IEC 61000-4-24:2015 deals with methods for testing protective devices for HEMP conducted disturbance. It includes two-terminal elements, such as gas discharge tubes, varistors, and two-port SPDs, such as HEMP combination filters. It covers testing of voltage breakdown and voltage-limiting characteristics but also methods to measure the residual voltage and/or the residual current, peak rate of rise and root action for the case of very fast changes of voltage and current as a function of time. It has the status of a basic EMC publication in accordance with IEC Guide 107. This second edition cancels and replaces the first edition published in 1997. This edition constitutes a technical revision.