Rotating brownouts expose grid dependence risks – analysts

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MANILA, Philippines — The rotating blackouts that hit Luzon and the Visayas this week exposed a deeper structural weakness in the country's power system: heavy dependence on a small number of major power plants, shared fuel facilities and critical transmission corridors.

Policy group Institute for Climate and Sustainable Cities said the May 13 outages showed how a single disruption could quickly cascade into a broader supply crisis.

According to ICSC on Thursday, May 14, available capacity in Luzon fell sharply from the National Grid Corp. of the Philippines' earlier forecast of 16,975 megawatts to just 12,447 MW after key transmission lines and power plants simultaneously tripped.

The group said the shutdown of the 500-kilovolt Dasmariñas-Ilijan line at 4:48 a.m. and the 500-kV Tayabas-Ilijan line at 6:39 a.m. on Thursday disconnected nearly 2,500 MW from the grid, including the Ilijan 1 and 2 plants and EERI Units 1, 2 and 3, all of which are liquefied natural gas, or LNG, facilities.

Vulnerabilities

The outages came as NGCP placed the Luzon and Visayas grids under red and yellow alerts on May 13 and again on May 14.

The Visayas faced possible outages of up to seven hours across 32 areas, while Luzon, including Metro Manila, experienced hour-long outages in nine areas, marking the first back-to-back serious supply alerts in two years.

ICSC noted that the same LNG plants also suffered simultaneous shutdowns on April 16 due to problems involving the LNG terminal supplying their fuel, underscoring the risks of relying on shared infrastructure.

"Whether through a shared LNG terminal or a critical transmission corridor, disruptions in these critical nodes can quickly cascade into broader system-wide supply shortages and grid instability," the group said.

"Reserves today are sized based on the largest power plant connected to the grid. But if a single shared facility, such as an LNG terminal or critical transmission corridor, can affect multiple plants at once, then that shared infrastructure should arguably become the benchmark for reserve requirements," ICSC Chief Data Scientist Jephraim Manansala said.

The group added that forced outages at coal facilities, including Masinloc Unit 3 and Mariveles Power Generation Corp. Unit 4, further tightened supply conditions.

ICSC warned that no single facility should be capable of putting the entire grid at risk.

"To break the cycle of grid alerts and rotating blackouts, the Philippines must move towards a more decentralized, diversified, and flexible power system," the group said.

It called for greater investment in renewable energy, battery storage and fast-ramping capacity to reduce the risk of a single disruption rippling across the power system.