Effects of trap characteristics on streamer propagation in dielectric liquid

Due to physical and chemical complexity, the mechanism for breakdown process of dielectric liquids is not clear. In this paper, electric field dependent molecular ionization was used to model the positive streamer in transformer oil. The relationship between electron hopping transition mobility and trap characteristic was analyzed. And the influence of trap characteristics on the propagating streamers was thereafter studied. Stimulation results present a negative correlation between the streamer propagation velocity and the density as well as the depth of trap in transformer oil. It indicates that electrons diffuse their energy by trapping and de-trapping process. With lower kinetic energy, those electrons turn into negative charge clusters more easily, which weaken the electric field magnitude in front of the propagating streamer. As a consequence, the propagating velocity of positive streamer is reduced.