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| Non-Uniform Gas Convection in UHV-GIL and Insulation Margin Analysis for Tri-Post Insulator |
| Du Boxue, Dong Jia′nan, Liang Hucheng |
| Key Laboratory of Smart Grid of Education Ministry School of Electrical and Information Engineering Tianjin University Tianjin 300072 China |
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Abstract In recent years, gas insulated transmission lines (GILs) have been widely applied in power systems because of their excellent performances including high transmission capacity, low power loss, strong environmental adaptability, etc. Under the current carrying condition, the joule heat generated from the central conductor can raise the conductor temperature to 70~80 ℃, causing a radial temperature gradient between the conductor and the shell. Under temperature gradient, SF6 gas convection is formed, changing the designed insulation margin of tri-post insulators, which threats the safe operation of UHV-GIL. At present, more attention is paid to the problem of electric field distribution during checking the insulation performance of UHV-GIL, and the influence of thermal-fluid field distribution on gas dielectric strength is seldom considered. Therefore, this paper analyzed the insulation margin of the UHV-GIL tri-post insulator considering the non-uniform gas convection effect.
The simulation model of the electric-thermal-fluid field in a horizontally laid 1 100kV GIL was established to explore the effects of the temperature and the gas density distributions inside the GIL on the breakdown strength of the insulation gas. Then, the insulation margin analysis for the tri-post insulator was conducted based on the current reference values of the designed electric field considering the gas convection effect. Finally, the discharge inception voltage based on the volume-time theory was calculated considering the electric field and the gas density.
Results show that under the large current-carrying condition (8 000A), the GIL conductor temperature reaches 78.1 °C, reducing the local gas density and the dielectric strength by 15%. To keep the insulation margin, the reference value of the designed electric field should be lowered accordingly. The revised allowable electric field strength considering the gas convection is 20.4 kV/mm in the SF6 gap, is 10.2 kV/mm on the insulator surface and is 3 kV/mm inside the insulator and on the insert surface, respectively. At the peak time of the lightning impulse voltage, the tangential electric field along the tri-post insulator is concentrated in the post leg region of the insulator, whose maximum value is 8.9 kV/mm and is below the revised allowable electric field strength. While the normal electric field along the tri-post insulator is concentrated in the spherical area of the insulator, whose maximum value is 18.5 kV/mm. The synthetic field strength in the SF6 gap is up to 20.5kV/mm at the connecting sleeve, which exceeds the revised allowable electric field strength under the large current-carrying condition. Under the rated power frequency voltage, the electric field strength on the insert surface is 3.25 kV/mm, which does not meet the electric field design specification. The load induces the discharge inception voltage to drop by 11.6%. Gas discharge easily occurs around the upper post of the insulator, because the warm SF6 gas with low density and dielectric strength goes up by buoyancy.
Since the gas convection has an evident impact on the insulation performance of GIL, the structure and parameter of the tri-post insulator should be adjusted to satisfy the current carrying condition. The research results are expected to provide references for the optimization design of GIL tri-post insulators.
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Received: 04 November 2021
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[1] 梁虎成, 杜伯学, 陈允, 等. 基于迭代算法的功能梯度绝缘子介电常数分布优化[J]. 电工技术学报, 2020, 35(17): 3758-3764.
Liang Hucheng, Du Boxue, Chen Yun, et al.Permittivity distribution optimization of functionally graded insulator based on iterative method[J]. Transactions of China Electrotechnical Society, 2020, 35(17): 3758-3764.
[2] 李文栋, 王超, 陈泰然, 等. 550kV GIS盆式绝缘子小型化设计(二): 介电分布优化[J]. 电工技术学报, 2022, 37(11): 2743-2752.
Li Wendong, Wang Chao, Chen Tairan, et al.Compact design of 550kV basin-type spacer in gas insulated switchgear(part Ⅱ)—dielectric distribution optimization[J]. Transactions of China Electrotechnical Society, 2022, 37(11): 2743-2752.
[3] 李祎, 张晓星, 傅明利, 等. 环保绝缘气体C4F7N研究及应用进展Ⅰ: 绝缘及电、热分解特性[J]. 电工技术学报, 2021, 36(17): 3535-3552.
Li Yi, Zhang Xiaoxing, Fu Mingli, et al.Research and application progress of eco-friendly gas insulating medium C4F7N, partⅠ: insulation and electrical, thermal decomposition properties[J]. Transactions of China Electrotechnical Society, 2021, 36(17): 3535-3552.
[4] 陈向荣, 黄小凡, 王启隆, 等. 温度和频率对环氧树脂/碳化硅晶须复合材料交流非线性特性的影响[J]. 电工技术学报, 2022, 37(15): 3897-3912.
Chen Xiangrong, Huang Xiaofan, Wang Qilong, et al.Effect of temperature and frequency on AC nonlinear properties of epoxy resin/silicon carbide whisker composites[J]. Transactions of China Electrotechnical Society, 2022, 37(15): 3897-3912.
[5] 吴细秀, 程诗敏, 周帆, 等. 母线通流温升对GIS内绝缘特性影响的仿真研究[J]. 高压电器, 2020, 56(2): 7-14.
