What type of waveform is referenced when discussing the nominal discharge current for SPDs?

The correct answer refers to the 8/20 µs waveform, which is widely recognized in lightning protection and surge protective device (SPD) standards. This waveform represents the typical characteristics of a current surge resulting from a lightning strike or other transient events.

In the context of SPDs, the 8/20 µs waveform indicates that the current rises to its peak value in approximately 8 microseconds and then decays to half that value in about 20 microseconds. This format is critical because it mimics the nature of real lightning currents, providing a standard for testing and guaranteeing that SPDs can adequately handle the transient currents that they are designed to protect against. This standardization enables manufacturers to evaluate their devices' performance rigorously and ensures that they can respond effectively to actual lightning-induced surges in electrical systems.

Understanding the 8/20 µs waveform helps professionals in implementing the correct SPDs for protecting infrastructural and electronic equipment from electrical overstress resulting from lightning strikes.