US 20120280189A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2012/0280189 A1 Warren et al. (43) Pub. Date: Nov. 8, 2012

(54) PERFLUOROKETONES AS GASEOUS Related US. Application Data (60) Provisional application No. 61/297,991, ?led on Jan. 25, 2010. (76) Inventors: Karl J. Warren, Hudson, WI (US); _ _ _ _ Phillip E_ Tuma’ Faribault’ MN Publication Classi?cation (US); John G. Owens, Woodbury, (51) Int_ CL MN (US); Richard M- Minday, H01B 3/56 (2006.01) Snllwaten MN (Us) H01F 2 7/20 (2006.01) H01B 7/42 (2006.01) (21) Appl. No.: 13/260,994 C07C 49/00 (2006.01) (52) US. Cl...... 252/571; 568/303; 336/55; 174/156 (22) PCT F1led: Jan. 19, 2011 (57) ABSTRACT (86) PCT NO; PCT/Us2011/021659 A gaseous comprising a per?uoroketone of the formula RfliCOiRfz, Wherein each of Rfl and Rf2 are per § 371 (0X1), ?uoroaliphatic groups, and use thereof in electrical devices, is (2), (4) Date: Sep. 29, 2011 described.

) Patent Application Publication Nov. 8, 2012 Sheet 1 0f 3 US 2012/0280189 A1

20 19 18 ll? 15 \\\

12 \ \ 11 \ \, 10 X 0 20 4O 60 80 100 120 Volume% Gas + SP6, Pt0t=4atm —<>— C6K, Ptot=4atm + SP6, Ptot=6atm —O— C6K, Ptot=6atm Patent Application Publication Nov. 8, 2012 Sheet 2 0f 3 US 2012/0280189 A1

25.0

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0

_ 15.0 > a 0 8 A ‘ 10.0 I ‘ 0 A A I 5.0 - . ‘ A

0.0 0 20000 40000 60000 80000 100000 120000 |Dvap [Pa] u C5 Ketone I C6 Ketone ASF6

fig’. 2 Patent Application Publication Nov. 8, 2012 Sheet 3 0f 3 US 2012/0280189 A1 US 2012/0280189 A1 Nov. 8, 2012

