MANILA, Philippines -- The National Grid Corp. of the Philippines (NGCP) issued yellow and red alerts for the Luzon, and Visayas grids today, Thursday, due to inadequate power supply.

According to the transmission firm, the Luzon grid will be on yellow alert from 12 noon to 1 p.m., 5 p.m. to 6 p.m. and 10 p.m. to 12 midnight; and on red alert from 1 p.m. to 5 p.m. and from 6 p.m. to 10 p.m.

The Visayas grid will be on yellow alert from 12 noon to 2 p.m., 4 p.m. to 6 p.m., and 7 p.m. to 10 p.m. It will be on red alert from 2 p.m. to 4 p.m., and 6 p.m. to 7 p.m.A red alert is issued when power supply is insufficient to meet consumer demand and the transmission grid's regulating requirement.

A yellow alert is when the operating margin is insufficient to meet the transmission grid's contingency requirement.