Effect of Suspended Particles on Streamer Branching in Transformer Oil

In order to explain the modified streamer pattern in nano-modified transformer oil, the polarization effects of suspended particles on the electrodynamics of streamer branching were studied. A multi-physical coupling numerical model of streamer propagation in transformer oil was presented based on the Poisson theory, continuity equations of charge carriers and field-depended molecule ionization. Considering the particle polarization under strong electric field, suspended particles with varying permittivities were studied. The results showed that the polarization of particle distorts electric field and enhances the local electric field strength surrounding the particle. As soon as the local electric field is intensive to produce sufficient ionization, a new streamer would be induced at the pole of the particle to form a side-branch. Besides, the patterns and characteristics of streamer branches highly depend on the permittivity of particle.