采用瞬态上流元法的油纸绝缘瞬态电场研究
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摘要
作为换流变压器的主要绝缘材料,油纸复合材料的绝缘特性受内部空间电荷的影响.在极性反转电压下,介质内部积聚电荷产生附加场强,可能使局部电场明显增强,从而更易引起绝缘击穿.基于瞬态上流有限元数值方法,引入界面势垒模型,计算极性反转条件下单层油浸纸、油浸纸-油双层绝缘结构内部空间电荷的运动特性以及瞬态电场随时间的变化规律,并与试验得到的规律进行对比验证.仿真结果表明:在直流电压下,介质内部积聚的电荷无法快速消散,将对反转瞬间的电场产生叠加作用,引起电极附近场强最大程度畸变.双层介质的界面阻碍效应产生的界面积聚电荷,导致在极性反转瞬间油中电场瞬时增大.研究结果可为换流变压器油纸绝缘特性和击穿场强研究提供参考.
The insulation property of oil-paper composite material, as main insulation material of converter transformer, is influenced by internal space charges. Under polarity reversal voltage, the accumulative charges inside the insulation will produce additional field strength and significantly enhance the local electric field, which tends to cause insulation breakdown. The interfacial barrier model was adopted based on the transient upstream finite element method(TUFEM), and the charge motion characteristics and transient electric field under polarity reversal in singlelayer oil-impregnated paper and two layers of oil-impregnated paper and oil were calculated. The simulation results were compared with the experiment results to verify applicability of the numerical method. Results showed that internal accumulative charges formed under direct current voltage were unable to dissipate quickly, which had a superposition effect on electric field at the instant of polarity reversal, causing the maximal electric field distortion near the electrodes. The accumulative charges at the interface due to interfacial blocking effect will lead to sudden increase in electric field of oil. The conclusion can provide reference for the study of oil-paper insulation characteristic and breakdown strength.
The insulation property of oil-paper composite material, as main insulation material of converter transformer, is influenced by internal space charges. Under polarity reversal voltage, the accumulative charges inside the insulation will produce additional field strength and significantly enhance the local electric field, which tends to cause insulation breakdown. The interfacial barrier model was adopted based on the transient upstream finite element method(TUFEM), and the charge motion characteristics and transient electric field under polarity reversal in singlelayer oil-impregnated paper and two layers of oil-impregnated paper and oil were calculated. The simulation results were compared with the experiment results to verify applicability of the numerical method. Results showed that internal accumulative charges formed under direct current voltage were unable to dissipate quickly, which had a superposition effect on electric field at the instant of polarity reversal, causing the maximal electric field distortion near the electrodes. The accumulative charges at the interface due to interfacial blocking effect will lead to sudden increase in electric field of oil. The conclusion can provide reference for the study of oil-paper insulation characteristic and breakdown strength.
引文
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[2]廖瑞金,李伟,杨丽君.变压器油纸绝缘介质在直流电场中的空间电荷输运特性[J].高电压技术,2011,37(5):1057-1065.LIAO Rui-jin,LI Wei,YANG Li-jun.Space charge transport properties of oil-paper insulation materials under DC field used in transformer[J].High Voltage Engineering,2011,37(5):1057-1065.
[3]吕晓德,陈世坤,方志强,等.换流变压器端部极性反转电场的数值算法及其绝缘设计[J].西安交通大学学报,1997,31(11):8-12.LV Xiao-de,CHEN Shi-kun,FANG Zhi-qiang,et al.Numerical computation of polarity reversal electric field in the converter transformer ending and its insulation design[J].Journal of Xi'an Jiaotong University,1997,31(11):8-12.
[4]WEN K,ZHOU Y,FU J,et al.A calculation method and some features of transient field under polarity reversal voltage in HVDC insulation[J].IEEETransactions on Power Delivery,1993,8(1):223-230.
[5]李琳,纪锋,刘刚.油纸绝缘结构瞬态电场计算的状态空间有限元法[J].中国电机工程学报,2010,30(36):111-116.LI Lin,JI Feng,LIU Gang.A state space finite element method for calculation of transient electrical field in oil-paper insulation construction[J].Proceedings of the CSEE,2010,30(36):111-116.
[6]李琳,纪锋,李文平,等.换流变压器极性反转试验的数值模拟[J].中国电机工程学报,2011,31(18):107-112.LI Lin,JI Feng,LI Wen-ping,et al.Numerical simulation of converter transformer's polarity reversal test[J].Proceedings of the CSEE,2011,31(18):107-112.
