CEBU CITY—A power outage that lasted for seven hours in some places hit four provinces in the Visayas on Thursday and the cause has not been determined.
The brownout occurred at 1:45 a.m. in Cebu, Bohol, Samar and Leyte provinces. Power was restored in Cebu and Bohol past 3 a.m. But in areas in Samar and Leyte, the brownout lasted until 9:09 a.m.
The National Grid Corp. of the Philippines (NGCP) has yet to determine the cause of the power interruption but it was traced to the Cebu grid, said Rosette Martinez, NGCP corporate public affairs officer.
“We are still assessing the cause of the power interruption in the Visayas. But our Tongonan (geothermal) plants (in Leyte), while affected, were not the cause of the interruptions,” Martinez said.
Initial reports indicated that there was a trip-off in the transmission line in Toledo City. NGCP, however, has yet to determine what caused the trip-off but it led to low voltage in power plants in Cebu and Leyte.
When the transmission line tripped off, Martinez said the line was disconnected from the power generating plant of Korean Power Corp. (Kepco) in Naga City, which generates 300 megawatts.
Lines were also disconnected from one generating unit of Cebu Energy Development Corporation (CEDC), which generates 130 MW of power.
Since at least 430 MW were lost, Martinez said power plants in the Visayas grid were unable to operate to their full capacity.
With power grids in Cebu and Leyte interconnected, power generation facilities tripped off as a result of the imbalance in supply.
“The power plants are operating at a certain voltage,” said Martinez.
“If they have detected low voltage, the automatic response of their power generating units is to trip off,” she said.
“But this doesn’t mean that they are no longer functioning. They have installed systems that are like voltage regulators. They trip off to save the power generating units in case of low voltage,” Martinez said.
The trip-off affected Bohol since its power supply comes from facilities in Leyte. Electricity passes through a submarine cable from Maasin City in Southern Leyte to Ubay town in Bohol.
Martinez said power in the transmission line in Toledo City was restored.
Martinez said the brownouts were just an “isolated incident.”
“This is not related to supply issue. If there’s a supply problem, usually, we will implement load curtailment but at present, there’s no official advice on the need to curtail supply,” she told the Inquirer. With a report from Jhunnex Napallacan, Inquirer Visayas