The Department of Energy on Friday said extreme heat was among the factors that may have contributed to recent power plant trips that triggered outages in parts of Luzon and Visayas, as it urged the public to conserve electricity while investigations are ongoing.

“We are also asking for help and cooperation from our consumers, who, through saving or properly using electricity, will help reduce stress on our electric power industry system,” Energy Undersecretary Mario Marasigan said during the “Bagong Pilipinas Ngayon” interview.

Marasigan said the power interruptions experienced on 13 May were caused by unexpected outages involving several power plants and transmission facilities.

He said two major National Grid Corporation of the Philippines transmission lines — the Dasmariñas-Ilijan 500-kilovolt line and the Tayabas-Ilijan 500-kV line — tripped, forcing five natural gas-fired power plant units offline.

The DOE has already sent notices to both generation companies and NGCP seeking explanations and corrective measures to immediately restore services.

Marasigan added that the agency is closely coordinating with plant operators and monitoring repairs hourly to determine when affected facilities can resume supplying electricity to the grid.

The DOE is also monitoring around 1,400 megawatts worth of new power facilities currently undergoing testing and commissioning.

Meanwhile, NGCP announced on its official Facebook page that it would implement Manual Load Dropping in several areas Friday to maintain grid stability.

Affected areas include parts of Ilocos Norte, Ilocos Sur, La Union, Pangasinan, Nueva Vizcaya, Tarlac, Pampanga, Zambales, Batangas, Camarines Sur, and portions of Metro Manila under Meralco coverage.

NGCP said the rotational outages may be canceled if power demand falls below projections.

Manual Load Dropping refers to the intentional and scheduled disconnection of power in certain areas to prevent the entire grid from collapsing during periods when electricity demand exceeds available supply.