NTPC restores 6 of 7 units at Korba plant after Sept 4 outage

New Delhi: NTPC Limited has restored generation at six of the seven units of its 2,600 MW Korba power station in Chhattisgarh, about two days after an electrical fault tripped the plant on September 4, an official statement said. The six units account for 2,100 MW of the station's installed capacity. The seventh, the 500 MW Unit-6, has been out of service on a planned overhaul since well before the fault.

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The last two units returned to the grid on September 6. The 200 MW Unit-2 came back at 8:40 pm and the 500 MW Unit-7 at 9:20 pm, the project's public relations officer Ushma Ghosh said.

The restoration sequence

Two 500 MW units, Unit-4 and Unit-5, and the 200 MW Unit-1 were restored within 12 hours of the outage. The 200 MW Unit-3 followed within 36 hours. Unit-2 and Unit-7 completed the sequence on September 6 night.

In a statement on September 5, Ghosh had said three units — two of 500 MW and one of 200 MW — had been revived at 6 pm that day. "Restoration of the remaining three generating units is currently underway in a sequential manner, in accordance with established safety and operational procedures," she said. She added that the cause of the blackout was under investigation.

Seventh unit due back by month-end

The 500 MW Unit-6 has been under shutdown for a biennial planned overhaul since August 25. Ghosh said the unit will be brought to the grid by the end of this month. Until it returns, 500 MW of the station's capacity stays out of service on a planned basis.

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The outage

The units at the coal-based station in Korba city's Darri area tripped shortly after 6 pm on September 4. NTPC attributed the simultaneous tripping to a fault during the testing of a breaker on a Power Grid Corporation of India Limited (PGCIL) bay. "Due to an electrical fault during testing of the breaker of the PGCIL bay being carried out by PGCIL, all the units of Korba have tripped," Ghosh said at the time. An NTPC official described the result inside the generating station as a "blackout-like situation."

The company said then that the units would be brought back in phases, since they cannot be restarted simultaneously after a total shutdown.

The Korba station comprises four units of 500 MW each and three units of 200 MW each, adding up to an installed capacity of about 2,600 MW. It supplies power to several beneficiary states through the interconnected grid.

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