Abstract: Abstract:Based on the theory of variable operating conditions of steam turbine, the variation of the thermal economy performance indexes of the steam turbine unit after the HP heater had been cut off was analyzed. According to the amplitude of the index variation, the influence of cutting the HP heater off on economic efficiency was estimated. After the HP heater was cut off, the heat rate of the unit increases obviously, the cycle thermal efficiency of the system decreases, and the gross coal consumption rate increases. For more long time the HP heater is stopped, the caused economic loss is more obvious.

Key words: Keywords:highpressure heater (HP heater);variable operating conditions, thermal economy performance, regenerative heating system