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    • 专利摘要:
    The present invention relates to a medium or high voltage electrical apparatus comprising a sealed enclosure in which there are electrical components and a gas mixture ensuring electrical insulation and / or extinguishing of electric arcs likely to occur in this enclosure, the mixture gas comprising heptafluoroisobutyronitrile and tetrafluoromethane. In the sealed chamber of the electrical apparatus according to the invention, there may be electrical components covered with a solid dielectric layer of variable thickness.
    公开号:FR3032828A1
    申请号:FR1551216
    申请日:2015-02-13
    公开日:2016-08-19
    发明作者:Yannick Kieffel；Jean-Marc Willieme
    申请人:Alstom Technolgoy AG；
    IPC主号:
    专利说明:

    [0001] TECHNICAL FIELD The invention belongs to the field of electrical insulation and extinguishing of electric arcs in medium or high voltage electrical equipment. BACKGROUND OF THE INVENTION The invention relates to the field of electrical insulation and extinguishing of electric arcs in medium or high voltage electrical apparatus. BACKGROUND OF THE INVENTION
    [0002] More particularly, the present invention relates to the use of a gaseous mixture comprising heptafluoroisobutyronitrile and tetrafluoromethane, as electrical insulation gas and / or electric arc extinguishing in a medium or high voltage electrical apparatus. More particularly, the present invention relates to the use, in a medium or high voltage electrical appliance, of a low environmental impact insulation based on a gaseous medium comprising heptafluoroisobutyronitrile and tetrafluoromethane as electrical insulation gas and / or extinction of electric arcs. This insulation based on such a gas mixture may optionally be combined with a solid insulation of low dielectric permittivity applied in low or thick layer on the conductive parts subjected to an electric field greater than the breakdown field of the system without solid insulation. The thickness of the insulating layer being a function of the utilization factor of the electric field, ri, defined as the ratio of the average electrical field (U / d) on the maximum electric field, Emax (ri = U / (Emax * d)), the layer being thick for use factors close to 0.3 and the layer being fine for use factors approaching 0.9.
    [0003] It also relates to a medium or high voltage electrical apparatus in which the extinction of electric arcs is ensured by a gaseous medium comprising heptafluoroisobutyronitrile and tetrafluoromethane while the electrical insulation is provided by the same gas, if any. in combination with a solid insulation of low dielectric permittivity applied in a low or thick layer on the conductive parts subjected to an electric field greater than the breakdown field of the system without solid insulation. This electrical apparatus can in particular be an electrical transformer such as a power or measurement transformer, a gas-insulated line (or LIG) for the transport or distribution of electricity, a busbar or an electrical appliance. connection / disconnection device (also called a switchgear) such as a circuit breaker, a switch, a fuse-switch combination, a disconnector, an earthing switch (MALT) or a contactor.
    [0004] STATE OF THE PRIOR ART In medium and high voltage substation electrical apparatus, electrical insulation and, where appropriate, arcing extinguishing are typically provided by a gas which is confined to the earth. inside these devices. Currently, the gas most often used in this type of device is sulfur hexafluoride (SF6).
    [0005] This gas has, in fact, a relatively high dielectric strength, good thermal conductivity and low dielectric losses. It is chemically inert and non-toxic to humans and animals and, after being dissociated by an electric arc, it recombines rapidly and almost completely. In addition, it is nonflammable and its price is still moderate today. However, SF6 has the major disadvantage of having a Global Warming Potential (GWP) of 23,500 (relative to CO2 over 100 years) according to the latest IPCC 2013 report (for "Intergovernmental Panel on Climate Change ") and an atmospheric residence time of 3,200 years, placing it among the gases with a high greenhouse effect. SF6 was therefore included in the Kyoto Protocol (1997) on the list of gases whose emissions must be limited. The best way to limit SF6 emissions is to limit the use of this gas, which has led industry to look for alternatives to SF6. So-called "simple" gases such as air or nitrogen, which do not have a negative impact on the environment, have a much lower dielectric strength than SF6. As a result, the use of these simple gases for electrical isolation and / or arc extinguishing in substation electrical apparatus involves drastically increasing the volume and / or pressure. filling these devices, which goes against the efforts that have been made in recent decades to develop compact electrical appliances, safe for staff and increasingly small footprint. Mixtures of SF6 and nitrogen are used to limit the impact of SF6 on the environment. In fact, the addition of SF6 in amounts of 10 to 20% by volume makes it possible to significantly improve the dielectric strength of nitrogen. Nevertheless, because of the high PRG of SF6, the GWP of these mixtures remains very high. Such mixtures can not therefore be used as a low environmental impact gas. The same is true for the mixtures described in the European patent application published under No. 0 131 922, [1], and comprising about 60 to 99.5 mol% of SF6 and about 0.5 to 40 mol% saturated fluorocarbon and especially selected from C2F8CN, CBrC1F2 and c-C4F8. Perfluorocarbons (CnF2n + 2 and c-C4F8) generally exhibit interesting dielectric withstand properties, but their PRGs typically range from 5,000 to 10,000 (6,500 for CF4, 7). 000 for C3F8 and C4-Fm, 8,700 for c-C4F8, 9,200 for C2F6). Note that the CF4 has already been used in a mixture with SF6 for applications at very low temperatures. Indeed, the CF4 has near-SF6 cutoff performance, is less sensitive to low temperatures, but its dielectric strength is worse than that of SF6. When using these SF6-CF4 blends, the overall performance of the blend was therefore limited due to the reduced dielectric performance due to CF4. US Patent 4,547,316, [2], is intended to provide an insulating gas mixture for electrical devices and having important insulating properties and with moderate toxicity for humans and animals, compared to C2F6CN. Thus, the proposed gas mixture comprises C2F6CN and an alkyl nitrite more particularly selected from the group consisting of methyl nitrite, ethyl nitrite, propyl nitrite, butyl nitrite and amyl nitrite. Such a mixture may further include SF6. However, little information about the insulating properties of this mixture is provided. International application WO 2008/073790, [3], describes a number of other dielectric gases that can be used in the field of electrical insulation and arcing extinction in medium and high voltage electrical appliances. There are other promising alternatives from a point of view of electrical and PRG characteristics, such as trifluoroiodomethane (CF3I). Indeed, the CF3I has a higher dielectric strength than SF6 in both homogeneous field and divergent field, for a PRG less than 5 and a residence time in the atmosphere of 0.005 year. Unfortunately, in addition to being expensive, CF3I has an average exposure value (EMC) of the order of 3 to 4 ppm and is classified as 3032828 6 among the carcinogenic, mutagenic and reprotoxic substances (CMR) category 3, which is prohibitive for use on an industrial scale.
