Avaliação da impedância impulsiva em um sistema de aterramento.

Abstract

In this work was realized an experimental study for the analysis of impulsive impedance behavior in a grounding grid. In order to evaluate the impulsive impedance, were applied to the soil electric current impulses (representing lightning discharges) with several front times and amplitudes. So, a high current impulse generator was used. The impulse generator was charged with different voltage levels from 15 kV to 35 kV. The configuration of the generator initially chosen provided the injection of current impulses 8/20 μs at different amplitudes. Also, in order to analyze the behavior of the impulsive impedance at different wave front times, the capacitor's charging voltage was established in 20 kV and the impulse generator parameters (RLC) was changed. The injection of current impulses into the soil was made possible using a steel grounding rod coated with copper buried into the ground. The data acquisition was performed with a four-channel digital oscilloscope. The applied voltage was measured using a high voltage probe and current was obtained by a shunt resistor. The results showed that when the analysis variable was the charging voltage of the impulse generator, impulsive impedance became increasingly lower as the rising voltage applied to the soil. The results showed that when the analysis variable was the front time of the applied current signal, the impulsive impedance varied inversely proportional to the front time of current signal applied.