WO2016146197A1

WO2016146197A1 - Dielectric insulation or arc-extinction fluid

Info

Publication number: WO2016146197A1
Application number: PCT/EP2015/055828
Authority: WO
Inventors: Charles DOIRON; Nitesh Ranjan; Branimir Radisavljevic; Thomas Alfred Paul; Anna Di Gianni; Philipp Simka
Original assignee: Abb Technology Ag
Priority date: 2015-03-19
Filing date: 2015-03-19
Publication date: 2016-09-22

Abstract

The present invention relates to a dielectric insulation or arc-extinction fluid comprising or essentially consisting of: a) a fluorinated organic compound FOC1 as a first fluid component A in mixture with b) a second fluid component B different from the said first fluid component A. According to the invention, said first fluid component A is a hydrochlorofluoroolefin.

Description

Dielectric insulation or arc-extinction fluid

The present invention relates to a dielectric insulation or arc-extinction fluid and to the use of a fluid mixture comprising or essentially consisting of a defined first and second fluid component as a dielectric insulation fluid or arc-extinction fluid. The present invention further relates to the use of the dielectric insulation or arc-extinction fluid in an apparatus for the generation, transmission, distribution and/or usage of electrical energy as well as to an apparatus containing the dielectric insulation fluid.

Dielectric insulation media in gaseous or liquid state are conventionally applied for the insulation of an electrically conductive part in a wide variety of apparatuses, such as for example switchgears, gas-insulated substations (GIS) , gas- insulated lines (GIL), transformers, or others.

In medium- or high-voltage metal-encapsulated switchgears, for example, the electrically conductive part is arranged in a gas-tight housing, which defines an insulating space, said insulation space comprising an insulation gas and separating the housing from the electrically conductive part without letting electrical current to pass through the insulation space. For interrupting the current in e.g. high-voltage switchgear, the insulating gas further functions as an arc- extinction gas. Sulphur hexafluoride (SF₆) is a well-established insulation gas due to its outstanding dielectric properties and its chemical inertness. Despite these properties, efforts to look for an alternative insulation gas have nevertheless been intensified, in particular in view of a lower Global Warming Potential (GWP) than the one of SF₆. Recently, the use of organofluorine compounds in dielectric insulation media has been suggested.

Specifically, WO-A-2010/142346 discloses a dielectric insulation medium comprising a fluoroketone containing from 4 to 12 carbon atoms. Fluoroketones have been shown to have a high dielectric strength. At the same time, they have a very low Global Warming Potential (GWP) and very low toxicity. The combination of these characteristics renders these fluoroketones highly suitable as a possible alternative to conventional insulation gases.

Despite the high dielectric strength of the fluoroketones disclosed in WO-A-2010/142346, the insulation performance of the respective insulation medium is often limited due to the relatively low vapour pressure of the fluoroketone. This is particularly the case for applications in a low temperature environment. In these applications, only a relatively low saturated vapour pressure of the fluoroketone can be maintained without it becoming liquefied.

In consideration of these shortcomings, WO-A-2012/080246 suggests a dielectric insulation gas comprising a fluoroketone containing exactly 5 carbon atoms, in particular 1,1,1,3,4,4, 4-heptafluoro-3- (trifluoromethyl) -butan-2-one (hereinafter referred to as "C5K") , in a mixture with a carrier gas, in particular air or an air component, which together with the fluoroketone provides a non-linear increase of the dielectric strength of the insulation medium over the sum of dielectric strengths of the gas components of the insulation medium.

Notstrengthing the excellent properties of the insulation medium according to WO-A-2012/080246, there is an ongoing need to further reduce any health risk that might arise by using an alternative "non-SF₆" insulation medium. The problem to be solved by the present invention is thus to provide an environmentally friendly dielectric insulation or arc-extinction medium showing comparable dielectric performance as other alternative insulation media, and which at the same time exhibits an even lower toxicity than such insulation media.

The problem is solved by the subject matter of claim 1. Preferred embodiments of the invention are defined in the dependent claims and claim combinations, and in the description and figures.

According to claim 1, the dielectric insulation or arc- extinction fluid of the present invention comprises or essentially consists of:

a) a fluorinated organic compound FOCI as a first fluid component A in mixture with

b) a second fluid component B different from the said first fluid component A,

wherein the first fluid component A is a hydrochlorofluoro- olefin . It has surprisingly been found that by the use of a hydro^¬ chlorofluoroolefin, an environmentally friendly insulation medium with a very low GWP can be achieved, l-chloro-3, 3, 3- trifluoropropene, for example, has an atmospheric lifetime between 26 and 40 days and exhibits a GWP of about 6 to 7 and an ODP of about 0. This finding is contrary to the established doctrine that compounds containing chlorine generally have a high ODP and are thus generally not considered when looking for an alternative "non-SF₆" insulation medium. Such low GWP compares very favourably with fluoronitriles , in particular with 2, 3, 3, 3-tetrafluoro-2- (trifluoromethyl) -2-propanenitrile (C4F7N) , which has a GWP of 2210. In embodiments, the hydrochlorofluoroolefin (in the following also referred to as HCFO) is selected to have a boiling point of less than 40°C. In the context of the present invention, the boiling point refers to the standard boiling point, i.e. the temperature at which boiling occurs under a pressure of 1 bar .

