NL2017157B1 - Use of a fluorocarbon liquid for insulating electric devices and electric device immersed in an insulation liquid - Google Patents
Use of a fluorocarbon liquid for insulating electric devices and electric device immersed in an insulation liquid Download PDFInfo
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- NL2017157B1 NL2017157B1 NL2017157A NL2017157A NL2017157B1 NL 2017157 B1 NL2017157 B1 NL 2017157B1 NL 2017157 A NL2017157 A NL 2017157A NL 2017157 A NL2017157 A NL 2017157A NL 2017157 B1 NL2017157 B1 NL 2017157B1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/08—Cooling; Ventilating
- H01F27/10—Liquid cooling
- H01F27/18—Liquid cooling by evaporating liquids
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Abstract
The present invention relates to the use of a fluorocarbon liquid as a liquid for insulating an electric device which is immersed in said liquid in a hazardous, explosive, environment. The present invention is moreover related to an electric device immersed in an insulation liquid comprising a fluorocarbon, preferably a (per)fluorinated alkane.
Description
Use of a fluorocarbon liquid for insulating electric devices and electric device immersed in an insulation liquid
Description
The present invention relates to the use of a fluorocarbon liquid for insulating an electric or electronic device, component or equipment. In other words, the present invention relates to the use of a fluorocarbon liquid in which an electric device is immersed. The use of a fluorocarbon liquid according to the present invention is mainly related to insulating an electric device in such a way that the surrounding gases cannot contact said electric device; in other words the fluorocarbon liquid acts as a barrier for gas, it is a gas-insulating liquid. The invention also relates to an gas-insulated electric or electronic device, component or equipment. In an embodiment, the invention also relates to an electrical-insulated electric or electronic device, component or equipment.
Dielectric fluids are used in the electrical industry to achieve electrical insulation between live parts and as cooling means. Examples of these electrically insulating liquids are mineral oil, silicone fluid, and synthetic hydrocarbon oils used in transformers, power cables and capacitors. Examples of such fluids are described in patent application US 4082866, EP0154993, and EP0467345. In addition, biodegradable fluids have also been used for electrically insulating and cooling electrical devices, as described in US 2002/0027219 and EP 2128874.
However, the previously described liquids, e.g. mineral oils can corrode materials that will be immersed therein, which is clearly undesirable. Moreover, mineral oils deteriorate rapidly (e.g. due to thermal decomposition or moisture contamination), leading to a high propensity to form sludge and sediment.
Therefore, there is a need for electric devices that may be used in explosives atmosphere and to novel insulation, in particular gas-insulation but also electrical-insulation, more preferably gas- and electrical-insulation, for said devices. This gas-insulation is needed in order to avoid surrounding gases to contact said electric devices, especially when said devices are to be located in explosive environments, as defined in the ATEX directive and/or the lECEx system for certification to standards relating to equipment for use in explosive atmospheres.
It is an object of the present invention to provide novel gas-insulation and preferably electrical-insulation liquids that may be used in explosive environments. It is an object of the present invention to provide novel gas-insulation liquids that are not corrosive to the equipment used.
One or more of the above cited objects are achieved by the several aspects and embodiments of the present invention as discussed below.
Summary of the invention
In a first aspect, the present invention relates to the use of a fluorocarbon as a liquid for insulating an electric device which is immersed in said liquid. The invention is hence related to the use of a fluorocarbon liquid as insulating liquid for gas-insulation of an electric device which is immersed in said liquid. It should be noted that one or more additives may be added to said fluorocarbon to form said liquid for insulating.
In an embodiment, maximally 5 wt.% of additives may be present in said liquid in addition to one or more fluorocarbons, based on the total weight of said liquid. In a second aspect, the present invention is related to gas-insulated electric device immersed in an insulation liquid comprising or consisting of at least one fluorocarbon liquid. In an embodiment, the invention is related to gas- and electrical-insulated electric device.
The key to the present invention is to insulate an electric device for gases in order to avoid surrounding gases to contact said electric devices. Said insulation according to the present invention is carried out by the use of a fluorocarbon liquid.
Definitions
The following definitions are used in the present description.