    [0006] The international application WO 2012/080246, [4], describes the use of one (or more) fluoroketone (s) mixed with air as a means of electrical insulation and / or extinction of the arc. electric low environmental impact. Because of the high boiling points for the proposed fluids, ie 49 ° C for fluoroketone C6 and 23 ° C for fluoroketone C5, these fluids are found in the liquid state at pressures and temperatures common service minimums for medium and high voltage electrical equipment requiring inventors to add vaporization systems of the liquid phase or external heating of the apparatus to maintain the temperature of the apparatus above the temperature liquefaction of fluoroketones. This external vaporization and, above all, heating system complicates the design of the electrical appliance, decreases its reliability in the event of a power failure and generates an additional electricity consumption of up to about 100 MWh over the service life. the electrical appliance, which goes against the objective of reducing the environmental impact of the appliance and in particular the reduction of carbon emissions. From the point of view of reliability at low temperature, in the event of a break in the low temperature power supply, the gaseous phase of the fluoroketone (s) would liquefy strongly lowering the concentration of fluoroketone (s) in the gaseous mixture and thus decreasing the Isolation power of the device, which would be unable to hold the voltage in case of electric supply.
    [0007] It has also been proposed to use hybrid insulation systems combining gas insulation, for example with dry air, nitrogen or CO2, with solid insulation. As disclosed in European Patent Application Laid-Open No. 1,724,802, [5], this solid insulation consists, for example, in covering the live parts which have a high electrical gradient by an epoxy resin or analogous, which reduces the field to which live parts are subjected. International Application WO 2014/037566, [6], proposes such a hybrid insulation system in which the gaseous isolation consists of heptafluoroisobutyronitrile in a dilution gas. However, the insulation thus obtained is not equivalent to that provided by the SF6 and the use of these hybrid systems necessitates an increase in the volume of electrical appliances compared to that allowed by SF6 insulation.
    [0008] Concerning the cutting of an electric arc without SF6, various solutions exist: cut in the oil, cut in the ambient air, cut with vacuum bulb. However, the devices with cut in the oil have the major disadvantage of exploding in 30 cases of no cut or internal defect. Room air interrupters are generally large, costly and environmentally sensitive (moisture, pollution), while appliances, especially disconnect switches, with a vacuum interrupter are very expensive and very small. present on the market 5 in the field of high voltage higher than 72.5 kV. In view of the foregoing, the inventors have thus set themselves the general goal of finding an alternative to SF6 having a low environmental impact compared to an apparatus identical to SF6 while maintaining the characteristics of the apparatus, from the point of view its insulating and cutting capacity, close to those of SF6 without significantly increasing the size of the device and the pressure of the gas inside.
    [0009] In addition, the inventors have set themselves the goal of maintaining the operating temperature ranges of the electrical appliance, similar to those of equivalent SF6 appliances, without any external heating means. More specifically, the inventors have set themselves the goal of finding an insulation system comprising at least one gas or a mixture of gases which, while having electrical insulation and electric arc extinction properties sufficient for a application in the field of high voltage electrical equipment and in particular comparable to those of SF6, has a low or no impact on the environment. They have also set themselves the goal that this insulation system and in particular the gas or the gas mixture that it comprises is not toxic to man and the environment.
    [0010] It has also been their goal that the insulation system, and in particular the gas or the gas mixture, have a cost of manufacture or purchase compatible with use on an industrial scale.
    [0011] 5 They have also set themselves the goal that the medium or high voltage electrical equipment based on this insulation system and in particular the gas or the gas mixture has a size and pressure close to equivalent apparatus insulated with SF6 and does not present no liquefaction at the minimum use temperature without the addition of an external heating source. PRESENTATION OF THE INVENTION The objects set and still others are achieved by the invention which proposes the use of a particular gaseous mixture, possibly combined with a solid insulation allowing to obtain a medium or high voltage electrical apparatus to low environmental impact and improved breaking capacity.
