The present invention relates to an electrical apparatus for the generation, the transmission and/or the distribution of electrical energy, according to the preamble of claim 1 , as well as to the use of a speci fic adsorber in an electrical apparatus for the generation, the transmission and/or the distribution of electrical energy .

In electrical apparatuses , dielectric insulation media in gaseous or liquid state are conventionally applied for the insulation of an electrical component .

In metal-encapsulated switchgears , for example , the active parts are arranged in a gas-tight housing, which defines an insulating space comprising an insulation gas . For interrupting the current in e . g. high voltage switchgears , the insulating gas further functions as an arc-extinction gas .

Sulphur hexafluoride ( SF ₆ ) is a well-established insulation gas due to its outstanding dielectric properties and its chemical inertness . Despite these properties , ef forts to look for an alternative insulation gas have nevertheless been intensi fied, in particular in view of a substitute having a lower Global Warming Potential ( GWP ) than the one of SF ₆ .

In view of providing a non-SF ₆ substitute , the use of organof luorine compounds in dielectric insulation media has been suggested .

WO-A-2010/ 142346 suggests 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. Owed to the combination of these characteristics, fluoroketones constitute a viable alternative to SF ₆ .

Further developments in this regard are reflected in WO-A- 2012/080246 suggesting a dielectric insulation gas comprising a fluoroketone containing exactly 5 carbon atoms, in particular 1, 1, 1, 3, 4, 4, 4-heptaf luoro-3- (trifluoromethyl) -butan-2-one (hereinafter also referred to as C5-FK) , 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.

Further attempts in finding an alternative "non-SF ₆ " insulation medium are reflected in WO 2013/151741 suggesting the use of heptaf luoroisobutyronitrile, (CF ₃ ) ₂ CFCN (hereinafter also referred to as "C4-FN") , or 2 , 3 , 3 , 3-tetraf luoro-2- ( trifluoromethoxy) propanenitrile (CF ₃ CF (OCF ₃ ) GN, as a dielectric fluid.

Based thereon, WO 2015/040069 describes an electrical apparatus of medium or high voltage comprising a housing, in which a gaseous medium comprising heptaf luoroisobutyronitrile, carbon dioxide and oxygen is contained.

All of the organof luorine compounds mentioned above have in common that they are less inert than SF ₆ . Although a reduced inertness is wanted in view of the organof luorine compound' s reduced GWP, reaction with other compounds contained in the electric apparatus is unwanted, since this has at the one hand a negative impact on the performance of the dielectric insulation medium (mainly due to the decrease in the concentration of the organof luorine compound) . On the other hand, the decomposition products or by-products formed can compromise the function of the apparatus and/or give raise to health and safety risks .

This is in particular the case for hydrofluoric acid, which is highly toxic and which can be formed as a by-product from reaction of a fluoroketone with water . Also with regard to fluoronitriles , moisture ( or humidity) in the insulation space has been found to a be key driver for decomposition and thus for the generation of potentially harmful by-products .

It is therefore imperative that moisture contained in the insulation space is at least partially removed and that moisture is thus not available or only available in very limited amounts as a reaction partner of the organof luorine compound .

For removing moisture from the insulation space of an electric apparatus , several desiccants have been proposed . EP2904617A, for example , mentions the use of a desiccant selected from the group consi sting of : calcium, calcium sulphate , in particular drierite , calcium carbonate , calcium hydride , calcium chloride , potassium carbonate , potassium hydroxide , copper ( I I ) sulphate , calcium oxide , magnesium, magnesium oxide , magnesium sulphate , magnesium perchlorate , sodium, sodium sulphate , lithium aluminium hydride , montmorrilonite , phosphorpentoxide , silica gel and a cellulose filter .

WO 2020/254004 Al discloses a dielectric- insulation or arcextinction f luid containing a dielectric compound, which - in having similar dielectric properties compared to octafluorobutene - has a higher stability when subj ected to partial discharge in the presence of oxygen . The fluid disclosed is a mixture comprising a fluoroolefin and oxygen, wherein the fluoroolefin is a monohydrofluoroolefin containing from 4 to 5 carbon atoms , the hydrogen atom being bound to a carbon atom of the double bond or directly adj acent to the double bond . An electrical insulation apparatus is also disclosed, wherein the dielectric-insulation or arc-extinction fluid can be used with a conventional adsorber, primarily designed to remove water and impurities from the insulation space , without facing the problem o f the monohydrofluoroolefin being adsorbed by the adsorber . The adsorber can be a zeolite having a pore si ze from 3 to 5 A used for desiccation of the insulation space , as there is no or only negligible adsorption of the monohydrofluoroolefin containing from 4 to 5 carbon atoms .

