Study on the Influence of Preferred Antioxidants on the Thermal and Oxygen Stability of Quaternary Alcohol Ester Insulation Oil

Synthetic ester insulating oil, with its high ignition point, excellent moisture resistance, ease of biodegradation, good performance, and low maintenance costs, has broad application prospects in power transformers, other electrical equipment, and environments with high environmental requirements. However, the presence of unsaturated <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{C}=\mathrm{C}$</tex> double bonds and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{\beta}-\mathbf{H}$</tex> structures can accelerate oxidation reactions and lead to molecular chain breakage, reducing its oxidation stability. To address these issues, thermal oxidation aging tests were conducted to evaluate the effectiveness of three phenolic antioxidants-T501, TBHQ, and T511-in enhancing the thermal oxidation stability of tetraol ester insulating oil (KA). The experimental results indicate that all three antioxidants effectively inhibit the deterioration of acid value, kinematic viscosity, dielectric loss factor, and volume resistivity of KA insulating oil during the aging process. In terms of oxidation stability, T511 demonstrates the best improvement effect, characterized by a significantly higher initial oxidation temperature.