Simulation Study on Long Gap Breakdown Characteristics of Natural Ester Under Lightning Shock
Zheng Hanbo1, Yang Hang1, Feng Yongji1, Lü Weijie1, Peng Qingjun2
1. Guangxi Key Laboratory of Intelligent Control and Maintenance of Power Equipment Guangxi University Nanning 530004 China; 2. Electric Power Research Institute of Yunnan Power Grid Corporation Kunming 650200 China
Abstract:Natural ester, which has a greater ignition point and a better rate of biodegradation than conventional dielectric liquid mineral oil, has emerged as a prospective substitute for the former in light of the present green development trend of power grid equipment. It differ from mineral oil in terms of chemical and molecular structure, which impacts how well they insulate. Dielectric breakdown is preceded by streamer in liquid dielectric under high electric field magnitude. Natural ester streamer has a higher propensity to become 3rd mode fast streamer when compared to mineral oil. Natural esters also suffer from the substantial issue of having insufficient lightning shock resistance when working in areas with strong local fields and wide discharge gaps. This paper develops an enhanced model of natural ester streamer to analyze the process underlying the unique breakdown characteristics of natural ester by investigating the streamer development characteristics. First, the continuous medium model of carriers in streamer is used to explain the mechanism of charge generation and capture, and the physical process of streamer development is studied from a microscopic perspective, with special attention to the changes of charge density, electric field magnitude and other parameters during the dynamic process of discharge. Secondly, the ionization potentials of different triglyceride molecules representing natural esters were calculated with the help of density flooding theory (DFT) and wave function analysis. Third, considering the temperature for the carrier mobility in the streamer development, and finally adding the standard lightning impulse voltage simulated by subtracting the two exponential functions, the simulation data of the streamer development of natural esters are calculated. Simulation results for natural esters show that unlike mineral oil, the breakdown voltage and acceleration voltage of natural esters are very close to each other, leading to the easy transition from slow to fast streamer. Discussion of the ionization of different ionized molecules in the development of streamer reveals that in the early stage of development, the ionization of low ionization potential molecules contributes most of the free electrons and positive ions, and the ionization of high ionization potential molecules is limited. And with the increase of voltage, as the ionization potential difference between high and low ionization potential molecules of natural esters is not large, the high ionization potentialy molecules quickly participate in ionization, injecting enough carriers for the 2nd mode streamer, and the streamer completes the transition from the 2nd mode slow streamer to the 3rd mode fast streamer. In long oil gaps, the breakdown voltage of natural esters is much smaller than that of mineral oil. The breakdown of long gaps requires higher voltage, which makes the insulating oil subject to high field magnitude. The difference in ionization potential and other aspects between natural ester and mineral oil intensifies the performance of both in breakdown under different gaps. Since the unique breakdown properties of natural esters are closely related to the ionization potential of molecules, the distribution characteristics of ionization potential and electron affinity energy of natural esters induced by molecular configuration are less studied. Although some studies have been conducted to show the correlation between molecular configuration and electrical properties, only a few features related to molecular structure and the conformational relationship between electronic structure properties and electrical properties have been attempted to explain, and the intrinsic mechanism of molecular structure affecting electrical properties has not been revealed. The future direction should clarify the conformational relationship between the molecular structure and electrical properties of natural esters, use molecular design to improve the electrical properties of natural esters, and expand the application scenarios of natural esters.
郑含博, 杨杭, 凤永吉, 吕伟杰, 彭庆军. 雷电冲击下天然酯的长间隙击穿特性仿真研究[J]. 电工技术学报, 0, (): 72-72.
Zheng Hanbo, Yang Hang, Feng Yongji, Lü Weijie, Peng Qingjun. Simulation Study on Long Gap Breakdown Characteristics of Natural Ester Under Lightning Shock. Transactions of China Electrotechnical Society, 0, (): 72-72.
