Modeling Grounding Systems Response to Current Impulses Considering Nonlinear Effects

Modeling grounding systems is necessary for the calculation of ground potential rise (GPR), power system simulations and insulation coordination studies. In this work, a methodology for estimating equivalent circuit parameters through the optimization of the time-domain impulse response was developed. It allows to obtain equivalent circuits with positive parameters that accurately represent grounding systems considering both effects related to frequency and soil ionization. Additionally, linear and nonlinear equivalent circuits for calculating the impulse response of typical grounding systems were proposed. The Nelder-Mead optimization method was applied to adjust the circuit parameters. For evaluating the methodology developed and the proposed models, data from impulse current tests was used. It was found that the use of nonlinear circuits increases the accuracy of the simulated response, resulting in errors of less than 4% in the estimation of GPR. The proposed methodology allows obtaining representative circuits of typical grounding systems used in the electrical system. The circuits can be used for systemic studies and calculation of GPR considering short-circuit or lightning currents.