Puerto Rico transmission system failure leaves over a million without power
Apr 2025Published 1 May 2026Responsible editor: Chief Editor
- Where
- Puerto Rico transmission system, Puerto Rico
- Operator
- LUMA Energy
- Owner
- Puerto Rico Electric Power Authority
- What
- Transmission failure caused power loss to over 1.4 million people
- Cause
- Not reported
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Companies named in the reporting of this entry (being named is not a finding of fault): LUMA Energy, Puerto Rico Electric Power Authority
What happened
In April 2025, at around midday local time, a transmission system failure on the Puerto Rico transmission system, operated by LUMA Energy and owned by the Puerto Rico Electric Power Authority, led to a loss of supply affecting more than 1.4 million people across Puerto Rico. More than 400,000 people also lost water service, as water pumping and treatment depended on grid supply. Major generating plant shut down and traffic signals, public transport and businesses were disrupted.
Hospitals and the main airport operated on standby generators while restoration work proceeded. Public reporting indicated that supply had been restored to about 90 per cent of customers by the following day, and that external assistance was offered. The failure occurred during a period of severe geomagnetic activity, rated at the second highest level on the standard five step scale. Available reporting did not establish whether the geomagnetic conditions contributed to the transmission failure. The Puerto Rico transmission system had been rebuilt in stages over several years following major hurricane damage in 2017 and further severe weather since.
Contributing factors
The cause of the transmission failure was not established in the available reporting. Reported context included: (1) cumulative damage and staged reconstruction of the transmission system after major hurricane damage in 2017 and later storms, leaving a mix of repaired and replaced components; (2) an island transmission network with limited redundancy and no interconnection to a larger system, so restoration depended on internal black start and re synchronisation resources; (3) severe geomagnetic activity at the time of the failure. As general engineering background rather than a finding for this event, geomagnetically induced currents can saturate transformer cores, raise reactive power demand and prompt protection operations that may extend a local disturbance. No source reviewed confirmed that this mechanism applied here.
Lessons learned
- An island grid with limited redundancy means loss of one transmission element can cause wide outages, so operators should test plans for black start and resynchronisation.
- Staged rebuild after successive storms leaves mixed vintage assets, so operators should assess ageing and mixed components as a distinct risk.
- Severe geomagnetic activity coincided with the failure, so operators in exposed regions should review monitoring and mitigation measures for such events.
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Not yet known
- Cause of the transmission failure
- Whether geomagnetic activity contributed
- Cost of the outage and restoration
This entry is updated when these are reported. Get an alert for the next one like it.
Source
Published 2026-05-01. Written from public reporting. Descriptive, not investigative. See the data accuracy disclaimer.
