添加纳米MgO对交联聚乙烯中直流接地电树枝的影响

Effect of Nano-MgO Addition on Grounded DC Tree in Cross-linked Polyethylene

对交联聚乙烯(cross-linked polyethylene,XLPE)材料与质量分数为0.5%的MgO/XLPE纳米复合材料分别进行了直流接地电树枝实验与基于电声脉冲法的空间电荷测量。电树枝实验表明,正极性下MgO/XLPE纳米复合材料表现出更高的50%电树枝引发电压;空间电荷测量结果表明XLPE中有更多同极性电荷注入,说明纳米颗粒的添加阻碍了针尖处同极性电荷的注入与抽出,进而阻碍了电树枝引发。正极性下MgO/XLPE纳米复合材料表现出更小的平均电树枝长度与宽度,这是由于高场强区产生的载流子与纳米颗粒发生碰撞,导致电树枝生长较慢。此外,正极性下MgO/XLPE纳米复合材料中平均电树枝长宽比随电压升高下降更快,这是由于电树枝无法穿透纳米颗粒,只能从其表面绕过,导致了电树枝通道方向的改变与细小分枝的产生。

Grounded DC tree experiments and space charge measurement based on the pulsed electro-acoustic（ PEA） method are performed on XLPE and 0. 5% by weight MgO / XLPE nanocomposite. The tree experiment shows that MgO / XLPE nanocomposite exhibits higher 50% tree inception voltage under positive voltages. The space charge measurement shows that more homocharge is injected in XLPE,which indicates that nanoparticles impede the homocharge injection or heterocharge extration at needle tip,thus impedes the generation of electrical tree. And MgO / XLPE nanocomposite shows smaller average tree length and width when under positive voltages,which may be attributed to the carries generated from high stress region colliding with nanoparticles and slowing the tree propagation. M oreover,the average tree length-width ratio in MgO / XLPE nanocomposite decreases faster with the positive voltage increasing.This can be explained by the fact that electrical tree is hard to penetrate nanoparticles,but can only develop around their surfaces,which results in the change of tree channel direction and emergence of many thin lateral branches.