Fluorocarbon a used in the present description means a compound comprising carbon atoms and fluorine atoms and optionally other atoms, such as hydrogen and oxygen atoms. (per)fluorinated alkane as used in the present description means a fluorinated or a perfluorinated alkane. A (per)fluoratined alkane according to the present invention includes preferably perfluorinated alkanes but also includes alkanes in which most, but not all hydrogen atoms have been replaced by fluorine atoms, such as for example alkanes comprising in addition to fluorine atoms also one or more alkyoxy groups, which are called perfluorinated alkoxy-alkanes. fluorinated alkane as used in the present description means is an alkane in which one or more of the hydrogen atoms have been replaced by fluorine atoms. perfluorinated alkane as used in the present description means an alkane in which all hydrogen atoms have been replaced by fluorine atoms. perfluorinated alkoxy-alkane as used in the present description means a perfluorinated alkane comprising at least one alkoxy group, such as a methoxy or ethoxy groups. A nonlimiting example of perfluorinated alkxoy-alkanes according to the present invention is 1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-(trifluoromethyl)-pentane. “Fire point” as used in the present description means the lowest temperature of a substance at which the vapor of that substance will continue to burn for at least 5 second after ignition by an open flame. Fire point in the present application is determined according to ISO 2592:2000. “Flash point” as used in the present description means the lowest temperature of a substance at which vapors of the material will ignite, given an ignition source. Flash point is measured according to the method in IS02719:2002. “Kinematic viscosity” as used in the present description means the resistance to flow of a fluid under gravity. The kinematic viscosity of a fluid is given by the ratio of the dynamic viscosity to the density of the fluid. Kinematic viscosity in the present application is determined according to ISO 3104:1994. “Electrical breakdown voltage” as used in the present application description means the minimum voltage at which a substance becomes electrically conductive. Electrical breakdown voltage in the present application is determined according to IEC 60156:1995. “Volume resistivity” as used in the present application description means a parameter that quantifies how strongly a substance opposes the flow of electric current. Volume resistivity in the present application is determined according to I EC 60247:2004. “Pour point” as used in the present application description means the temperature at which a liquid becomes semi solid and loses its flow characteristics. Pour point in the present application is determined according to ISO 3016:1994. “Acidity” as used in the present application description means a value for the acid neutralization of a liquid according to IEC 62021-1:2003.This is a measure of how much a liquid has oxidized and thus deteriorated, and how great is the propensity to form sludge and sediment. “Oxidation stability” as used in the present application description means the parameter that measures the tendency of a substance to react with oxygen. Oxidation stability in the present application is determined according to IEC 61125:1992 and is given as a percentage of sludge that is formed. “Surface load” as used in the present application description means the maximum surface load which is the maximum energy dissipated on a surface in contact with the liquid where the liquid does not overheat.
Electric device is meant to encompass electric or electronic device, component or equipment when used in the present invention.
Detailed description of the invention
The present invention and several embodiments are disclosed in more detail below. The invention relates to the use of a fluorocarbon as liquid for insulating an electric device, which is immersed in said liquid. In a first aspect, the present invention relates to the use of a fluorocarbon liquid as insulating liquid for gas-insulation of an electric device which is immersed in said liquid.
An electric device immersed in an insulation liquid that is present in a enclosure needs to be powered. This can be done by one more conductors through an internal or external wall of an enclosure; this is called a bushing. In an embodiment, the electric device is powered through bushings that connect to equipment that is suited for use in EPL b or c as described in IEC 60079 or Zone 1 or 2 according to EN 60079 areas. The other side of this device is wired.
When the immersed electric device according to the present invention is powered, it has power losses that are converted into heat. This production of heat warms up the liquid, which heat is partly dissipated (and hence the liquid partly cooled) by the natural convection of the liquid in its enclosure or in some cases also by a liquid treatment system if present. The liquid may also be cooled by electric or mechanical means such as a radiator or a fan, this may then be referred to as a liquid treatment system.
When the electric device is immersed in the inventive fluorocarbon liquid, gasses cannot contact the electrics; therefore, gasses cannot get in touch with the possible hot spots in the device and reaction between said gasses and possible ignition sources is avoided.
In an embodiment of both the first and second aspects of the present invention, said electric device immersed in said liquid is being used in an atmosphere according to the ATEX directive 2014/34/EU related to equipment for potentially explosive atmospheres.
