Effects of Overvoltage on Mesh-Distributed and Edge-Distributed Rods in Rectangular Ground Grid Systems of High Voltage Substations

In this study, the rectangular ground grids of the high voltage substations equipped with two different patterns of rods, including mesh-distributed and edge-distributed rods, were analyzed for the effects of overvoltage by using ATP/EMTP simulation program. By following the IEEE standard 80-2000, these two rectangular ground grids were designed to have the same area size of 324 square meters and then used for simulation by injecting the fault current of 25 kA at the center and corner of ground grids. The overvoltage occurred across the diagonal line and at the corner of these two rectangular ground grids were measured and compared with the calculated grid potential rise (GPR). The results showed that lower levels of overvoltage were found on mesh-distributed rods than on edge-distributed rods perhaps due to the possibility that overvoltage may disperse symmetrically on mesh-distributed rods and resulting in quickly distribution of overvoltage to ground soil. The results from this study can be useful for future designing of the ground grid systems of high voltage substations.