纳米TiO_2对直流电缆用XLPE介电性能的影响
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摘要
为探索提升高压直流电缆用交联聚乙烯直流介电性能的方法,采用熔融共混法在直流电缆用交联聚乙烯基体中添加微量(质量分数0.1%、0.5%、1%)纳米TiO_2制备得到XLPE/TiO_2纳米复合介质,并通过纳米粒子表面偶联剂处理对比研究了表面改性对XLPE/TiO_2介电性能的影响。采用SEM观测纳米粒子的分散性,测试了XLPE和XLPE/TiO_2的结晶度、电导率温度特性、空间电荷注入特性和直流击穿场强。结果表明,采用偶联剂进行表面处理能够改善纳米粒子的分散性,在直流电缆用XLPE中直接添加微量纳米TiO_2能够增大结晶度、电导活化能和直流击穿场强,降低电导率,抑制正电荷的注入,而添加经过偶联剂处理的纳米TiO_2可使这些影响更加显著。分析认为,结晶度的增大是由于纳米粒子的成核作用,而偶联剂处理使得粒子与基体结合更加紧密从而进一步增大结晶度。电导特性和空间电荷特性的改善主要由于纳米TiO_2形成交互区以及聚集态结构改变对陷阱特性的影响,在较低场强下测试得到的电导活化能的增大即对应为复合介质的深陷阱能级的增加,因此电荷注入得到了明显的抑制。电荷陷阱的引入也使得电导率随粒子含量的增加而减小。直流击穿场强的提高则是由聚集态结构和陷阱特性两者共同作用导致的。因此,高压直流电缆用交联聚乙烯材料可以采用添加微量纳米TiO_2(0.5%)进一步改善直流介电性能,偶联剂处理过程则使得改善效果更加显著。
In order to explore the method of improving the DC dielectric properties of crosslinked polyethylene for HVDC cable, a small amount of nano-TiO_2(0.1%, 0.5%, 1%) were added into the crosslinked polyethylene matrix for DC cable using the melt blending method. The effect of surface modification on the dielectric properties of XLPE/TiO_2 was studied. Moreover, the dispersion of TiO_2 was observed by SEM, and the crystallinity, the conductivity at different temperatures, space charge injection characteristics and DC breakdown field strength of XLPE and XLPE/TiO_2 nanocomposites were tested. The results show that surface modification can improve the TiO_2 nanoparticle dispersion, the addition of nano-TiO_2 to XLPE for DC cable can increase the crystallinity, conductivity activation energy and DC breakdown field strength, reduce the conductivity and suppress the injection of positive charges, and surface modification using a coupling agent can make these effects more significant. It is suggested that the nanoparticles act as nucleating agents, leading to the increase of crystallinity, and the coupling agent modification made the particles and matrix more close to further increase the crystallinity. The improvement of conductivity and space charge characteristics is mainly due to the effect of interaction area formed by nano-TiO_2 and the morphology on the trap characteristics. The increase of conductivity activation energy measured at lower field strength corresponds to the increase of deep trap energy, so the charge injection is significantly inhibited. The introduction of charge traps also decreases the conductivity with the increase of particle content. The DC breakdown field strength can be increased by the morphology and the trap characteristics. Therefore, adding 0.5% nano-TiO_2 into crosslinked polyethylene material for HVDC cable can further improve the DC dielectric properties, and the coupling agent modification will make the improvement more significant.
In order to explore the method of improving the DC dielectric properties of crosslinked polyethylene for HVDC cable, a small amount of nano-TiO_2(0.1%, 0.5%, 1%) were added into the crosslinked polyethylene matrix for DC cable using the melt blending method. The effect of surface modification on the dielectric properties of XLPE/TiO_2 was studied. Moreover, the dispersion of TiO_2 was observed by SEM, and the crystallinity, the conductivity at different temperatures, space charge injection characteristics and DC breakdown field strength of XLPE and XLPE/TiO_2 nanocomposites were tested. The results show that surface modification can improve the TiO_2 nanoparticle dispersion, the addition of nano-TiO_2 to XLPE for DC cable can increase the crystallinity, conductivity activation energy and DC breakdown field strength, reduce the conductivity and suppress the injection of positive charges, and surface modification using a coupling agent can make these effects more significant. It is suggested that the nanoparticles act as nucleating agents, leading to the increase of crystallinity, and the coupling agent modification made the particles and matrix more close to further increase the crystallinity. The improvement of conductivity and space charge characteristics is mainly due to the effect of interaction area formed by nano-TiO_2 and the morphology on the trap characteristics. The increase of conductivity activation energy measured at lower field strength corresponds to the increase of deep trap energy, so the charge injection is significantly inhibited. The introduction of charge traps also decreases the conductivity with the increase of particle content. The DC breakdown field strength can be increased by the morphology and the trap characteristics. Therefore, adding 0.5% nano-TiO_2 into crosslinked polyethylene material for HVDC cable can further improve the DC dielectric properties, and the coupling agent modification will make the improvement more significant.
