Analysis of the Hazard of Interface Defects in Epoxy Encapsulation Insulation under Sustained Voltage
Wang Tengteng1, Li Xudong2, Zhou Qinyu1, Liu Runyu1, Ren Ming1
1. State Key Laboratory of Electrical Insulation and Power Equipment Xi’an Jiaotong University Xi’an 710049 China; 2. Institute of Electronic Engineering China Academy of Engineering Physics Mianyang 621000 China
Abstract：Epoxy resin is widely used in the manufacturing of insulation components for various power equipment due to its excellent properties. Currently, the vacuum degassing process is usually adopted to avoid air gaps. However, some tiny defects still cannot be totally avoided. Partial discharge (PD) generated at internal defects in materials is a common cause of insulation failure in epoxy-potted power equipment. It should be noted that the appearance of PD signals does not necessarily mean that the equipment has lost its normal operation capability. However, traditional PD diagnostic techniques often fail to precisely evaluate the insulation hazard level caused by discharge activities. In response to this situation, this article deeply explores the discharge intensity development speed of three epoxy resin micro-defects under continuous PD. Based on the differences in the discharge intensity development speed, the hazard levels of different defects to the insulation are classified. Firstly, a new method for preparing epoxy potting defects, including bubble, crack, and delamination defects, was adopted. The simulated defects prepared by this method were very similar to the actual defects in terms of defect scale and other aspects. The method for assessing the hazard level of defects was as follows: First, compare whether there are macroscopic changes in the defect samples before and after the experiment; Second, analyze the variation of the discharge intensity over time. Three parameters, namely maximum discharge magnitude, discharge frequency, and average discharge magnitude, were selected as quantitative indicators to assess PD intensity. It was found that the crack defect samples exhibited dielectric breakdown within 30 minutes under sustained AC voltage. However, both bubble and delamination defect samples showed no significant macroscopic changes after 150 minutes of continuous voltage application. The relationship between discharge intensity and time was statistically analyzed, and the results showed that under sustained AC voltage, the discharge intensity of bubble defects weakened with time, while that of the delamination defects strengthened with time. Moreover, it was observed that the discharge intensity of some bubble defects first weakened and then basically stabilized, whereas that of another group of bubble defects gradually weakened until it disappeared. Therefore, semi-enclosed bubble defect samples were prepared for research. Based on the discharge sustainability, the hazard level of bubble defects to insulation could be further classified. The following conclusions can be drawn from the experiment analysis: (1) Under sustained AC voltage, significant macroscopic changes are observed in the crack defects before and after the experiment, whereas the bubble and delamination defects exhibit no comparable macroscopic variations. Therefore, the hazard level of the crack defect is higher than that of the bubble and delamination defects. (2) Under sustained AC voltage, the discharge intensity of the delamination defect shows an increasing trend with time. By contrast, the bubble defect demonstrates a gradual attenuation in discharge intensity over time. Therefore, the hazard level of the delamination defect is higher than that of the bubble defect. (3) Continuous PD will suppress the natural ionization of the gas inside the defect, which may lead to the disappearance of the discharge signal. Based on the continuity of discharge, the hazard level of the bubble defect can be further classified. That is, bubble defects with persistent discharge are more hazardous than those with non-persistent discharge.
王腾腾, 李旭东, 周沁昱, 刘润宇, 任明. 持续电压下环氧灌封绝缘界面缺陷危害性分析[J]. 电工技术学报, 2026, 41(7): 2510-2520.
Wang Tengteng, Li Xudong, Zhou Qinyu, Liu Runyu, Ren Ming. Analysis of the Hazard of Interface Defects in Epoxy Encapsulation Insulation under Sustained Voltage. Transactions of China Electrotechnical Society, 2026, 41(7): 2510-2520.
