Influence of high frequencies and harmonic distorted voltages on refractive field grading for medium voltage cable accessories

This contribution investigates the influence of high frequencies as well as harmonics on refractive field grading material for medium voltage cable accessories. The dielectric losses of the refractive field grading material are first measured and evaluated to determine the influence of harmonics. Then, a model of a medium voltage cable joint incorporating the test sample as field grading material is computed using Finite Element Method (FEM). Using a Multiphysics approach, the electrothermal behaviour of the model is evaluated under the influence of high frequencies and harmonics. Preliminary results show that high frequencies do not significantly increase the electric field strength on the interface. Additionally, high frequencies up to 2 kHz also d o not result in any significant temperature increase in the field grading material. Similarly, under harmonics, the increase in the electric field strength remains negligible.