Accelerated thermal ageing on performance of polypropylene-based semiconducting screen for high voltage direct current cable applications—Effect of antioxidants

The potential of using eco-friendly thermoplastic polypropylene (PP)-based insulation for high voltage direct current (HVDC) cable has been widely investigated but much less work on the PP-based semiconducting screen (SC). Considering a long service life (>30 years) under high temperature and high electrical stress is required for typical HVDC cables, and investigations on the effect of antioxidant (AO) concentration and thermal oxidative stability, mechanical, and electrical properties of PP-based SCs have been conducted. It has been demonstrated that an appropriate combination and amounts of AOs are critical for achieving high thermal stability and maintaining the mechanical properties of SC after ageing in a harsh environment (150°C, with Cu, in air, 7 days). Although higher amounts of space charges have been observed in SC/PP/SC samples with higher AO concentrations, the impact on space charge behaviours is less after ageing, suggesting that ageing (or operating at high temperature) leads to microstructure evolution in SC and can potentially mitigate space accumulation in PP-based insulating materials.