Police officers were called to the Oldbury substation, off Churchbridge in Oldbury, following reports at about 8.20am on Thursday that someone was spotted at the site.
National Grid said a total of 49,090 houses in the Dudley area were left without power for about 20 minutes as the electricity supply had to be turned off for the safety of the individual.
“At 8.23am we were informed that a member of the public had climbed a structure at Oldbury Substation in the West Midlands", National Grid said.
"For the safety of the individual, electricity supply was turned off resulting in 49,090 homes in the Dudley area being without power for around 20 minutes.
"The police attended, the individual is no longer on site and power supplies are now fully restored.”