Study of the Impact of Electrode Structure on the Overheat Protection of SPD Based on Multiphysics Field Simulation

Surge Protective Device (SPD) is utilized to protect the electric circuits from overvoltage, typically containing a metal oxide varistor (MOV) inside. As the MOV deteriorates gradually, the risk of the SPD catching fire and burning also increases. The metal electrode of the SPD internal disconnector can conduct the heat generated by the MOV. When the solder on the electrode melts, the MOV with abnormal heating will be disconnected from the power electric circuit. The metal electrode plays a vital role in temperature conduction. Different electrode structures have significant influence on the thermal protection performance of the SPD. This paper analyzes the structure of two types of electrodes for the MOV inside SPD. Firstly, the models of the MOV and its electrodes are built. Then the temperature distribution of the electrodes under both DC and AC conditions is individually calculated using the finite element method (FEM). The accuracy of the simulation is verified through DC thermal stability experiments. The influence of different electrodes on MOV temperature and heat protection is analyzed. Finally, the recommendations for solder selection are provided. The simulation results have a profound influence on guiding the electrode design within the SPD.