Study of turbine generator shaft torque due to faulty synchronization

Abstract

The generator shaft designers usually consider the shaft torques that develop during short circuit as the most severe case. But, recent studies show that the developed torques due to faulty synchronisation could be greater than that occur during short circuit. This thesis describes a method of simulating faulty synchronisation of a generator with a power system. Previous studies, in almost all cases, neglected the effects of generator saturation in the process of simulation. Even included, the saturation only in the mutual paths of a p;enerator was considered. But since the currents involved during faulty synchronisation become quite large for some synchronising angle, the leakage paths may also saturate. The simulation of faulty synchronisation described in this thesis includes saturation both in the mutual and leakap;e path of a p;enerator. It has been demonstrated that a considerable change in results occur if saturations in a generator are neglected. A comparison between the phenomena of faulty synchronisation and that of short circuit has also been incorporated in the work. For this purpose, the shaft torques developed during fault throwing test under varying conditions are studied. The results reveal that the shaft designers should consider the magnitude of torques developed during faulty synchronisation as one of the design criterion of turbine generator shaft system.