Simulation approaches using the finite-element method (FEM) can be categorized in how they
represent the electrical response of surges arresters. A purely capacitive representation assumes negligible resistive effects in continuous operation, e.g. [6]. It is
the most conservative approximation as it does not take conductive field-grading effects into account. The industry norm [2] recommends a capacitive–resistive representation
of the MO resistor column. This is equivalent to an electroquasistatic (EQS) approach assuming a field-dependent MO conductivity, adopted in [7]–[9]. The strong nonlinearity
and temperature dependence of the electrical characteristic requires, especially for ultrahigh-voltage systems, the analyses of the potential and, additionally, the temperature distribution.
Thus, a heat transfer model for the investigated arrester must be introduced [10], [11]. Station class arresters require substantially more advanced modeling approaches compared with small-sized distribution class arresters considered in the literature so far. This includes current displacement effects, natural convection, and thermal radiation. In this paper, we propose a numerical method enabling transient electroquasistatic-thermal (EQST) station class surge
arrester simulations, including the addressed effects. A multirate time integration technique is developed and implemented in a 2-D in-house code, considering the different electrical and
thermal time scales.