Wang Haoyue, Sun Maolun, Zhao Kaijie, Wang Xiaowei, Xu Qilong, Wang Wei, Li Chengrong
State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China.
State Grid Shandong Electric Power Company, Heze 274000, China.
Polymers (Basel). 2022 Aug 27;14(17):3519. doi: 10.3390/polym14173519.
This paper aims to investigate the influence of thermal aging on a crosslinked polyethylene (XLPE) cable, and the relationships between the macroscopical high-voltage dielectric and the microscopical physicochemical properties are also elucidated. To better simulate thermal aging under working condition, the medium-voltage-level cable is subjected to accelerated inner thermal aging for different aging times. Then, high-voltage frequency domain spectroscopy (FDS) (cable sample) and analyses of microscopic physical and chemical properties (sampling from the cable), including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and elongation at the break (EAB), are conducted at different cable aging stages. The dielectric test results show that after a certain aging time, the high-voltage FDS curves of the cable have layered characteristics, and this phenomenon is more obvious as the aging degree increases. Moreover, the slope and the integral of the high-voltage FDS curves rise with aging time. The mechanism is deduced by the physicochemical results that thermo-oxidative aging results in increasing polar groups and dislocation defects in the crystal region, which leads to the above phenomenon. On the one hand, the appearance of polar groups increases the density of the dipole. On the other hand, the destruction of the crystal region increases the probability and amplitude of dipole reversal. In addition, the breaking of molecular bonds and the increase in the amorphous phase also reduce the rigidity of the XLPE molecular main chain. The above factors lead to obvious delamination and larger dielectric parameters of the thermally aged cable. Finally, according to the experimental results, an on-site diagnosis method of cable insulation thermal aging based on high-voltage FDS is discussed.
本文旨在研究热老化对交联聚乙烯（XLPE）电缆的影响，并阐明宏观高压介电性能与微观物理化学性质之间的关系。为了更好地模拟工作条件下的热老化，对中压等级电缆进行不同老化时间的加速内热老化。然后，在电缆的不同老化阶段进行高压频域光谱法（FDS）（电缆样品）以及微观物理和化学性质分析（从电缆取样），包括傅里叶变换红外光谱法（FTIR）、X射线衍射（XRD）和断裂伸长率（EAB）。介电测试结果表明，经过一定老化时间后，电缆的高压FDS曲线具有分层特征，且随着老化程度的增加，这种现象更加明显。此外，高压FDS曲线的斜率和积分随老化时间上升。通过物理化学结果推断其机理为热氧化老化导致晶体区域极性基团增加和位错缺陷增多，从而引发上述现象。一方面，极性基团的出现增加了偶极子密度。另一方面，晶体区域的破坏增加了偶极子反转的概率和幅度。此外，分子键的断裂和非晶相的增加也降低了XLPE分子主链的刚性。上述因素导致热老化电缆出现明显分层且介电参数增大。最后，根据实验结果，讨论了基于高压FDS的电缆绝缘热老化现场诊断方法。
