云南典型土壤冲击特性研究与火花放电现象分析

发布时间：2018-05-09 13:57

本文选题：土壤基质结构 + 团聚性　；参考：《西南交通大学》2017年硕士论文

【摘要】：土壤是接地系统性能的决定因素,因此近年来国内外学者针对土壤的阻抗特性开展了大量的研究工作,现有的研究多用细砂替代土壤,反而忽略了土壤的结构差异可能引发的导电性异常。本论文通过开展实验,对比研究云南红粘土与细砂的冲击导电特性,提出土壤基质结构差异对其冲击特性的影响规律;增加不同规格结构接地极在粘土环境中的冲击试验,探究粘土的火花放电特性;最后结合试验过程中出现的问题分析雷电冲击波形对接地极接地电阻的影响,为统一简化冲击试验提供理论支持。本文首先分析了不同基质结构土壤的导电机理;搭建了土壤冲击实验平台,通过实验方法研究了受不同基质结构影响的土壤冲击特性。实验结果表明:对于基质为非团聚性结构的土壤,在相同含水量条件下,土壤的冲击电阻率、临界击穿场强和击穿时延随着土壤粒径的增大而增大,并受到土壤孔隙率和粒径均匀度的影响;对于基质为团聚性结构的土壤,土壤的冲击特性不符合以上规律,且在相同含水量时,红粘土的导电性要弱于均匀粒径的砂质土;同时得出用细砂替代土壤开展土壤冲击特性研究是片面的。然后开展粘土环境下不同规格结构接地极的冲击试验,发现粘土环境下:一端注入方式下的较短水平接地极周围土壤发生的火花放电效应较强;接地极夹角对土壤火花放电效应的影响较小;方框型接地极具有均压功能,当方框边长增大时,周围土壤的火花放电效应会减弱;表面积越小的接地极周围土壤越容易发生火花放电现象;以及在接地极所用钢材总长一定时,方框型接地极的接地效果要优于方框+射线型接地极。而对于方框+射线型接地极而言,在用料总长一定的条件下,增加方框边长的降阻效果要差于增加射线长度。最后分析研究了电压电流冲击波形、极性对不同结构接地极冲击接地电阻的影响规律,并从电荷量、连续性和火花放电角度分析以上规律的产生依据。结果表明:在相同冲击波幅值条件下,冲击接地电阻随冲击波的波前时间每减少50%其近似降低5%,而随半波时间每增加一倍其近似降低5%;仅改变冲击极性时,正极性冲击下的冲击接地电阻要比负极性冲击下的小,且最多减小10%;电流波形控制冲击与电压波形控制冲击在接地冲击实验中的作用效果是一致的,为简化冲击试验可用电压控制替代电流控制。
[Abstract]:Soil is the decisive factor of the performance of grounding system. Therefore, in recent years, scholars at home and abroad have carried out a lot of research work on the impedance characteristics of soil. On the contrary, the structural differences in soil may lead to electrical conductivity anomalies. In this paper, the impact and conductivity characteristics of Yunnan red clay and fine sand were compared and studied, and the influence of soil matrix structure difference on impact characteristics was put forward, and the impact test of ground pole with different size structure in clay environment was added. Finally, the influence of lightning shock wave shape on grounding resistance of earth electrode is analyzed, which provides theoretical support for unified simplified impact test. In this paper, the electrical conductivity mechanism of soils with different substrate structures was analyzed, and a soil shock test platform was set up, and the impact characteristics of different substrates were studied by means of experimental methods. The experimental results show that the impact resistivity, critical breakdown field strength and breakdown delay increase with the increase of soil particle size under the condition of the same water content for the soil with non-agglomeration structure of the substrate, and under the same water content, the soil impact resistivity, critical breakdown field strength and breakdown delay increase with the increase of soil size. Under the influence of soil porosity and particle size uniformity, the impact characteristics of soils with aggregate structure do not conform to the above laws, and the conductivity of red clay is weaker than that of sandy soils with uniform particle size when the water content is the same. At the same time, it is concluded that it is one-sided to use fine sand instead of soil to study soil impact characteristics. Then the impact tests of the ground poles with different specifications were carried out in the clay environment. It was found that under the clay environment, the spark discharge effect of the soil around the short horizontal grounding poles with one end injection was stronger than that under the clay environment. The influence of the corner angle on the soil spark discharge effect is relatively small, the square type earth pole has the function of voltage equalization, when the side length of the square frame increases, the effect of the surrounding soil spark discharge will be weakened. The smaller the surface area is, the more easily spark discharge occurs in the soil around the earth pole, and when the total length of steel used in the earth pole is fixed, the earthing effect of the square type earth electrode is better than that of the square ray type earth pole. For the square ray type ground pole, the drag reduction effect of increasing the side length of the square frame is worse than that of increasing the ray length under the condition that the total material length is fixed. Finally, the influence of the voltage and current shock wave shape and polarity on the grounding resistance of different structures is analyzed, and the basis of the above rule is analyzed from the angle of charge quantity, continuity and spark discharge. The results show that under the same shock wave amplitude, the shock grounding resistance is approximately reduced by 5% for every 50% reduction of the wave front time of the shock wave, and approximately reduced by 5% with each doubling of the half wave time, and when the shock polarity is changed only, The impact grounding resistance under the positive polarity shock is smaller than that under the negative polarity shock, and the maximum reduction is 10%, and the effect of current waveform control impulse and voltage waveform control impulse in the grounding impact experiment is the same. In order to simplify impulse test, voltage control can be used instead of current control.
【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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