Parametric Study and Improvement of Anti-Corona Structure in Stator Bar End Based on Finite Element Analysis

Voltage withstand tests on stator bars can cause destructive phenomena such as thermal breakdown and flashover discharge on the surface of the anti-corona layer. This study optimizes the anti-corona structure at a stator bar’s end to prevent such failures using a 120 MW water-cooled turbogenerator with a rated voltage of 15.75 kV. For a well-designed anti-corona system, the maximum potential gradient of the stator bar should be lower than the discharge intensity of air corona. In our design, the electric field intensity is maintained below 3.1 kV/cm, and the maximum surface loss in the anti-corona layer is limited to less than 0.6 W/cm2. Additionally, the terminal voltage is kept lower than that of flashover voltage at rated conditions. Furthermore, the length of the anti-corona layer should be minimized. The optimization process involves determining the rotation angle of the stator bar, calculating the total length of the anti-corona layer, and analyzing the electric field and loss in the layer at different lengths. The results demonstrate that the optimized anti-corona design effectively reduces the risk of flashover and thermal failure, ensuring stable operation under rated conditions. This manuscript belongs to purely computational experiments. At present, the electrical machinery with 120 MW rated power grade is put into operation steadily. There is a growing requirement for anti-corona. In this manuscript, computing method is used to assist the anti-corona structure design. The electrical machinery insulation is improved by better anti-corona materials. Therefore, the service life of electrical machinery can be prolonged, which is significant in engineering.