In embodiments, the hydrochlorofluoroolefin (HCFO) contains from 2 to 5 carbon atoms, more preferably from 3 to 4 carbon atoms, and most preferably contains exactly 3 carbon atoms. Depending on the number of carbon atoms, the chain of the HCFO can be linear or branched.

In embodiments, the hydrochlorofluoroolefin (HCFO) is 1- chloro-3 , 3 , 3-trifluoropropene (in the following also referred to as HCFO-1233zd) , in particular the trans-isomer of 1- chloro-3 , 3 , 3-trifluoropropene (in the following also referred to as HCFO-1233zd (E) ) , as will be explained in further detail below. HCFO-1233zd has a boiling point of 19°C.

The HCFO used in the dielectric insulation or arc-extinction fluid of the present invention, and HCFO-1233zd in particular, exhibits a relatively high pressure-reduced dielectric strength. For example, the breakdown voltage at 500 mbar of HCFO-1233zd was found to be about 150 kV/cm/bar in uniform field conditions, as will be shown in more detail below, which is higher than the dielectric strength of e.g. 1 , 3 , 3 , 3-tetrafluoropropene (HFO-1234ze) , which solely differs from HCFO-1233zd in being fluorinated in position 1 rather than being chlorinated.

As will also be shown in more detail below, the vapour pressure of HCFO-1233zd is higher than the one of C5K at least over the temperature range from 250 K and 300 K, i.e. the whole temperature range of interest encompassing any minimal operating temperature range of any electrical apparatus of relevance. Owing to the higher vapour pressure of HCFO-1233zd compared to C5K, its maximum dielectric strength reachable for a given dew point is higher than the one of C5K: although the pressure-reduced dielectric strength of HCFO-1233zd is slightly lower than the one of C5K, this is in practice more than compensated due to the higher partial pressure achievable for HCFO-1233zd, ultimately allowing for an increased dielectric performance throughout the relevant temperature range of the electrical apparatus. In order to achieve the dielectric performance required in e.g. medium-voltage or high-voltage metal-encapsulated switchgears, the insulation medium comprises apart from the first fluid component A a second fluid component B different from the said first fluid component A. Typically, this second fluid component B is a carrier gas, by means of which a relatively high operating pressure in the range of several bars can be achieved, as will be explained in further detail below. Ultimately, a very high dielectric performance can thus be achieved by the dielectric insulation or arc- extinction medium of the present invention.

The toxicity of the hydrochlorofluoroolefin, in particular HCFO-1233zd, more particularly HCFO-1233zd (E) , is markedly lower than e.g. of fluoronitriles , in particular of C4F7N. In addition, an even lower toxicity than the already low toxicity of C5K can be achieved by the present invention. Specifically, the toxicity of HCFO-1233zd is extremely low. In more concrete terms, its LC50 (lethal concentration over 4 hours with rats) is about 120' 000 ppm, which compares favourably with the already very low toxicity of fluoroketones such as dodecafluoro-2-methylpentan-3-one, which is in commercial use under the trade name "Novec".

Apart from its extremely low toxicity, the HCFO of the present invention, in particular HCFO-1233zd, exhibits no flame propagation at all. Its safety rating according to the ASHRAE Std. 34 Safety Classification is "Al", i.e. is of higher safety than e.g. the safety rating of 1,3,3,3- tetrafluoropropene (HFO-1234ze) , which is classified as "A2L" and which solely differs from HCFO-1233zd in being fluorinated in position 1 rather than being chlorinated.

The insulation medium or arc-extinction medium of the present invention comprising a hydrochlorofluoroolefin is further favourable in view of a high compatibility with other materials, such as sealings, solid insulators and the like, contained in the electrical apparatus in which it is to be used. Without wanting to be bound by the theory, it is assumed that this high material compatibility is due to the relatively low reactivity of the double bond being the only reactive moiety of the molecule. The potential reactivity of the double bond is further lowered by the presence of the electrophilic substituents CF₃ and CI, which further decrease the nucleophilic properties of the compound.

In preferred embodiments, the first fluid component A is chosen to be l-chloro-3, 3, 3-trifluoropropene (HCFO-1233zd) , in particular because of its low toxicity, environmental friendliness and high dielectric strength achievable, in particular in gas mixtures. In particularly preferred embodiments, the trans-isomer of l-chloro-3, 3, 3-trifluoro- propene (HCFO-1233zd (E) ) is chosen.

In embodiments, the second fluid component B comprises or consists of a carrier gas, specifically a carrier gas having a boiling point of -60°C at most, thus allowing a far higher operating pressure and, therefore, a higher dielectric strength to be achieved than when using the hydrochloro- fluoroolefin alone. Typically, the carrier gas itself has a lower dielectric strength than the first fluid component A.

