Reliability Analysis of Fuses in AC Capacitors for HVDC System

Based on the phenomenon of the internal fuse does not operate when the elements of the capacitors used in HVDC AC system break down, this paper analyzes the particularity of the requirements for the internal fuse in HVDC AC system, and summarizes the differences between HVDC AC capacitors and conventional AC capacitors. According to the four parameters of the internal fuses, the characteristics of the internal fuse of AC capacitor used in HVDC system are analyzed, and the problems that should be paid attention to the design of the internal fuses for HVDC are put forward. The low breakdown voltage is also the main factor that causes the fuse failure in the breakdown of capacitor elements. The Weibull model of breakdown under long-term operation is established, and the relationship between breakdown time interval and breakdown probability is analyzed. At 0.707 times the peak voltage, the breakdown probability is negligible. Based on a large amount of analysis of the breakdown voltage of the capacitor's breakdown voltage, the distribution law of the breakdown voltage of the capacitor's breakdown voltage is obtained. The breakdown voltage of the capacitor is almost not lower than the rated voltage of the capacitor, in this case, there will be no internal fuse does not operate when the element breakdown.