Problem diagnosis · Sigenergy

Sigenergy Grid Protection Trip — G98/G99 Voltage & Frequency Fault Diagnosis

Your SigenStor keeps disconnecting from the grid with a protection alarm. It's not the inverter failing — it's protecting the network. Grid overvoltage, frequency excursion, or isolation fault — each has a different cause and fix. This guide walks through how to identify which one you're dealing with.

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G98/G99 voltage and frequency limits
Safety protection, not system failure
SigenCloud event log diagnosis

Frequent grid trips?

We review your SigenCloud event log, check grid code configuration, and determine whether the trips are caused by grid quality, system settings, or an isolation fault.

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Wow... a firmware update to my inverter sent the whole system into meltdown – the battery discharged, and the house seemed to be drawing power, and the solar, who knows where that was going? Aghhh... A short email exchange with Roland and Solar Tech Support sorted the problem... the firmware had reversed a setting (from when it was installed), and the CT clamp needed to be reversed. As soon as I had done that, the world returned to normal. Thanks, Roland; there is no way I would have come to that conclusion. Would I recommend them? You bet! Worth the fee? You bet, again!

Pete Hawkins · Jul 2026 Google

We have a GivEnergy system, both GivEnergy and our installer have gone bust! Ron was able to remotely log in to our system and sort the issue within about 30mins. Would definitely recommend and will be using in future

Chris Robson · Oct 2026 Google

Ron has come to our rescue once again! After sorting out our GivEnergy battery issue, he was on hand to help us find a solution to data logging issues caused during install of an additional inverter. He's helpful, patient and extremely knowledgeable. Utterly brilliant service. Thank you again!

Edward Johnson · Aug 2026 Google

Absolutely wonderful support. I have a GivEnergy system that was installed in 2022, and a firmware update was flagged in the app, so I proceeded to update the software .... and immediately regretted it, as my inverter came up with an error, and was not working at all! With no GivEnergy support available, and my installer saying there was nothing he could do, I googled help, and found Ron. What a stroke of good luck! Submitted an on line enquiry late morning, and received phone call just after 5 pm, and later that evening Ron was able to supply me with old firmware no longer available on the GivEnergy web site. I was then able to update the firmware using a GivEnergy youtube video as reference, and hey presto the system was back up and running. One further slight adjustment by Ron and we are back normal. What a relief. I have no hesitation in recommending Solar Tech Support if you have a problem. Great service! And if you are a GivEnergy system owner, whatever you do, DO NOT UPDATE FIRMWARE!

Neill Ginn · Jul 2026 Google

Ronald was able to organise a brilliant electrician with extensive experience of GivEnergy systems local to me in the SW. I have now got a fully functioning system and suspect that my electricity bill will be substantially reduced or in credit over a year. Also when said electrician discovered an overvoltage in the my local grid, Ronald prepared a very lucid and comprehensive report of the situation which I have now supplied to my local grid. Cannot recommend Ron and Dan enough.

Ian Macmillan · Jul 2026 Google

The Solar Tech Support company was the only one to respond to a request for someone to supply and fit a new inverter for our solar panels after our old one finally expired after 26 years. Ron kept us well informed throughout, came and ascertained that the issue was down to the inverter having failed then sourced and fitted a new one. He got the system up and running again, set up the wi-fi performance feedback and took away the old inverter for disposal. By acting promptly and fitting the job around existing commitments we were able to get our solar power unit back in operation with minimal delay in the short while before we were due to go away for a week. The work was carried out very professionally and we were asked to confirm that all was in order the following day. I was impressed that, having recently taken on additional work for GivEnergy customers we were able to keep our solar panel down-time to a minimum. I would highly recommend for prompt attention and first-rate service.

James Dignan · Aug 2026 Trustpilot

Pete Hawkins · Jul 2026 Google

Neill Ginn · Jul 2026 Google

Ian Macmillan · Jul 2026 Google

James Dignan · Aug 2026 Trustpilot

Written by Ronald · Independent Solar Engineer Last updated 8 November 2026

Important: A grid protection trip is a safety function, not a system failure. Your SigenStor is doing exactly what it should — disconnecting to protect the grid when voltage or frequency exceeds safe limits. The system reconnects automatically when conditions normalise. Understanding the cause helps reduce trip frequency.

Diagnostics

5-step grid protection trip diagnosis

Grid protection trips fall into two categories: grid quality issues (voltage/frequency — external) and isolation faults (DC insulation — internal). The SigenCloud event log tells you which one you're dealing with.

Check SigenCloud event log for the trip details

Log into SigenCloud and navigate to the alarm or event log. Find the grid protection trip and note:

• Fault type — overvoltage, undervoltage, overfrequency, underfrequency, or isolation fault

• AC voltage reading at the time of disconnect

• Grid frequency at the time of disconnect

• Time of day — midday trips suggest solar export pushing voltage up

Grid protection thresholds (G98)

Over voltage: Above 262.2 V for 1 s (stage 1) or 273.7 V for 0.5 s (stage 2) → automatic disconnect

Under voltage: Below 184 V for 2.5 s → automatic disconnect

Over frequency: Above 52Hz for its stated time delay → automatic disconnect

Under frequency: Below 47.5Hz for its stated time delay → automatic disconnect

The fault type determines which diagnostic path to follow. Voltage and frequency trips are grid quality issues. Isolation faults are internal to your system.

Confirm the correct G98 or G99 grid code is configured

In SigenCloud, check the grid code configuration for your SigenStor:

G98: For installations up to 16 A per phase in total (3.68kW single-phase, 11.04kW three-phase). Can connect without prior DNO approval. Standard voltage and frequency protection limits.

