Analysis of saturated synchronous reactances of large turbine generator by considering cross-magnetizing reactances using finite elements

This paper describes a method to calculate saturated reactances of synchronous machines at various loads under steady-state operation by considering influence of cross-magnetizing phenomenon between d- and q-axis circuits. In the method, mutual reactances x_dq due to the cross-magnetizing phenomenon can be calculated on the basis of two-dimensional magnetic field analysis. The validity of analysis is shown by good agreement between measured and calculated field current values of a 592 MVA turbine generator at various loads. It is clear that quantitative accuracy requires the magnetic coupling between d- and q-axis circuits be considered. Subsequently, steady-state reactances at various loads are analyzed by considering mutual reactances x_dq due to cross-magnetizing phenomenon. The relation between the load angle δ and mutual reactance x_dq is clarified, and the difference between equivalent synchronous reactances that are obtained by considering x_dq and conventional defined synchronous reactances that do not consider x_dq is shown numerically