交联聚乙烯电力电缆的电树枝化试验及其局部放电特征

Experimental Research on Electrical Treeing and Partial Discharge Characteristics of Cross-linked Polyethylene Power Cables

电树枝化是影响交联聚乙烯（cross—linked polyethylene，XLPE）绝缘电力电缆长期安全运行的瓶颈，需要深入研究XLPE电缆绝缘的老化机制，尤其是电树枝化的规律，为XLPE电缆的设计制造和现场的运行管理，特别是在线诊断提供理论支撑。设计了交联聚乙烯电缆样品和相应的试验电极装置，并搭建基于实际XLPE电缆的电树枝化试验平台进行试验。结果表明该试验系统能满足XLPE电缆电树枝化试验研究的要求。以15kV的XLPE电缆作为试验样品，开展常温下工频12～21kV和50～90℃下的电树枝化试验，分析了电压和温度对电树枝形态的影响，得到电树枝局部放电的统计图谱，并将电树枝的生长发展分成4个阶段，分析了电树枝在不同生长阶段局部放电的最大放电量相位和平均放电量相位的分布，提取了其偏斜度等统计特征量，结果表明电压和温度对实际XLPE电缆中电树枝形态的影响与针一板电极得到的结果趋势相同，但是电树枝生长过程存在着一定的差异，同时最大放电量相位分布和平均放电量相位分布的3阶矩随着电树枝的生长发展而减小，可作为诊断电树枝生长发展阶段的参考量。

The bottleneck affecting the long-term operation safety of cross-linked polyethylene （XLPE） power cables is electrical treeing, and it is necessary to study on the insulated aging mechanism of XLPE power cables, especially on the law of treeing, to provide theory support for the manufacture, operation management and on-line diagnosis. XLPE power cable sample and electrode test system was designed and built to simulate electrical treeing in actual XLPE cables. Results show that the testing system can meet research requirements on electrical treeing. Electrical treeing tests on samples of 15 kV XLPE power cables were carried out at power frequency of voltages from 12-21 kV and temperature from 50-90 ~C, and the influence of voltage and temperature on morphology of electrical trees was analyzed, In addition, partial discharge （PD） patterns of electrical trees during tree growth were also studied. It has been found that propagation process of electrical trees can be divided into four stages. The maximal discharging-phase distributions, average discharging-phase distributions and statistical parameters derived from PD distributions were presented. The results show that in actual XLPE power cable, the effect of voltage is similar to needle-plate electrode system on morphology of electrical trees, however, there are some differences in propagation process of electrical trees, and the skewness of the maximal and mean discharging-phase distributions decreases with the propagation of electrical trees, which may potentially be considered as a parameter to diagnose electrical tree propagation stages.