Investigating dielectric failure of A transformer during works testing resulting from inadvertent drying process deficiency

Transformer insulation being hygroscopic always retains some amount of moisture. However, for the reliable service life, the moisture level has to be contained within the permissible level of ≤0.5%. In this context, proper drying of insulation of the active part of the transformer during manufacturing plays a vital role. Any deficiency in processing affects long term reliability of the product. And any major lapses in processing could even lead to test bed failure.