Why is Iimp important?
IEC 62305 standard requires a maximum impulse current value of 25 kA per pole for three-phase system. This means that for a 3P+N network the SPD should be able to withstand a total maximum impulse current of 100kA coming from the earth bonding.
Imax: Maximum discharge current
This is the peak value of a current of 8/20 碌s waveform that the SPD is capable of discharging once.