Application of the critical volume theory to estimating impulse corona characteristics in the coaxial cylindrical electrode arrangement

Corona discharge causes the attenuation and distortion of lightning and switching surges propagating along overhead transmission lines. Therefore, knowledge on surge corona characteristics is of great importance for insulation coordination studies. Most of the studies pertaining to corona effects on wave propagation on overhead line conductors neglect the fact that surge corona inception is stochastic in nature. This can be accounted for by applying the well-established theory of critical volume, allowing for statistical distributions of impulse corona inception characteristics to be estimated. In the present study the critical volume theory is applied to estimate impulse corona characteristics in the coaxial cylindrical electrode arrangement; this configuration is most commonly used in scale model experiments for assessing corona performance of overhead lines. The developed model accounts well for the effects of steepness of the wavefront of the impulse voltage on corona characteristics. The dependence of the estimated impulse corona inception probability distributions on the density and lifetime of negative ions is assessed and discussed.