Manila, April 24 -- The National Grid Corp. of the Philippines (NGCP) has placed the Mindanao grid under yellow alert, and the Luzon and Visayas grids under red and yellow alert.

In its advisory Wednesday, the NGCP said the Mindanao grid is under yellow alert from 10 a.m. to 4 p.m., as nine power plants went offline and five more plants are running on a derated capacity.

A total of 673.98 megawatts (MW) were unavailable to the grid, causing the declaration of a yellow alert in the southern part of the country.

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

Peak demand in the Mindanao grid on Wednesday is projected at 2,761 MW, with available ...