Effectiveness of admixturing treatment of aged transformer oils

The effectiveness of admixturing treatment is considered in the macroscopic formulation. This maintenance activity consists of the insertion of a small amount of suitable organic acid (not more than 0.1% by weight) to partially aged transformer oil in due time. The admixturing effects are evaluated by means of tanδ measurements made for oils in service. The effectiveness of the admixturing treatment depends on the electrical parameters of power transformers and seems to be especially satisfactory for MV transformer units. From field investigations it appears that tanδ mean values of admixtured oils may decrease temporarily by several times and the long-term admixturing effects are justified by the substantial prolongation of the operating time of certain transformer units