Computational estimation of ESD conditions between charged particles and grounded surfaces

The paper examines the conditions in which a discharge occurs between charged spherical particles and grounded surfaces, in air, at atmospheric pressure. The study is of interest to a large group of electrostatic applications which involve the processing of particulate matter: separation of granular mixtures, precipitation of dust, and spraying of powders. At the same time, this simple physical model simulates a class of hazardous situations quite often met in the operation of electronic circuits. The boundary-element method was employed for the computation of the electric field in the gap of length x between a charged conductive spherical particle of radius R and a grounded plate. The data on field distribution represented the input data of an original program which employed Pedersen's criterion for estimating the breakdown conditions of that air-gap. The study was carried out for spheres of various sizes (radii: 0.01-1 mm). Some computations were performed for the case when the grounded plate was covered with an insulating layer of known permittivity. The computational results were in good agreement with the experimental data for both long (x/R>10) and short (x/R<0.1) gaps.