Officials of Entergy New Orleans say the device, called a relay, had been installed to protect the stadium from a cable failure between the company's incoming power line and lines that run into the stadium.
Company officials said the device performed without problem during January's Sugar Bowl and other earlier events.
They said the device has been removed and replacement equipment will be installed.
"While some further analysis remains, we believe we have identified and remedied the cause of the power outage and regret the interruption that occurred during what was a showcase event for the city and state," said Charles Rice, president and chief executive officer of Entergy New Orleans.
The power failure cut lights to about half of the stadium for 34 minutes, halting play between the Baltimore Ravens and San Francisco 49ers.