纳米SiO2对交联聚乙烯交/直流击穿强度和耐电树枝性能影响

为系统地研究纳米SiO₂对交联聚乙烯（XLPE）交/直流击穿强度和交/直流耐电树枝特性的影响，使用平行双螺杆分别制备了含0.5wt%和1wt%纳米SiO₂的纳米SiO₂/XLPE复合材料，以商用直流电缆料和普通XLPE作为参照，测试了掺杂纳米SiO₂对XLPE交流电树枝和直流接地电树枝的引发和生长特性及交/直流击穿强度的影响。实验结果表明，商用直流电缆料的直流击穿强度与普通XLPE相近，但其直流接地电树枝的引发更困难，树枝生长也更缓慢；随着纳米SiO₂添加量增大，纳米SiO₂/XLPE复合材料交/直流击穿强度的作用增强，对交/直流电树枝引发的抑制作用也增强，1wt%纳米SiO₂/XLPE复合材料具有显著抑制直流接地电树枝生长的效果，其直流接地电树枝引发和生长特性均优于商用电缆料；1wt%纳米SiO₂/XLPE复合材料的交流击穿强度和交流电树枝起始电压均高于普通XLPE，但其对交流电树枝的生长抑制作用仅局限在电树枝生长初期，电树枝生长达到一定阶段后，1wt%纳米SiO₂/XLPE复合材料中的电树枝生长速度超过普通XLPE。 

Effects of nano SiO2 on AC/DC breakdown strength and electrical treeing resistance of cross-linked polyethylene

In order to systemically investigate the effects of nano SiO₂ on the alternating current/direct current (AC/DC) breakdown strength and AC/DC electrical treeing resistance properties of cross-linked polyethylene (XLPE), nano SiO₂/XLPE composites with 0.5wt% and 1wt% nano SiO₂ were prepared using parallel twin screw extrude. With untreated XLPE and commercial DC cable XLPE insulation as references, the doping effects of nano SiO₂ on the electrical tree initiation and growth characteristics under AC voltage and periodic grounded DC voltage as well as the AC/DC breakdown strength of XLPE were tested. The experimental results indicate that the DC breakdown strength of commercial DC cable XLPE insulation is similar to that of the untreated XLPE, but the periodic grounded DC electrical tree initiation is more difficult and the tree growth speed is much slower than that of untreated XLPE. With the increase of nano SiO₂ content, its effect on improving AC/DC breakdown strength and inhibiting AC/DC electrical tree initiation are increased. The 1wt% nano SiO₂/XLPE composite has the significant inhibition effect on the imitation and growth of the periodic grounded DC electrical tree, and its tree initiation and growth properties are both superior to the commercial cable material. The AC breakdown strength and the initiation voltage of AC electrical tree of 1wt% nano SiO₂/XLPE composite are both higher than that of untreated XLPE, but the inhibition on the growth of AC electrical tree is limited to the early stage of tree propagation. After the electrical tree exceeds a certain length, the growth rate of electrical tree in the 1wt% nano SiO₂/XLPE composite exceeds that of untreated XLPE.