Gas Generation Characteristics by Partial Discharge in Rapeseed-Oil and Soybean-Oil Based Natural Ester Liquids

Natural esters have different chemical composition compared to mineral oil, so that the gas species and concentrations generated under faults in natural-ester-immersed transformers may differ from those generated in mineral-oil-immersed transformers, affecting the interpretation of dissolved-gas-analysis (DGA) results. In this study, experiments simulating a partial discharge (PD) fault in transformers are conducted to obtain the DGA characteristics of natural esters. The experimental results show that H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>, C<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>, and CO are commonly generated from natural esters under PD. However, the concentration of C2H2 generated from natural esters is lower than that for mineral oil at a similar average PD magnitude. This result may affect the development of the DGA criteria for detection of PD faults in natural-ester-immersed transformers.