No clear return date for aging power plants behind Visayas outages

CEBU CITY, Philippines — Aside from the lack of base load power generators, the Visayas grid also faces aging plants, which grid operators identified as among the factors behind its instability.

Of the over 20 plants on forced outages, around 15 to 20 percent have been classified as “aging facilities,” said Engr. Amado Otarra III of Visayas System Operations of the National Grid Corporation of the Philippines (NGCP).

Several of the affected generating units have been operating for decades, including diesel plants, Otarra said.

READ MORE: Grid outlook: Visayas grid maintains thin power reserve

While repair work is underway, he said it is difficult to estimate when these facilities will be operational again or how much capacity they will ultimately contribute.

“There are about 15 or 20 percent of those plants offline now, which are expected to be back, but we don’t have the specific date as to when they will be back, and we also don’t have the specific capacity when they will be available,” Otarra added.

Older units are more prone to unplanned breakdowns. Even when running, many operate well below their original rated capacity. Repairs on these plants also tend to take longer.

The issue carries bigger consequences for grid stability because the Visayas’ interconnected system can see reserve margins drop quickly when even one large, aging power plant goes offline, a pattern officials pointed to when near-daily yellow alerts began following outages at three of the region’s largest power plants.

The concern has also prompted calls from NGCP for a comprehensive “resource adequacy” study to assess the true condition of existing plants and guide decisions on retiring, refurbishing, or replacing aging capacity.

READ: Power supply troubles affect Visayas islands

Derated power plants

Grid operators also pointed to derated power plants as another contributor to the thinning power supply in the region.

Derated means that a power generator cannot produce power at the maximum output or capacity due to several factors such as equipment deterioration, boiler problems, fuel-loading limitations, and other mechanical issues.

“Plants can sometimes be derated [by] as much as 50 percent of the capacity,” Otarra added.

After a short-lived reprieve during the first week of July, the Visayas grid remained under strain, as evidenced by the over 50 yellow alerts the NGCP has issued since May.

READ MORE: EXPLAINER: Color-coded grid alert statuses and what they mean

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