NGCP declares ‘yellow alert’ for Luzon power grid

RESERVE ENERGY in the Luzon grid fell below minimum levels on Tuesday, prompting the system operator to issue a “yellow alert” a day after the Energy department gave its assurance that power supply is sufficient for the dry season.

Privately-owned National Grid Corp. of the Philippines (NGCP) said the country’s biggest power grid was placed on yellow alert between 11:00 a.m. and 5:00 p.m. and again from 7:00 p.m. to 9:00 p.m.

NGCP said available capacity on Tuesday was at 10,115 megawatts (MW) while peak demand during the day hit 9,491 MW.

“Luzon grid is on yellow alert due to the unexpected shutdown and limited generation of some power plants, and high power demand,” the system operator said.

It deferred to the Department of Energy (DoE) the announcement on which power plants were on an unscheduled shutdown.

The warning came even before the expected full impact of the El Niño weather phenomenon in May. The DoE expects peak demand in Luzon to reach 11,403 MW during that month.

“This is the first yellow alert for the Luzon grid this year,” NGCP said.

NGCP has several levels of reserve energy that it uses to stabilize the fluctuating power demanded from the electricity grid.

A frequency regulating reserve is the standard operating requirement to maintain a balance between available capacity and system demand, and should address small variations during normal operation. The regulating reserve is ideally equivalent to 4% of the demand for the hour.

On top of the regulating reserve, NGCP also maintains a contingency reserve that it allocates to immediately answer any reduction in supply when the largest power generating unit online — usually at 600 MW — fails to deliver.

Aside from these reserves, the operator also maintains a dispatchable reserve that is readily available to replenish lost contingency reserve.

When these reserves fall below ideal levels, NGCP issues a “yellow alert,” which is downgraded to a “red alert” when the power supply situation worsens.

The other day, the Department of Energy (DoE) said it adjusted the output of the hydroelectric power plants (HEPPs) in Luzon after the forecast “weak” El Niño during the April-June months. It placed the expected capacity reduction at 30%.

“While El Niño is seen to have the greatest impact in Luzon due to the number of HEPPs in the area, the grid will continue to be under normal conditions,” it said.

The DoE also said that in the instance of forced outages in the Luzon grid, there would be an additional 350-MW buffer, with a 200-MW “importation” coming from the Visayas grid and 150MW coming from the remaining Malaya diesel power plant. —