In an embodiment of both the first and second aspects of the present invention, said electric device is being used in an atmosphere according to the lECEx system for certification to standards relating to equipment for use in explosive atmospheres. The IEC 60079 series describe the standards for equipment for use in hazardous atmospheres.
In an embodiment of both the first and second aspects of the present invention, said electric device immersed in said liquid is being used in an atmosphere that is both according to the ATEX directive 2014/34/EU or succeeding versions of the ATEX directive related to equipment for potentially explosive atmospheres and according to the lECEx system for certification to standards relating to equipment for use in explosive atmospheres.
In an embodiment of both the first and second aspects of the present invention, said electric device immersed in said liquid is being used in an atmosphere that is according to one or more of the following certifications, “Certificate TR CU (Technical Reglament
Conformity Certificate TRCU)”for Russia, National Electrical Code (NEC) where the 500 series (NEC-500) have a different definition for hazardous areas than the NEC-505 both of which are included for the USA, CEC (Canadian Electrical Code) for Canada and Inmetro (National Institute of Metrology, Standardization and Industrial Quality) for Brazil. In an embodiment, the liquid complies with all of the requirements as stipulated in one or more of the above certificates. These certificates and all requirements are incorporated by reference into the present patent application.
In an embodiment of both the first and second aspects of the present invention, said fluorocarbon liquid is not flammable. A non-flammable liquid is suitable for use in hazardous environments, such as explosive environments.
In an embodiment of both the first and second aspects of the present invention, said fluorocarbon liquid has a fire point as measured according to ISO 2592:2000 of at least 200 °C, preferably at least 300 °C, more preferably at least 400 °C.
At a lower fire point, the fluorocarbon may ignite during the operation of the electrical device, which would make said immersed electric device unsuitable for use in explosive atmospheres.
In an embodiment of both the first and second aspects of the present invention, wherein said fluorocarbon liquid has a kinematic viscosity as measured according to ISO 3104:1994 at 25 °C of at most 100 cSt, preferably at most 50 cSt, more preferably at most 25 cSt, even more preferably at most 10 cSt, most preferably between 0.5 cSt and 2 cSt.
At a higher kinematic viscosity, the fluorocarbon will lose its ability to flow freely and this might cause hot spots, which will ignite the gases in the explosive atmosphere.
In an embodiment of both the first and second aspects of the present invention, said fluorocarbon liquid has an electrical breakdown voltage as measured according to I EC 60156:1995 of at least 30 kV, preferably at least 40 kV, such as between 30 kV and 40 kV.
At a lower electrical breakdown voltage, the fluorocarbon will break down at lower voltages, which will cause the fluorocarbon to become electrically conductive, losing then its insulating properties.
In an embodiment of both the first and second aspects of the present invention, said fluorocarbon liquid has a volume resistivity as measured according to I EC 60247:2004 at 25°C at least 1x1012 Qm, most preferably between 1x1012 Om and 1x1013 Qm.
At a lower volume resistivity, the fluorocarbon will lose its insulating properties; therefore, the fluorocarbon would not be suitable for safe use.
In an embodiment of both the first and second aspects of the present invention, said fluorocarbon liquid has a pour point as measured according to ISO 3016:1994 of at most -30°C, preferably at most -40°C, more preferably even lower.
At a lower pour point, the fluid will gel with lower temperatures and it will not be able to flow around the electric device.
In an embodiment of both the first and second aspects of the present invention, said fluorocarbon liquid has an acidity as measured according to IEC 62021-1:2003 of at most 0.03 mg KOH/g, preferably even lower.
At a higher acidity, the fluid may corrode either the electrical device or the container with the immersion liquid in which the electrical device is immersed.
The density is preferably below 2000 kg/m3. This parameter is important because it has economic benefits when the product is light weight because less material is needed to support the weight of the fluid.
Thermal expansion, measured according to ASTM D1903 - 08 is at most 12 x 10 3 °C"1. This parameter is important because a high thermal expansion leads to more pressure build up and with it larger air leakage out of the enclosure of which vapor of the liquid as stated above is a part, leading to liquid loss.
The boiling point is preferably more than 80 ° C at atmospheric pressure. This parameter is important because a boiling point that is lower than the expected temperature rise of the liquid will ensure no large quantities of liquid loss.
