Share of the Lightning Current on Electric Installation Lines Within a Building Considering Equipotential Bonding at Roof Level

The main objective of this paper is to evaluate the maximum share of the lightning current, which enters a building on electric installation lines. The conductors of the power circuit are equipotentially bonded to the air-termination or down-conductor system at roof level. For live conductors, the lightning equipotential bonding is realized by the use of surge protective devices (SPD), which have to withstand the threat of the share of the lightning current. The most important parameter is the maximum transferred charge, which was calculated by the use of the computer code CONCEPT II. The maximum expected charge is about 0.6 C for buildings with metal façades. If the building is additionally equipped with a metal roof, or, if the roof, the ceilings and the pillars/walls consist of reinforced concrete, the maximum expected charge is 0.1 C. For buildings without shielding elements (metal roof, metal façade, reinforced concrete), the charge is much higher, in the range of several coulombs. The values only apply to spark-type SPD and to building up to heights of about 15 m using copper or aluminum for the air-termination and down-conductor system. The transferred charge is significantly higher, if the air-termination and down-conductor system consists of stainless steel.