GARD – Installation, Operation and Maintenance Manual
A l e n c o n S y s t e m s L L C - P a g e
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4.4 GARD Functionality and Operation
Functionality
The SPOT or any upstream equipment is connected to the PV System via the GARD. The
communication with GFDI/AFD is carried out via MODBUS.
The GFDI provide ground and arc fault protection features to the existing SPOTs. The GARD
generates its own control voltages. A microcontroller monitors the currents and voltages in all four
PV channels and controls and monitors the AFD module. Self-tests on the GFDI and AFD are
performed automatically every day.
In the event of a fault, the faulty channel is disconnected preventing ground leakages and arc
flashes on the commensurate input PV wires. Local indicators report the status of the GARD. A
remote monitoring facility is available via MODBUS. The operator can enforce the disconnection
manually by using an external switch (E-STOP) or remotely by sending MODBUS commands.
After the system is safely shutdown and the fault cleared, the GARD can be manually reset using
the reset push button available locally on the GARD or via a Modbus Reset command.
Instructions when Ground Fault is Detected
In the event of a ground fault, the faulty channel is disconnected preventing ground currents from
flowing. Local indicators report the status of the GARD. A remote monitoring facility is available
via MODBUS. Follow the suggested actions below;
1. When a ground fault is indicated the corresponding channel will trip and indicate a ground
fault. The ground current will be interrupted by the GARD. When the unit is tripped the LED
for the tripped channel on the GARD will turn RED. The status of the GARD can be
monitored on the HUB user interface. Refer to the HUB manual for more information.
2. When a ground fault is indicated normally grounded conductors may be ungrounded and
energized or normally ungrounded conductors may be grounded.
3. The ground fault will be on the channel that tripped due to ground fault.
4. Press E-Stop button to disconnect all other channels.
5. Check the input and output wires of the tripped channel to make sure there is no current
flowing.
6. After ensuring that there is no current flowing through the tripped GARD channel,
disconnect the input and the output wires.
7. Once the tripped channel is safely disconnected, reset the GARD by disengaging the E-
STOP button and pushing the Reset switch. The GARD can also be reset using the HUB
user interface.
8. Disconnected PV strings must be inspected by the authorized maintenance personnel.
9. Once the faulty string(s) are restored they can be reconnected back to the GARD channel.
