① Insulation transformer oil is transformed.

Both its physical and chemical functions are involved, and then its electrical functions deteriorate. After testing the insulation oil's acid value, interfacial tension, water-soluble acid value, etc., it can be judged whether it is due to this type of disadvantage. Regeneration treatment of the insulation oil may eliminate the oil-degraded products, but the processing process May also remove natural antioxidants.

② Insulation oil gets wet with water because water is a highly polar substance.

Under the effect of the electric field, it is easy to ionize and differentiate, and the electric conductive current of the insulating oil is added. Therefore, a small amount of moisture can significantly increase the dielectric loss of the insulating oil. After testing the micro-water of the insulating oil, it is judged whether it is due to this type of disadvantage. Pressure vacuum filtration of insulating oil usually eliminates moisture.

③ Insulating oil infects microbial bacteria.

For example, in the main transformer device or hanging core, insects attached to the exterior of the insulator and the latches left by the device personnel: stains and so on may carry bacteria and then infect the insulating oil: maybe the insulating oil itself has infected microorganisms. The main transformer operates under the environment of 40-80 ℃ which is very conducive to the growth and reproduction of these microorganisms. Because the insulation function of minerals and proteins in microorganisms and their excreta is far lower than that of insulating oil, and then the insulating oil is added through the dielectric loss. This kind of disadvantage is difficult to deal with the method of on-site recycling treatment, because no matter how it is treated, a part of the microorganisms remain on the insulating solid. After the treatment, the insulation of the main transformer will recover in a short period of time, but because the operating environment of the main transformer is very conducive to the growth and reproduction of microorganisms, these residual microorganisms will grow and reproduce year by year, and then the insulation of some main transformers will decrease year by year.

④ Alkyd resin insulation paints rich in polar substances are dissolved in oil.

Under the effect of the electric field, polar substances will undergo dipole lax polarization and energy will be consumed in the process of communication polarization.  The dielectric loss of the transformer oil will increase. Although the insulation paint is cured before leaving the factory, it may still be incompletely treated. After the main transformer has been running for a while, the incompletely treated insulating varnish is gradually dissolved in the oil which gradually reduces its insulation function. The moment when this type of defect occurs is related to the completeness of the insulation paint treatment and a certain effect can be obtained after one or two adsorption treatments.

⑤ Only water and impurities are mixed in the oil.

This pollution does not alter the fundamental nature of the transformer oil. Moisture can be removed by boring method. Impurities can be removed by filtration, air in oil can be removed by vacuuming.

⑥ Two or more types of insulation from different origins are used in combination.

The properties of the oil should meet the relevant requirements, the oil has the same specific gravity, the same condensation temperature, the same viscosity and near the flash point; and the stability of the oil after mixing also meets the request. Regarding the oil that deteriorates after being mixed with oil, because the transformer oil quality has changed and acidic substances and oil sludge have occurred, it is necessary to use chemical methods to regenerate the degraded goods to recover their properties.