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Automatic switch to backup power all-pin separa-
tion, Italy
Functions
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Transitioning
1.
from feeding en-
ergy into the grid
2.
to backup power
3.
mode
4.
5.
6.
7.
8.
9.
10. All loads in the backup power circuits are supplied with power. The remaining
50
Measuring and transferring the required parameters for energy management
and Solar.web by the Fronius Smart Meter.
Monitoring of the voltage and frequency grid parameters by the inverter.
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 lim-
its specified by the country-specific standards.
Establishing a correct ground connection for backup power mode.
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 in-
verter. Furthermore, the performance of the connected battery must also be
considered.
The public grid is monitored by the inverter's internal grid and system pro-
tection unit and by an external grid and system protection unit.
Failure of the public grid
The inverter carries out the measures necessary according to the country
standard and then switches off.
The external grid and system protection unit opens contactors K1 and K2 for
grid monitoring. 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 all-pin open. To ensure that the public grid
has definitely been disconnected, the NC auxiliary contacts of contactor K1
give feedback to the external grid and system protection unit.
The NC main contacts of contactors K4 and K5 are closed, establishing a
connection between the neutral conductor and the ground conductor. The
two other NC main contacts of contactors K4 and K5 give feedback to the
inverter that the ground connection has been established correctly.
The inverter activates relay K3, which activates the remote input of the ex-
ternal grid and system protection unit via an NC contact. This prevents a
connection to the public grid when voltage is restored in the grid.
The NO contact of relay K3 gives additional feedback to the inverter on
whether the locking was successfully performed by relay K3.
The inverter decides based on the contactor's feedback as well as the meas-
urement on the inverter terminals and the Smart Meter that the emergency
power mode can be activated.
The inverter starts backup power mode after a defined checking period.
loads are not supplied with power and are safely isolated.
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