantage of limiting contact between the winding and the material in gel form.

[0066] In this way, the risks of air bubbles forming within the winding, which could hinder the proper functioning of the electrical device, are reduced or even eliminated.

[0067] Advantageously, the material in gel form, located at least at one of the ends of the longitudinal recess of the housing, preferably at both ends of the longitudinal recess of the housing, is not in contact with the winding. According to one embodiment, the material in gel form may be located at least partly between the composition comprising at least one dielectric fluid and the bore of the recess, i.e. between the composition comprising at least one dielectric fluid and the internal surface of the recess. In this case, the material in gel form adheres in particular to the bore of the recess.

[0068] In this way, the material in gel form can at least in places be sandwiched between the composition comprising at least one dielectric fluid and the bore of the recess.

[0069] The layer of material in gel form partly sandwiched between the bore of the recess 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 20,000 μm, in particular ranging from 1,000 to 10,000 μm.

[0070] According to this embodiment, the gelled material may be located at one end of the recess, preferably at one or both ends of a longitudinal recess, and may further be, partially or totally, sandwiched between the composition comprising at least one dielectric fluid and the bore of the recess.

[0071] Again, in accordance with this embodiment, the chemical nature of the gelled material may be different when positioned on one of the distal portions of the recess and when positioned between the bore of the recess and the dielectric fluid. Preferably, the chemical nature is the same when positioned on one of the distal portions of the recess and when positioned between the bore of the recess and the composition comprising at least one dielectric fluid.

[0072] Further, in accordance with this embodiment, at least 50% by weight, or at least 90% by weight, or at least 92% by weight, or at least 94% by weight, or at least 96% by weight, or at least 98% by weight, or at least 99% by weight, of the total weight of the gelled material may be located at at least one end of the recess, preferably at one or both ends of a longitudinal recess, and respectively, 50% or less by weight, or 10% or less by weight, or 8% or less by weight, or 6% or less by weight, or 4% or less by weight, or 2% or less by weight, or 1% or less by weight, of the total weight of the gelled material is located partially between the composition comprising at least one dielectric fluid and the bore of the recess.

[0073] According to a preferred embodiment, the composition comprising at least one dielectric fluid is at least partially in direct contact with the recess, preferably in direct contact with the bore of the recess. In other words, the composition comprising at least one dielectric fluid is at least in some places in direct contact with the recess, i.e. the dielectric fluid has one or more contact surfaces with the recess, in particular with the bore of the recess.

[0074] Thus, at these contact surfaces, the composition comprising at least one dielectric fluid is not separated from the recess by the material in gel form according to the invention.

[0075] According to an advantageous embodiment, the composition comprising at least one dielectric fluid is completely in direct contact with the bore of the recess.

[0076] The electrical device thus obtained has particularly improved electrical performance while preventing leaks of dielectric fluid, making it the most reliable from an ecological, health and safety point of view (particularly in the event of fire).

[0077] Preferably, the recess is longitudinal and the gelled material is located at one end of the recess, preferably at both ends of the recess.

[0078] More preferably, the material in gel form is located at one of the ends of the longitudinal recess, preferably at both ends of the longitudinal recess, and the composition comprising at least one dielectric fluid is totally in direct contact with the bore of the longitudinal recess, i.e. with the internal surfaces of the longitudinal recess of the housing.

[0079] In other words, the composition comprising at least one dielectric fluid is not separated from the recess by a space filled by the material in gel form according to the invention, over the entire internal surface of the recess.

[0080] Preferably, the gelled material is located at at least one end of the recess, preferably at one or both ends of a longitudinal recess, and may be in any suitable shape to prevent leakage of dielectric fluid, and may have a thickness ranging from 1 to 100 mm, preferably a thickness ranging from 5 to 50 mm.

[0081] Advantageously, the material in gel form is in the form of a plug which may have a thickness ranging from 1 to 100 mm, preferably a thickness ranging from 5 to 50 mm.

[0082] Alternatively, the recess has a U-shape. In this case, the recess has two longitudinal portions spaced apart from each other and connected to each other by a transverse portion, and comprises two ends opening onto the same front face of the housing, and the material in gel form is at least located at one of the ends of the recess, preferably at both ends of the recess.

[0083] Preferably, the gel-like material occupies a maximum volume of less than or equal to 30% and the composition comprising at least one dielectric fluid, preferably a dielectric liquid, occupies a volume of greater than or equal to 70% in the recess.

[0084] More preferably, the gel-form material occupies a maximum volume less than or equal to 20% and the composition comprising at least one dielectric fluid, preferably a dielectric liquid, occupies a volume greater than or equal to 80% in the recess.

