非线性电导环氧树脂复合材料在±600 kV换流变压器套管中的应用仿真研究
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摘要
换流变压器套管是换流变压器的一个绝缘薄弱环节,尤其是套管中心导杆发热使芯子产生的径向温度差,会造成电场畸变,在运行过程中易引发绝缘故障。为此,以±600 kV超高压换流变压器套管为对象,研究了不同工况下套管的径向电场分布,并尝试应用非线性电导环氧树脂绝缘来抑制套管的径向电场畸变。研究结果表明:随着套管负载的增加,径向温差使法兰处套管芯子的电场分布发生畸变,法兰附近的畸变场强满载时高达12k V/mm;同时,套管芯子在导杆附近场强的下降使端部SF6气体承受的电气强度增加了近3倍,极易造成气体放电。在替换为非线性电导环氧树脂绝缘后,法兰处的套管芯子电场畸变得到了极大的改善,同时也有效缓解了套管端部SF6气体和变压器油的绝缘负担。虽然非线性套管在运行中环氧芯子损耗增加,但是与导杆的焦耳发热相比,该损耗可以忽略。仿真结果证明了应用非线性电导环氧树脂绝缘抑制套管芯子电场畸变从而降低故障概率的可行性。
Converter transformer bushing is an insulation weak link of the converter transformer, especially, the radial temperature difference generated by the core of the bushing will cause the electric field to be distorted, which is prone to insulation fault during operation. Consequently, we studied the radial electric field distribution of a ±600 kV ultra-high voltage converter transformer bushing under different working conditions, and applied a nonlinear electric conductivity epoxy resin insulation to suppress the radial electric field distortion of the bushing. The research results show that the electric field distribution of the bushing core at the flange is distorted by radial temperature differences with the increasing of the bushing load, and the distortion field strength near the flange is as high as 12 kV/mm under full load. At the same time, the decrease in field strength of the casing core near the guide rod increases the electrical strength of the end SF6 gas by nearly three times, which is highly likely to cause gas discharge. After replacement of non-linear conductive epoxy resin insulation, the electric field distortion of the bushing core at the flange is greatly improved, and the insulation load of SF6 gas and transformer oil at the end of the bushing is also effectively alleviated. The epoxy core loss in non-linear bushing increases during its operation; however, compared with the current heating in the conductor, the loss increase can be ignored. The simulation results prove the feasibility of using nonlinear conductance epoxy resin insulation to suppress the electric field distortion of bushing core and reduce the probability of failure.
Converter transformer bushing is an insulation weak link of the converter transformer, especially, the radial temperature difference generated by the core of the bushing will cause the electric field to be distorted, which is prone to insulation fault during operation. Consequently, we studied the radial electric field distribution of a ±600 kV ultra-high voltage converter transformer bushing under different working conditions, and applied a nonlinear electric conductivity epoxy resin insulation to suppress the radial electric field distortion of the bushing. The research results show that the electric field distribution of the bushing core at the flange is distorted by radial temperature differences with the increasing of the bushing load, and the distortion field strength near the flange is as high as 12 kV/mm under full load. At the same time, the decrease in field strength of the casing core near the guide rod increases the electrical strength of the end SF6 gas by nearly three times, which is highly likely to cause gas discharge. After replacement of non-linear conductive epoxy resin insulation, the electric field distortion of the bushing core at the flange is greatly improved, and the insulation load of SF6 gas and transformer oil at the end of the bushing is also effectively alleviated. The epoxy core loss in non-linear bushing increases during its operation; however, compared with the current heating in the conductor, the loss increase can be ignored. The simulation results prove the feasibility of using nonlinear conductance epoxy resin insulation to suppress the electric field distortion of bushing core and reduce the probability of failure.
引文
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[15]ZHOU H Y,MA G M,LI C R,et al.Impact of temperature on surface charges accumulation on insulators in SF6-filled DC-GIL[J].IEEETransactions on Dielectrics and Electrical Insulation,2017,24(1):601-610.
[16]王飞风,张沛红,高铭泽.纳米碳化硅/硅橡胶复合物非线性电导特性研究[J].物理学报,2014,63(21):356-363.WANG Feifeng,ZHANG Peihong,GAO Mingze.Research on the non-linear conductivity characteristics of nano-SiC/silicone rubber composites[J].Acta Physica Sinica,2014,63(21):356-363.
[2]杜伯学,李忠磊,杨卓然,等.高压直流交联聚乙烯电缆应用与研究进展[J].高电压技术,2017,43(2):344-354.DU Boxue,LI Zhonglei,YANG Zhuoran,et al.Application and research progress of HVDC XLPE cables[J].High Voltage Engineering,2017,43(2):344-354.
