交联聚乙烯中丛状电树枝的生长机制
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摘要
为了研究交联聚乙烯(cross-linked polyethylene,XLPE)中丛状电树枝的生长机理,采用XLPE薄片试样进行电树枝老化实验,通过实时显微观测系统完整记录了在工频高压下电树枝从引发到击穿的全过程,利用扫描电镜观察丛状电树枝的微观结构,并对电树枝通道进行能谱分析。通过构建丛状电树枝不同阶段的有限元电场仿真模型,进一步分析丛状电树枝生长特性与微观结构的关系。研究表明:电树枝引发初期,气体的迅速膨胀促使非导电型电树枝沿无定形区快速生长;碳颗粒周围产生的局部放电和电-机械应力导致电树枝进一步分叉和生长,碳颗粒的不断聚集使非导电型电树枝逐渐转化为导电型电树枝;丛状电树枝团端部场强相对较小以及电树枝内部局部放电减少,是丛状电树枝滞长的主要原因;电树枝团端部由于电-机械应力作用可能形成新的微孔或裂纹,易形成新的电树枝,最终导致绝缘击穿。
To study the mechanism of brush-type electrical tree growing in cross-linked polyethylene(XLPE), the electrical tree aging experiments in XLPE slice samples were made. Under power frequency and high voltage, the whole process of electrical tree aging from initiation to breakdown was recorded by the real-time microscopic observation system. The microstructure of electrical tree was observed by scanning electron microscope and the energy spectrum of the electrical tree channel was analyzed. The relationship between electrical tree growing characteristics and microstructure was analyzed based on the finite element simulation models of electrical tree at different stages of electrical tree aging. The results show that the rapid expansion of gas in the early stage of electrical tree initiation leads to the rapid growing of non-conducting electrical trees along amorphous regions. Due to strong electrical-mechanical stress and partial discharges around carbon particles, electrical trees are growing and bifurcating ceaselessly. In addition, with the continuous accumulation of carbon particles, non-conductive electrical trees are gradually transformed into conductive electrical trees. The lesser electric field strength at the end of electrical tree group and the decrease of partial discharges in the electrical tree channels lead to the stagnation of electrical trees. However, with the passage of time, some new micro cracks can be formed due to the accumulation of fatigue by electrical-mechanical stress. New electrical trees begin to grow and the insulation was broken eventually.
To study the mechanism of brush-type electrical tree growing in cross-linked polyethylene(XLPE), the electrical tree aging experiments in XLPE slice samples were made. Under power frequency and high voltage, the whole process of electrical tree aging from initiation to breakdown was recorded by the real-time microscopic observation system. The microstructure of electrical tree was observed by scanning electron microscope and the energy spectrum of the electrical tree channel was analyzed. The relationship between electrical tree growing characteristics and microstructure was analyzed based on the finite element simulation models of electrical tree at different stages of electrical tree aging. The results show that the rapid expansion of gas in the early stage of electrical tree initiation leads to the rapid growing of non-conducting electrical trees along amorphous regions. Due to strong electrical-mechanical stress and partial discharges around carbon particles, electrical trees are growing and bifurcating ceaselessly. In addition, with the continuous accumulation of carbon particles, non-conductive electrical trees are gradually transformed into conductive electrical trees. The lesser electric field strength at the end of electrical tree group and the decrease of partial discharges in the electrical tree channels lead to the stagnation of electrical trees. However, with the passage of time, some new micro cracks can be formed due to the accumulation of fatigue by electrical-mechanical stress. New electrical trees begin to grow and the insulation was broken eventually.
引文
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[7]Sarathi R,Raju P G.Study of electrical treeing phenomena in XLPE cable samples using acoustic techniques[J].Electric Power Systems Research,2005,73(2):159-168.
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[9]Fothergill J C.Filamentary electromechanical breakdown[J].IEEE Transactions on Electrical Insulation,1991,26(6):1124-1129.
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[12]Fabian J H,Hartmann S,Hamidi A.Analysis of insulation failure modes in high power IGBT modules[C]//Conference Record of the 2005 IEEE Industry Applications Conference Fortieth IAS Annual Meeting.Hong Kong,China:Institute of Electrical and Electronics Engineers,2005:799-805.
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[15]尹毅,肖登明,屠德民.空间电荷在评估绝缘聚合物电老化程度中的应用研究[J].中国电机工程学报,2002,22(1):43-48.Yin Yi,Xiao Dengming,Tu Demin.An application of space charge in valuing the electric ageing degree of insulating polymer[J].Proceedings of the CSEE,2002,22(1):43-48(in Chinese).
