Simulation of point plane corona inception in dry air at Atmospheric pressure

Numerical analysis of electric field variation between point plane electrode configuration have been carried out by few investigators using charge simulation method. In order to analyse corona performance in air at atmospheric pressure, electric field computations between point plane gaps have been carried out using ANSYS software version 9.0 (multiphysics). The software uses finite element method for analysis. For values of hemispherical tip diameter of 1.0 mm and above the electric field variation between point plane gaps along point electrode axis does not vary considerably (less than 0.5%) over several mean free paths in atmospheric air. From these considerations, corona inception potentials have been computed in air at atmospheric pressure between point plane gaps using Townsend´s theory applicable to non uniform fields. The computations have been carried out for values of tip diameter 1.0 mm, 2.0 mm, 3.0 mm and for gap distances varying from 20 mm to 50 mm (approximately) for positive polarity of the tip in the present work. The computed corona inception potentials showed good agreement (within plusmn 10%) with experimental results reported in literature. This suggests that the positive polarity corona inception voltages can be calculated for these types of gaps as voltage of point electrode that causes electron multiplication to be 10⁶.