The specific heat, measured according to ASTM D7896 - 14, is preferably at least 1000 kg'1°C'1. This parameter is important because it determines how much energy can be stored when the liquid has a given maximum temperature.
Thermal conductivity, measured according to ASTM D7896 - 14, is at least 1x1 O'2, preferably at least 5x10'2 W/(m-°C). This parameter is important because the higher the thermal conductivity, the better the cooling.
Maximum Surface load is preferably at least 10, preferably at least 15 W/cm2. This parameter is important because when a load higher than the maximum surface load is applied the liquid may degrade.
In an embodiment of both the first and second aspects of the present invention, said fluorocarbon liquid has an oxidation stability as measured according to IEC 61125:1992 of at most 0.15 % sludge, preferably at most 0.10 % sludge, more preferably at most 0.05 % sludge.
At a lower oxidation stability the fluorocarbon deteriorates, leading to a high propensity to form sludge and sediment.
In an embodiment of both the first and second aspects of the present invention, said fluorocarbon liquid has a sulfur content that is non-corrosive as measured according to IEC 62535:2008; this method uses a copper strip and a piece of paper of which the former is heated. The test results is “non-corrosive” if the copper has any of the following colors: graphite grey, dark brown and black and when the piece of paper does not have any of the following metallic colors: lead, tin, silver, brass, bronze, blue, purple.
In an embodiment of both the first and second aspects of the present invention, said fluorocarbon liquid has a water content of at most 35 ppm, preferably of at most 25 ppm.
At higher water content the stability the fluorocarbon deteriorates, which will cause failure of the electrical device below acceptable levels.
In an embodiment of both the first and second aspects of the present invention, wherein said fluorocarbon liquid is a (per)fluorinated alkane, preferably a (per)fluorinated alkane comprising between 3 to 15 carbon atoms, more preferably between 3 to 12 carbon atoms, even more preferably between 3 to 10 carbon atoms, and one or more combinations thereof.
In an embodiment of both the first and second aspects of the present invention, said fluorocarbon liquid a periluorinated alkoxy-alkane.
In an embodiment of both the first and second aspects of the present invention, said fluorocarbon liquid is a perfluorinated alkoxy-hexane.
In an embodiment of both the first and second aspects of the present invention, said fluorocarbon liquid is a perfluorinated alkoxy-pentane.
In an embodiment of both the first and second aspects of the present invention, said fluorocarbon liquid is 1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-(trifluoromethyl)-pentane. This fluorocarbon liquid is marketed under the tradename Novec 7300 by 3M. This compound exhibits properties which makes it suitable as insulating fluids.
In an embodiment of both the first and second aspects of the present invention, said fluorocarbon liquid is a mixture of one or more (per)fluorinated alkanes.
In an embodiment of both the first and second aspects of the present invention, said fluorocarbon liquid consists of one or more (per)fluorinated alkanes.
In an embodiment of both the first and second aspects of the present invention, said fluorocarbon liquid comprises of one or more (per)fluorinated alkanes, preferably in an amount of at least 80 wt.%, more preferably at least 90 wt.%, the rest being one or more additives.
In an embodiment of both the first and second aspects of the present invention, said fluorocarbon liquid complies with the IEC 60079-6:2015 standards regarding equipment protection by liquid immersion.
In an embodiment of both the first and second aspects of the present invention, said fluorocarbon liquid is transparent.
In an embodiment of both the second aspect of the present invention, said electric device operates at a voltage of not more than 15 kV r.m.s. AC or DC, preferably not more than 11 kV r.m.s. AC or DC, most preferably not more than 1.1 kV r.m.s. AC or 1 kV DC. “No switchgear” as used in the present application means: device that is not designed to make or break the current in one or more electric circuits, according to IEC 60079-6:2015.
In an embodiment said electric device is a no switchgear, being a device that is not designed to make or break the current in one or more electric circuits, according to IEC 60079-6:2015.
In another embodiment, said electric device may be a switchgear, being a gas-insulated switchgear (GIS).
The invention also relates to an electric device immersed in an insulation liquid comprising a fluorocarbon, preferably a (per)fluorinated alkane.
It will be understood by the person skilled in the art that the electric device will be immersed in a container comprising the insulation liquid.
