Treatment methods for increased transformer oil dielectric loss

There are two methods to solve the problem of excessive dielectric loss in transformer oil: one is to ｒｅｐｌａｃｅ unqualified oil and refill it with oil that has passed electrical tests and chemical analysis and all indicators are qualified; the other is to regenerate the oil that exceeds the standard.

1.ｒｅｐｌａｃｅ unqualified oil. 

Replacing unqualified oil can shorten the system's power outage time. It only needs to drain the old oil in the transformer, flush the transformer with qualified oil, and then vacuum fill the transformer with oil. 

This treatment is more suitable for the unit that cannot be allowed to be shut down for a long time, the unit has been running for a long time, the oil acid value is high, the oil is dark yellow or brown, free water or oil turbidity appears, and it is fully degraded. However, a simple oil change is not as good as "flushing" the transformer with oil filtration, and the oil change is expensive, which is not conducive to energy saving and environmental protection. It is not suitable for oil replacement treatment for oil that exceeds the standard.

2.Regeneration treatment. 

Regeneration treatment refers to the physical-chemical or chemical method to remove harmful substances in the oil and restore or improve the physical and chemical indicators of the oil.

Common methods of regeneration treatment are: the adsorbent method and the sulfuric acid-white clay method. The adsorbent method is suitable for treating oil with a less severe degree of deterioration; the sulfuric acid-kaolin method is suitable for treating oil with a more severe degree of deterioration.

The adsorbent method can be divided into the contact method and the percolation method. 

The contact method uses powdered adsorbents (such as kaolin, 801 adsorbent, etc.) and oil to regenerate under stirring contact; while the percolation method forces the oil to pass through a purifier equipped with granular adsorbents (such as silica gel, granular kaolin, or activated alumina, etc.) for percolation regeneration. 

For transformer oil with more severe deterioration, the sulfuric acid-kaolin method can be used for regeneration. Sulfuric acid treatment can remove a variety of aging products in the oil, and kaolin treatment can eliminate undesirable substances remaining in the oil after acid treatment.

In actual production and operation, it is often encountered that after vacuum, filtration and purification, the water content of the oil is very small, and the dielectric loss factor of the oil is high. This is because the dielectric loss factor of the oil is not only related to the water content, but also to many factors. From the above analysis, it can be found that the reason for the increase in the dielectric loss factor of most transformer oils is the increase in soluble polar substances (such as sol, etc.) in the oil.

For sol particles, their diameter is between 10-gm and 10-Tm, and they can pass through filter paper, so the dielectric loss factor cannot be reduced by the secondary vacuum oil filter. Therefore, to deal with the problem of increased oil dielectric loss factor caused by this reason, the percolation method regeneration treatment can usually achieve good results, such as using a transformer oil regeneration machine equipped with regenerated diatomaceous earth.