[1] 刘贺晨, 刘畅, 孙章林, 等. 热氧老化对基于双重动态共价键的可降解树脂性能的影响[J]. 电工技术学报, 2025, 40(9): 2944-2957. Liu Hechen, Liu Chang, Sun Zhanglin, et al.The effect of thermal oxygen aging on the properties of degradable resin based on dual-dynamic bonds[J]. Transactions of China Electrotechnical Society, 2025, 40(9): 2944-2957. [2] 刘云鹏, 黎馨阳, 刘贺晨, 等. 基于亚胺键的香草醛基可降解环氧树脂综合性能研究[J]. 电工技术学报, 2025, 40(7): 2267-2281. Liu Yunpeng, Li Xinyang, Liu Hechen, et al.Comprehensive performance study of vanillin-based degradable epoxy resin based on imine bonding[J]. Transactions of China Electrotechnical Society, 2025, 40(7): 2267-2281. [3] 韩锦春, 李禹锋. 电压波动条件下环氧树脂内部局部放电特性研究[J]. 绝缘材料, 2024, 57(1): 80-86. Han Jinchun, Li Yufeng.Study on internal partial discharge characteristics of epoxy resin under voltage fluctuation[J]. Insulating Materials, 2024, 57(1): 80-86. [4] Gui Lu, Mi Yan, Deng Shengchu, et al.Partial discharge characteristics of an air gap defect in the epoxy resin of a saturable reactor under an exponential decay pulse voltage[J]. High Voltage, 2020, 5(4): 482-488. [5] 何宁辉, 李秀广, 周秀, 等. GIS固体绝缘不同类型气隙缺陷的放电特征[J]. 高电压技术, 2021, 47(6): 2073-2083. He Ninghui, Li Xiuguang, Zhou Xiu, et al.Discharge characteristics of different types of void defects of solid insulation of GIS[J]. High Voltage Engineering, 2021, 47(6): 2073-2083. [6] Rodríguez-Serna J M, Albarracín-Sánchez R, Dong Ming, et al. Computer simulation of partial discharges in voids inside epoxy resins using three-capacitance and analytical models[J]. Polymers, 2020, 12(1): 77. [7] Wu Zehua, Tian Huidong, Zhu Sijia, et al.In-situ observation of electrical tree evolution in epoxy dielectrics with internal cracks[J]. High Voltage, 2021, 6(2): 210-218. [8] 刘智鹏, 魏来, 李庆民, 等. GIL支柱绝缘子嵌件-环氧界面缺陷演化过程与放电脆裂机制[J]. 高电压技术, 2024, 50(1): 359-369. Liu Zhipeng, Wei Lai, Li Qingmin, et al.Defects evolution process and mechanism of discharge embrittlement of GIL post insulator inserts and epoxy interface[J]. High Voltage Engineering, 2024, 50(1): 359-369. [9] 杜伯学, 张莹, 孔晓晓, 等. 环氧树脂绝缘电树枝劣化研究进展[J]. 电工技术学报, 2022, 37(5): 1128-1135, 1157. Du Boxue, Zhang Ying, Kong Xiaoxiao, et al.Research progress on electrical tree in epoxy resin insulation[J]. Transactions of China Electrotechnical Society, 2022, 37(5): 1128-1135, 1157. [10] 张志斌, 任明, 宋波, 等. 冷绝缘超导电缆终端用环氧玻璃钢材料绝缘劣化机制研究[J]. 中国电机工程学报, 2022, 42(5): 1690-1701. Zhang Zhibin, Ren Ming, Song Bo, et al.Insulation deterioration mechanism of glass fiber reinforced plastic used in cold dielectric superconducting cable terminal[J]. Proceedings of the CSEE, 2022, 42(5): 1690-1701. [11] 唐志国, 李阳. 恒压下GIS固体绝缘界面气隙缺陷放电严重程度评估[J]. 高压电器, 2024, 60(2): 62-68, 77. Tang Zhiguo, Li Yang.Severity assessment of air gap defect discharge at GIS solid insulation interface under constant voltage[J]. High Voltage Apparatus, 2024, 60(2): 62-68, 77. [12] 周俊杰, 吴治诚, 张乔根, 等. 油纸绝缘层间气泡局部放电演化特性[J]. 高电压技术, 2024, 50(5): 2217-2224. Zhou Junjie, Wu Zhicheng, Zhang Qiaogen, et al.Evolution characteristics of bubble partial discharge between oil paper insulation layers[J]. High Voltage Engineering, 2024, 50(5): 2217-2224. [13] Suriani M J, Rapi H Z, Ilyas R A, et al.Delamination and manufacturing defects in natural fiber-reinforced hybrid composite: a review[J]. Polymers, 2021, 13(8): 1323. [14] Otake Y, Umemoto T, Suga K I, et al.Influence of defect size on insulation deterioration of epoxy resins with voids[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2021, 28(1): 52-57. [15] 王伟, 李贝, 王健, 等. 基于热解动力学的有机硅凝胶封装绝缘剩余寿命评估方法[J]. 