The system grounding method option has a direct influence on the overall performance of the entire medium voltage network as well as on the ground fault current magnitude. IntroductionThe system grounding in power distribution substations is an This grounded system protection is particularly advantageous in rural areas, to solve the occurrence of lightning, birds and tree branches caused faults. In urban areas, with mostly permanent faults, resonant grounding system can also be used to guarantee electrical service continuity.Resonant grounding provides self-extinction of the fault arc in overhead lines for about 80% of temporary ground faults [3]. Considering that about 80 % of ground faults are temporary, we conclude that more than 60 % of overhead line ground faults clear without breaker tripping. Highimpedance grounded systems are grounded through a highimpedance resistor or reactor with an impedance equal to or slightly less than the total system capacitive reactance to ground. The neutral resistor is of such a high value that ground faults on such systems have very similar characteristics to those of resonant-grounded systems [4][5].In the next sections we will see different grounded systems and we will analyze their influence on the occurrence of a line-to-ground fault, and the influence of direct and resistive faults at different network points.