Sungrow
SG-004 · ID 9
Grid Underfrequency
AC grid frequency has fallen below lower frequency protection threshold. Auto-reconnects when frequency normalises. Displayed fault ID: 009.
Common causes
Grid frequency genuinely below thresholdFrequency protection set too high
What to check
STEP 1
Wait — inverter auto-reconnects. If recurring, measure actual grid frequency.
STEP 2
If below set range, contact DNO/DNSP. Review protection parameters.
Escalate if
Fault persists after parameter review — contact Sungrow support
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