Withstanding capability and aging mechanism of metal-oxide varistors under DC temporary overvoltage

With the development of low-voltage DC (LVDC) application scenarios, the application of Surge protective devices (SPDs) for the protection of LVDC systems from overvoltage requires urgent attention. Temporary overvoltage (TOV) withstanding capability is a critical parameter so that studying the withstanding capability and aging mechanism of metal-oxide varistor (MOV) which serves as the core component of SPD is significantly important. The numerical model of MOV is established in this paper to study the TOV performance in DC systems with different voltage levels. The 2D Voronoi network is employed to depict the microstructure of MOV. After validating the reliability of the microstructure model, the electrothermal characteristics and capability of the MOV to withstand TOV in LVDC systems at various voltage levels are investigated. The parameters for the DC TOV are obtained from the latest committee draft of IEC 61643-41. The aging mechanism based on double Schottky Barrier theory under DC TOV is discussed in detail, which can explain the initial rise followed by a subsequent decline in varistor voltage. The Voltage-Temperature-Time (V-T-t) curve of MOV is proposed for the first time which serves as a valuable theoretical reference for the development of overcurrent and overheat protection of DC SPD.