Electro-thermal Modeling and Study of MOV Encapsulated with Ceramifiable Silicone Rubber in SPD

As the core component of surge protective device (SPD), the metal oxide varistor (MOV) is widely used for overvoltage protection in the electrical equipment and power systems due to their excellent non-linear characteristics. Currently, MOV is mainly encapsulated with epoxy resin, while it’s flame-retardant and heat-resistant properties are poor. Once a MOV overheats due to overvoltage, the epoxy resin will catch fire causing severe damage. The ceramifiable silicone rubber is a new type of polymer composite material with the excellent flame-retardant properties, which has been applied in fire-retardant coatings and fire resistant cables. This material also has good application prospects in MOV. In this paper, the electro-thermal model of MOV with encapsulation flame-retardant materials was established by COMSOL Multiphysics, and the accuracy of the model was verified by the temporary overvoltage (TOV) experiment. Based on this model, four sets of flame-retardant material parameters were selected within a suitable range of parameters. Comparing the temperature rise characteristics of MOV with different parameters, the parameter which can make the lowest temperature rise inside the MOV model is selected. The simulation results can provide a reference for the application of flame-retardant material on MOV.