EP 3 671 764 Al discloses an electrical insulation system for medium or high voltage electrical switchgear comprising a gaseous medium consisting of a mixture of one or more fluoroketones of between 5 and 6 carbon atoms , one or more non- flammable hydrofluoroolefins of 4 carbon atoms and one , two or three carrier gases selected from N2 , 02 , dry air, helium or mixtures thereof ; and a molecular sieve having a pore si ze of 3 to 6 A and a polar surface . The molecular sieve can be a zeolite sieve . The zeolite may be natural or synthetic zeolite .

US 2018 / 005727 Al discloses an electrical apparatus for the generation, transmission, distribution and/or usage of electrical energy comprising a housing enclosing an insulating space and an electrical component arranged in the insulating space . The insulating space contains a dielectric insulation gas comprising an organof luorine compound . The apparatus further comprises a desiccant arranged such as to come into contact with the insulation gas . The desiccant contains lithium bromide that does neither adsorb organof luorine compound molecules nor carrier gas molecules and thus leaves the composition of the insulation gas unaf fected . In addition to the desiccant containing lithium bromide , the apparatus can further comprise at least one molecular sieve in the form of a zeolite arranged such as to come into contact with the insulation gas .

In addition, zeolites are currently being used as adsorber in some industrial applications , including SF ₆ -using high voltage switchgear, and a large variety of zeolites are commercially available , some of which are based on natural occurring minerals (moederite , stilbite , or the like ) and some syntheti zed ( type A, X, Y and L crystal types ) . For handling reasons , the zeolites are often used in the form of beads or pellets and can comprise some binding agent , typically clay, for providing mechanical stability .

Although the use of zeolites allows favourable properties in terms of adsorption to be achieved, investigations revealed that the problem of decomposition products being formed is not completely solved .

In the case of an apparatus using perfluoroisobutyronitrile ( C4-FN) , it has for example been found that various decomposition products can form, some of which form crystalline deposits in the interior of the apparatus . In this regard, reference is made to Juhre et al . , Cigre Report ID 1114 , (" Investigations on the long-term performance of Fluoronitrile-containing gas mixtures in gas-insulated systems") , reporting on tests, in which a zeolite type with a pore size of 3 A was used but which nevertheless resulted in the formation of solid decomposition products. In addition, the formation of decomposition products when exposing C4-FN to a moisture containing environment is also reported in Kessler et al., "Compatibility of a Gaseous Dielectric with Al, Ag, and Cu and Gas-Phase Synthesis of a New N-Acylamidine Copper Complex", Eur . J. Inorg. Chem. 2020, 1989-1994.

According to these investigations, the main components of the decomposition products of C4-FN are perfluorobutyroamide (2,3,3, 3-tetra-f luoro-2- (trifluoromethyl) propane amide)

(decomposition product A) : (decomposition product A) as well as the N-acyl amidine dimer of this compound (decomposition product B) :

(decomposition product B) and N-acyl amidine metal complexes (decomposition product C) :

( decomposition product C ) .

In consideration of the increasing need to reduce the use of SF ₆ to a minimum, it would be desirable to provide a "non-SF ₆ electric apparatus" for the generation, the transmission and/or the distribution of electrical energy, i . e . an apparatus which uses an alternative gas other than SF ₆ and hence complies with the requirement of improved environmental friendliness , in particular a reduced carbon footprint , but which does not have the drawbacks mentioned above . In particular, there is a need to ef ficiently remove at least moisture from the insulation space of such an electrical apparatus , but without compromising the performance and the safety of the electrical apparatus .

