The aim of this paper is to present a grounding system modeling using a circuit network synthesized from its frequency response. This circuital representation allows simulating the grounding system in EMTP/ATP program considering its frequency dependent effects. Also, any electrical component may be included in the simulation, such as power system equipments or electronic devices. The frequency response was obtained by means of both an electromagnetic model based on the moments method (MM) and a hybrid electromagnetic model (HEM). The results were compared with previous works and field measurements, finding a good agreement.