Protection against lightning overvoltages: Approach and tool for surge protective devices selection

The present paper deals with the protection of low voltage apparatus against surges due to lightning to a structure, or to the line or to ground nearby the line supplying the apparatus. An approach is proposed to evaluate the performance of a Surge Protective Device (SPD) system in protecting apparatus, and to select, ultimately, the system able to provide the required performance in terms of probability of damage. An easy-to-use tool is introduced and discussed. Selected graphs are presented to help the designer to evaluate the probability of damage of an apparatus despite the installation of an SPD system and two examples of application of the proposed procedure are discussed. Conclusions that are drawn can be useful for the revision of the international standard IEC 62305 series.