    [0012] Thus, the insulating system used in the context of the present invention is based on a gaseous medium comprising heptafluoroisobutyronitrile mixed with tetrafluoromethane as electrical insulating gas and / or electric arc extinguishing in a medium or high voltage electrical appliance. In general, the present invention proposes a medium or high voltage electrical apparatus comprising a sealed enclosure in which there are electrical components and a gaseous mixture ensuring electrical insulation and / or extinguishing of the electric arcs likely to occur in this enclosure, the gaseous mixture comprising heptafluoro isobutyronitrile and tetrafluoromethane. In the electrical apparatus according to the present invention, the gaseous insulation employs a gaseous mixture comprising heptafluoroisobutyronitrile and tetrafluoromethane. In what precedes and what follows, the terms "medium voltage" and "high voltage" are used in their usual acceptance, namely that the term "medium voltage" refers to a voltage that is greater than 1000 volts AC. and at 1500 volts DC but not exceeding 52,000 volts AC and 75,000 volts DC, while the term "high voltage" refers to a voltage that is strictly greater than 52,000 volts AC and at 75,000 volts DC. Heptafluoroisobutyronitrile of formula (I): (CF3) 2CFCN (I), hereinafter designated as -C3F7CN, corresponds to 2,3,3,3-tetrafluoro-2-trifluoromethylpropanenitrile, CAS number: 42532-60 -5. This compound has (i) a boiling point of -4.7 ° C to 1013 hPa (boiling point measured according to ASTM D1120-94 "Standard Test Method for Boiling Point of Engine Coolants"); (ii) a molecular weight of 195 g; (iii) a GWP of 2210 (calculated over 100 years according to the IPCC 2013 method); and (iv) an Ozone Depletion Potential (PDO) of 0.
    [0013] The relative dielectric strength of the heptafluoroisobutyronitrile of formula (I), normalized with respect to the gas which one wishes to replace ie SF6 and compared with that of N2, is given in Table I below, said dielectric strength being measured at atmospheric pressure, under direct tension, between two steel electrodes 2.54 cm in diameter and spaced 0.1 cm apart. SF6 N2 C3F7CN 1, 0 0.35-0.4 2.6 Table I Tetrafluoromethane or carbon tetrafluoride of formula CF4 and CAS number: 75-73-0 shows: (i ') a boiling point of -127.8 ° C to 1013 hPa (boiling point measured according to ASTM D1120-94); (ii ') a molecular weight of 88 g; (iii ') a GWP of 6500 (calculated over 100 years according to the IPCC 2013 method, and (iv') a PDO of 0.
    [0014] The relative dielectric strength of the tetrafluoro methane of formula CF 4, normalized with respect to the gas which it is desired to replace ie SF 6, is given in Table II below, said dielectric strength being measured at atmospheric pressure, under DC voltage, between two steel electrodes 2.54 cm in diameter and spaced 0.1 cm. Accordingly, heptafluoroisobutyronitrile and tetrafluoromethane as previously defined, which are neither toxic, nor corrosive, nor flammable and which have a low GWP compared to that SF6, are provided with electrical insulation properties and extinguishing electric arcs suitable to allow them to optionally replace in mixture with a dilution gas, the SF6 as insulating gas and / or arc extinguishing in electrical appliances of medium or high voltage. It should be noted, however, that the GFR of tetrafluoro methane, although lower than that of SF6, is high, it is therefore necessary to minimize the presence of this compound in the gaseous mixture and to determine its quantity as a function of the GWP targeted for this gaseous mixture. More particularly, the present invention provides a low environmental impact gas insulation comprising a gaseous mixture with low environmental impact (low GWP to SF6) compatible with the minimum operating temperatures of the electrical equipment and having dielectric properties, improved cut-off and heat dissipation compared to conventional gases such as CO2, air or nitrogen.
    [0015] In the context of the present invention, heptafluoroisobutyronitrile and tetrafluoromethane are present in medium or high voltage electrical apparatus exclusively or almost exclusively in the gaseous state under all the temperature conditions at which the gaseous medium is intended to be used. subject, 3032828 13 when confined in the electrical apparatus. For this purpose, heptafluoroisobutyronitrile and tetrafluoromethane should be present in the electrical apparatus at partial pressures which are selected according to the saturation vapor pressures which these compounds respectively exhibit at the minimum temperature of use of the device. electrical appliance. The minimum operating temperature of an electrical appliance is the lowest temperature at which this appliance is intended to be used. Heptafluoroisobutyronitrile and tetrafluoro methane may thus be the only components of the gaseous medium confined in the medium or high voltage electrical apparatus.
