BZ series utilizes physiochemical means to recover deteriorated transformer oil and breaker oil through removing the acid content, suspended matter and precipitated residues from the oil. It utilizes a special purification device, which allows transformer to stay running in normal manner without switching off of power and changeing of oil. The basic content and anti-oxygenic property of oil remain the same after treatment, and are brought back to the specification of new oil; Insulator property and safety of equipment are enhanced.