Evaluation of electrical aging life of nano SiO₂/PP composites

The electrical aging life of polypropylene (PP) insulation, a new environmentally friendly material, and its nano-SiO₂ composites were investigated to provide theoretical support for the reliability of PP-insulated cables in later applications. Based on the electric aging life formula-inverse power method, the life model parameters of PP insulation and SiO₂/PP composites were estimated by constant voltage accelerated aging test, and then the reliabi-lity of life index n was evaluated by stepwise accelerated aging test. The SiO₂/PP composites were also structurally characterized and performance tested. The results show that the lifetime index n of SiO₂/PP6 is 14.61, which is enhanced by 16.51% compared with that of PP6 of 12.54. It is found in the experimental stage that the doping of SiO₂ has a significant effect on the enhancement of PP6's time to failure at lower aging field strengths, and it is predicted that the long-term electrical aging lifetime of SiO₂/PP6 is more than five times that of PP6 below the aging field strength of 25 kV·mm⁻¹. Meanwhile, the doping of nano-SiO₂ reduced the industrial frequency dielectric loss factor and lowered the loss peak height of PP insulation. Based on the electrical aging cavity theory, it is proposed that SiO₂ enhances the electrical aging life of PP insulation by limiting the chain segment breakage by consuming hot electron energy.