Surge protective devices selection for true installations

This paper intends to show how to select SPDs in practical applications when standards only gives general rules. This addresses the selection of voltage protection level Up and the value of current Iimp. Based on these two values an SPD can be determined and appropriate selection of these two parameters is then important. IEC 62305-2 allows to determine the Lightning Protection Level (LPL). Based on this, the current circulating inside an SPD can be determined using simple calculation or a more sophisticated one. Based on the LPL, the probability of protection of the SPD can also be determined and this is related to the current withstand of the SPD and also to its voltage protection level even if this last parameter is less easy to assess in spite of being fundamental.