The influence of turbine generator rotor damping structure and material on first swing stability

In this paper, we study the influence of rotor damping structure and material on First Swing Stability (FSS) of turbine generator connected to power system after three-phase short circuit. Considering the complex rotor damping structure of turbine generator, we make crucial improvements in finite element discrete strategy reflecting skin effect of eddy current and establish field-circuit-network coupled time-step finite element model. We test this model by the experiment of 7.5 kW model machine. Based on this model, we take a 300 MW turbine generator as an example to study the influence of damping bar, rotor iron core and conductive slot wedge on FSS. We investigate the importance of the rotor damping structure to FSS and find its impact is not negligible. By comparing the FSS limits affected by three components of rotor damping structure respectively, we conclude that the effect of rotor slot wedge and iron core is not linear superposition but Coupling relationship. Since we have several rotor slot wedge materials to choose from and the conductivity of these materials is different, we establish the relationship between FSS limit and conductivity of rotor slot wedge. The result shows that the FSS limit gradually increases as the conductivity of rotor slot wedge changes from σal (conductivity of aluminum alloy) to 0.05σal.