[1] 崔鲁, 陈伟根, 杜劲超, 等. 植物油-纸绝缘气隙放电形态及发展特征[J]. 电工技术学报, 2018, 33(3): 618-626. Cui Lu, Chen Weigen, Du Jinchao, et al.Investigation on air-gap discharge patterns and development characteristics of vegetable oil-paper insulation[J]. Transactions of China Electrotechnical Society, 2018, 33(3): 618-626. [2] 陈刚, 黄正勇, 段瑜, 等. 基于不同油纸介电常数配比的油纸沿面放电仿真[J]. 电工技术学报, 2020, 35(增刊2): 620-628. Chen Gang, Huang Zhengyong, Duan Yu, et al.Simulation of surface discharge based on the different ratio of dielectric constants of oil and papers[J]. Transactions of China Electrotechnical Society, 2020, 35(S2): 620-628. [3] Lu Wu, Liu Qiang.Effect of cellulose particles on impulse breakdown in ester transformer liquids in uniform electric fields[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2015, 22(5): 2554-2564. [4] 别朝红, 任彦哲, 李更丰, 等. “双碳”目标下城市能源系统的形态结构和发展路径[J]. 电力系统自动化, 2022, 46(17): 3-15. Bie Zhaohong, Ren Yanzhe, Li Gengfeng, et al.Morphological structure and development path of urban energy system for carbon emission peak and carbon neutrality[J]. Automation of Electric Power Systems, 2022, 46(17): 3-15. [5] 张永泽, 唐炬, 潘成, 等. 油流速度对含气泡变压器油击穿特性的影响[J]. 电工技术学报, 2022, 37(2): 479-487. Zhang Yongze, Tang Ju, Pan Cheng, et al.Impact of velocity on breakdown characteristics of transformer oil containing bubbles[J]. Transactions of China Electrotechnical Society, 2022, 37(2): 479-487. [6] Zheng Hanbo, Yang Enchen, Li Xufan, et al.Microscopic reaction mechanisms of formic acid generated during pyrolysis of cellulosic insulating paper[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2021, 28(5): 1661-1668. [7] 陈宝辉, 邓捷, 孙易成, 等. 电场均匀性对细水雾短空气间隙工频放电特性的影响[J]. 电工技术学报, 2021, 36(8): 1734-1742. Chen Baohui, Deng Jie, Sun Yicheng, et al.Influence of electric field uniformity on power frequency discharge characteristics of short air gap in water mist condition[J]. Transactions of China Electrotechnical Society, 2021, 36(8): 1734-1742. [8] 梁苏宁, 李剑, 王飞鹏, 等. 正极性雷电冲击电压下天然酯绝缘油油纸沿面流注动态变化规律研究[J]. 中国电机工程学报, 2021, 41(1): 156-165, 406. Liang Suning, Li Jian, Wang Feipeng, et al.Study on the dynamic characteristics of streamer along the interface surface of natural ester insulating oil-pressboard system under positive lightning impulse voltage[J]. Proceedings of the CSEE, 2021, 41(1): 156-165, 406. [9] Rozga P, Stanek M, Cieslinski D.Comparison of properties of electrical discharges developing in natural and synthetic ester at inception voltage[C]//2013 Annual Report Conference on Electrical Insulation and Dielectric Phenomena, Shenzhen, China, 2014: 891-894. [10] Huang Zhengyong, Chen Xiuping, Li Jian, et al.Streamer characteristics of dielectric natural ester-based liquids under long gap distances[J]. AIP Advances, 2018, 8(10): 105129. [11] 刘毅, 赵勇, 任益佳, 等. 水中大电流脉冲放电电弧通道发展过程分析[J]. 电工技术学报, 2021, 36(16): 3525-3534. Liu Yi, Zhao Yong, Ren Yijia, et al.Analysis on the development process of arc channel for underwater high current pulsed discharge[J]. Transactions of China Electrotechnical Society, 2021, 36(16): 3525-3534. [12] Lesaint O.Prebreakdown phenomena in liquids: propagation ‘modes’ and basic physical properties[J]. Journal of Physics D: Applied Physics, 2016, 49(14): 144001. [13] Liu Qiang, Wang Zhongdong.Streamer characteristic and breakdown in synthetic and natural ester transformer liquids with pressboard interface under lightning impulse voltage[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2011, 18(6): 1908-1917. [14] Rozga P.Streamer propagation in a non-uniform electric field under lightning impulse in short gaps insulated with natural ester and mineral oil[J]. Bulletin of the Polish Academy of Sciences Technical Sciences, 2016, 64(1): 171-179. [15] 冯谟可, 王傲群, 袁帅, 等. 国产化电磁暂态仿真平台发展方向分析及展望[J]. 