When determining the POwer variation due to the back pressure change of the condensing turbines
the change of the unit capacity is calculatedwhen the steam condition changed or the thermal system is in diferent type
which is studied on the basis of the theory of the tUrbine and thermalsystem Performance in variable steam conditions. When determining the POwer variation due to the back pressure change of the condensing turbinesthe unit capacity change is calculated under various loads on basis of the theory of the turbine and thermal system Performance in varied steam con-ditions
with consideration of Performance variation of thermal system. A sample method is established for the economic performance of the unit.