How does a transformer oil dehydrator remove moisture and dissolved gases?

The most common method is vacuum dehydration and degassing. The dehydrator heats the oil, then exposes it to a low pressure environment where dissolved moisture and gases boil off at much lower temperatures than at atmospheric pressure. The system removes the vapors through condensers or vacuum pumps, while filters remove particles. Multi stage designs improve gas stripping and achieve very low moisture ppm. The outcome is increased BDV, lower dielectric losses, reduced bubble risk, and improved thermal performance, especially after maintenance or when moisture ingress has occurred.