Effect of Voltage Stabilizer Grafting on Electrical Properties of 500 kV DC XLPE Cable Insulation Materials
Chen Xiangrong1,2, Huang Xiaofan1, Wang Qilong1, Zhu Hanshan1, Hong Zelin1
1. College of Electrical Engineering Zhejiang University Hangzhou 310027 China;
2. Zhejiang Provincial Key Laboratory of Power Semiconductor Materials and Devices Hangzhou Global Scientific and Technological Innovation Center Zhejiang University Hangzhou 311200 China
High-voltage direct current (HVDC) cables, serving as vital equipment for flexible DC power transmission, possess advantages such as extended transmission reach, substantial delivery capacity, and minimal power transmission losses. Currently, the most extensively utilized and mature insulation material for HVDC cables, both domestically and internationally, is cross-linked polyethylene (XLPE). Grafting organic substances is preferred to be used to enhance XLPE insulation performance than improving purity of XLPE base material or incorporating nano-fillers due to lower cost, higher stability, and better compatibility. Current domestic and international research on voltage stabilizers grafted onto XLPE is extensive, but there is scarce direct application in industrial insulating materials for 500 kV HVDC cables. Therefore, unsaturated aromatic small molecules are grafted onto the molecular chains of commercially available 500 kV HVDC XLPE insulation material in this work.
Firstly, pure XLPE samples are prepared with 1%, 3%, and 5% of 4-acetoxy styrene (AOS) grafted onto XLPE to acquire AOS-grafted XLPE (XLPE-g-AOS). Secondly, the samples are characterized using microscopic morphology, Fourier-transform infrared spectroscopy, differential scanning calorimetry, DC conductivity, space charge, DC breakdown, and thermally stimulated depolarization current tests. Thirdly, the effects of AOS grafting on the microstructure, crystallization characteristics, insulation properties, and micro-scale charge dynamics of the XLPE material are investigated, and the role of AOS grafting in charge carrier trap characteristics and charge transport is analyzed. Finally, quantum chemical calculations elucidate the physical mechanisms by which AOS grafting enhances the electrical properties of XLPE materials at the molecular level, and the relationship between micro-scale molecular structure, trap characteristics, charge behavior, and macroscopic electrical performance is established.
The results show AOS grafting results in a rougher cross-sectional morphology of XLPE-g-AOS. At an AOS content of 5%, AOS self-polymerizes to form nanoscale spherical particles. With increasing AOS content, the melting temperature and crystallinity of XLPE-g-AOS initially increase and then decrease. Among them, XLPE-g-AOS with a 3% content exhibits optimal crystallization characteristics. Moreover, AOS grafting reduces the DC conductivity of XLPE under high-temperature and high-electric-field conditions, decreases the accumulation of space charges, reduces electric field distortion, enhances the DC breakdown strength, and increases the shallow trap energy levels and quantities. Among them, XLPE-g-AOS with a 3% AOS content demonstrates the lowest DC conductivity, the least accumulation of space charges, the smallest electric field distortion, the highest DC breakdown field strength, and the largest shallow trap energy levels and quantities under high-temperature and high-electric-field conditions. When the AOS content increases to 5%, both the shallow trap energy levels and quantities of XLPE-g-AOS decrease, resulting in a decrease in breakdown strength and an increase in DC conductivity and electric field distortion.
The following conclusion can be drawn from the experimental and simulation analysis: The grafting of AOS induces a shift in the trap distribution of XLPE, introducing a greater number and denser arrangement of shallow traps. These traps manifest as both hole traps and electron traps, exhibiting high electrostatic potential. Consequently, a uniform and compact lattice of shallow traps is established within the XLPE matrix, facilitating the dissipation of energy during the frequent trapping and de-trapping processes of high-energy charges. This impedes the migration of charge carriers, ultimately enhancing the electrical performance of the grafted XLPE.
陈向荣, 黄小凡, 王启隆, 朱汉山, 洪泽林. 电压稳定剂接枝改性对500 kV直流XLPE电缆材料电气性能的影响[J]. 电工技术学报, 0, (): 239629-239629.
