在运行 20 多年的电缆上截取长、短试样，分别进行等温松弛电流法试验，再利用电热老化前后的长样进行等温松弛电流法试验． 结果显示长样由于带有电缆接头而体现出老化因子大的特点，表明电缆接头是电缆的薄弱环节，接头更容易受到电热作用而发生老化;经电热老化后的长样因内部缺陷增加而使老化因子增大，说明电热处理会加重电缆老化程度;通过逐级耐压法对电缆试样进行试验，结果表明试样的剩余寿命在 10 ～20 年的范围内，和设计时的预期寿命一致． 基于等温松弛电流法的试验结果对 XLPE 电缆进行老化状况评估，通过耐压法试验结果给出其具体的剩余寿命，两者相辅助结合可以进行比较全面的判断．

Short and long samples from the cables running for over twenty years were cut out． Then，the short samples as well as the long samples before and after the electric heating process were tested by means of the isothermal
relaxation current method． The results show that the long samples have a larger aging factor because they have cable
joints，which means that the cable joints constitute the weak link in the cables，and the joints under the electric
heating process are easier to get aging． After the electric heating process，the aging factor of the long samples increases due to the increase of their internal defects，which means that the electric heating process can aggravate the
aging degree of the cables． From the voltage-endurance tests，it is found from the voltage-endurance tests that the
residual life of the samples ranges from ten to twenty years，which is consistent with the expected life in their design． Thus，it comes to the conclusion that the XLPE cable can be more comprehensively judged by combining the
isothermal relaxation current method with the stepwise voltage-endurance method，which means that the aging degree and the residual life can be respectively assessed by using both methods．