transformers core acids byproducts crucial role removing contaminants separate contaminants removes contaminants efficient operation force oil filter presses oil temperature costeffective alternative involves passing original properties oil restoring oxygen leading contamination accumulation degrade due protective agent insulator coolant filtration equipment specialized equipment dissolved gases timely filtration centrifugal force remove moisture large particles insulation reducing distribution transformer oil filtration transformer oil filtration insulation failure sludge specialized filters degasification optimal transformer operation particles oxidation reaction transformer oil plays gases centrifugal separators preventing costly failures steps prefiltration removal filtration key indicators dust dirt moisture vital maintenance practice strainers heating increasing