Loss Distribution in Stator End Region of Turbo-generators During Asynchronous Operation after Loss of Field

The asynchronous operation of a turbo-generator after the loss of field can avoid large-scale blackout and improve the reliability of the power systems. However, the turbo-generator would absorb large reactive power during asynchronous operation, and the increased stator currents can result in the increase of the leakage flux and loss in the end region of the turbo-generator. In order to study the losses of the end structural components during asynchronous operation, this paper presents a method combining the 2-D field-circuit coupled time-stepping finite element model (FCCTSFEM) with the 3-D transient electromagnetic field in the end region of the turbo-generator. The dynamic responses of the turbo-generator after loss of field are calculated by FCCTSFEM, and 3-D transient electromagnetic field and the losses in the end region of the turbo-generator are calculated based on the results of the dynamic response. From the detailed performance evaluations by the 3-D finite-element analysis, the flux density and loss distributions of the end structural components are compared. The regions with the maximum loss in the end structural components are found. The losses of the end structural components affected by the different materials of the metal shield are studied. The results could provide a theoretical basis for improving the asynchronous operating ability of the turbo-generator.