The acceleration trend relay for generator stabilization at Colstrip

This paper describes the development and implementation of an acceleration trend relay (ATR) which is in operation for generator stabilization at Colstrip, Montana. The ATR is unique in that it uses only local signals at the remote generation site to selectively trip generating units based on a real-time assessment of the severity of a disturbance. Local inputs to the ATR are generator shaft speed from magnetic pickups and generator electric power from a watt/VAr transducer. Based on these inputs the appropriate amount of generation to trip is determined in order to maintain stability of the remaining system. Details on how the device works, how trip decisions are arrived at, and operating experience with the device are presented.