直流交联聚乙烯电缆泄漏电流试验特性研究

Experimental Research on Leakage Current of DC Cross Linked Polyethylene Cable

为研究直流电压下交联聚乙烯(XLPE)电缆出现绝缘缺陷时的泄漏电流特性,模拟高压XLPE电缆常见缺陷,设计并制作了主绝缘外表面划伤、高压端导体毛刺、绝缘内部气隙和外半导电层残留四类典型绝缘缺陷模型,仿真研究了不同缺陷下的电场与电导率分布特性。采用阶梯升压法在直流电压下进行泄漏电流试验,讨论了稳态泄漏电流与电压关系,并对泄漏电流-时间曲线进行波形分析。仿真及试验结果表明:导体毛刺缺陷电场与电导率畸变最严重,绝缘表面划伤缺陷与绝缘内部气隙缺陷畸变程度次之;导体毛刺缺陷泄漏电流增长速度随电压升高明显加快;泄漏电流波动程度随电压升高而增大,但电压升至一定程度后绝缘表面划伤缺陷和导体毛刺缺陷的泄漏电流波动有所减小;不同类型缺陷的各频带小波包系数能量存在差异。

To study the leakage current characteristics of cross linked polyethylene cables with insulation defects at DC voltage, four types of typical insulation defects, including scratch on the insulation surface, metal burr, cavity inside insulation and semiconducting layer residual, were fabricated using XLPE cables. The distribution characteristics of electric fields and conductivity with different defects were simulated. Leakage current test under step-wise DC voltage was conducted. The relationship between steady-state leakage current and voltage was discussed and the leakage currenttime curves were analyzed. The simulation and experimental results show that the metal burr defects have the most serious conductivity and electric field distortions, scratch defect and cavity defect take the second place; the growth rate of the leakage current of the burr defect is obviously accelerated with the increase of voltage; the fluctuation of leakage current increases with voltage increase, but the fluctuation of leakage current of the scratched and burr defects decreases after the voltage rises to a certain extent; the energy of wavelet packet nodes of different defects are different.