New submitter wilby writes "Power company Entergy New Orleans says the Super Bowl blackout was caused by device designed to prevent power outages. A device designed to improve the Superdome electrical system reliability instead caused it to shut down dramatically during Super Bowl 47. [The company] said testing traced the source of the problem to an 'electrical relay device' it had installed in December to protect Superdome equipment in case a cable failure occurred between the company's switchgear and the stadium."