杆塔接地极冲击散流效率影响因素及多频率组合测量方法研究

发布时间：2018-01-16 11:47

本文关键词：杆塔接地极冲击散流效率影响因素及多频率组合测量方法研究　出处：《西南交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：输电线路杆塔接地装置是雷击输电线路时雷电流重要的泄流通道,优化杆塔接地装置结构、降低杆塔接地装置冲击接地电阻措施等研究工作,对于降低输电线路雷电反击跳闸率具有重要意义。由于输电线路杆塔分布地形复杂,常规的大型冲击电流发生器很难开展现场测量,准确地测量冲击接地电阻并获取其变化情况对于电力系统的防雷工作意义重大。本文首先建立500kV典型杆塔接地体仿真模型,通过研究发现:冲击泄漏电阻可以反映杆塔接地装置各个导体段的散流能力,提出确定杆塔接地装置外部射线有效散流长度的依据;通过分析土壤电阻率与有效散流长度之间的关系,推出有效散流长度的计算公式,并且发现土壤电阻率越低其射线有效散流长度越短;并通过研究典型杆塔接地装置的优化布置方式,发现在射线总长度一定的情况下,当其小于总的有效散流长度时,延长单根射线长度的降阻效果要优于增加射线数量,而当射线总长度高于总的有效散流长度时,结论则相反。然后研究了不同长度垂直接地极的影响范围;垂直接地极数量、长度对于杆塔接地装置降阻效果的影响。通过研究发现不同长度垂直接地极影响范围不同:10m长垂直接地极的影响范围大约为40m,而3m和5m长垂直接地极的影响范围分别为5m和20m;在所添加垂直接地极总长度相同的情况下,所采用单根垂直接地极的长度越长,则降阻效果越好;随着垂直接地极数量的增加,其降阻率都不断趋向饱和。推荐在泄漏电流弱的地方添加尽可能长的垂直接地极,然后再根据其影响范围增加合适的垂直接地极数量。其次研究了土壤电阻率、换土方式以及换土范围对于杆塔接地装置降阻效果的影响;通过研究发现换土所使用的土壤电阻率越低起到的降阻效果越好,仅对接地装置的四根射线进行换土便能起到很好的降阻效果,其中推荐的换土深度为1.1m,换土总宽度为6m。最后研究了测量接地极的冲击接地阻抗的方法,并通过仿真分析该方法与有限元计算结果的偏差,给出了雷电流响应测量时所需的频率点数量。最后,本文利用实验验证了该方法与直接采用冲击电源测量结果的一致性,实验结果表明,无论是实验室试样还是实际杆塔,在相同的测量接线方式下,采用冲击装置测量和利用本文提供的方法进行测量,测量的结果基本相同。
[Abstract]:The grounding device of transmission line tower is an important discharge channel of lightning current when lightning strikes transmission line. The research work is to optimize the structure of tower grounding device and to reduce the impact earthing resistance of tower earthing device. It is of great significance to reduce the lightning strike tripping rate of transmission lines. Due to the complex terrain of transmission line tower distribution, it is difficult for the conventional large-scale impulse current generator to carry out field measurement. It is of great significance to accurately measure the impulse grounding resistance and obtain its variation for the lightning protection of power system. Firstly, this paper establishes the simulation model of 500 kV typical pole tower earthing system. It is found that the shock leakage resistance can reflect the diffusing capacity of each conductor section of the tower grounding device, and the basis for determining the effective beam length of the external ray of the tower earthing device is put forward. By analyzing the relationship between the soil resistivity and the effective diffusing length, the formula for calculating the effective diffusing length is deduced, and it is found that the lower the soil resistivity, the shorter the ray effective diffusing length. By studying the optimal arrangement of the typical tower grounding device, it is found that when the total ray length is fixed, it is less than the total effective diffusing length. The drag reduction effect of prolonging the length of single ray is better than that of increasing the number of rays, but when the total length of ray is higher than the total effective scattering length, the conclusion is opposite. The effect of the number and length of vertical earthing poles on the resistance reduction effect of tower earthing devices. It is found that the influence range of vertical earthing poles of different lengths is about 40 m, and the influence range of vertical earth poles of different lengths is about 40 m. The influence ranges of 3m and 5m long vertical earth poles are 5 m and 20 m, respectively. When the total length of the added vertical earth pole is the same, the longer the length of the single vertical earth pole is, the better the resistance reduction effect is. As the number of vertical earths increases, the resistance reduction rate tends to saturate. It is recommended to add as long as possible vertical grounding poles where the leakage current is weak. Secondly, the effects of soil resistivity, soil change method and soil exchange range on resistance reduction effect of pole tower earthing device are studied. Through the study, it is found that the lower the soil resistivity, the better the resistance reduction effect, and the better the resistance reduction effect can be if only the four rays of the earthing device are changed. The recommended depth of earth exchange is 1.1 m and the total width of soil exchange is 6 m. Finally, the method of measuring the impact earthing impedance of the earth pole is studied, and the deviation between the method and the finite element calculation result is analyzed by simulation. The number of frequency points needed for lightning current response measurement is given. Finally, the agreement between the method and the measurement results of direct impulse power supply is verified by experiments, and the experimental results show that. No matter the laboratory sample or the actual pole tower, under the same measuring connection mode, the measurement results are basically the same by using the impact device and the method provided in this paper.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM862

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