[0085] In the context of the present invention, the winding, corresponding to the active parts of the electrical device, positioned inside the recess of the housing, can be impregnated with at least one dielectric fluid and / or be immersed, i.e. bathed, in at least one dielectric fluid.

[0086] According to a preferred characteristic of the present invention, the winding is immersed in at least one dielectric fluid.

[0087] According to another preferred characteristic, the winding is impregnated with at least one dielectric fluid by means of an impregnation process capable of being implemented before or after the introduction of the winding into the recess of the housing, i.e. therefore inside or outside the recess.

[0088] According to another preferred feature, the winding is first impregnated with at least one dielectric fluid, then is immersed in at least one dielectric fluid inside the recess of the housing. In other words, the winding can be impregnated with at least one dielectric fluid outside the housing using an impregnation process and then, once the impregnation is complete, the winding can then be immersed in at least one dielectric fluid filling the recess of the housing. In this case, the dielectric fluid used for impregnation and immersion can be the same or different, preferably is the same.

[0089] According to a general characteristic, the gel-form material is not miscible with the composition comprising the dielectric fluid.

[0090] For the purposes of the present invention, the gel-like material and the composition comprising the dielectric fluid are separate and are not miscible with each other.

[0091] For the purposes of the present invention, the term "immiscible" means that the material in gel form has a solubility of less than 0.1% by weight in the composition comprising the dielectric fluid in a temperature range from -60 to 150°C, preferably from -30 to 120°C.

[0092] The gel-form material 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.

[0093] The gel material can exhibit heat resistance in a temperature range of 50 to 200°C, particularly in a temperature range of 40 to 90°C.

[0094] Preferably, the gel-like material is a resin selected from the group consisting of silicone resins, polyurethane resins, polyester resins, polystyrene resins, polyethylene resins and mixtures thereof.

[0095] More preferably, the gel-form material is a resin selected from the group consisting of silicone resins, polyurethane resins, and mixtures thereof.

[0096] Even more preferably, the gel-form material is a resin selected from the group consisting of silicone resins.

[0097] For the purposes of the present invention, the term silicone means all organosilicon polymers or oligomers of variable molecular weight, obtained by polymerization and / or polycondensation of silanes, comprising at least one repetition of units in which the silicon atoms are linked together by oxygen atoms (siloxane bond -Si-O-Si-).

[0098] Siloxanes can be prepolymers of silicone, polysilane, polysilazane, polycarbosilane, polysilphenylene.

[0099] Preferably, the gel material is a silicone resin having a cone penetrability ranging from 2 to 500 mm / 10, in particular ranging from 5 to 350 mm / 10, measured at a temperature of 25°C according to ISO2137.

[0100] Preferably, the gel-form material is a silicone resin, in particular made from a two-component mixture comprising a component A and a component B.

[0101] More preferably, the material in gel form is a silicone resin made from a mixture of two components, in a 1 / 1 weight ratio, sold under the trade name / BLUESIL ESA 6018-01A + BLUESIL ESA 6018-01B, having in particular a viscosity of 530 mPa.s at a temperature of 23°C, measured according to standard ISO 3219.

[0102] According to a general characteristic of the invention, the material in gel form and the composition comprising at least one dielectric fluid are notably distinct, in particular the composition comprising at least one dielectric fluid is not in the form of a dispersed phase in the material in gel form.

[0103] For the purposes of the present invention, dielectric fluid means a fluid which does not conduct electricity (or only slightly) but allows electrostatic forces to be exerted.

[0104] According to a general characteristic of the invention, the dielectric fluid may be a dielectric gas, a dielectric liquid or a mixture of dielectric gas and dielectric liquid.

[0105] Preferably, the dielectric fluid is a dielectric liquid.

[0106] The dielectric liquid can have a kinematic viscosity, measured at a temperature of 40°C, ranging from 1 to 51 mm 2 .s -1 , preferably ranging from 1 to 35 mm 2 .s' 1 measured according to ISO 3104.

[0107] The dielectric fluid may be 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, as well as their mixtures.

[0108] Synthetic oils are preferably selected from the group consisting of aromatic hydrocarbons, aliphatic hydrocarbons, silicone oils, synthetic esters, and mixtures thereof.

[0109] Aromatic hydrocarbons include alkylbenzenes, alkyldiphenylethanes (e.g. phenylxylylethane (PXE), phenylethylphenylethane (PEPE)), monoisopropylbiphenyl (MIPB), 1,1-diphenylethane (1,1-DPBE), alkylnaphthalenes (e.g. diisopropylnaphthalene (DIPN), methylpolyarylmethanes (e.g. benzyltoluene (BT) and dibenzyltoluene (DBT), and mixtures thereof.

