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Effect of Thermo-oxidative Aging on Space Charge Characteristics and Physicochemical Properties of XLPE/Al2O3 Nanocomposites for HVDC Cables

Cross-linked polyethylene (XLPE) nanocomposites show the potential to be insulating materials for high-voltage direct current (HVDC) cables because of their improved electrical properties. However, the role of nanoparticles on the thermal aging properties of cable insulation is still unclear. In this paper, the influence of thermo-oxidative aging on the space charge characteristics and physicochemical properties of pure XLPE and XLPE/Al2O3 nanocomposites were comparatively investigated. Space charge accumulation characteristics, crystallinity and carbonyl index were tested by pulse electroacoustic method (PEA) system, X-ray diffraction (XRD) and Fourier-transform infrared (FTIR), respectively. It was found that appropriate number of nanoparticles can improve the crystallinity of XLPE, reduce the low-molecular impurities containing carbonyl groups generated and also has an excellent effect on limiting the injection of homo-charges during the aging process. Compared with pure XLPE, XLPE/Al2O3-A with appropriate number of nanoparticles still has excellent space charge distribution and physicochemical properties when aged for 672 hours. The dispersive interface region between nanoparticles and matrix may be the reason for the anti-thermal aging ability exhibited by the nanocomposites.