Modern transformers have several requirements because of greater electrical stress in fluids and insulating materials. For such requirements we have to maintain lower residual water content and better dielectric strength of oil to handle those stresses. We have to treat insulating fluids from time to time in a proper way. Transformer oil filtration services will improve the properties of entire system of transformers. Insulating fluids are used in transformers as effective coolants and also as a dielectric material. Different functions are performed with transformer oils like to suppress corona, for insulation process and also for arcing.