The cause of a power outage that brought the Super Bowl to a halt for more than a half-hour is being blamed on a faulty device that Entergy New Orleans installed to prevent electric cables leading to the stadium from failing. A relay, or electrically operated switch, located in a brick structure called the "vault" outside the Mercedes-Benz Superdome malfunctioned and opened, causing a partial outage in the 73,000-seat stadium, Entergy said.