Why is transformer oil degasification required and how is it performed?

Degasification is required to remove dissolved air and fault gases that reduce dielectric strength and increase partial discharge risk. It is typically performed using a vacuum degassing unit where heated oil is sprayed or thin-filmed under deep vacuum. Gases are released and extracted while oil is recirculated. Degasification is especially important after maintenance, oil filling, or when DGA shows elevated dissolved gas levels.