The SPST12 is a combined type 1 and type 2 device for the 40mm busbar installation and fits perfectly in our ZSD boards. Availaible for TT/TN-C-S and TN-S grids it provides carefree protection against transient overvoltage caused by direct and indirect lightning strikes. AC protection Type 1/2 is often used where customers have a lightning protection system installed. The SPD fullfills all requirements of VDE 0100-534. Usually when an external lightning protection system is installed, an internal lightning protection system is also required for which the type 1/2 combination offers the best solution.