Influence of synchronous-machine-rotor angular-velocity variations in transient-stability studies

A modified method of power-system transient-stability assessment is presented and shows that, although they were previously considered to be negligible, the inclusion of the effects of variations of rotor angular velocities can have an influence on the stability as great as that of other factors (such as the voltage regulator saturation, flux decay and machine damping) which it is already considered worthwhile to incorporate in system calculations. The present study, although limited to treating synchronous machines as being frequency-dependent, can be extended to other power-system units, and it points to the need for a reassessment of the role of transient frequency deviations in transient-stability studies.