Said container, preferably is made of materials such as steel or a synthetic material where said steel is selected from Stainless steel, aluminium-silicium alloys, more preferably stainless steel 316 or aluminium-silicium-titanium alloy comprising between 91.3 to 93.3 % Al, 6.5 to 7.5 % Si, 0.25 to 0.45 % Mg, 0 to 0.25 % Ti, 0 to 0.19% Fe, 0 to 0.1 % Mn, 0 to 0.1 % residual impurities, 0 to 0.70 % zn and 0 to 0.050 % Cu (being an Al alloy according to EN AC-42000 or EN AC-42100), even more preferably stainless steel 316L or an Al alloy according to EN AC-42000); and wherein said synthetic material is not a silicone or fluoroelastomer.
The minimum liquid level of the insulation liquid in the container is at least at a certain amount higher than the highest, not explosion safe component (all electric components that are not designed for safe use in hazardous arreays according to IEC/EN 60079, NEN 500/505, CEC, UTCR, that is immersed, as stipulated in lECEx 60079-6:2015 clause 4.6 or EN 60079-6:2016. This amount of liquid is called the minimum permissible level. The level is dependent on the highest immersed voltage and is determined according to the information described in Table I.
Table II
The temperature for normal operation inside the container comprising the insulating liquid and the electric device is controlled by having a cooling capacity that is at least as high as the heat production. Heat production is defined as the sum of all power losses (heat dissipation) from the electric device immersed in the insulation liquid. The cooling capacity of the container is the given by the cooling capacity of the container comprising the insulation liquid and liquid treatment system.
Examples
As specified above, the present invention is related to the use a fluorocarbon as a liquid for insulating an electric device which is immersed in said liquid. 1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-(trifluoromethyl)-pentane (F-alkane) was tested by the present inventors and found to comply with all of the requirements of IEC/EN 60079 and was tested with immersion of an electric device. The device worked without any sparks and hence it can be safely used in hazardous environments. The fire point of F-alkane was non existing since it is not flammable; the kinematic viscosity at 25°C was 0.71 cSt; the electrical breakdown voltage was 40 kV; the volume resistivity at 25°C was 1x1013, the pour point was -38 °C; it was sulfur non-corrosive and the water content was < 10 ppm.
The density of F-alkane was 1660 kg/m3; the thermal expansion was 1.3x10-3 °C'1; the boiling point was 98 °C; the specific heat was 1140 kg"1oC'1; the thermal conductivity was 6.3x1 O'2 W/(m-°C); the maximum surface load was 10-18 W/cm2.
The insulating liquids according to the invention has a higher maximum surface load that liquids according to the prior art, which prevents the liquid from degrading when it comes into contact with hotspots. In addition, these fluids have a low viscosity, which facilitates the convection movement of the insulating liquid.
From the Examples it is clear that fluorocarbons are suitable to be used as liquids for insulating an electric device which is immersed in said liquid and hence one or more objects of the present invention are achieved by the use of fluorocarbons liquids which is further elucidated in the appended claims.
Claims (17)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL2017157A NL2017157B1 (en) | 2016-07-12 | 2016-07-12 | Use of a fluorocarbon liquid for insulating electric devices and electric device immersed in an insulation liquid |
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| Application Number | Priority Date | Filing Date | Title |
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| NL2017157A NL2017157B1 (en) | 2016-07-12 | 2016-07-12 | Use of a fluorocarbon liquid for insulating electric devices and electric device immersed in an insulation liquid |
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| NL2017157B1 true NL2017157B1 (en) | 2018-01-17 |
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB661531A (en) * | 1948-11-06 | 1951-11-21 | Westinghouse Electric Int Co | Improvements in or relating to insulation and cooling of electrical apparatus |
| US20150288271A1 (en) * | 2014-04-04 | 2015-10-08 | Raytheon Company | Inertial energy storage system and hydro-fluoro-ether power transformer scheme for radar power systems and large pfn charging |
-
2016
- 2016-07-12 NL NL2017157A patent/NL2017157B1/en active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB661531A (en) * | 1948-11-06 | 1951-11-21 | Westinghouse Electric Int Co | Improvements in or relating to insulation and cooling of electrical apparatus |
| US20150288271A1 (en) * | 2014-04-04 | 2015-10-08 | Raytheon Company | Inertial energy storage system and hydro-fluoro-ether power transformer scheme for radar power systems and large pfn charging |
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