Evaluation technique of turbine shaft fatigue in private-generation systems using consumption rate of shaft life cycle

Under the action of disturbances in power systems, the turbine-generator shaft is subjected to mechanical stress caused by severe torsional torques. Shaft torque is proportional to the shaft twist, which is caused by the angle difference between both ends. However, observing the angle difference in an actual generation system is difficult technically. On the other hand, measuring the rotational speed of the shaft ends is relatively easy. Then if the shaft torque could be estimated effectively, it would be used in order to control the rotational speed for shaft torque reduction.