Against the characteristics of a Siemens 660MW unit's shaft sealing system which is not equipped with spray attemperator and redundant steam supply

a novel control strategy was put forward.On the basis of coupling pressure regulation with steam supply valve and overflow valve as actuators

the control strategy adopted steam desuperheating instead of spray desuperheating

which achieved automatic control of shaft sealing steam parameters under each working condition.By comparison with the original control strategy

some suggestions were proposed against the defects of existing Siemens control strategy.