Separation distance between external LPS and structure conductive parts

This paper presents a study on the overvoltages that appear across the separation distance between LPS and structure conductive parts when the former is struck by lightning. The overvoltage calculation is carried out in frequency-domain using the Method of Moments and the results are translated to time-domain by Fourier transform. The structure is represented by its steelwork and the voltages are computed for the standard waveforms corresponding to negative first strokes and subsequent strokes. The likelihood of insulation breakdown is assessed by the Equal Area Method, which takes into account the voltage waveform. It is shown that, for non-insulated LPS, sparks between LPS and structure steelwork are very likely to occur, both for first and subsequent strokes. The results support the proposal of bonding the LPS to the building steelwork, regardless of the condition of the latter. The paper also discusses how this issue is addressed in the international standard for lightning protection of structures.