Super Bowl Blackout Caused By Defective Protective Relay

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."

Comments

Re:The TL;DR

[cblguy2]

Circuit breaker was not "miscalibrated". The protective relay (which is separate from a breaker) possibly had a setting in it that was too low. Protective relay settings are based on time curves (which are plotted on logarithmic paper). For, say, 300 amps, it trips after 10s or 100s of seconds of continuous operation past the setting. For 10,000 amps, it may after .03 seconds (or you may have an instantaneous setting, or a definite time delay based on cycles). That kind of curve. If the load was drawing so much current, for so long of time, then yes, it will send a command for the circuit breaker to trip. Anyhow, it's easy to screw up a protective relay setting - and yes, I've done it. That's why relay settings are always checked by a second engineer as well, just to make sure you didn't miss something. IAAPE (I am a protection engineer, and a P.E.), though we don't use S&C relays (Schweitzer here).