The Effects of Nano-SiO2 on the Electrical Treeing Resistance of XLPE

In order to systematically investigate the effects of nano-SiO
2
on the AC and DC electrical treeing resistance properties of XLPE, nano-SiO
2
/XLPE composite with the doping rate of 1wt% was prepared using parallel twin screw extruder. An electrical tree real-time observation system was designed. With untreated XLPE and commercial available XLPE for DC cable insulation as reference, the doping effects of nano-SiO
2
on the electrical tree initiation and growth characteristics under AC voltage and periodically grounded DC voltage were tested under different voltages using needle-plate electrode system. The test results indicate that: the periodically grounded DC electrical tree initiation and growth are more difficult and less harmful than the AC electrical tree. Periodically grounded DC electrical tree initiation of commercial DC cable XLPE is more difficult and the tree growth is much slower than that of untreated XLPE. Nano-SiO
2
/XLPE composite has significant inhibition effect on the initiation and growth of the periodically grounded DC electrical tree, its periodically grounded DC electrical tree initiation property is superior to the commercial DC cable XLPE, and its growth speed of periodically grounded DC electrical tree is between the untreated XLPE and commercial DC cable XLPE. The AC electrical tree test results indicate that: initiation voltage of AC electrical tree of nano-SiO
2
/XLPE is 13.6% higher than that of untreated XLPE, the AC tree length of nano-SiO
2
/XLPE is lower than the untreated XLPE in the early growth stage. However, the AC tree length of SiO
2
/XLPE exceeds that of untreated XLPE after a certain time of stress.