THE MOVEMENT OF A CONDUCTING PARTICLE IN TRANSFORMER OIL IN AC FIELDS

This paper proposes a theoretical model to analyze the movement of a small conducting sphere stressed with alternating voltage in transformer oil. The model is verified by comparing it with the experimental observations of a metal particle of radius 0.5 mm in an electrode gap of 8 mm stressed with ac voltage. The model suggests that for practically existing micrometer-sized particles (congruent-to 50 mum diameter), the opposing viscous force is the most significant component. The viscous force is dissipated in the medium as fluid drag both along and perpendicular to the direction of movement. A theoretical analysis of the contribution of multiple particles to viscous drag is presented, and is shown to provide a possible explanation for the experimentally observed particle cloud formation at lower ac stresses and dispersion at higher ac stresses.