Analysis of the Failure in a Turbine-Generator Shaft

A shaft damage in a power plant in China is investigated in this paper. The opening of two phases of a three-phases circuit due to the incorrect operation of a protection system has been the initial cause for the damage of a turbine-generator (T-G) shaft. The unbalanced fault was analysed by using the method of symmetrical components. Non-synchronously switching process was discovered when the fault of the electromechanical interaction was analysed through the method of the rotating phasor. Using the modal analysis technique, shaft torsional analysis was carried out. And then coupled electromechanical system model was set up using the software PSCAD/EMTDC. The mechanism of the shaft damage was analysed. The present study confirms that non-synchronously switching process can produce high levels of oscillatory torque and it is necessary to avoid having any of the torsional frequencies in the 100 Hz range.