Effect of Tracking and Treeing on Impulse Breakdown in Solid insulator

用带像增强器的摄像机，在标准雷电冲击电压下，观察了油浸式固体绝缘子、高密度聚乙烯(HDPE)、环氧树脂(EP)和环氧玻璃纤维层压板(EGML)表面爬电放电的传播特性。EGML表面的蠕变放电显示出一个独特的特征，即在流光上有发光的放电点。研究表明，这种现象是由于EGML中玻璃纤维组分的存在，放电斑点的出现增加了放电能量。另一方面，通过对点-面和点-点电极系统施加间歇雷电冲击电压，研究了PMMA(聚甲基丙烯酸甲酯)的树枝特性。电树的形状和延伸长度清楚地揭示了极性对外加电压的影响。在点电极上施加脉冲电压4次以上，对电树的生长有很大的抑制作用。这一测试结果归因于第一次电压作用下初始树枝形成时积累的电荷。此外，新开发了大尺寸取向扩展链结晶聚乙烯(ECCPE)。用针板电极系统研究了ECCPE的电树状放电。树木的生长方向完全受ECCP取向的控制，当取向与电场平行时，树木呈单线状生长，没有分枝。当取向垂直于电场时，它向取向方向传播，没有分支。树枝状放电电流在取向方向上也表现出明显的差异。这一研究结果对电绝缘领域具有很好的应用前景。

Using a standard lightning impulse voltage, the propagation aspects of a creepage discharge over the surface of oil-immersed solid insulators, high density polyethylene (HDPE), epoxy resin (EP) and epoxy glass mat laminate (EGML), have been observed by means of a camera equipped with an image intensifier. The creepage discharge over the surface of EGML revealed to a distinctive aspect which had the luminous discharge spots on the streamers. It was clarified that this phenomenon was attributed to the existence of a glass fiber ingredient in EGML and the discharge energy was increased by the occurrence of the discharge spots.On the other hand, the treeing properties of PMMA (polymethylmethacrylate) were studied by the intermittent lightning impulse voltage to either the point-plane or the point-point electrode system. The forms and extension lengths of the electrical tree revealed clearly the polarity effect on the applied voltage. The growth of electrical trees was greatly restrained when the impulse voltage was applied to the point electrode more than 4 times. This test result was attributed to the electric charge accumulated by the initial tree generation due to the first voltage application.Furthermore, the oriented ECCPE (Extended Chain Crystal Polyethylene) of a large size was newly developed. Electrical treeing discharges of ECCPE were investigated using a needle to plate electrode system. The direction of the tree-growth was completely controlled by the orientation of ECCPE.When the orientation was parallel to an electric field, the tree propagated as a single line without branchings. When the orientation was vertical to the electric field, it propagated to the orientation direction without branchings. Treeing discharge current also revealed the remarkable difference on orientation directions.The results obtained in this investigation are promising for a field of electrical insulations.