Abstract <p>One of the important problems solved in planning electric-power-system (EPS) operation consists in the assessment of its transient stability. Using incorrect parameters for EPS element models, in particular synchronous generators (SGs), leads to errors in determining the operating conditions of power systems and, therefore, to a decrease in the reliability of EPS operation. This work is aimed at studying the effect of errors in SG model parameters on the results of transient stability assessment based on computational simulation experiments in the environment of a MATLAB/Simulink software package. Two approaches have been considered; in each case, the EPS transient stability assessment has been performed almost automatically, and quantitative parameters have been computed for analyzing the impact of SG model parameter deviations on EPS transient stability. The deviations in the parameters of SG models from their reference values exert a significant effect on the calculation results obtained for the maximum lifetime of a short-circuit under the condition of DS retention, regardless of the SG model; the calculation errors can amount up to 100%. The deviations of the parameters of SG models from the reference values affect the calculation results for the maximum load of the generating equipment in the initial pre-emergency mode under the condition of dynamic stability (DS) retention at a preset disturbing impact. In the case of conducted computational experiments, the scatter in the values of the maximum load of the generator under study amounts to about 20%.</p>