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Surge arresters of station class are equipped with field grading elements that break the rotational symmetry of the arrester body. To avoid a computationally expensive full three‐dimensional (3D) simulation, a quasi‐3D simulation procedure is presented to study graded arresters. The method employs a hybrid discretization combining a two‐dimensional (2D) axisymmetric finite element (FE) method in axial and radial direction with a spectral element method in terms of trigonometric functions in azimuthal direction. Furthermore, the asymmetric boundary conditions associated with the support rods are taken into account by collocation in a saddle‐point system of equations. The method is validated and compared with a standard 3D FE simulation of a test problem. It is, subsequently, applied to study the electric field distribution of a graded station class surge arrester.

Extruded high-voltage direct current cable systems transmit electric power over long distances. Numerical field simulation can provide access to the internal electrothermal behavior of cable joints, which interconnect cable sections. However, coupled nonlinear electrothermal field simulations are still a challenge. In this work, a robust numerical solution approach is implemented and validated. This approach allows for efficient parameter studies of resistively graded high-voltage direct current cable joint designs. It is assessed how the dielectric stress distribution between the conductor connection and the grounded cable sheath is influenced by nonlinear field and temperature dependent electric conductivity of the field grading material. Optimal field grading material parameters, which fulfill the field grading and power loss requirements, are suggested based on the simulation studies.

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