Lightning current distribution in the components of cladding structure

Results on numerical simulation (NS) of lightning current distribution in components of round standing seam cladding structure are presented. NS was performed by using 3D models of two types: large-scale model (#1), better reproducing conditions for current distribution in natural cladding; small model (#2), reproducing the sample for laboratory tests. Analysis included cases related to injection of lightning current having different standard waveforms (approximations) and variation of some parameters (halter's fastening contact area, channel radius and length). Scaling effects on using small test samples are addressed and recommendations for selection of adequate current parameters during tests are provided. In particular, in approach of equivalent frequency, for impulse waveform 10/350 μs and basic dimensions of the cladding components, current magnitude portion distributed into main halter (under the strike point) for the small model #2 (13.5 %) is obtained about twice bigger than that for the large one #1 (7 %). For continuous current, corresponding current portions are almost identical for both models: #1 - 45%, #2 - 43.5%. More accurate proportions of possible magnitude correction can be determined in further studies by considering closer waveform approximation and tests.