Currents on Electric Installation Lines in Case of Equipotential Bonding at Roof Level

Main objective of this paper is to evaluate the maximum partial lightning currents, which enter a building on electric installation lines. The conductors of the installation lines are equipotentially bonded to the air-termination or downconductor system at roof level. For live conductors, the lightning equipotential bonding is realized by the use of surge protective devices (SPD) which have towithstand the threat of the partial 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 facades. If the building is additionallyequipped with a metal roof, or, if the roof, the ceilings and the pillars/walls consist of concrete with steel reinforcement, the maximum expected charge is 0.1 C. For buildings without shielding elements (metal roof, metal facade, reinforced concrete), the charge is much higher, in the range of several coulombs. The values only apply to building up to heights of about 15 m using copper, aluminum or steel for the air-termination and down-conductor system. The transferred charge is significantly higher, if the air-termination and downconductor system consists of stainless steel.