Protective Measures for Medium-Voltage Cable Systems against Nearby Lightning Strikes to Ground

Due to their reduced exposure to environmental influences and their high reliability, mediumvoltage (MV) cables represent an increasingly important component of modern power distribution networks. Despite this, underground MV cables are not immune to the effects of atmospheric discharges. Lightning strikes to ground in the vicinity of underground cable routes may induce severe transient overvoltages, potentially resulting in breakdown of the outer polyethylene (PE) cable sheath. Such events can initiate moisture ingress, accelerate degradation of the cross-linked polyethylene (XLPE) insulation, and consequently reduce the service life of the cable system. This paper presents a summary of the simulations and numerical models developed to assess these phenomena. The simulation results are corroborated by laboratory testing performed on a MV cable sample. The results indicate that effective mitigation requires a coordinated approach, combining optimized cable design, controlled installation practices employing suitable conductive backfill materials and ducts, and the systematic installation of protective conductors (shield wires) above the cable trench. The application of these measures is therefore particularly relevant for underground cable installations in regions characterized by elevated lightning activity.