引文
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[19]詹威鹏,褚学来,申作家,等.加速热氧老化中交联聚乙烯电缆绝缘聚集态结构与介电强度关联性研究[J].中国电机工程学报,2016,36(17):4770-4777.ZHAN Weipeng,CHU Xuelai,SHEN Zuojia,et al.Study on aggregation structure and dielectric strength of XLPE cable insulation in accelerated thermal-oxidative aging[J].Proceedings of the CSEE,2016,36(17):4770-4777.
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[21]王霞,王陈诚,朱有玉,等.高压直流塑料电缆绝缘用纳米改性交联聚乙烯中的空间电荷特性[J].高电压技术,2015,41(4):1096-1103.WANG Xia,WANG Chencheng,ZHU Youyu,et al.Space charge profiles in XLPE nano dielectrics used for HVDC plastic cable insulation[J].High Voltage Engineering,2015,41(4):1096-1103.
[22]KOLESOV S N.The Influence of morphology on the electric strength of polymer insulation[J].IEEE Transactions on Electrical Insulation,1980,EI-15(5):382-388.
[23]王威望.LDPE/Al2O3纳米复合电介质界面区特性与击穿关联的研究[D].陕西:西安交通大学,2015:10-12.WANG Weiwang.Investigation on correlation between interface characteristics and breakdown in LDPE/Al2O3 nanodielectrics[D].Shaanxi,China:Xi’an Jiaotong University,2015:10-12.
[24]DONGLING M,TREESE A H,RICHARD W S,et al.Influence of nanoparticle surface modification on the electrical behaviour of polyethylene nanocomposites[J].Nanotechnology,2005,16(6):724-731.
[2]马为民,樊纪超.特高压直流输电系统规划设计[J].高电压技术,2015,41(8):2545-2549.MA Weimin,FAN Jichao.Planning and design of UHVDC transmission system[J].High Voltage Engineering,2015,41(8):2545-2549.
[3]饶宏,张东辉,赵晓斌,等.特高压直流输电的实践和分析[J].高电压技术,2015,41(8):2481-2488.RAO Hong,ZHANG Donghui,ZHAO Xiaobin,et al.Practice and analyses of UHVDC power transmission[J].High Voltage Engineering,2015,41(8):2481-2488.
[4]周远翔,刘睿,张云霄,等.高压/超高压电力电缆关键技术分析及展望[J].高电压技术,2014,40(9):2593-2612.ZHOU Yuanxiang,LIU Rui,ZHANG Yunxiao,et al.Key technical analysis and prospect of high voltage and extra-high voltage power cable[J].High Voltage Engineering,2014,40(9):2593-2612.
[5]何金良,彭琳,周垚.环保型高压直流电缆绝缘材料研究进展[J].高电压技术,2017,43(2):337-343.HE Jinliang,PENG Lin,ZHOU Yao.Research progress of environment-friendly HVDC power cable insulation materials[J].High Voltage Engineering,2017,43(2):337-343.
[6]MA D,HUGENER T A,SIEGEL R W,et al.Influence of nanoparticle surface modification on the electrical behaviour of polyethylene nanocomposites[J].Nanotechnology,2005,16(6):724-731.
[7]ZAZOUM B,FRECHETTE M,DAVID E.LDPE/TiO2 nanocomposites:effect of POSS on structure and dielectric properties[J].IEEETransactions on Dielectrics and Electrical Insulation,2016,23(5):2505-2507.
[8]KHALIL M S,ZAKY A A,HANSEN B S.The influence of TiO2 and Ba TiO3 additives on the space charge distribution in LDPE[C]∥1985Annual Report Conference on Electrical Insulation and Dielectric Phenomena.[S.l.]:[s.n.],1985:143-148.
[9]JOSE J P,MHETAR V,CULLIGAN S,et al.Cross linked polyethylene/TiO2 nanocomposites:morphology,polymer/filler interaction,mechanics and thermal properties[J].Science of Advanced Materials,2013,5(4):385-397.
[10]ANDERSEN A,DENNISON J.Mixed Weibull distribution model of DC dielectric breakdowns with dual defect modes[C]∥2015 Annual Report Conference on Electrical Insulation and Dielectric Phenomena.Ann Arbor,MI,USA:IEEE,2015:570-573.
