People who want to prevent arcing flood the cavity with sulfur hexafluoride. Fun fact, it has 25,000 times the "greenhouse potential" of CO2. Dunno if that includes lifetime in the atmosphere, or just instantaneous opacity to IR. All the wind turbines are pumped full of it. There is an effort on to switch to something else of proprietary composition.
"Data from Vattenfall suggests leakage emissions from Europe’s 100,000 wind turbines were about 900kg of SF6 over the last six years. This is equivalent to 3,525 tonnes of CO2 a year. This includes the release of gases during the reclamation and recycling process. At end-of-life the turbine switchgears are collected and the sulphur hexafluoride gas is reclaimed and reused in new equipment.
By comparison wind energy avoids the emission of 255 million tonnes of CO2 in Europe a year by generating 336TWh of electricity displacing fossil fuels. The SF6 leakage therefore represents around 0.001% of the emissions avoided thanks to wind energy every year."
That is only true to a certain point. Look up Paschen's law. After you go lower than a certain point, around 10 Torr cm depending on the gas, decreasing pressure increases the breakdown voltage.
It's probably not feasible to pump to such low pressures in wind turbines, so they probably don't even try. But for NIF, it's common.