The problem to be solved by the present invention is thus to provide a non-SF ₆ electrical apparatus for the generation, the transmission and/or the distribution of electrical energy, in particular a non-SF ₆ apparatus , more particularly a gas insulated switchgear ( GIS ) , the GIS being a GIS for transmission, a GIS for sub-transmission, or an integrated GIS ; a gas-insulated line ; a hybrid switchgear ( gas insulated modules ) ; a circuit breaker being a live tank breaker, a dead tank breaker, or an interrupter unit ; a switch being a grounding or earthing switch, an isolation switch or disconnector, or a fast acting earth switch; a trans former being an instrument or measurement transformer, a power transformer or a distribution transformer; a gas-insulated surge arrester; or extensions, upgrades or retrofits or a component or combinations thereof, which allows removing moisture or other unwanted impurities (i.e. contaminants and/or decomposition products resulting due to arcing or partial discharge) efficiently from the insulation space but with a low tendency of unwanted decomposition products e.g. A (Amide) , B (Dimer) , C (Complex) being formed. The problem is solved by the apparatus according to claim 1. Preferred embodiments of the invention are defined in the dependent claims.

According to claim 1, the invention relates to an electrical apparatus for the generation, the transmission and/or the distribution of electrical energy.

The electrical apparatus may be energi zed with a voltage higher than 1 kV, and more preferably energi zed at medium or high voltage . In this regard, it can be preferred that the electrical apparatus is energi zed with a voltage higher than 12 kV or with a voltage higher than 52 kV .

As further defined in claim 1 , the electrical apparatus comprises a housing enclosing an electrical apparatus interior space , at least a portion of the electrical apparatus interior space forming an insulation space , in which an electrical component is arranged and which contains an insulation medium surrounding the electrical component .

The insulation medium contains an organof luorine compound, in particular C4-FN or C5-FK, which has a reduced GWP and a smaller carbon footprint compared to SF ₆ , as discussed above .

The electrical apparatus further comprises an adsorber, speci fically an adsorber for removing at least a part of a contaminant and/or decomposition product resulting from arcing or partial discharge in the insulation space . For example , the adsorber can be used for removing moisture or other unwanted impurities or gaseous decomposition products ( resulting from arcing or partial discharge ) contained in the insulation space . It should be noted that a contaminant such as moisture may get introduced in the insulation space due to a reaction in the insulation space , or during gas filling or service ( e . g . during gas handling) .

According to the invention, the adsorber comprises a zeolite , in particular a zeolite containing

- less than 0 . 5 at% of magnesium (Mg)

- less than 0 . 5 at% of calcium ( Ca ) and

- less than 0 . 5 at% of iron ( Fe ) . As will be discussed by way of the speci fic working examples , it has surprisingly been found by the present inventors that an adsorber preferably comprising a zeolite as defined above does not lead to any of the solid decomposition products A, B or C being formed in the insulation space , even i f harsh conditions are applied . The present invention therefore allows moisture or other unwanted impurities or gaseous by-products ( resulting from arcing or partial discharge ) to be ef ficiently removed and at the same time the formation of potentially harmful decomposition products to be reduced or completely avoided .

In particular, it was found that issues regarding incompatibility with the organof luorine compound used in the dielectric insulation medium could be reduced or even completely avoided . Without wanting to be bound by the theory, it is assumed that the adsorber according to the present invention does not function as a catalyst for decomposition reactions as it may be the case for adsorbers not falling under the definition of the invention, thus leading to the formation of solid decomposition products .

The technical ef fect achieved by the present invention is particularly pronounced in case the electrical apparatus is a gas-insulated switchgear or a component thereof , due to the fact that the drawbacks mentioned above are particularly profound in a gas-insulated switchgear . However, all other electric apparatuses for the generation, the transmission and/or the distribution of electrical energy are covered by the present invention, in particular live tank breakers, dead tank breakers, gas insulated bus ducts, arresters, bushings and/or transformers.

According to a preferred embodiment of the present invention, the electrical apparatus is thus a gas insulated switchgear (GIS) , the GIS being a GIS for transmission, a GIS for subtransmission, or an integrated GIS; a gas-insulated line; a hybrid switchgear (gas insulated modules) ; a circuit breaker being a live tank breaker, a dead tank breaker, or an interrupter unit; a switch being a grounding or earthing switch, an isolation switch or disconnector, or a fast acting earth switch; a transformer, being an instrument or measurement transformer, a power transformer or a distribution transformer; a gas-insulated surge arrester; and extensions, upgrades and retrofits or a component or combinations thereof.

According to a preferred embodiment of the invention, the adsorber, and preferably the zeolite, contains less than 0.25 at% of Mg, more preferably less than 0.10 at% of Mg and most preferably is at least approximately devoid of Mg. For this preferred embodiment, there is an even lower tendency for the decomposition products mentioned being formed.

