交联聚乙烯电缆绝缘中的导电和非导电型电树枝

研究发现,交联聚乙烯中存在导电型、非导电型和混合型三种电树枝,分别对应于不同的生长机理,主要取决于介质的聚集态和施压频率等.实验表明,均匀结晶态中的电树枝为导电型,非均匀结晶态大球晶界面的电树枝为非导电型;频率会促进非导电型电树枝的发展,但对导电型电树枝的引发与生长不产生显著影响.非导电型电树枝引发过程较弱时,会缓慢发展成为混合型.研究分析证实,空间电荷限制下的树枝尖端微击穿是深入到晶体中的导电型电树枝缓慢发展的主要过程,局部高温高压气体沿晶界弱区迅速膨胀、树枝通道中的局部放电和电荷复合等是非导电型电树枝发展的主要过程.

CONDUCTING AND NON-CONDUCTING ELECTRICAL TREES IN XLPE

It is found in this paper, there are three kinds of electrical trees in XLPE, which are conducting tree, non- conducting and compound trees. The growing mechanisms of these electrical trees are mainly depended on the congeries of the dielectric; it is also influenced by frequency of applying voltage. The experiment shows, when material crystallized perfectly the electrical tree branch in XLPE will be conducting type; but only non-conducting electrical tree can develop in the boundaries of big crystals. The frequency of applying voltage will promote non-conducting electrical tree initiating and developing; But it is no useful for prompting the type of conducting electrical tree developing. When non-conducting electrical tree initiating is weaker, it will be changed into the type of compound tree gradually in very long developing period. It is confirmed by our research and analysis that the tiny break down of the material in the tip of tree branch is main cause of conducting tree developing, and the space charges nearby the tip of the tree is main reason that restrict conducting electrical tree developing; For non-conducting electrical tree developing, partial high temperature and pressure gas very quickly expand along weak region of the bounder of crystal, stronger partial discharge and charge combine occur in the tree channel, there are main reason.