BACOLOD City — Power consumers in Negros may continue to experience rotating brownouts as insufficient generation capacity pushes the Visayas Grid into Yellow and Red Alerts, prompting distribution utilities, including Negros Electric and Power Corp. (Negros Power), to implement Manual Load Dropping (MLD).
The National Grid Corporation of the Philippines (NGCP) has directed distribution utilities across the Visayas to implement possible power interruptions as the grid continues to experience alert conditions that began during the summer months.
During a press conference at the Negros Power office in Bacolod City on September 7, Engr. Joe-Mel Zaporteza, vice president and chief operating officer of Negros Power, said the current alerts are primarily due to insufficient generation caused by multiple unscheduled outages of large power plants in the Visayas.
Zaporteza said about 488 megawatts (MW) of generating capacity are currently on forced outage, including 338 MW from TVI Units 1 and 2 and 150 MW from PEDC Unit 3, in addition to approximately 258 MW from 19 smaller generating units.
The supply situation has been further aggravated by the derating of other generating facilities, including about 83 MW from diesel peaking plants and 15 MW from hydroelectric plants due to low water inflows.
The Visayas is also receiving limited support from Mindanao, where power exports have been constrained by similar unscheduled outages at baseload plants.
Zaporteza said Mindanao’s contribution to the Visayas has at times dropped below 100 MW and even to zero.
With available generation falling short of demand, NGCP has instructed distribution utilities to reduce their loads through MLD to protect the stability of the grid.
Negros Power currently expects MLD periods to last about an hour, although the duration could still change depending on the availability of generating units and actual grid conditions.
Zaporteza said the situation is showing some improvement as several power plants have started returning to service.
“In fact, before, that was really the expectation by the first half of September—that some plants would be able to return,” Zaporteza said.
However, not all generating units are expected to resume operations immediately, with some plants scheduled to return only toward the latter part of the year.
Zaporteza said the supply shortage became particularly severe in August, when numerous generating units went offline due to forced outages and preventive maintenance.
The resulting supply deficit was too large for the grid to absorb without resorting to prolonged MLD.
“When the manual load dropping started in May, the gap was only around 30 minutes to one hour,” Zaporteza said. “But in August, many plants went out. Therefore, the gap became much bigger and the MLD lasted longer.”
The situation resulted in several hours of rotating power interruptions on some days as distribution utilities worked to keep the grid stable amid the shortage of available generation.
Despite the continuing alert conditions, Zaporteza said Negros Power expects the situation to improve this month compared with August.
Some generating plants are gradually returning online, while electricity demand is also expected to ease as the country moves beyond the summer period.
“What we’re expecting is that September would be an improvement from August because right now we’re seeing some plants going online, and in terms of demand, we’re already in the off-summer months,” Zaporteza said.
Still, Negros Power cautioned that the duration and frequency of MLD will ultimately depend on the overall condition of the Visayas Grid and the amount of generation available to meet demand.
For now, the company said consumers should continue to expect possible rotating brownouts whenever NGCP declares alert conditions and directs distribution utilities to shed load.
Zaporteza stressed that the immediate concern is not a lack of distribution capacity in Negros but a shortfall in generation across the interconnected Visayas Grid.
As long as several large generating plants remain unavailable, power interruptions will remain a necessary measure to prevent a more serious and uncontrolled grid disturbance./PN
