High-energy Arc Gas Generation Characteristics of Transformer Bushing

This study establishes an LC resonant dischargebased power-frequency arc test platform for transformer bushings, employing a rod-rod electrode model to simulate high-energy arc faults in capacitive bushings environment. Systematic experiments investigate the influence of arc current amplitude ($\mathbf{2} \mathbf{- 6 ~ k A}$) and arc length ($5-25 \mathrm{~mm}$) on insulating oil pyrolysis gas generation. The key findings reveal that gas production per unit energy exhibits negligible correlation with current amplitude under fixed arc length (15 mm), increasing by less than 5% when the current rises from 2 kA to 6 kA. However, when maintaining the arc current at 4 kA and extending the arc gap from 5 mm to 25 mm, the deposited arc energy increases from 3.97 kJ to 17.12 kJ, and gas production per unit energy rises from $0.064 \mathrm{~L} / \mathrm{kJ}$ to $0.068 \mathrm{~L} / \mathrm{kJ}$. Due to the increased contact area between the arc and oil, thermal decomposition is en hanced, allowing arc length to dominantly govern gas generation and pressure characteristics. Thereby, more energy is converted into pressure wave energy, significantly elevating pressure peaks. Therefore, for the internal design of transformer bushings, protrusions and extended gaps should be structurally avoided. Explosion-proof design must prioritize monitoring the pressure peak during the first half-cycle of arcing initiation to prevent catastrophic failure escalation, thereby reducing the risk of widespread damage following arc faults.