[0110] In said aromatic hydrocarbons, it is to be understood that at least one ring is aromatic and that, optionally, one or more other ring(s) present may be partially or totally unsaturated.

[0111] Among the aliphatic hydrocarbons, we can notably cite poly(alpha)olefins (PAO), for example polyisobutene (PIB) or vinylidene olefins, such as those marketed for example by the company Soltex Inc.

[0112] Among the silicone oils, we can notably cite linear silicone oils of the polydimethylsiloxane type such as, for example, those marketed by the Wacker company under the trade name Wacker® AK.

[0113] Among the synthetic esters, mention may be made in particular of phthalic type esters, in particular alkyl phthalates such as dioctylphthalate (DOP) or di-isononylphthalate (DINP) (marketed for example by the company BASF). Mention may also be made of esters resulting from the reaction between a polyalcohol and an organic acid, in particular an acid chosen from C4 to C22 organic acids, saturated or unsaturated. 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 which may be used for the synthesis of the aforementioned esters, mention may be made, as non-limiting examples, of pentaerythritol.

[0114] Thus, synthetic esters resulting from the reaction between a polyalcohol and an organic acid are, for example, products from the Midel® range, such as Midel® 7131, or from the Mivolt® range, such as Mivolt® DFK and Mivolt® DF7 from the company M&I Materials, or even esters from the Nycodiel range from the company Nyco.

[0115] Natural esters and vegetable oils include products derived from oily seeds or other sources of natural origin. Examples include, but are not limited to, FR3™ and Envirotemp™ marketed by Cargill, or Midel eN 1215 marketed by M&I Materials.

[0116] Vegetable oils also include rapeseed oil, corn oils, castor oil, and soybean oils and their mixtures.

[0117] Mineral oils include paraffinic oils, naphthalene oils such as the Nytro family of dielectric oils marketed by Nynas (in particular Nytro Taurus, Nytro Libra, Nytro 4000X and Nytro 10XN), and Dalia, marketed by Shell.

[0118] Preferably, the dielectric fluid is free of phthalic type esters, in particular alkyl phthalates such as dibutyl phthalate, dioctyl phthalate.

[0119] Preferably, the dielectric fluid is a synthetic oil, in particular chosen from the group consisting of aromatic hydrocarbons.

[0120] Advantageously, the dielectric fluid is chosen from the group consisting of methylpolyarylmethanes.

[0121] Advantageously, the dielectric fluid is chosen from the group consisting of mixtures based on benzyltoluene and one or more aromatic compounds, other than benzyltoluene, as described previously, in particular dibenzyltoluene or 1,1-diphenylethane.

[0122] Still advantageously, the dielectric fluid is a mixture comprising benzyltoluene and one or more aromatic compounds, different from benzyltoluene, as described previously, in particular dibenzyltoluene or 1,1-diphenylethane; the benzyltoluene being present in a concentration greater than or equal to 30% by weight, preferably present in a concentration greater than or equal to 40% by weight, more preferably in a concentration greater than or equal to 50% by weight, even more preferably in a concentration greater than or equal to 60% relative to the total weight of said mixture.

[0123] More preferably, the mixtures of benzyltoluenes and dibenzyltoluenes comprise 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.

[0124] Even more preferably, the mixtures of benzyltoluenes and dibenzyltoluenes comprise 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.

[0125] The composition may also comprise one or more additives and / or fillers, well known to those skilled in the art, for example chosen, in a non-limiting manner, from the group consisting of antioxidants, passivators, pour point depressants, decomposition inhibitors, perfumes and aromas, colorants, preservatives, and others as well as their mixtures.

[0126] Among the antioxidants that may be advantageously used, mention may in particular be made, as non-limiting examples, of phenolic antioxidants, such as, for example, dibutylhydroxytoluene, butylhydroxyanisole, tocopherols, as well as the acetates of these phenolic antioxidants; but also amine-type antioxidants, such as, for example, phenyl-a-naphthylamine, of diamine type, for example, N,N'-di-(2-naphthyl)-paraphenylenediamine, but also ascorbic acid and its salts, esters of ascorbic acid, alone or in mixtures of two or more of them or with other components, such as, for example, green tea extracts, coffee extracts.

[0127] A particularly suitable antioxidant is the one commercially available from Brenntag under the trade name Ionol®.

[0128] The passivators which can be used as additives in the composition usable in the context of the present invention are of any type known to those skilled in the art and are advantageously chosen from triazole derivatives, benzimidazoles, imidazoles, thiazole, benzothiazole. By way of example and in a non-limiting manner, dioctylaminomethyl-2,3-benzotriazole and 2-dodecyldithioimidazole can be mentioned. Among the pour point depressants which can be present in the composition usable in the context of the present invention, mention may be made, by way of non-limiting examples, of sucrose fatty acid esters, acrylic polymers such as poly(alkyl methacrylate) or poly(alkyl acrylate).

