The Effect of Electrically Prestressing on DC Breakdown Strength in the Nanocomposite of Low-density Polyethylene / nano-SiOx

Nano-SiOx and micro-SiO2 particles were homogeneously dispersed in low-density polyethylene with double-solution method. The dc breakdown strength of the composite containing various contents of nano-SiOx was experimentally investigated, as well as the composite containing micro-SiO2. The breakdown strength of the nanocomposite is greater than that of pure LDPE. For example, the breakdown strength of the nanocomposite is 16% greater than that of pure LDPE. However, the breakdown strength increment of the nanocomposite decreases as the nano-SiOx content increases. The breakdown strength of the composite containing micro-SiO2 is lower than that of pure LDPE and the breakdown strength decrement increases as the micro-SiO2 content increases. It is very interesting that electrical prestressing enhances the breakdown strength of the nanocomposite and the more content, the more enhancements. As the nano-SiOx content reaches 3%wt, the breakdown strength of prestressed nanocomposite is 20% higher than that of non-prestressed nanocomposite. However, electrical prestressing decreases the breakdown strength of microcomposite, and it could hardly find any distinct content effect on the breakdown strength in the prestressed microcomposite. Finally, the different prestressing effects on breakdown strength in both kinds of composites are discussed with the different interface characteristic in both composites.