What do waveforms such as 8/20 and 10/1000 mean and how are they interrelated?
Lightning-induced surge currents are characterized as having very rapid rising front edges and long decaying tails. To a first approximation, the first number in each example of the above surge waveforms signifies the time taken for the surge to reach 90% of its peak value, and the second number, the time taken for this surge to decay from its peak to its half way value. These times are measured in microseconds, although convention does not require that this unit appear after the wave shape. The ratio between these different waveforms is a complicated function based on the integration of the energy content.
