Lifting force on metallic particles in gis systems

Dielectric coatings have shown to reduce the activity of metallic particles in GIS systems and thus hinder the development of particle initiated electrical breakdown. In this report we present an experimental method to investigate the charge exchange between metallic particles and the coating and the conditions for particle lift off. A few experimental results are also presented. The system comprises a balance mechanism with which the force needed to lift the particle from the coating can be measured as a function of an applied electric field. An electronic servo system makes it possible to keep the particle on a given distance from the coating and at the same time determine the force needed to keep the particle in place. The report also contains suggestions of investigations that can be carried out with the device to clarify the desired properties of an optimal coating to suppress particle initiated electric breakdown