G99: For anything larger, even with export limited. Requires formal DNO application and acceptance. Additional requirements for reactive power support and frequency response.

If the wrong grid code is configured — for example, a factory default from another country — the protection limits may be wrong, causing unnecessary trips. Grid code settings typically require installer-level access in SigenCloud.

If you have a G99 system, check your DNO acceptance letter for the specific export and protection settings that were agreed.

Determine if the trip is transient or persistent

After a grid protection trip, observe the reconnection behaviour:

Transient (reconnects in 5–10 min)

A brief grid voltage spike or frequency excursion. Common in areas with high solar density at midday. The system recovers automatically. Accept as normal grid behaviour or consider export limiting to reduce frequency.

Persistent (stays disconnected 30+ min)

Grid voltage or frequency remains outside limits for an extended period. This is a local grid infrastructure issue. Export limiting may help, but the DNO should be notified if it happens regularly.

Monitor over 3–5 sunny days to establish a pattern. Note the time, voltage, and whether the system reconnects automatically.

Check for isolation faults on the DC side

If the grid protection alarm includes an isolation fault code, the issue is on the DC side of the system — not the AC grid. An isolation fault means the insulation resistance between DC circuits and earth has fallen below the safety threshold:

• MC4 connector water ingress — moisture inside panel connectors reduces insulation resistance

• Damaged DC cable insulation — UV degradation, rodent damage, or mechanical abrasion

• Battery module fault — internal insulation breakdown within a module (see battery module fault guide)

• Junction box fault — cracked or water-damaged panel junction boxes

Isolation faults require on-site testing with an insulation resistance (IR) meter to locate the affected circuit. Do not attempt to inspect DC wiring yourself — solar panels produce voltage whenever light hits them.

Contact your DNO if grid overvoltage is persistent

If SigenCloud consistently shows AC voltage above 250V at the time of grid protection trips, the problem is grid infrastructure — not your SigenStor:

1. Gather evidence: Screenshot SigenCloud event logs showing voltage readings at each disconnect. Note the pattern — time of day, frequency of trips, and whether it correlates with sunny weather.

2. Contact your DNO: Report persistent high grid voltage. Provide the evidence from SigenCloud. Your DNO is responsible for maintaining voltage within statutory limits.

3. Consider export limiting: While waiting for DNO action, setting an export limit in SigenCloud can reduce peak export power and lower the voltage rise your system contributes.

DNO response times vary. Keep a log of trip events to strengthen your case if the issue persists.

Why grid protection trips happen — and why they're increasing

Grid protection trips are a designed safety function required by UK grid codes. Every grid-connected inverter — regardless of brand — must disconnect when AC voltage or frequency exceeds statutory limits. The SigenStor is not failing when it trips; it is doing exactly what the regulations require. The issue is that the grid infrastructure in many UK residential areas was not designed for the level of distributed solar generation now connected to it.

As solar installations increase — particularly in suburban streets where multiple homes have panels — the cumulative export during peak solar hours pushes local grid voltage above 253V, the ceiling the network has to stay within. This is a voltage rise problem caused by the grid cable resistance and the current flowing back towards the transformer. Every kilowatt exported adds to the voltage rise. When enough systems export simultaneously, the voltage climbs past the inverters' protection limits and all inverters on that circuit disconnect.

Sigenergy SigenStor systems with battery storage have a potential advantage here: excess solar can be stored in the battery rather than exported. If your system is configured for self-consumption priority, it will charge the battery during peak solar periods rather than exporting to the grid — reducing your contribution to local voltage rise. STS can review your SigenCloud settings and recommend a configuration that minimises grid trips while maximising self-consumption and battery utilisation.

Grid protection trip — common questions

Why does my Sigenergy SigenStor keep disconnecting from the grid?

The SigenStor disconnects when grid voltage passes its G98/G99 protection limits: above 262.2V for 1 second or 273.7V for 0.5 seconds, or below 184V for 2.5 seconds. In areas with many solar installations, midday export pushes local voltage above the over-voltage limit. This is a grid quality issue, not an inverter fault, and the system reconnects automatically. Export limiting or battery self-consumption mode can reduce trip frequency.

What is the difference between G98 and G99 on a Sigenergy system?

G98 applies to installations up to 16 A per phase in total (3.68kW single-phase, 11.04kW three-phase), with no prior DNO approval needed. G99 applies to anything larger, even with export limited, and requires formal application. The grid code setting determines voltage and frequency protection limits. Wrong configuration causes unnecessary trips. Check your SigenCloud settings or DNO acceptance letter.

How do I check what caused a grid protection trip on my Sigenergy system?

Log into SigenCloud and check the alarm or event log. Grid protection trips show the specific fault type — overvoltage, undervoltage, overfrequency, underfrequency, or isolation fault — along with the voltage and frequency at disconnect. This tells you whether it was a grid quality issue or an internal system fault.

Can a grid protection trip damage my Sigenergy system?

No. Grid protection trips are a designed safety function. The SigenStor disconnects to protect both the system and the grid — no damage occurs. Frequent trips reduce your generation during disconnect periods but do not cause wear or degradation to the inverter or battery.

What causes an isolation fault on a Sigenergy SigenStor system?

An isolation fault means the insulation between DC circuits and earth has fallen below the safety threshold. Common causes include water ingress into MC4 connectors, UV-damaged cable insulation, or a fault within a battery module. Unlike grid voltage trips, isolation faults require on-site testing with an insulation resistance meter. Book a diagnostic and we'll confirm the cause.

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SigenStor keeps tripping off the grid?

We review your SigenCloud event log, check grid code configuration, and determine whether the trips are caused by grid voltage, frequency, or an isolation fault. Clear diagnosis, clear next steps.

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Grid code and export limit review
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