Evaluation of Weakening Effect of Stator Parallel Branch Circuit on Main Field Asymmetry

The short circuit between turns of the rotor winding is a weak characteristic electrical fault of the turbine generator, which makes the fault detection difficult. This paper investigates the weakening effect of the circulating magnetic field inside the parallel branch of the stator winding of a turbine generator on the asymmetric magnetic field generated by the rotor winding turn-to-turn short-circuit, derives the expression of the excitation magnetic field under the fault condition, obtains the expression of the circulating current of the parallel branch of the stator winding and the expression of the magnetic field generated by the circulating current, and finds out the offsetting effect of the circulating field on the original asymmetric magnetic field. A 300MW steam turbine generator is used as an example to carry out finite element simulation, which proves the weakening effect of the parallel branch structure of the stator winding on the short-circuit fault characteristics of the rotor winding, and the research conclusion is helpful to analyze the external appearance and causes of the short-circuit fault characteristics between turns of the rotor winding, and also provides theoretical support for the feature extraction in the fault diagnosis stage.