基于雷击高塔远距离电磁辐射特征的研究

Study on the Characteristics of Long Distance Electromagnetic Radiation Based on Lightning Tower

分别研究了理想地面(电导率无限大)和地面电导率有限情况下雷击高塔远场的变化情况。结果表明,在理想地面情况下,当雷电流的上升沿时间RT超过5h/c(h为塔的高度,c为光速)时,雷击高塔和雷击地面在距闪电通道水平距离为10 km到100 km的地表面处产生的水平磁场的峰值近似相等,但是,雷击高塔产生的场的上升沿时间比雷击地面的要短。在地面电导率为0.01到0.001 S/m的情况下,当雷击300 m的高塔时,利用传统公式反演得到的雷电流峰值会偏大,其误差在+5%到+17%之间,而且由于感应场分量的存在,使得当观测点与闪电通道之间的水平距离在20 km以内时反演结果的误差很大。当雷击50 m高塔时,利用传统公式得到的雷电流峰值的误差在-15%到+5%之间(正值代表反演结果偏大,负值代表结果偏小)。

We have studied the accuracy of the new general expressions for far-field-current factors presented by Bermudez et al. （2005,2007） for lightning strike to high tower on perfectly and finitely con- ducting ground, respectively, found that when the risetime of lightning current （RT） is beyond 5 h/c （h is the height of tall object and c is the light speed）, the field peak values for lightning strike to high tower are similar to that strike to flat ground at distances from 10 km to 100 km on the perfectly conducting ground, however, the field risetime is shorter for the lightning strike to high tower than that for the flat ground. For the finitely conducting ranging from 0.01 S/m to 0.001 S/m, when the lightning strikes the 300 m high tower, the lightning current peak from the measured magnetic field peak according to the tra- dition method is overestimated ranging about from ＋5% to ＋17% and the derivation value is more within distances of 20 km because of the effect of induction field component. When the lightning strikes the 50 m high tower, the predicted current peak according to the tradition method has an error within ＋5% to - 15% （Positive or negative mean that the results are larger or smaller）.