Four major factors that affect the turbine heat rate during the unit sliding pressure operation were presented

like the main steam pressure

high pressure cylinder efficiency

inlet steam flow of the feedwater pump steam turbine

and enthalpy rise of the feedwater pump.An ultra supercritical 1 000MW unit and a supercritical 600MW unit were taking as the example to conduct the calculation.The variation of the high cylinder efficiency against the main steam pressure was considered as the basic reason that affects the optimal sliding pressure point of the main steam. Moreover

the sliding pressure operation optimization test was carried out under different steam distribution modes.The results show that

the optimal main steam pressure point of the throttlegoverned steam turbine appeared when the steam turbine regulating valve was fully open.The high pressure cylinder efficiency of the nozzle-governed steam turbine showed a nonlinear relationship with the main steam pressure

so the optimal main steam pressure point of this turbine appeared at the flex point of the high pressure cylinder efficiency.After the preliminary experimental results were obtained

the load variation test should be performed to find the final operation fix-sliding pressure curve.