A power blackout hit central Sydney on Tuesday for the third time in a month.
EnergyAustralia said a cable failure cut power to about 30,000 businesses and homes.
Trading on the Australian stock exchange was not affected. Trains also continued running in and out of the city.
A severe power blackout caused peak-hour traffic jams in downtown Sydney at the end of last month. Dozens of people were stranded in lifts.
Days later, a second blackout cut power to 50,000 customers for an hour, stopping 50 sets of traffic lights, closing a tunnel under Sydney Harbour and again trapping people in lifts.
