SMA module kit for AC surge protection type I and II. AC surge protection is necessary to protect electrical devices from voltage spikes. Also called overvoltage, and lightning is a well-known example. Surge protection creates potential equalization which leads to neutralization of voltage differences. This keeps all connected solar panels and inverters undamaged.
Type I surge protection is designed to provide protection against a direct lightning strike. Type II has a lower rating than type I and only protects against indirect lightning strikes. See info link for combination with an inverter.