SMA SC 500HE-20 - Manual (Page 22)

3 Product Description SMA Solar Technology AG
22 SCxxxHE-20-BE-BEN111210 Operating Manual
Figure 6: Sunny Central String-Monitor Controller
The String-Monitor units measure the string currents via the integrated measuring circuit board and
continuously calculate the average value of the string currents. The measuring circuit board compares
the string currents with the average values. If a string current exceeds or falls short of the specified
threshold for the average value, a warning or fault is generated and displayed via the indicator lights
or the display and on the SC-COM surface.
3.4 Remote shutdown
With the remote shutdown unit, you can set the Sunny Central to switch off or shut down within
6 seconds (e.g. from a control room). The remote shutdown is similar to the stop function of the key
switch.
If the remote shutdown unit is activated from the control room when the Sunny Central is in
"Grid monitoring" operating state, a motor drive automatically shuts off the main DC switch and the
Sunny Central switches to "Stop".
If the remote shutdown unit is activated from the control room when the Sunny Central is in the
"MPP load operation" operating state, the Sunny Central switches to "Shutdown". Once shutdown is
complete, the AC contactor and the DC main switch turn off automatically and the Sunny Central goes
into "Stop" operating state.
3.5 Insulation Monitoring
3.5.1 How Insulation Monitoring Works
Insulation monitoring is a mechanism for ensuring plant protection in electrical devices. There are
different types of insulation monitoring:
• In grounded grids
Insulation monitoring is performed via a residual current monitoring device. If an insulation
failure occurs, the fault currents will be detected and interrupted.
• In ungrounded grids
An insulation monitoring device constantly determines the insulation resistance using an active
measurement procedure. If the insulation resistance falls below the warning threshold specified
in the insulation monitoring device, an insulation warning will given via the indicator lights or on
HE SUNNY CENTRAL
STRING MONITOR CONTROLLER
SUNNY CENTRAL
STRING MONITOR CONTROLLER