Particulate contamination and stress induced motion in transformer oil

An experimental investigation of electric field induced motion in transformer oil is reported. The oil was subjected to a voltage step giving fields of up to 5 MV /m. The observations are explained in terms of a model based on behavior of particles both at the oil/electrode interface and in the bulk of the oil. The results indicate that charged particles with diameters less than one micro-meter, rather than ions, are the source of stress induced motion in transformer oil.