    [0016] However, in view of the filling pressure levels generally recommended for medium or high voltage electrical appliances which are typically several bars and taking into account, on the one hand, the liquefaction temperature of heptafluoro isobutyronitrile on the one hand, atmospheric pressure (1013.25 hPa) and, on the other hand, the GWP of tetrafluoromethane, heptafluoroisobutyronitrile and tetrafluoromethane will most often be used diluted in at least one other gas so as to obtain the pressure level of recommended filling for the electrical apparatus concerned while ensuring the maintenance in the gaseous state of heptafluoroisobutyronitrile throughout the range of operating temperatures of this apparatus. In this case, according to the invention, this other gas, said dilution gas or carrier gas or buffer gas, is chosen from gases that meet the following four criteria: (1) have a very low boiling point less than the minimum operating temperature of the apparatus, this boiling temperature being typically at or below -50 ° C above standard pressure; (2) have a dielectric strength greater than or equal to that of carbon dioxide under identical test conditions (same apparatus, same geometrical configuration, same operating parameters, etc.) as those used to measure the dielectric strength of the dioxide; of carbon ; (3) be devoid of toxicity to humans and the environment; and (4) having a lower GWP than that of the heptafluoroisobutyronitrile / tetrafluoromethane mixture so that the dilution of this mixture by the dilution gas also has the effect of lowering the environmental impact of the mixture since the GWP of a mixture Gaseous is a weighted average, derived from the sum of the mass fraction of each of the substances multiplied by the GWP of each component. The dilution gases usually used are neutral gases whose GWP is very low, typically equal to or less than 500 and, more preferably, equal to or less than 10. Gases having all of these properties are, for example, air and preferably dry air (GWP of 0), nitrogen (GWP of 0), helium (GWP of 0), carbon dioxide (GWP of 1), oxygen (PRG 3032828 Of 0) and nitrous oxide (PRG 310). Also, any of these gases or their mixtures can be used as the diluent gas in the invention. In the context of the present invention, heptafluoroisobutyronitrile is present in the electrical apparatus at a partial pressure which is advantageously between 95 and 100% and, in particular, between 98 and 100% of the corresponding pressure, at the temperature filling the electrical apparatus with the saturation vapor pressure of heptafluoroisobutyronitrile the minimum temperature of use of the electrical apparatus. Thus, the dielectric properties of the gaseous medium in a direct line and on the path are as high as possible and are closest to those of SF6. In other words, in order to put the maximum amount of heptafluoroisobutyronitrile without generating a liquid phase at the minimum temperature of use of the apparatus according to the present invention, the composition of the gaseous medium is defined according to Raoult's law for the minimum temperature of use of the device, or even for a temperature slightly higher than the latter, in particular of 3 ° C. In particular, for a ternary mixture heptafluoroisobutyronitrile (i-C3F7CN) / tetrafluoromethane (CF4) / dilution gas, the pressures of each constituent are therefore defined by the following equation: Pi -C3F7CN + PCF4 Ptotale Pgaz dilution i -C3F7CN PCF4 PVS i -C3F7CN PVS CF4 3032828 16 with PVS ± c3F7cN = saturation vapor pressure of heptapfluoroisobutyronitrile and PVScF4 = saturation vapor pressure of tetrafluoromethane. Advantageously, in the context of the present invention, the minimum operating temperature Train is chosen from 0 ° C, -5 ° C, -10 ° C, -15 ° C, -20 ° C, -25 ° C, -30 ° C, -35 ° C, -40 ° C, -45 ° C and -50 ° C and, in particular, selected from 0 ° C, -5 ° C, -10 ° C, -15 ° C, -20 ° C, -25 ° C, -30 ° C, -35 ° C and -40 ° C.
    [0017] In a particular embodiment, the gaseous mixture used in the context of the present invention is a ternary mixture comprising or consisting of - from 1 to 20 mol% of i-C3F7CN; 1-40 mol% of CF4; and from 40 to 98 mol% of dilution gas. A particular example of a gaseous mixture that may be used in the context of the present invention comprises or consists of i-C3F7CN, CF4 and CO2.
    [0018] A more particular example of a gaseous mixture usable in the context of the present invention comprises or consists of 1 to 20 mol% of i-C3F7CN; from 1 to 40 mol% of CF4 and from 40 to 98 mol% of CO2.
    [0019] In order to improve the dielectric strength of the assembly, the gaseous mixture comprising heptafluoro isobutyronitrile and tetrafluoromethane can be used, in a hybrid insulation system, in combination with a solid insulation, in particular with a permittivity weak dielectric, applied in an insulating layer of variable thickness on the conductive parts 3032828 17 subjected to an electric field greater than the breakdown field of the medium or high voltage device without solid insulation. In fact, the medium or high voltage electrical apparatus according to the invention has electrical components which are not covered with a solid dielectric layer. In other words, in the sealed enclosure of the medium or high voltage electrical apparatus according to the present invention, there are electrical components covered with a solid dielectric layer of varying thickness. The dielectric / insulating layer implemented in the invention has a low relative permittivity. By "low relative permittivity" is meant a relative permittivity of less than or equal to 6. It will be recalled that the relative permittivity, also referred to as the dielectric constant, of a material, which is denoted by Er, is a dimensionless size that can be defined. by the following formulas (IV) and (V): Er = C / Co (IV), with E = (e * C) / S and CO = 1 / (36n * 109) (V) in which: E corresponds to the absolute permittivity (expressed in Farads / meter) of the material; - CO corresponds to the permittivity (expressed in Farads / meter) of the vacuum; C corresponds to the capacitance (expressed in farads) of a plane capacitor comprising two parallel electrodes between which is disposed a layer of the material for which it is desired to determine the permittivity, this layer representing a specimen; e corresponds to the distance (expressed in meters) between the two parallel electrodes of the flat capacitor, which corresponds, in our case, to the thickness of the specimen; and S corresponds to the area (in square meters) of each constituent electrode of the planar capacitor.
    [0020] In the context of the present invention, the capacitance is determined as in the IEC 60250-ed1.0 standard, namely by using a capacitor comprising two circular electrodes with a diameter ranging from 50 to 54 mm, integral with the test specimen 15 consisting of the material, these electrodes being obtained by spraying a conductive paint with a guard. The test specimen has dimensions of 100 mm × 100 mm and a thickness of 3 mm. The distance between the electrodes of the capacitor, which corresponds to the size e mentioned above, is therefore 3 mm. In addition, the capacitance is determined under an excitation level of 500 volts RMS, at a frequency of 50 hertz, at a temperature of 23 ° C. and a relative humidity of 50%. The duration of application of the aforementioned voltage is 1 min. In the context of the present invention, the term "insulating layer / dielectric of variable thickness" means that the dielectric material deposited or applied to the electrical components or conductive parts has varying thicknesses depending on the conductive part or part thereof. of conductor part on which it is deposited. The thickness of the layer does not vary during use of the electrical apparatus but is determined during the preparation of the elements constituting this apparatus.
