Statistical distributions of current amplitudes and lightning incidence number to structures of various configurations

摘要

On the basis of probability statistical distribution of negative lightning return stroke current amplitudes (I) related to events occurred from cloud to ground (or short structures) and using electrogeometric model (EGM), the statistical distributions of currents are recalculated and number of strikes are estimated for the structures of different configurations considering their geometrical shape and dimensions (cylindrical, parallelepiped, hangar types, buildings having round and rectangular internal openings). Some characteristics of distributions are retrieved (I, I, I, mode). Simulation is performed and results are compared for different EGM parameters, in particular, for two extreme relations of striking distance (rolling sphere radius) and current peak: R=10·I and R=1.9·I. Results show significant difference in estimated number of strikes obtained by EGM approach (N) and by simplified standard approach (N) using calculation of the so-called collection area of the structure (3H-zone, where H is the structure height). For example, for the cylinder-type structure having height of 110 m and radius of 5 m when assuming relation R, the calculated number of strikes is reduced about N/ N =9.4 times. For the hanger having roof shaped as portion of cylinder surface (B×L×H=250×165×110 m), this ratio is about 6.1. Probability density and cumulative distributions of stroke current amplitudes, and lightning incidence number are calculated both for external surfaces of the structure and, if present, for its internal openings (stadium-type). In latest case, the upper limit of penetrating currents is also determined.