Evaluation of SPD protection distance in low-voltage systems

The paper deals with the evaluation of the protection distance of a surge protective device (SPD) for the reduction of the probability of failure of electrical and electronic systems within a structure. Surges due to flashes to the structure, to ground near the structure and to the entering lines are considered. Simple relations are proposed to evaluate the protection distance of an SPD to be effective against overvoltages due to resistive and inductive coupling with lightning current.