A Phase Field Model for Bubble Dynamics in Dielectric Liquid

Transformers under operating conditions will generate bubbles under the effect of high temperature and moisture. Existing research and engineering applications have shown that bubbles are a typical defect of oil-paper insulation systems, and may induce partial discharge or even breakdown. In this paper, a multi-physics simulation model coupled with electric field, flow field and phase field was established to study the dynamic behavior of bubbles under the action of electric field and its effect on the internal discharge characteristics of bubbles. The results showed that under the action of the electric field, bubbles elongate along the direction of the electric field. The deformation increases with the increase of the electric field strength, the bubble radius and the dielectric constant of the oil, and can be expressed as a function related only to the dimensionless electrical bond number ( BoE). In addition, the discussion results showed that the bubble deformation has a significant effect on the partial discharge characteristics inside the bubble. The research results in this paper can provide a reference for further study of the mechanism of bubble discharge, assessment of the damage of bubbles to liquid insulation systems and establishment of effective detection methods.