Metodologia de avaliação de sistemas de aterramento submetidos a impulsos de corrente elétrica.

Abstract

In this work, a methodology of evaluation of grounding systems subjected to current impulses is proposed based on the amplitude and frequency of the impulse, the configuration of the grounding system and the resistivity of the soil that surrounds the grounding system. Experimental field tests and computational simulations were performed on grounding systems subjected to impulse currents with amplitudes between 1 kA and 2.5 kA and front time between ͳͲ μs and ͵Ͳ μs. Field tests were performed for two different configurations of grounding systems and different electrical characteristics of the soil. The results in the field were used to propose two models that represent the grounding system from the characteristic curve of the relation between measured voltage and applied current (V×I). In comparison to a reference model in the literature, the proposed models presented greater ease of calculation of their parameters and implementation with only linear elements. By presenting themselves as a simple and reliable configuration, the proposed models can be coupled, with greater ease and flexibility, to programs of electromagnetic transient analysis and in insulation coordination studies. The results obtained from the field tests were also used to prove computational simulations performed in XGSLab® software. The simulation of the grounding system was generalized considering the variation of the input parameters and the inductive and capacitive effects. As proof of concept, a methodological procedure was proposed for the grounding systems evaluation capable of identifying the effects caused by high intensity and high frequency phenomena. The methodological procedure allows the representation of the performance of grounding systems, through the use of models obtained from tests, as well as of computational simulations, in traditional programs of electromagnetic transient analysis.