The tower footing grounding system of a transmission line is important for dissipating lightning currents, thereby reducing overvoltage and flashover across insulators. This paper presents the influence of the length of the grounding wire on the transient voltage of the tower grounding system and across insulators of an overhead transmission line rated at 220 kV. The impact of the length of the tower's grounding wire on the outage rate of the transmission line due to lightning is also determined and evaluated. Additionally, a characteristic curve illustrating the relationship between the effective length of the ground wire and the threshold of lightning current required to cause flashover across insulators is established. The research results are based on the EMTP/ATP electromagnetic transient program and COMSOL software. These findings will assist power utilities in managing and operating transmission lines by providing a reference for designing and selecting the appropriate length of grounding wire to ensure both effective lightning protection and economic considerations.