[0129] Preferred acrylic polymers are those with molecular weights between 50,000 g mol 1 and 500000 g mol -1. Examples of such acrylic polymers include polymers which may contain linear alkyl groups comprising from 1 to 20 carbon atoms.

[0130] Among these, and always by way of non-limiting examples, mention may be made of poly(methyl acrylate), poly(methyl methacrylate), poly(heptyl acrylate), poly(heptyl methacrylate), poly(nonyl acrylate), poly(nonyl methacrylate), poly(undecyl acrylate), poly(undecyl methacrylate), poly(tridecyl acrylate), poly(tridecyl methacrylate), poly(pentadecyl acrylate), poly(pentadecyl methacrylate), poly(heptadecyl acrylate), and poly(heptadecyl methacrylate).

[0131] An example of such a pour point depressant is commercially available from Sanyo Chemical Industries, Ltd., under the trade name Aclube.

[0132] According to a very particularly preferred aspect, the composition according to the present invention comprises at least one decomposition inhibitor, as an additive.

[0133] The decomposition inhibitor may be of any type well known to those skilled in the art and in particular may be chosen from carbodiimide derivatives such as diphenyl carbodiimide, di-tolylcarbodiimide, bis(isopropylphenyl)carbodiimide, bis(butylphenyl)carbodiimide, but also from phenylglycidyl ethers, or esters, alkylglycidyl ethers, or esters, 3,4-epoxycyclohexylmethyl-(3,4-epoxycyclohexane)carboxylate, compounds of the anthraquinone family, such as for example 0-methylanthraquinone marketed under the name “BMAQ”, epoxidized derivatives such as vinylcyclohexene diepoxides, 3,4-epoxy-6-methylcyclohexylmethyl-(3,4-epoxy-6-methylhexane)carboxylate, phenol-type epoxy resins novolak, bisphenol A diglycidyl ether epoxy, such as DGEBA or CEL 2021P, available in particular from Whyte Chemicals.

[0134] The weight content of the additive, or additives optionally present in the composition according to the present invention may range from 0.0001% to 5% by weight, preferably from 0.001% to 3% by weight, more preferably from 0.01% to 2% by weight, limits included, relative to the total weight of the composition. Preferably, the composition according to the invention comprises a mixture of benzyltoluene and one or more aromatic compounds, other than benzyltoluene, as defined above, in particular dibenzyltoluene or 1,1-diphenylethane, in particular sold under the trade names Jarylec® C101 and Jarylec® C101D by the company Arkema, or SAS 60® by the company JX Nippon Chemical Texas Inc.

[0135] Advantageously, the material in gel form is a resin selected from the group consisting of silicone resins and the composition comprises a mixture of benzyltoluene and one or more aromatic compounds, different from benzyltoluene, as defined above, in particular dibenzyltoluene or 1,1-diphenylethane, the benzyltoluene being present in a mass concentration greater than or equal to 30% by weight, preferably present in a mass concentration greater than or equal to 40% by weight, more preferably in a mass concentration greater than or equal to 50% by weight, even more preferably in a mass concentration greater than or equal to 60% relative to the total weight of said mixture.

[0136] In accordance with the present invention, the term "winding" means any assembly, in particular any winding or stacking, of several layers, connected to each other, successively alternating an electronically conductive layer and an electronically insulating layer.

[0137] The electronically conductive layer is in particular a metal layer, for example of aluminum or copper, or a doubly metallized foil. Preferably, the electronically conductive layer is an aluminum foil.

[0138] The electronically insulating layer may be selected from the group consisting of paper, a polyolefin, in particular polypropylene, a polyester, or mixtures thereof.

[0139] Preferably, the electronically insulating layer is a layer of polyolefin, in particular polypropylene.

[0140] Preferably, the winding is an assembly, in particular a winding, of an aluminum layer and a polyolefin layer, in particular polypropylene.

[0141] Advantageously, the winding is an assembly successively alternating a plurality of layers of aluminum and layers of polyolefin, in particular polypropylene, impregnated with at least one dielectric fluid, in particular selected from the group consisting of mixtures of benzyltoluenes and one or more aromatic compounds, other than benzyltoluene, as defined above, in particular dibenzyltoluene or 1,1-diphenylethane, more precisely those described above.

[0142] The winding can be wrapped in paper or kraft-type cardboard.

