ILOILO City – The two large power plants in Panay Island explain why their facilities tripped, contrary to the National Grid Corporation of the Philippines’ (NGCP) statement that the former caused the power blackout.
Unit 1 of the Panay Energy Development Corporation (PEDC) with 83 megawatts (MW) load capacity tripped at 12:06 p.m. on Jan. 2, and after two hours or at 2:19 p.m., PEDC’s Unit 2 with an 83-MW load capacity and the Palm Concepcion Power Corporation (PCPC) with 135-MW followed. This also includes the six other small power plants in the island.
“The unscheduled maintenance shutdowns of the largest power plants in Panay Island were the primary cause of the power interruption. We emphasize the need for improved planning to ensure sufficient generation per island with a well-balanced mix of fuels and technology,” NGCP said.
In an earlier statement, NGCP reported that with the tripping of three of the largest power-generating units and the planned maintenance shutdown of PEDC Unit 3 (150 MW), 451 MW, or 68.75% of the total 656 MW in-island generation, was lost to the Panay sub-grid.
Maintenance shutdowns and deration of plants outside the Department of Energy’s (DOE) approved Grid Operating and Maintenance Program also contributed to the lack of power supply.
Here, Panay News reached out to Engr. Albin Kintanar, Vice President for Operations of PCPC.
Kintanar explained that the power demand of Panay is 400 MW per day. In transmission lines, there are three lines, or phases A, B, and C, and those three phases should have equal voltages.
“During that time, ‘yong Phase A sa nakita namin ay 138 kilovolt (KV), Phase B – 128 KV, tapos Phase C – 134 KV. So, may discrepancy na sia at ‘yong A and B is 6.72%, which is in terms sa standard sa grid medyo abnormal na ‘yan. Usual, ang maximum na discrepancy is about 3% as per standard,” Kintanar elaborated.
Due to the variations in voltage in the grid, the change was detected by PCPC’s line, consequently triggering the protection measure of the power plant, resulting in its disengagement from the grid.
“So, ‘yong process ng disengagement sa planta since we are carrying about 235 MW nasa full load kami that time. ‘Pag-na-disengage sia wala ng pupuntahan ang power namin kasi nakahiwalay na sa grid. So, ang mangyayari to protect our power plant, magti-trip na rin ‘yong power plant, nag-stop operating kasi wala na talagang power eh. So ‘yong term na nag-trip kami was the consequence of the imbalance in the system voltage,” added Kintanar.
He also clarified that when they tripped out, a large power supply could have been left for Panay Island. But since it happened together with PEDC’s Unit 2, it caused a domino effect on small power plants.
“‘Yong simultaneous trip out ng six power plants kasi there is domino effect or cascading effect, ‘pag nawala ang isang malaki and hindi na kaya ng maliliit na power plant na i-sustain ‘yong supply sa Panay, ‘yong protection nila made them tripped out. So, sunod-sunod kaming nag-trip out, so nagkaroon ng blackout sa Panay,” he further said.
Kintanar also believed that this should have been balanced out if power distributors curtailed the load or demand to balance the system.
Atty. Antonio “Jun” Cabalhug, Jr., First Vice President, Panay Site Head of PEDC, meanwhile, explained that PEDCs’ Unit 1 tripped due to the momentary activation of the vibration protection of Boiler Feedwater Pump (BFP) during load reduction, following the real-time dispatch (RTD).
PEDC Unit 1 immediately restarted but was interrupted due to a total blackout of the Panay grid at around 2:19 p.m. PEDC Unit 2 tripped due to the abrupt drop in grid voltage, prompting its shutdown.
“Para sa amin, ang shutdown ng planta is just an effect, kasi nag-respond na lang ang protection namin. So, there must be something na nag-trigger,” Cabalhug told Panay News.
The trigger factor Cabalhug referred to was the “low voltage” on the grid they recorded.
“‘Yong sa Unit 2, ang nakita namin as per record, nakita ng protection namin na nag-low voltage ‘yong grid, so dahil may protection sia para hindi masira ‘yong major equipment, especially ‘yong generator na hindi masusunog dahil mababa ‘yong boltahe ng grid kasi requirement ‘yon na dapat pareho ‘yong voltage ng ating generator at saka sa grid. If under voltage, nag-react sia kasi ‘yon ang function niya, tini-trip niya,” Cabalhug said.
As to why NGCP’s grid experienced low voltage, he has no idea.
Cabalhug also clarified that PEDC’s Unit 1 should not be pointed at as the cause of the grid’s low voltage since NGCP itself said during the forum with the governors in Region 6 on Thursday morning, Jan. 4, that from 12 noon to 2 p.m. on Jan. 2, power supply in Panay Island was actually stable or sufficient.
PEDC Unit 2 came back into the grid after receiving stable feedback power from the grid operator.
Unit 2 promptly initiated start-up procedures and successfully synchronized with the grid at 11:45 p.m. on Jan. 2. PEDC Unit 1 followed suit and synchronized at 7:45 a.m. on Jan. 3, 2024.
Meanwhile, PEDC Unit 3 is presently undergoing its scheduled preventive maintenance schedule/shutdown, which commenced on Dec. 19, 2023, with necessary approvals from regulators, including the grid operator./PN