PERFLUOROKETONES AS GASEOUS SUMMARY DIELECTRICS [0007] Brie?y, the present disclosure provides a gaseous dielectric comprising a per?uoroketone of the formula Rfli CROSS REFERENCE TO RELATED COiRf2, wherein each of Rfl and Rf2 are per?uoroaliphatic APPLICATION groups. The gaseous dielectric may be useful in a number of other applications that use dielectric gases. Examples of such [0001] This application claims the bene?t of US. Provi other applications are described in the aforementioned NIST sional PatentApplication No. 61/297,991, ?led Jan. 25, 2010, technical note 1425. The disclosure further provides an elec the disclosure of which is incorporated by reference herein in trical device containing as a component the per?uoroketone its entirety. gaseous dielectric. In some embodiments, the present disclo sure further provides a gaseous dielectric comprising a mix ture of a per?uoroketone and an inert gas, such as nitrogen. FIELD OF THE INVENTION [0008] The use of a per?uoroketone as a gaseous dielectric advantageously has a broad range of operating temperatures [0002] This invention relates to per?uoroketones and the and pressures, is thermally, and chemically stable, has a use thereof as gaseous dielectric ?uids in electrical devices higher and heat transfer ef?ciency than SF6 such as , switchgear, and electric at a given partial pressure, and has and a lower global warm cables or buses. ing potential (GWP) than SF6. The instant per?uoroketones generally have a dielectric strength greater than 6 kV at a BACKGROUND pressure of 20 kPa at the operating temperature of the elec trical device. [0003] Dielectric gases are used in various electrical appa ratus; see for example US. 2008/0135817 (Luly et al.). Major BRIEF DESCRIPTION OF THE FIGURES types of such apparatus are transformers, electric cables or [0009] FIG. 1 is a graph of the heat transfer performance of buses, and circuit breakers or switchgear. In such electrical the gaseous per?uoroketone/nitro gen dielectrics as compared devices, dielectric gases are often used in place of air due to to SF6, and SF6 mixtures with N2, at the indicated pressures. their high dielectric constant (K) and high dielectric strength [0010] FIG. 2 is a graph of the dielectric strength perfor (DS). Such dielectric gases allow higher power densities as mance of the gaseous per?uoroketone dielectrics as com compared to air-?lled electrical devices. pared to SF6. [0004] Most signi?cantly sulfur hexa?uoride (SF6) has [0011] FIG. 3 is an illustration of electrical hardware using become the dominant captive in many electrical a per?uoroketone gaseous dielectric. applications. SF6 is advantageously nontoxic, non-?am [0012] As used herein, “GWP” is a relative measure of the mable, easy to handle, has a useful operating temperature warming potential of a compound based on the structure of range, and excellent dielectric and arc-interrupting proper the compound. The GWP of a compound, as de?ned by the ties. Within transformers, it also acts as a . Blowers Intergovernmental Panel on Climate Change (IPCC) in 1990 within the circulate the gas aiding in heat transfer and updated in 2007, is calculated as the warming due to the from the windings. release of 1 kilogram of a compound relative to the warming [0005] However, the greatest concern with SF6 is its 3200 due to the release of 1 kilogram of CO2 over a speci?ed year atmospheric lifetime and very signi?cant global warm integration time horiZon (ITH). ing potential (GWP) of about 22,200 times the global warm ing potential of carbon dioxide. At the December 1997 Kyoto Summit in Japan, representatives from 160 countries drafted ITH ITH f a; [cm] m f a; cot-H" m an agreement containing limits for greenhouse gas emissions. 0 0 The agreement covers six gases, including SF6, and includes IOITH “C02 [CC02 (1)] d1 folTHacoz [Cc02 (1)] d1 a commitment to lower the total emissions of these gases by the year 2010 to levels 5.2% below their total emissions in 1990. See UNEP (United Nations Environment Programme), [0013] In this equation (xi is the radiative forcing per unit Kyoto Protocol to the United Nations Framework Convention mass increase of a compound in the atmosphere (the change on Climate Change, Nairobi, Kenya, 1997. in the ?ux of radiation through the atmosphere due to the IR [0006] The National Institute of Standards and Technology absorbance of that compound), C is the atmospheric concen (NIST) have published Technical Note 1425: “Gases for elec tration of a compound, '5 is the atmospheric lifetime of a trical Insulation and Arc Interruption: Possible Present and compound, t is time and i is the compound of interest. Future Alternatives to Pure SF6”, which identi?es, as possible [0014] The commonly accepted ITH is 100 years represent replacements, mixtures of SF6 with either nitrogen or helium, ing a compromise between short-term effects (20 years) and or high-pressure nitrogen. Some other replacement mixtures longer-term effects (500 years or longer). The concentration suffer from release of free carbon during arcing, increased of an organic compound, i, in the atmosphere is assumed to toxicity during or after arcing, and increased dif?culty in gas follow pseudo ?rst order kinetics (i.e., exponential decay). handling due to substantially different pressures required dur The concentration of CO2 over that same time interval incor ing liqui?cation of the components. Also identi?ed are per porates a more complex model for the exchange and removal ?uorocarbon (PFC) gases that might also be mixed with nitro of CO2 from the atmosphere (the Bern carbon cycle model). gen or helium, like SF6. Yet PFCs also have high GWPs so the [0015] Carbonyl compounds such as aldehydes and possible reduction in environmental impact of such strategies ketones have been shown to have measurable photolysis rates is limited. in the lower atmosphere resulting in very short atmospheric US 2012/0280189 A1 Nov. 8, 2012