Additionally or alternatively, it is further preferred that the adsorber, and preferably the zeolite, contains less than 0.25 at% of Ca, more preferably less than 0.10 at% of Ca and most preferably is at least approximately devoid of Ca, for the same reason that the tendency of decomposition product formation is reduced even further. Additionally or alternatively, it is further preferred that the adsorber, and preferably the zeolite, contains less than 0.25 at% of Fe, preferably less than 0.15 at% of Fe and most preferably is at least approximately devoid of Fe, for the reason mentioned above in the context of Mg and Ca.

In particular, the organof luorine compound used in the context of the present invention is a fluoroketone, in particular a perfluoroketone, and/or a fluoronitrile, in particular a perfluoronitrile .

According to a particularly preferred embodiment, the organof luorine compound is a fluoronitrile, and in particular a perfluoronitrile. More particularly, the fluoronitrile can be a perfluoroalkylnitrile, specifically perfluoroacetonitrile, perfluoropropionitrile (C ₂ F ₅ CN) and/or perfluorobutyronitrile (C ₃ F ₇ CN) . Preferably, the fluoronitrile is perfluoroisobutyronitrile (according to the formula (CF ₃ ) ₂ CFCN) and/or perf luoro-2-methoxypropanenitrile (according to the formula CF ₃ CF (OCF ₃ ) CN) . Of these, perfluoroisobutyronitrile (C4-FN) is particularly preferred.

Typically, the dielectric insulation medium additionally contains a carrier gas (or background gas) selected from the group of air, an air component, in particular nitrogen and/or oxygen, carbon dioxide and mixtures thereof.

The carrier gas used can essentially consist of only one component, for example carbon dioxide or nitrogen. Alternatively, the carrier gas can contain at least one further carrier gas component besides carbon dioxide or nitrogen (being the first component) , in particular in an amount lower than the one of the first component. Specifically, the at least one further carrier gas component can be an oxidizing gas, in particular oxygen, for reducing the formation o f soot and/or other unwanted decomposition products . More speci fically, the insulation medium of the present invention relates to a ternary mixture containing C4-FN, carbon dioxide and oxygen or a ternary mixture containing C4-FN, nitrogen and oxygen .

Alternatively or additionally to the fluoronitrile contained in the speci fic insulation medium defined above , the alternative insulation medium can contain a fluoroketone , more particularly a perfluoroketone .

As mentioned above , the adsorber used is preferably comprising the zeolite in the form of beads or pellets . Typically, it is arranged in a sachet or casing which allows the insulation gas to permeate at least partially .

According to a further preferred embodiment of the invention, the zeolite has a pH less than 8 , since this has been found to further contribute to a reduced tendency of decomposition products being formed . In the context of the present invention, the pH o f the zeolite refers to the pH of the solution obtained by dissolving 5 g of the zeolite in 50 ml of distilled water .

It has surprisingly been found that also the amount of clay used as a binder in the zeolite-containing adsorber and to provide the latter with the required stability has an impact on the compatibility with the organof luorine compound . In this regard, an amount of clay of less than 3 wt-% , based on the total weight of the zeolite , has been found to be particularly preferred . Most preferably, the zeolite-containing adsorber is at least approximately devoid of clay . In a preferred embodiment, the adsorber is primarily a moisture— adsorber for removing at least a part of the moisture (or humidity) contained in the insulation space.

In view of an even further reduction of the tendency to form unwanted decomposition products, it is further preferred that the average pore size diameter of the zeolite- is in the range from 0.25 to 0.55 nm.

Besides the electrical apparatus discussed above, a further aspect of the present invention relates to the use of an adsorber for removing at least a part of a contaminant and/or decomposition product resulting from arcing or partial discharge, the adsorber containing

- less than 0.5 at% of magnesium (Mg)

- less than 0.5 at% of calcium (Ca) and

- less than 0.5 at% of iron (Fe) in an electrical apparatus for the generation, the transmission, the distribution and/or the usage of electrical energy, in particular an electrical apparatus of medium or high voltage. More particularly, the electrical apparatus is a gas insulated switchgear (GIS) being a GIS for transmission or sub-transmission, or an integrated GIS; a gas-insulated line; a hybrid switchgear (gas insulated modules) ; a circuit breaker being a live tank breaker, a dead tank breaker, or an interrupter unit; a switch being a grounding or earthing switch, an isolation switch or disconnector, or a fast acting earth switch; a transformer being an instrument or measurement transformer, a power transformer or a distribution transformer; a gas-insulated surge arrester; or extensions, upgrades or retrofits or a component or combinations thereof.

