Arc discharge in transformer oil can lead to localized high temperatures and rapid and violent gas generation. This paper presents three electrode shapes which are designed on the basis of the typical insulation structure and characteristics of transformers

namely

plate-plate

ball-ball

and tip-plate. A high-speed camera is employed to capture the arc discharge process in insulating oil and the corresponding changes in gas cluster morphology. The position of the arc channel is observed to follow the movement of the gas cluster

shifting when the arc is reignited after extinguishing under the ball-ball and tip-plate electrodes. By constructing a two-phase flow heat transfer model that incorporates phase change reactions

the shape and evolution of the gas cluster in the simulation results align closely with the captured images. The gas cluster often exhibits ellipsoidal deformation due to surface tension

and its low density causes it to rise under buoyancy

resulting in the upward movement of the high-temperature zone and arc channel. Electric field results indicate that the arc initiates in regions of high electric field strength

with the shape of the arc channel corresponding to the direction of the electric field lines. Although the gas cluster distorts the electric field to some extent

its effect remains relatively minor. When the gas cluster exits from the high electric field area

the position of the arc channel reigniting after extinguishing shifts back to the initial high electric field region

which is consistent with the recorded images. The methods and findings of this research provide a theoretical and practical foundation for enhancing the understanding of the gas generation mechanism and developing fault protection strategies for arcs in oil.