3.3.4.2 Probabilities of damage in case of nearby lightning strikes

The probability P_M that a lightning flash near a structure will cause failure of internal systems in the structure depends on the measures taken for the protection of electrical and electronic installations (SPM). A grid-like lightning protection system, shielding measures, installation principles for the cables, an increased rated impulse withstand voltage, isolating interfaces and coordinated SPD systems are suitable protection measures to reduce P_M. 

The probability P_M is calculated as follows (Equation 3.3.4.2.1):