Evaluation of Scaling Factors to move from Flash Density (Ng) to Ground Strike Point Density (Nsg)

Abstract:
The assessment of lightning risk to structures, and infrastructure has traditionally relied on the Flash Density (Ng) metric, representing the number of lightning flashes per square kilometer per year. However, recent studies have highlighted potential underestimations in Ng, particularly concerning ‘forked’ lightning or multiple ground strike points (Nsg). Ground Strike Point (GSP) algorithms emerged as a promising solution to accurately assess lightning risk. However, their complexity poses accessibility challenges to Lightning Protection System (LPS) designers and risk assessors. This study delves into the assessment of potential discrepancies between Ng and Nsg, leveraging data from the South African Lightning Detection Network (SALDN) and GSP algorithm implementation. The findings underscore the importance of region-specific evaluations and caution against a one-size-fits-all approach in scaling Ng to estimate Nsg. The proposed scaling factor of 2×Ng, while convenient, may lead to an overestimation of risk and inflated costs in LPS designs for South Africa