Preferably, the adsorber comprises a zeolite, more preferably a zeolite containing - less than 0.5 at% of magnesium (Mg)

- less than 0.5 at% of calcium (Ca) and

- less than 0.5 at% of iron (Fe) .

EXAMPLES

The invention is further illustrated by way of the following examples and the attached figures, of which

Fig. 1 shows a photographic picture of beads of an adsorber falling within the definition of the present invention after exposure to a dielectric insulation medium containing C4-FN and air in a test vessel at 70 °C ;

Fig. 2 shows a photographic picture of beads of an adsorber falling outside the definition of the present invention after exposure to a dielectric insulation medium containing C4-FN and air in a test vessel at 70 °C ;

Fig. 3 shows the FTIR spectrum of the adsorber shown in Fig. 1 (i.e. according to the present invention) prior to exposure (A) and after exposure (B) ; and

Fig. 4 shows the FTIR spectrum of the adsorber shown in Fig. 2 (i.e. according to the comparative example) prior to exposure (A) and after exposure (B) .

In a first series of tests, a bead-shaped adsorber comprising a zeolite of type A, 4A was exposed to a dielectric insulation medium containing C4-FN and air in a test vessel at 70°C and was examined after exposure.

The composition of the zeolite of this adsorber (Sample 1) as determined by EDX analysis was as follows, thus complying with the definition of the present invention: Referring to Fig. 1 and 2, it was observed that for comparative Sample 2 crystals were formed (Fig. 2) whereas no such crystals were detected for Sample 1 (Fig. 1) . The FTIR spectra confirmed the formation of the N-acyl amidine dimer (decomposition product B) , whereas no decomposition products were identified for Sample 1 (with the spectrum in the respective range after exposure essentially corresponds to the one prior to exposure) .

Composition of Sample 1 in at%

0 60.15

Na 10.20

Al 14.70

Si 14.68

Mg <LOD

Ca <LOD

Fe 0.10

K <LOD

S 0.05

Ti 0.12

* (with <LOD standing for a concentration below the lower detection limit) pH 7-8 (5g of zeolite in 50mL of distilled water)

For reasons of comparison, a zeolite of type A, 4A (Sample 2) was used under the exact same conditions as described for Sample 1, Sample 2 having the following composition: Composition of Sample 2 in at%

0 61.93

Na 9.58

Al 11.42

Si 13.85

Mg 0.90

Ca 0.40

Fe 0.37

K 1.45

S 0.10

Ti <LOD pH 9-10 (5g of zeolite in 50mL of distilled water) The finding was confirmed by measurements made in a further test series examining the zeolite mentioned below after exposure to the conditions defined above for Sample 1 and Sample 2. Of these, the zeolites according to Sample 3 and 6 (having a composition falling within the definition of the present invention) did not show any crystal formation after the test at 70 °C in the insultation medium (containing C4-FN and air) , whereas crystals were formed for Sample 4 and 5 (having a composition falling outside the definition of the present invention) if exposed to the same insulation gas and conditions: Sample No 3 6 4 5

Zeolite A, 4A A A, 3A FAU type at% at% at% at%

0 62.30 0 62.15 0 63.45 0 62.65

Na 11.00 Na 6.63 Na 6.59 Na 10.72

Al 13.28 Al 14.13 Al 11.17 Al 11.00

Si 13.10 Si 13.30 Si 13.36 Si 14.25

Mg <LOD Mg <LOD Mg 1.06 Mg 0.71

Ca <LOD Ca <LOD Ca 0.31 Ca 0.30

Fe <LOD Fe 0.07 Fe 0.29 Fe 0.17

K 0.22 K 3.72 K 3.61 K 0.12

S 0.09 S <LOD S 0.16 S <LOD

Ti 0.01 Ti <LOD Ti <LOD Ti <LOD pH 7-8 7-8 9-10 9-10

(5g of zeolite in 50mL of distilled water) after no no crystals crystals test at crystals crystals

70 °C in

C4-FN/air mixture