Patent ID: 7468091

Claim:
Method of air dehumidification for oil-filled transformers, reactance coils and step switches for dehumidification of the air inducted into an oil expansion vessel, wherein the air humidity F r is measured in the area between a granulate-filled housing of an air dehumidifier and the oil expansion vessel connected therewith, and wherein subsequently a comparison of the measured air humidity F r with a predetermined limit value F max is undertaken and if the limit value is exceeded an electric heating device for baking the moisture-absorbing granulate in the interior of the housing is activated, characterised in that it is additionally detected whether an air flow is present between the housing ( 5 ) and the oil expansion vessel and if so which flow direction this air flow has and that the electric heating device is switched on only if either no air flow is present or this is directed outwardly from the oil expansion vessel.