According to particularly preferred embodiments, the second fluid component B comprises or consists of a carrier gas selected from the group consisting of oxygen (0₂) , nitrogen (N₂) , carbon dioxide (C0₂) , nitrous oxide (N₂0) , and mixtures thereof. Ultimately, a dielectric strength high enough for the targeted applications, in particular for medium-voltage or high-voltage metal-encapsulated switchgears, can thus be achieved.

Alternatively or additionally, the carrier gas can also comprise a noble gas, nitric oxide (NO) and/or nitrogen dioxide (N0₂) .

In further preferred embodiments, the second fluid component B comprises or consists of carbon dioxide (C0₂) . This is in particular the case when the present invention relates to an arc-extinction fluid, as C0₂ has been found to have optimum carrier gas properties for this application.

According to specific embodiments, the second fluid component B comprises or consists of oxygen (0₂) , since by the presence of oxygen the formation of harmful decomposition products can be reduced efficiently or can even be eliminated, in particu^¬ lar owed to the ability of oxygen for radical quenching.

In embodiments when a carrier gas comprising carbon dioxide is used, the carrier gas preferably further comprises oxygen, since by the presence of oxygen any soot formation which might otherwise occur during switching can be efficiently reduced or even eliminated.

Thus, according to particularly preferred embodiments, the second fluid component B comprises or consists of a mixture of carbon dioxide and oxygen, thereby allowing a combination of the above mentioned desired effects of a good carrier gas performance with reduced formation of soot and harmful decomposition products. In this regard, it is further preferred that the ratio of the amount of carbon dioxide to the amount of oxygen ranges from 50:50 to 100:1, preferably from 80:20 to 95:5, more preferably from 85:15 to 92:8, even more preferably from 87:13 to less than 90:10, and in particular is about 89:11.

In further embodiments, the dielectric insulation or arc- extinction fluid comprises as the second fluid component B or as a third fluid component C a further fluorinated organic compound FOC2 different from the hydrochlorofluoroolefin (i.e. FOCI) of the first fluid component A. By the presence of both a hydrochlorofluoroolefin and a further fluorinated organic compound FOC2, in particular a fluoroketone, a highly synergistic effect can be achieved, as will be explained in more detail by way of the examples below. In other words, a dielectric performance can be achieved, which is beyond the dielectric performance achievable when using either the hydrochlorofluoroolefin or the fluoroketone in pure form. This synergistic effect between hydrochlorofluoroolefin and the fluoroketone, in particular between trans-isomer of 1- chloro-3 , 3 , 3-trifluoropropene and C5K, is expected to be present also when a background or carrier gas is mixed in. As explained above, the dielectric insulation or arc- extinction fluid of the present invention typically contains a carrier gas as fluid component B. Consequently, if a further fluorinated organic compound FOC2 is contained, the dielectric insulation or arc-extinction fluid preferably comprises or essentially consists of

a) a hydrochlorofluoroolefin (FOCI) as first fluid component A in mixture with

β) a carrier gas as second fluid component B, and γ) a further fluorinated organic compound (FOC2) different from the hydrochlorofluoroolefin (FOCI) of the first fluid component A.

Specifically, the further fluorinated organic compound FOC2 is an organofluorine compound devoid of chlorine atoms, in contrast to the hydrochlorofluoroolefin contained as first fluid component A.

More specifically, the further fluorinated organic compound FOC2 is at least one compound selected from the group consisting of: fluoroethers (including oxiranes) , in particular hydrofluoromonoethers , fluoroketones , in particular perfluoroketones , fluoroolefins , in particular hydrofluoroolefins , and fluoronitriles , in particular perfluoronitriles , and mixtures thereof. It is thereby particularly preferred that the further fluorinated organic compound FOC2 is a fluoroketone containing from four to twelve carbon atoms, preferably containing exactly five carbon atoms or exactly six carbon atoms or mixtures thereof.

The term "fluoroketone" as used in this application shall be interpreted broadly and shall encompass both perfluoroketones and hydrofluoroketones , and shall further encompass both saturated compounds and unsaturated compounds, i.e. compounds including double and/or triple bonds between carbon atoms. The at least partially fluorinated alkyl chain of the fluoro- ketones can be linear or branched, or can form a ring, which optionally is substituted by one or more alkyl groups. In exemplary embodiments, the fluoroketone is a perfluoroketone . In further exemplary embodiment, the fluoroketone has a branched alkyl chain, in particular an at least partially fluorinated alkyl chain. In still further exemplary embodiments, the fluoroketone is a fully saturated compound. As mentioned, it is particularly preferred that the further fluorinated organic compound FOC2 is a fluoroketone containing exactly five carbon atoms or exactly six carbon atoms or mixtures thereof. Compared to fluoroketones having a greater chain length with more than six carbon atoms, fluoroketones containing five or six carbon atoms have the advantage of a relatively low boiling point. Thus, problems which might go along with liquefaction can be avoided, even when the apparatus is used at low temperatures. According to embodiments, the fluoroketone is at least one compound selected from the group consisting of the compounds defined by the following structural formulae in which at least one hydrogen atom is substituted with a fluorine atom:

(Ie)

Fluoroketones containing five or more carbon atoms are further advantageous, because they are generally non-toxic with outstanding margins for human safety. This is in contrast to fluoroketones having less than four carbon atoms, such as hexafluoroacetone (or hexafluoropropanone) , which are toxic and very reactive. In particular, fluoroketones containing exactly five carbon atoms and fluoroketones containing exactly six carbon atoms are thermally stable up to 500°C.