[16]郑晓泉,Chen G,Davies A E.交联聚乙烯中的滞长型丛林状电树枝特性研究[J].绝缘材料,2003,36(3):25-27.Zheng Xiaoquan,Chen G,Davies A E.Study on the characteristics of electrical tree with bush structure and growing very slowly in low frequency[J].Insulating Materials,2003,36(3):25-27(in Chinese).
[17]周远翔,聂琼,邢晓亮,等.频率对高密度聚乙烯电树老化特性的影响[J].高电压技术,2008,34(2):220-224.Zhou Yuanxiang,Nie Qiong,Xing Xiaoliang,et al.Effect of frequency on electrical treeing characteristics of high-density polyethylene[J].High Voltage Engineering,2008,34(2):220-224(in Chinese).
[18]陈向荣,徐阳,刘英,等.交联聚乙烯电缆绝缘材料中电树枝的导电特性研究[J].物理学报,2012,61(8):087701.Chen Xiangrong,Xu Yang,Liu Ying,et al.Study on conducting characteristics of electrical trees in cross-linked polyethylene cable insulation[J].Acta Physica Sinica,2012,61(8):087701(in Chinese).
[19]Zhou Kai,Huang Ming,Tao Wenbiao,et al.A possible water tree initiation mechanism for service-aged XLPE cables:Conversion of electrical tree to water tree[J].IEEE Transactions on Dielectrics and Electrical Insulation,2016,23(3):1854-1861.
[20]Wang Zuoqian,Marcolongo P,Lemberg J A,et al.Mechanical fatigue as a mechanism of water tree propagation in TR-XLPE[J].IEEE Transactions on Dielectrics and Electrical Insulation,2012,19(1):12537154.
[21]欧阳本红,刘松华,邓显波,等.高压XLPE电缆绝缘厚度优化设计[J].高电压技术,2016,42(8):2388-2393.Ouyang Benhong,Liu Songhua,Deng Xianbo,et al.Optimization design for insulation thickness of high-voltage XLPE cable[J].High Voltage Engineering,2016,42(8):2388-2393(in Chinese).
[22]Densley J,Kalicki T,Nodolny Z,et al.Characteristics of PD pulses in electrical trees and interfaces in extruded cables[J].IEEE Transactions on Dielectrics and Electrical Insulation,2001,8(1):48-57.
[2]李春阳,韩宝忠,张城城,等.电压稳定剂提高PE/XLPE绝缘耐电性能研究综述[J].中国电机工程学报,2017,37(16):4850-4864.Li Chunyang,Han Baozhong,Zhang Chengcheng,et al.Review of voltage stabilizer improving the electrical strength of PE/XLPE[J].Proceedings of the CSEE,2017,37(16):4850-4864(in Chinese).
[3]周利军,仇祺沛,成睿,等.不同温度下局部气压对XLPE电缆电树枝生长及局放特性的影响[J].中国电机工程学报,2016,36(18):5094-5102.Zhou Lijun,Qiu Qipei,Cheng Rui,et al.Influence of partial air pressure on propagation and partial discharge characteristics of electrical trees in XLPE cable under different temperatures[J].Proceedings of the CSEE,2016,36(18):5094-5102(in Chinese).
[4]周利军,成睿,江俊飞,等.局部气压对交联聚乙烯电缆电树枝生长特性的影响[J].高电压技术,2015,41(8):2650-2656.Zhou Lijun,Cheng Rui,Jiang Junfei,et al.Influence of partial air pressure on the growth characteristics of electrical tree in XLPE cable[J].High Voltage Engineering,2015,41(8):2650-2656(in Chinese).
[5]陶文彪,周凯,赵威,等.有机硅注入技术延长运行电缆使用寿命的研究[J].中国电机工程学报,2012,32(s1):76-80.Tao Wenbiao,Zhou Kai,Zhao Wei,et al.Study of siloxane injection technology for extending the lifetime of the operating cable[J].Proceedings of the CSEE,2012,32(s1):76-80(in Chinese).
[6]Dissado L A.Understanding electrical trees in solids:from experiment to theory[J].IEEE Transactions on Dielectrics and Electrical Insulation,2002,9(4):483-497.
[7]Sarathi R,Raju P G.Study of electrical treeing phenomena in XLPE cable samples using acoustic techniques[J].Electric Power Systems Research,2005,73(2):159-168.
