How does the oil in oil-immersed power transformers clean itself?

The self-cleaning mechanism of transformer oil is typically achieved through the following methods:

1. Oil Purifier Filtration
   Oil purifiers are common purification devices in transformers, filled with adsorbents such as silica gel or activated alumina. During transformer operation, convection caused by oil temperature changes drives the oil to flow downward through the purifier. Moisture, acidic substances, and oxidation byproducts in the oil are absorbed by the adsorbent, thereby maintaining oil cleanliness and extending its service life.

2. Oil Circulation Purification System
   Some modern transformers are equipped with oil circulation purification systems. For example, Suzhou Boyuan Special Transformer Co., Ltd. has developed a self-circulating oil-forced air-cooled high-efficiency power transformer that uses an oil pump to draw oil from the main tank and deliver it to a purification chamber. Inside the chamber, a W-shaped microporous filter screen and activated carbon plates provide dual-stage filtration for deep oil purification.

3. Function of the Breather (Dehydrating Breather)
   The transformer breather (also called a dehydrating breather) adsorbs moisture and impurities from the air entering the conservator tank. As the oil temperature fluctuates, air is expelled from or drawn into the conservator through the breather. The desiccant inside (e.g., silica gel) absorbs moisture from the incoming air, preventing humidity from entering the conservator and thus indirectly preserving the insulating properties of the transformer oil.

4. Automatic Cleaning Devices
   Some transformers are also equipped with automatic cleaning devices. For instance, a certain type of oil-immersed transformer with automatic cleaning functionality uses electric sliding rails and cleaning brushes to wipe the transformer’s outer casing, while high-pressure nozzles flush the inner walls of the oil reservoir to remove residual oil stains.

5. Vacuum Dehydration and Degassing
   In some advanced transformer oil purification systems, the oil is atomized or formed into a thin film inside a vacuum separator, allowing moisture and gases to be separated. The moisture is then collected via a cooling and condensation system, and the gases are vented out, achieving effective oil purification.

These mechanisms can be used individually or in combination to enable self-cleaning and purification of transformer oil, thereby improving transformer operational efficiency and extending its service life.