This diploma thesis addresses the optimization and verification of grounding systems for high-voltage transmission line towers. An effective grounding system is critical for protection against dangerous touch and step voltages and for preventing insulation back-flashovers during lightning strikes. Dimensioning often relies on generalized assumptions from the SIST-EN 50341-2-21:2023 NNA standard, which can lead to inadequate or over-dimensioned grounding systems.
Using the case study of the 110 kV Hudo–Kočevje transmission line (tower locations SM 84 and SM 86), lightning data from the SCALAR system were analyzed, along with field measurements of soil resistivity using the Wenner method—which served as the basis for multi-layer soil models developed in CDEGS—and grounding resistance measurements at individual tower locations. The effect of non-linear soil ionization under high impulse currents was also evaluated in the grounding resistance verification calculations.
The results show that using real lightning data from the SCALAR system enables a significantly more accurate determination of the required tower grounding resistance. This avoids over-dimensioning and directly reduces grounding tape trenching costs as well as the extent of unnecessary environmental impacts.
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