Failure of underground cables due to electrical treeing phenomena, i.e. formation of electrical discharges in the imperfections of cable insulation, is a major problem faced by electrical utilities. Many research works on nanocomposites are being carried out to improve the electrical treeing resistance of the XLPE cable insulation material. Technological advancements in communication and data analytic systems have shown the way for implementing online continuous partial discharge (PD) monitoring systems for high voltage apparatus. Hence collection of PD database of XLPE nanocomposites in the laboratory during entire electrical tree growth process is important for implementing efficient condition monitoring systems and relatively little work has been published in this area. In this work, PD characteristics of XLPE nanocomposites with 1, 3, 5 and 10 wt% silica were investigated. Electrical tree growth and corresponding phase resolved PD (PRPD) pattern were analysed with respect to time. Cluster analysis of equivalent time–frequency mapping of PD signals was carried out with respect to tree growth time period. Statistical analysis was performed for the entire set of PD data. Results show that cluster analysis of T–F map of PD data is useful in estimating early failure of insulating material due to treeing. Addition of silica nano fillers in the range of 3–5 wt% concentration significantly improves the PD resistance and breakdown time of XLPE material.

中文翻译：

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使用时间-频率图和局部放电信号聚类分析研究 XLPE 纳米复合材料的电树生长

由于电树现象（即在电缆绝缘缺陷中形成放电）导致的地下电缆故障是电力公用事业面临的主要问题。许多关于纳米复合材料的研究工作正在开展，以提高 XLPE 电缆绝缘材料的抗电树化能力。通信和数据分析系统的技术进步为高压设备的在线连续局部放电 (PD) 监测系统提供了途径。因此，在整个电树生长过程中，在实验室中收集 XLPE 纳米复合材料的 PD 数据库对于实施有效的状态监测系统非常重要，并且在该领域发表的工作相对较少。在这项工作中，XLPE 纳米复合材料的 PD 特性与 1, 3, 研究了 5 和 10 重量％的二氧化硅。电树生长和相应的相位分辨 PD (PRPD) 模式就时间进行了分析。对树木生长时间段进行 PD 信号等效时频映射的聚类分析。对整套 PD 数据进行了统计分析。结果表明，局部放电数据的 T-F 图的聚类分析可用于估计绝缘材料由于树化而导致的早期失效。添加 3-5 wt% 浓度范围内的二氧化硅纳米填料显着提高了 XLPE 材料的抗PD 性能和击穿时间。对树木生长时间段进行 PD 信号等效时频映射的聚类分析。对整套 PD 数据进行了统计分析。结果表明，局部放电数据的 T-F 图的聚类分析可用于估计绝缘材料由于树化而导致的早期失效。添加 3-5 wt% 浓度范围内的二氧化硅纳米填料显着提高了 XLPE 材料的抗PD 性能和击穿时间。对树木生长时间段进行 PD 信号等效时频映射的聚类分析。对整套 PD 数据进行了统计分析。结果表明，局部放电数据的 T-F 图的聚类分析可用于估计绝缘材料由于树化而导致的早期失效。添加 3-5 wt% 浓度范围内的二氧化硅纳米填料显着提高了 XLPE 材料的抗PD 性能和击穿时间。