谐波交流电对交联聚乙烯电缆的树状放电的影响

Effect of harmonic AC on dendritic discharge of XLPE cables

由于外加电压的影响,电气树形状会发生变化。在谐波电压和较低的总谐波失真下形成灌木型电气树。随着谐波含量的增加,形成了纤维状的电树。威布尔分布研究表明,随着THDS的增加,谐波水平(奇数/偶数)的增加会加速电缆绝缘中的树形生长,导致电缆绝缘早期失效。由于电树形成而辐射的超高频(UHF)信号的频率含量在0.5~2GHz的频带内。采用频谱功率比对特高频信号进行分类,可以对不同电压下在绝缘材料中起起伏伏的电树形状进行分类。利用超高频信号进行的相位分辨局部放电(prpd)分析表明,在电压上升率较高的谐波电压下发生放电,从而加速了电树的生长。在电树生长期间,放电发生在三角形电压的整个阶段。局部放电发生在低频交流电压的峰值和电源电压升高时的升高部分。

The shape of electrical trees gets altered due to applied voltage profile.Bush type electrical trees forms under harmonic voltages with lower THDs.With increase in harmonic level with increased THDs fibrillar type electrical trees were formed.Weibull distribution studies indicate that increase in harmonic level(odd/even)with higher THDs accelerates the tree growth in cable insulation causing early failure of cable insulation.The frequency content of the Ultra High Frequency(UHF)signals radiated due to tree formation lies in the frequency band of 0.5~2 GHz.Adoption of spectral power ratios to UHF signal can classify the shape of electrical trees that has incepted and propagating in the insulating material under different voltages.Phase Resolved Partial Discharge(PRPD)analysis using UHF signal indicates that discharges occurs under harmonic voltages where the rate of rise of voltage is high thereby accelerating the tree growth.During tree growth discharges occur in the entire phase of the triangular voltage.Partial discharges occur at the peak with the low frequency AC voltage and at the raising portion when the supply voltage is increased.