Analysis of Touch Potentials in Solar Farms

The grounding system in a solar farm has unique characteristics due to its extended footprint and varying type of grounding components. The changing physical properties of the soil within the perimeter of a solar farm result in the nonuniform resistivity of the top soil layers. Measurements of the as-built grounding grid could indicate higher grounding resistance than that predicted by design. Once this difference is detected, it is the duty of the designer to modify the existing grounding grid such that the touch potential is below the limits specified by the applicable codes. This paper presents the analysis of the touch potentials in solar farms and also provides some recommendations to reduce these potentials when the grounding resistance is higher than that predicted by the design. An actual grounding grid design and field measurements are used in an example to illustrate the concepts introduced in this paper.