    [0021] In the context of the invention, the insulating layer is applied in a layer of low or high thickness on the conductive parts subjected to an electric field greater than the breakdown field of the system without solid insulation.
    [0022] More particularly, the thickness of the insulating layer used in the context of the present invention being a function of the utilization factor of the electric field, ri, defined as the ratio of the average electric field (U / d) on the field maximum electric power, Emax (p = U / (Emax * d)), the layer is thick for use factors close to 0.3 ie between 0.2 and 0.4 and the layer is fine for factors using approaching 0.9 ie greater than 0.5 and in particular greater than 0.6.
    [0023] In the context of the present invention, the term "thick layer" means a layer with a thickness greater than 1 mm and less than 10 mm and "thin layer" a layer with a thickness of less than 1 mm, advantageously less than 500 mm. im, in particular between 60 and 100 μm. The solid insulating layer implemented in the context of the present invention may comprise a single dielectric material or several different dielectric materials. In addition, the composition of the insulating layer i.e. the nature of the dielectric material (s) it comprises may differ depending on the conductive part or part of the conductive part on which the solid insulating layer is deposited. In particular, in the context of the invention, the materials selected to produce the thick insulating layers have low relative permittivities, that is to say less than or equal to 6. In a particular embodiment, the dielectric permittivities of the insulating materials used to make the thick solid layers 10 have relative permittivities of the order of 3, or even lower ie relative permittivities less than or equal to 4 and in particular less than or equal to 3. As an example of materials suitable for producing the dielectric layers, solid and thick, of the electrical apparatus according to the invention, mention may be made of polytetrafluoroethylene, polyimide, polyethylene, polypropylene, polystyrene, polycarbonate, polymethyl methacrylate, polysulfone, polyetherimide, polyether ether ketone, parylene NTM, NuflonTM, silicone and the like. epoxy resin. With regard to the materials used to make the thin layers, the materials selected in the context of this invention have relative permittivities of the order of 3 i.e. between 2 and 4 and in particular between 2.5 and 3.5. By way of example of materials that can be used for producing the dielectric layers, solid and thin, of the electrical apparatus according to the invention, mention may be made of polytetrafluoroethylene, polyimide, polyethylene, polypropylene, polystyrene, polyamide and ethylene 3032828 21 Monochlorotrifluoroethylene parylene NTM, NuflonTM, HALARTM and HALAR CTM. According to the invention, this electrical apparatus can be, in the first place, a gas-insulated electrical transformer such as, for example, a power transformer or a measurement transformer. It may also be a gas-insulated line, aerial or underground, or a busbar for the transport or distribution of electricity. It can also be a connection element to other network equipment such as for example overhead crossings or bulkheads.
    [0024] Finally, it can also be an electrical device for connection / disconnection (also called apparatus or interrupting chamber) such as, for example, a circuit breaker such as a circuit breaker of the "dead tank" type, a puffer circuit breaker ("puffer" or "puffer"). self blast "), a dual-movement double-throw circuit breaker for arcing contacts, a thermal-effect self-blast circuit breaker in single-acting arc contacts, a thermal-purging self-blast circuit breaker with partial movement of the contact rod a switch, a disconnector such as an AIS for "Air-Insulated Swithgear" or a GIS for "Gas-Insulated Swithgear", a fuse-switch combination, an earthing switch or a contactor.
    [0025] The present invention also relates to the use of a gaseous mixture comprising heptafluoroisobutyronitrile and tetrafluoromethane as electrical isolation gas and / or electric arc extinguishing in a medium or high voltage electrical appliance whose components In addition, the electric wires can be covered with a solid insulating layer of variable thickness as previously defined. Other features and advantages of the invention will emerge from the additional description which follows given by way of illustration and not limitation. DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS The invention is based on the use of a particular low environmental impact gas mixture with improved cleavage capacities combining heptafluoroisobutyronitrile and tetrafluoromethane as previously defined, with or without dilution gas. As used herein, the terms "dilution gas", "neutral gas" or "buffer gas" are equivalent and can be used interchangeably. Advantageously, heptafluoroisobutyronitrile and tetrafluoromethane are present in the electrical apparatus in exclusively or almost exclusively gaseous form and this, over the entire range of operating temperatures of this apparatus. It is therefore appropriate that the partial pressure at which the heptafluoroisobutyronitrile is present in the electrical apparatus 30 be chosen as a function of the saturation vapor pressure (PVS) that this compound exhibits at the lowest temperature of use of said apparatus. . However, since the gas filling of the electrical apparatus is usually done at room temperature, the pressure referred to for filling the electrical apparatus with heptafluoroisobutyronitrile is the pressure PTremp which corresponds, for example, to the filling temperature. ° C., at the saturation vapor pressure PVSTmin that this compound exhibits, respectively, at the minimum use temperature Tmin of said electrical apparatus. This correspondence is given, for each compound, by the formula: PTremp = PVS Tmin x 293) / Train 15 with Tmin expressed in Kelvins. By way of example, Table III below shows the saturated vapor pressures, denoted PVS ± -c3F7cN and expressed in hectopascals, that heptafluoroisobutyronitrile exhibits at temperatures of 0 ° C., 20 ° -5 ° C., -10 ° C. C, -15 ° C, -20 ° C, -25 ° C, -30 ° C, -35 ° C and -40 ° C, as well as the pressures, denoted Pi-C3F7CN and expressed in hectopascals, which correspond to these saturated vapor pressures reduced to 20 ° C. Temperatures MrSi-C3F7CN Pi-C3F7CN (hPa) (hPa) 0 ° C 1177 1264 -5 ° C 968 1058 -10 ° C 788 877 -15 ° C 634 720 -20 ° C 504 583 3032828 24 -25 ° C 395,466 -30 ° C 305 368 -35 ° C 232 286 -40 ° C 173 218 Table III: saturation vapor pressures of i-C3F7CN With regard to tetrafluoromethane, with a boiling point of about -128 ° C, this compound 5 is still in the gaseous state for the maximum pressures and minimum temperatures customary for medium and high voltage electrical appliances. As a result, saturation vapor pressures are not reported for this compound as never reached.
