Benefits of dry Air Filling in Transformer?

Dry air must be used to ventilate the inside of the tank when it is opened for internal fitting. The air must have a dew point less than -40°C and sufficient airflow for the number of operators in the tank must be maintained.

Do never use nitrogen or other gases than air for ventilation

When opening the transformer tank, care must be taken to prevent moisture or dirt entering the transformer or moisture condensing in the transformer. If wet air enters the transformer, it may be cooled by the tank wall below its dew point and condensed, so it will reduce dielectric strength of the transformer

Dry air should be supplied through hand hole during working or inspection. Care especially must be taken not to drop tools or foreign substances. It is recommended that tools used in the tank be tied to worker with a cord. When the work in the tank is completed, the inside of the tank should be inspected. For inside cleaning, the dry, clean and lint-free cloths should be used.