Abstract: This study experimentally investigated the arc electrolysis characteristics and gas production behavior in transformers at different temperatures. The explosion process of the electrolysis gas in transformers was also simulated using Computational Fluid Dynamics (CFD). The results indicate that hydrogen constitutes the highest proportion among the gases produced from soybean-based natural ester, recycled oil-based natural ester, and mineral insulating oil. This high hydrogen content is attributed to the combination of H· radicals generated from C-H bond cleavage under high-voltage arc conditions and the electrolysis of water vapor in the air. Based on reaction kinetics simulations, the yield and temperature sensitivity of key free radicals involved in the oxidation of the electrolysis gases were analyzed under critical equivalence ratio conditions, revealing the main conversion pathway: H₂ →·H→·OH (·O) →H₂O. Numerical simulations clearly demonstrate the evolution of the explosion flame in the electrolytic gas mixture and accurately capture the distribution patterns of explosion pressure and flame temperature. The increased turbulence induced by obstacles is identified as the primary cause for the enhancement of flame speed and explosion pressure, reflecting a positive feedback mechanism driven by the coupling of pressure, flame, and turbulence.

Key words: transformer, electrolytic gas production, gas explosion, CFD simulation, reaction kinetics simulation, arc