摘要
为了研究电缆机械弯曲对其绝缘中水树生长的影响,对不同弯曲程度的交联聚乙烯(XLPE)电缆中的水树生长特性进行了对比分析。采用水针电极老化法,分别对不弯曲、弯曲程度较小和弯曲程度较大的3组电缆样本进行加速水树老化实验。经过28天加速老化后,分别对3组电缆样本进行切片,利用显微镜观察水树形态,并对水树尺寸进行测量统计。同时,结合XPLE材料在机械应力作用下的取向行为,对实验结果进行理论分析。结果表明:随着电缆弯曲程度逐渐增加,其绝缘外侧的水树形态逐渐由半圆形变为圆锥形,并且水树长度和宽度之间的差异逐渐增大。且弯曲程度越大,水树宽度超过长度越多。分析认为当电缆达到一定的弯曲程度时,其绝缘外侧的局部机械拉力将超过XLPE的屈服强度,从而导致材料分子链发生力学取向。取向后材料呈现各向异性,沿取向方向的水树生长将得到促进,而垂直于取向方向的水树生长将受到抑制,从而导致圆锥形水树的出现。
To study the influence of cable mechanical bending on the propagation of water trees in insulation, the propagation characteristics of water trees in XLPE cables with different bending degrees were compared. Accelerated ageing experiments were conducted on unbending cable and bending cables with smaller and greater bending degrees. After ageing for 28 days, the samples were sliced, the morphologies of water trees were observed via optical microscope, and the sizes of water trees were measured. Meanwhile, the experimental results were analyzed based on the mechanical orientation theory of XLPE materials. The results show that with the increase of cable bending degree, the morphology of water trees on the outer side of the samples changes from half round to cone, and the difference between water tree length and width increases gradually. The greater the bending degree of cable, the larger the difference between water tree width and length is. It is considered that when the cable is bent to certain extent, the local strain on the outer side of the insulation would exceed the yield strength of XLPE, which causes the mechanical orientation of molecular chains. After orientation, the material becomes anisotropy, and the water tree propagation along the orientation direction is promoted, while the water tree propagation perpendicular to the orientation is inhibited, which result in the formation of conical water trees.
作者
黄鹤鸣
李康乐
杨明亮
周凯
龚薇
魏艳平
Huang Heming Li Kangle Yang Mingliang Zhou Kai Gong Wei Wei Yanping(State Grid Beijing Electric Power Company, Beijing 100031, China School of Electrical Engineering and Information, Sichuan University, Chengdu 610065, China Ziyang Power Supply Company, State Grid Sichuan Electric Power Company, Ziyang 641300, China)
出处
《绝缘材料》
CAS
北大核心
2017年第10期26-30,共5页
Insulating Materials
基金
国家自然科学基金资助项目(51477106)
关键词
交联聚乙烯
水树
弯曲
分子链
取向
XLPE
water trees
bending
molecular chains
orientation
