电热协同老化应力下环氧树脂复合材料沿面闪络特性与数值模拟

doi:10.19595/j.cnki.1000-6753.tces.240904

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摘要干式变压器正在向高电压等级、高功率密度方向发展,长期运行于电热协同等多应力复杂工况下的环氧树脂浇注绝缘更易诱发沿面闪络故障。为研究电热协同老化应力下环氧树脂的沿面闪络特性,该文搭建了交流沿面闪络实验平台,实验发现当老化温度为160℃时,老化80天的环氧树脂试样闪络场强为2.11 kV/mm,下降了25.7%。进一步地,结合带电粒子连续性方程、平均电子能量方程和界面反应表征式建立了环氧树脂沿面闪络等离子体模型,实现了工频下沿面闪络的动态模拟。根据老化实验结果引入随机函数改变介质表面粗糙度,并结合老化后的介电常数模拟环氧树脂准确的电热老化行为,得到了老化前后环氧树脂闪络过程中切向电场强度、电子密度和表面电荷密度的时空演化规律。仿真结果表明,老化环氧树脂闪络发展过程中电子密度和表面电荷密度均增大,12 ns时流注头部电场强度达到1.183 kV/mm,增加近10.87%,且老化会引起闪络演化速度更快。最后,通过表面电荷消散实验对其进行机理解释,发现老化试样表面电荷消散速率明显减弱,深陷阱能级和密度均增大,分别达到1.06 eV和2.56×10¹⁶ eV^-1·m^-3,导致材料表面电荷大量积聚,最终造成闪络场强下降。上述研究结果可为干式变压器故障运维及寿命预测提供理论和方法基础。

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关键词 ：环氧树脂, 电热联合老化, 沿面闪络, 等离子体, 表面陷阱

Abstract：Dry-type transformer is to high voltage level, high power density direction, long-term operation in the electro-thermal cooperative multi-stress complex working conditions such as epoxy resin casting insulation is more likely to induce along the surface flashover failure. In order to study the characteristics of epoxy resin along the surface flashover under the stress of electro-thermal cooperative aging, this paper builds a platform for flashover along the surface under AC stress, and it is found that when the aging temperature is 160℃, the flashover field strength of the epoxy resin specimen aged for 80 days is 2.11 kV/mm, which is a decrease of 25.7%. The steepest decrease in the field strength along the surface is found from 0 to 40 days, which is related to the rapid increase in the surface roughness of the specimen from 0 to 40 days.
A plasma model of epoxy resin flashover along the surface is established by combining the continuity equation of charged particles, the average electron energy equation and the interfacial reaction characterization equation, and the dynamic simulation of flashover along the surface at the working frequency is realized. According to the results of the aging experiment, a random function is introduced to change the surface roughness of the medium, and the dielectric constant after aging is combined to simulate the accurate electro-thermal aging behavior of the epoxy resin, and the temporal and spatial evolution laws of the tangential electric field strength, electron density and surface charge density of the epoxy resin in the process of flashover before and after aging are obtained. The simulation results show that the electron density and surface charge density increase during the flashover development of the aging epoxy resin, and the electric field strength at the head of the flow injection reaches 1.183 kV/mm at 12 ns, an increase of nearly 10.87%. With the aging specimen due to the roughness and dielectric constant increase, its surface charge density will occur surge phenomenon, compared with the aging specimen before the increase of 57.66%, so that the electron density quickly reached the threshold value of the electron collapse to flow injection, resulting in the development of the flashover becomes faster.
The mechanism of combined electro-thermal aging on the surface charge of epoxy resin specimens is explained by the trap effect, and the reason for the decrease in the flash field strength of the specimens is clarified. For the specimen aged for 80 days, the deep trap density and energy level increase to 2.56×10¹⁶ eV^-1·m^-3 and 1.06 eV, respectively, resulting in an increase in the probability of charge entry trapping, which leads to a large amount of surface charge accumulation, and the electric field distortion becomes more serious, thus decreasing the flash-coincidence field strength along the surface. The above findings provide theoretical and methodological basis for the fault operation and maintenance and life prediction of dry-type transformers.

Key words： Epoxy resin electrothermal joint aging flashover along the surface plasma surface traps

收稿日期: 2024-05-28

PACS:

TM855

基金资助:国家自然科学基金（52177147, 52127812）、北京市自然科学基金（3232053）、国家重点研发计划（2021YFB2601404）和中央高校基本科研业务费专项资金（2023JC005）资助项目

通讯作者: 李庆民男,1968年生,教授,博士生导师,研究方向为高电压与绝缘技术、放电物理等。E-mail：lqmeee@ncepu.edu.cn

作者简介: 李思庚男,1997年生,硕士研究生,研究方向为绝缘设备寿命预测与老化状态评估。E-mail：1476624240@qq.com

引用本文:

李思庚, 李庆民, 王伟, 金虎, 李锐海. 电热协同老化应力下环氧树脂复合材料沿面闪络特性与数值模拟[J]. 电工技术学报, 2025, 40(13): 4045-4057. Li Sigeng, Li Qingmin, Wang Wei, Jin Hu, Li Ruihai. Characterization and Numerical Simulation of Epoxy Resin Composites Flashed along the Surface under Electro-Thermal Co-Aging Stresses. Transactions of China Electrotechnical Society, 2025, 40(13): 4045-4057.

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