The growth and partial discharge (PD) characteristics of electrical tree in crosslinked polyethylene (XLPE) needle-plate electrode samples are investigated under constant dc voltage at different temperatures. The results reveal that under the experimental conditions, the electrical trees are all branch trees, and the discharge intensity fluctuates with time. The increase in temperature promotes the growth of electrical tree as well as the intensity of PD. Five texture features of PD ${q}$ - ${t}$ histogram are extracted and used as the elements to evaluate the insulation status of XLPE needle-plate electrode under dc voltage based on the gray correlation degree. The area ratio and lateral tree ratio of electrical tree is extracted based on the gray histogram. The lateral tree ratio increases with the increase in temperature, which is closely related to the intensity of PD. Gray correlation theory is used to evaluate the status of XLPE insulation. The results reveal that the evaluated insulation statuses based on the gray correlation degree are the same as those based on experience, which indicates that the proposed diagnosis method of XLPE insulation status based on the gray correlation degree with ${q}$ - ${t}$ histogram texture features as elements has a high accuracy.

中文翻译：

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一种针对 XLPE 中直流电气树损坏的建议诊断程序

研究了不同温度下恒定直流电压下交联聚乙烯（XLPE）针板电极样品中电树的生长和局部放电（PD）特性。结果表明，在实验条件下，电树均为分枝树，放电强度随时间波动。温度的升高促进了电树的生长以及局部放电的强度。PD的五个纹理特征 ${q}$- ${t}$提取直方图作为评价交联聚乙烯针板电极在直流电压下的绝缘状态的要素，基于灰色关联度。基于灰度直方图提取电气树的面积比和侧向树比。侧树比随温度升高而增加，与PD强度密切相关。灰色关联理论用于评价交联聚乙烯绝缘状况。结果表明，基于灰色关联度的绝缘状态评估与基于经验的绝缘状态评估结果相同，表明所提出的基于灰色关联度的交联聚乙烯绝缘状态诊断方法具有 ${q}$- ${t}$直方图纹理特征作为元素具有很高的准确性。