In embodiments, those fluoroketones, in particular fluoro^¬ ketones containing exactly five carbon atoms, having a branched alkyl chain are preferred, because their boiling points are lower than the boiling points of the corresponding compounds (i.e. compounds with same molecular formula) having a straight alkyl chain.

According to embodiments, the fluoroketone is a perfluoro- ketone, in particular has the molecular formula C₅Fi₀O, i.e. is fully saturated without double or triple bonds between carbon atoms. The fluoroketone a) may more preferably be selected from the group consisting of: 1,1,1,3,4,4,4- heptafluoro-3- (trifluoromethyl) butan-2-one (also named decafluoro-2-methylbutan-3-one) , 1,1,1,3,3,4,4,5,5,5- decafluoropentan-2-one, 1,1,1,2,2,4,4,5,5, 5-decafluoropentan- 3-one and octafluorocylcopentanone, and most preferably is 1,1,1,3,4,4, 4-heptafluoro-3- (trifluoromethyl) butan-2 -one .

1,1,1,3,4,4, 4-heptafluoro-3- (trifluoromethyl) butan-2 -one can be represented by the following structural formula (I) :

C5K, i.e. 1, 1, 1, 3, 4, 4, 4-heptafluoro-3- (trifluoromethyl) butan- 2-one with molecular formula CF₃C (0) CF (CF₃) ₂ or C₅Fi₀O, has been found to be particularly preferred for high-voltage and medium-voltage insulation applications, because it has the advantages of high dielectric insulation performance, in particular in mixtures with a dielectric carrier gas, has very low GWP and has a low boiling point. It has an ODP of 0 and is practically non-toxic.

According to embodiments, even higher insulation capabilities can be achieved by combining the mixture of different fluoroketone components. In embodiments, a fluoroketone containing exactly five carbon atoms, as described above, and a fluoroketone containing exactly six carbon atoms or exactly seven carbon atoms, here briefly named fluoroketone c) , can favourably be part of the dielectric insulation at the same time. Thus, an insulation gas can be achieved having more than one fluoroketone, each contributing by itself to the dielectric strength of the insulation gas.

In embodiments, the further fluoroketone c) is at least one compound selected from the group consisting of the compounds defined by the following structural formulae in which at least one hydrogen atom is substituted with a fluorine atom:

as well as any fluoroketone having exactly 6 carbon atoms, in which the at least partially fluorinated alkyl chain of the fluoroketone forms a ring, which is substituted by one or more alkyl groups (Ilh); and/or is at least one compound selected from the group consisting of the compounds defined by the following structural formulae in which at least one hydrogen atom is substituted with a fluorine atom:

(Illh)

, and

(ΙΙΙη), e.g. dodecafluoro-cycloheptanone, as well as any fluoroketone having exactly 7 carbon atoms, in which the at least partially fluorinated alkyl chain of the fluoroketone forms a ring, which is substituted by one or more alkyl groups (IIIo) .

The present invention encompasses each compound or each combination of compounds selected from the group consisting of the compounds according to structural formulae (la) to (Ii), (Ha) to (Ilh), (Ilia) to (IIIo), and mixtures thereof.

Depending on the specific application of the present invention, a fluoroketone containing exactly six carbon atoms (falling under the designation "fluoroketone c) " mentioned above) may be preferred; such a fluoroketone is non-toxic, with outstanding margins for human safety.

In embodiments, fluoroketone c) , alike C5K, is a perfluoro- ketone, and/or has a branched alkyl chain, in particular an at least partially fluorinated alkyl chain; and/or the fluoroketone c) contains fully saturated compounds. E.g., the fluoroketone c) is or contains decafluorocyclohexanone . In particular, the fluoroketone c) has the molecular formula C₆Fi₂0, i.e. is fully saturated without double or triple bonds between carbon atoms. More preferably, the fluoroketone c) can be selected from the group consisting of: 1, 1, 1, 2, 4, 4, 5, 5, 5-nonafluoro-2- (trifluoromethyl) pentan-3-one (also named dodecafluoro-2-methylpentan-3-one) , l,l,l,3,3,4,5,5,5-nonafluoro-4- (trifluoromethyl) pentan-2 -one

(also named dodecafluoro-4-methylpentan-2-one) ,

1, 1, 1, 3, 4, 4, 5, 5, 5-nonafluoro-3- (trifluoromethyl) pentan-2 -one (also named dodecafluoro-3-methylpentan-2-one) ,

1, 1, 1, 4, 4, 4-hexafluoro-3, 3-bis- (trifluoromethyl) butan-2 -one (also named dodecafluoro-3, 3- (dimethyl) butan-2-one) , dodecafluorohexan-2-one, dodecafluorohexan-3-one, and particularly is the mentioned 1, 1, 1, 2, 4, 4, 5, 5, 5-Nonafluoro-2- ( trifluoromethyl) pentan-3-one .

