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SMA Solar Technology AG
2.2.2 Reverse Current
A reverse current may arise when different open circuit voltages are present at modules mounted in
parallel. In this event, the reverse current can be much higher than the module's short circuit current.
The higher the reverse current, the higher the heat will rise in the modules of the faulty PV strings.
Pronounced warming can destroy the modules of the faulty PV strings.
Figure 3: Possible reverse currents in the PV array
The following points can cause a reverse current:
• Short circuit in one or more modules,
• Short circuit in one or more cells in a module
• Double ground fault in a module
• Double ground fault in the cabling
The Sunny String-Monitor contains string fuses. They trip when the string current is too high and thus
protect the modules of the faulty PV strings. The Sunny String-Monitor informs Sunny Central Control
of the failure of the PV strings. The Sunny Central Control displays the warning "SMU".
Technical Description
2 Safety
SSM-TEN103132
11
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