Solar Inverter Grid Fault: 7 Safe Checks Before You Call

Your rooftop plant was fine yesterday. Today the inverter screen says grid fault, the units have dropped, and it is a sunny day. A solar inverter grid fault is one of the most common messages on Kerala rooftops, and often the cause is outside your house. This guide gives seven safe checks you can do from the ground, the voltage KSEB must supply, and when to call the installer.

What does a solar inverter grid fault mean?

• A grid fault message usually means the inverter has stopped feeding power because the KSEB supply is missing or outside the range it is set to accept.
• Every grid-connected plant must isolate itself when the grid fails (Regulation 14.4 of the KSERC RE Regulations 2025), so a stop during a power cut is normal.
• KSEB must keep single-phase supply at 240 V within six per cent either way (Regulation 4(8) of the Standards of Performance Regulations).
• If voltage stays outside that band, KSEB has seven days to correct it after your complaint when no network upgrade is needed.
• A PM Surya Ghar vendor must repair the plant free of cost during the 5-year maintenance contract (MNRE guideline clause 7(d)).
• Never open the inverter, junction box or DC isolator yourself; panels stay live in daylight.

Most messages that say grid fault, grid lost, no grid, AC voltage high or AC voltage low mean one thing: the inverter checked the KSEB supply, did not like what it saw, and switched itself off from the grid. That is a safety feature, not a breakdown. The MNRE technical specification for PM Surya Ghar plants says the inverter must turn off quickly when the grid fails, so it does not feed a dead line where a KSEB lineman may be working, and must also disconnect on under and over voltage (MNRE guideline, technical specification 2.11).

This is also why an on-grid plant gives no power during a power cut, even at noon. If you want backup, that needs a battery or hybrid setup; the on-grid vs off-grid vs hybrid guide explains the difference. A grid fault that clears on its own when the supply comes back is the system working as designed.

7 safe checks before you call the installer

Under the KSERC rules, you as the plant owner are responsible for safe operation and for getting defects fixed on your side of the inter-connection point, while KSEB is responsible beyond it, including the meter (Regulation 14.2). In practice that splits a grid fault into two questions: is the problem in the KSEB supply, or in your plant? The checks below help you answer that from the ground, without touching any wiring.

• Check one: look at the house supply. If lights and fans are off, or neighbours have no power too, the grid is down and the inverter will restart by itself after supply returns.
• Check two: read the inverter screen or app and write down the exact message, the date and the time. Take a photo. Do not press reset repeatedly.
• Check three: note when the fault happens. A fault only around midday on sunny days, when your plant exports most, is a reason to ask KSEB to measure the voltage at your meter.
• Check four: look at the solar AC breaker in the distribution board without opening the board cover. If it has tripped, leave it and call the installer rather than switching it on again and again.
• Check five: compare today's units with your normal days. The solar generation per day guide shows how to keep a simple log.
• Check six: from the ground, look for new shade from a tree, water tank or a neighbour's new floor. The solar panel shading guide covers what to do.
• Check seven: look for chewed cables or loose conduit near the inverter from a safe distance. The rodent protection guide explains the warning signs.

What voltage should a Kerala home get from KSEB?

The Kerala Electricity Supply Code fixes low-tension supply at 240 volts between phase and neutral for single-phase homes and 415 volts between phases for three-phase homes (Supply Code Regulation 6). Under Regulation 7, KSEB may let the voltage at your point of supply move up to six per cent above or below that without your written consent.

What six per cent means at your meter (arithmetic from the declared voltage):

On a lightly loaded rural line with many solar homes, the voltage can rise in the middle of the day when everyone exports. Your inverter then sees the supply climb past its limit and disconnects, comes back, and disconnects again. You cannot fix this inside your house. It is a matter for KSEB's network, and it is the same local capacity question that the transformer hosting capacity guide covers for new applications.