1,1,1,2,4,4,5,5, 5-Nonafluoro-2- (trifluoromethyl) pentan-3-one (also named dodecafluoro-2-methylpentan-3-one) can be represented by the following structural formula (II) :

(ID 1,1,1,2,4,4,5,5, 5-Nonafluoro-4- (trifluoromethyl) pentan-3-one (here briefly called "C6-ketone", with molecular formula C₂F₅C (0) CF (CF₃) ₂) has been found to be particularly preferred for high-voltage insulation applications because of its high insulating properties and its extremely low GWP . Specifically, its pressure-reduced breakdown field strength is around 240 kV/ (cm*bar) , which is much higher than the one of air which has a much lower dielectric strength (E_cr = 25 kV/ (cm*bar) . It has an ozone depletion potential of 0 and is non-toxic (LC50 of about 100' 000 ppm) . Thus, the environmental impact is very low, and at the same time outstanding margins for human safety are achieved.

In additional or alternative embodiments, the further fluorinated organic compound FOC2 is a hydrofluoroether selected from the group consisting of: hydrofluoro monoether containing at least three carbon atoms; hydrofluoro monoether containing exactly three or exactly four carbon atoms; hydrofluoro monoether having a ratio of number of fluorine atoms to total number of fluorine and hydrogen atoms of at least 5:8; hydrofluoro monoether having a ratio of number of fluorine atoms to number of carbon atoms ranging from 1.5:1 to 2:1; pentafluoro-ethyl-methyl ether; 2 , 2 , 2-trifluoroethyl- trifluoromethyl ether; and mixtures thereof.

As mentioned above, the further fluorinated organic compound FOC2 can also be a fluoroolefin, in particular a hydrofluoroolefin . More particularly, the fluoroolefin or hydrofluorolefin, respectively, contains at least three carbon atoms or contains exactly three carbon atoms.

According to particularly preferred embodiments, the hydro- fluoroolefin is thus selected from the group consisting of: 1 , 1 , 1 , 2-tetrafluoropropene (HFO-1234yf; also named 2,3,3,3- tetrafluoro-l-propene) , 1, 2, 3, 3-tetrafluoro-2-propene (HFO- 1234yc) , 1, 1, 3, 3-tetrafluoro-2-propene (HFO-1234zc) , 1,1,1,3- tetrafluoro-2-propene (HFO-1234ze) , 1 , 1 , 2 , 3-tetrafluoro-2- propene (HFO-1234ye) , 1 , 1 , 1 , 2 , 3-pentafluoropropene (HFO- 1225ye) , 1 , 1 , 2 , 3 , 3-pentafluoropropene (HFO-1225yc) ,

1 , 1 , 1 , 3 , 3-pentafluoropropene (HFO-1225zc) , (Z) 1,1, 1,3- tetrafluoropropene (HFO-1234zeZ) ; also named cis-1, 3,3,3- tetrafluoro-l-propene) , (Z) 1,1,2, 3-tetrafluoro-2-propene

(HFO-1234yeZ) , (E) 1 , 1 , 1 , 3-tetrafluoropropene (HFO-1234zeE; also named trans-1, 3, 3, 3-tetrafluoro-l-propene) , (E)l, 1,2,3- tetrafluoro-2-propene (HFO-1234yeE) , ( Z ) 1 , 1 , 1 , 2 , 3- pentafluoropropene (HFO-1225yeZ ; also named cis- pentafluoroprop-l-ene) , (E) 1 , 1 , 1 , 2 , 3-pentafluoropropene (HFO- 1225yeE; also named trans-1, 2, 3, 3, 3 pentafluoroprop-l-ene) , and mixtures thereof.

As mentioned above, the further fluorinated organic compound FOC2 can also be a fluoronitrile, in particular a perfluoronitrile . In particular, the organofluorine compound can be a fluoronitrile, specifically a perfluoronitrile, containing two carbon atoms, three carbon atoms or four carbon atoms .

More particularly, the fluoronitrile can be a perfluoro- alkylnitrile, specifically perfluoroacetonitrile, perfluoro- propionitrile (C₂F₅CN) and/or perfluorobutyronitrile (C₃F₇CN) .

Most particularly, the fluoronitrile can be perfluoro- isobutyronitrile (according to the formula (CF₃)₂CFCN) and/or perfluoro-2-methoxypropanenitrile (according to the formula CF₃CF (OCF₃) CN) . Of these, perfluoroisobutyronitrile is most preferred due to its low toxicity.

The further fluorinated organic compound FOC2 being a fluoro- ketone containing exactly five carbon atoms, specifically a perfluoroketone containing exactly five carbon atoms, more specifically C5K, is highly preferred, due to the synergistic non-ideal behaviour found for the respective mixture, as reported by way of the figures below.

According to particularly preferred embodiments, the dielectric insulation or arc-extinction fluid thus comprises or essentially consists of hydrochlorofluoroolefin as fluorinated organic compound FOCI in mixture with a fluoroketone containing exactly five carbon atoms, specifically a perfluoroketone containing exactly five carbon atoms and more specifically C5K, as further fluorinated organic compound FOC2, the mixture optionally further comprising a carrier gas, in particular a carrier gas as described herein.

