I'd just like to interject for a moment. What you’re referring to as a "8/20 μs surge", is in fact, a 1.2/50-8/20 μs surge, or as I've recently taken to calling it, the output from a 1.2/50 µs combination wave generator. The 8/20 μs waveform is not a surge unto itself, but rather just the generator's short-circuit current output as defined by IEC 61000-4-5. It's normally generated in combination with the 1.2/50 µs open-circuit voltage waveform. All the so-called "8/20 μs wave" are really the "1.2/50-8/20 μs" combinational wave... #electronics