It happened around 3:00 Sunday morning at the Laurel sub-station on the 1000 block of Germantown Avenue.
Neighbors reported seeing a bright flash coming from the area.
Fire crews arrived and found a pair of bolt cutters clamped onto a 2400 volt cable in an apparent attempt to steal it.
Police are checking local hospitals to see if anyone was injured during the theft.
There were no power outages reported with the incident.
PECO advises that people stay away from their power equipment due to the danger risk.
The incident remains under investigation.