A new method for destruction-free lifetime evaluation on cross-linked polyethylene cables is studied in this paper. The third order exponential decay fitting is utilized to process measured isothermal relaxation current (IRC) data. The current I could be calculated by subtracting the steady direct current component from measured current, and then the relationship between I~*t and log (t) is obtained. Consequently, the weight of each kind of depolarization current component is obtained and the aging status could be evaluated by means of analysis and comparison on the peak-value location. The aging factor (A) is introduced for the convenience of classifying the aging level of cables. The experiment results show that although there are some errors, this new method can effectively evaluate the aging status of cables. Because of the influence of sampling and the manufacturing technology, to some extent, the factor A calculated from these experiments is bigger than those reported by foreign scholars.%研究了一种新的非破坏性交联聚乙烯电缆寿命评估的试验方法.利用三阶指数衰减函数对测得的等温松弛电流数据进行拟合处理,计算得出去除稳态直流分量的电流值I,获得I~*t～log(t)曲线.通过比较该曲线中峰值的位置,分析电缆绝缘各种退极化电流分量的权重,并评估绝缘的老化状态.为了方便对绝缘老化状况进行划分,引入老化因子A.试验结果表明,等温松弛电流法对电缆的寿命评估存在一定误差,但仍可以有效地评估电缆的老化状态.受到试验取样及电缆制造工艺的影响,计算所得的老化因子与国外学者报道的结果相比普遍偏大.
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