Chen Xiangrong, Huang Xiaofan, Wang Qilong, Zhu Hanshan, Hong Zelin. Effect of Voltage Stabilizer Grafting on Electrical Properties of 500 kV DC XLPE Cable Insulation Materials. Transactions of China Electrotechnical Society, 0, (): 239629-239629.
[1] 辛保安, 单葆国, 李琼慧, 等. “双碳”目标下“能源三要素”再思考[J]. 中国电机工程学报, 2022, 42(9): 3117-3126.
Xin Baoan, Shan Baoguo, Li Qionghui, et al.Rethinking of the “three elements of energy” toward carbon peak and carbon neutrality[J]. Proceedings of the CSEE, 2022, 42(9): 3117-3126.
[2] 饶宏, 黄伟煌, 郭知非, 等. 柔性直流输电技术在大电网中的应用与实践[J]. 高电压技术, 2022, 48(9): 3347-3355.
Rao Hong, Huang Weihuang, Guo Zhifei, et al.Practical experience of VSC-HVDC transmission in large grid[J]. High Voltage Engineering, 2022, 48(9): 3347-3355.
[3] 马鑫, 张怀垠, 吴继岩, 等. 温度对交联聚乙烯电缆尖刺缺陷局部放电特性的影响[J]. 高压电器, 2021, 57(5): 151-156.
Ma Xin, Zhang Huaiyin, Wu Jiyan, et al.Effect of temperature on partial discharge characteristics of needle defects in cross-linked polyethylene cable[J]. High Voltage Apparatus, 2021, 57(5): 151-156.
[4] Wang Shihang, Chen Peixing, Li Huan, et al.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.
[5] 董芸滋, 高嫄, 李秀峰, 等. 交联度对交联聚乙烯/有机化蒙脱土纳米复合材料拉伸性能和介电性能的影响[J]. 电工技术学报, 2023, 38(5): 1154-1165.
Dong Yunzi, Gao Yuan, Li Xiufeng, et al.Effect of crosslinking degree on tensile and dielectric properties of cross-linked polyethylene/organic montmorillonite nanocomposite material[J]. Transactions of China Electrotechnical Society, 2023, 38(5): 1154-1165.
[6] 张镱议, 赵梓炜, 刘捷丰, 等. 耐电晕聚酰亚胺薄膜研究进展[J]. 电工技术学报, 2023, 38(5): 1190-1205.
Zhang Yiyi, Zhao Ziwei, Liu Jiefeng, et al.Research progress of corona resistant polyimide films[J]. Transactions of China Electrotechnical Society, 2023, 38(5): 1190-1205.
[7] 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, 6911.
He Jinliang, Peng Simin, Zhou Yao, et al.Interface properties of polymer nanocomposites[J]. Proceedings of the CSEE, 2016, 36(24): 6596-6605, 6911.
[8] Deng Wei, Ren Yuanyuan, Qu Kexin, et al.Improved DC insulation performance of XLPE with graftable voltage stabilizer[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2022, 29(5): 1857-1864.
[9] 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, 4911.
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, 4911.
[10] 陈向荣, 洪泽林, 朱光宇, 等. 高温下电压稳定剂对交联聚乙烯电树枝化及局部放电特性的影响[J]. 电工技术学报, 2023, 38(3): 577-586.
Chen Xiangrong, Hong Zelin, Zhu Guangyu, et al.Effect of voltage stabilizer on electrical treeing and partial discharge characteristics of crosslinked polyethylene at high temperature[J]. Transactions of China Electrotechnical Society, 2023, 38(3): 577-586.
[11] 石逸雯, 陈向荣, 孟繁博, 等. 电压稳定剂及其含量对高压直流用500kV XLPE电缆材料绝缘性能的影响[J]. 电工技术学报, 2022, 37(22): 5851-5861.
Shi Yiwen, Chen Xiangrong, Meng Fanbo, et al.The effect of voltage stabilizer and its content on the insulation properties of 500kV HVDC cable insulation materials[J]. Transactions of China Electrotechnical Society, 2022, 37(22): 5851-5861.
[12] Englund V, Huuva R, Gubanski S M, et al.Synthesis and efficiency of voltage stabilizers for XLPE cable insulation[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2009, 16(5): 1455-1461.
