Thermal behaviour analysis in a porcelain-housed ZnO surge arrester by computer simulations and thermography

In this article, an analysis of heat transfer in a porcelain-housed ZnO surge arrester is presented. Due to the fact that ZnO-based surge arresters are key components for protection and reliability of electrical systems, it is necessary to seek techniques to assure correct assessment. In porcelain-housed arresters, the air gap leads to an increased thermal resistance between the ambient and the varistor column. Consequently, a thermal analysis must consider convection and radiation heat transfer mechanisms, besides heat conduction. This study proposes the use of computational simulations in combination with thermography as a tool for a temperature-based estimation of the varistor state. For the analysis, temperature rise tests were performed in a 69-kV ceramic-housed arrester to measure material emissivity and produce data to fit the simulated response. Furthermore, the thermal response of the surge arresters subject to an impulsive energy input was evaluated. The simulations allow to relate varistors temperature and housing temperature with regard to a specified amount of dissipated power. The obtained results show that the used technique can be an effective method for arrester monitoring and may allow to define assessing criteria for a porcelain-housed arrester based on housing temperature measurements.