Abstract
We have developed a novel diagnosis of oil filled middle-sized power transformers by optical analysis. The color of insulating oil gradually turns to yellowish in the long term use. The coloring is caused by the increase of electronic transition absorption due to thermal oxidation of insulating oil.
We derived a relationship between the aging degree of deteriorated oil and the optical absorption loss. The aging degree of deteriorated insulating oil can be estimated using the diagnostic master curve, which is obtained with an accelerated heating experiment. Furthermore, the optical absorption loss was correlated with the average value of polymerization degree of the insulating paper. Therefore, this optical technique is theoretically applicable to diagnosis for power transformers.
