Lightning Surge Propagation on a Grounded Vertical Conductor

This letter addresses lightning surge propagation on a vertical conductor connected to the earth via a ground electrode. As the vertical conductor does not support the TEM mode of wave propagation, surge propagation is characterized with time- and position-variant surge impedance and attenuation coefficient of current. The reflection of a lightning surge at the ground then is addressed with the approach similar to the travelling wave theory. Expressions of the reflected surge excited by the current with a ramp or an arbitrary waveform are derived. Note that the reflected surge consists of two components with different attenuation rates. The traditional reflection coefficient is not applicable to the grounded vertical conductor. The results are numerically validated with the finite-difference time domain and partial element equivalent circuit methods.