The influence of the damper cage on the waveforms and subtransient reactances calculated at a two-phase short circuit of a large hydrogenerator

Influence of induced currents in conductive parts of the large hydrogenerator rotor on the waveforms occurring in the two-phase short circuit of the stator winding is investigated in the paper. The waveforms have been calculated using the finite element method with the use of a two-dimensional field-circuit hydrogenerator model. This model has been verified on the basis of the characteristics of idle run and three-phase short circuit calculated and measured in the power plant. Calculations of the waveforms at the two-phase short circuit have been carried out for various structural versions of the damper squirrel-cage, differing in the location of the eddy currents flow and the intensity of their interaction with the magnetic field. The calculated harmonic spectra of waveforms at two-phase short circuit have been used to calculate the subtransient reactances of the hydrogenerator. Comparisons and discussion of the achieved results are presented.