Investigation of Thermal Stability for a Station Class Surge Arrester

The protection of power transmission systems against voltage surges is based on station class arresters. An important design criterion is to achieve thermal stability after operating duties. In order to study the transient behavior of arresters, a fully coupled electroquasi-static-thermal finite-element-method simulation approach is introduced. The procedure includes an efficient multirate time integration scheme. Furthermore, for station class arresters, dynamic thermal processes, such as natural convection and thermal radiation in the air gap, are considered. The numerical approach is applied in the simulation of an ungraded 550-kV-system arrester in continuous operation as well as under voltages surges. In order to assess the thermal stability properties of the arrester, an effective cooling rate parameter is introduced. Different impulse injection scenarios, similar to the IEC 60099-4 operating duty test, are investigated.