The National Grid Corp. of the Philippines (NGCP) placed the Visayas grid under red and yellow alerts on July 9 after a series of power plant outages and high projected electricity demand tightened supply across the region.
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 the transmission grid's contingency requirement.
Supply gap triggers warnings
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. The grid was placed under yellow alert from 3 to 5 p.m. and 7 to 10 p.m., and red alert from 5 to 7 p.m.
By 1 p.m., available capacity stood at 2,532 MW against peak demand of 2,354 MW, allowing the red alert to be lifted. However, the yellow alert persisted because the operating margin was still below the transmission grid's contingency requirement.
Plant outages cause shortage
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. According to NGCP, 10 power plants were on forced outage and 14 others were running on derated capacities, leaving 959.3 MW unavailable to the Visayas grid.
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 noted that NGCP may implement manual load dropping if demand continues to rise while available generating capacity remains unchanged.
Recent relief short-lived
The alerts came barely a week after NGCP said supply warnings in the Visayas had stopped following the return of Panay Energy Development Corp. (PEDC) Unit 3 in Western Visayas. On July 1, the grid had been free of yellow alerts since 2:40 p.m. after PEDC Unit 3 restored 150 MW of capacity, ending daily yellow alerts that began on May 11.
Despite that relief, several major generating units remained offline. Amado Otarra, senior supervisor for Network Operations at NGCP, said during a July 2 forum that Therma Visayas Inc. Units 1 and 2 and Kepco SPC Power Corp. Unit 1 in Cebu Province were still out of service. Otarra said the two TVI units, each capable of producing 169 MW, were expected to return in September after maintenance work.
Alert definitions and public advisory
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.
