Simulation Analysis of Critical Parameters for Thermal Stability of Surge Arresters

Ensuring thermal stability is an important aspect of an arrester design process. In this paper, the thermal stability of station class surge arresters is investigated using a coupled electrothermal numerical model. An ungraded 550-kV-station class arrester model is successfully validated against temperature measurements in power grid operation. The arrester cooling rate is introduced to determine the thermal stability threshold. Thermally stable and unstable scenarios are compared. The influence of selected arrester design parameters on the stability threshold is analyzed. It is shown that an improved heat transfer in the arrester air gap increases the thermal stability threshold significantly. Additionally, the nonlinear zinc oxide material characteristics influence the thermal stability threshold strongly. Furthermore, a thermal stability prediction approach based on few, computationally less expensive simulations is proposed. Finally, the results are confirmed for an arrester model that is equipped with a field-grading system. The paper shows that the presented field simulation approach can be reliably used to determine the stability threshold of an arrester, thus, reducing the need for costly laboratory tests.