Surge protection can be divided into three levels: coarse protection, medium protection and fine or equipment protection. For this purpose, surge protective devices (Surge Protective Devices = SPD) are used, which are divided into three categories in DIN EN 61643-11. Coarse protection is achieved by a lightning arrester (SPD type 1), which is installed on the electrical house connection box or at the meter point in order to dissipate high partial lightning currents to earth. However, there is still an overvoltage that is harmful to electrical/electronic devices.
For medium protection, surge protection devices (SPD type 2) are installed in the sub-distributor, which reduce the voltage level in the cable network and thus protect the installation and building technology. For fine protection, for example, surge protection sockets (SPD type 3) are installed, which reduce the voltage to such an extent that electrical/electronic equipment is no longer damaged.
Source: bauwion
