On the Influence of an Elevated Terrain on the Grounding Resistance of a Vertical Rod

Abstract

In this paper, we analyze the grounding resistance of a vertical grounding rod located in an elevated terrain. Tall structures such as wind turbines and mobile phone base stations are often installed in remote and hilly locations to gain more power or to facilitate line of sight to end users. Those locations are at an increased risk of being struck by lightning due to the greater elevation compared to their surroundings. These hilly areas are usually very rocky with low soil conductivity. A proper grounding system is therefore of paramount importance. In this study, we analyze the influence of the elevated terrain considering a simplified cone and a truncated cone geometries as a function of the apex angle and top radius. It is shown that the grounding resistance can be significantly increased both, in the case of small mounds of only a few meters height, and in the case of a high hill or a mountain.

Grounding Resistance of a Hemispheric Electrode Located on the Top of a Finite-Height, Cone-Shaped Mountain

“…It has recently been shown that the grounding resistance can be significantly increased in the case of a non-flat terrain that effectively reduces the conductive volume for the injected current [11]. A similar degree of increase was obtained for both, hemispheric grounding electrodes [11] and vertical rods [12], suggesting that the increase in the grounding resistance is mostly governed by the soil geometry and not by the geometry of grounding electrode. Remote grounding can be one effective way of reducing the grounding resistance of structures located on mountaintops [13].…”

Reduction of a Cone-Shaped Terrain Grounding Resistance by Remote Grounding

“…This equation is valid for the case of a hemispheric grounding electrode at the tip of a cone-shaped mountain (for the geometry, see Fig 2 . in [8]). In [8], it was shown that the same coefficient can be used for the case of a vertical rod as a good approximation. Fig.…”

“…The influence of a nonflat ground on the grounding resistance of structures was recently analyzed in [7]. It was shown [7,8] that the grounding resistance of structures located on the top of mountains can be significantly higher than the grounding resistance of the same structure located on a flat ground.…”

“…In Section III, three different case studies are discussed. First, for the sake of completeness, we present the analytical solution for a vertical grounding electrode in a flat ground (II.A) as well as the worst-case scenario results from [8] for the case of a grounding at the tip of a cone-shaped mountain (II.B). We will also discuss the more realistic case of a vertical grounding rod located at the tip of a truncated cone-shaped mountain and we will analyze the reduction of the resistance with the use of a remote grounding along the mountain (II.C).…”