Engineers of the Power Development Board (PDB) were working to restore generation in the three units when this report was filed at 8:00pm last night.

The two 210-megawatt (MW) capacity units at Raozan power plant and the lone 50 MW functional unit out of five at Kaptai hydroelectric project tripped at about 10:00am due to mechanical faults, PDB sources said.

The sudden collapse in power generation and supply in the port city came as a blow to trade and industry as well as to thousands of students preparing for the Higher Secondary Certificate (HSC) examinations starting today.

PDB Chief Engineer, Chittagong region, Kabindra Nath Sen said engineers were trying to detect and repair the faults. "Hopefully Raozan unit-1 and the Kaptai unit will resume generation by 11:00pm," he told The Daily Star in the evening.

He said the city was receiving only 180 MW power from the national grid which was being supplied at very low-voltage to some key areas, such as the export processing zone and Chittagong Medical College and Hospital, to meet emergency needs.

Another PDB official, however, said the plants collapsed due to a sudden fall in voltage in the national grid line. "The line is too old to bear a load more than 140 MW during peak hours, although its normal capacity is around 200 MW," he said.

The official said it may take at least two days to restore full-fledged generation because Raozan unit-2, if tripped, normally needs 72 hours to get back into operation.

Power generation and supply in Chittagong have become a growing concern over the years because of frequent shutdowns of different power plants in the region.

A total of 630 MW power is generated by the plants in Chittagong when all the generation units at Raozan, Kaptai and Shikalbaha are in full operation.

Power generation at Shikalbaha plant remained suspended for the last six days while four units at Kaptai have been inoperative for months together. The total generation at Raozan and Kaptai was 410 mw when the plants collapsed yesterday morning.