MANILA, Philippines - The National Grid Corp. of the Phils. (NGCP) attributes Friday afternoon's one-hour rotating brownouts, scheduled between 1 pm - 3 pm, to technical problems in the Ilijan power plant and the Sual power plant.

In a phone interview, NGCP Sr. Adviser Engr. Jesusito Sulit said that an Ilijan power plant's auxillary motor for its circulating water pump tripped, forcing the power plant to lower energy output from 600 megawatts to 330 megawatts for the day.

"Kaninang tanghali nag-trip yung part ng Ilijan, kaya from 600 megawatts, mga 320 plus na lang siya. Kulang-kulang 300 megawatts nawala," he said.

He added this came in tandem with the Sual power plant's lowering of its output from 647 MW to 580 MW for the day. He was unable to explain the exact details behind the Sual problem.

But Sulit said the problems with both plants are already being addressed, and that power supply would normalize within the day.

Affected areas of the brownout include portions of Bulacan, Batangas, Cavite and Metro Manila.