Aspects of semiconductive shields under accelerated wet electrical aging conditions of power cables

Modern power cables are insulated with crosslinked polyethylene (XLPE) and semiconductive shields. The aging of power cables is influenced by multiple factors such as electrical, thermal, mechanical and environmental stresses. Semiconductive shield technology has advanced to improve the dielectric degradation at the interface with the cable insulation. Clean carbon black is critical for semiconductive shield compounds performance. Model XLPE cables with conventional semiconductive shields with different types of carbon black were subjected to 9 kV/mm voltage and 70 °C in the presence of water for 1,000 hours to identify the parameters, affecting the endurance of cables to electrical stress. It was found that the semiconductive shield with a low ion content resulted in higher breakdown strength than semiconductive shield with a high ion content. The high thermal extrusion stability of the semiconductive shield compounds can reduce scorch byproducts in the cable extrusion process to allow for longer production run and smooth surface. The selection of clean semiconductive shield and the enhanced cable extrusion processing behavior are key factors to improve on wet electrical aging performance.