lifetimes. Compounds such as formaldehyde, acetaldehyde, [0021] “Per?uoroaliphatic” is inclusive of per?uoroalkyl propionaldehyde, isobutyraldehyde, n-butyraldehyde, and per?uorooxyalkyl (and nitrogen and sulfur analogs acetone, 2-butanone, 2-pentanone and 3-pentanone have thereof) Wherein all hydrogen atoms of the oxyalkyl radical atmospheric lifetimes by photolysis ranging from 4 hours to are replaced by ?uorine atoms and the number of carbon 38 days (Martinez, R. D., et al., 1992, Atmospheric Environ atoms is from 2 to 5, eg CF3CF2OCF2CF2i, ment, 26, 785-792, and Seinfeld, J. H. and Pandis, S. N., CF3CF2SF4CF2i or CF3CF2N(CF3)CF2i. Atmospheric Chemistry and Physics, John Wiley & Sons, [0022] “Per?uoroalkyl” has essentially the meaning as NeWYork, p. 288, 1998). CF3CF2C(O)CF(CF3)2 has an atmo “alkyl” Wherein all of the hydrogen atoms of the alkyl radical spheric lifetime of approximately one Week based on pho are replaced by ?uorine atoms and the number of carbon tolysis studies With natural sunlight (D’Anna, B., Sellevag, S. atoms is from 1 to about 5, eg per?uoropropyl, per?uoroiso R., WirtZ, K., Nielsen, C. 1., Environ. Sci. Technol, 39, 8708, propyl per?uorobutyl, per?uoromethyl, and the like. 2005), and photolysis studies at 300 nm are described by [0023] Per?uorinated ketones (PFKs) useful in the present Taniguchi, N., et al. J. Phys. Chem. A, 107(15), 2674-79, invention include ketones Which are fully ?uorinated, i.e., all 2003. Other per?uoroketones shoW similar absorbances near of the hydrogen atoms in the carbon backbone have been 300 nm and are expected to have similar atmospheric life replaced With ?uorine atoms. The carbon backbone can be times. linear, branched, or cyclic, or combinations thereof, and Will [0016] The very short lifetimes of the per?uoroketones lead preferably have about 4 to about 7 carbon atoms. Represen to very loW GWPs. A measured IR cross-section Was used to tative examples of per?uorinated ketone compounds suitable calculate the radiative forcing value for CF3CF2C(O)CF for use in the processes and compositions of the invention (C133)2 using the method of Pinnock, et al. (J. Geophys. Res., 100, 23227, 1995). Using this radiative forcing value and the include CF3CF2C(O)CF(CF3)2, CF3C(O)C2F5, CF3C(O) one Week atmospheric lifetime the GWP (100 year ITH) for (CF2)2CF3, CF3CF2C(O)CF2CF2CF3, (CF3)2CFC(O)CF CF3CF2C(O)CF(CF3)2 is 1. The per?uoroketones of the dis (CF92, CF3(CF2)2C(O)CF(CF3)2, CF3(CF2)4C(0)CF3, CF3 closure typically have a GWP less than about 100, and pref (CF2)3C(O)CF3, CF3CF2C(O)CF2CF3, CF3C(O)CF(CF3)2, erably less than 10. per?uorocyclopentanone, per?uorocyclohexanone, and mix tures thereof. [0017] As a result of their rapid degradation in the loWer atmosphere, the per?uoroketones have short lifetimes and [0024] The per?uoroketones can also contain one or more Would not be expected to contribute signi?cantly to global caternary (i.e. in-chain) heteroatoms interrupting the carbon Warming. The loW GWP of the per?uoroketones, in addition backbone. Suitable heteroatoms include, for example, nitro to the dielectric performance characteristics, make them Well gen, oxygen, and sulfur atoms. Representative examples of suited for use as a gaseous dielectric. such ?uorinated ketones include CF3OCF2CF2C(O)CF [0018] Advantageously, the gaseous dielectric of the (C133)2 and CF3OCF2C(O)CF(CF3)2. present disclosure has a high electrical strength, also [0025] In addition to demonstrating dielectric gas perfor described as high breakdown voltage. “Breakdown voltage,” mance, per?uorinated ketones can offer additional important as used in this application means (at a speci?c frequency) the bene?ts in safety of use and in environmental properties. For highest voltage applied to a liquid that induces catastrophic example, CF3CF2C(O)CF(CF3)2 has loW acute toxicity, failure of the gaseous dielectric alloWing electrical current to based on short-term inhalation tests With mice exposed for conduct through the gas. Thus the gaseous dielectric of the four hours at a concentration of 100,000 ppm in air. Also present invention can function under high voltages. The gas based on photolysis studies at 300 nm CF3CF2C(O)CF(CF3)2 eous dielectric can also exhibit a loW loss factor, that is, the has an estimated atmospheric lifetime of one Week. Other amount of electrical energy that is lost as heat from an elec per?uorinated ketones shoW similar absorbances and thus are trical device such as a . expected to have similar atmospheric lifetimes. As a result of [0019] Per?uoroketones (PFKs) that are useful in the their rapid degradation in the loWer atmosphere, the per?u present invention include those ketones having only ?uorine orinated ketones have short atmospheric lifetimes and Would attached to the carbon backbone. More speci?cally, the not be expected to contribute signi?cantly to global Warming instant per?uoroketones are of the formula Rfl4COiRf2, (i.e., loW global Warming potentials) and thereby reduce Wherein each of Rfl and Rf2 are per?uoroaliphatic groups, greenhouse gas emissions When replacing SP6. preferably per?uoroalkyl groups. The per?uoroketones con [0026] Per?uorinated ketones Which are straight chain or tain 4 to 7 carbon atoms. cyclic can be prepared as described inU.S. Pat. No. 5,466,877 [0020] More speci?cally, Rfl and Rf2 are each monovalent (Moore et al.) Which in turn can be derived from the ?uori per?uoroaliphatic groups having 1 to 5 per?uorinated carbon nated esters described in US. Pat. No. 5,399,718 (Costello et atoms, optionally containing one or more catenary (in-chain) heteroatoms, such as divalent oxygen, hexavalent sulfur, or al.). trivalent nitrogen bonded only to carbon atoms, such heteroa [0027] Per?uorinated ketones that are alpha-branched to toms being a chemically stable link betWeen per?uorocarbon the carbonyl group can be prepared as described in US. Pat. portions of the per?uoroaliphatic group and do not interfere No. 3,185,734 (FaWcett et al.). Hexa?uoropropylene is added With the inert character of the per?uoroaliphatic group. In to acyl halides in an anhydrous environment in the presence of preferred embodiments, R l and Rf2 are per?uoroalkyl ?uoride ion. Small amounts of hexa?uoropropylene dimer groups. The skeletal chain of Rfl and Rf2 can be straight chain, and/or trimer impurities can be removed by distillation from branched chain, and if su?iciently large, cyclic, or combina the per?uoroketone. If the boiling points are too close for tions thereof, such as per?uoroalkylcycloaliphatic groups. In fractional distillation, the dimer and/ or trimer impurity can be some embodiments at least one of Rfl and Rf2 is a branched removed by oxidation With alkali metal permanganate in a per?uoraliphatic group. suitable organic solvent such as acetone, acetic acid, or a US 2012/0280189 A1 Nov. 8, 2012

