Initial Report Outlines Investigation Process, Overview of Damaged Equipment and Critical Next Steps

San Juan, Puerto Rico, April 12, 2022 – This afternoon, LUMA submitted an initial report outlining the preliminary findings of the ongoing investigation into the island-wide blackout to the Puerto Rico Energy Bureau (PREB). The report outlined key preliminary findings including a timeline of events, an overview of damaged equipment, a summary of the Costa Sur energization plan and critical next steps in the ongoing investigation.

“The magnitude of the April 6 event serves as an important reminder that Puerto Rico’s electric grid is incredibly fragile and is only as strong as its weakest link. This significant outage event, which deeply frustrated and impacted so many of our customers, is symptomatic of an electric grid that suffered from years – if not decades – of neglect and mismanagement. While the investigation is ongoing, and will take time, we are committed to being fully transparent with our customers, regulators and the legislature with our findings to determine how we must all work together to identify the actions which must be taken to prevent an outage of this scale from ever occurring again,” said LUMA President and Chief Executive Officer Wayne Stensby.

In the report, LUMA outlined the following:

• The process the company will undertake to complete the thorough investigation into the island-wide blackout that affected its 1.5 million customers.
• The process of safely and formally collecting evidence from relevant sources, internally and externally, to inform the investigation.
• Makes it clear that when the evidence collection is completed there will be an analysis of all data, including an independent forensic analysis.
• Outlines that a complete and thorough analysis is expected to take weeks, and the findings and conclusions of the root causes of this event will be made public and provided to all relevant parties.

Among the preliminary findings included the following:

• On April 6, 2022, at 8:42 PM, oil-circuit breaker (OCB) #0082 failed at closing during an attempt to connect the PREPA operated Costa Sur Steam Plant’s Unit #5 to the grid.
• The oil-circuit breaker (OCB) #0082 connects to the PREPA operated Costa Sur Steam Plant’s Generation Unit #5. While synchronizing Unit #5 to the grid and during the circuit breaker’s closing operation, the circuit breaker experienced a failure. This failure caused damage to Bus #6 which is in the vicinity of the breaker in question.
• The failure affected three adjacent circuit breakers and several portions of the substation’s lattice structures.
• Due to the circuit breaker’s failure, the 230 kV circuits at the Costa Sur substation needed to open to clear the fault, which disconnected EcoEléctrica from the grid and resulted in subsequent outage events that cascaded into a full blackout of Puerto Rico’s electrical system.
• The island lost power 19 seconds after the initial fault was recorded.
• The exact cause of the oil circuit breaker failure is still under investigation.
• By 3:00 AM on Sunday, April 10, 99% of customers impacted by this event had been restored.
• PREPA maintenance records for oil circuit breaker (OCB) #0082 indicate the maintenance was current and had been serviced in March 2020. The recommendation from PREPA on the last report was to place the circuit breaker into service and the next breaker maintenance was planned for 2023, per industry standards.
• Since June 2021, LUMA maintenance crews have completed 17 maintenance actions at the Costa Sur switchyards.

“While it has only been ten months since we assumed operations of Puerto Rico’s electric transmission and distribution system, LUMA is determined to work together with all parties –PREPA, the PREB and the Government – to prevent dramatic outage events we experienced last week from happening again. While there has been wild speculation made about the causes, the Puerto Rican people, and our customers deserve answers – not guesses. All of us at LUMA are determined to conduct a thorough and complete investigation, including an independent forensic review of the failed equipment, even as we continue the incredibly hard work of repairing and rebuilding an electrical infrastructure that has suffered years – if not decades of neglect,” added Stensby.

About LUMA

LUMA is a Puerto Rican company that, since June 1, 2021, operates and manages the electric power transmission and distribution system in Puerto Rico. LUMA is a company driven by a mission to transform the electrical transmission and distribution system to provide all Puerto Ricans with the reliable, resilient, cleaner and affordable electrical grid they deserve. As a customer-centric company, LUMA’s entire workforce of more than 3,000 employees is focused on safely delivering an exceptional customer service experience to its 1.5 million customers.