[3]杜伯学,侯兆豪,徐航,等.高压直流电缆绝缘用聚丙烯及其纳米复合材料的研究进展[J].高电压技术,2017,43(9):2769-2780.DU Boxue,HOU Zhaohao,XU Hang,et al.Research achievements in polypropylene and polypropylene/inorganic nanocomposites for HVDC cable Insulation[J].High Voltage Engineering,2017,43(9):2679-2780.
[4]刘刚,李琳,赵小军,等.油-纸绝缘结构非线性交直流复合电场计算的定点频域有限元法[J].中国电机工程学报,2012,32(1):154-161.LIU Gang,LI Lin,ZHAO Xiaojun,et al.Analysis of nonlinear electric field of oil-paper insulation under AC-DC hybrid voltage by fixed point method combined with FEM in frequency domain[J].Proceedings of the CSEE,2012,32(1):154-161.
[5]张施令,彭宗仁,刘鹏,等.电热耦合模型应用于干式油气套管径向温度分布计算及其试验研究[J].电网技术,2012,36(12):289-296.ZHANG Shiling,PENG Zongren,LIU Peng,et al.Experimental study on electro-thermal coupling model applied in computation of radial temperature distribution of RIP oil-gas bushing condenser[J].Power System Technology,2012,36(12):289-296.
[6]吴云飞,黄友生.换流变压器阀侧套管局部温度过高的故障分析[J].变压器,2007,44(8):36-38.WU Yunfei,HUANG Yousheng.Analysis of partial over temperature fault of valve bushing in converter transformer[J].Transformer,2007,44(8):36-38.
[7]JYOTHI N S,RAMU T S,MANDLIK M.Temperature distribution in resin impregnated paper insulation for transformer bushings[J].IEEETransactions on Dielectrics and Electrical Insulation,2010,17(3):931-938.
[8]LIAO C,RUAN J,LIU C,et al.3-D coupled electromagnetic-fluidthermal analysis of oil-immersed triangular wound core transformer[J].IEEE Transactions on Magnetics,2014,50(11):1-4.
[9]王青于,杨熙,彭宗仁,等.应用三维电磁-热-流耦合场分析法计算换流变压器干式套管的温度场分布[J].中国电机工程学报,2016,36(22):6269-6275.WANG Qingyu,YANG Xi,PENG Zongren,et al.3D coupled electromagnetic-thermal-fluid method for computation of temperature field of converter transformer RIP bushings[J].Proceedings of the CSEE,2016,36(22):6269-6275.
[10]张施令,彭宗仁,刘鹏,等.电热耦合模型应用于高压干式直流套管径向温度和电场分布计算[J].中国电机工程学报,2013,36(22):191-200.ZHANG Shiling,PENG Zongren,LIU Peng,et al.Electro-thermal coupling model for computation of radial temperature and electric field of resin impregnated paper high voltage direct current bushing[J].Proceedings of the CSEE,2013,36(22):191-200.
[11]刘晨阳,郑晓泉,别成亮.掺杂ZnO/环氧树脂基体的制备及其非线性电导改性研究[J].电工技术学报,2016,31(12):24-30.LIU Chenyang,ZHENG Xiaoquan,BIE Chengliang.Research of preparation and nonlinear conductivity modification of doped ZnO/epoxide resin material[J].Transactions of China Electrotechnical Society,2016,31(12):24-30.
[12]郭文敏,韩宝忠,李忠华.聚乙烯/碳化硅复合材料的非线性电导特性的研究[J].功能材料,2010,41(3):436-438.GUO Wenmin,HAN Baozhong,LI Zhonghua.Study on non-linear conductivity characteristic of polyethylene/carborundum composites[J].Journal of Functional Materials,2010,41(3):436-438.
[13]DU B X,YANG Z R,LI Z L,et al.Surface charge behavior of silicone rubber/SiC composites with field-dependent conductivity[J].IEEETransactions on Dielectrics and Electrical Insulation,2017,24(3):1340-1348.
[14]胡军,赵孝磊,杨霄,等.非线性电导材料应力锥改善电缆终端电场强度分布[J].高电压技术,2017,43(2):398-404.HU Jun,ZHAO Xiaolei,YANG Xiao,et al.Improving the electric field strength distribution of cable terminals by stress cone of nonlinear conductivity material[J].High Voltage Engineering,2017,43(2):398-404.
[15]ZHOU H Y,MA G M,LI C R,et al.Impact of temperature on surface charges accumulation on insulators in SF6-filled DC-GIL[J].IEEETransactions on Dielectrics and Electrical Insulation,2017,24(1):601-610.
[16]王飞风,张沛红,高铭泽.纳米碳化硅/硅橡胶复合物非线性电导特性研究[J].物理学报,2014,63(21):356-363.WANG Feifeng,ZHANG Peihong,GAO Mingze.Research on the non-linear conductivity characteristics of nano-SiC/silicone rubber composites[J].Acta Physica Sinica,2014,63(21):356-363.