mixture thereof. The oxidation reaction is typically carried substations contain one or all of these devices often in ?uid out in a sealed reactor at ambient or elevated temperatures. In communication With each other. Such gas-insulated equip some embodiments, per?uoroketones in Which at least one of ment is a major component of poWer transmission and distri Rfl or Rf2 are secondary per?uoroalkyl groups are preferred. bution systems all over the World. [0028] Linear per?uorinated ketones can be prepared by [0034] In some embodiments, the present disclosure pro reacting a per?uorocarboxylic acid alkali metal salt With a vides electrical devices, such as capacitors, comprising metal per?uorocarbonyl acid ?uoride as described in Us. Pat. No. electrodes spaced from each other such that the gaseous 4,136,121 (Martini et al.) Such ketones can also be prepared dielectric ?lls the space betWeen the electrodes. The interior by reacting a per?uorocarboxylic acid salt With a per?uori space of the electrical device may also comprise a reservoir of nated acid anhydride in an aprotic solvent at elevated tem the liquid per?uoroketone Which is in equilibrium With the peratures as described in Us. Pat. No. 5,998,671 (Van Der gaseous per?uoroketone. Thus the reservoir may replenish Puy). All of the aforementioned patents are incorporated by reference in their entirety. any losses of the gaseous per?uoroketone. [0029] The useful per?uoroketones have a gaseous range [0035] For circuit breakers the excellent thermal conduc that encompasses the operating temperature range of the elec tivity and high dielectric strength of such gases, along With trical device in Which they are used as components of the the fast thermal and dielectric recovery (short time constant gaseous dielectric of this invention, preferably such that the for increase in resistivity), are the main reasons for its high per?uoroketones have a boiling point less than 50° C., more interruption capability. These properties enable the gas to preferably beloW 30° C. and containing 4 to 7 carbon atoms. make a rapid transition betWeen the conducting (arc plasma) C3 per?uoroketone, i.e. hexa?uoroacetone, may be excluded and the dielectric state of the arc, and to Withstand the rise of due to the knoWn toxicityihaving a Threshold Limit Value the recovery voltage. of 0.1 ppm. Higher, i.e. greater than C7, per?uoroketones may [0036] For gas-insulated transformers the heat transfer per be excluded due to the loW vapor pressure. formance, and compatibility With current devices, in addition [0030] In most embodiments, useful per?uoroketones have to the dielectric characteristics, make them a desirable a vapor pressure of 30 kPa at 25° C. Preferably, useful per medium for use in this type of electrical equipment. The ?uoroketones have a vapor pressure of at least 30 kPa, more instant per?uoroketones have distinct advantages over oil preferably at least 40 kPa, at the operating temperature of the electrical device. Generally, useful per?uoroketone gaseous insulation, including none of the ?re safety problems or envi dielectrics having a boiling point in the range of —20 to 50° C., ronmental compatibility, high reliability, little maintenance, preferably —20 to 30° C. For example, many electrical devices long service life, loW toxicity, ease of handling, and reduced such as capacitors, transformers, circuit breakers and gas equipment Weight. insulated transmission lines may operate at temperatures of at [0037] For gas-insulated transmission lines the dielectric least 30° C. and above. At these operating temperatures, the strength of the gaseous per?uoroketones under industrial gaseous dielectric should have a vapor pressure of at least 40 conditions is signi?cant, especially the behavior of the gas kPa. eous dielectric under metallic particle contamination, sWitch [0031] Further, the per?uoroketones have a dielectric ing and lightning impulses, and fast transient electrical strength of at least 5 kV at the operating pressure in the stresses. These gaseous per?uoroketones also have a high electric device, Which is typically at least 20 kPa. Preferably ef?ciency for transfer of heat from the conductor to the enclo per?uoroketones have a dielectric strength of at least 10 kV sure and are stable for long periods of time (e.g., 40 years). and more preferably at least 15 kV at the operating tempera These gas-insulated transmission lines offer distinct advan ture and pressure of the device. tages: cost effectiveness, high-carrying capacity, loW losses, [0032] In some embodiments, the per?uoroketone may be availability at all voltage ratings, no ?re risk, reliability, and a combined With other conventional gaseous dielectrics, such compact alternative to overhead transmission as an inert gas. These conventional dielectric gases have a lines in congested areas that avoids public concerns With boiling points beloW 0° C., have a Zero oZone depletion poten overhead transmission lines. tial, a global Warming potential beloW that of SP6 (about 22,000), are chemically and thermally stable, and have a [0038] For gas-insulated substations, the entire substation dielectric constant greater than air. The conventional gaseous (circuit breakers, disconnects, grounding sWitches, busbar, dielectrics include nitrogen, helium, argon, and carbon diox transformers, etc., are interconnected) is insulated With the ide. Generally, the second gaseous dielectric is used in gaseous dielectric medium of the present disclosure, and, amounts such that vapor pressure is at least 70 kPa at 25° C., thus, all of the above-mentioned properties of the dielectric or at the operating temperature of the electrical device. In gas are signi?cant. some embodiments the ratio of the vapor pressure of the [0039] In some embodiments the gaseous dielectric may be second gaseous dielectric to the per?uoroketone dielectric is present in an electric device as a gas per se, or as a gas in at least 2.5: 1, preferably at least 5:1, and more preferably at equilibrium With the liquid. In these embodiments the liquid least 10:1. phase serves as a reservoir for additional gaseous dielectric. [0033] The per?uoroketones are useful in gaseous phase [0040] The use of per?uoroketones as gaseous dielectrics is for electrical insulation and for arc quenching and current illustrated in the generic electrical device of FIG. 3. The interruption equipment used in the transmission and distribu Figure illustrates device comprising a tank or pressure vessel tion of electrical energy. Generally, there are three major 2, containing electrical hardware 3, such as a sWitch, inter types of electrical devices in Which the gases of the present rupter or the Windings of a transformer, and at least one disclosure can be used: (1) gas-insulated circuit breakers and gaseous per?uoroketone 4. Optionally the gaseous per?uo current-interruption equipment, (2) gas-insulated transmis roketone 4 is in equilibrium With a reservoir of a liquid per sion lines, and (3) gas-insulated transformers. Gas-insulated ?uoroketone 5. US 2012/0280189 A1 Nov. 8, 2012

