Impact of thermal aging of transformer oil on UV-Vis optical spectrum and dielectric properties

Abstract

Aged transformer oil can be evaluated by conventional tests to assess the degradation in electrical, chemical and physical properties. However, proper evaluation requires expensive equipment, expertise and time for sampling and testing. UV-Vis spectroscopy is a nondestructive technique that can be conducted on-line with a lower cost and a simple manner. This study aims to investigate the impact of thermal aging on the UV-Vis spectra and the dielectric properties of aged transformer oil in order to correlate between them for the sake of condition assessment of aged transformer oil using UV-Vis spectroscopy. In this regard, oil samples were thermally degraded by accelerated aging experiment in laboratory. Then, these samples were tested for breakdown voltage and dielectric dissipation factor. Also, water content was measured due to its influence on the dielectric properties. In addition, the samples were tested using UV-Vis spectrophotometer to obtain UV-Vis spectra and decomposition by-products. The results were investigated considering the effect of aging duration and correlating the decomposition by-products with dielectric properties. The results indicate that UV-Vis spectra can reflect the degradation in aged transformer oil.