Numerical investigation of transient potential distribution along stress-grading on stators bars (Roebel Type)

This paper presents the potential distribution along the stress-grading system (Roebel Bar Type) under 50 Hz sinusoidal AC voltage based on the finite element method (FEM). In order to reduce the number of mesh elements and simulation time, a comparative study of two different approaches was examined using commercial software based on the Finite Element Method. The first one is a volume approach which takes into account the thickness of the stress-grading system. The second is the surface approach where the stress-grading system is treated as a specific boundary condition. The investigations have focused on the comparison of the surface potential and electric field distributions along the stress-grading system as well as the number of mesh elements and simulation time using 2D-axisymetric finite element method. The results obtained showed that the surface approach is the best method as it provides the same results as the volume approach with less mesh elements. In addition, a good agreement was found qualitatively as well as quantitatively between numerical and experimental results. Thus, the numerical study provides an alternative to calculate the surface potential distribution along the stress grading with sufficient accuracy using surface approach