How to complain to KSEB about high or low voltage

If your notes show the fault lines up with supply voltage, register a voltage complaint with your KSEB section office. Once KSEB receives a voltage complaint, it must check whether the variation is beyond the permitted limits and bring it back within them in seven days where no network upgrade or new substation is needed. Where the distribution system has to be upgraded, the limit is 120 days (Standards of Performance Regulation 4(8)(C)).

KSEB's website lists the 1912 customer care service and the number 9496001912 for complaints. Give the consumer number, say the plant trips on grid voltage, and share your dated list of fault times. Keep the complaint number.

If KSEB misses the deadline, Schedule I of the same regulations sets compensation of ₹200 for each week of default on voltage fluctuation complaints. Where compensation is not automatic, the application goes through the online portal within thirty days of the breach (Regulation 16). The KSEB compensation guide lists the other standards and how to claim.

A Kerala example: a plant that trips every sunny noon

Illustrative example, not a real case. A single-phase home in Palakkad notes that its inverter shows AC voltage high between about eleven and two on clear days, and the screen reads close to 256 V each time. That is above the 254.4 V ceiling worked out above. The owner registers a voltage complaint on day one. KSEB has seven days if no upgrade is needed. If the voltage is still out of range three weeks after the deadline, the compensation at ₹200 a week would be ₹600 for those three weeks of default (3 × ₹200).

Meanwhile the owner asks the installer to confirm the fault log and inspect the AC cable run from the inverter to the meter, so a problem on the house side is ruled out before KSEB visits. Any change to inverter grid settings is a job for the installer alone, within what KSEB has approved.

When to call the installer, and what it should cost you

Call the installer when the fault continues while the house has normal supply, when the AC breaker trips again, when the screen shows an isolation, earth or insulation fault, or when output stays low after the checks above. For PM Surya Ghar plants, the registered vendor must carry out repairs and maintenance free of cost for 5 years of the Comprehensive Maintenance Contract from commissioning, and replace or repair non-performing or under-performing parts free in that period (MNRE guideline clause 7(d)). The solar panel maintenance guide covers routine care after that.

After a thunderstorm, a fault that will not clear can mean a surge device has operated. That is a job for the installer, not for you; the lightning protection guide explains what is fitted and why.

Checklist: what to do this week if your inverter shows a grid fault

• Confirm whether the house and street have supply.
• Photograph the inverter message and note the date and time every time it appears.
• Compare generation with normal days using your meter; the net meter reading guide shows which display to note.
• Look for new shade and chewed cables from the ground only.
• If faults line up with midday sun, register a voltage complaint with KSEB and keep the number.
• If supply is normal and the fault stays, call your installer and ask for the fault log in writing.
• Book a free bill and transformer check if you are unsure whether the local line is the cause.

Frequently Asked Questions

Official Sources and Accuracy Note

• 01KSERC (Renewable Energy and Related Matters) Regulations, 2025 (gazette PDF)
  Takeaways: Reg 14.4 isolation on supply failure, Reg 14.2 owner responsibility up to the inter-connection point.
  govt source · opened 2026-10-28
• 02KSERC (Standards of Performance of Distribution Licensees) Regulations, 2015, consolidated text (final PDF)
  Takeaways: SoP Reg 4(8)(B)(i) six per cent LT band and 4(8)(C) seven-day voltage complaint timeline.
  govt source · opened 2026-10-28
• 03MNRE Guidelines for PM-Surya Ghar: Muft Bijli Yojana, CFA to Residential Consumers (PDF)
  Takeaways: MNRE clause 7(d) free repairs for the 5-year CMC on PM Surya Ghar plants.
  govt source · opened 2026-10-28
• 04Kerala Electricity Supply Code, 2014, consolidated text updated as on 14-10-2025 (KSERC final PDF)
  b7: Supply Code Reg 6(1)(a) declares LT supply as single phase 240 V and three phase 415 V; Reg 7 proviso allows six per cent variation for LT.
  govt source · opened 2026-10-28
• 05KSEB Ltd official website (home page contact strip)
  b11: kseb.in home page lists the 1912 toll-free customer care service and the 9496001912 IVR number.
  govt source · opened 2026-10-28