Motion characteristics and distribution of metal particles in insulating oil under DC voltage

Abstract

Studying the dynamic behavior of metal particles in insulating oil in case of flow-electric field coupling is important to fully understand the insulation mechanism in transformers, such as partial discharge and insulation deterioration of contaminated insulating oil. In this paper, through experiments, the particle image velocimetry (PIV) technique is applied to study the motion of metal particles in the oil flow under direct current (DC) electric field. According to the observation results of flow field, the effects of voltage level, electric field non-uniformity, and oil flow velocity on the motion and distribution of particles are analyzed in detail. The obtained results show that the applied voltage has an obvious effect on the motion of metal particles in oil flow, and it causes the formation of wavy trajectories of particles, where such effect becomes more obvious as the voltage level increases. Moreover, it is observed that the increase of flow velocity can weaken the influence of electric field, and the electric field non-uniformity affects the trajectory of particles mainly by changing their velocity component in the vertical direction. In addition, the concentration of particles group in the oil flow is sensitive to the external electric field, where the concentration decreases with the increasing electric field. Certainly, the results reported herein are effective in further revealing the effect of impurity particles on the insulating oil.