MANILA (UPDATE 3) -- The Luzon and Visayas power grids were again placed on red alert Thursday, April 18, the National Grid Corporation of the Philippines (NGCP) said.

In a Facebook post, the NGCP said the Luzon grid would be on red alert from 3 p.m. to 4 p.m., and from 8 p.m. to 10 p.m.

The Visayas grid was on red alert from 6 p.m. to 7 p.m. but this was later lifted.

For the Luzon grid, the NGCP said that as of 8 p.m. it may implement Manual Load Dropping (MLD) or rotating brownouts from 8 p.m. to 9 p.m.

• ISECO (parts of Ilocos Sur)
• ISELCO I (parts of Isabela)
• QUIRELCO (entire province of Quirino)
• CAGELCO 2 (parts of Cagayan)
• SFELAPCO (parts of Pampanga)
• QUEZELCO (parts of Quezon Province)
• CANORECO (parts of Camarines Norte)

The NGCP earlier also placed the following areas on red alert from 3 p.m. - 4 p.m. to maintain the integrity of the power system: 

• NUVELCO (parts of Nueva Vizcaya)
• CAGELCO I Feeders 1 and 3 (parts of Cagayan)
• SORECO II (Parts of Sorsogon Province)
• ZAMECO II ( parts of Zambales)

For the Visayas grid, the NGCP earlier put the following areas on red alert from 6 p.m. to 7 p.m:

• CENECO (parts of Negros Occidental)
• NOCECO (parts of Negros Occidental)
• NORECO II (parts of Negros Oriental)
• MORE (parts of Iloilo City)
• ILECO II (parts of Iloilo Province)
• CAPELCO (parts of Capiz)
• AKELCO (parts of Aklan)
• LEYECO V (parts of Leyte)
• LEYECO II (parts of Leyte)

As of 7:13 p.m. the NGCP said it has lifted the red alert for the Visayas grid but a yellow alert was still in effect from 8 p.m. to  9 p.m.

A red alert is issued when the power supply is insufficient to meet consumer demand.

The Luzon grid yellow alert meanwhile will be in effect from 1 p.m. to 3 p.m. and will be on yellow alert again from 4 p.m. to 8 p.m., and 10 p.m. to 11 p.m.

A yellow alert is issued when the operating margin cannot meet the transmission grid’s contingency requirement.

The NGCP said 19 power plants in Luzon are on forced outage, while one is running on derated or lower capacity, which together have decreased available capacity by 1,891.3 megawatts unavailable to the public.

The Visayas grid meanwhile was put on red alert due to higher forecasted demand this evening.

Thirteen power plants in the Visayas are on forced outage, while 9 others are running on derated or lower capacities, for a total of 696.7MW unavailable to the grid.