Ground flash density and lightning exposure of power transmission lines

Lightning is one of the major causes for outages in electric distribution and transmission networks. Data provided by a lightning location system in Austria allows detailed correlation of reported outages and the corresponding lightning discharges. Even within the small region of the Austrian territory the lightning flash exposure of HV transmission lines varies in a range from 0.6 to 2.6 km^-2yr^-1. A comparison of the actual observed lightning related line outages with calculated estimates based on the IEEE flash program show an underestimation of the outage rate by the flash program by a factor of about 2.