[0041] Objects and advantages of this invention are further For compositions below 100% SP6, N2 is then added to obtain illustrated by the following examples, but the particular mate PM. The composition can then be calculated as Vol %:Pgas/ rials and amounts thereof recited in these examples, as well as tot‘ other conditions and details, should not be construed to [0045] For C6K, it is not possible for Pgas to exceed the unduly limit this invention. C6K saturation pressure, PM, at Ta. Pgas will equal PSMIEXP (—3627.0355/Ta+22.7598) if excess liquid is present. There EXAMPLES fore, the gas was added as a liquid beyond the level that would saturate the vessel volume at the maximum temperature to be Materials studied. N2 was added to obtain the desired PM. Power is then applied to the heater and fan. Data are recorded when the [0042] system has equilibrated. For these experiments water tem peratures were 14.9, 30.9, and 43 .40 C. at Pt0t:4 atm and 15 .7, 31.0 and 42.6, at Pt0t:6 atm. [0046] Superior heat transfer performance is indicated by a Compound Structure Name Source lower temperature difference between the jacket water tem perature, TW, and the heater temperature, T h, at a given PM and, in the case of the C6K, TW. The data in FIG. 1 show that at even at moderate gas temperatures, C6K-saturated N2 pro duced superior heat transfer performance as compared to pure St. Paul, MN SP6. Dielectric Strength (DS) Measurement Concorde Gas, Eatontown, NJ [0047] The dielectric strength of SP6, CSK and C6K were measured experimentally using a dielectric Hipotronics OC90D dielectric strength tester (available from Hipotronics, Preparation 1: 1,1,1,3,4,4,4-Hepta?uoro-3 -tri?uo Brewster, N.Y.) modi?ed to allow low pressure gases. The romethyl-butan-2-one CF3C(O)CF(CF3)2 electrode and test con?guration comply with ASTM D877. The test chamber was ?rst evacuated and the baseline dielec [0043] Tri?uoroacetic anhydride (2310 g 11.0 mol, Alfa tric strength was measured. Known quantities of SP6, C6K or Aesar, Ward Hill, Mass.), potassium ?uoride (703 g 12.1 mol, CSK were then injected to achieve the measured pressure, Aldrich, Milwaukee, Wis.), hexa?uoropropene (1650 g 11.0 Pvap. The dielectric strength (DS) was recorded after each mol, MDA Manufacturing, Decatur, Ala.) and diglyme sol injection. The results are shown in FIG. 2. vent (2000 g) were combined in a 2-gallon Parr high pressure reactor. The reactor was then heated slowly to 75° C. The 1. An electrical device containing as a component a C4 to pressure increased to 350 psi. As the hexa?uoropropene C7 per?uoroketone gaseous dielectric, wherein the per?uo reacted with the anhydride to form the ketone, the pressure roketone has a vapor pressure of at least 30 kPa at the oper gradually dropped below 50 psi. Additional hexa?uoropro ating temperature of the device. pene was added at this point (528 g) to maximize conversion. 2. The electrical device of claim 1 comprising a per?uo The reaction mix was stirred for 24 hours. The crude reaction roketone of the formula Rfl4COiRf2, wherein each of Rfl product was emptied to a round bottom ?ask where the ketone and Rf2 are per?uoroaliphatic groups. product was vacuum distilled away from the salts and dig 3. The electrical device of claim 1 wherein the per?uoroke lyme solvent. The ketone was then puri?ed by fractional tone is a C4 to C6 per?uoroketone. distillation from concentrated sulfuric acid (used for drying). 4. The electrical device of claim 1 wherein said per?uo An Oldershaw (20-tray) column was used for the distillation. roketone is selected from the group consisting of CF3CF2C The total amount of ketone recovered was 1690 g. Product (O)CF(CF3)2, CF3C(O)C2F5, CF3C(O)(CF2)2CF3, CF3CF2C purity was measured by 1H, 19P NMR and determined to be (O)CF2CF2CF3, (CF3)2CFC(O)CF(CF3)2, CF3(CF2)2C(O) 99.6%. CF(CF3)2, CF3(CF2)4C(O)CF3, CF3(CF2)3C<0)CF3, CF3CF2C(O)CF2CF3, CF3C(O)CF(CF3)2, per?uorocyclo Heat Transfer Measurements pentanone, per?uorocyclohexanone, and mixtures thereof. 5. The electrical device of claim 1 wherein said per?uo [0044] The relative heat transfer capabilities of SP6, SF6/N2 mixtures and C6K-saturated N2 were measured experimen roketone is selected from CF3CF2C(O)CF(CF3)2 and CF3C tally using the following apparatus. The apparatus comprised (O)CF(CF3)2. a 1 liter jacketed pressure vessel. The pressure vessel con 6. The electrical device of claim 1 wherein one of Rfl and tained an electric resistance heater and a DC fan, and a valved Rf2 of the gaseous dielectric is a secondary per?uoroalkyl. pressure inlet for introduction of gases and purging of the 7. The gaseous dielectric of claim 1 having a vapor pressure chamber. Water of a controlled temperature, TW, is passed ofat least 30 kPa at 250 C. through the jacket. Thermocouples are used to monitor the 8. The gaseous dielectric of claim 1 having a dielectric heater temperature, Th, the water temperature and the tem strength of at least 5 kV at 25 kPa. peratures of the gas in the vessel, Ta. The vessel was ?rst 9. The electrical device of claim 1 wherein the gaseous evacuated. The gas under study is then added. In the case of dielectric has a global warming potential of less than 100. SF6 and SF6/N2 measurements, the composition of the gas is 10. The electrical device of claim 1 wherein the gaseous controlled by ?rst adding SF6 until a particular pressure is dielectric further comprises a reservoir of liquid dielectric obtained, P For 100% SF6 this is the total pressure, PM. per?uoroketone. US 2012/0280189 A1 Nov. 8, 2012

