Parameter evaluation for lightning impulse with oscillation and overshoot using the Eigensystem Realization Algorithm

This paper presents a novel approach for the evaluation of impulse parameters. The approach is based on the eigensystem realization algorithm (ERA) which produces a state space model to fit the impulse waveform. Instead of the conventional static mathematical curve model, the dynamic state space model gives a more exact fit for all types of impulse waveforms. This paper demonstrates the feasibility of decomposing the impulse waveform into various components such as smooth, overshoot, oscillations, and high frequency noise etc. Using the presented method it is possible to accurately extract the individual component, even for the overshoot or low frequency oscillation, in analytic functions without significant distortion of the original waveform. Depending on the identified oscillation frequency or overshoot duration, the unwanted components can be removed for the construction of the mean curve. Once the mean curve is obtained and described by analytic functions, the Newton-Raphson method can be performed to the computation of the impulse parameters with high accuracy. Results obtained with analytic and measured impulses show its applicability