Under the combined action of steam flow disturbance and unbalanced centrifugal force

unstable synchronous vibration is easy to occur during the operation of high and intermediate pressure rotors of high parameter steam turbines. Through theoretical derivation of the vibration control equation of rotor bearing system

the influence mechanism of steam flow disturbance on the unbalanced response of steam turbine rotor is analyzed

and then the fault diagnosis and treatment methods of unstable synchronous vibration are summarized. The vibration treatment cases of two 300 MW-level steam turbine generator units are introduced in detail

which verifies the proposed treatment strategy. The field treatment of such vibration faults can be carried out by enhancing system stability

alleviating steam flow disturbance and reducing mass unbalance. When the measures such as adjusting the bearing elevation and changing the opening sequence of high-pressure regulating valve are invalid

the unstable synchronous vibration of high and intermediate pressure rotor can be reduced through on-site precision dynamic balance.