In this paper, the effects of harmonic superimposed DC voltage on electrical tree growth characteristics in ethylene propylene diene monomer (EPDM) for HVDC cable accessories insulation are studied. Harmonic component with a frequency from 50 to 450 Hz is superimposed on DC voltage to analyze the mechanism of harmonic amplitude, order and voltage polarity on electrical tree growth. The results show that the electrical treeing process is promoted with an increase in harmonic amplitude and order, which brings a longer tree length and more accumulated damage to the insulation. Especially when the amplitude of harmonic component exceeds that of DC voltage, the electrical treeing processes are significantly deteriorated, resulting from the large amount of energy released by the recombination of hetero charges. The growth of electrical tree has an obvious polarity effect which tends to be branch-like tree under positive voltage and bush-like tree under negative voltage. The polarity effect may be caused by different propagation processes of electron avalanche under different voltage polarities. As harmonic order increases, the main channel of positive electrical tree is broadened, while the negative tree becomes denser with a lot of bifurcation. These results indicate that harmonic component accelerates the initiation and propagation of electrical tree by affecting the charge transport behavior under the superimposed electric field.

中文翻译：

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高压直流电缆附件绝缘三元乙丙橡胶中谐波分量对电树的影响


本文研究了谐波叠加直流电压对高压直流电缆附件绝缘三元乙丙橡胶(EPDM)电树生长特性的影响。将频率为 50 至 450 Hz 的谐波分量叠加在直流电压上，分析谐波幅度、阶次和电压极性对电树生长的机制。结果表明，随着谐波幅值和次数的增加，电树过程得到促进，从而带来更长的树长度和更多的绝缘累积损伤。特别是当谐波分量的幅度超过直流电压的幅度时，由于异质电荷的复合释放大量能量，电树过程显着恶化。电树的生长具有明显的极性效应，在正电压下趋向于枝状树，在负电压下趋向于灌木状树。极性效应可能是由于不同电压极性下电子雪崩的传播过程不同而引起的。随着谐波次数的增加，正电树的主通道变宽，而负电树变得更密集，分叉较多。这些结果表明，谐波分量通过影响叠加电场下的电荷传输行为来加速电树的引发和传播。