Lightning Protection System (LPS) must provide a low-impedance path through its grounding system when a lightning strikes at the top of buildings. This grounding system is composed by combination of vertical (VE) and horizontal electrodes (HE) and a precise computation of its impedance must consider a stratified soil. Additionally, due to corrosion and electromagnetic forces, the electrode may present ruptures on connectors or welded parts. These factors affect the transient voltages along the grounding grid. In this paper, transient currents and voltages are investigated for a real LPS, subjected to a lightning strike, whose grounding system is buried in a homogeneous and stratified soil. In each condition, the grounding system is analysed under whole and damage state. In this study, a lumped approach for the VE and HE are obtained by the Vector Fitting technique and by the electromagnetic radiation theory (ERT), respectively. Results show that transient currents and voltages are affected by a rupture in the grounding electrodes; significant differences are more pronounced in high resistive homogeneous soil which may impact on the safety of people surrounding the LPS area.