Analysis of Torsional Stress and Fatigue of Turbine-Generator Shafts during Islanding

Power system disturbances induce transient torques, which may overstress turbine-generator shafts and shorten their fatigue life. This work analyses torsional stress and fatigue life loss of turbine generators subsequent to unintentional islanding in a network. The analysis was conducted using time domain simulation with PSCAD and an analytical method for fatigue estimate of turbine-generator shafts. Islanding termination and operation after islanding termination are identified as the two events that pose the biggest threats to shaft fatigue life. It is shown that the risk of early shaft damage is averted when the turbine-generator islands on a local load whose size is bigger than a critical value.