The National Grid Corporation of the Philippines (NGCP) raised a yellow alert on the Visayas grid early Wednesday due to a thin power supply after a 6.9-magnitude earthquake triggered multiple plant and transmission line trips.

The transmission operator said the available capacity in the Visayas as of this morning stood at 1,888 megawatts (MW), just above peak demand of 1,839MW. 

The quake caused 27 power plants to trip, with 16 others already offline. One plant is operating at reduced capacity, leaving 1,654.7MW of generation unavailable.

The earthquake at 9:59 PM on 30 September split the Leyte, Samar, and parts of Bohol grid from the Cebu-Negros-Panay-Bohol network. 

NGCP reported damage to its Daanbantayan Substation and the tripping of four 230kV transmission lines. Cebu plants  such as Therma Visayas, Cebu Energy units 1–3, KSPC, and TPC1A and Negros’ Palinpinon Geothermal 1 also tripped, cutting 641MW of load.

A yellow alert signals that the grid’s operating margin is insufficient to meet contingency requirements. 

Luzon and Mindanao grids remain stable. 

The quake caused widespread damage to transmission lines across Leyte and Samar, leaving key lines like Daanbantayan-Tabango, Tabango-Kananga, Ormoc-Babatngon, and Paranas-Calbayog out of service.

Restoration efforts are underway, and some lines have already been brought back online, including the Ubay-Maasin 138KV at 4:01AM, Ormoc-Maasin 138KV Line 1 at 4:18AM, and Ormoc-Isabel 138KV at 5:11AM.

Meanwhile, power transmission in the rest of the Visayas—covering Panay, Negros, Cebu, and Bohol—remains stable, providing some relief amid ongoing recovery efforts.

NGCP said it will continue aerial and ground inspections and restore affected lines when safe. Updates will be issued every four hours until full service resumes.