What steps are involved in oil filtration of transformer procedure?

Oil filtration typically involves heating oil to reduce viscosity, applying vacuum dehydration to remove moisture, degassing to extract dissolved gases, and passing oil through fine particulate filters. The process may be performed online or offline depending on transformer condition. Pre and post filtration testing verifies improvement in moisture content, dielectric strength, and cleanliness. Proper grounding, sealed connections, and controlled temperature are critical to avoid introducing air or contaminants during filtration.