Transformer oil will cause polarization loss and conductivity loss under the action of alternating electric field. These are collectively referred to as dielectric loss. The dielectric loss factor reflects the quality of transformer insulation characteristics and the aging of transformer oil under the action of electric field, oxidation and high temperature.
Excessive dielectric loss of transformer oil will affect the normal operation of the transformer. At present, there are two main methods to solve the problem of excessive dielectric loss of transformer oil. One is to replace the unqualified oil and re-inject the oil that has passed the electrical test and chemical analysis. It is to regenerate excess oil.
1. Replace the unqualified oil, and re-inject the oil that has passed the electrical test and chemical analysis. Replacing unqualified oil can shorten the power outage time of the system. It is only necessary to drain the old oil in the transformer, flush the transformer with qualified oil, and then perform vacuum oiling on the transformer. This treatment is more suitable for the unit that does not allow long-term power failure; the unit has been running for a long time, the oleic acid value is high, the oil is dark yellow or brown, and free water or oil is turbid and fully degraded. However, simple oil change is not as thorough as filtering oil to "flush" the transformer, and the oil change consumes a lot, which is not conducive to energy saving and environmental protection. It is not suitable to change the oil that exceeds the standard.
2. Regenerate excess oil. Regeneration refers to physical-chemical or chemical methods to remove harmful substances in oil and restore or improve the physical and chemical indicators of oil. Common methods of regeneration are: adsorbent method and sulfuric acid-white clay method. The adsorbent method is suitable for treating oil with a light degree of deterioration; the sulfuric acid-clay method is suitable for treating oil with a heavier degree of deterioration. The adsorbent method can be further divided into contact method and percolation method. The contact method uses powdered adsorbent and oil to regenerate in a stirring contact mode; while the percolation method is to force the oil to pass through a purifier equipped with granular adsorbents. Diafiltration regeneration treatment. For the seriously deteriorated transformer oil, the sulfuric acid-white clay method can be used for regeneration. Sulfuric acid treatment can remove a variety of aging products in the oil, and clay treatment can eliminate the undesirable substances remaining in the oil after acid treatment. In actual production and operation, it is often encountered that after the oil is vacuumed, filtered and purified, the water content of the oil is very small, and the medium loss factor of the oil is high. This is because the medium loss factor of the oil is not only related to the content of the oil The amount of water is also related to many factors. The reason for the increase of the dielectric loss factor of most transformer oils is the increase of soluble polar substances in the oil. For sol particles whose diameter is between 10-gm and 10-Tm, they can pass through filter paper. Therefore, it is impossible to process the medium loss factor of the sol particles by the secondary vacuum oil filter. Therefore, the oil medium loss caused by this reason cannot be treated. The factor increase is usually regenerated by percolation.