The influence of absorbed gases on electroluminescence phenomenon in polymeric materials subjected to high electrical stress

Whenever a polymeric material is subjected to an electrical stress, imperfections such as protrusions, contaminants and microvoids, will all act as points where the field is enhanced, causing the degradation processes to be initiated. However, as manufacturing technology improves, insulation systems are of higher quality and their interfaces smoother. The reduction in concentration and size of impurities has led to more research at the atomic scale where space charges can play a fundamental role in triggering ageing phenomena. Since space charges seem to play a significant role in long-term electrical degradation of polymeric insulation, researchers are investigating the energy dissipation of mobile and trapped charges in the molecules of a dielectric medium. The dissipation process is associated with the emission of visible photons, a process known as electroluminescence (EL), which has been observed in various materials. This paper presents the series of experiments completed in the study of EL phenomenon in low-density polyethylene (LDPE); the most common type of material used for high voltage cable insulation. In addition to that, the role of gas diffusion into the polymer on the processes leading to EL has also been examined.