The Department of Energy (DOE) directed the National Grid Corporation of the Philippines (NGCP) and several power generation companies to immediately restore affected transmission lines and generating units after Red and Yellow alerts were raised in the Luzon and Visayas grids on Tuesday.

In an official statement issued today, Energy Secretary Sharon S. Garin said the grid issues began at around 6:30 AM after the 500-kilovolt Tayabas-Ilijan and Dasmarinas-Ilijan transmission lines tripped.

The incidents disconnected the 1,200-megawatt (MW) Ilijan 1 and 2 plants as well as EERI Units 1, 2, and 3 with a combined capacity of 1,262.1 MW from the grid.

At around 6:34 AM, Masinloc Unit 3, with a capacity of 325 MW, also went on forced outage.

Garin directed NGCP to “immediately resolve transmission constraints affecting the dispatch of large power plants” and ordered San Miguel Power Group Corporation to expedite the restoration of Masinloc Unit 3.

“The DOE is managing both situations in real time,” Garin said. “On both the transmission side and the generation side, our directive is the same: restore normal conditions as quickly as possible and protect Filipino consumers from prolonged supply disruptions.”

NGCP later declared a red alert in the Luzon grid from 3 PM to 8 PM, while yellow alerts were raised from 2 PM to 3 PM and again from 8 PM to 10 PM.

According to NGCP, available capacity in Luzon fell to 12,447 MW against peak demand of 12,537 MW, while a total of 4,681.6 MW became unavailable to the grid.

A Red alert is issued when power supply becomes insufficient to meet consumer demand and regulating reserve requirements, while a Yellow alert is raised when operating margins fall below contingency reserve requirements.

The DOE also reported that the Visayas grid was placed under Red alert from 3 PM to 8 PM and under Yellow alert from 8:01 PM to 9 PM.

The Visayas grid alerts were linked to outages involving Therma Visayas Inc. Units 1 and 2 and Panay Energy Development Corporation Unit 3.

Garin ordered the DOE Visayas Field Office to conduct on-site inspections and coordinate closely with the affected generation companies to help restore the units safely and quickly.

Meanwhile, Manila Electric Company (Meralco) said it had begun coordinating with customers enrolled under the Interruptible Load Program (ILP) to help reduce electricity demand and ease pressure on the grid.

“If necessary, we are ready to implement manual load dropping (MLD) or rotating power interruptions as part of our responsibility to manage the system condition,” Meralco said in a statement issued today.

The DOE added that Meralco advised load dropping within its franchise area could be avoided if sufficient ILP capacity is deployed.

The ILP is a voluntary demand-side management program where large customers temporarily switch to their own generator sets during periods of tight power supply.

NGCP also said it may implement Manual Load Dropping (MLD) from 4 PM to 5 PM in parts of Abra, Bataan, Batangas, Metro Manila, Albay, and Camarines Norte to maintain the integrity of the power system.

The grid operator said the schedule could still be cancelled if system conditions improve, particularly if actual demand falls below projections. NGCP also urged the public to exercise prudence in electricity consumption.

The DOE said it continues to monitor both grid situations in real time while coordinating with NGCP, generation companies, and distribution utilities as restoration efforts continue.

As simultaneous transmission and generation outages continue to strain grid conditions, will emergency measures such as the Interruptible Load Program be enough to prevent wider power interruptions during peak demand periods?

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