GAS-INSULATED ELECTRICAL APPARATUS COMPRISING CARBON DIOXIDE, HEPTAFLUOROISOBUTYRONITRILE AND A HIGH CONTENT OF OXYGEN

Abstract

The present application concerns a medium- or high-voltage equipment including a leaktight enclosure in which there are located electrical components and a gas mixture for providing electrical insulation and/or for extinguishing electric arcs that are likely to occur in the enclosure, the gas mixture including heptafluoroisobutyronitrile, carbon dioxide, and a high content of oxygen

Claims

1.-13. (canceled)

1. A medium- or high-voltage equipment including a leaktight enclosure in which there are located electrical components and a gas mixture for providing electrical insulation and/or for extinguishing electric arcs that are likely to occur in said enclosure, the gas mixture comprising heptafluoroisobutyronitrile, carbon dioxide and oxygen, wherein oxygen presents a molar percentage equal to or higher than 26%, in said gas mixture.

2. The equipment according to claim 1, wherein oxygen in said gas mixture presents a molar percentage lying in the range 28% to 50%.

3. The equipment according to claim 1, wherein oxygen in said gas mixture presents a molar percentage lying in the range 30% to 50%.

4. The equipment according to claim 1, wherein said gas mixture comprises or consists of: from 40 mol % to 72 mol % of carbon dioxide, from 2 mol % to 10 mol % of heptafluoroisobutyronitrile, and at least 26 mol % of oxygen.

5. The equipment according to claim 2, wherein said gas mixture comprises: from 40 mol % to 70 mol % of carbon dioxide, from 2 mol % to 10 mol % of heptafluoroisobutyronitrile, and from 28 mol % to 50 mol % of oxygen.

6. The equipment according to claim 3, wherein said gas mixture comprises: from 40 mol % to 68 mol % of carbon dioxide, from 2 mol % to 10 mol % of heptafluoroisobutyronitrile, and from 30 mol % to 50 mol % of oxygen.

7. The equipment according to claim 1, wherein part of the electrical components arranged inside the enclosure of said equipment is covered by solid insulating layers.

8. The equipment according to claim 1, wherein said equipment is a gas-insulated electrical transformer, an overhead or buried gas-insulated line, a set of busbars for transporting or distributing electricity, an element for connection to the other equipment in the network, or a connector/disconnector.

9. The equipment according to claim 1, wherein said equipment presents a minimum pressure of 7.5 bars (i.e. 7500 hPa) absolute and a nominal pressure of 8.5 bars (i.e. 8500 hPa) absolute.

10. Use of a gas mixture comprising heptafluoroisobutyronitrile, carbon dioxide and oxygen, as a gas for electrical insulation and/or for electric arc extinction in medium- or high-voltage equipment, in which part of the electrical components may further be covered with a solid insulating layer as defined below, wherein oxygen presents a molar percentage equal to or higher than 26%, in said gas mixture.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0073] FIG. 1 presents the liquefaction temperature of gas mixtures comprising CO.sub.2, 6 mol % of (CF.sub.3).sub.2CF—CN and different mole percentages of O.sub.2, at a pressure of 7.5 bars (i.e. 7500 hPa) absolute or at a pressure of 8.5 bars (i.e. 8500 hPa).

[0074] FIG. 2 presents the pressure at liquefaction as a function of temperature for gas mixtures comprising CO.sub.2, 6 mol % of (CF.sub.3).sub.2CF—CN (Novec 6 mol %) and different mole percentages of O.sub.2.

DETAILED DESCRIPTION

[0075] In the following experiments, the leaktight enclosure of a high-voltage equipment was filled subsequently starting by (CF.sub.3).sub.2CF—CN, and CO.sub.2 and O.sub.2 at the end.

[0076] The liquefaction temperature of gas mixtures comprising CO.sub.2, 6 mol % of (CF.sub.3).sub.2CF—CN and different mole percentages of O.sub.2, at a pressure of 7.5 bars (i.e. 7500 hPa) absolute or at a pressure of 8.5 bars (i.e. 8500 hPa) absolute is presented in FIG. 1.

[0077] The obtained values for the liquefaction temperature are summarized in the below Table I.

TABLE-US-00001 TABLE I Liq T at 7.5 Liq T at 8.5 Mixture bars abs bars abs 6 mol % (CF.sub.3).sub.2CF—CN + CO.sub.2 + −24.1° C. −21.3° C. 0% O.sub.2 6 mol % (CF.sub.3).sub.2CF—CN + CO.sub.2 + −24.6° C. −21.8° C. 5 mol % O.sub.2 6 mol % (CF.sub.3).sub.2CF—CN + CO.sub.2 + −24.8° C. .sup. −22° C. 15 mol % O.sub.2 6 mol % (CF.sub.3).sub.2CF—CN + CO.sub.2 + −26.1° C. −23.4° C. 30 mol % O.sub.2 6 mol % (CF.sub.3).sub.2CF—CN + CO.sub.2 + −28.6° C. −25.9° C. 50 mol % O.sub.2

[0078] The liquefaction temperature of mixtures comprising no oxygen, 5 mol % of oxygen or 15 mol % oxygen does not significantly vary. There is less than 1 degree of difference between the different liquefaction temperatures at a pressure of 7.5 bars (i.e. 7500 hPa) absolute or at a pressure of 8.5 bars (i.e. 8500 hPa) absolute.

[0079] On the contrary, by increasing the mole percentage of oxygen in the mixture to 30% or to 50%, the liquefaction temperature is significantly lowered when compared to the liquefaction temperatures of mixtures comprising no oxygen, 5 mol % of oxygen or 15 mol % oxygen. In particular, the liquefaction temperatures are reduced by more than 4 degrees when the oxygen ratio in the mixture reaches 50 mol % at a pressure of 7.5 bars (i.e. 7500 hPa) absolute and at a pressure of 8.5 bars (i.e. 8500 hPa) absolute.

[0080] This is confirmed when considering the pressure at liquefaction as a function of temperature for gas mixtures comprising CO.sub.2, 6 mol % of (CF.sub.3).sub.2CF—CN and different mole percentages of O.sub.2 (FIG. 2).

[0081] There is an almost complete overlap for the curves obtained for mixtures comprising no oxygen, 5 mol % of oxygen or 15 mol % oxygen while the curves obtained for mixtures comprising 30 mol % of oxygen or 50 mol % oxygen shift to 20 lower temperatures.

BIBLIOGRAPHY

[0082] [1] International application WO 2014/037566 [0083] [2] International application WO 2015/040069 [3] International application WO 2017/114862