Abstract
In this paper a general set of field expressions associated with a lightning channel are proposed to evaluate the electromagnetic fields due to lightning in the presence of a ground reflection at the channel base. The ground reflection factor is due to the difference between the channel and ground impedances and can enter additional reflected currents into the lightning channel. The proposed field expressions can support the widely used current functions and current models directly in the time domain without the need to apply any extra conversions. Moreover, the proposed expressions are applied on a sample of lightning current that has been obtained from a triggered lightning experiment and the evaluated electromagnetic fields are compared to the corresponding measured fields and the results discussed accordingly. The results illustrate that the simulated fields based on the proposed method are in good agreement with the measured fields. Moreover, the ground reflection factor can have a great effect on the values of the lightning electromagnetic fields. The proposed field expressions consider all field components directly in the time domain and vary appropriately to join with widely used coupling models to evaluate the lightning induced voltage on power lines without the need to apply any extra conversions.