基于极化-去极化电流法的老化PVC电缆绝缘性研究

Insulation Property Researches of Aged PVC Cables by the Polarization-Depolarization Current Method

电缆老化会使绝缘失效,导致短路乃至火灾事故的发生。为研究低压电缆老化后的绝缘性能,对电缆中采用的聚氯乙烯(PVC)绝缘材料进行加速老化实验,通过对样本极化-去极化的电流数据进行分析,得到直流电导率、低频介质损耗因数等参数的变化规律,并利用热失重和傅里叶红外光谱测试老化样本的理化性能。结果表明,随着老化时间的增加,极化电流、去极化电流、电导率和低频介质损耗因数均增大。热失重分析和傅里叶红外光谱分析结果则进一步表明,长时间的高温老化会使PVC电缆绝缘的氯含量减少,阻燃性降低,PVC分子链断裂,羟基、甲基、亚甲基和C=C等官能团含量增加,电缆老化加剧,最终导致电缆的绝缘性下降。

The aging of electrical cables could lead to insulation breakdown,culminating in short circuits and even the occurrence of fire incidents.To investigate the insulating properties of low-voltage cables after aging,accelerated aging experiments were conducted on the polyvinyl chloride(PVC)insulation material used in the cables.Analysis of the polarization-depolarization current data from the samples revealed the change patterns in parameters such as DC conductivity and low-frequency dielectric loss factors.Furthermore,the physicochemical properties of the aged samples were assessed through thermogravimetric analysis and Fourier infrared spectroscopy.The results indicate that with the increase of aging time,there is a notable augmentation observed in parameters including polarization current,depolarization current,conductivity,and low-frequency dielectric loss factor.The thermal gravimetric analysis and Fourier transform infrared spectroscopy results further elucidate that the long-term high-temperature aging reduces the chlorine content of PVC cable insulation,diminishing the flame retardancy and resulting to the fracture of PVC molecular chains.The contents of functional groups such as hydroxyl,methyl,methylene,and carbon-carbon double bonds increase.These alterations exacerbate the cable aging,ultimately decreasing the insulation performances of cables.