雷击高塔地闪回击电磁辐射特征研究

发布时间：2018-10-20 17:36

【摘要】：高塔更易形成上行先导,因此更易成为雷电击中的目标,而高塔的暂态效应,使得雷击高塔产生的电磁辐射与雷击地面的情况存在明显差异。关于雷击高塔的电磁辐射已有大量研究,然而土壤色散效应对于雷击高塔电磁辐射的影响尚未开展。所谓土壤色散效应,是指在不同频率条件下,土壤电参数表现出不同的特征。在低频条件下,土壤电参数趋于恒定,可以假定土壤电参数恒定；而在高频条件下,土壤电导率会变小。此外,目前雷电回击电磁场在中高层高度的研究,均假定雷电击中地面,未考虑高塔存在的影响。因此,本文主要研究了土壤色散效应对雷电回击电磁辐射的影响,以及高塔暂态效应对于中高层高度电磁瞬态特征的影响。本文通过对不同色散模型的对比分析,选取了相关性系数最优的色散模型用于雷击高塔的回击电磁场计算,讨论了土壤色散效应对雷击高塔回击电磁场的影响条件,在此基础上,对雷击高塔电流峰值反演因子FCCFs(Field-to-Current Conversion Factors)进行了修订。此外,本文研究了雷击高塔回击电磁场在中高层高度的电磁场瞬态变化特征,对比雷击地面的情况,分析了高塔对中高层瞬态电磁场的影响。针对以上研究,取得具体成果如下：本文对比了六种色散模型,通过Kramers-Kronig检验,计算了各模型的相关性,选取了相关性最优的Portela模型。研究了雷击50-300 m高塔时,土壤色散效应对雷电电磁场沿地表面传播时的影响。研究发现,当考虑土壤色散效应时,雷击高塔电磁场沿地表传播时的衰减程度明显小于电参数恒定时的结果。当土壤恒定电导率大于0.01 S/m时,土壤色散效应的影响可以忽略,而小于0.001S/m时,则需要考虑色散效应的影响。比如,当土壤恒定电导率等于0.0001 S/m,考虑色散效应时,雷击300 m高塔在100 km处的电磁场峰值是恒定电参数情况下的2.5倍。利用研究结果修订了雷电流反演因子FCCFs,经过修订后的误差在10%以内,反演精度显著提高。本文还模拟了雷电击中50-300m高塔时中高层的瞬态电场,研究了高塔存在对中高层瞬态电场的影响。由于高塔对雷电流的暂态效应,对于波头时间RT在0.2us～2us范围内的继后回击电流而言,其产生的电场峰值增大,高频分量也相应增多。当波头时间RT减小或塔高增加,电场的峰值则越大。当RT为0.2us的雷电流击中300 m高塔时,在80k m高度、水平距离80 km处产生的辐射场是击中地面所产生的电场峰值的数倍；随着波头时间RT的增加,击中高塔的闪电在远场上的高塔存在的影响会逐渐变小。
[Abstract]:The tower is easier to form the upward lead, so it is easier to be the target of lightning strike, and the transient effect of the tower makes the electromagnetic radiation produced by the lightning tower is obviously different from that of the lightning strike ground. Much research has been done on the electromagnetic radiation of lightning tower, but the effect of soil dispersion on the electromagnetic radiation of lightning tower has not been carried out. The so-called soil dispersion effect refers to the different characteristics of soil electrical parameters under different frequency conditions. Under the condition of low frequency, the electric parameters of the soil tend to be constant, which can be assumed to be constant, but the conductivity of the soil becomes smaller under the condition of high frequency. In addition, the current research on the height of lightning return stroke electromagnetic field in the middle and high level assumes that the lightning strikes the ground without considering the influence of the tower. Therefore, the influence of soil dispersion effect on electromagnetic radiation of lightning return stroke and the influence of tower transient effect on high electromagnetic transient characteristics of middle and high level are studied in this paper. Based on the comparative analysis of different dispersion models, the optimal dispersion model with correlation coefficient is selected to calculate the electromagnetic field of lightning tower, and the influence of soil dispersion on the electromagnetic field of lightning tower is discussed. On this basis, the inversion factor FCCFs (Field-to-Current Conversion Factors) for the peak current of lightning tower is revised. In addition, this paper studies the transient characteristics of the electromagnetic field of the lightning tower at the height of the middle and high levels, compares the lightning strike on the ground, and analyzes the influence of the tower on the transient electromagnetic field of the middle and high levels. The results are as follows: in this paper, six dispersion models are compared, the correlation of each model is calculated by Kramers-Kronig test, and the optimal Portela model is selected. The effect of soil dispersion on the propagation of lightning electromagnetic field along the ground surface was studied when lightning struck 50-300 m tall tower. It is found that the attenuation degree of electromagnetic field of lightning tower is obviously less than that of constant electric parameters when considering the dispersion effect of soil. When the constant conductivity of soil is greater than 0. 01 S / m, the effect of soil dispersion can be neglected, but when the soil conductivity is less than 0. 01 S / m, the influence of dispersion effect should be considered. For example, when the constant conductivity of the soil is equal to 0.0001 S / m and the dispersion effect is considered, the peak value of the electromagnetic field of the 300m lightning tower at 100 km is 2.5 times higher than that under the constant electrical parameters. Based on the results of the study, the correction error of the lightning current inversion factor (FCCFs,) is less than 10%, and the inversion accuracy is improved significantly. This paper also simulates the transient electric field in the middle and upper layers when lightning strikes 50-300m tall tower, and studies the influence of the tower on the transient electric field in the middle and high layers. Because of the transient effect of tower on lightning current, the peak electric field and the high frequency component of wave head time RT in the range of 0.2us~2us increase. When the RT of the wave head decreases or the tower height increases, the peak value of the electric field increases. When the lightning current with RT of 0.2us hits the 300m tower, the radiation field at 80km height and 80 km horizontal distance is several times the peak value of the electric field generated by hitting the ground, with the increase of the wave head time RT. The impact of lightning striking the tower on the far field becomes smaller.
【学位授予单位】：南京信息工程大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P427.3;O441.4

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