[0143] According to an advantageous embodiment, the invention relates to an electrical capacitor or a transformer, in particular a measuring transformer, comprising: a housing provided with a recess, preferably longitudinal, a winding, at least one composition comprising at least one dielectric fluid, preferably a dielectric liquid, and at least one material in gel form arranged inside the recess, the material in gel form occupying a maximum volume 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 recess.

[0144] According to this embodiment, the dielectric fluid is advantageously a mixture of benzyltoluene and one or more aromatic compounds, different from benzyltoluene, as defined previously, in particular dibenzyltoluene or 1,1-diphenylethane and the material in gel form being a silicone resin.

[0145] According to one embodiment, the invention relates to an electrical apparatus, comprising: a housing provided with a recess, preferably longitudinal, at least one winding and at least one composition comprising at least one dielectric fluid arranged inside the recess, at least one plug formed of a material in gel form; the electrical apparatus further comprising material in gel form interposed between the composition comprising at least one dielectric fluid and the bore of the recess and spaced from said plug.

[0146] According to this advantageous embodiment, the gel-form material that is interposed between the composition comprising the dielectric fluid and the bore of the recess may be the same or different, preferably the same, as the gel-form material forming the plug. According to this embodiment, the electrical apparatus, the composition comprising the dielectric fluid, the winding and the recess are as previously described.

[0147] According to this embodiment, the material in gel form occupies a maximum volume less than 50% relative to the total volume of the recess.

[0148] According to this embodiment, the electrical apparatus is preferably a capacitor or a transformer, in particular a measuring transformer.

[0149] According to an advantageous embodiment, the electrical device comprises: a housing provided with a recess, preferably longitudinal as described above, a winding and at least one composition comprising at least one dielectric fluid arranged inside the recess as described above; the composition comprising at least the dielectric fluid being at least partly in direct contact with the recess, a material in gelled form, as described above, arranged inside the recess and at least located at one of the ends of the recess.

[0150] According to this advantageous embodiment, the composition comprising the dielectric fluid shares at least one contact surface with the recess, in particular with at least the bore of the recess.

[0151] Preferably, according to this advantageous embodiment, the composition comprising the dielectric fluid is entirely in direct contact with the bore of the recess, i.e. with one of the internal surfaces of the recess.

[0152] According to this embodiment, the electrical apparatus, the composition comprising the dielectric fluid, the winding and the recess are as described previously.

[0153] Preferably, in accordance with this embodiment, the material in gel form occupies a maximum volume of less than 50% relative to the total volume of the recess.

[0154] Use

[0155] The present invention also relates to the use of a material in gel form to prevent, and possibly eliminate, leaks of a composition comprising at least one dielectric fluid, as defined above, in an electrical device as defined above.

[0156] In particular, the electrical device is a transformer, especially a measuring transformer, or a capacitor.

[0157] In other words, the invention relates to the use of a material in gel form inside an electrical device, as defined above, to prevent, and possibly eliminate, leaks of a composition comprising at least one dielectric fluid.

[0158] In other words, the invention relates in particular to the use of a material in gel form to prevent, and possibly eliminate, leaks of a composition comprising at least one dielectric fluid, in an electrical device comprising: a housing provided with a recess, preferably longitudinal, a winding and at least one composition comprising at least one dielectric fluid, preferably a dielectric liquid, arranged inside the recess, said material in gel form being arranged inside the recess and occupying a maximum volume less than 50% of the total volume of the recess.

[0159] Process

[0160] The present invention also relates to a method of manufacturing an electrical device as described above.

[0161] Preferably, the method comprises:

[0162] - at least one step of inserting a winding, as described previously, into the recess of the housing,

[0163] - optionally, at least one step of impregnating the winding with a composition comprising at least one dielectric fluid, as described previously,

[0164] - at least one step of filling the recess with a gellable composition,

[0165] - at least one step of gelling said gellable composition to obtain a material in gelled form as described above; such that the material in gelled form occupies a maximum volume less than 50% of the total volume of the recess. More preferably, the method comprises:

[0166] - at least one step of inserting a winding, as described previously, into the recess of the housing,

[0167] - at least one step of impregnating the winding with a composition comprising at least one dielectric fluid, as described previously,

[0168] - at least one step of filling the recess with a gellable composition,

[0169] - at least one step of gelling said gellable composition to obtain a material in gelled form as described above; such that the material in gelled form occupies a maximum volume less than 50% of the total volume of the recess.

[0170] The step of impregnating the winding can be carried out before or after the step of inserting said winding into the recess of the housing, preferably after the insertion step.

[0171] The gelation step can take place at a temperature ranging from 5°C to 70°C, preferably from 23°C to 70°C.

