Abstract
Exposure of insulating systems to strong electric field and other environmental stresses may cause loss of their desired properties. In high-voltage applications, phenomena, such as corona discharges and unexpected flashovers, may deteriorate the surface as well as bulk conditions of an insulating material and thereby affect its lifetime. In this article, several types of corona-exposed HTV-SiR/ethylene propylene diene monomer (EPDM) blends filled with different concentrations of nano-sized boron nitride and silicon carbide particles are evaluated and the induced modifications of their properties are presented and discussed. The diagnosis is based on measured data of surface partial discharge (PD) and volume current. For the latter, experiments were performed at different levels of electric field between 0.5 and 4 kV/mm and ambient temperature ranging from 22 °C to 70 °C. Results of the conducted experiments revealed the degradation of surface properties through an increase in the PD magnitude. It was also observed that corona aging of the samples decreases the threshold electric field particularly at elevated temperatures, above which space charge effect in the materials may become significant. Moreover, it was observed that the blend compositions loaded with nanofillers retard surface PD and bulk deterioration.