The interturn paper insulation of oil-immersed power transformer windings

under the combined influence of electric fields

moisture

and conductor heating

will produce bubbles

which pose a significant threat to the insulation system. However

there is limited research on the characteristics of bubble evolution in oil–paper insulation under the influence of electric fields and the subsequent dissolution process. Based on the continuous observation of bubble size using electron microscopes

experimental and theoretical investigations into the formation and dissolution of bubbles under electric field conditions are presented. The effects of different field strengths on bubble evolution and dissolution characteristics were studied. The results showed that the electric field promoted both the generation and dissolution of bubbles

with a more pronounced effect observed at higher field strengths (below partial discharge (PD) inception electric field

hereafter referred to as PDIE). However

when the field strength exceeded PDIE

the bubbles tended to shrink and gradually increase in size. The changes in bubble volume were related to not only gas diffusion but also oxygen consumption and fault gases generation due to PD. A better understanding of the formation and dissolution characteristics of bubbles under varying field strengths is achieved. Furthermore

it also provides a reference for assessing the risk of bubble generation and conducting bubble-related fault diagnosis during the overload operation of oil-immersed power equipment.