Bridging in contaminated transformer oil under AC, DC and DC biased AC electric field

Cellulose particle accumulation under AC, DC and DC biased AC electric field in transformer oil has been investigated in this paper. Different levels of particle concentrations tested with spherical electrode system. Optical microscopic images and conduction current of the particle accumulation process have been recorded during the experiments. A complete bridge of cellulose particles only observed under DC and DC biased AC electric field.