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

Degasification removes dissolved air and fault gases that reduce dielectric strength and can promote partial discharge. It is performed using vacuum degassing units where oil is heated and exposed to low pressure, allowing gases to escape. In severe cases, oil is processed in multiple passes, and the transformer may be vacuum dried and filled to remove trapped gas in paper and structures. Degasification is important after maintenance, oil replacement, or when DGA and dielectric loss suggest excessive gas content.