SMA SC 500CP XT - Manual (Page 93)

The insulation monitoring device takes approximately five minutes to detect the correct insulation resistance. The value
of the insulation resistance can be read off from the user interface in the instantaneous value Riso. If the insulation is
intact, the inverter switches back to the operating state "MPP load operation." Once the insulation monitoring process is
complete, the GFDI should be closed again, thus enabling the PV array to revert to grounded operation.
If after approximately five minutes one of the errors 3501 ‒ Insulation Failure, 3504 ‒ Insulation failure ignored
or 3601 ‒ Warning insulation error is displayed, the insulation is defective. In this case, a qualified person will
need to check and, if necessary, repair the insulation and then acknowledge the error.
Type of insulation monitoring device used
The insulation monitoring device used is the A-ISOMETER iso-PV1685 device supplied by Bender GmbH & Co. KG.
10.2.3.6 Remote GFDI and Insulation Monitoring Device
With the order option "Remote GFDI and Insulation Monitoring", it is possible to automatically correct errors which
have occurred, to temporarily disable the grounding connection of the PV array and to check the insulation with the
integrated insulation monitoring device.
Figure 21: Remote GFDI and Insulation Monitoring Device
Position Designation
A Insulation monitoring device
B Remote GFDI
When the Remote GFDI is closed, the PV array is grounded. In this state, the insulation resistance cannot be
determined. If the Remote GFDI trips, initially a temporary error will be assumed and a motor drive will close the
Remote GFDI after a defined waiting time. No external switch command is required to close the tripped Remote GFDI.
The inverter can switch back to feed-in operation after a waiting time.
In the default setting of the inverter, the software will attempt to start the Remote GFDI up to three times per day.
If the Remote GFDI is tripped on several consecutive days, the software assumes a permanent insulation error and the
inverter will no longer switch back on. In this case, a qualified person will need to check and, if necessary, repair the
insulation and then acknowledge the error.
When the Remote GFDI is open, the grounding connection is disabled. In this state, the insulation monitoring device
continuously measures the insulation resistance. In the operating state "MPP load operation", the insulation resistance
of the entire system, from the PV array to the MV transformer, will be measured. If the inverter is in the operating state
"Grid monitoring", only the insulation resistance from the PV array to the inverter will be measured.
10 Function Description SMA Solar Technology AG
User Manual 93 SCCPXT-BA-E4-en-54