Investigation of Lightning Current Distribution in a Large-Scale Earth-Termination System of Photovoltaic Power Plant

The transient performance of large grounding grids subjected to lightning current impulses is studied in case of photovoltaic (PV) power plant. In this paper various numerical models have been developed which considers different parameters both geometry of grounding mesh system and soil. The maximum transient ground potential rise or GPR and frequency dependent impedance are analyzed in frequency and in transient domains. Simulation are based on Maxwell equations and Sommerfeld integrals used in XGSLab software package for grounding system analysis. Also, a prospective overvoltage between point of strike and a cabinet at a distance of 300 m is analyzed. A significant reduction of transient ground potential rise is possible only in cases when mesh sizes or separation between conductors are significantly smaller than estimated effective area during lightning performance. For different soil parameters an effective area was estimated in case of first positive lightning current. Also the possibility of reduction of maximal transient GPR as well as reduction of overvoltages between different parts of grounding grid with adjusting of span between conductors is investigated.