Impulse efficiency of simple grounding electrode arrangements

Grounding basic function as the earth termination of the lightning protection systems is to effectively disperse the lightning current to earth without causing any danger to people or damage to installations. However, due to the inductive phenomena, the grounding performance might be much worse at high frequencies in comparison to low frequencies, which might deteriorate the efficiency of the protection during fast front lightning current pulses. This paper provides simple empirical formula for a first approximation of the impulse efficiency of some common arrangements of vertical and horizontal ground electrodes for typical lightning current waveforms. The effects of the soil ionization are disregarded; therefore, the new formula leads to a conservative estimate of the upper bound of the impulse impedance.