As will also be explained in more detail by way of the figures below, the further fluorinated organic compound FOC2 is preferably contained in a molar fraction ranging from 10% to 50%, more preferably from 15% to 40%, even more preferably from 20% to 30% and most preferably of about 25%, based on the sum of the molar amounts of the fluorinated organic compounds FOCI and FOC2. It has been found that FOC2 being contained in the mentioned ranges results in an optimum synergistic effect with regard to the dielectric performance.

It further embodiments, the second fluid component B is a carrier gas present in a molar amount that is higher than the molar amount of the first fluid component A, and optionally is higher than the sum of molar amount of the first fluid component A (FOCI) and the third fluid component C (FOC2) .

Accordingly, the present invention further relates to the use of a fluid mixture comprising or essentially consisting of:

A) a hydrochlorofluoroolefin as a first fluid component A and

B) a second fluid component B different from the first fluid component A, as a dielectric insulation fluid or arc-extinction fluid.

As mentioned, the suitability of a hydrochlorofluoroolefin- containing insulation or arc-extinction fluid as an environmentally friendly substitute of SF₆ has been most surprising, given the established doctrine that compounds containing chlorine generally have a relatively high ODP.

According to a further aspect, the present invention thus also relates to the use of the dielectric insulation or arc- extinction fluid described above in an apparatus for the generation, transmission, distribution and/or usage of electrical energy.

According to a still further aspect, the invention further relates to an apparatus for the generation, the transmission, the distribution and/or the usage of electrical energy, said apparatus comprising a housing enclosing an insulating space and an electrically conductive part arranged in the insulating space, said insulating space containing a dielectric insulation fluid comprising or essentially consisting of:

a) an organofluorine compound A as a first fluid component in mixture with

b) a second fluid component B different from the said first fluid component A,

wherein said first fluid component A is a hydrochloro- fluoroolefin .

Given the high dielectric performance achievable by the dielectric insulation fluid, smaller dielectric safety margins, in particular smaller spatial dielectric insulation distances, can be chosen, which allows for compact designs of the apparatuses, in particular for high-voltage applications, without affecting the proper functioning. Specifically, the apparatus of the present invention, in particular the gas-insulated apparatus, is part of or is a: switchgear, in particular gas-insulated switchgear (GIS) , or part and/or component thereof, gas-insulated line (GIL), busbar, bushing, cable, gas-insulated cable, cable joint, current transformer, voltage transformer, sensor, humidity sensor, surge arrester, capacitor, inductance, resistor, insulator, air-insulated insulator, a gas-insulated metal- encapsulated insulator, current limiter, high-voltage switch, earthing switch, disconnector, combined disconnector and earthing switch, load-break switch, circuit breaker, gas circuit breaker, generator circuit breaker, gas-insulated vacuum circuit breaker, medium-voltage switch, ring main unit, recloser, sectionalizer, low-voltage switch, and/or any type of gas-insulated switch, transformer, distribution transformer, power transformer, tap changer, transformer bushing, electrical rotating machine, generator, motor, drive, semiconducting device, computing machine, power semiconductor device, power converter, converter station, convertor building, and components and/or combinations of such devices.

The present invention is further illustrated by the attached figures of which:

Fig. 1 shows the vapour pressure-curve of HFCO-1233zd

(continuous line) to be contained in a dielectric insulation or arc-extinction fluid according to the present invention in comparison to the vapour pressure-curve of C5K (dashed line) ;

Fig. 2 shows the ratio of the maximum dielectric strength obtained for HCFO-1233zd to the respective maximum dielectric strength obtained for C5K at any given temperature over a temperature range of about 250 K to about 300 K; Fig. 3 shows the dew pressure (or condensation pressure or combined vapour pressure) of a mixture of HFCO- 1233zd and C5K at 5°C as a function of the gas- phase mole fraction of C5K calculated under the assumption of an ideal gas mixture using Raoult's law (dashed line) and using a quantum chemical method predicting a synergistic non-ideal behaviour (continuous line) ; and

Fig. 4 shows the ratio of the dielectric strength of a mixture containing HFCO-1233zd and C5K to the dielectric strength of pure C5K as a function of the gas phase mole fraction of C5K.

As mentioned, the pressure-reduced dielectric strength of HCFO-1233zd is slightly lower than the one of C5K at identical conditions. In more concrete terms, the breakdown voltage at 500 mbar of HCFO-1233zd was found to be about 150 kV/cm/bar in uniform field conditions (Rogowski profile electrodes, technical surface with a high roughness defined by a Mean Roughness Depth (R_z) of about 60 μιη) . Using the same experimental setup, the breakdown voltage at 500 mbar of C5K was found to be about 160 kV/cm/bar, i.e. less than 10% higher than the one of HCFO-1233zd.

