Particle-in-cell simulations of discharge along angled insulators in compressed gases

Summary form only given. This paper deals with the discharge along the surface of angled insulators in compressed gases using 3D finite difference particle-in-cell simulation. The simulation is carried in pure nitrogen at atmospheric pressure. The ionization of neutral atoms of nitrogen takes place by electron impact leading to production of positive ions and secondary electrons. The ionization cross sections of electrons with neutral gas molecules are taken as function of electron energy. The pulse rise time is 5ns with pulse duration of 50ns. The spacer angle `θ´ is measured between the inclined surface and line vertical to the electrode. The angle is positive when narrow end is connected to the anode and negative otherwise. The positive spacer angle shows a reduced discharge voltage for a 20mm gap length which is close to the discharge voltage for cylindrical insulators. The negative spacer angle shows a discharge voltage close to the bulk gas gap condition. This is explained by a reduction in the momentum profile of electrons for positive spacer angle which aids in earlier emission of electrons and the discharge path followed is same as that for cylindrical insulators whereas an increase in momentum for negative spacer angle gives a longer discharge path and hence condition close to the bulk gas gap. This finds application in the design of high voltage insulators subjected to impulse voltages.