A power cut on February 20 left hundreds of homes and businesses in west Oxford without electricity.
Southern Electric spokesman Susan Scobie said the blackout, at 11.40am, affected 528 customers in Osney, Botley and North Hinksey.
She said: "We don't know cause of the power cut yet. We are investigating.
"We are giving customers the message power should be back on at 2pm or before."
Thames Trains spokesman Jonathan Radley said business and services at Oxford railway station were not affected.
The power cut came less than 30 minutes after the Queen and Prince Philip arrived at the station.
Mr Radley said: "The lights did flicker for a moment, but then the power came back on again."
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