Aterramentos encapsulados por concreto - avaliação do tipo de cimento na resposta elétrica

Abstract

Electrical grounding is extremely important for energy generation, transmission and distribution systems. Its main objective is to provide an earth connection with a sufficiently low impedance, in order to protect people and equipment. In the meantime, it is known that, in soils with high resistivity and in spaces with a small available area, the construction of a grounding that meets regulatory criteria becomes challenging. Therefore, grounding improvement techniques can be used, one of the most promising being the use of concrete around the grounding electrodes, thus forming groundings encapsulated by concrete. On the other hand, although it is expected that the electrical properties of concrete are strongly influenced by the type of cement used, water/cement ratio and mix, there are few studies in the literature that point out the influence that these concrete components have on its electrical resistivity, from a perspective of use in grounding encapsulated by concrete. Therefore, this work initially presents a study of concrete resistivity for three different types of cement and three water/cement ratio values, that is, nine concrete possibilities. Then, a grounding was constructed with a concrete-encased rod, using the most promising concrete among those evaluated. Such grounding had its respective grounding resistance measured and compared with a conventional bare rod. Finally, the results obtained indicated that concrete prepared with type CP – V cement and a water/cement ratio of 0.7 presented the lowest resistivity values observed. Furthermore, the rod encapsulated by concrete provided a resistance 20% lower than the conventional rod, after 30 days of measurement