Optimum Position of a Grounding Wire within a Building for Reduction of Lightning Surge Voltages

Abstract:
When a building is struck by a lightning, a high surge voltage between a grounding wire within the building and a building structure is produced. An effective grounding method and a position of the grounding wire for reducing the overvoltage are proposed in this paper. The overvoltage is evaluated by means of a numerical electro-magnetic field analysis method and by experiments using a scaled-down building model. The lightning current flowing into outside pillars is larger than that into a center pillar because of the skin effect. The maximum voltage between the grounding wire and a structure depends on the current distribution. The characteristic of the maximum voltage versus distance between the grounding wire and a structure is independent from the building configuration. The transient voltage is reduced by 40 % when the grounding wire is installed nearby the center pillar, and by 54 % when the common grounding method is also applied. The grounding wire installed nearby the center pillar is the optimum position for reducing the overvoltage.