Optimal Arrangement of Long Vertical Rods to Reduce Ground Resistance considering Their Shielding Effect

Grounding system is very important for the safety of the electric power grid, which should have small enough grounding resistance. Long vertical rods are usually used to reduce the grounding resistance of a grounding grid if it is impossible to increase the area of the grid. Although increasing the number and the length of the long vertical rods could make the grounding resistance smaller and smaller, the cost will increase greatly. What is more, due to the shielding effect among the rods, the effectiveness to reduce the grounding resistance will decrease if two vertical rods are too close to each other or the rods are too long. Therefore, the efficient way to use the long vertical rods is an interesting topic for engineers. In this paper, the shielding effect among the long vertical rods is discussed with the help of numerical calculation. The effect of the distance between two nearby rods and the depth of the rod on the shielding effect is analyzed in homogeneous soil and in two-layered soil with different reflection coefficients. The optimal parameter for the long vertical rod in different cases is put forward. The results may be a reference for the design of grounding grid.