ECONOMYNEXT – Sri Lanka’s island-wide blackout on Saturday, October 17, occurred after a coal power unit tripped during maintenance, exposing an electricity grid destabilized by nearly 1,700 megawatts of unmonitored renewable energy, Energy Minister Aruna Karunathilaka told parliament.
The government has launched an official inquiry through the Ministry Secretary to determine why risky maintenance was scheduled when electricity demand was low and renewable generation peaked.
“We have already questioned the relevant officials regarding why such risky maintenance was undertaken on a day when system demand was at a minimum, the sun was shining brightly, and large amounts of renewable energy were feeding into the grid,” Karunathilaka said.
Before the 11:43 am outage, the National System Operator managed 1,137 MW from controlled sources—516 MW of coal and 621 MW of hydro—alongside roughly 1,700 MW of unmonitored, predominantly solar power.
During maintenance on Unit 1 at the Norochcholai coal plant, a boiler diaphragm dislodged and ruptured, forcing the unit to trip for safety. The sudden loss caused system frequency to drop rapidly, triggering unmonitored renewables to trip offline faster than conventional plants could compensate and collapsing grid equilibrium.
“We can understand a single unit tripping. But how a failure in a single unit escalates into a collapse of the entire system is something we must thoroughly scrutinize,” Karunathilaka said, noting that under grid regulations, a single unit trip should never cause a national network to collapse.
Restoration began at 12:37 pm via the Kotmale plant, though out-of-sequence reconnections by external plants slowed progress. The high-voltage transmission grid was restored by 4:58 pm, and power was fully returned to all consumers by 9:56 pm, with priority given to hospitals, water treatment plants, and airports. Karunathilaka clarified that the Kotmale station had no connection to the initial failure.
During parliamentary debate, opposition lawmaker Ravi Karunanayake questioned why grid spinning reserves failed to prevent the blackout. Karunanayake argued that with total generation at 2,870 MW, a standard spinning reserve of 10 to 15 percent should provide a buffer of 280 to 425 MW, which ought to have easily absorbed a 175 MW drop from the coal unit.
A spinning reserve is unused electricity generating capacity that is already online, synchronized to the power grid, and capable of ramping up within seconds to minutes if an unexpected power loss occurs.
Karunanayake also alleged the boiler failure stemmed from burning substandard coal linked to a past coal procurement scam. He claimed the wider fallout resulted in an accumulated 56-billion-rupee economic loss, comprising 16 billion rupees in direct plant damages, 15 billion rupees in government subsidies, and 25 billion rupees in excess costs incurred from burning expensive emergency diesel.
Karunathilaka rejected both the substandard coal allegations and the loss estimate.
“The issue regarding coal quality occurred during the previous season. By September 4, almost all of that coal had been completely exhausted, and after September 4, what we have been using is new coal,” Karunathilaka said.
He explained that Unit 1 was completely overhauled and resumed operations on September 29 using only fresh coal.
Responding to the reserve issue, Karunathilaka stated that capacity at the Victoria hydro station functioned as the spinning reserve. However, the grid was vulnerable because roughly 2,000 MW of installed rooftop solar inverters were not configured to ride through frequency drops down to 47.5 Hz, causing them to trip offline. Recommendations from an EPRI study on grid inertia and spinning reserve criteria are now being implemented, he added. (Colombo/Oct20/2026)
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