Impact of semiconductive shield quality on accelerated aging cable performance

Semiconductive shield quality is critical to the life expectancy of power cables in medium, high, and extra-high voltage classes. The material properties and cable performance under accelerated conditions were compared for different commercial semiconductive shield compounds. All of the semiconductive shield compositions were found to be crosslinkable, contain similar levels of carbon black to be conductive, meet volume resistivity and physical properties required by IEC specifications and considered suitable for MV cable applications. The cables made with compound containing more protrusions and total chemical impurities had a much shorter characteristic life, less retained breakdown strength even as low as 7.8 kV/mm, and would be expected to have much less reliability than the cable with high quality semiconductive shields. The combination of these critical performance factors clearly indicates that semiconductive shields of poor quality can drastically reduce the effectiveness of an insulation material to achieve an expected long lifetime cable.