Characterization of the lightning wave
Analysis of the phenomena allows definition of the types of lightning current and voltage waves.
- 2 types of current wave are considered by the IEC standards:
- 10/350 µs wave: to characterize the current waves from a direct lightning stroke (see Fig. J9);
- 8/20 µs wave: to characterize the current waves from an indirect lightning stroke (see Fig. J10).
These two types of lightning current wave are used to define tests on SPDs (IEC standard 61643-11) and equipment immunity to lightning currents.
The peak value of the current wave characterizes the intensity of the lightning stroke.
- The overvoltages created by lightning strokes are characterized by a 1.2/50 µs voltage wave (see Fig. J11).
This type of voltage wave is used to verify equipment's withstand to overvoltages of atmospheric origin (impulse voltage as per IEC 61000-4-5).