Power was restored in some areas late Sunday, but brief outages continued to hit several areas yesterday.
"This was a technical failure — a freak accident," said Josephine Mangila, spokeswoman for the National Power Corp. (Napocor).
However, Napocor officials said they were still investigating the cause of the blackout and would move to prevent a recurrence.
President Arroyo ordered Napocor officials yesterday to draft a detailed engineering plan to prevent the Sual power plant in Pangasinan from tripping again.
Presidential Spokesman Rigoberto Tiglao told reporters Mrs. Arroyo issued the instructions from Brunei, where she is attending the leaders’ summit of the Association of Southeast Asian Nations (ASEAN).
"The President’s instructions were for the (Napocor) to draw up this detailed plan to prevent a repetition of the Sual tripping because this was the second time it happened," Tiglao said.
On Dec. 10, 1999, more than half of the nation’s power supply was knocked out when an estimated 50 tons of jellyfish suddenly swam into the cooling system of the 1,000-megawatt Sual plant.
But Phil Vaughan, station manager of Sual, told Pangasinan provincial administrator Virgilio Solis that Sunday’s tripping was caused neither by jellyfish nor sabotage.
Pangasinan was plunged into a two-hour power failure at 10:02 a.m. yesterday after a frequency disturbance affected the load capacity of Unit 2 in Sual.
Defense Secretary Angelo Reyes said the blackout was due to a "normal, technical tripping" at Sual which had a "cascading effect" on other power plants in Luzon.
Reyes said there was no reason to panic and that the energy department was activating hydroelectric plants to take the place of the downed power stations.
But Napocor said it was checking whether there had been sabotage or other forms of damage to its overhead transmissions that spanned thousands of kilometers.
Mangila said Napocor has not found any damage to its major transmission lines and was now in the process of inspecting secondary lines.
"We’re looking at a technical failure of major power facilities not only owned by Napocor but also independent power producers," she said. "We have not received any report (of any damage). We feel confident in saying there’s no major problem in transmission lines."
Mangila said Napocor was coordinating with local officials as well as with police and military units to help guard the transmission lines.
The Department of Energy plans to review the contracts of independent power producers (IPPs) to determine if they have any liabilities or were proven to be the cause of Sunday’s Luzon-wide blackout.
At 4:45 p.m. Sunday, the Sual plant experienced technical problems, which caused it to shut down. Seconds later, the Calaca power plant’s unit 2 in Batangas also tripped.
With a combined generation of 300 megawatts, the twin shutdowns caused brownouts in portions of Luzon. The outage was traced to a sequence of tripping starting with the Pagbilao plant in Quezon.
This series of events took out 500 megawatts from the system. Quezon Power Ltd., an IPP of Meralco, also tripped, followed by the Sual Unit 2 and Makban geothermal plant.
As a result, the Leyte-Luzon high voltage direct current transmission system, which transports power from the geothermal plant in Leyte to the Luzon grid, automatically disengaged from the system as a protective measure.
Senators Rodolfo Biazon and Gregorio Honasan called yesterday for a review of the government’s energy program to avoid any recurrence of Sunday’s massive blackout that paralyzed the whole of Luzon.
Biazon said: "It is about time that the government conduct a comprehensive and accurate study which will determine the cause of the failure of our major generating plants."
Honasan said: "We cannot call the jellyfish for investigation to find out the cause of this problem and so our authorities must be the ones to do something about this." – Marichu Villanueva, Eva de Leon, Ted Torres, Aurea Calica