3 Product Description
SMA Solar Technology AG
32
SCCP-JP-BA-A4-en-12
User Manual
3.9 Islanding Detection
3.9.1 Active Islanding Detection
The islanding detection function detects the formation of stand-alone grids and disconnects the Sunny Central from the
utility grid.
Islanding can occur when at the time of utility grid failure, the load in the shut-down sub-grid is roughly equivalent to the
current feed-in power of the PV system.
With active islanding detection, the Sunny Central continuously checks the stability of the utility grid by actively attempting
to influence the power frequency.
If the utility grid is intact, this has no impact on the utility grid. The power frequency can only be influenced if a stand-alone
grid has been established. In this case, the frequency change is sufficient to exceed the configured frequency limits and
the Sunny Central disconnects from the utility grid (see Section 7.3 "Setting Power Frequency Monitoring", page 47).
To enable the "Active Islanding Detection" function, contact the SMA Service Line.
3.9.2 Passive Islanding Detection
Depending on the order option, the Sunny Central may be equipped with passive islanding detection. The islanding
detection function detects the formation of stand-alone grids and disconnects the Sunny Central from the utility grid.
Islanding can occur when at the time of utility grid failure, the load in the shut-down sub-grid is roughly equivalent to the
current feed-in power of the PV system.
Unlike active islanding detection, with passive islanding detection the utility grid is not actively influenced, but simply
passively monitored. This involves monitoring the speed of the frequency change. A grid monitoring relay is integrated in
the Sunny Central for this purpose. This relay monitors the utility grid and sends a signal to the Sunny Central under fault
conditions.
If the power frequency changes by a certain amount in a certain time, a stand-alone grid is detected and the
Sunny Central disconnects from the utility grid. The magnitude of the frequency change and the time in which this change
must take place can be configured via parameters on the grid monitoring relay.
The response times for passive islanding detection are generally shorter than for active islanding detection.
3.10 Schematic Diagram
Schematic diagrams in PDF format contain jump marks. By double clicking a jump mark, the display will change to the
corresponding current path or the referenced place in the equipment list.
SMA Solar Technology AG recommends using PDF schematic diagrams for troubleshooting. The schematic diagrams in
PDF format are available on request. Contact the SMA Service Line.