[13] Lee S H, Park J K, Han J H, et al.Space charge and electrical conduction in maleic anhydride-grafted polyethylene[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 1995, 2(6): 1132-1139.
[14] 李春阳, 赵洪, 韩宝忠, 等. 电压稳定剂对交联聚乙烯直流绝缘性能的影响[J]. 中国电机工程学报, 2018, 38(23): 7071-7079, 7141.
Li Chunyang, Zhao Hong, Han Baozhong, et al.Effect of voltage stabilizer on the DC insulation properties of XLPE[J]. Proceedings of the CSEE, 2018, 38(23): 7071-7079, 7141.
[15] Li Chunyang, Zhang Chengcheng, Zhao Hong, et al.Grafted UV absorber as voltage stabilizer against electrical degradation and breakdown in cross-linked polyethylene for high voltage cable insulation[J]. Polymer Degradation and Stability, 2021, 185: 109498.
[16] Zhang Chengcheng, Wang Tingting, Sun Weifeng, et al.Grafting of antioxidant onto polyethylene to improve DC dielectric and thermal aging properties[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2021, 28(2): 541-549.
[17] Wei Zuojun, Liu Haiyan, Yu Linwei, et al.Delocalized aromatic molecules with matched electron-donating and electron-withdrawing groups enhancing insulating performance of polyethylene blends[J]. Journal of Applied Polymer Science, 2020, 137(39): 49185.
[18] Jarvid M, Johansson A, Englund V, et al.High electron affinity: a guiding criterion for voltage stabilizer design[J]. Journal of Materials Chemistry A, 2015, 3(14): 7273-7286.
[19] Hu Shixun, Zhang Wenjia, Wang Wei, et al.Comprehensive comparisons of grafting-modified different polypropylene as HVDC cable insulation material[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2022, 29(5): 1865-1872.
[20] 陈向荣, 玉林威, 刘海燕, 等. 电压稳定剂改善聚乙烯共混材料绝缘性能的研究[J]. 西安交通大学学报, 2019, 53(12): 87-96.
Chen Xiangrong, Yu Linwei, Liu Haiyan, et al.Insulating property enhancement of polyethylene blends by voltage stabilizers[J]. Journal of Xi’an Jiaotong University, 2019, 53(12): 87-96.
[21] Yamano Y.Roles of polycyclic compounds in increasing breakdown strength of LDPE film[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2006, 13(4): 773-781.
[22] 申作家, 罗智奕, 詹威鹏, 等. 基于介质体内陷阱参数与松弛过程的XLPE电缆绝缘热老化行为分析[J]. 中国电机工程学报, 2016, 36(19): 5382-5388, 5421.
Shen Zuojia, Luo Zhiyi, Zhan Weipeng, et al.Analysis on thermal aging behaviors of XLPE cable insulation based on trap parameters and relaxation process[J]. Proceedings of the CSEE, 2016, 36(19): 5382-5388, 5421.
[23] 付一峰, 陈俊岐, 赵洪, 等. 交联聚乙烯接枝氯乙酸烯丙酯直流介电性能[J]. 电工技术学报, 2018, 33(18): 4372-4381.
Fu Yifeng, Chen Junqi, Zhao Hong, et al.DC dielectric properties of crosslinking polyethylene grafted chloroacetic acid allyl ester[J]. Transactions of China Electrotechnical Society, 2018, 33(18): 4372-4381.
[24] 杨佳明, 王暄, 韩宝忠, 等. LDPE纳米复合介质的直流电导特性及其对高压直流电缆中电场分布的影响[J]. 中国电机工程学报, 2014, 34(9): 1454-1461.
Yang Jiaming, Wang Xuan, Han Baozhong, et al.DC conductivity characteristic of LDPE nanocomposite and its effect on electric field distribution in HVDC cables[J]. Proceedings of the CSEE, 2014, 34(9): 1454-1461.
[25] Tian Fuqiang, Bu Wenbin, Shi Linshuang, et al.Theory of modified thermally stimulated current and direct determination of trap level distribution[J]. Journal of Electrostatics, 2011, 69(1): 7-10.