Impulse Impedance Modeling and Application of Tower Grounding Device
Guo Lei1, Gu Weifu1, Liu Bin1, Zeng Yi1, Chen Sixiang2
1. School of Electrical Engineering Southwest Jiaotong University Chengdu 611756 China; 2. Foshan Power Supply Bureau of Guangdong Power Grid Co. Ltd Foshan 528000 China
Abstract:Tower grounding impedance is one of the main influencing factors of lightning trip accidents on transmission lines. In the mountainous and hilly areas of China, the tower usually has a large impulse grounding resistance, which causes frequent line trip accidents. Based on the combination of finite element method and circuit theory, this paper explored the impulse characteristics of typical soils in Guangdong and established a precise grounding transient model of transmission lines. Based on this model, an optimization method for the impulse resistance reduction of transmission towers in rock zones was studied. The results show that for grounding devices with rock formations below the earth surface, the application of external grounding electrodes with short conductors and external grounding electrodes with vertical grounding electrodes has a better optimization effect. If the short conductors are used to match external grounding electrodes, the effect of reducing the resistance is the best when the length of the short conductor is 3%~6% of the external grounding conductor and the spacing of the short conductors is 10%~14% of the external grounding conductor. If the vertical grounding electrodes are used to match external grounding electrodes, the effect of reducing the resistance is the best when the vertical grounding electrodes are placed at the outermost ends of the external grounding conductors. The results can provide reference and theoretical support for grounding transformation and optimization of mountain towers.
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