Grid and PV system protection in accordance with VDE-AR-N 4105

The grid and PV system protection is a "type-tested protective device with a certificate of compliance" as per application guide VDE-AR-N 4105. This type-tested protective device with a certificate of compliance constantly monitors the voltage and frequency of the transmission line for compliance with the specified tolerances and prevents the formation of stand-alone grids.

For generating systems < 30 kW, the grid and PV system protection that is integrated into the inverters as standard is sufficient in Germany. For generating systems > 30 kW, however, external grid and PV system protection is required. Here it is absolutely necessary that an external monitoring unit with an integrated system protection relay is implemented. Whereas for systems up to 135 kW, the tie switch that disconnects the PV system from the utility grid does not necessarily have to be implemented externally, provided the standard requirements are complied with. Thus, the external grid and PV system protection consists of two components:

• Monitoring unit with a grid and system protection relay

• Tie switch that is switched via the system protection relay of the monitoring unit and disconnects the PV system in the event of a grid failure.

From firmware version 3.02.xx.R, the inverter offers the possibility to replace the external interface switch for disconnection from the grid with the optional SMA I/O Module.