Fronius Grid and System Protection:
Save costs by controlling the
inverter-integrated interface switch
Feature Guide
© Fronius International GmbH
Version 1 08/2020
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1 WHAT IS A GRID AND SYSTEM (GS) PROTECTION?
Grid and system protection is a protective device which constantly monitors the voltage and
frequency of the supply network for the specified switch-off conditions. The grid and system
protection activates the interface switch. The interface switch usually consists of two electrical
switchgear connected in series. The GS protection is used for safe disconnection of the
generating plant if the voltage and frequency limits in the power supply network are not
observed because of unwanted conditions in the grid or if an isolated system has formed.
2 VARIANTS FOR GRID AND SYSTEM PROTECTION
The normative requirements for GS protection vary from country to country. Grid operators,
too, sometimes require different designs or settings. For the sake of simplicity, the subject of
GS protection is described in this document using the example of Germany (according to
VDE-AR-N 4105:2018), as this country often plays a pioneering role with regard to norms
and standards.
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Figure 1: Inverter-integrated GS protection for systems up to 30 kVA
2.1 Inverter integrated grid and system protection
Grid and system protection is integrated in every typical inverter. The GS protection measures
the grid voltage and grid frequency and switches off the PV system via the integrated interface
switches as soon as the switch-off conditions are fulfilled. The GS protection and the redundant
interface switches are both located in the inverter. For PV systems with an output of up to 30
kVA, this GS protection inside the inverter is sufficient. No external GS protection is required.
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