Fronius Symo GEN24 10.0, Operating Instructions Manual, Page: 36 / 120

Cabling variants including emergency power cir-
cuits and 3-pin separation e.g. Austria or Australia
Functions - Measuring and transferring the required parameters for energy management and
Solar.web by the Fronius Smart Meter.
- Disconnecting from the public grid to enable operation in backup power mode if the
grid parameters are outside the country-specific standards.
- Reconnecting to the public grid when the grid parameters are within the limits spe-
cified by the country-specific standards.
- Option of having a separate backup power circuit or several backup power circuits
that are supplied even during failure of the public grid. The total load of the backup
power circuits must not exceed the nominal output of the inverter. Furthermore, the
performance of the connected battery must also be considered.
Transitioning
from feeding
energy into the
grid to backup
power mode 1. The public grid is monitored by the inverter's internal grid and system protection unit
and by the Fronius Smart Meter connected to it.
2. Failure of the public grid .
3. The inverter carries out the necessary measures according to the country standard
and then switches off.
Contactors K1 and K2 drop out. This disconnects the backup power circuits and the
inverter from the rest of the home network and from the public grid, as the main con-
tacts of the contactors K1 and K2 3-pin open. The inverter activates relay K3, which
interrupts the supply to contactors K1 and K2. This prevents unintentional activation
of contactors K1 and K2 and thus a grid connection when voltage is restored in the
grid. The NC auxiliary contacts of contactors K1 and K2 send feedback to the
inverter that the contactors are open (a condition for starting backup power mode).
4. The NO contact of relay K3 gives additional feedback to the inverter on whether the
locking was successfully performed by relay K3.
5. The inverter decides based on the contactors' feedback as well as the measure-
ments on the inverter terminals and the Smart Meter that backup power mode can
be started.
6. After all the required activation tests have been carried out, the inverter starts
backup power mode.
7. All loads in the backup power circuits are supplied with power. The remaining loads
are not supplied with power and are safely isolated.
Transitioning
from backup
power mode to
feeding energy
into the grid 1. The inverter is operating in backup power mode. The contactors K1 and K2 to the
public grid are open.
2. Public grid available again.
3. The Fronius Smart Meter monitors the grid parameters on the public grid and
passes this information to the inverter.
4. The stability of the returned public grid is determined by checking the measured val-
ues of the Fronius Smart Meter.
5. The inverter ends backup power mode and disconnects the outputs.
6. The inverter deactivates K3. The contactors K1 and K2 are reactivated.
7. All circuits are reconnected to the public grid and are supplied by the grid. The
inverter does not feed anything into the grid at this time.
8. The inverter can start feeding energy into the grid again after performing the grid
checks required by the relevant standard.
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