On the Accuracy of the Surface Voltage Gradient Calculation on Round Conductors Using Standard Formulas

• The strength of the surface voltage gradient greatly determines corona occurrence. • Some standards show formulas to infer the surface voltage gradient of round busbars. • This paper compares the accuracy of such simplified formulas against FEM simulations. • This paper shows that these simplified formulas have certain limitations. • Such limitations can be overcome using fast two-dimensional FEM simulations. The surface voltage gradient (SVG) is probably the most important factor in determining the likelihood of a corona discharge occurring on the surface of round conductors or tubular substation busbars. There are several standards that propose simple formulas to determine the SVG of various configurations involving round conductors. However, such formulas are not exact, so this paper analyzes their accuracy by comparing the results provided by such formulas with the results obtained by Finite Element Method (FEM) models. This comparison highlights the difficulty in accurately calculating the average and maximum SVG of round conductors and tubular busbars using simple formulas.