    [0026] Thus, for example, an electrical apparatus intended to be used at a minimum temperature of -30 ° C. will be filled, at the temperature of 20 ° C., with a partial pressure of heptafluoroisobutyronitrile which will not exceed 368 hPa at 20 ° C. if it is desired that this compound be kept in a gaseous state in this apparatus over the entire range of use temperatures thereof. Depending on the electrical apparatus, the total gas filling pressure that is recommended varies. It is, however, typically several bars, i.e., several hundred kPa. Also, although in theory, heptafluoroiso butyronitrile and tetrafluoromethane may represent the only components of the gaseous medium, they will most often be supplemented with a dilution gas (or carrier gas or buffer gas) making it possible to obtain the recommended filling pressure level.
    [0027] Preferably, the dilution gas is chosen from gases which have, on the one hand, a very low boiling point, less than or equal to the minimum temperature of use of the apparatus, and on the other hand, a dielectric strength greater than or equal to that of carbon dioxide under identical test conditions (same apparatus, same geometrical configuration, same operating parameters, ...) as those used to measure the dielectric strength of the carbon. In addition, it is preferred that the dilution gas be non-toxic and have very little or no GWP, so that the dilution of tetrafluoromethane with this gas also has the effect of lowering the environmental impact of this compound since the PRG of a gaseous mixture is related to the partial pressures of each of its components. Also, the dilution gas is preferably carbon dioxide whose GWP is equal to 1, nitrogen, oxygen or air, preferably dry, whose GWP is equal to 0, or mixtures thereof. Since heptafluoroisobutyronitrile and tetrafluoromethane have a higher dielectric strength than gases that can be used as a dilution gas, it is desirable to optimize the filling of the electrical apparatus with heptafluoro isobutyronitrile and tetrafluoromethane. The electrical apparatus will therefore be filled with heptafluoroisobutyro nitrile at a partial pressure which will advantageously be between 95 and 100% and, more preferably, between 98 and 100% of the corresponding pressure, at the filling temperature, at saturation vapor pressure that this compound exhibits at the minimum temperature of use of the electrical apparatus.
    [0028] In other words, the heptafluoroisobutyronitrile will preferably be present in the gaseous medium in a molar percentage which will be between 95 and 100% and, more preferably, between 98 and 100% of the molar percentage M given, for each compound, by the formula: M = (P Temp / Pmilieu) × 100, in which - PTremp represents the pressure which corresponds, at the filling temperature and for heptafluoroisobutyronitrile, to the saturated vapor pressure that this compound exhibits at the minimum temperature of use of the electrical apparatus; and - middle represents the total pressure of the gaseous medium (i-C3F7CN + CF4 + dilution gas) at the filling temperature.
    [0029] A particular example of a ternary gas mixture which can be used within the scope of the invention at a minimum temperature of -30 ° C. consists of - 4.1 mol% of i-C3F7CN; - 20 mol% of CF4; and 25 - 75.9 mol% of CO2. Such a mixture makes it possible to obtain a reduction of about 90.2% of the carbon equivalent relative to pure SF6 (Table V).
    [0030] 3032828 27 Gas Mass PRG% mol Molar fraction (% P) by mass (% w) i-C3F7CN 195 2210 4.10% 13.55% CF4 88 6500 20.00% 29.84% CO2 44 1 75.90% 56 , 61% PRG mixture = 2239 Reduction / SF6 = 90.2% Table V A second particular example of a ternary gas mixture that can be used in the context of the invention at a minimum temperature of -25 ° C. consists of - 6.3 mol% of i-C3F7CN; - 20 mol% of CF4; and - 73.7 mol% of CO2.
    [0031] Such a mixture makes it possible to obtain a reduction of the order of 90.0% of the carbon equivalent relative to pure SF6 (Table VI). Gas Mass PRG% mol Molar fraction (% P) mass (% w) i-C3F7CN 195 2210 6,30% 19,71% CF4 88,600 20,00% 28,24% CO2 44 1 73,70% 52,04 % PRG mixture = 2272 Reduction / SF6 = 90.0% Table VI From a practical point of view, after evacuating with the aid of an oil vacuum pump, it is possible to fill a commercial appliance with 5 bars (500 kPa) provided for use at -30 ° C using a gas mixer to control the ratio between the pressures of heptafluoroisobutyronitrile and tetrafluoromethane and the pressure of the diluent gas; The ratio is kept constant and equal to 6.3 mol% for heptafluoroisobutyronitrile and 20 mol% for tetrafluoromethane throughout the filling by the use of precision mass flow meters. Preferably, the vacuum (0 to 0.1 kPa) will have been done previously in the apparatus. It should also be noted that future electrical apparatus will be equipped with anhydrous calcium sulfate (CaSO 4) molecular sieve adsorbing the moisture of the gas, thereby reducing the toxicity and acidity of the gaseous medium after partial discharges by molecules that may have toxicity, typically HF. In addition, at the end of life or after breaking tests, the gaseous medium can be recovered by conventional recovery techniques using a compressor and a vacuum pump. Heptafluoroisobutyronitrile and tetrafluoromethane can then be separated from the dilution gas using a zeolite capable of trapping only that dilution gas which is smaller in size; alternatively, a selective separation membrane allowing the dilution gas to escape and keeping heptafluoroisobutyronitrile and tetrafluoromethane since these have a higher molecular weight can be used. Of course, any other option is conceivable.
