When lightning strikes the PV system, it causes induced transient current and voltage within the PV system wire loops. These transients appear at the equipment terminals and can likely cause insulation and dielectric failures within the solar PV electrical and electronics components (such as PV panels, inverter, combiner box, control and communications equipment, and so on).

Surge Protective Devices (SPD, also called surge arresters and suppressors), are designed to protect electrical installations and equipment against transient current and voltage. The protection usually shall be based on system level, not merely targeted at specific devices. Without proper surge protection, sensitive electronic equipment can easily be damaged and even create fire hazards.

The SPD are connected in parallel with the equipment; the equipment has a high impedance. Once a transient overvoltage appears in the system, the impedance of the SPD decreases so surge current is driven through the SPD, bypassing the sensitive equipment.

Figure 5-1shows an example of a solar inverter surge protection scheme. SPDs are installed on the AC side, DC side, and communication interfaces of the inverter.

Figure 5-1 Example of Solar Inverter Surge Protection Scheme