Electrothermal Optimization of Field Grading Systems of Station Class Surge Arresters

摘要

An electrothermal simulation based procedure for the optimization of the field grading systems of station class surge arresters is presented. The main difficulty consists in the numerical solution of the three-dimensional (3-D) field grading system, and the transient electric field problem that arises when a field grading system is introduced. Therefore, we first develop an equivalent axisymmetric arrester model that can reproduce the electric field stress in the resistor column with high accuracy. The model employs a special virtual electrode geometry whose shape and position are determined by a multi-parametric optimization procedure. On the basis thereof, a numerical optimization of the 3-D grading system for an arbitrarily large arrester can be efficiently performed on the basis of transient, electroquasistatic simulations of its axisymmetric equivalent. This procedure is demonstrated for the standard International Electrotechnical Commission (IEC) surge arrester. The detailed electrothermal analysis of this arrester shows that an immense improvement of the field and thermal stress distribution in the resistor column can be obtained.