Steam turbine generator shaft torque transients: a comparison of simulated and test results

If the electrical system of a turbine generator is subjected to a fault or disturbance condition, large mechanical torques may be induced in the turbine shafts. The computer prediction of such torsional behaviour has become an important feature of system design and appraisal. Simulation results are presented for two different operating conditions: malsynchronisation and load rejection. Comparisons of these computer predictions and actual measured test results are made for the torque transients on two shafts of the turbine generator. Good correlation is obtained if electrical and mechanical damping data is chosen carefully. The computer model is shown to behave satisfactorily with respect to the predicted torsional frequencies, peak to peak torque amplitudes and rate of decay of the transients. The variations of the rate of damping for the different disturbances are also discussed