Turbine

Turbine runback refers to a controls condition which causes a program to automatically run the turbine back (by closing down on turbine valves) to a predetermined setpoint (based on available equipment) when a piece of equipment trips off. An example of how it works is... a coal pulverizer in service is rated at 100 MW per this scheme. Let's say we have 4 coal pulverizers in service and we have 350 MW being generated. One of the coal pulverizers trips which leaves us with three pulverizers running which allows for 300 MW of power generation based on this controls scheme. When this happens, the controls scheme (program) automatically goes into a runback condition which acts very fast (by design) to pinch the turbine valves back to 300 MW condition. During this time, the feeders supplying coal to the pulverizers would have runout (going to 100% capacity) until the turbine valves were able to pinch down enough to bring the conditions back in a stable operating condition (under control).