Modelling of thermal phenomena in zinc-oxide surge arresters

The paper presents a thermal model of a surge arrester. This model is relatively complex since the electrical and thermal characteristics of the surge arrester are non linear and the thermal and electrical behaviours are interrelated. The problem has been solved by developing an equivalent electrical model which takes all non-linearities into account, including those due to convection and radiation phenomena. This model is operated on the ASTEC routine. The simulation provides the temperature distribution at different points of the surge arrester and allows many electrical stresses to be dealt with (lightning impulses, steady state, etc.). Many tests have been conducted to check the validity of the model. It has already been widely used by EDF to simulate various conditions of use, as varied as built in surge arresters, pollution stress, etc. These modelling operations have shed light on the influence of axial and radial heat flows and have in particular revealed the influence of the architecture of caps.