介观尺度结晶形貌对XLPE电缆绝缘击穿特性影响研究

Effect of mesoscale crystal morphology on breakdown characteristics of XLPE cable insulation

为了研究XLPE材料的介观尺度结晶形貌对其交流击穿特性的影响并分析其作用机理,通过控制样品在降温结晶过程中的降温速率,制备得到了具有不同结晶形貌的XLPE试样。同时,通过扫描电子显微镜(SEM)和X射线衍射(XRD)对试样的结晶结构与形貌进行了表征和观测,并使用宽频介电谱仪、三电极系统和交流击穿系统对其介电性能进行测试。最后,结合仿真模拟的手段对试验结果进行验证及机理分析。结果表明:减小降温速率可以延长结晶时间,使分子链规则排列堆叠形成大尺寸球晶,晶区面积占比较高且结构相对完善。结晶结构的完善使XLPE试样的相对介电常数小幅上升,电导率降低,击穿强度及其稳定性显著提升。仿真与试验结果相一致,介观尺度下试样内部完善的结晶形貌降低了球晶间的电场畸变程度,抑制了局部放电与击穿的发生。

In order to study the effect of mesoscale crystal morphology of XLPE material on its AC breakdown characteristics and analyze its mechanism,XLPE samples with different crystal morphologies were prepared by controlling the cooling rate of samples during cooling crystallization.At the same time,the crystalline structure and morphology of the samples were characterized and observed by scanning electron microscope(SEM)and X-ray diffraction(XRD),and its dielectric properties were tested by the broadband dielectric spectrometer,three electrode system,and AC breakdown system.Finally,the test results were verified and the mechanism was analyzed by means of simulation.The results show that decreasing the cooling rate can prolong the crystallization time,making the molecular chains regularly arrange and stack to form large-size spherulites with a relatively high crystal area and relatively perfect structure.The improvement of crystal structure makes the relative dielectric constant of the XLPE sample increase slightly,the conductivity decrease,and the breakdown strength and stability significantly improve.The simulation results are consistent with the test results.The perfect crystal morphology of the sample at mesoscale reduces the degree of electric field distortion between spherulites and inhibits the occurrence of partial discharge and breakdown.