    [0032] Thus, the present invention proposes gaseous mixtures with a low environmental impact with very significant CO2 equivalent reduction factors (of the order of 90%) compatible with the minimum operating temperatures of the electrical equipment. and having improved dielectric properties compared to typical gases such as CO2, air or nitrogen and close to those of pure SF6 while improving its breaking capacity. This gaseous medium can advantageously replace the SF6 used in electrical appliances, without substantially modifying their design: the production lines can be kept, with a simple change of the gaseous filling medium.
    [0033] In order to obtain the dielectric equivalence with respect to SF6 (to reach 100% of the SF6 resistance), without degrading its low temperature performance or increasing its total pressure, the gaseous mixture presented above can be used in combination with a Solid insulation of weak dielectric permittivity applied to the conductive parts subjected to an electric field higher than the breakdown field of the system without solid insulation. The solid insulation implemented in the context of the present invention is in the form of a layer whose thickness varies for a given electrical appliance. Indeed, the insulating layer used may have a small thickness (thin or thin layer) or a thick (thick layer).
    [0034] The thickness of the insulating layer being a function of the utilization factor of the electric field, ri, defined as the ratio of the average electric field (U / d) to the maximum electric field, Emax (n = U / (Emax * d)), the layer is thick for use factors close to 0.3 and the layer is fine for use factors approaching 0.9. This solution therefore makes it possible to reduce the maximum electric field on the gaseous phase and thus to increase the electrical resistance of the so-called mixed total insulation composed in series of the solid insulation and the gaseous insulation. This phenomenon of reduction of the electric field on the gas phase is more pronounced when the dielectric permittivity of the solid layer is low.
    [0035] REFERENCES [1] European patent application, on behalf of 5 Mitsubishi Denki Kabushi Kaisha, published under No. 0 131 922 on 23 January 1985. [2] US Patent 4,547,316, in the name of Mitsubishi Denki Kabushiki Kaisha , published October 15, 1985. [3] International Application WO 2008/073790, on behalf of Honeywell International Inc., published June 19, 2008. [4] International Application WO 2012/080246, on behalf of ABB Technology AG. , published on 21 June 2012. [5] European patent application, on behalf of Mitsubishi Denki Kabushiki Kaisha, published under No. 1,724,802 on 22 November 2006. 20 [6] International Application WO 2014/037566, in the name of Alstom Technology Ltd, published March 13, 2014. 25
    权利要求:
    Claims (14)
    [0001]
    REVENDICATIONS1. Medium or high voltage electrical apparatus comprising a sealed enclosure in which there are electrical components and a gas mixture ensuring electrical insulation and / or extinguishing of electric arcs likely to occur in this enclosure, the gas mixture comprising heptafluoroisobutyronitrile and tetrafluoromethane.
    [0002]
    2. Electrical apparatus according to claim 1, characterized in that said gaseous mixture further comprises a dilution gas.
    [0003]
    3. Electrical apparatus according to claim 2, characterized in that said dilution gas is selected from carbon dioxide, nitrogen, oxygen, air and mixtures thereof.
    [0004]
    4. Electrical apparatus according to any one of claims 1 to 3, characterized in that the heptafluoro isobutyronitrile is present in said electrical apparatus at a partial pressure selected according to the saturated vapor pressure that heptafluoroisobutyronitrile exhibits at the temperature minimum use of said electrical apparatus.
    [0005]
    5. Electrical apparatus according to any one of claims 1 to 4, characterized in that the heptafluoro isobutyronitrile is present in said electrical apparatus at a partial pressure which is between 95 and 100% of the corresponding pressure, the filling temperature of said electrical apparatus at the saturation vapor pressure exhibited by heptafluoroisobutyronitrile at the minimum temperature of use of said electrical apparatus.
    [0006]
    6. Electrical apparatus according to claim 4 or 5, characterized in that said minimum temperature of use of said electrical apparatus is selected from 0 ° C, -5 ° C, -10 ° C, -15 ° C, -20 ° C, -25 ° C, -30 ° C, -35 ° C, -40 ° C, -45 ° C and -50 ° C and, in particular, selected from 0 ° C, -5 ° C, -10 ° C, -15 ° C, -20 ° C, -25 ° C, -30 ° C, -35 ° C and -40 ° C. 15
    [0007]
    7. Electrical apparatus according to any one of claims 1 to 6, characterized in that said gaseous mixture is a ternary mixture consisting of - 1 to 20 mol% of i-C3F7CN; from 1 to 40 mol% of CF4; and 20 - from 40 to 98 mol% of dilution gas and in particular of CO2.
    [0008]
    8. Electrical apparatus according to any one of claims 1 to 7, characterized in that, in said sealed chamber, there are electrical components covered with a solid dielectric layer of varying thickness.
    [0009]
    Electrical apparatus according to claim 8, characterized in that the thickness of said solid dielectric layer is a function of the electric field utilization factor, r 1, defined as the ratio of the average electric field (U / d). ) on the maximum electric field, Emax (ri = U / (Emax * d)), said solid dielectric layer is a thick layer having a thickness greater than 1 mm and less than 10 mm for utilization factors between 0 , 2 and 0.4.
