What precautions are required during oil filling in transformers?

Key precautions include keeping oil dry and clean, preventing air ingress, and avoiding contamination from hoses, drums, or containers. Use clean dedicated transfer equipment, filter the oil through fine filtration and dehydration if required, and maintain vacuum filling or nitrogen blanket practices as specified by the manufacturer. Ensure grounding and bonding to reduce static, confirm correct oil type and inhibition status, and monitor temperature, moisture, and level. After filling, verify seals, sample oil for baseline tests, and check for leaks.