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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Instructions when ARC Fault is Detected
In the event of an arc fault, the faulty channel is disconnected and isolated preventing arc flashes.
Local indicators report the status of the GARD. A remote monitoring facility is available via
MODBUS. Follow the suggested actions below;
1. When an arc fault is detected all channels will be disconnected with the GARD status
indicators OFF and the status telemetry reading”ARC Fault Detected”.
2. After an arcing even, the GARD transitions to the “self-test” state and sequenctially cycles
power through individual channels A,B,C & D for 150 seconds each.
a. During the 150 seconds, if an arc is detected, the channel is disconnected and a flag
is raised on the Alencon HMI.
3. Faulted channels will be disconnected with the status indicators glowing RED while
unfaulted channels will be re-energized with indicators glowing green.
4. Alencon HMI will update the status and indicate faulted channels to the user.
5. If servicing is to be completed, press the E-Stop button to disconnect all other channels.
6. Check the input and output wires of the tripped channel to make sure there is no current
flowing.
7. After ensuring that there is no current flowing through the tripped GARD channel,
disconnect the input and the output wires.
8. 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.
9. Disconnected PV strings must be inspected by the authorized maintenance personnel.
10. Once the faulty string(s) are restored they can be reconnected back to the GARD channel.
Principle of Operation
4.4.4.1
Manual Operation
The GARD operates autonomoously. The connected input PV strings power up the GARD. The
GARD automatically performs a self-test of the GFDI and AFD before transitioning to normal
operation i.e. RUN. If no faults are detected, the channel LED’s (A, B, C, D) turn GREEN. If a fault
is detected on one of the channels, the indicator light on this channel turns RED.
The reason for a fault should be investigated and the fault should be repaired. Once a fault is
cleared, the red indicator may be cleared by depressing the RESET pushbutton.
4.4.4.2
Remote Monitoring and Control
The GARD is a very intelligent device. The software controls operating as a State Machine is
described in sections below. The states and statuses are communicated via Modbus RTU as
described in section 6.
