SMA SC 500HE-20 - Manual (Page 23)

SMA Solar Technology AG 3 Product Description
Operating Manual SCxxxHE-20-BE-BEN111210 23
the display. This allows measures to be taken to prevent errors (e.g. injury risk due to leakage
current or plant failure). If the insulation resistance falls below the specified warning threshold,
then the plant can switch itself off. The "IsoErrIgn" parameter can be used to configure the
shutdown process when an error occurs.
3.5.2 GFDI
Depending on the order, ground fault monitoring in the Sunny Central is carried out via ground fault
detection interruption (GFDI). This process is used to ground one pole of the PV array.
GFDI is performed via a high-performance k-type miniature circuit breaker with adjustable operating
current. It is integrated in the inverter and connected between an input busbar and the protective
conductor bar.
Figure 7: GFDI in the Sunny Central
Ground fault on ungrounded pole
If a ground fault occurs at the PV array pole that is not grounded, a fault current will flow to the
grounded pole through the GFDI thus triggering it. The fault current is interrupted as a result and the
PV array is not grounded via the ground fault.
If the GFDI is tripped, the insulation monitoring device switches off the inverter so that the insulation
error can be corrected.
Ground fault on grounded pole
The GFDI is bypassed when a ground fault occurs in the grounded pole of the PV array. The ground
fault on the grounded pole cannot be reliably detected. A ground fault that occurs unnoticed on the
grounded pole poses a safety risk. An additional ground fault on the non-grounded pole leads to
higher fault currents that cannot be interrupted by the GFDI. We therefore recommend using an
additional insulation monitoring device in grounded systems. This will allow the insulation to be
checked at regular intervals.
3.5.3 Remote GFDI
Depending on the order, ground fault monitoring in the Sunny Central is carried out via ground fault
detection interruption with motor drive, abbreviated remote GFDI. This process is used to ground one
pole of the PV array. Remote GFDI also enables automatic error processing. This prevents downtimes
and service calls due to temporary insulation errors such as condensation on the PV modules.
on on o off off
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