Optimisation of lightning current discharge to the ground in electrical networks: Introduction of the proportionality coefficient (K)

Abstract

The electrical network, essential to our society, frequently encounters disruptions from lightning strikes, resulting in material damage and power blackouts. Swift diversion of lightning currents to the ground is imperative to safeguard the grid. This study proposes a proportionality coefficient (K) to effectively distribute lightning current between grounding and network flow. The optimality of this coefficient depends on the tower grounding system resistances; lower resistances facilitate optimal distribution, enabling more current to flow to the ground. In the examination of the Djiri-Ngo power line in the Republic of Congo, grounding systems were optimised based on soil types. Three electrodes were used for clayey sand, while fifteen were employed for siliceous sand. Optimal coefficients were determined to be 0.86 for clayey sand and 0.81 for siliceous sand. These coefficients denote that 86% and 81% of the lightning current were directed to the ground, in contrast to non-optimal resistances (69% and 29% with a single grounding electrode). The experiments highlight the importance of adapting grounding systems to soil characteristics, rather than adhering to a uniform approach. Efficient diversion of lightning current to the ground is paramount for grid protection.