摘要
换流变压器的油纸绝缘系统处于强机械振动与热老化的综合作用环境中,其绝缘纸的劣化特性尚未引起足够重视。为研究机-热老化对绝缘纸机械性能劣化的协同作用,文中设计了高温振动老化箱,在130℃时添加频率为10Hz,振幅分别为0、1.99mm和2.64mm的加速老化试验,并对试品依次进行了抗拉强度测试、X射线衍射和扫描电镜分析以及聚合度测量。研究结果表明,机-热效应对绝缘纸机械性能劣化的促进作用显著高于热老化,且振幅越高,绝缘纸抗拉强度及聚合度的下降越明显。纤维素大分子链的取向使得纤维素的轴向机械强度远优于其径向机械强度,而外施力沿垂直于绝缘纸表面的分量大于平行于绝缘纸表面的分量,两因素共同加速机-热协同老化作用下绝缘纸机械性能的劣化。XRD和SEM分析显示,机-热协同老化使得绝缘纸微观结构中纤维的相对结晶度和晶粒尺寸变小,而微晶类型没有改变。同时,机-热协同作用促进了纤维的细化、分叉和断裂以及孔洞的出现、增加与发展,诸因素对绝缘纸机械性能的劣化共同起着促进作用。本研究可为分析换流变绝缘纸机-热综合作用下的劣化机理提供参考作用。
Oil-paper insulation system of converter transformer lies in a combination environment under which strong mechanical vibration and thermal are coupling, but the deterioration characteristics of insulation paper has not been paid enough attention. To study the mechanical-thermal synergy on the deterioration of insulation paper mechanical properties, thermal-vibration ageing box was designed. A series of accelerated ageing experiments were carried out under conditions of 130℃ thermal aging, added with vibration amplitude of 0, 1.99 mm and 2.64 mm at frequency 10 Hz, and ageing duration was 48 h, 96 h and 144 h respectively. The tensile strength(TS), X-ray diffraction(XRD) and scanning electron microscopy(SEM) analysis and the degree of polymerization(DP) were measured for the specimen. The results show that the promotion of mechanical-thermal synergy is sharper than that of thermal ageing, and the higher the amplitude, the more obvious the decrease of TS and DP of the insulation paper. Orientation of cellulose macromolecule chain makes the fiber axial mechanical strength is far superior to the radial one, and the perpendicular component of the applied force is higher than the one along to the surface of the insulation paper, the above two factors play a key synergy role to accelerate the deterioration of the insulation paper mechanical properties. XRD and SEM analysis indicate that, from a microstructure point, the relative crystallinity and microcrystal size of the cellulose fiber become smaller, whichindicates the type of microcrystalline doesn’t change with ageing conditions. At the same time, the phenomena of refinement, bifurcation and breakage of fiber, and appearance, increase and development of holes, were found and they promoted the mechanical properties deterioration of the insulation paper. The study can provide a reference for the deterioration mechanism research of converter transformer insulation paper under the complex mechanical-thermal condition.
作者
李长云
王铮
LI Changyun;WANG Zheng(School of Electrical Engineering and Automation,Qilu University of Technology,250353 Jinan,Shandong Province,China)
出处
《中国电机工程学报》
EI
CSCD
北大核心
2019年第2期612-620,共9页
Proceedings of the CSEE
基金
山东省自然科学基金项目(ZR2017MEE078)
新能源电力系统国家重点实验室开放课题(LAPS17004)
国家自然科学基金(61701270)~~
关键词
换流变压器
机-热协同作用
抗拉伸强度聚合度
微观结构
converter transformer
mechanical-thermal synergy
tensile strength
degree of polymerization
microscopic structure
