The movement of a conducting particle in transformer oil in AC fields

A theoretical model is proposed and used 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 (≃50 μm 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