Solar inverter shutting down or derating on grid overvoltage
The inverter runs, then backs off or disconnects through the middle of the day with overvoltage events in its log. Generation (and the feed-in credit) suffers — worst on bright days when everyone's exporting.
Safety first
This is live measurement work at the switchboard and inverter AC terminals — licensed work with rated gear and due care. Inverter grid-protection settings exist to protect the network: never widen them beyond what the DNSP and the applicable standard allow just to stop the tripping.
Isolate, lock out / tag out, and prove dead before working unless a live test is specifically required, authorised, and carried out under proper supervision. Always follow local regulations, your site procedures, and the equipment manufacturer's documentation.
Apprentice mode
Full walk-through — the why, what readings mean, mistakes & safety.
Likely causes
Ranked from most to least likely.
- 1
Voltage rise across the inverter's own AC run
Most likelyAt full export, the volt drop equation runs in reverse: the inverter end sits HIGHER than the board. A long or undersized run from inverter to switchboard adds rise on top of an already-high grid, tipping the inverter over its limit.
- 2
The grid itself sitting high
#2End-of-line or lightly loaded networks with lots of local solar routinely sit near the top of the tolerance band in the middle of the day — before your customer's export adds to it.
- 3
Wrong grid-settings profile in the inverter
#3A unit commissioned on the wrong region/profile, or with legacy settings, may trip earlier (or later!) than the current requirements — verify against what the DNSP mandates.
- 4
Loose or high-resistance AC connection
Least likelyA poor termination anywhere in the inverter's AC path adds impedance, so the same export current creates extra local rise — and heat at the joint.
Reports are saved on this device to reflect what you actually find.
Testing sequence
Work through one test at a time. Expected reading and what each result means.
On the tools? Job Mode shows one test at a time with thumb-sized buttons — your place and readings carry straight over.
Enter Job ModePull the inverter's event log (display or app) and note the recorded voltages and times of the overvoltage events.
A pattern: events cluster around peak export/light-load hours with voltages at or above the inverter's disconnect setting.
Real voltage data in hand — now find out where the voltage is being made.
If the log shows trips at sane voltages, the settings profile is the suspect — verify it against the current requirements.
View all expected readings at once
Fault-finding flowchart
The same logic as a decision tree.
- 1start
Inverter trips/derates on overvoltage
→ step 2 - 2decision
At full export, is there a big voltage difference between inverter terminals and the board?
Yes→ step 3No→ step 4 - 3result
Voltage rise in the inverter's AC run — fix terminations or upsize the run.
- 4decision
Is the board voltage itself sitting near/above the top of the band through the day?
Yes→ step 5No→ step 6 - 5result
Network voltage problem — log it and report formally to the distributor.
- 6result
Verify the grid-settings profile via accredited commissioning — don't hand-widen limits.
Common mistakes apprentices make
- Widening the inverter's voltage window to stop the trips — it masks a real network problem and can breach the connection agreement.
- Measuring voltage at the board only, and missing the rise across the inverter run entirely.
- Blaming the inverter when the log clearly shows the grid sitting high before the system even wakes up.
- Forgetting that adding export capacity (bigger system) makes existing rise worse.
When to stop & escalate
Sustained high network voltage is the distributor's problem — report it formally with logged measurements (they are obliged to investigate supply outside the allowed range). Settings changes go through accredited commissioning against the DNSP's requirements, not guesswork. Persistent derating that's genuinely rise-in-run is a rewire/upsize quote, not a settings tweak.
If you're past your competence, authorisation, or the safe limits of the job — stop and hand it on. There's no fault worth getting hurt over.
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Related faults
Solar inverter dead, blank, or showing a fault
The rooftop solar has stopped generating — the inverter display is blank, or it's alive but sitting on a fault code. The owner usually notices when the power bill jumps.
Solar inverter showing an isolation / earth fault (often after rain)
The inverter refuses to start (or shuts down) on an isolation, ISO, ground-fault or Riso error — classically first thing on a dewy morning or after rain, sometimes clearing as the day dries out. Something on the DC side is leaking to earth.
Lost or high-resistance neutral
Strange symptoms across a circuit or installation — voltages going high and low on different loads, flickering, equipment damage — pointing to a lost or high-resistance neutral.