Analysis of the Influence of Soil Stratification Models on Different Grounding System Configurations

Abstract

Grounding has great importance in power electrical systems. The main parameter to evaluate its performance is the impedance, which can be estimated in the design stage using the conductors geometry and a soil stratification model based on measures of soil resistivity. In this context, this work performed a comparative analysis of one-layer and two-layer stratification models. The frequency response associated to each of the soil models considered was calculated for two different grounding systems and used to obtain the grounding response to a 8/20-$$\upmu $$s current impulse. Differences of up to 44% were obtained for impedance at low frequency, and it was verified that the homogeneous soil model underestimates grounding impedance. That may lead to a worse-to-expected performance during short-circuit or lightning. It can be concluded that the modeling of the soil with the homogeneous model is discouraged when designing a grounding system for substations.