SMA
Technologie AG
Description of the Sunny String Monitor Cabinet
Technical Description
SSM-TEN072310
Page 5
2 Description of the Sunny String Monitor Cabinet
The Sunny String Monitor Cabinet (SSM-C) enables connection of several strings in
parallel. If failures occur in individual modules, or in the string cabling, they can only
be detected with great effort, or not at all. The SSM-C reliably detects failures, and thus
prevents power losses and yield losses.
In addition, the SSM-C enables monitoring of the internal overvoltage protectors. They
are integrated into each SSM-C in order to protect the inverter from transient
overvoltages. The upstream string fuses allow defective strings, e.g. with a short circuit
in a module or the cabling, to be isolated from the entire PV array. If a string fuse is
triggered, this is detected by the software, and a warning is generated in the Sunny
Central Control (SCC), which is situated within the Sunny Central (SC). In addition, the
individual string currents are analyzed and displayed in the SCC.
For maintenance work and the connection of string lines, there are isolation terminals
in the SSM-C, which enable load-free disconnection of the individual connected strings,
or all connected strings, from the PV generator. An optional load-disconnecting switch
is available, which realizes disconnection from the inverter. See the block circuit
diagram of the SSM-C below.
Data transfer to the SCC occurs via an RS485 bus. The +55 V supply comes from the
Sunny Central.
Overvoltage
protection
RS485 +55 V
Sunny String Monitor Cabinet
String
current monitoring
Sunny Central
Sunny
Central
Control via
hub
Load
disconnector