    [0010]
    Electrical apparatus according to claim 9, characterized in that the material (s) selected for producing said thick solid dielectric layer has a relative permittivity of less than or equal to 6, in particular less than equal to 4 and especially less than or equal to 3. 15
    [0011]
    Electrical apparatus according to claim 8, characterized in that, the thickness of said solid dielectric layer being a function of the utilization factor of the electric field, ri, defined as the ratio of the average electric field (U / d) on the maximum electric field, Emax (ri = U / (Emax * d)), said solid dielectric layer is a thin layer having a thickness of less than 1 mm, advantageously less than 500 μm, in particular between 60 and 100 μm for factors use greater than 0.5 and in particular greater than 0.6.
    [0012]
    12. Electrical apparatus according to claim 11, characterized in that the (or) material (s) selected (s) for producing said thin solid dielectric layer has (s) a relative permittivity of between 2 and 4 and in particular between 2, 5 and 3.5. 3032828
    [0013]
    Electrical apparatus according to any one of the preceding claims, characterized in that said apparatus is a gas-insulated electrical transformer, a gas-insulated line for the transport or distribution of electricity, a connection element to the others. network equipment or an electrical device for connection / disconnection. 10
    [0014]
    14. Use of a gaseous mixture comprising heptafluoroisobutyronitrile and tetrafluoro methane as defined in any one of claims 1 to 7, in a medium or high voltage electrical apparatus whose electrical components are optionally covered by a solid insulating layer of variable thickness as defined above in any one of claims 8 to 12, as electric insulation gas and / or electric arc extinguishing. 20
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    US20180040391A1|2018-02-08|
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    EP3257059A1|2017-12-20|
    CN107430901A|2017-12-01|
    BR112017016903A2|2018-03-27|
    FR3032828B1|2017-03-17|
    WO2016128571A1|2016-08-18|
    JP2018506947A|2018-03-08|
    KR20170118130A|2017-10-24|
    MX2017010448A|2017-11-28|
    引用文献:
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    FR2995462A1|2012-09-10|2014-03-14|Alstom Technology Ltd|MEDIUM OR HIGH VOLTAGE ELECTRICAL APPARATUS WITH LOW ENVIRONMENTAL IMPACT AND HYBRID INSULATION|CN112578036A|2020-11-06|2021-03-30|武汉大学|Method for judging compatibility of heptafluoroisobutyronitrile and ethylene propylene diene monomer material|US7807074B2|2006-12-12|2010-10-05|Honeywell International Inc.|Gaseous dielectrics with low global warming potentials|
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    DE102017105982B4|2017-03-21|2022-03-03|Fritz Driescher KG Spezialfabrik für Elektrizitätswerksbedarf GmbH & Co.|Dielectric medium and gas-insulated switchgear filled with it|
    CN109493995A|2018-09-25|2019-03-19|上海交通大学|Mesohigh device housings filled with seven fluorine isobutyronitriles and difluoromethane mixed gas|
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    优先权:
    申请号 | 申请日 | 专利标题
    FR1551216A|FR3032828B1|2015-02-13|2015-02-13|GAS INSULATED MEDIUM OR HIGH VOLTAGE ELECTRICAL APPARATUS COMPRISING HEPTAFLUOROISOBUTYRONITRILE AND TETRAFLUOROMETHANE|FR1551216A| FR3032828B1|2015-02-13|2015-02-13|GAS INSULATED MEDIUM OR HIGH VOLTAGE ELECTRICAL APPARATUS COMPRISING HEPTAFLUOROISOBUTYRONITRILE AND TETRAFLUOROMETHANE|
    US15/550,599| US20180040391A1|2015-02-13|2016-02-12|Gas-insulated medium-or high-voltage electrical apparatus including heptafluoroisobutyronitrile and tetrafluoromethane|
    JP2017541952A| JP2018506947A|2015-02-13|2016-02-12|Gas-insulated medium or high voltage electrical equipment including heptafluoroisobutyronitrile and tetrafluoromethane|
    CN201680010261.9A| CN107430901A|2015-02-13|2016-02-12|Gas-insulated medium-pressure or high pressure electrical equipment comprising seven fluorine isobutyronitriles and tetrafluoromethane|
    CA2976018A| CA2976018A1|2015-02-13|2016-02-12|Gas-insulated medium- or high-voltage electrical apparatus including heptafluoroisobutyronitrile and tetrafluoromethane|
    PCT/EP2016/053079| WO2016128571A1|2015-02-13|2016-02-12|Gas-insulated medium- or high-voltage electrical apparatus including heptafluoroisobutyronitrile and tetrafluoromethane|
    EP16704609.3A| EP3257059A1|2015-02-13|2016-02-12|Gas-insulated medium- or high-voltage electrical apparatus including heptafluoroisobutyronitrile and tetrafluoromethane|
    BR112017016903A| BR112017016903A2|2015-02-13|2016-02-12|medium or high voltage equipment and use of a gas mixture|
    KR1020177025559A| KR20170118130A|2015-02-13|2016-02-12|Gas-insulated medium voltage or high voltage electrical apparatus comprising heptafluoroisobutyronitrile and tetrafluoromethane|
    MX2017010448A| MX2017010448A|2015-02-13|2016-02-12|Gas-insulated medium- or high-voltage electrical apparatus including heptafluoroisobutyronitrile and tetrafluoromethane.|
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