A faulty sensor was likely to blame for the hour-long power outage on Friday morning, according to Public Utilities Director Dan Winters. 

The recently installed CAT C280 engine had a ‘high crank case pressure’ alarm that tripped the system, shutting down the engine.  The total grid load at that point exceeded the generating capacity of the two smaller CAT engines, causing them to shut down as well.

Winters says that a whole-system shutdown like that takes a while to deal with because it involves restarting the entire grid, section by section.  He says most power outages are triggered at the breakers and don’t involve engine shutdown, so can be fixed relatively quickly.  The last time there was a whole-system outage was when the two Wartsila engines were installed in early 2011.