Investigating High Intensity Thermal Faults in Ester-Based Transformer Oil: A Dissolved Gas Analysis Approach

Dissolved Gas Analysis (DGA) is a significant diagnostic tool for assessing transformer conditions, especially for detecting thermal faults. These faults, stemming from heightened thermal and electrical stresses on liquid insulation and cellulosic materials, generate various gases dissolved in oil. With the rise of environmental concerns, ester-based liquid insulation, like natural and synthetic esters, is an alternative to Mineral Oil (MO) in transformers. However, interpreting DGA data for ester-based oils requires an understanding of the distinct fault gas profiles they exhibit. In the current study, high intensity thermal faults were generated and analyzed by DGA in three different types of transformer oils: MO, natural ester, and synthetic ester, utilizing a novel method of inducing/which induces high intensity thermal stress. The results revealed differences in fault gas generation and concentrations among the three oil types, highlighting the importance of tailored interpretation methods. Since standard DGA interpretation methods are not available for ester filled transformers, these results were validated using established DGA interpretation techniques of MOs. While traditional methods may not fully capture fault conditions in natural and synthetic esters, the present study proposes Duval Triangles and Pentagons for accurate interpretation, shedding light on fault types and their implications for transformer health. The critical role of DGA in assessing transformer health is underscored, particularly in the context of evolving insulation technologies towards a greener future.