The transient overvoltages (surges) that appear in PV plant installations are produced by different phenomena and may be:
- Due to direct lightning strikes on the external protection system
- Due to direct strikes and their induced currents distributed over the power grid
- Transmitted from the power grid, originating from atmospheric causes or from switching in the lines
- Caused by variations in the electrical field as a result of lightning
The heart of a PV system is its inverter, and that is why it should be the focus of protection against lightning and voltage surges. To properly protect the inverter, surge protection devices (SPDs) should be fitted on both the DC and AC sides. These devices must comply with EN 61643-11 Part 11: (Surge protective devices connected to low-voltage power systems – Requirements and test methods), and must be installed according to technical specification CLC/TS 50539-12:2010: (Low-voltage surge protective devices – Surge protective devices for specific application including d.c. Part 12 Selection and application principles – SPDs connected to photovoltaic installations).
In addition, PV panels and their metal supports must be connected to the grounding system.