A maximum current derivative of 28.56 kA/µs is obtained from Figure 2 (the risetime of this current derivative waveform is 157.4 ns). Figure 3 shows a current wavefront of 11.53 kA peak (first peak) and a risetime of 795.4 ns.
The minimum current wavefront risetime of lightning strokes recorded in 1999 is 96.9 ns. The fastest rise of the current derivative waveform recorded in the same year has a risetime of 35.9 ns. The wavefront time characteristics and the cumulative statistics of current wavefront parameters are of major importance for the planning of experiments for the measurement of the lightning current as well as for the design of protective means from lightning, especially for tall structures or other structures erected on high ground.
In 1999, the current measuring system recorded 94 strokes of 28 flashes. The 1999 cumulative statistics of current wavefront parameters (maximum steepness, first current peak and the 10%-90% risetime) are shown in Figure 4 to 6, respectively