Ground Potential Distribution and Human-Body Touch Voltage in Old Residential Communities

Electric shock in residential buildings always is an issue of concern. This paper investigated both ground-surface potential and touch voltage in old residential communities under a phase-to-ground fault. The PEEC method is adopted for numerical simulation by including the coupling model of buried conductive parts and the human-body branch circuit in an electric-shock event. It is found that compared to the dedicated vertical grounding rod, the wire mesh of the building foundation causes the potential to decrease slowly with increasing distance, and accordingly reduces the touch voltage. The touch voltage inside a building is generally dangerous in the case of an indoor fault. It is found that by bonding the conductor mesh to the dedicated grounding rod, touch voltage in the community can be reduced under all possible fault conditions. Such bonding can even reduce the touch voltage at the outdoor equipment away from the building. This measure is effective for the fault up to the building entrance, and effective in all cases if local equipotential bonding is taken. It is also found that including the human-body branch circuit in the simulation will lead to an increase of ground-surface potential, but a decrease in touch voltage outside a building. This measure will not alter the results arising from the indoor evaluation. Nevertheless, the results without considering the human body branch circuit may be treated as worst-case results.