Multi-rate time integration for coupled electrical and thermal modeling of surge arresters

A coupled electro-quasistatic-thermal (EQST) method for 2-Dimensional-Finite-Element-Method (2D-FEM) simulations of transient arrester behavior is presented. Due to the extremely short time scales associated with the nonlinear electrical characteristic of the MO resistor material, a multi-rate time integration technique is employed. The heat transfer in the annular cylindrical air gap between the metal-oxide (MO) resistor stack and the porcelain arrester housing involves radiation and natural convection. Hereby, a nonlinear equivalent material model for the heat transfer in the air gap is developed. Simulations for a station class arrester in continuous operation are carried out and validated against measurements.