Half of the largest island in the Philippines was affected in early May by a power failure that shut down six power plants.

The massive blackout affected the capital city of Manila as well as several nearby provinces on May 8th. An initial report from the National Grid Corporation of the Philippines (NGCP) indicated that it was caused when a unit of the Calaca power plant tripped along with the 230 kV Calaca-Binan transmission line.

The failure occurred at 2pm and caused six power plants with a combined capacity of 3700 MW to shut down, including the Sual coal plant and Ilijan gas fired power plant. Power was restored by midnight, according to the Department of Energy (DOE).

The National Grid Corporation of the Philippines (NGCP) is to carry out a "thorough evaluation" of the incident, which led to "the unexpected series of tripping of several power plants and transmission facilities", according to a DOE statement.

The DOE has also requested the Grid Management Committee to conduct its own investigation in line with the country’s grid code. "From there, policies and regulatory intervention will be established to prevent such incidents from occurring in the future," said the DOE.