Stability characteristics of turbine generators

THIS paper^∗ reviews and analyzes the steady-state stability characteristics of turbine generators taking the effects of saturation into account. The need for such an analysis has become particularly important with the recent trend toward 3,600-rpm units of large capacity. With the development of such units, the designer is forced in the direction of reducing the weight of the rotor per kilovolt-ampere in order to keep the length and diameter within reasonable limits. However, the reduction in weight of the rotor tends to reduce the short-circuit ratio, which has long been used as a measure of the stability characteristics. The determination of the stability characteristics which may reasonably be expected from a machine, and the validity of short-circuit ratio as a criterion for steady-state stability were considered important enough to justify an analysis. Although the paper deals primarily with the cylindrical-rotor type of generator, the results also apply in general to the salient-pole type.