Modelling the lightning return-stoke current using Heidler function

Different functions have been used to model the lightning return-stroke current with the aid of direct current measurements at tall structures. In this paper, a comparison between the Pulse function and Heilder function is carried out to determine the suitability of each of these functions for simulating the lightning return-stroke current, measured at the CN Tower. An automated system for estimating the lightning return-stroke current waveform parameters from the measured current derivative signal will be introduced. The curve fitting technique of the system, initial values and feasible regions of the function parameters will be discussed. Also, the idea of using an artificial lightning signal free of noise and reflections as a reference signal for evaluating the parameter extraction system will be presented. Finally, the lightning return-stroke current waveform parameters (peak, maximum rate of rise, risetime, pulse width, decay time and charge) are expressed in term of the Pulse or Heidler function parameters.