SMA SC 500CP XT - Manual (Page 92)

• If the parameter IsoErrIgn is set to On, the error message from the measuring circuit is ignored when the
insulation resistance falls below the error threshold. The inverter continues to feed into the grid and generates the
error message 3504 ‒ Insulation failure ignored.
• If the parameter IsoErrIgn is set to Run and the insulation resistance falls below the error threshold, the error
message from the measuring circuit will only be ignored if the inverter is in feed-in operation. In feed-in operation,
the inverter continues to feed into the grid and generates the error message 3504 ‒ Insulation failure ignored.
If the insulation resistance falls below the error threshold in another operating state, the error is not ignored and
the inverter does not switch to feed-in operation. The error message 3501 ‒ Insulation Failure appears on the
touch display. The LEDs ALARM1 and ALARM2 are glowing.
Type of insulation monitoring device used
The insulation monitoring device used is the A-ISOMETER iso-PV1685 device supplied by Bender GmbH & Co. KG.
10.2.3.5 GFDI and Insulation Monitoring Device
With the order option "GFDI and Insulation Monitoring", it is possible to temporarily disable the PV array grounding
and to check the insulation via the integrated insulation monitoring device.
Figure 20: GFDI and insulation monitoring
Position Designation
A Insulation monitoring device
B GFDI
When the GFDI is closed, the PV array is grounded. In this state, the insulation resistance cannot be determined.
When the GFDI is open, grounding 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.
Insulation monitoring should be performed in the operating state "MPP load operation". This will ensure that all parts of
the system are included in the insulation measurement.
Insulation monitoring
The insulation monitoring device will start measuring once the GFDI is open. The insulation monitoring device will
initially assume that the insulation is poor. If the parameter IsoErrIgn is set to Off, the inverter will switch off
temporarily.
10 Function Description SMA Solar Technology AG
User Manual SCCPXT-BA-E4-en-54 92