File:Electricity grid simple- North America.svg|thumb|380px|right|Simplified diagram of AC electricity grid from generation stations to consumers in North Americarect 2 243 235 438 Power stationrect 276 317 412 556 Transformerrect 412 121 781 400 Electric power transmissionrect 800 0 980 165 Transformerdesc bottom-left

A transmission system operator