山区雷击高塔影响架空线感应过电压的模拟研究

Simulation Study on the Induced Voltages of Overhead Line Influenced by Lightning Striking a Tower in Mountainous Terrain

为了研究山区雷击高塔对雷电感应过电压的影响,建立了三维时域有限差分(3D-FDTD)算法模型,计算复杂山体地形下的雷击高塔产生的电磁场,并结合Agrawal耦合模型计算架空线感应过电压。利用该模型计算对比了雷击平坦地面、雷击山顶和雷击山顶高塔时的线路感应过电压,并讨论了山体坡度、距离、塔高、土壤电导率的影响。结果表明:与雷击平坦地面相比,架空线感应过电压幅值随锥形山体坡度的增加而增大;当雷击山顶高塔时,线路两端的感应过电压幅值随着距离的增加而减小、随塔高的增加而增大、随电导率的降低而增大,与雷击山顶相比,雷击山顶高塔时线路两端的感应过电压波形产生了明显震荡,波形幅值进一步增大;以南京紫金山真实山区地形为例,模拟结果发现与雷击平坦地面相比,雷击山顶时的线路两端过电压幅值分别提高了43.5%和48.9%,雷击山顶高塔时的线路两端过电压幅值分别提高了50.2%和124.3%。

In order to study the induced voltages of overhead line influenced by lightning striking a tower over complex mountainous terrain, a three-dimensional finite-difference time-domain(3 D FDTD) algorithm model was proposed to calculate the electromagnetic fields due to lightning striking a tower over mountainous terrain, the lightning induced voltages are computed by means of Agrawal coupling model. The influence of lightning strike to idea flat ground, mountain top or a tall tower sitting on the mountain top was compared, and the effect of the mountain slope, the distance, tower height and soil conductivity on lightning induced voltages were evaluated. The results show that the induced voltage amplitudes on overhead line increase with the increasing cone-shaped mountain slope as compared with the case of flat terrain. When lightning strikes a tower on the mountain, the induced voltages decrease with increasing distance from the lightning channel, increase with increasing tower height and increase with the decrease of the soil conductivity, and produce obvious waveform oscillation and the amplitude increase significantly compared with lightning striking on the top of the mountain. The example of the Purple Mountain terrain in Nanjing shows that the induced voltages at the two ends of line due to lightning striking to mountain top are increased by 43.5% and 48.9%, and the induced voltages at the two ends of line due to lightning striking to a tower sitting on the mountain top are increased by 50.2% and 124.3% as compared with that for flat ground, respectively.