Current flowing backwards through one or more PV strings — mismatch in string configuration or shading causing reverse current.
Common causes
Affected string has fewer PV modules than other stringsPV module heavily shaded causing reverse biasModule open-circuit voltage abnormalIncorrect panel orientation on affected string
What to check
STEP 1
Identify affected string. Check if module count is lower than other strings on same MPPT. If so: wait for current <0.5 A, disconnect DC switch, rebalance string configuration.
STEP 2
Check for shading on string — remove obstruction if possible. Measure each string's Voc with DC switch disconnected. Confirm all modules face correct orientation.
Escalate if
String configuration and shading confirmed correct but alarm persists — contact Sungrow support
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