Homes and businesses in the east of the city suffered a dip in power after a fault in a 33,000-volt cable last night.
Thousands of homes and businesses, from the Highfields district to Hamilton saw a widespread dip in supply after the fault in the underground cable shortly before 9.30pm.
Further dips in supply were reported about an hour later as engineers worked to correct the fault.
A spokesman for Western Power Distribution said: "There was no loss of supply, but people would have noticed their lights dip down, with the first reports initially at 9.20pm.
"There were two further depressions in the system at around 10.30pm.If factories had machines running they might have been affected, but it would just have been the case of switching back on.
"One company rang in to say it had lost supplies to its motors and had to re-set the production line."