Some 11,000 buildings in Dublin city centre briefly lost power on Friday afternoon.
A fault on a power line at Heuston Station affected people on both sides of the River Liffey.
These were mostly in the Stoneybatter and Kilmainham areas of the city.
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Other areas such as St Stephen's Green and Rialto were also affected.
ESB crews put a temporary fix in place within five minutes.
They are now working to find a permanent solution.
The ESB has apologised for the loss of supply.
While Irish Rail services appear to be unaffected.