Rotational Invariance Technique for Evaluation of Perturbed Lightning Impulses

A spectrum estimation method is proposed for the evaluation of the mean curve required by ANSI/IEEE Std. 4-1995 for the determination of non-smooth lightning test voltages parameters. The method is based on the estimation of signal parameters via rotational invariance techniques. A decomposition procedure for deriving the mean curve of full lightning impulses with oscillations on front and crest and/or overshoot is presented. The results of analytical waveforms are compared with a similar method previously introduced in the literature. The application of the method does not introduce distortions to the recorded waveform; also, high accuracy, easy implementation, and noise immunity make this technique a superior one.