DOE: Coal-fired plant causes Minda-wide blackout

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Sunday, March 16, 2014

THE Mindanao-wide blackout that happened last February 27, 2014 happened after Steag State Power, Inc. (SPI)'s loss control of the reduction of load of its 205 megawatt (MW) coal-fired power plant that resulted to a tripping in the Agus Hydroelectric Power Plants.

In a transcript furnished to the media by the Department of Energy (DOE), National Transmission Corp. (Transco) president Rolando Bacani said in a press conference Friday that the power disturbance happened around 3:51 a.m. when the coal-fired power plant started to reduce load.

He said the reduction of the load was "sensed" by the Agus Units and resulted to an abrupt increase in the generation of Agus 1.


The abrupt increase in the generation caused problems on Agus 1's defectivve capacity voltage transformer (CVT) -- a transformer used in power systems to step down extra high voltage signals and provide a low voltage signal, for measurement or to operate a protective relay -- which caused the tripping that resulted to a drop in system frequency.

National Power Corporation (NPC) president Gladys Sta. Rita said the CVT of Agus 1 has already been defective prior to the blackout. She said the equipment has had two tripping incidents before the system wide collapse.

Bacani said because of the tripping of Agus 1, the automatic load dropping kicked in as a protective remedy and helped Agus 1 recover.

However, the system frequency dropped back because of the continuous reduction of the Steag power plant. This resulted to the activation of a second and third automatic load dropping.

"Because of the continuous drop in system frequency, na-activate naman 'yung underfrequency ng Agus 7 and Mount Apo power plants. So imbes na magrecover ang system frequency natin, lalong bumagsak dahil nawala 'yung dalawang planta," he said, adding that the fourth automatic load dropping was again activated as a protective measure.

Bacani said the fourth load drop was not enough to get the system frequency back and eventually caused the tripping of other power plants in the island -- Agus 7, Agus 4, Southern Philippines Power Corporation (SPPC)'s diesel-fired power plant, Agus 6, Pulangi, Agus 5, Agus 2, and Steag -- that resulted to a system-wide collapse.

"In effect, ang nangyaring blackout sa atin sa Mindanao was due to a demand and supply imbalance, causing underfrequency due to the combination of events of unwanted loss of generation of the STEAG units, the defective equipment (CVT) of Agus 1 and the insufficient automatic load dropping at off-peak scenario," he said.

However, Bacani said that if these events happened on their own and not together, there should not have been a collapse in the system.

He said in the past, there was no recorded system-side collapse when power plants in the island would trip on its own. However, for this incident, Bacani said the power plants went down all together which caused a sequence of problems that resulted to the collapse of the system.

"Parang nawalan sila (Steag) ng manibela sa control system doon sa monitoring nila. So nagkaroon sila ng problema sa electrical at hindi nila napansin. Parang eroplano o sasakyan, nawalan sila ng control. So dun na nagumpisa ang sunod-sunod sa insidente," said DOE Usec. Raul B. Aguilos.

Eugen Victor, National Grip Corporation of the Philippines (NGCP) head of Mindanao operations, said after the incident NGCP they will working closely with NPC and Steag to improve the "electrical issues" in the island like improvement on the protection of lines and protection, coordination settings with the plants.

"We hope that (the island-wide blackout) will not happen. By May or June, the supply condition in Mindanao will improve," he said.

Aguilos said the power situation in Mindanao will normalize by May 4 and that Steag is targetting that by June 4 they have already restored their full capacity. He said Steag's current capacity is only around half of its full capacity of 205 MW.

Sta. Rita said the defective CVT has already been replaced over the weekend.

"Because of that replacement ay nadagdagan pa po 'yung generation ng Agus 1, Agus 2, at iba pa. In fact, sa Agus 1, 30 MW. Sa Agus 2, another 30 MW. So ang total na nakapagdagdag ang mga plant ng NPC ng about 109 MW after the blackout," she said.

Aguilos said at this point of time, they are not yet looking into penalizing or imposing sanctions on those who are liable with the blackout.

Published in the Sun.Star Davao newspaper on March 17, 2014.


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