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What Is Electric Transformer Oil Oxidation

What Is Electric Transformer Oil Oxidation

Insulating oil is widely applied in electric equipment, such as power transformer, circuit breaker, and other oil-filled equipment.

During the use, storage and transportation of electric transformer oil, it will inevitably come into contact with oxygen in the air. Under certain conditions, the direct contact between oil and oxygen will cause a chemical reaction to produce some new oxidation products. These oxides in the oil will aggravate the oil deterioration. This chemical reaction between oil and oxygen is called oil oxidation (or oil aging or oil deterioration). The oil's ability to resist oxidation is called its anti-oxidation stability (or oil stability).

Since electric transformer oil is composed of a mixture of many hydrocarbons with different structures, its oil oxidation process is very complicated, but it can be roughly divided into three stages:

1) The initial stage is the so-called "induction period", which occurs when the temperature of the new oil is not high. In this stage, the oil absorbs a small amount of oxygen, oxidizes very slowly, and generates very few oxidation products, because the oil contains natural antioxidants to prevent its oxidation. However, if the temperature rises (and under the influence of the catalyst), the induction period will be quickly shorten, as shown in the following table.

The Relationship between the Induction Period and the Temperature







Induction Periodh






2) Development Period. After the induction period, stable oxidation products are gradually formed in the oil, such as organic acids, water and certain oxides, all of which have low molecular weights. The oxidation process is constantly going on, and the chain reaction is intensified. The initial oxidation products are soluble in oil and water, and have a strong corrosive effect. Continue to oxidize to produce solid polymerization and condensation products. When they reach saturation in the oil, they will precipitate out of the oil, which is the oil sludge sediment.

3) Hysteresis Period. At this time, the oxidation reaction of oil is hindered to a certain extent, because some phenolic oxides generated by resin oxidation begin to act as a negative catalyst to prevent the oxidation process. In this stage, the oxidation rate slows down, and the oxidation products are also reduced compared to the previous stage.

In order to maintain the insulating properties of electric transformer oil, the oxides, oil sludge, water,acids and other oxidation products must be removed. By using the Transformer Oil Regeneration machine developed by PureTech, you can effectively perform the following functions:

a) Vacuum Drying of electric transformer oil

b) Precision Filtration of electric transformer oil

c) Regeneration(re-refining) of electric transformer oil

Contact us for more details.