Influence of Various Temperatures on the Drying Time of 220/66 KV Transformer Insulations in Vapour Phase Drying Process

Abstract

Cellulose based insulation in the form of different papers and pressboard play a vital role in transformer manufacturing as very high level of voltages are encountered during transformer operation. Cellulose being hygroscopic in nature contains 8-10% moisture by weight. The life of a transformer is critically dependant on the state of cellulose insulation so much so that, paper with 1.5% moisture content ages 10 times faster than with only 0.3% moisture. For obvious reasons, it is very important that the moisture is removed from transformer insulation. As of today, the latest technology available for this moisture extraction is the vapour phase drying process. This paper evaluates the influence of temperatures at various locations on the drying time of two 220kv transformer insulations in vapour phase drying process.