Numerical calculation of the end region of large air-cooled turbo-generator under the single-phase earth fault

In view of the appearance of asymmetrical operation condition in the air-cooled turbo-generator, the negative sequent current is caused in stator windings, which may endanger the stability of the turbo-generator. With the 2-D and 3-D direct coupled transient electromagnetic field, the end region electromagnetic field distribution with the rated condition and single-phase earth fault condition is studied. Furthermore, the attenuation law of the axial and radial axial leakage magnetic flux distribution on the generator end core under the single-phase earth fault condition is discovered. The no-load calculated result is finally compared with the measured value; the analysis indicates that the error is within the permitted range of engineering application.