TAGBILARAN CITY, Bohol: Bohol suffered an almost 20-hour blackout Sunday when the geothermal power plant in Leyte, the main source of power for Bohol, became unavailable because of heavy rain brought about by Typhoon Ruby.
Power went off at 3:10 a.m. and had been restored by 10:52 p.m. on Sunday, December 7.
In its first advisory, the National Grid Corporation of the Philippines (NGCP) explained that power transmission service in some parts of Bohol was affected by Typhoon Ruby as it triggered the tripping of the 100-megavolt-ampere transformer in Corella substation serving Bohol Light Company, Inc. (BLCI), Bohol Electric Cooperative (Boheco) I and Boheco II franchise.
At around 8:04 a.m., NGCP restored transmission service to the three distribution utilities after completing the reconfiguration of its power delivery route to temporarily draw power from the transformer at Ubay substation.
“The reconfiguration was done due to the unavailability of the 100-MVA transformer at Corella substation,” according to NGCP.
However, power went off again in a few minutes.
NGCP then coordinated with Leyte power plants which it said went offline at around 9 a.m., for the supply to be transmitted to Bohol through the 138-kV Maasin-Ubay submarine cable.
NGCP explained the 138-kilovolt Ubay-Maasin line was isolated by Under Frequency Relay (UFR) activation.
“UFR is part of an automatic scheme to maintain system balance when significant changes occur to the grid such as the unavailability of geothermal power plant in Leyte which was affected by heavy rains. Normalization will follow when system balance stabilizes,” NGCP explained.
Later in the evening, power had been restored in some parts of Bohol and by 10:52 p.m. it’s totally restored in the entire province. PNA