However, the vapour pressure of HCFO-1233zd is higher than the one of C5K at least over a temperature range from about 250 K to about 300 K, as shown in Fig. 1. The temperature range shown in Fig. 1 corresponds to the relevant temperature range of typical minimum operating temperature of electrical apparatuses of interest. In other words, for any electrical apparatus of interest and any minimum operating temperature for which it is rated, the vapour pressure of HCFO-1233zd is higher than the one of C5K. Given the higher vapour pressure of HCFO-1233zd in comparison to C5K, a higher partial pressure of HCFO-1233zd can be achieved at the same operating conditions. In consequence, a higher dielectric strength can be achieved for HCFO-1233zd than for C5K at the same operating conditions, as shown in Fig. 2.

The plot given in Fig. 3 was obtained by implementing the "cosmo-rs" method used for evaluating the composition- dependence of the dew pressure of the mixture at a temperature of 5°C. The "cosmo-rs" method is known to the person skilled in the art. The respective software is e.g. available through the Cosmotherm product webpage of Cosmologic; another implementation of the method exists within the "ADF" software package (www . scm. com) another via the DDBSP package (www . ddbst . com) , for example.

As shown in Fig. 3, a maximum dew pressure of about 620 mbar was determined for a mixture containing about 25% of C5K and 75% of HFCO-1233zd. Compared to pure HFCO-1233zd, this mixture will thus stay in purely gaseous phase up to a higher pressure, namely up to 620 mbar, compared to the maximum pressure of about 595 mbar allowed for pure HFCO-1233zd. This implies that for a given minimum operating temperature of an electrical apparatus, a higher concentration of fluorinated organic compounds in gaseous form can be obtained than expected under the assumption of ideal gas behaviour. With regard to Fig. 3, the term dew pressure is to be understood as the pressure at constant temperature (in the specific case at 5°C) at which the gaseous mixture condenses into the liquid phase at the same rate at which it evaporates. As further shown in Fig. 4, a higher partial pressure directly translates into an increase of the dielectric performance. By increasing the dew pressure, the presence of C5K in the gas mixture thus leads to a substantial increase in the dielectric strength of the gas mixture over the one of either pure HFCO-1233zd or pure C5K. This synergistic effect between hydrochlorofluoroolefin and the fluoroketone, in particular between trans-isomer of l-chloro-3, 3, 3-trifluoro- propene and C5K, is present also when a background or carrier gas is mixed in.

Claims

1. Dielectric insulation or arc-extinction fluid comprising or essentially consisting of:

b) a second fluid component B different from the said first fluid component A,

wherein said first fluid component A is a hydrochloro- fluoroolefin .

2. Dielectric insulation or arc-extinction fluid according to claim 1, wherein the hydrochlorofluoroolefin has a boiling point of less than 40°C.

3. Dielectric insulation or arc-extinction fluid according to any one of the preceding claims, the hydrochloro- fluoroolefin containing from 2 to 5 carbon atoms, more preferably from 3 to 4 carbon atoms, and most preferably containing exactly 3 carbon atoms.

4. Dielectric insulation or arc-extinction fluid according to any one of the preceding claims, wherein the hydrochlorofluoroolefin is l-chloro-3, 3, 3-trifluoro- propene, in particular the trans-isomer of 1-chloro- 3,3, 3-trifluoropropene .

5. Dielectric insulation or arc-extinction fluid according to any one of the preceding claims, wherein the second fluid component B comprises or consists of a carrier gas, which has a boiling point of -60°C at most.

6. Dielectric insulation or arc-extinction fluid according to any one of the preceding claims, wherein the second fluid component B comprises or consists of a carrier gas, which itself has a lower dielectric strength than the first fluid component A.

7. Dielectric insulation or arc-extinction fluid according to any one of the preceding claims, wherein the second fluid component B comprises or consists of a carrier gas selected from the group consisting of: oxygen, nitrogen, carbon dioxide, nitrous oxide, nitric oxide, nitrogen dioxide, and mixtures thereof.

8. Dielectric insulation or arc-extinction fluid according to any of the preceding claims, wherein the second fluid component B comprises or consists of carbon dioxide.

9. Dielectric insulation or arc-extinction fluid according to any of the preceding claims, wherein the second fluid component B comprises or consists of oxygen.

10. Dielectric insulation or arc-extinction fluid according to any of the preceding claims, wherein the second fluid component B comprises or consists of a mixture of carbon dioxide and oxygen.

11. Dielectric insulation or arc-extinction fluid according to claim 10, wherein the ratio of the amount of carbon dioxide to the amount of oxygen ranges from 50:50 to 100:1, preferably from 80:20 to 95:5, more preferably from 85:15 to 92:8, even more preferably from 87:13 to less than 90:10, and in particular is about 89:11.

12. Dielectric insulation or arc-extinction fluid according to any one of the preceding claims, wherein it comprises as the second fluid component B or as a third fluid component C a further fluorinated organic compound FOC2 different from the hydrochlorofluoroolefin of the first fluid component A. Dielectric insulation or arc-extinction fluid according to claim 12, wherein it comprises or essentially consists of

a) a hydrochlorofluoroolefin as first fluid component A in mixture with

β) a carrier gas as second fluid component B, and

γ) at least one further fluorinated organic compound FOC2 different from the hydrochlorofluoroolefin of the first fluid component A.

