مدل سازي صاعقه ي از نوع ابر به زمين بر اساس سرعت متغير انتشار موچ جريان در كانال صاعقه در مجاورت زمين تلفاتي

In this paper, a new method is presented to model a Cloud-to-Ground (CG) lightning return-stroke channel. In this method, the lightning channel is approximated by a lossy monopole antenna with distributed resistive-inductive load above a lossy ground. To determine the temporal-spatial current distribution along the channel, the governing electric field integral equation (EFIE) in frequency domain is solved numerically by the method of moment. As opposed to the conventional models, the proposed model enables one to assign the realistic value of unity to the relative permittivity of the surrounding medium. In addition, the channel speed can be appropriately adjusted using the distributed inductive loads along the channel. The latter enables one to assign a realistic propagation speed to the channel current. In addition, the inclusion of lossy ground in the proposed model further enhances its superiority over the conventional models for accurate modeling of a lightning channel. In fact, a lossy ground produces a nonzero horizontal component of electric filed whose value is found to be closer to its actual value for having a more realistic current propagation speed along the channel. To demonstrate the validity of the model, the current distribution along the channel and the radiated electromagnetic field are computed and compared with those obtained using the conventional Antenna Model (AT) models. A comparison of the results confirms the validity of the proposed model. It is also shown that, as opposed to the conventional AT models, the proposed model is capable of predicting the zero-crossing feature of electromagnetic fields waveform in a far range as observed in all measurement data.