The Department of Energy Department of Energy (Philippines) has mobilized the Grid Reliability Task Force (GRTF) to investigate the May 13 tripping of the 500-kilovolt Tayabas–Ilijan and Ilijan–Dasmariñas transmission lines, which disconnected 2,462.1 megawatts (MW) of natural gas capacity from the Luzon grid and triggered widespread power interruptions.

The incident immediately severed key generation assets from the system, including Ilijan Blocks A and B and Excellent Energy Resources Inc. (EERI) Units 1, 2, and 3. Only EERI Unit 1 has so far synchronized back to the grid, while the remaining units and Ilijan Blocks A and B are still undergoing technical assessment before safe reconnection.

To formalize the investigation, the DOE is convening the GTRF composed of the Energy Regulatory Commission Energy Regulatory Commission, and the Independent Electricity Market Operator of the Philippines Independent Electricity Market Operator of the Philippines in line with the 2010 DOE circular on grid reliability and integrity mechanisms.

The task force also includes the National Transmission Corporation National Transmission Corporation (TransCo), and Power Sector Assets and Liabilities Management Corporation Power Sector Assets and Liabilities Management Corporation (PSALM).

The Department said the disruption also blocked power transfer from Luzon to Visayas at a time when the Visayas grid was already under tight supply conditions. System stress was further compounded when Masinloc Unit 3 (325 MW) went on forced outage, tightening reserve margins across Luzon.

The Ilijan power complex remains a critical node in Luzon’s supply architecture due to the scale of capacity transmitted through its corridors, with the DOE warning that simultaneous transmission failures of this magnitude can rapidly cascade into wider grid instability.

“Two major 500-kV transmission arteries feeding power into Metro Manila and the broader Luzon grid were suddenly cut off. These lines carried roughly 12 percent of Luzon’s supply at the time. An incident of this scale demands full technical disclosure, clear accountability, and immediate corrective action,” Energy Secretary Sharon S. Garin said.

The DOE reiterated its earlier directive for the National Grid Corporation of the Philippines National Grid Corporation of the Philippines (NGCP) to submit complete operational data, incident reports, and technical findings to establish the root cause of the disturbance.

“The public deserves a complete accounting of incidents of this magnitude. We will ensure that all operational, technical, and compliance dimensions are fully examined and that appropriate actions are taken where warranted,” Secretary Garin said.

Amid tight supply conditions in Luzon and Visayas, the DOE also urged consumers to adopt energy conservation measures, particularly during peak demand hours, to help ease pressure on the grid while restoration efforts continue.

The agency said it will maintain close monitoring of system conditions and provide further updates as additional technical findings become available.

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