11. The electrical device of claim 1 Wherein the gaseous 16. The electrical device of claim 15 Wherein the second dielectric has a dielectric strength (DS) of 6 kV of more. dielectric gas is selected from nitrogen, helium, argon, and 12. The electrical device of claim 1 Wherein the gaseous carbon dioxide. dielectric has a global Warming potential of less than 10. 17. A gaseous dielectric composition comprising a C4 to C7 13. The electrical device of claim 1 Wherein at least one of per?uoroketone gaseous dielectric, and a second gaseous dielectric comprising an inert gas having a vapor pressure is at Rfl or Rf2 is (CF3)2CFi. least 70 kPa. 14. The electrical device of claim 1, Wherein said electrical 18. The gaseous dielectric composition of claim 17 device is selected from the group consisting of: gas-insulated Wherein the ratio of the vapor pressure of the second gaseous circuit breakers and current-interruption equipment, gas-in dielectric to the per?uoroketone dielectric is at least 2.511. sulated transmission lines, gas-insulated transformers, and 19. The gaseous dielectric composition of claim 17 gas-insulated substations. Wherein the inert gas is selected from nitrogen, helium, argon, 15. The electrical device of claim 1 further comprising a and carbon dioxide. second dielectric gas having a vapor pressure of at least 70 kPa.