Method for re-establishing an electrical apparatus of medium or high voltage

1. A method for re-establishing an electrical apparatus of medium or high voltage, the method comprising the steps of:

a) providing an electrical apparatus designed for using an insulation medium containing SF6,

b) removing at least partially the SF6-containing insulation medium from an insulation space contained in the apparatus, and

c) filling an alternative insulation medium into the insulation space,

wherein the alternative insulation medium is a mixture of at least one organofluorine compound A and a carrier gas containing nitrogen and carbon dioxide, and the amount of carbon dioxide in the alternative insulation medium is lower than the amount of nitrogen.

2. The method according to claim 1 , wherein the organofluorine compound A comprises a fluoroether.

3. The method according to claim 1 , wherein the alternative insulation medium contains heptafluoroisobutyronitrile as the organofluorine compound A.

4. The method according to claim 1 , wherein after step c), the partial pressure of the organofluorine compound A is at least 5 kPa.

5. The method according to claim 1 , wherein the carrier gas amounts to more than 60% of the total gas pressure of the alternative insulation medium.

6. The method according to claim 1 , wherein the molar percentage of nitrogen in the alternative insulation medium is higher than 50%.

7. The method according to claim 1 , wherein the carrier gas further contains an oxidizing gas.

8. The method according to claim 7 , wherein the molar percentage of oxidizing gas in the alternative insulation medium is in a range from 1 to 25%.

9. The method according to claim 1 , wherein the molar percentage of carbon dioxide in the alternative insulation n medium is lower than 5%.

10. The method according to claim 1 , wherein the molar percentage of the organofluorine compound A contained in the alternative insulation medium is from 0.5% to 35%.

11. The method according to claim 1 , wherein the insulation space is sealed by a sealing component comprising a sealing material selected from the group consisting of EPDM rubber, nitrile rubber and butyl rubber.

12. The method according to claim 1 , wherein the method comprises the further step of installing a gas density monitor designed for monitoring the density of the alternative insulation medium.

13. The method according to claim 12 , wherein the step of installing the gas density monitor is carried out after step b) and before step c).

14. The method according to claim 13 , wherein after installing the gas density monitor and before step c) the insulation space is at least partially evacuated.

15. The method according to claim 13 , wherein after step b) and before installing the gas density monitor at least a part of one or more adsorbers, absorbers and/or gas filling valves contained in the insulation space are replaced.

16. The method according to claim 12 , wherein the step of installing the gas density monitor is carried out during operation of the apparatus by means of a check valve.

17. An electrical apparatus of medium or high voltage re-established by the method according to claim 1 .

18. An electrical apparatus according to claim 17 , wherein the insulating space containing the alternative insulation medium is sealed with a sealing component comprising a sealing material selected from the group consisting of EPDM rubber, nitrile rubber and butyl rubber.

19. An electrical apparatus according to claim 17 , wherein the apparatus is a switchgear, or a part and/or a component thereof, a gas-insulated line (GIL), a busbar or a bushing.

20. An electrical apparatus according to claim 17 , wherein the apparatus is a cable, a gas-insulated cable, a cable joint, a current transformer, a voltage transformer, a sensor, a humidity sensor, a surge arrester, a capacitor, an inductance, a resistor, an insulator, an air-insulated insulator, a gas-insulated metal-encapsulated insulator, a current limiter, a high voltage switch, an earthing switch, a disconnector, a combined disconnector and earthing switch, a load-break switch, a circuit breaker, a gas circuit breaker, a generator circuit breaker, a gas-insulated vacuum circuit breaker, a medium voltage switch, a ring main unit, a recloser, a sectionalizer, a 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.