To investigate these concepts, assume that Berger's distribution having a median of 31.1 kA and a log standard deviation of 0.484 is valid for a conductor height of 30 meters. Using the IEEE-1992 equations, the required ground level distribution (which is lognormal) must have a median of 27.4 kA and a log standard deviation of 0.49. A plot of the median current as a function of conductor height is shown in Fig. 28 and reveals that the median increases sharply from 27.4 to 30.3 for a height
increase from 0 to about 1 meter. However, from 1 meter to 60 meters, the median current increases only to 32 kA. Thus the values of 3 1.1 and 0.484 are valid for all practical conductor heights.