The National Grid Corp. of the Philippines (NGCP) placed the Visayas grid under red and yellow alerts on July 9 due to power plant outages and high projected electricity demand.
The red alert was lifted at 12:45 p.m. after supply conditions improved, but a yellow alert remained in effect until 10 p.m. because operating margins stayed below contingency requirements.
NGCP reported 959.3 MW of capacity unavailable, attributing the supply shortage to the forced outage of 10 power plants, including units at Therma Visayas Inc. and Palm Concepcion Power Corp.
THE Visayas grid returned to red and yellow alert status Thursday, July 9, after power plant outages and expected high demand tightened supply across the region.
The alerts were issued barely a week after the National Grid Corp. of the Philippines (NGCP) said supply warnings in the Visayas had stopped following the return of a major generating unit in Western Visayas.
In its 8 a.m. advisory, NGCP said the grid had 2,561 megawatts (MW) available against projected peak demand of 2,568 MW, leaving a seven-MW shortfall. It placed the grid under yellow alert from 3 to 5 p.m. and 7 to 10 p.m., and red alert from 5 to 7 p.m.
Supply gap
In a 1 p.m. update posted at 1:19 p.m. Thursday, NGCP said the red alert had been lifted as of 12:45 p.m. after supply conditions improved. Available capacity stood at 2,532 MW against peak demand of 2,354 MW.
The grid, however, remained under yellow alert until 10 p.m. because its operating margin was still below the transmission grid’s contingency requirement.
Plant outages
NGCP traced the alerts to the continued unavailability of Therma Visayas Inc. Units 1 and 2, the recent outage of the 135-MW Palm Concepcion Power Corp. plant in Iloilo and the forecast of high demand.
Michael Ortega Ligalig, government relations and regional affairs lead specialist for NGCP’s Cebu-Bohol Area-District 2, said the grid operator was monitoring the system because demand could still rise during peak hours.
Ligalig said NGCP may implement manual load dropping if demand continues to rise while available generating capacity remains unchanged. Manual load dropping refers to the deliberate disconnection of power load to keep the grid from becoming unstable when supply is not enough.
Earlier relief
SunStar Cebu reported on July 2 that the Visayas grid had been free of yellow alerts since 2:40 p.m. on July 1 after Panay Energy Development Corp. (PEDC) Unit 3 in Western Visayas returned to service.
During NGCP’s Power 101 forum on July 2, Amado Otarra, senior supervisor for Network Operations, said PEDC Unit 3 restored 150 MW of capacity after weeks offline, ending daily yellow alerts that began on May 11.
At the time, NGCP said the return of PEDC Unit 3 reduced the immediate risk of rotating outages but did not mean the grid had returned to normal because several major generating units remained offline.
Even with PEDC Unit 3 back online, Therma Visayas Inc. Units 1 and 2 and Kepco SPC Power Corp. Unit 1 in Cebu Province remained out of service. Otarra said the two TVI units, each capable of producing 169 MW, were expected to return in September after maintenance work meant to prevent future technical problems.
NGCP said 10 power plants were on forced outage and 14 others were running on derated capacities, leaving 959.3 MW unavailable to the Visayas grid.
A yellow alert is issued when the operating margin is insufficient to meet the transmission grid’s contingency requirement. A red alert is declared when available supply is insufficient to meet consumer demand and the transmission grid’s regulating requirement.
NGCP advised the public to monitor its official advisories as it continued to assess supply conditions across the Visayas. / ABC & SHERYN MAE SINOY, UV INTERN