This oil purification plant is used for overhauling and installing the electric insulating equipments which are running as energized, such as transformer, oil switch and mutual inductor. Also it is especially applied to regenerate and purify the seriously deteriorated insulation oil and make the oil reach the international standard. The functions include dewatering, degassing, decolor, removing the impurities, free carbon and deep oxides, and recovering the oil's original function.