3. OBSERVATIONS
A typical CN Tower lightning current derivative signal,
captured by the old Rogowski coil, and its corresponding
current (time integral of the current derivative signal)
representing the overwhelming majority of CN Tower
lightning current derivative impulses are shown in Figs. 2
and 3, respectively. This measured signal is one of 474
fast-rising negative impulses recorded at the tower during
one decade (1992-2001). (It is worth mentioning that
current impulses having wavefront peaks lower than 2 kA
have not been used in the analysis presented in this paper.)
Reflections from the tower’s structural discontinuities are
visible in Figs. 2 and 3, especially the ground reflection
arriving after 3.2 ms. The first current peak, representing
the original injected lightning current is not affected by
reflections and is used for statistical analysis. It is called
the wavefront peak.