Comparison between 2D and 3D modeling of an EHV post station insulator equipped with a grading ring

This paper presents a comparative study between 2D axisymmetric and 3D modeling of an EHV post station insulator equipped with a standard corona ring. The simulations were performed using the FEM commercial software Comsol Multiphysics® and particular attention was dedicated to the presence of two anchors or brackets of the grading ring. These anchors were taken into account in both 2D axisymmetric and 3D models in order to study their influence on the E-field distribution and magnitude closed to the HV insulator. The results obtained highlights the fact that the metallic anchors can have a notable influence on the E-field strength when 3D modeling was used. However, this influence is only limited within the vicinity of the HV electrode and does not extend to the entire potential and E-field distribution along the EHV insulator. The metal anchor tends to decrease the E-field strength closed to the HV electrode, providing a better grading effect. However, as the position is moving away from the metal anchor, the 3D and 2D axisymmetric E-field again becomes the same. This demonstrated that it is not necessary to take into account the metal anchors when 3D modeling of outdoor insulator equipped with grading ring has to be performed. Moreover, the results demonstrated that the creation of a complete electrical link between the grading ring and the HV electrode could result in a better improvement of the E-field strength reduction in the vicinity of the HV electrode.