Efficiency of the earthing system in a large-scale solar power plant during lightning

Abstract

The efficiency of a large earth-termination system (ETS) in case of a large-scale solar power plant (LSP) is crucial for protecting the facility and ensuring the safety of personnel and equipment during lightning events. The transient performance of the ETS for LSP subjected to lightning current impulses is studied in this paper. A suggested numerical model considers different ETS configurations, lightning strike locations, and parameters of the surrounding soil. The maximum transient ground potential rise (GPR) and frequency dependent impedance are analysed in both frequency and in time domains. The earth resistance is compared with the impulse impedance of the observed ETS.Simulations are based on the Partial Equivalent Electrical Circuit (PEEC) method using the XGSLab [1] software package for grounding system analysis. Due to simulation of the different ETS configurations, it is possible to find a favourable configuration for reduction of the GPR and thus to reduce the energetic stress on the installed surge protective devices (SPDs). In this approach, an impulse effective area is considered, which depends on the soil resistivity and the steepness of the lightning current. As a result, a mesh size of the ETS or distances between ground conductors of the grounding grids must be smaller than the estimated impulse effective area. This is often overlooked in the design of the ETS of LSP.