More than 200,000 customers across parts of the Manila Electric Co. (Meralco) franchise alone in Luzon experienced rotating power interruptions on Wednesday after the National Grid Corporation of the Philippines (NGCP) placed the Luzon Grid under Red Alert status due to major power plant outages and transmission line failures.

Meralco began implementing emergency manual load dropping, or rotating brownouts, at 3:23 p.m. 

The interruptions, which lasted an average of three hours, affected customers in parts of Batangas, Bulacan, Cavite, Laguna, Metro Manila, and Rizal.

NGCP placed the Luzon Grid under Red Alert from 3:00 p.m. to 8:00 p.m., with Yellow Alerts raised from 2:00 p.m. to 3:00 p.m. and again from 8:00 p.m. to 10:00 p.m.

The grid operator said peak demand reached 12,537 megawatts (MW), exceeding the available capacity of 12,447 MW, while 4,681.6 MW remained unavailable to the grid.

The Department of Energy (DOE) said the supply shortage was triggered by the tripping of the 500-kilovolt Tayabas-Ilijan and Dasmariñas-Ilijan transmission lines early Tuesday morning. 

The incident disconnected the 1,200-MW Ilijan power plant and EERI Units 1, 2, and 3, which supply 1,262.1 MW to the grid.

Masinloc Unit 3, a 325-MW plant, also went on forced outage later in the morning, worsening the supply deficit.

Energy Secretary Sharon Garin directed NGCP to resolve the transmission issues and ordered San Miguel Power Group to immediately restore Masinloc Unit 3.

“The DOE is managing both situations in real time,” Garin said. “Our directive is to restore normal conditions as quickly as possible and protect consumers from prolonged supply disruptions.”

To help ease the strain on the grid, Meralco activated its Interruptible Load Program (ILP), asking participating commercial and industrial customers to shift temporarily to their own generator sets.

As of 3:40 p.m., Meralco said it had secured more than 240 MW of de-loading capacity under the ILP.

The utility also urged consumers to conserve electricity while restoration efforts continue.

Meanwhile, the Visayas Grid was also placed under Red Alert from 3:00 p.m. to 8:00 p.m. due to forced outages, high demand, and the lack of imported power from Luzon.

NGCP said 12 plants in the Visayas have remained on forced outage since March, while several others continue operating on limited capacity, leaving 862.3 MW unavailable to the grid.