Attractive Zone of Lightning Rods Evaluated with a Leader Progression Model in a Common Building in Brazil

Modeling the lightning attachment process is required on any method to design the air-termination elements of a lightning protection system. An attachment model that adopts the leader progression concept is used to evaluate the three-dimensional attractive zone of a lightning rod on a common 54-m tall building in Sao Paulo, Brazil. Electric field and scalar potential distributions are calculated numerically with a finite element method. The result is compared with the interception volume predicted by the electro-geometric model, as applied by the rolling sphere method. The results show that the electrogeometric theory underestimates the striking distance and the attractive radius. Moreover, in the presence of upward connecting leaders, the striking distance varies according to the field enhancement on the geometry of the structure and the lateral displacement of the stepped leader. The simulated propagated distances and speeds of the downward and upward leaders are compared with a recently published high-speed video analysis of a natural lightning attachment case observed on the evaluated lightning rod. A reasonable agreement between the simulated and measured leader characteristics has been found.