It was the second time for the Sual plant, operated by Mirant Philippines (formerly Southern Energy Philippines) suffered a major technical problem since December 1999 when the plant tripped when numerous jellyfish got stuck in it.
The Sual plants are being operated under a build-operate-transfer scheme with the National Power Corp.
The Sual units were carrying a combined load of 1,100 megawatts when they tripped.
According to Napocor officials, the tripping triggered a "domino effect" causing other power plants in the Luzon grid to trip.
Nearly 1,900 MW was lost in Luzon, representing about 30 percent of the total load of the Luzon grid.
Among the areas affected were certain parts of Quezon City, Makati City, Mandaluyong City, Taytay, Navotas, Taguig and certain portions of Tarlac, Bulacan, Pampanga, Batangas, Laguna and the Bicol region.