Extreme weather events in power system could lead to damages resulting into huge financial losses and serious safety issues. One such event is lightning strikes in which high amount of current could flow through lines and substations. The earthing system should be able to discharge such a high amount of current safely to the ground. This paper investigates impacts of frequency of lightning voltage on earth potential rise of a substation. The modelling and simulation of earth and energization parameters are implemented using the current distribution, electromagnetic fields, grounding, and soil structure analysis (CDEGS) tool. The results show that low frequency lightning strikes and high frequency lightning strikes result into different voltage gradients on a substation grounding system. As a result, grounding system designed for a particular frequency strikes may not provide adequate safety against strikes at other frequencies. Safety risks can vary with different frequencies of lightning strikes.