电热联合老化对XLPE电缆绝缘特性的影响

Effect of electro-thermal aging on characteristics of XLPE cable insulation

为了探究达到设计寿命的高压交联电缆继续运行的可靠性,文中对一回实际运行32 a的110 kV高压交联聚乙烯(XLPE)电缆采用预鉴定试验方法,进行为期180 d的电热循环加速老化试验。通过综合分析比较试验过程中电缆绝缘内、中和外层的电场强度和温度场变化的差异,并将各绝缘层试验条件转化为导体芯表面得到相应的等效试验条件,发现电缆绝缘中层和外层的等效试验条件接近电缆的实际运行情况。通过相关理化实验分析比较试验前后电缆绝缘各层的微观和聚集态状况。结果发现:绝缘内层在严苛的试验条件下热氧化降解占主导;绝缘中层虽然发生一定的氧化降解,但晶体结构仍有所改善;绝缘外层的结晶形态在温度效应的热刺激下趋于完善。因此,可以评估该退役电缆的其余部分在实际运行条件下仍具有长期服役的潜能。

In order to investigate the reliability of the continuous operation of the high voltage cross-linked cable which reaches the design life limitation,a 180-day pre-qualification test method is carried out on a section of high-voltage cross-linked cable which has been in operation for 32 years.By comprehensively analyzing and comparing the differences of electric field strength and temperature field in the inner,middle and outer layers of cable insulation during the test,the testing conditions of each insulation layer are converted into the surface of conductor core,and the corresponding equivalent testing conditions are obtained.It is found that equivalent testing conditions of the medium and outer positions are close to the cable practical operation condition.Several diagnostic measurements are conducted to analyze the micro-structure and aggregation structure among the samples.The results show that the inner layer produces more small molecular chains and oxygen-containing groups in the high-strength test condition.The medium layer insulation has a certain oxidative degradation,but the crystalline structure is still improved after the moderate condition.The crystalline form of the outer layer insulation has been improved under the equivalent testing condition.Therefore,it is expected that the rest of retired cables still have the potential to reuse in long-term actual operation condition.