The Mindanao grid will be placed under yellow alert from 1 p.m. to 8 p.m. on Wednesday, August 12, the National Grid Corporation of the Philippines (NGCP) said.

In an advisory, NGCP said the Mindanao grid has an available capacity of 2,779 megawatts (MW) against a peak demand forecast of 2,689 MW.

The grid has nine power plants on forced outage, while nine others are operating at derated capacities, resulting in a total of 621.6 MW of capacity unavailable to the grid.

The additional yellow alert declaration was attributed to the maintenance outage of GNPK 2 that began on July 28, the emergency shutdown of GNPK 1 on August 9 due to a boiler tube leak, and high forecasted system demand.

"A yellow alert is issued when the operating margin is insufficient to meet the transmission grid’s contingency requirement," the grid operator said.