[0172] The step of filling the recess with a gellable composition may take place before the step of inserting the winding into the recess, or after the gelling of said composition.

[0173] The filling step may comprise one or more, preferably one or two, steps of filling the recess with a gellable composition.

[0174] The filling step may comprise depositing the gellable composition on at least one end of the recess and / or partially or totally on the bore of the recess.

[0175] Preferably, the method comprises: i) at least one step of partially filling a recess of the housing with a gellable composition, ii) at least one step of gelling said gellable composition to obtain a material in gelled form as described above, iii) at least one step of inserting a winding, as described above, into the recess of the housing, iv) at least one step of impregnating the winding with a composition comprising at least one dielectric fluid, as described above, v) at least one step of filling the remainder of the recess of the housing with said gellable composition, vi) at least one step of gelling the gellable composition added to step v) to obtain a material in gelled form as described above; such that the material in gelled form occupies a maximum volume less than 50% of the total volume of the recess.

[0176] The partial filling step i) may comprise depositing the gellable composition on at least one end of the recess and / or partially or totally on the bore of the recess.

[0177] The gelling step ii) may take place at a temperature ranging from 5°C to 70°C, preferably from 23°C to 70°C.

[0178] The impregnation step iv) can be carried out before or after step iii) of inserting the winding into the recess of the housing, preferably after step iii).

[0179] The impregnation step may for example include:

[0180] - a step of impregnating the winding under reduced pressure at a temperature ranging from 5°C to 100°C, preferably from 23°C to 100°C, with the composition comprising the dielectric fluid, for a period ranging from 48 to 200 hours, preferably from 48 to 150 hours,

[0181] - possibly followed by a step of cooling the winding to room temperature, for example to a temperature of 23°C.

[0182] Filling step v) may comprise depositing said gellable composition over the entire bore and / or at least one end of the recess, different from the end of step i).

[0183] Other characteristics and advantages of the invention will appear even more clearly on detailed examination of an embodiment taken as a non-limiting example of an electrical apparatus according to the invention and illustrated by the appended drawing, in which Figure 1 represents a sectional view of the capacitor according to the invention.

[0184] As illustrated in the single figure, the electrical apparatus extends along a general longitudinal axis X-X'. In Figure 1, the electrical apparatus 1 is shown in a position assumed to be horizontal.

[0185] Alternatively, the electrical appliance 1 can also be in a vertical position.

[0186] The electrical apparatus 1 comprises a housing 3, shown here schematically. The housing 3 may be electrically insulating, for example made of a ceramic material, for example porcelain, or electrically conductive, for example made of a metallic material, in particular with ferrous metals.

[0187] The housing 3 is shown in Figure 1 with a rectangular shape but can have any type of geometric shapes.

[0188] The housing 3 is provided with a longitudinal recess 5. In the illustrated embodiment, the recess 5 is axially transverse. The recess 5 has two ends 5a and 5b which open respectively onto the front faces 3a, 3b of the housing 3, thus forming two openings.

[0189] Alternatively, the recess 5 could not be through. In this case, the recess 5 has a single end which opens onto only one of the two front faces 3a, 3b of the housing 3.

[0190] Alternatively, the recess 5 has a U-shape. In this case, the recess 5 has two longitudinal parts spaced from each other and connected to each other by a transverse part, and comprises two ends 5a and 5b opening onto the same front face 3a and 3b of the housing 3.

[0191] The electrical device 1 also comprises a winding 7 arranged inside the recess 5 and which is immersed in a composition 9 comprising a dielectric fluid.

[0192] Alternatively, the winding 7 may be impregnated with the composition 9 over part or all of its surface by means of an impregnation process capable of being implemented before or after the introduction of the winding 7 into the recess 5 of the housing 3, i.e. therefore inside or outside the recess 5.

[0193] As a further variant, the winding 7 may first be impregnated with the composition 9 over all or part of its surface, outside the recess 5, by an impregnation process, then the winding 7 may be inserted into the recess 5 previously filled with the composition 9.

[0194] The impregnation method may for example comprise: a step of impregnating the winding 7 under reduced pressure at a temperature which may range from 5°C to 100°C, preferably from 23°C to 100°C, with the composition 9, for a period which may range from 48 to 200 hours, preferably from 48 to 150 hours, the winding 7 may then be cooled to a temperature of 23°C,

[0195] As indicated above, the winding 7 is preferably a winding successively alternating layers of aluminum and layers of polyolefin, for example constituted in an alternating succession of aluminum sheets and polyolefin sheets, in particular polypropylene. As indicated 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, other than benzyltoluene, as defined above, in particular dibenzyltoluene or 1,1-diphenylethane.

