## 6 Conclusions  
The primary objective of this analysis was to provide insights concerning the operational efficacy of grounding systems of MV concrete poles facilitating interconnections between overhead and underground sections of power distribution networks via switching devices. Additionally, the goal was to examine and propose possible alternatives and improvements to the existing grounding systems. Through extensive simulations, the following key conclusions emerged:  
* In general, all examined grounding grids have a relatively dense design featuring a 4 \(\times\) 4 grid. * The efficacy of grounding systems is heavily contingent upon their installation location across the MV line. Notably, when an SC event occurs at a substantial distance from the HV substation, the resultant SC current is diminished. Consequently, grounding grids exhibit higher efficacy in mitigating the risk of hazardous touch and step voltages. * For all three grounding grids, operating on a uniform soil structure, a linear correlation exists between the total grounding grid resistance and the soil resistivity, as depicted in Figure 10.
* Regarding the GRID B alternative, enlarging the radius of the circular loop results in a lower resistance and, therefore, a slightly better performance when compared to GRID A. However, it should be noted that due to its dense and small design it is still ineffective in providing adequate protection against hazardous potentials. * Regarding GRID C, the incorporation of a grounding rod correlates with a notable 25% reduction in the maximum developed touch and step voltages, as depicted in Figure 11.
* All three grounding grid variations exhibit similar behavior regarding touch and step voltages; as such, they are ineffective in providing adequate protection against hazardous potentials. Therefore, it is imperative to incorporate a surface layer with high resistivity, ideally 2.500 \(\Omega\)m with at least 15 cm thickness. To elaborate further, as illustrated in Figure 11, when the grounding grid is placed in farmlands with soil resistivity ranging from 200 to 300 \(\Omega\)m, a top layer of 2.500 \(\Omega\)m resistivity with thickness more than 15-20 cm is considered necessary. Conversely, in regions characterizedby high soil resistivity exceeding 200 \(\Omega\)m, it is strongly recommended to incorporate a top layer of asphalt with a resistivity of 10.000 \(\Omega\)m.
* All three grounding grid variations exhibit relatively high resistance, reaching 40 \(\Omega\) when the soil resistivity is approximately 300 \(\Omega\)m. This holds critical significance, as at this resistance level, the magnitude of the total fault current diminishes significantly. Consequently, the overcurrent relay positioned at the departure point of the HV substation may fail to detect the fault for tripping purposes. Such a fault scenario could potentially evolve into a permanent fault, posing substantial risks to the safety of personnel and passersby. It is therefore imperative to avoid placing the grounding grid in soil structures with resistivity exceeding 300 \(\Omega\)m.
* If the fault clearing time exceeds the instantaneous operation of the circuit breaker (150 ms), the effectiveness of the grounding grids deteriorates significantly. One viable solution under such circumstances may be the addition of a top layer of asphalt. * Based on the findings extracted from Tables 1-3 in Appendix A, pertaining to a two-layer horizontal soil structure, it is evident that hazardous potentials (touch and step voltages) exhibit an upward trend with increasing soil resistivity in the upper layer. This phenomenon predominantly arises due to the positioning of the circular grounding grid loops within the upper layer, with only the grounding rods extending into the second layer. Consequently, when deploying grounding grids, DSOs should conduct comprehensive assessments of soil resistivity and ensure appropriate installation in the layer with the lowest possible soil resistivity.