Contents of large current flashes among all the lightnings measured on transmission lines

"I (amplitude of lightning current" vs. "P(I)) (probability of stroke current amplitude exceeding I)" characteristics are published in many papers. These are given by a single curve or by a functional formula of "I" regardless of the isokeraunic level in the districts where the transmission lines are passing. The author analysed the results of lightning current measurement in Japan, and found that the I vs. P(I) characteristic curves vary depending on the intensity of lightning in the district concerned. In other words, the content (%) of large current lightning (larger than 80 kA) is larger in heavy lightning districts than in mild lightning districts.