电力系统自动化, 2022, 46(10): 64-74. Feng Moke, Wang Aoqun, Yuan Shuai, et al.Analysis and prospect of development of China’s independent electromagnetic transient simulation platform[J]. Automation of Electric Power Systems, 2022, 46(10): 64-74. [16] Hwang J G, Zahn M, Pettersson L A A. Mechanisms behind positive streamers and their distinct propagation modes in transformer oil[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2012, 19(1): 162-174. [17] 陈刚, 李剑, 黄正勇, 等. 考虑载流子密度扰动的植物绝缘油中初始流注放电仿真[J]. 中国电机工程学报, 2021, 41(3): 1176-1185. Chen Gang, Li Jian, Huang Zhengyong, et al.Simulation of streamer discharge considering carrier density fluctuation in vegetable insulating oil[J]. Proceedings of the CSEE, 2021, 41(3): 1176-1185. [18] Chen Gang, Li Jian, Huang Zhengyong, et al.Simulation of the effect of carrier density fluctuations on initial streamer branching in natural ester during pulsed positive discharges[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2020, 27(5): 1604-1610. [19] Hwang J W G. Elucidating the mechanisms behind pre-breakdown phenomena in transformer oil systems[D]. Cambridge, MA, USA: Massachusetts Institute of Technology, 2010. [20] O'Sullivan F M.A model for the initiation and propagation of electrical streamers in transformer oil and transformer oil based nanofluids[D]. Cambridge, MA, USA: Massachusetts Institute of Technology, 2007. [21] Vanraes P, Bogaerts A.Plasma physics of liquids—a focused review[J]. Applied Physics Reviews, 2018, 5(3): 031103. [22] 李元, 温嘉烨, 李林波, 等. 液体介质微/纳秒脉冲放电的特性与机理:现状及进展[J]. 强激光与粒子束, 2021, 33(6): 6-18. Li Yuan, Wen Jiaye, Li Linbo, et al.Characteristics and mechanisms of streamer discharge in liquids under micro/nano-second pulsed voltages: status and advances[J]. High Power Laser and Particle Beams, 2021, 33(6): 6-18. [23] Zheng Hanbo, Li Xufan, Feng Yongji, et al.Investigation on micro-mechanism of palm oil as natural ester insulating oil for overheating thermal fault analysis of transformers[J]. High Voltage, 2022, 7(4): 812-824. [24] Holroyd R A, Preses J M, Boettcher E H, et al.Photoconductivity induced by single-photon excitation of aromatic molecules in liquid hydrocarbons[J]. The Journal of Physical Chemistry, 1984, 88(4): 744-749. [25] 董明, 杨凯歌, 马馨逸, 等. 纳米改性变压器油中载流子输运特性分析[J]. 电工技术学报, 2020, 35(21): 4597-4608. Dong Ming, Yang Kaige, Ma Xinyi, et al.Analysis of charge-carrier transport characteristics of transformer oil-based nanofluids[J]. Transactions of China Electrotechnical Society, 2020, 35(21): 4597-4608. [26] Xue Qingjiang, Timoshkin I, Given M J, et al.Mobility of charge carriers in dielectric liquids[C]//2019 IEEE 20th International Conference on Dielectric Liquids (ICDL), Roma, Italy, 2019: 1-4. [27] Xue Qingjiang, Timoshkin I, Wilson M P, et al.Mobility of charge carriers in mineral oil and ester fluids[J]. High Voltage, 2021, 6(6): 1040-1050. [28] 王琪, 王萌, 王珏, 等. 纳秒脉冲下变压器油两相流注放电仿真研究[J]. 强激光与粒子束, 2020, 32(2): 63-67. Wang Qi, Wang Meng, Wang Jue, et al.Two-phase streamer characteristics in transformer oil under nanosecond impulses voltages[J]. High Power Laser and Particle Beams, 2020, 32(2): 63-67. [29] Liu Q, Wang Z D.Streamer characteristic and breakdown in synthetic and natural ester transformer liquids with pressboard interface under lightning impulse voltage[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2011, 18(6): 1908-1917. [30] Jadidian J, Zahn M, Lavesson N, et al.Effects of impulse voltage polarity, peak amplitude, and rise time on streamers initiated from a needle electrode in transformer oil[J]. IEEE Transactions on Plasma Science, 2012, 40(3): 909-918. [31] Duy C T, Lesaint O, Denat A, et al.Streamer propagation and breakdown in natural ester at high voltage[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2009, 16(6): 1582-1594. [32] 林翔. 植物绝缘油长油隙雷电冲击放电特性研究[D]. 重庆: 重庆大学, 2017.