The SPD (surge protection devices), are intended to reduce the input surge to a lower value. This is accomplished with a strategy that integrates 3 protection levels: type 1, type 2 and type 3. Thereby achieving a low voltage level not dangerous for the electronic equipment.
There are different rules and regulations, the most important are the RBT (ITC-BT-23), EN 61643-11: 2012, IEC 62305-4.
The lightning strikes in the distribution lines or close to, or the lightning strikes in external protection system located in the same building or nearby.
They arise mainly as a result of lightning strikes, switching in the networks and/or defects therein.
It’s an over voltage with a big magnitude, about tens of kV and with a short duration (microseconds). However, they have a highly destructive power on sensitive electronic equipment.
They are the appropriate protection to avoid the surge in the power supply system, communications or data system.