Malhas de aterramento em subestações energizadas: medições e análises.

Abstract

For many years, most of the measurement techniques applied to grounding grids were only possible to be used in de-energized substations. However, in the recent decades, several measurement techniques applicable to energized substations have been developed, whose main goal is to perform measurements that provide a fast grid evaluation, safely and without harming quality and continuity of power supply. In this work, six substations grounding grids were studied. Several analysis techniques of grounding grid conditions were applied in order to obtain more accurate and reliable diagnosis. For this, were applied known techniques, such as: measurement of ground resistivity, touch voltage and step voltage; and proposed techniques like: measurement of grounding resistance in energized installations and measurement of surface potentials, having their data treated and analyzed by a developed computational routine, based on the Finite Difference Method (FDM). The results of grounding grids resistance measurement, using the proposed method, were compared to results obtained through a traditional measurement method (de-energized substation) as well as those obtained through software simulation. Through the comparison of these results, the proposed technique was validated. The developed computational routine was able to calculate and display, through two-dimensional and three-dimensional graphics, the potentials distribution on the ground surface. The graphic analysis of the surface potentials through time allows monitoring and analysis of grounding grids conservation status. The diagnosis obtained from the set of used measurement techniques proved to be effective. Periodic measurements (semiannual) of grounding grids are recommended, in order to monitor and analyze its aging over time.