[7]HUANG B,HAO M,HAO J,et al.Space charge characteristics in oil and oil-impregnated pressboard and electric field distortion after polarity reversal[J].IEEE Transactions on Dielectrics and Electrical Insulation,2016,23(2):881-891.
[8]HUANG M,ZHOU Y,CHEN W.Influence of voltage reversal on space charge behavior in oilpaper insulation[J].IEEE Transactions on Dielectrics and Electrical Insulation,2014,21(1):331-339.
[9]ALISON J M,HILL R M.A model for bipolar charge transport,trapping and recombination in degassed crosslinked polyethene[J].Journal of Physics D:Applied Physics,1994,27(6):1291-1299.
[10]TAKUMA T,IKEDA T,KAWAMOTO T.Calculation of ion flow fields of HVDC transmission lines by the finite element method[J].IEEETransactions on Power Apparatus and Systems,1981,PAS-100(12):4802-4810.
[11]连启祥,杜志叶,杨知非,等.油-纸绝缘结构合成电场数值模拟方法研究[J].电工技术学报,2017,32(20):53-61.LIAN Qi-xiang,DU Zhi-ye,YANG Zhi-fei,et al.Numerical simulation of electric field considering space charge in oil-paper insulation[J].Transaction of China Electrotechnical Society,2017,32(20):53-61.
[12]ROY S L,SEGUR P,TEYSSEDRE G,et al.Description of bipolar charge transport in polyethylene using a fluid model with a constant mobility:model prediction[J].Journal of Physics D:Applied Physics,2004,37(2):298-305.
[13]陈季丹,刘子玉.电介质物理学[M].北京:机械工业出版社,1982:66-68.
[14]唐超.油纸绝缘介质的直流空间电荷特性研究[D].重庆:重庆大学,2010:5-8.TANG Chao.The study on DC space charge characteristics of oil-paper insulating medium under DC[D].Chongqing:Chongqing University,2010:5-8.
[15]BELGAROUI E,BOUKHRIS I,KALLEL A,et al.Anew numerical model applied to bipolar charge transport,trapping and recombination under low and high DC voltages[J].Journal of Physics D:Applied Physics,2007,40(21):6760-6767.
[16]冯晗.高压直流输电线路离子流场计算及其工程应用[D].北京:华北电力大学,2006.FENG Han.Calculation of the ionized field under high voltage direct current transmission lines and engineering application[D].Beijing:North China Electric Power University,2006.
[17]陈曦,王霞,吴锴,等.极性反转时间对聚乙烯中空间电荷及瞬态电场的影响[J].西安交通大学学报,2010,44(10):105-10.CHEN Xi,WANG Xia,WU Kai,et al.Effect of voltage reverse time on space charge and transient field in polyethylene[J].Journal of Xi'an Jiaotong University,2010,44(10):105-10.
[18]ROY S L,SEGUR P,TEYSSEDRE G,et al.Description of charge transport in polyethylene using a fluid model with a constant mobility:fitting model and experiments[J].Journal of Physics D:Applied Physics,2006,39(7):1427-1436.
[19]周远翔,黄猛,陈维江,等.直流电场下油纸绝缘介质界面处的空间电荷特性[J].高电压技术,2011,37(10):2417-2423.ZHOU Yuan-xiang,HUNAG Meng,CHEN Weijiang,et al.Space charge characteristics of the interface in oil-paper insulation under DCvoltage[J].High Voltage Engineering,2011,37(10):2417-2423.
[20]朱庆东,吴锴,朱文兵,等.温度梯度下油纸绝缘空间电荷特性的数值仿真[J].高电压技术,2016,42(3):923-930.ZHU Qing-dong,WU Kai,ZHU Wen-bing,et al.Numerical simulation of space charge property in oil-paper insulation under temperature gradient[J].High Voltage Engineering,2016,42(3):923-930.
[21]WU K,ZHU Q,WANG H,et al.Space charge behavior in the sample with two layers of oilimmersed-paper and oil[J].IEEE Transactions on Dielectrics and Electrical Insulation,2014,21(4):1857-1865.
[22]周远翔,黄猛,陈维江,等.直流电压下多层油纸绝缘介质的界面空间电荷特性[J].高电压技术,2013,39(6):1304-1311.ZHOU Yuan-xiang,HUANG Meng,CHEN Weijiang,et al.Interface space charge characteristics in multi-layer oil-paper insulation under DCvoltage[J].High Voltage Engineering,2013,39(6):1304-1311.