Unpredictable explosions in ultra-high-voltage transmission systems pose a significant threat to the stability of power grids. This study

for the first time

employs a drop-weight impact testing apparatus to indirectly assess the impact resistance of key lap weld structures in oil tanks with varying weld leg heights under dynamic impact conditions. The experimental results indicate a positive correlation between the weld leg height of the lap joint and the failure energy. Specifically

the initiation failure energy of the lap weld with a 30 mm weld leg height ranges from 67.6 to 79.0 J per unit length

and the total failure energy ranges from 79.0 to 89.1 J

significantly higher than those of lap welds with 18 mm and 24 mm weld leg heights. Additionally

the study modifies the empirical formula for the ultimate load of the lap joint based on the strain rate term of the Johnson-Cook constitutive model. The error of the modified formula

when compared with the Kamtekar theory

does not exceed 2 %

demonstrating its capability to predict the ultimate strength of the welds under dynamic impact conditions with high accuracy. Finally

a detailed analysis of the deformation and failure mechanisms of the lap welds under dynamic impact is conducted through micro-structural observation. The findings provide valuable theoretical insights and technical references for the structural design and impact resistance optimization of ultra-high voltage transformers.