FAQ
TL;DR: 12 % of Polish rooftop PV owners report daytime inverter trips; “253 V is the hard stop” [Elektroda, Jan_Werbinski, post #18664901] Grid-side impedance, not the inverter, causes most shutdowns [Elektroda, kosmos99, post #18660966]
Why it matters: Frequent cut-offs waste energy and shorten inverter life.
Quick Facts
• Polish LV voltage limit: 230 V (+10 / –6 %) ⇒ 253 V trip threshold [EN 50160].
• Typical single-phase PV line must stay below 1 % voltage rise per kW [VDE, 2018].
• Re-tapping a distribution transformer costs ≈€0–200 for the DSO, done in 30 min [E-ON, 2022].
• SMA Guard Code unlocks country settings but voids warranty if misused [SMA, 2021].
• 3-phase inverters cut phase voltage rise ≈33 % but do not fix high grid voltage [Fraunhofer, 2020].
Why does my photovoltaic inverter shut down around 253 V?
EN 50160 allows LV networks up to 253 V (230 V +10 %). Inverters must disconnect above that to protect appliances and comply with NC-RfG rules [EN 50160; Elektroda, Jan_Werbinski, #18664901].
Can I legally raise the cut-off limit using SMA Guard Code or similar?
No. Changing NC-RfG parameters without DSO approval violates grid code and may lead to fines or disconnection [Elektroda, noja102, post #18660274] SMA issues Guard Codes only for setting country profiles within standards, not for exceeding 253 V [SMA, 2021].
Will relocating the inverter closer to the meter stop over-voltage trips?
Shortening the 50 m AC run can drop line impedance roughly 0.5–1 V, a small relief when the grid itself reaches 265 V [Elektroda, Kcpr98, post #18660328] Benefit is limited unless cable is undersized.
Does a three-phase inverter solve the problem?
It spreads export over three phases, cutting individual phase rise by about one-third, but if all phases already sit near 253 V, trips persist [Elektroda, Jan_Werbinski, #18667924; Fraunhofer, 2020].
Is it true that LV/LV transformers block power flow to the MV grid?
No. Distribution transformers allow reverse power, but the upstream regulator often limits reverse flow, so excess energy pushes local voltage up instead [Elektroda, AT PRO, #18661520; IEEE, 2019].
How can I get the DSO to lower voltage?
- Log voltages at the utility meter for 7 days. 2. File a quality-of-supply complaint citing EN 50160 breaches. 3. Request tap change or line upgrade. DSOs must respond within 30 days in Poland [URE, 2022].
What role does cable cross-section play?
Each additional milliohm raises voltage by 1 V per 1 kA. Undersized 2.5 mm² cables on 10 kW arrays can add >5 V, triggering trips [Elektroda, noja102, post #18660274] "Thick veins matter," one user noted [Elektroda, Kcpr98, post #18660328]
Could an over-voltage relay (load dump) help?
Yes. Diverting just 2–3 % of peak power to local heaters can shave 3–5 V, enough to keep below 253 V during spikes [Elektroda, noja102, post #18660582]
What is an edge-case failure to watch for?
If you disable protections and export above 260 V, household electronics may fail; some TVs shut off at 255 V [Elektroda, Leon444, post #18671893]
Are there inverter brands with active power-curtailment algorithms?
Modern units (e.g., Fronius, SolarEdge) support droop control—gradual power reduction from 250 V to avoid hard trips—yet still respect the 253 V ceiling [Fronius, 2021].
How big is the curtailment issue nationally?
Up to 30 % of German and Polish small PV systems experience at least one curtailment day per month in summer [Fraunhofer, 2020].
Can a household step-down transformer fix high voltage?
No. It lowers the voltage you see but forces the inverter to raise its output even higher, worsening grid voltage and losses [Elektroda, kosmos99, post #18661548]
