Sri Lanka lost power across the entire island on Friday after the national grid suffered a total system failure, and the Energy Minister says investigators are examining whether a technical fault reported the previous day at the Upper Kotmale power station set it off.

The National System Operator (NSO) — the post-restructuring grid manager that took over the Ceylon Electricity Board’s control function — said the country was experiencing an islandwide outage “following a system failure caused by instability in the electricity grid this morning,” the Daily Mirror reported.

Energy Minister Anura Karunathilaka said the disruption “resulted in an emergency shutdown of electricity supplies as authorities moved to stabilise the system,” and that supply to several areas had already been restored, the Daily Mirror reported at 1.30 p.m. He told NewsFirst that electricity could return to some areas within roughly an hour, with no confirmed timeline for the rest.

The suspected trigger, and what is actually established

Two different claims are circulating and they are not the same claim.

The NSO’s statement describes the mechanism: instability in the grid produced a system failure. That is an account of how the system went down.

The Minister’s statement concerns a possible trigger. Authorities are examining whether the collapse was linked to “a technical glitch reported yesterday at one of the units at the Upper Kotmale Power Station,” and are checking whether that incident “directly triggered the grid disruption or whether other operational factors had contributed to the imbalance.”

The timing detail is the Daily Mirror’s, and it matters: on that account the fault at Upper Kotmale was known on Thursday, a day before the grid fell over. NewsFirst’s filing reports the suspected unit failure without placing it on the previous day, and Hiru News carries the suspicion without a date. Nothing published so far says what the Thursday glitch was, whether the unit was returned to service, or who knew about it.

Both NewsFirst and the Daily Mirror state plainly that the exact cause remains unconfirmed and under investigation. This desk is recording the Upper Kotmale link as a line of inquiry, not a finding.

Rooftop solar owners asked to disconnect

The NSO asked owners of rooftop solar photovoltaic systems to disconnect them until further notice to support restoration, a request Hiru also carried and which the Minister repeated, saying it would help stabilise the grid and speed the work.

This should not be read as a statement that solar caused the outage, and no official has said it did. Bringing a collapsed grid back up requires controllers to match generation and demand step by step; thousands of inverters feeding in unpredictably at midday makes that harder. The request is a restoration measure.

That said, the instrument is a familiar one, and the archive shows how familiar.

Sri Lanka has been warned about exactly this

On 2 October, Ministry of Energy officials told Parliament’s Sectoral Oversight Committee on Infrastructure and Strategic Development that the technical concerns around the solar build-out were grid stability, frequency control and reverse power flow caused by fluctuating solar generation during periods of low daytime demand — the hours when rooftop output peaks and consumption does not. The mitigations described to that committee were about 400,000 smart meters and battery storage placed at distribution-transformer level in Colombo and Kotte. Neither is in place.

Friday’s collapse happened around midday.

The switch-off request has precedent on both sides of the calendar. On Vesak poya day, 30 May, supply was cut to around 100 areas after what the same minister called an “unexpected system imbalance” during a holiday demand slump, and the NSO asked rooftop solar owners to switch off then too. In April, the CEB ordered rooftop systems above 300 kW off the grid for ten days over Avurudu, citing the same midday-surplus problem.

Against that, the Minister has consistently rejected the suggestion that the government is squeezing solar. On 26 September he called claims of curtailment “entirely baseless”, saying 1,513 MW of rooftop and ground-mounted capacity had been added in two years. On 12 September he assured Parliament that no power cuts were expected, citing reservoirs at 58.7% of capacity and 565 MW of battery storage being fast-tracked before March.

The water supply went with it

The outage has already propagated beyond electricity. Water purification stopped at the Ambatale and Biyagama treatment plants, the Chairman of the National Water Supply and Drainage Board said, attributing the halt to the nationwide power failure, Hiru reported at 1.37 p.m.

Ambatale is the principal source of treated water for the Colombo metropolitan area. No filing yet says how long the plants have been down, when purification will resume, or whether supply interruptions are expected.

How the day unfolded

All times Colombo.

Not reported

No filing gives the number of consumers affected, the time the grid actually went down, or a figure for lost load. None says whether other generating plants — including the Norochcholai coal station — tripped as the system collapsed, which is the ordinary consequence of a grid-wide failure and the usual reason restoration takes hours rather than minutes.

Nothing reports the status of hospitals, Bandaranaike International Airport, the ports, rail signalling or telecommunications. No official has said whether the system has a black-start capability adequate to the event, or given a target time for full restoration.

Nor is there yet any statement from the Public Utilities Commission, or any indication of whether a formal inquiry will be opened into the failure.

This is a developing story and will be updated.