A New Method for Estimating Transformer Health Index Based on Ultraviolet-Visible Spectroscopy

The condition assessment of power transformers by evaluating the state of their insulating system is of great importance according to the electrical utilities. Since, as early as the insulation deterioration is detected, the probability of a sudden system outage is significantly reduced. Regarding that, there are several methods through which the transformer condition can be determined. Recently, the utilization of optical spectroscopy techniques in condition monitoring based on oil quality analysis has attracted attention in many research papers. Therefore, the contribution of this paper is to check the reliability of estimating the transformer's Health index (HI) percentage based on the optical spectroscopy techniques. So, pure mineral oil samples were thermally aged in the laboratory for various ageing durations. Then, all of them were examined by ultraviolet-visible (UV-Vis) spectroscopy for determining the dissolved decay products (DDP) in each sample. After that, the HI percentages were estimated for the transformers simulated by these aged samples according to their DDP values. In the final analysis, this optical method has proven its potential in being a superior alternative to conventional techniques in estimating the transformer's HI percentage.