The Growth of Electrical Trees and Partial Discharge Characteristics at the Interlayer Insulation Interface of Epoxy Resin
Ma Xianwei1, Shang Yingqiang1, Zhao Yang1, Song Jianhong2, Lü Zepeng2
1. State Grid Beijing Electric Power Company Beijing 100031 China; 2. State Key Laboratory of Electrical Insulation and Power Equipment Xi'an Jiaotong University Xi'an 710049 China
Abstract：With the increasingly widespread and in-depth application of power electronics technology, the requirements for power density, efficiency, and cost of power electronic devices are also constantly increasing. The insulation performance of traditional materials has become increasingly difficult to meet the needs. The partial discharge (PD) and electrical tree of epoxy resin under the electric-thermal environment are important factors that restrict the safe and stable operation of equipment, and the study of the PD characteristics during the growth process of electrical tree is particularly important. At present, there is a relative lack of research on the characteristics of electrical tree and PD in epoxy resin multilayer structures. Therefore, this paper uses epoxy encapsulated printed circuit boards (PCBs) as multilayer samples to study the characteristics of electrical tree growth and PD on V-shaped electrodes at the interface between epoxy resin and PCB. Firstly, a sample was designed with a bottom made of copper-clad laminate, electrodes made of copper wire, and an upper layer made of epoxy encapsulation. The electrode structure adopted a V-shaped design to facilitate the growth of electrical trees. The PD and changes in the morphology of the electrical tree were recorded until the sample breakdown at 12 kV. The typical phase-resolved partial discharge (PRPD) patterns of electrical tree at different stages of growth process were analyzed. By analyzing the trend in applied voltage difference between adjacent PDs in the partial discharge sequence, it was found that the voltage difference plots of electrical tree changed from a rhombus shape to a double hooked hexagonal shape during the growth process. Based on the characteristics of non-conductive electrical trees, it was found that the change in needle tip potential corresponds to the change from the PD extinction electric field to the PD inception electric field in the electric tree. A method was proposed for estimating the partial discharge inception voltage (VI) and extinction voltage (VX) based on the voltage difference of PD. Furthermore, by comparing the length of non-conductive electrical tree, l, with the difference between the VI and VX, as well as the maximum magnitude of partial discharge, Q, it was found that Q and l and VI -VX are approximately linear. Considering the partial discharge propagation characteristics of non-conductive electrical tree, the relationship between PD propagation length and partial discharge magnitude was obtained by analyzing the electric field and potential distribution of the tree before and after PDs take place. Due to the randomness of the PD in the electrical tree, the propagation path of each discharge is also different, and each partial discharge cannot cover all the branches. Therefore, the maximum discharge propagation length can be equal to, but is more likely to be less than, the total length of the electric tree. Specifically, the following conclusions can be drawn: (1) At lower voltages, the electrical tree and discharge characteristics in PCB and epoxy encapsulation are similar to those of needle plate electrodes. Through partial discharge pulse sequence analysis, it was found that the VI and VX of the electrical tree growth process decreased overall, with fluctuations in the middle. (2) In the early stage of electric tree growth, there is a linear relationship between discharge magnitude, VI -VX, and electrical tree length. The ratio of partial discharge magnitude to VI -VX and electrical tree length is approximately equal to a constant, close to πε0. (3) A narrow channel partial discharge model based on non-conductive electrical tree is used to explain the linear relationship between partial discharge magnitude, VI -VX, and electrical tree length.
马宪伟, 尚英强, 赵洋, 宋剑虹, 吕泽鹏. 环氧树脂层间绝缘界面电树枝生长与局部放电特性[J]. 电工技术学报, 2025, 40(21): 6894-6904.
Ma Xianwei, Shang Yingqiang, Zhao Yang, Song Jianhong, Lü Zepeng. The Growth of Electrical Trees and Partial Discharge Characteristics at the Interlayer Insulation Interface of Epoxy Resin. Transactions of China Electrotechnical Society, 2025, 40(21): 6894-6904.
