Computation of Transient Voltages on the Interconnected Grounding Grids

Grounding grids play a fundamental role to provide safety during electromagnetic transients and reliable operation of any electrical system under normal conditions. In this context, when lightning strikes a transmission line, surge currents will propagate to the electrical substations where grounding grids must dissipate these impulsive currents into the soil. Grounding grids are composed of horizontal bars welded with vertical forming a large mesh. Additionally, the interconnected grids are largely employed to guarantee safety for personnel and equipment in facilities. Due to several natural conditions, horizontal bars can be damaged and compromise the performance of the grounding grid in power plants. In this paper, transient voltages are computed for whole and damaged grids when lightning strikes a transmission line. Results have shown that there is a difference in the transient voltage peaks in these two conditions. To decrease these voltages, vertical rods are installed in the border of the grounding grids, which has been shown as an effectivesolution to lower these voltage peaks in the damaged grounding grids.