METHOD OF STARTING UP TURBINES

摘要

METHOD OF STARTING UP TURBINES At the point of time to when the turbine speed has come up to a first speed N1, a thermal stress expected in the turbine when the speed is increased to a second speed N2 at a rate .alpha.1 is presumed. Thermal stress .theta.s(t)- .theta.sT1 at the point of time to1 for commencing acceleration to the second speed N2 is then obtained, which point of time to1 would never cause the maximum value of the presumed thermal stress to exceed a predetermined limit .theta.s? of the thermal stress when the turbine speed is increased at that rate. Then, a length of time Tw1, referred to as a warming time, is determined which is required for the thermal stress .theta.s(t) to decrease to the level of (.theta.s(t)-.theta.sT1) when the warming is continued after the point of time to. Subsequently, a length of time (N2-N1)/.alpha.1 required for increasing the turbine speed from N1 to N2 at the rate .alpha.1 is calculated. The sum of the warming time Tw and the time required for acceleration is calculated to provide. The lengths of time for starting T1, T2, T3 are found for each of' the acceleration rates .alpha.1, .alpha.2, .alpha.3 in speed. The acceleration of the turbine is commenced at the time and with the rate which in combination provide the smallest sum T of time.