SMA SC 500HE-20 - Manual (Page 26)

3 Product Description SMA Solar Technology AG
26 SCxxxHE-20-BE-BEN111210 Operating Manual
If an insulation error occurs, the insulation resistance will fall below the ALARM1 threshold. In this case
the operating behavior of the inverter can be set via parameters:
• If the parameter "IsoErrIgn" is set to Off, the measuring circuit generates a fault message and
the inverter switches off when the ALARM1 value falls below a specific threshold. LED1 turns on.
• If the parameter "IsoErrIgn" is set to On, the error message from the measuring circuit is ignored
when the ALARM1 value falls below a specific threshold. The inverter continues to feed power
into the grid and generates the error message "3504 ‒ insulation failure ignored".
Type of insulation monitoring device used
The insulation monitoring device used is the A-ISOMETER iso-PV device supplied by
Bender GmbH & Co. KG.
3.5.6 GFDI and Insulation Monitoring
If "GFDI and Insulation Monitoring" is ordered, you can temporarily disable the grounding connection
of the PV array and check the insulation with the integrated insulation monitoring device.
When the GFDI is closed, the PV field is grounded and the insulation resistance cannot be determined.
If the GFDI is open, the grounding connection is disabled and the insulation monitoring device can
continuously measure the insulation resistance. In the "MPP load operation" operating state, the
insulation resistance of the entire system will be detected, from the PV modules to the medium-voltage
transformer. If the inverter is the "Grid monitoring" operating state, only the insulation resistance from
the PV modules to the inverter will be detected.
Insulation monitoring should be performed in the "MPP load operation" operating state so that all
sections of the PV plant are included in the insulation measurement.
The parameter for insulation monitoring allows you to configure how an error message in the
insulation monitoring device will affect the operating behavior of the Sunny Central:
• If the parameter "IsoErrIgn" is set to Off, the measuring circuit generates a fault message and
the inverter switches off when the ALARM1 value falls below a specific threshold. LED1 turns on.
• If the parameter "IsoErrIgn" is set to On, the error message from the measuring circuit is ignored
when the ALARM1 value falls below a specific threshold. The inverter continues to feed power
into the grid and generates the error message "3504 ‒ insulation failure ignored".
Insulation Monitoring
The insulation monitoring device will start measuring once the GFDI is open. The device will initially
assume that the insulation is poor. If the parameter "IsoErrIgn" is set to Off, the inverter will switch off
temporarily.
Within 5 minutes the insulation monitoring device will determine the correct insulation resistance,
which can be viewed on the device's display. If the insulation is intact, the inverter switches back to
"MPP load operation". The error "3505 ‒ ground fault ignored" appears. This error indicates that the
PV array is operating without a grounding connection. If the insulation monitoring process is complete,
the GFDI should close again and thus allow the PV array to operate with a grounding connection.