The transmission wire came loose from a sleeve securing it at 8:41 a.m. at Barbadoes and Washington streets in Norristown, according to Peco Energy communications manager Michael Wood.
About 8,000 customers in Norristown, East Norriton and West Norriton townships were without power for 50 minutes.
A Peco crew arrived and bypassed the damaged line to restore service by switching over to an automated backup.
Crews cut away the lines and reconfigured the power, Wood said. It was a lot of work in a short period of time.
He said the company would continue to investigate the incident to find out what caused the line to come loose.
A sleeve (securing the wire) heated up and expanded, and the line fell, he said. It will take a while for us to determine why the line broke apart from the sleeve.
The separated wire cut power to substations in Norristown and East Norriton.
Norristown Fire Department Chief Tom ODonnell said firefighters responded to the brick generating station on Schuylkill Avenue and saw a small brush fire; however, local fire personnel waited for an emergency power crew to handle the high-voltage wire.
Its very dangerous for our firefighters, ODonnell said. We stood by until Peco came.
ODonnell said the water plant that serves the area operated on back-up power after the power failure.
Also, several people in the courthouse were reportedly stuck in elevators during the power interruption.
Based in Philadelphia, Peco Energy is an electric and natural gas utility subsidiary of Exelon Corporation that serves 1.6 million electric and 485,000 natural gas customers in southeastern Pennsylvania. This includes about 298,800 customers in Montgomery County.
Pecos installation of computerized distribution automation equipment over the past seven years has enabled the company to improve reliability, efficiency and reduce the duration of outages, Wood said.