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Prepa Acknowledges Total Power Shutdown Wasn’t Deliberate

Automatic response by equipment following a three-second surge in voltage blacks out system in less than one minute


October 7, 2004
Copyright © 2004 CARIBBEAN BUSINESS. All Rights Reserved.

The Puerto Rico Electric Power Authority (Prepa) acknowledged that the island’s power grid shutdown during Tropical Storm Jeanne was in response to a power surge and not a manual shutdown as announced by Gov. Sila Calderon and Prepa Executive Director Hector Rosario.

Rosario along with Prepa Deputy Executive Director Hector Alejandro, Electricity Systems Director Edwin Rivera, and Operations Division Manager Carlos Castro visited CARIBBEAN BUSINESS last Friday to discuss in detail how the storm’s events unfolded.

Rivera told CARIBBEAN BUSINESS that around noon Sept. 15, a sudden, three-second surge in voltage, probably in the north, activated the power plants’ automatic shutdown programs. "The system protected itself automatically and shut down," said Rivera. "All the electricity-generating units have automatic protection programs to maintain the equipment at optimum levels. If at any time these protections detect danger to the unit, it shuts down. The event that provoked the shutdown was a surge in voltage, a reduction or variation possibly caused by power lines touching each other. It took about three seconds to happen, but it was during this period that the units detected dangerous conditions and shut down."

Still, the Prepa executives remain adamant in their rejection of the word "collapse" to describe what happened during the storm. Rivera and Castro said there was no damage associated with the passage of Tropical Storm Jeanne and the power grid’s shutdown, contrary to CARIBBEAN BUSINESS reports based on an anonymous source within Prepa (CB Sept. 30).

"If there had been damage to the system’s generating capacity we wouldn’t have been able to generate the record 5,000 megawatts that we achieved this week," said Rivera.

Prepa has yet to find the actual site where the power failure occurred but is concentrating on Palo Seco. Prepa’s Rosario said he was confident of the work being done by technicians to pinpoint and correct the damage. This week, the agency faced a review by a Professional College of Engineers & Land Surveyors of Puerto Rico (PCELSPR) ad hoc committee that has evaluated the events that occurred before and during Tropical Storm Jeanne’s passage through the island.

The findings were to be disclosed this week during a press conference headed by PCELSPR President Roberto Rexach Cintron and Committee Chair Edison Aviles. A preview of the findings shown to CB states that two possibilities exist for the shutdown.

"The first hypothesis is that a series of events associated with the storm critically affected the system’s operation...causing a reactive [power] deficiency at a critical point," states the PCELSPR’s finding. Reactive power is used to control voltage in the transmission network, establishing and sustaining the electric and magnetic fields of alternating current equipment.

"Palo Seco’s thermoelectric plant generators unsuccessfully tried to supply the reactive [power], which provoked a progressive and uncontrollable decrease in voltage, activating the power grid’s generating units’ automatic protection programs," states the finding.

"The second hypothesis, offered by some members of the PCELSPR’s ad hoc committee, establishes that a disturbance near Palo Seco thermoelectric plant activated Unit 4’s automatic protection program, causing it to shut down. Since this unit was supplying 13% of the power grid’s electricity, this created a deficiency in the reactive, provoking a sudden voltage decrease, and a progressive and uncontrollable voltage instability in the system, which caused the rest of the generating plants to activate their automatic protection programs," the report says.

The report concludes, "The commission arrived at the assumption that unstable voltage activated the [power system’s] automatic protection, leading to its disconnection, except for Aguirre Unit 1 which was appropriately disconnected manually after the automatic protection system didn’t turn on. To establish the factual causes, we must perform simulations. Prepa engineers and technical personnel’s management of the power grid followed good practices in engineering and established procedures."

According to PCELSPR’s Rexach, "The power grid wasn’t shut down by any one person. It was initiated after a sudden voltage surge that cut down the power throughout the island in barely 31 seconds. In the coming months, we will continue reviewing the facts of the event and proceed with simulations to determine if any revisions need to be made to the established operation systems."

This Caribbean Business article appears courtesy of Casiano Communications.
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