COLUMBUS, OHIO ? In the hours before the nation’s worst blackout, several transmission lines in Ohio were carrying massive amounts of power “well above” emergency summer standards before automatically shutting down, a company that owns the lines said Friday.

American Electric Power owns or co-owns the power lines with FirstEnergy Corp., which is at the center of a U.S.-Canada blackout investigation. The company released the information with a timeline but didn’t offer any conclusions about the cause of the outage.

AEP said it avoided potential widespread outages in its area — only 14,000 of its customers lost power — because control systems detected “abnormal operating conditions” and tripped — or disconnected — from linked FirstEnergy lines.

“It is likely that the automated controls tripped some transmission lines moments before they would have burned down because of extremely high power flows out of our system,” said Henry Rayne, AEP’s executive vice president.

The region where investigators suspect the eight-state blackout began Aug. 14 had become a black hole, sucking electricity from generators and threatening to burn transmission lines because of the overload, power company officials said.

“Those lines were never designed for that tremendous shot,” said Joseph Welch of International Transmission Co. of Ann Arbor, Mich.