Wu Xixiu, Cheng Shimin, Zhou Fan, et al.Influence of temperature rise due to rated-current flowing through busbar on the internal insulation characteristics of GIS: a simulation study[J]. High Voltage Apparatus, 2020, 56(2): 7-14.
[6] 王增彬, 刘姝嫔, 周宏扬, 等. GIS盆式绝缘子温度多物理场仿真方法[J]. 高电压技术, 2019, 45(12): 3820-3826.
Wang Zengbin, Liu Shupin, Zhou Hongyang, et al.Multiphysics simulation method for GIS epoxy spacer temperature[J]. High Voltage Engineering, 2019, 45(12): 3820-3826.
[7] 高璐, 贾云飞, 汲胜昌, 等. 环保型1100 kV GIL用三支柱绝缘子多物理场耦合仿真及校核[J]. 高电压技术, 2020, 46(3): 987-996.
Gao Lu, Jia Yunfei, Ji Shengchang, et al.Multi-physical field coupling simulation and verification of tri-post insulator on environment-friendly 1 100 kV GIL[J]. High Voltage Engineering, 2020, 46(3): 987-996.
[8] 陈敬友, 高兵, 杨帆, 等. 气体绝缘输电线路温升数值计算及绝缘气体换热能力[J]. 高电压技术, 2020, 46(11): 4042-4051.
Chen Jingyou, Gao Bing, Yang Fan, et al.Numerical calculation of temperature rise of gas insulated transmission lines and heat transfer capability of insulating gases[J]. High Voltage Engineering, 2020, 46(11): 4042-4051.
[9] Hering M, Speck J, Großmann S, et al.Influence of gas temperature on the breakdown voltage in gas-insulated systems[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2017, 24(1): 401-408.
[10] 路士杰, 张连根, 周宏扬, 等. 温度对工频下环氧支柱沿面闪络电压的影响[J]. 高电压技术, 2019, 45(9): 2774-2781.
Lu Shijie, Zhang Liangen, Zhou Hongyang, et al.Effect of temperature on flashover voltage of epoxy column at power frequency[J]. High Voltage Engineering, 2019, 45(9): 2774-2781.
[11] 吴泽华, 田汇冬, 王浩然, 等. 特高压GIL哑铃型三支柱绝缘子优化设计方法[J]. 电网技术, 2020, 44(7): 2754-2761.
Wu Zehua, Tian Huidong, Wang Haoran, et al.Optimization design method for UHVAC GIL dumbbell type tri-post insulators[J]. Power System Technology, 2020, 44(7): 2754-2761.
[12] 张施令, 彭宗仁, 王浩然, 等. 盆式绝缘子多物理场耦合数值计算及结构优化[J]. 高电压技术, 2020, 46(11): 3994-4005.
Zhang Shiling, Peng Zongren, Wang Haoran, et al.Numerical calculation and structural optimization of multi-physical field coupling for basin insulator[J]. High Voltage Engineering, 2020, 46(11): 3994-4005.
[13] 张震, 林莘, 余伟成, 等. C4F7N/CO2和C4F7N/N2混合气体热力学物性参数计算[J]. 高电压技术, 2020, 46(1): 250-256.
Zhang Zhen, Lin Xin, Yu Weicheng, et al.Thermodynamic calculation of physical properties of C4F7N/CO2 and C4F7N/N2[J]. High Voltage Engineering, 2020, 46(1): 250-256.
[14] Hermann K.Gas-insulated transmission line (GIL)[M]. Germany: Wiley-IEEE Press, 2011.
[15] 黎斌. SF6高压电器设计[M]. 4版. 北京: 机械工业出版社, 2015.
[16] 张亮, 何聪, 李军浩, 等. 振荡雷电冲击电压下气体绝缘组合电器中极不均匀场击穿特性研究[J]. 电工技术学报, 2020, 35(12): 2672-2680.
Zhang Liang, He Cong, Li Junhao, et al.Breakdown characteristics study of non-uniform field in gas insulated switchgear under oscillating lightning impulses[J]. Transactions of China Electrotechnical Society, 2020, 35(12): 2672-2680.
[17] 何彦良, 丁未, 孙安邦, 等. 电场不均匀系数对SF6/N2混合气体负直流电晕电流脉冲特性的影响[J]. 电工技术学报, 2021, 36(15): 3124-3134.
He Yanliang, Ding Wei, Sun Anbang, et al.Effect of electric field non-uniformity coefficient on current pulse characteristics of negative DC corona in SF6/N2 gas mixtures[J]. Transactions of China Electrote-chnical Society, 2021, 36(15): 3124-3134.
[18] Hayakawa N, Miyaji Y, Kojima H, et al.Simulation on discharge inception voltage improvement of GIS spacer with permittivity graded materials (ε-FGM) using flexible mixture casting method[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2018, 25(4): 1318-1323.
[19] 张刘春. SF6替代气体c-C4F8及其混合气体的绝缘性能研究[D]. 上海: 上海交通大学, 2007. |
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2023, Vol. 38 
