热老化对植物油中绝缘纸样频域介电谱的影响

为研究不同绝缘纸样在植物油中的老化行为,对FR3植物油与菱格点胶纸、DPE纸和Nomex纸构成的油纸绝缘组合,在130℃环境中开展人工加速热老化试验,测量绝缘纸在10-1～107 Hz范围内的频域介电谱(FDS),分析FR3植物油中绝缘纸样老化前后的tanδ、复介电常数实部ε′和虚部ε″,利用扫描电子显微镜观察绝缘纸的表面微观结构,并测试各纸样的拉伸强度。结果表明,三种纸样在低频下的介电谱随老化程度延长呈现降低趋势,下降幅度为点胶纸>DPE纸>Nomex纸;热老化破坏绝缘纸紧密的纤维排列结构,使其孔洞、裂纹增多;相同老化时间下DPE纸纤维结构比点胶纸纤维结构的劣化程度低;Nomex比点胶纸和DPE纸抗热老化能力更强,机械强度更稳定。

Effect of Thermal Aging on Frequency Domain Dielectric Spectrum of Insulating Papers in Vegetable Oil

In order to study the aging behavior of different insulating paper samples in vegetable oil,the artificial accelerated heat aging experiment of oiled paper insulation combination of FR3 vegetable oil with Kraft paper,DPE paper and Nomex paper were carried out under temperature of 130℃.The FDS of the insulating paper in the range of 10-1-107 Hz was measured,and the tanδ,the complex dielectric constant real partε′and the imaginary partε″of the insulating paper before and after aging in the FR3 vegetable oil were analyzed.In addition,The surface microstructures of insulating paper were observed by scanning electron microscopy,and the tensile strength of each paper sample was tested.The results show that the dielectric spectra of the three samples at low frequencies show a decreasing trend with the aging degree,and the descend range is sorted as follows:Kraft paper>DPE paper>Nomex paper.The compact fiber arrangement structure of insulating paper was broken during the process of thermal aging,resulting in the increasing of holes and cracks.At the same aging time,the deterioration degree of DPE paper fiber structure is lower than that of Kraft paper.The thermal stability and mechanical strength of Nomex paper was stronger than that of Kraft paper and DPE paper.