Study on dielectric structure and space charge behavior of XLPE/SiO2 nanocomposites

Abstract

Polymer materials are excellent insulation materials due to low conductivity, low loss and high breakdown field strength. In recent years, with the improvement of power system voltage level and the increase of transmission capacity, the dielectric property, mechanical performance and thermal stability of conventional insulating materials are put forward higher requirements. By using organic nanoparticles to modify the polymer, it can effectively improve the breakdown strength, suppress space charge injection, reduce dielectric loss and thus improve the insulation performance. In this paper, the nano-SiO 2 particles treated by different surface modifiers were melting blended with crosslinked polyethylene to prepare the XLPE/SiO 2 nanocomposites. The nano-SiO 2 particles is well dispersed in the XLPE matrix observing by scanning electron microscopy (SEM), the dispersion effect depends on the polarity of the compatibilizer and the matching effect of the surface modifier. The melting and crystallization behavior of the nanocomposites were studied by differential scanning calorimetry (DSC), the crystal morphology and crystal distribution of the samples were observed by SEM. The results show that the organic SiO2 plays a role of the heterogeneous nucleation in the polymer to reduce the melting point of the polymer, decrease the crystal size and distribute more evenly. The nucleation effect of nanoparticles leads to an increase in the crystallization rate. The space charge characteristics of nanocomposites are measured by pulse electro-acoustic method (PEA). The results indicate that the interfacial effects of organic nano-SiO 2 introduce deep traps in the polymer matrix, which are beneficial to bound charge and reduce the carrier mobility, thus effectively avoiding the accumulation and migration of space charges. The effect of organic surface modifier on the space charge transfer and suppression characteristics of nanocomposites is discussed based on the structural characteristics.