Numerical Simulation of Two-Phase Gas Generation and Propagation in Transformer Oil Under Arc Faults

In high-energy arc fault-induced transformer explosions, the rapid generation and expansion of gas in insulating oil is a key driver of the sudden internal pressure surge. To investigate the influence of gas yield on pressure response, this study develops a VOF-based thermo-fluid coupling model governed by the three fundamental conservation equations. A thermodynamic approach combined with arc zoning theory is employed to model arc-induced oil decomposition, based on which the composition and yield of decomposition gases at different energy levels are calculated. These results are introduced as mass source terms to enable equivalent fault source loading. Taking the on-load tap-changer (OLTC) compartment as a representative case, simulation results reveal that gas yield has a significant impact on internal tank pressure, exhibiting an approximately linear relationship. This work provides an effective numerical frame-work for pressure prediction and explosion-proof design of transformers under arc fault conditions.