Time-Domain Geoelectrical Modeling and Experimental Validation of Ground Potential Rise in Multilayer Soil Structures during Fault Events

Accurate characterization of subsurface electrical behavior during high-energy fault events is critical for both geotechnical safety assessment and the protection of power infrastructure. This study presents a geophysically driven, time-domain modeling framework for Ground Potential Rise (GPR) in multilayer and anisotropic soils, integrating electromagnetic field theory with physics-informed arc resistance modeling. The methodology employs apparent resistivity profiling and soil impedance mapping, enabling high-resolution simulation of current density and voltage gradients under realistic subsurface conditions. A coupled numerical-experimental approach is implemented: finite-element simulations incorporating layered earth resistivity are calibrated against controlled fault injection tests using scaled grounding grids in stratified soil. The model achieves an average deviation of less than 4.7% from measured GPR and step/touch voltages, demonstrating strong predictive reliability. Results reveal that conventional steady-state and homogeneous soil assumptions can underestimate hazardous step voltages by up to 63% and misrepresent the spatial extent of GPR zones by more than a factor of two. Comparative analyses show that optimized grounding grids reduce surface current densities by over 90% compared to isolated systems, significantly enhancing compliance with safety thresholds. Beyond its immediate application to substation and renewable energy grounding, the framework offers a transferable geoelectrical tool for infrastructure risk mapping, lightning hazard assessment, and geotechnical site evaluations in complex soil environments.