Wavefront characteristics of the lightning current measured at the Toronto CN tower

Lightning strikes to the Toronto CN Tower have been monitored since 1978. In this paper, a detailed description of the current measuring system installed at the Tower in 1990 and extended in 1997 is given. Typical current derivative and current waveforms of CN Tower strikes are presented. Cumulative statistics of the wavefront characteristics of lightning currents (maximum steepness, wavefront peak and risetime) measured at the CN Tower in 1999 are derived. These statistics have led to recommendations concerning instrumentation and techniques for the proper measurement of lightning currents especially for those encountered at elevated objects.