[1] 盛况, 董泽政, 吴新科. 碳化硅功率器件封装关键技术综述及展望[J]. 中国电机工程学报, 2019, 39(19): 5576-5584, 5885. Sheng Kuang, Dong Zezheng, Wu Xinke.Review and prospect of key packaging technologies for silicon carbide power devices[J]. Proceedings of the CSEE, 2019, 39(19): 5576-5584, 5885. [2] 王来利, 赵成, 张彤宇, 等. 碳化硅功率模块封装技术综述[J]. 电工技术学报, 2023, 38(18): 4947-4962. Wang Laili, Zhao Cheng, Zhang Tongyu, et al.Review of packaging technology for silicon carbide power modules[J]. Transactions of China Electrotechnical Society, 2023, 38(18): 4947-4962. [3] Tanaka T.Charge transfer and tree initiation in polyethylene subjected to AC voltage stress[J]. IEEE Transactions on Electrical Insulation, 1992, 27(3): 424-431. [4] Tanaka T, Greenwood A. Effects of charge injection and extraction on tree initiation in polyethylene[J]. IEEE Transactions on Power Apparatus and Systems, 1978, PAS-97(5): 1749-1759. [5] Laurent C, Mayoux C, Noel S.Mechanisms of electroluminescence during aging of polyethylene[J]. Journal of Applied Physics, 1985, 58(11): 4346-4353. [6] Sekii Y, Maruta K, Okada T.The effect of inclusions in XLPE insulations on electrical trees generated by AC and grounded DC voltage[C]//Proceedings of the 1998 IEEE 6th International Conference on Conduction and Breakdown in Solid Dielectrics, Vasteras, Sweden, 1998: 317-320. [7] Stark K H, Garton C G.Electric strength of irradiated polythene[J]. Nature, 1955, 176(4495): 1225-1226. [8] Auckland D W, Taha A, Varlow B R.Correlation of mechanical properties with electrical treeing behaviour at elevated temperatures[C]//Proceedings of IEEE Conference on Electrical Insulation and Dielectric Phenomena-(CEIDP '93), Pocono Manor, PA, USA, 1993: 636-641. [9] Auckland D W. Mechanical aspects of electrical treeing[C]//IEE Colloquium on The Mechanical Influence on Electrical Insulation Performance, London, UK, 1995: 7/1-7/3. [10] 郑书生, 张宗衡, 孔举, 等. 电树枝起树后电压幅值对生长形貌和局部放电特性的影响[J]. 绝缘材料, 2023, 56(3): 70-76. Zheng Shusheng, Zhang Zongheng, Kong Ju, et al.Effect of voltage amplitude on growth morphology and partial discharge characteristics of electrical tree[J]. Insulating Materials, 2023, 56(3): 70-76. [11] 陈向荣, 洪泽林, 朱光宇, 等. 高温下电压稳定剂对交联聚乙烯电树枝化及局部放电特性的影响[J]. 电工技术学报, 2023, 38(3): 577-586. Chen Xiangrong, Hong Zelin, Zhu Guangyu, et al.Effect of voltage stabilizer on electrical treeing and partial discharge characteristics of crosslinked poly- ethylene at high temperature[J]. Transactions of China Electrotechnical Society, 2023, 38(3): 577-586. [12] 张雯嘉, 王伟, 袁浩, 等. 接枝聚丙烯电缆绝缘材料的电树枝特性及机理[J]. 电工技术学报, 2024, 39(1): 88-98. Zhang Wenjia, Wang Wei, Yuan Hao, et al.Electrical tree characteristics and mechanism of grafted poly- propylene cable insulation[J]. Transactions of China Electrotechnical Society, 2024, 39(1): 88-98. [13] 程子霞, 邢威威, 张云霄, 等. 纳米MgO/环氧树脂复合材料的陷阱特性及对电树枝特性的影响研究[J]. 电工技术学报, 2022, 37(21): 5562-5569. Cheng Zixia, Xing Weiwei, Zhang Yunxiao, et al.Study on trap properties of nano-MgO/epoxy resin composites and its influence on electrical tree properties[J]. Transactions of China Electrotechnical Society, 2022, 37(21): 5562-5569. [14] Du Boxue, Liu Yong, Liu H J.Effects of low pressure on tracking failure of printed circuit boards[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2008, 15(5): 1379-1384. [15] Du Boxue, Liu Yong, Gao Yu.Discharge inception on printed circuit board in an artificial fog[C]//The 17th Annual Meeting of the IEEE Lasers and Electro- Optics Society, Boulder, CO, USA, 2004: 555-558. [16] Meng Guodong, Cheng Yonghong, Song Jianrui, et al.Breakdown characteristics of PCB paralleled traces injected by rectangular pulse[C]//Proceedings of 2011 International Symposium on Electrical Insulating Materials, Kyoto, Japan, 2011: 144-147. [17] 李进, 赵仁勇, 陈允, 等. 