Lightning density characteristics of the exponential distribution in Three Gorges area in Western Hubei during a decade

The Cloud-to-Ground (CG) lightning flash density is a very sensitive parameter in High Voltage Transmission Line Lightning Protection Project. Statistics show that lightning flashover accidents of the transmission line are proportional to Lightning density. Due to lightning activity is highly random, the average density during many years is used to measure the lightning characteristics in a given region. However, the fluctuation with time of lightning density is not defined by these parameters, thus it is necessary to estimate the probability of lightning density which is greater than the mean. This paper analyzes the statistical data of lightning location system (LLS) in the Three Gorges area in Western Hubei during 2000-2009. It concludes that propose lightning density obedience to exponential distribution in time domain, and derive that the bigger one between the mean and STD can be use for estimating lightning density expectations in the engineering.