High field conduction and polarization phenomena in polymeric dielectrics

The thesis consists of two parts, both related to fundamental aspects of polymeric dielectrics. The first part is focused on fundamental high field phenomena in solid dielectrics related to degradation thereof. The charge-injection measurement using a guarded needle and the electroluminescence test using metal/semicon needle electrodes are developed to measure the critical field above which carriers with high mobility start to damage the polymeric dielectric. The measurements are simulated with transient nonlinear finite element analysis as well as with analytic approaches. These studies are very insightful for the understanding of high field conduction induced degradation for polymeric dielectrics in ac/dc systems at engineering fields. The second part of the presentation investigates pyroelectric effects in coaxial cables formed of multiple polymeric dielectric layers, some of which have large thermal expansion while others have strong polarization. The measured pyroelectric response is well simulated, including nonlinear effects such as temperature dependent heat capacity and thermal expansion.