Effect mechanism of dielectric-coated electrodes on metal particle lift-off in SF6 gas

In order to study the influence mechanism of dielectrically coated electrode in SF6 gas under DC electric field on metal particle lift-off, experimental platform is setup and motion trajectory is recorded by high-speed camera. The experiment shows that with the increasing of SF6 gas pressures, the lift-off field of metal particle is increased and the time to reach the high-voltage electrode shortened. Instantaneous displacement of metal particle is gained by image processing and computational method of charge quantity is raised, analysing of charge quantity shows that the metal particle's charge quantity decreases. Meanwhile, theoretical analysis model of field distribution around metal particle is established, result indicates that there is an enhance of electric field between coating and metal particle and a transform of charge density distribution, which leads to a downward polarisation force for metal particle. The decreasing of the electric charge quantity and the downward polarisation force results in the increasing of the lift-off field. This article maintains that partial discharge is the charging mechanism of metal particle; the enlargement of SF6 gas pressure brings about the raise of initial electric field of partial discharge, causing the increase of downward polarisation force with higher electric field to lift-off.