Investigation of the Partial Discharge Inception and Flashover With IEC‐Based Comparative Tracking Index Electrodes and Comparison With Homogeneous and Inhomogeneous Electric Fields at Varying Pressures for Aerospace Applications

For designing aeronautical components, the creepage distance is usually estimated by considering the pollution level and the dielectric material group as defined by the standard IEC 60664‐1. The material group is expressed by the comparative tracking index (CTI) performed at atmospheric pressure following the standard IEC 60112. Thus, the calculated creepage distance does not consider the influence of altitude for aeronautical applications. This article aims to examine the surface discharge behaviour of solid dielectrics at different air pressures corresponding to flying altitudes of the aircraft. The impact of electrode shape and air pressure on the onset of surface partial discharge (PD) and flashover voltage has been investigated experimentally. The results from standard CTI electrodes (as defined by IEC 60112) are compared to semi‐cylindrical blocks producing homogeneous and needle creating inhomogeneous electric fields. The mechanism of surface discharges until flashover has been investigated using the phase‐resolved PD patterns. The flashover results are compared with Paschen's law of air breakdown, and a modelling approach for PD inception and flashover voltage has been discussed with the obtained results.