Dielectric insulation or arc-extinction fluid according to any one of the claims 12 to 13, wherein the further fluorinated organic compound FOC2 is an organofluorine compound devoid of chlorine atoms.

Dielectric insulation or arc-extinction fluid according to any one of the claims 12 to 14, wherein the further fluorinated organic compound FOC2 is at least one compound selected from the group consisting of: fluoro- ethers, in particular hydrofluoromonoethers , fluoro- ketones, in particular perfluoroketones , fluoroolefins , in particular hydrofluoroolefins , fluoronitriles , in particular perfluoronitriles , and mixtures thereof.

Dielectric insulation or arc-extinction fluid according to any one of the claims 12 to 15, wherein the further fluorinated organic compound FOC2 is a fluoroketone containing from four to twelve carbon atoms, preferably containing exactly five carbon atoms or exactly six carbon atoms or a mixture thereof.

Dielectric insulation or arc-extinction fluid according to any one of the claims 12 to 16, wherein the further fluorinated organic compound FOC2 is at least one compound selected from the group consisting of the compounds defined by the following structural formulae in which at least one hydrogen atom is substituted with a fluorine atom:

(ig)

Dielectric insulation or arc-extinction fluid according to any one of the claims 12 to 17, wherein the further fluorinated organic compound FOC2 is a compound having the molecular formula C₅Fi₀O and, in particular, being selected from the group consisting of: 1,1,1,3,4,4,4- heptafluoro-3- (trifluoromethyl) butan-2 -one,

1,1,1,3,3,4,4,5,5, 5-decafluoropentan-2-one,

1,1,1,2,2,4,4,5,5, 5-decafluoropentan-3-one, and 1,1,1,4,4,5,5,5, -octafluoro-3-bis (trifluoromethyl) - pentan-2-one; and preferably is 1,1,1,3,4,4,4- heptafluoro-3- (trifluoromethyl) butan-2 -one .

Dielectric insulation or arc-extinction fluid according to any ine of the claims 12 to 18, wherein the further fluorinated organic compound FOC2 is a hydrofluoro- monoether containing at least three carbon atoms.

Dielectric insulation or arc-extinction fluid according to any one of the claims 12 to 19, wherein the further fluorinated organic compound FOC2 is contained in a molar fraction ranging from 10% to 50%, preferably from 15% to 40%, more preferably from 20% to 30% and most preferably of about 25%, based on the sum of the molar amounts of the fluorinated organic compounds FOCI and

FOC2.

21. Dielectric insulation or arc-extinction fluid according to any one of the claims 12 to 20, wherein it comprises or essentially consists of hydrochlorofluoroolefin as fluorinated organic compound FOCI in mixture with a fluoroketone containing exactly five carbon atoms, specifically a perfluoroketone containing exactly five carbon atoms, more specifically 1,1,1,3,4,4,4- heptafluoro-3- (trifluoromethyl) -butan-2-one, as further fluorinated organic compound FOC2, the mixture optionally further comprising a carrier gas.

22. Dielectric insulation or arc-extinction fluid according to any one of the preceding claims, wherein the second fluid component B is a carrier gas present in a molar amount that is higher than the molar amount of the first fluid component A and optionally the sum of molar amount of the first fluid component A and the third fluid component C.

23. Use of a fluid mixture comprising or essentially consisting of:

A) a hydrochlorofluoroolefin as a first fluid component A and

B) a second fluid component B different from the said first fluid component A,

as a dielectric insulation fluid or arc-extinction fluid .

24. Use of the dielectric insulation or arc-extinction fluid according to any one of the claims 1 to 23 in an apparatus for the generation, the transmission, the distribution and/or the usage of electrical energy.

25. Apparatus for the generation, the transmission, the distribution and/or the usage of electrical energy, said apparatus comprising a housing enclosing an insulating space and an electrically conductive part arranged in the insulating space, said insulating space containing a dielectric insulation fluid comprising or essentially consisting of:

a) an organofluorine compound A as a first fluid component in mixture with

b) a second fluid component B different from the said first fluid component A,

wherein said first fluid component A is a hydrochlorofluoroolefin .

Apparatus according to claim 25, wherein the apparatus, in particular the gas-insulated apparatus, is part of or is a: switchgear, in particular gas-insulated switchgear (GIS) , or part and/or component thereof, gas-insulated line (GIL) , busbar, bushing, cable, gas-insulated cable, cable joint, current transformer, voltage transformer, sensor, humidity sensor, surge arrester, capacitor, inductance, resistor, insulator, air-insulated insulator, a gas-insulated metal-encapsulated insulator, current limiter, high-voltage switch, earthing switch, disconnector, combined disconnector and earthing switch, load-break switch, circuit breaker, gas circuit breaker, generator circuit breaker, gas-insulated vacuum circuit breaker, medium-voltage switch, ring main unit, recloser, sectionalizer, low-voltage switch, and/or any type of gas-insulated switch, transformer, distribution transformer, power transformer, tap changer, transformer bushing, electrical rotating machine, generator, motor, drive, semiconducting device, computing machine, power semiconductor device, power converter, converter station, convertor building, and components and/or combinations of such devices.