EFFECTS OF CONTROLLING THE SEQUENTIAL INTERRUPTION AND RECLOSING OF SYSTEM FAULTS ON TURBINE-GENERATOR SHAFT TORSIONAL TORQUES

Abstract

Over the past decade, there has been considerable interest in predicting the effect of electrical disturbances on the shaft stresses of large turbine-generators. These disturbances include breaker operations associated with synchronizing, line switching, fault clearing and reclosing. All such events induce high torsional torques on the turbine-generator shafts. Depending on many factors, the stresses induced by these torques may exceed the endurance limit of the turbine-generator shafts and, hence, cause shaft fatigue. Comperhensive studies have been reported in this thesis to explain the nature of the interaction between the turbine-generator shaft systems and the electrical disturbances in the transmission network and to search for practical and economical solutions to the problems associated with it. In particular, attention is focused on the problem of the high torsional torques induced in the turbine-generator shaft systems during clearing and reclosing of multi-phase system faults. For this purpose, theoretical studies of the phenomenon using a detailed benchmark model of one-machine infinite bus system have been carried out. The thesis presents a detailed study to investigate the possibility of reducing the high torsional torques induced in the turbine-generator shafts during clearing close-in multiphase system faults by controlling the sequential interruption of such faults. Furthermore, the thesis proposes an adaptive reclosing technique to reduce the high torsional torques to which the turbine-generator shafts might be subjected during highspeed reclosing of system faults. The results of these investigations have demonstrated the effectiveness of these techniques in reducing the high torsional torques induced in the turbine-generator shafts during clearing and reclosing of system faults.