水分含量影响玻璃纤维增强环氧树脂电树枝生长特性研究[J]. 电工技术学报, 2023, 38(5): 1166-1176, 1189. Li Jin, Zhao Renyong, Chen Yun, et al.Effects of moisture contents on electrical treeing process in glass fiber reinforced epoxy resin[J]. Transactions of China Electrotechnical Society, 2023, 38(5): 1166-1176, 1189. [18] 王旗, 李喆, 尹毅, 等. 微/纳米氧化铝/环氧树脂复合材料抑制电树枝生长能力的研究[J]. 电工技术学报, 2015, 30(6): 255-260. Wang Qi, Li Zhe, Yin Yi, et al.The effect of micro and nano alumina on the ability of impedance on the electrical tree of epoxy resin[J]. Transactions of China Electrotechnical Society, 2015, 30(6): 255-260. [19] 杨国清, 刘庚, 王德意, 等. 超支化聚酯改性纳米SiO2/环氧树脂的电树枝生长特性[J]. 电工技术学报, 2020, 35(20): 4415-4422. Yang Guoqing, Liu Geng, Wang Deyi, et al.Growth characteristics of electric tree for nano-SiO2/epoxy resin modified by hyperbranched polyester[J]. Trans- actions of China Electrotechnical Society, 2020, 35(20): 4415-4422. [20] Zeynali E, Bridges R, Kordi B.Electrical insulation of conformally coated printed circuit boards: an overview and a study of the influence of pollution[J]. IEEE Electrical Insulation Magazine, 2021, 37(2): 6-17. [21] 程金金, 李学宝, 李超, 等. 正极性重复方波电压下有机硅凝胶内局部放电起始特性及影响因素研究[J]. 高压电器, 2024, 60(10): 183-190. Cheng Jinjin, Li Xuebao, Li Chao, et al.Inception characteristics and influence factors of partial discharge in silicone gel under positive polarity repetitive square wave voltage[J]. High Voltage Apparatus, 2024, 60(10): 183-190. [22] Nakamura S, Kumada A, Hidaka K, et al.Effects of temperature on electrical treeing and partial discharges in epoxy/silica nanocomposites[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2020, 27(4): 1169-1177. [23] Wang Yongqiang, Feng Changhui, Luo Yu.The development of electrical tree discharge in epoxy resin impregnated paper insulation[J]. IEEE Access, 2020, 8: 69522-69531. [24] Lv Zepeng, Rowland S M, Chen Siyuan, et al.Evolution of partial discharges during early tree propagation in epoxy resin[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2017, 24(5): 2995-3003. [25] Lv Zepeng, Rowland S M, Chen Siyuan, et al.Modelling and simulation of PD characteristics in non- conductive electrical trees[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2018, 25(6): 2250-2258. [26] Wu Kai, Suzuoki Y, Mizutani T, et al.A novel physical model for partial discharge in narrow channels[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 1999, 6(2): 181-190. [27] Lv Zepeng, Rowland S M, Chen Siyuan, et al.Modelling of partial discharge characteristics in electrical tree channels: Estimating the PD inception and extinction voltages[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2018, 25(5): 1999-2010. [28] Suwarno, Suzuoki Y, Komori F, et al. Partial discharges due to electrical treeing in polymers: phase- resolved and time-sequence observation and analysis[J]. Journal of Physics D: Applied Physics, 1996, 29(11): 2922-2931.
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