The effects of reclosure operations on turbine-generator shaft torsional oscillation

This paper discusses the mechanism of the turbine-generator shaft torsional oscillations caused by electrical operations. Firstly a shaft global energy function is presented to evaluate the magnitude of shaft torsional oscillation. It indicates that the value of the energy function at the time of performing the last operation is proportional to the torsional oscillation intensity, and this value varies periodically, and is determined by the disturbance torque. Then a shaft partial energy function for a two section equivalent model of the shaft system is constructed to analyse the torsional oscillation amplitude of the most seriously affected shaft section. The auto-reclosure is taken as an example to demonstrate the electrical operations' impacts on shaft torsional oscillation. It is shown that the electrical operation introduces a disturbance in the system, it may enlarge or reduce the oscillation, depending on the magnitude and the applying time of the disturbance. It is shown that the shaft torsional oscillation can be reduced if the last electrical operation is appropriately timed.