[8]Chen Xiangrong,Xu Yang,Cao Xiaolong,et al.On the conducting and non-conducting electrical trees in XLPE cable insulation specimens[J].IEEE Transactions on Dielectrics and Electrical Insulation,2016,23(1):95-103.
[9]Fothergill J C.Filamentary electromechanical breakdown[J].IEEE Transactions on Electrical Insulation,1991,26(6):1124-1129.
[10]Zeller H R,Schneider W R.Electrofracture mechanics of dielectric aging[J].Journal of Applied Physics,1984,56(2):455-459.
[11]郑晓泉,Chen G,Davies A E.交联聚乙烯电缆绝缘中的导电和非导电型电树枝[J].中国电机工程学报,2004,24(3):140-144.Zheng Xiaoquan,Chen G,Davies A E.Conducting and non-conducting electrical trees in XLPE[J].Proceedings of the CSEE,2004,24(3):140-144(in Chinese).
[12]Fabian J H,Hartmann S,Hamidi A.Analysis of insulation failure modes in high power IGBT modules[C]//Conference Record of the 2005 IEEE Industry Applications Conference Fortieth IAS Annual Meeting.Hong Kong,China:Institute of Electrical and Electronics Engineers,2005:799-805.
[13]Shimizu N,Tanaka T.Effect of liquid impregnation on electrical tree initiation in XLPE[J].IEEE Transactions on Dielectrics and Electrical Insulation,2001,8(2):239-243.
[14]党智敏,亢婕,屠德民.EAA改性XLPE中空间电荷和电树、水树的关系[J].中国电机工程学报,2001,21(7):5-8.Dang Zhimin,Kang Jie,Tu Demin.Relationships of space charge accumulation with electrical and water treeing in XLPE modified by EAA[J].Proceedings of the CSEE,2001,21(7):5-8(in Chinese).
[15]尹毅,肖登明,屠德民.空间电荷在评估绝缘聚合物电老化程度中的应用研究[J].中国电机工程学报,2002,22(1):43-48.Yin Yi,Xiao Dengming,Tu Demin.An application of space charge in valuing the electric ageing degree of insulating polymer[J].Proceedings of the CSEE,2002,22(1):43-48(in Chinese).
[16]郑晓泉,Chen G,Davies A E.交联聚乙烯中的滞长型丛林状电树枝特性研究[J].绝缘材料,2003,36(3):25-27.Zheng Xiaoquan,Chen G,Davies A E.Study on the characteristics of electrical tree with bush structure and growing very slowly in low frequency[J].Insulating Materials,2003,36(3):25-27(in Chinese).
[17]周远翔,聂琼,邢晓亮,等.频率对高密度聚乙烯电树老化特性的影响[J].高电压技术,2008,34(2):220-224.Zhou Yuanxiang,Nie Qiong,Xing Xiaoliang,et al.Effect of frequency on electrical treeing characteristics of high-density polyethylene[J].High Voltage Engineering,2008,34(2):220-224(in Chinese).
[18]陈向荣,徐阳,刘英,等.交联聚乙烯电缆绝缘材料中电树枝的导电特性研究[J].物理学报,2012,61(8):087701.Chen Xiangrong,Xu Yang,Liu Ying,et al.Study on conducting characteristics of electrical trees in cross-linked polyethylene cable insulation[J].Acta Physica Sinica,2012,61(8):087701(in Chinese).
[19]Zhou Kai,Huang Ming,Tao Wenbiao,et al.A possible water tree initiation mechanism for service-aged XLPE cables:Conversion of electrical tree to water tree[J].IEEE Transactions on Dielectrics and Electrical Insulation,2016,23(3):1854-1861.
[20]Wang Zuoqian,Marcolongo P,Lemberg J A,et al.Mechanical fatigue as a mechanism of water tree propagation in TR-XLPE[J].IEEE Transactions on Dielectrics and Electrical Insulation,2012,19(1):12537154.
[21]欧阳本红,刘松华,邓显波,等.高压XLPE电缆绝缘厚度优化设计[J].高电压技术,2016,42(8):2388-2393.Ouyang Benhong,Liu Songhua,Deng Xianbo,et al.Optimization design for insulation thickness of high-voltage XLPE cable[J].High Voltage Engineering,2016,42(8):2388-2393(in Chinese).
[22]Densley J,Kalicki T,Nodolny Z,et al.Characteristics of PD pulses in electrical trees and interfaces in extruded cables[J].IEEE Transactions on Dielectrics and Electrical Insulation,2001,8(1):48-57.