Dehydration: The process of removing the moisture (water content) from the body. Dehydration is one of the methods to improve the efficiency of Transformer. In Dehydration process Transformers is dried up so that the moisture and sludge could be removed out from winding. Filtration: Filtration is the process in which the oil being filtered with the help of High Vacuum Filtration Machine. Filtration helps out to eliminate the solid elements of oil. Both of the above methods are being use to remove the Moisture, Sludge, Acidity and mainly to improve the BDV and Resistivity of Transformer’s oil. After Dehydration and Filtration of Oil the BDV of Oil should be around 60 KV.