电工技术学报, 2025, 40(7): 2295-2305. Wang Wei, Li Bei, Wang Jian, et al.Remaining life assessment of silicone gel package insulation based on pyrolysis kinetics[J]. Transactions of China Electro-technical Society, 2025, 40(7): 2295-2305. [16] 蒋起航, 王威望, 钟禹, 等. 环氧树脂高频松弛的交流电导与双极性方波击穿特性[J]. 电工技术学报, 2024, 39(4): 1159-1171. Jiang Qihang, Wang Weiwang, Zhong Yu, et al.AC conductivity with high frequency relaxation and breakdown characteristics of epoxy resin under bipolar square wave voltage[J]. Transactions of China Electrotechnical Society, 2024, 39(4): 1159-1171. [17] 汲胜昌, 赵德华, 贾云飞, 等. 变压器绝缘缺陷放电发展特性及检测方法研究现状及展望[J]. 高电压技术, 2024, 50(10): 4297-4314. Ji Shengchang, Zhao Dehua, Jia Yunfei, et al.Research status and prospects of development characteristics and detection methods of transformer insulation defect discharge[J]. High Voltage Engineering, 2024, 50(10): 4297-4314. [18] 任明, 夏昌杰, 余家赫, 等. 绝缘子沿面放电多光谱脉冲演化特性及诊断方法[J]. 电工技术学报, 2023, 38(3): 806-817. Ren Ming, Xia Changjie, Yu Jiahe, et al.Multispectral pulse evolution laws of insulator surface discharges and its diagnosis approach[J]. Transactions of China Electrotechnical Society, 2023, 38(3): 806-817. [19] 郑书生, 孔举, 戴敏婷, 等. X射线激励XLPE电缆终端金属颗粒局部放电的研究[J]. 电工技术学报, 2025, 40(3): 913-927. Zheng Shusheng, Kong Ju, Dai Minting, et al.Study on partial discharge of metal particles in XLPE cable terminal excited by X-ray[J]. Transactions of China Electrotechnical Society, 2025, 40(3): 913-927. [20] 赵心毅, 周文凯, 李传扬, 等. 开关柜用环氧树脂绝缘表面的凝露放电特性研究[J]. 绝缘材料, 2024, 57(12): 98-107. Zhao Xinyi, Zhou Wenkai, Li Chuanyang, et al.Research on condensation discharge characteristics on surface of epoxy resin insulation for switchgears[J]. Insulating Materials, 2024, 57(12): 98-107. [21] Ren Ming, Zhang Chongxing, Dong Ming, et al.Fault prediction of gas-insulated system with hypersensitive optical monitoring and spectral information[J]. International Journal of Electrical Power & Energy Systems, 2020, 119: 105945. [22] Suzuki H, Sato M, Kumada A, et al.Prediction of impulse breakdown voltage in dry air at high pressure using volume-time theory[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2022, 29(4): 1251-1258. [23] Pancheshnyi S.Effective ionization rate in nitrogen-oxygen mixtures[J]. Journal of Physics D: Applied Physics, 2013, 46(15): 155201. [24] 尚星宇, 庞磊, 卜钦浩, 等. 温度对方波电压下环氧树脂局部放电及击穿特性的影响[J]. 高电压技术, 2023, 49(8): 3286-3295. Shang Xingyu, Pang Lei, Bu Qinhao, et al.Effect of temperature on partial discharge and breakdown characteristics of epoxy resin under square wave voltage[J]. High Voltage Engineering, 2023, 49(8): 3286-3295. [25] Shang Xingyu, Pang Lei, Bu Qinhao, et al.Thermal runaway and induced electrical failure of epoxy resin in high-frequency transformers: Insulation design reference[J]. High Voltage, 2024, 9(5): 989-1000. [26] Hayakawa N, Shimizu F, Okubo H.Estimation of partial discharge inception voltage of magnet wires under inverter surge voltage by volume-time theory[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2012, 19(2): 550-557. [27] 杨帆, 张玉琛, 王鹏博, 等. 电容屏破损缺陷局部放电过程规律特征及仿真分析[J]. 电工技术学报, 2024, 39(9): 2860-2872. Yang Fan, Zhang Yuchen, Wang Pengbo, et al.Characteristics and simulation analysis of partial discharge process of condenser foil layer defect[J]. Transactions of China Electrotechnical Society, 2024, 39(9): 2860-2872. [28] 康永强, 王兆赟, 党露芝, 等. 低气压条件下IGBT模块局部放电特性及机理研究[J]. 电网技术, 2024, 48(10): 4406-4416. Kang Yongqiang, Wang Zhaoyun, Dang Luzhi, et al.Research on partial discharge characteristics and mechanisms of IGBT modules under low pressure conditions[J]. Power System Technology, 2024, 48(10): 4406-4416.
2026, Vol. 41 