[0196] Advantageously, composition 9 can be sold under the trade names Jarylec® C101 and Jarylec® C101D by the company Arkema or the trade name SAS 60® by the company JX Nippon Chemical Texas Inc.

[0197] As illustrated in Figure 1, the composition 9 is arranged so as to be entirely in direct contact with the bore of the recess 5.

[0198] In other words, the composition 9 is not separated from the bore of the recess 5 by an empty space or a free space.

[0199] The electrical appliance 1 further comprises a material 12 in gel form which is immiscible with the composition 9. The material 12 is distinct from the composition 9. The material 12 is preferably selected from the group consisting of silicone resins, polyurethane resins, polyester resins, polystyrene resins and polyethylene resins and mixtures thereof.

[0200] Advantageously, the material 12 in gelled form is a resin selected from the group consisting of silicone resins, polyurethane resins and their mixtures.

[0201] More preferably, the material 12 in gelled form is selected from the group consisting of silicone resins.

[0202] The material 12 in gel form is disposed inside the recess 5 of the housing. The material 12 in gel form comes into contact against the bore of the recess 5.

[0203] As shown in the single figure, the material 12 in gelled form occupies a maximum volume less than or equal to 20% relative to the total volume of the recess 5. In other words, the ratio between the maximum volume occupied by the material 12 in gelled form and the total volume of the recess is less than or equal to 20%.

[0204] According to the present invention, the material 12 in gelled form can also occupy a larger volume in the recess 5, in particular a maximum volume less than 50% relative to the total volume of the recess 5.

[0205] As shown in the single figure, the material 12 in gelled form is located at each end 5a and 5b of the recess 5. In particular, the material 12 is located between the two front faces 3a and 3b of the housing 3 and the composition 9. The material 12 in gelled form is thus presented in this example in the form of two blocks or plugs 12a, 12b. The material 12 in gelled form thus closes the recess 5.

[0206] The internal face of each plug 12a, 12b formed by the material 12 in gelled form is in contact with the composition 9.

[0207] In particular, the material 12 is not in contact with the winding 7, i.e. with the active parts of the electrical device 1.

[0208] The positioning of the material 12 thus makes it possible to effectively prevent leaks of the composition 9 comprising the dielectric fluid and ensures the protection of the winding 7 with respect to the external environment, in particular the mechanical strength and the sealing of the winding 7 are effectively preserved, including during aging of the electrical device 1.

[0209] In Figure 1, the material 12 is positioned at the two ends 5a and 5b of the longitudinal recess 5 but can alternatively be located only at one of the ends of the recess 5, in particular when the recess 5 has a single end which opens onto a single front face 5a or 5b, thus forming an opening.

[0210] The positioning of the material 12 makes it possible to prevent the risks of the material 12 coming into contact with the winding 7, minimizing the formation of air bubbles.

[0211] The electrical device 1 further comprises closing means 15 each fixed to one end of the housing. The closing means 15 are distinct from the material 12. The closing means 15 are removably fixed to the housing by any suitable means, here by threading.

[0212] The electrical device 1 according to the invention thus has improved electrical performance, in particular good dielectric strength and better resistance to partial discharges.

[0213] Furthermore, the risks of leaks of the dielectric fluid in the electrical device 1 are reduced, or even eliminated, even after its aging, in particular under increasing continuous voltages.

[0214] The following examples serve to illustrate the invention without, however, being of a limiting nature.

[0215] EXAMPLE

[0216] 1. Verification of the gel seal A clear glass test tube was filled with 5 mL of Jarylec® C101 and then with 1 mL of BLUESIL ESA 6018-01A + 1 mL BLUESIL ESA 6018-01B, two products marketed by ELKEM, to form a silicone gel. The test tube was then placed in an oven at 40°C for 3 hours. At the end of this step, the tube can be turned upside down without any liquid flowing out.

[0217] 2. Determination of the dielectric properties of a film capacitor according to one embodiment of the invention.

[0218] Description of the production of film capacitors

[0219] The windings are made with a rough polypropylene film of type PP2MAR8.3 marketed by the company BOLLORE Film Plastiques.

[0220] The box used is a cylindrical box with a volume of 250 cm 3 capable of being closed at both ends.

[0221] Two capacitors are made.

[0222] In a first case (case No. 1 - invention), the case is kept in a vertical position and then filled with 8g of BLUESIL ESA 6018-01A and 8g of BLUESIL ESA 6018-01B in order to form a gelled layer in the lower part of the case, i.e. at the bottom of the case. Gelling takes place for a period of 20 hours at room temperature, i.e. a temperature of 23°C.

