Electric field evaluation on high voltage outdoor insulation by means of finite element method

In this paper the validity of a finite element method based analysis tool, ElecNet software, has been demonstrated to calculate the electric field distribution in high voltage surge arresters. First, a one column porcelain surge arrester model described in IEC 60099-4, Annex L was simulated with ElecNet. The calculation results were then compared with the modeling results published in IEC 60099-4. Generally, the curve of the voltage stress along the arrester column is very similar and the difference in maximum voltage stresses in different units is within 10%. Second, ElecNet was used to calculate the electric field distribution of the three-column surge arrester model with different grading designs. The simulation results suggest that the effect of spacing between the two grading rings on the voltage distribution is very significant. The top unit voltage steadily decreases with the increasing of spacing between the two grading rings. The results also show that grading rings with larger tubing diameter have superior grading properties than grading rings with smaller tubing diameters. However, voltage distribution is not significantly affected by the spacing between the three parallel columns. The simulation also gives an optimized design of grading rings for this three-column surge arrester model which exhibits satisfactory electrical performance.