Effect of the dielectric barrier on discharges in non-uniform electric fields

Abstract

This paper is aimed at calculating the electric field in the point-to-plane electrode system with the plate covered with a dielectric layer. With charge accumulation on the dielectric surface by corona discharge, the field in the dielectric is increased at the expense of a decrease in the gas gap. The charge accumulation on the dielectric surface proceeds to the maximum possible value when the normal component of the surface field vanishes. With the dielectric layer fully-charged, the percentage decrease of the field in the gas gap is maximum at the dielectric surface and declines along the gap axis to vanish at the point tip. The percentage decrease of the field becomes more pronounced with the increase of the diameter of the dielectric layer. The effect of inter-electrode spacing and the dielectric layer thickness on the field distribution is investigated. An accurate method of charge simulation was used for field calculation irrespective of the thickness of the dielectric layer and the gap geometry. With ion flow along the flux lines from the stressed point to the ground plane, the field enhancement factor increases and the volume charge density decreases along the flux lines. The voltages of the ion flow threshold and corona quenching are calculated and compared with previous measurements. The method of calculation is extended to calculate how high the surface potential of the charged dielectric needs to be to trigger a micro-spark in the electrostatic discharges from grounded point electrodes.