[0223] The winding is then placed in the box containing the gel layer at the bottom of the box and then an impregnation step is carried out with 200g of Jarylec® C101 for 5 days at 90°C. At the end of this step and after cooling to room temperature, the gel components are added at a rate of 8g of BLUESIL ESA 6018-01A and 8g of BLUESIL ESA 6018-01B to allow the formation of a waterproof gel on the surface. The box is then closed. Gelling takes place for 20 hours at room temperature.

[0224] The measurement of the dissipation factor (delta tangent) can then be carried out.

[0225] In a second case (case no. 2 - comparison), the winding is impregnated with Jarylec® C101 for 5 days at 90°C, at the end of which stage the excess Jarylec® fluid is removed before placing the winding in the case. The case is then completely filled with 116g of BLUESIL ESA 6018-01A and 116g of BLUESIL ESA 6018-01B. Gelling takes place for 20 hours at room temperature. The dissipation factor (delta tangent) can then be measured.

[0226] The results of the tangent delta measurements were then carried out at 20°C and the results are shown in the following table. The values ​​obtained with box No. 1 (values ​​less than 0.001 after 60 minutes) are excellent and significantly better than those obtained for box No. 2.

[0227] [Table 1]

Claims

CLAIMS 1. Electrical apparatus comprising: a housing (3) provided with a recess (5), a winding (7) and at least one composition (9) comprising at least one dielectric fluid arranged inside the recess (5); a material in gel form (12), arranged inside the recess (5), occupying a maximum volume less than 50% of the total volume of the recess (5).

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

3. Electrical appliance (1) according to claim 1, in which the material (12) in gelled form occupies a maximum volume less than or equal to 40%, preferably less than or equal to 30%, more preferably less than or equal to 20%, more particularly less than or equal to 15%, of the total volume of the recess (5).

4. Electrical apparatus (1) according to any one of the preceding claims, wherein the gel-like material (12) is at least located at at least one end of the recess (5), preferably at least two ends of the recess (5).

5. Electrical apparatus (1) according to any one of the preceding claims, wherein the gelled material (12) is not in contact with the winding (7).

6. Electrical apparatus (1) according to any one of the preceding claims, wherein the gelled material (12) is located at least partly between the composition (9) comprising at least one dielectric fluid and the bore of the recess (5).

7. Electrical apparatus (1) according to any one of the preceding claims, wherein the composition (9) comprising the dielectric fluid is at least partly in direct contact with the recess (5), preferably totally in direct contact with the bore of the recess (5).

8. Electrical appliance (1) according to any one of the preceding claims, in which the recess (5) comprises a longitudinal part comprising at least one end (5a, 5b) opening onto at least one of the faces fronts (3a, 3b) of the housing (3) and the gelled material (12) is at least located at at least one end (5a, 5b) of the recess (5), preferably at least at both ends (5a, 5b) of the recess (5).

9. Electrical apparatus (1) according to any one of the preceding claims, wherein the gelled material (12) is located between one of the front faces (3a, 3b) of the housing (3) and the composition comprising the dielectric fluid (9).

10. Electrical apparatus (1) according to any one of the preceding claims, wherein the gelled material (12) is not miscible with the composition (9) comprising the dielectric fluid.

11. Electrical apparatus (1) according to any one of the preceding claims, wherein the gelled material (12) 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. Electrical apparatus (1) according to any one 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, as well as mixtures thereof, preferably aromatic hydrocarbons.

13. Electrical apparatus (1) according to any one of the preceding claims, in which the composition (9) comprises a dielectric fluid chosen from the group consisting of mixtures of benzyltoluene and one or more aromatic compounds, other than benzyltoluene, in particular dibenzyltoluene or 1,1-diphenylethane.

14. Electrical apparatus (1) according to any one of the preceding claims, wherein the winding (7) comprises a plurality of layers, connected together, successively alternating an electronically conductive layer, preferably a layer of aluminum or copper, and an electronically insulating layer, preferably a layer of paper or a layer of polyolefin, in particular a layer of polypropylene.

15. Use of a material (12) in gelled form inside an electrical device (1) according to any one of claims 1 to 14 to prevent, and optionally suppressing leaks of a composition (9) comprising at least one dielectric fluid.

16. Method of manufacturing an electrical device (1) as described according to any one of claims 1 to 14, comprising: - at least one step of inserting a winding, as described previously, into the recess of the housing, - optionally, at least one step of impregnating the winding with a composition comprising at least one dielectric fluid, as described previously, - at least one step of filling the recess with a gellable composition, - at least one step of gelling said gellable composition to obtain a material in gelled form as described above; such that the material in gelled form occupies a maximum volume less than 50% of the total volume of the recess.

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