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 char
ge 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. T
he charge accumulation on the dielectric surface proceeds to the maximum po
ssible 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 ga
p axis to vanish at the point tip. The percentage decrease of the field bec
omes more pronounced with the increase of the diameter of the dielectric la
yer. The effect of inter-electrode spacing and the dielectric layer thickne
ss 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 lin
es from the stressed point to the ground plane, the field enhancement facto
r increases and the volume charge density decreases along the flux lines. T
he voltages of the ion flow threshold and corona quenching are calculated a
nd compared with previous measurements. The method of calculation is extend
ed to calculate how high the surface potential of the charged dielectric ne
eds to be to trigger a micro-spark in the electrostatic discharges from gro
unded point electrodes.