Diagnosis of stator winding insulation of large generator

Several new parameters is proposed based on testing results of multistress aging testing of stator bar specimens carried out by using a new developed multistress aging system in our laboratory. The corresponding new parameters, including skewness of partial discharge phase resolved distribution, ultra-wide-frequency characteristic parameters of partial discharge and minimal and average propagation velocities of ultrasonic wave in stator bar insulation, change much more remarkable than the conventional parameters with aging time. Therefore these new parameters could be considered as characteristic parameters for diagnosis of stator insulation of large generators. With these characteristic parameters, authors assessed the insulation condition of actual stator bars replaced from several power plants successfully.