Thermal Instability Analysis of Station Class Surge Arresters Based on Electrothermal Finite Element Simulation

The phenomenon of thermal instability is an important practical problem of station class surge arresters. This effect may occur after single or repetitive energy impulse injections to an arrester connected to the power grid. Thermal stability of full scale arresters cannot be investigated in the laboratory. Finite element simulation provides detailed insight to this complex electrothermally coupled problem. Therefore, an ungraded arrester is modeled including all relevant electrothermal physics. After the model is validated, various thermally stable and unstable scenarios are investigated. A criterion that assesses and predicts thermal instability of an arrester is determined. Furthermore, selected model parameters that increase the thermal stability limit are identified in order to optimize future arrester designs.