Transformer oil in operation is often at high temperature (85 ℃ or so), and the atmosphere will occur oxidation. The oil in the presence of certain substances (such as copper, etc.) will accelerate the oxidation process. Oil oxidation, the continued decomposition of acid, ash and other impurities, so that the performance of oil degradation. When the oil reaches a certain concentration of impurities, will produce sludge deposition, sludge accumulation in the windings, iron core and heat pipe, the impact of transformer heat. In addition, the transformer oil will absorb moisture from the atmosphere. In the above-mentioned factors, the transformer oil quality will gradually deteriorate (ie, aging), the insulation strength is gradually reduced, so that transformer oil aging deterioration.