Relationship between Oscillating Impulse Waveform and the Base-Curve under Lightning Impulse Test

Overshoot magnitude is defined by the difference between the extreme value of the recorded voltage curve and the maximum value of the base curve. And relative overshoot magnitude is defined by the ratio of the overshoot magnitude to the maximum value of the base curve. Therefore the estimation of the maximum value of the base curve is very important to determine the relative overshoot magnitude. This paper deals with the determination of base curve and proposes the calculation procedure of the base curve based on the analysis of oscillating waveform. Examples illustrate with the difference between the definitions of relative overshoot magnitude.