[11]陈铮铮,赵健康,欧阳本红,等.直流电缆料工作温度和击穿特性的纳米改性研究[J].高电压技术,2015,41(4):1214-1227.CHEN Zhengzheng,ZHAO Jiankang,OUYANG Benhong,et al.Study on the nanoparticle-modification of working temperature and breakdown characteristics for insulating materials in DC cables[J].High Voltage Engineering,2015,41(4):1214-1227.
[12]WANG S,CHEN P,LI J,et al.The improved DC performance of crosslinked polyethylene insulation depending on a higher purity[J].IEEE Transactions on Dielectrics and Electrical Insulation,2017,24(3):1809-1817.
[13]LEWIS T J.Interfaces are the dominant feature of dielectrics at the nanometric level[J].IEEE Transactions on Dielectrics and Electrical Insulation,2004,11(5):739-753.
[14]何金良,彭思敏,周垚,等.聚合物纳米复合材料的界面特性[J].中国电机工程学报,2016,36(24):6596-6605.HE Jinliang,PENG Simin,ZHOU Yao,et al.Interface properties of polymer nanocomposites[J].Proceedings of the CSEE,2016,36(24):6596-6605.
[15]张心亚,沈慧芳,黄洪,等.纳米粒子材料的表面改性及其应用研究进展[J].材料工程,2005(10):58-63.ZHANG Xinya,SHEN Huifang,HUANG Hong,et al.Novel progress of application and surface-modification technique for nano-particles materials[J].Journal of Materials Engineering,2005(10):58-63.
[16]HUZAYYIN A,BOGGS S,RAMPRASAD R.Density functional analysis of chemical impurities in dielectric polyethylene[J].IEEETransactions on Dielectrics and Electrical Insulation,2010,17(3):926-930.
[17]WANG W,MIN D,LI S.Understanding the conduction and breakdown properties of polyethylene nanodielectrics:effect of deep traps[J].IEEE Transactions on Dielectrics and Electrical Insulation,2016,23(1):564-572.
[18]田付强,杨春,何丽娟,等.聚合物/无机纳米复合电介质介电性能及其机理最新研究进展[J].电工技术学报,2011,26(3):1-12.TIAN Fuqiang,YANG Chun,HE Lijuan,et al.Recent research advancement in dielectric properties and the corresponding mechanism of polymer/inorganic nanocomposite[J].Transactions of China Electrotechnical Society,2011,26(3):1-12.
[19]詹威鹏,褚学来,申作家,等.加速热氧老化中交联聚乙烯电缆绝缘聚集态结构与介电强度关联性研究[J].中国电机工程学报,2016,36(17):4770-4777.ZHAN Weipeng,CHU Xuelai,SHEN Zuojia,et al.Study on aggregation structure and dielectric strength of XLPE cable insulation in accelerated thermal-oxidative aging[J].Proceedings of the CSEE,2016,36(17):4770-4777.
[20]吴振升,叶青,周远翔,等.表面修饰纳米SiO2/XLPE的电导电流和空间电荷特性[J].高电压技术,2014,40(10):3268-3275.WU Zhensheng,YE Qing,ZHOU Yuanxiang,et al.Conduction current and space charge characteristics of SiO2/XLPE nanocomposites with nanocomposite surface modification[J].High Voltage Engineering,2014,40(10):3268-3275.
[21]王霞,王陈诚,朱有玉,等.高压直流塑料电缆绝缘用纳米改性交联聚乙烯中的空间电荷特性[J].高电压技术,2015,41(4):1096-1103.WANG Xia,WANG Chencheng,ZHU Youyu,et al.Space charge profiles in XLPE nano dielectrics used for HVDC plastic cable insulation[J].High Voltage Engineering,2015,41(4):1096-1103.
[22]KOLESOV S N.The Influence of morphology on the electric strength of polymer insulation[J].IEEE Transactions on Electrical Insulation,1980,EI-15(5):382-388.
[23]王威望.LDPE/Al2O3纳米复合电介质界面区特性与击穿关联的研究[D].陕西:西安交通大学,2015:10-12.WANG Weiwang.Investigation on correlation between interface characteristics and breakdown in LDPE/Al2O3 nanodielectrics[D].Shaanxi,China:Xi’an Jiaotong University,2015:10-12.
[24]DONGLING M,TREESE A H,RICHARD W S,et al.Influence of nanoparticle surface modification on the electrical behaviour of polyethylene nanocomposites[J].Nanotechnology,2005,16(6):724-731.