MANILA — The National Grid Corp. of the Philippines (NGCP) placed the Luzon grid on yellow alert on Thursday due to insufficient power supply following outages in several power plants.

In an advisory, NGCP said the alert in Luzon will be in effect from 4 p.m. to 10 p.m.

A yellow alert is raised when power reserves fall to a thin margin above demand.

Available capacity in Luzon was recorded at 12,223 megawatts (MW), slightly above the peak demand of 11,996 MW.

NGCP reported that 35 power plants are on forced outage, while 14 others are operating at reduced capacity, resulting in a total of 5,137.2 MW unavailable.

Among the affected facilities were Units 1, 2, and 3 of Excellent Energy Resources Inc., Block B of the Ilijan Power Plant in Batangas, and Magat hydro units 1 to 4 in Isabela.

The Visayas grid was also placed on yellow alert from 6 p.m. to 7 p.m.

Available capacity in the Visayas stood at 2,597 MW against a peak demand of 2,368 MW.

NGCP said 15 plants are on forced outage, while 13 are running at reduced capacity, leading to 679.2 MW of unavailable capacity.

The situation in the Visayas was also linked to the absence of power imports from Luzon through the high-voltage direct current (HVDC) link.