Jerker B. I. Kjellqvist

High salinity wet electrical ageing behavior of polyolefin blends

Power delivery products (e.g. power cables) and accessories (e.g. joint, termination, and other solid dielectric components) experience ingress of moisture when employed underground or in submarine condition. Over years of services in a wet condition, power cables and other cable components degrade due to water treeing, resulting in reduction of electrical breakdown strength of cable system. Olefin diblock copolymer is a new designed polymer having “hard” polymer segments and “soft” copolymer segments by controlling composition distribution within a single polymer chain. In this study, the wet electrical breakdown behavior of polymer blends with low density polyethylene and olefin diblock copolymer is investigated in high salinity condition.

Evaluation of UV stability of outdoor dielectric compounds for covered overhead lines

For outdoor covered overhead lines, the service life normally depends on cable weathering and environmental stress. This paper presents the comparison of ageing deterioration of crosslinkable polyethylene compounds for outdoor covered overhead lines by using an accelerated weathering test. The effect of carbon black on crosslinkable polyethylene compounds was correlated as an ultraviolet absorber by inhibiting photodegradation. An accelerated weathering test simulated damaging effects of long term outdoor exposure of materials by exposing test samples to varying conditions of the most aggressive components of weathering, such as ultraviolet radiation (340 nm), moisture, and heat continuously for 1,000 hours. Physical, chemical, and morphological analyses were conducted to characterize the degree of ageing deterioration of compounds.

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.