How cellulose particles influence streamer propagation and branching in transformer oil: a 2D modelling perspective

Abstract

The streamer discharges and electric breakdown in insulating liquid like transformer oil are undesirable for power equipment. However, the physical processes of streamer propagation and branching events in dense liquid dielectrics are not well understood. In this paper, we develop an improved fluid model to investigate the interactions of cellulose particles with streamer propagation and branching behaviors. We elaborately select the number of cellulose particles (single or multiple particles), their size and locations to elucidate the influencing mechanisms. The simulation results show that when the heads of streamer contact with the surface of the cellulose particle, the local electric field increases sharply, hence the rise of ionization rate and velocity. The scattering electric field lines guide the streamer head away from the surface, thereby causing branching to occur. The interactions between the two split streamers allow one head to continuously propagate, while the other dies out due to insufficient ionization rate. When the particle is too small or too far away to the streamer channel, it has no pronounced impact on the streamer propagation. While placing the particle very close to or on the route of discharge channel will cause the streamer to creep on the cellulose particle and to branch more.