Mechanism of Static and Dynamic Voltage Distribution in Environment-Friendly Tank Multibreak Vacuum Circuit Breakers

Environment-friendly tank multibreak vacuum circuit breakers (TMVCBs) are a promising alternative to SF6circuit breakers for high-voltage applications. However, the static and dynamic voltage distribution mechanisms among series-connected breaks in TMVCBs remain insufficiently understood. In this article, the static and dynamic voltage distribution characteristics of environment-friendly TMVCBs were investigated. A finite-element electric field model of environment-friendly TMVCBs was established to obtain the static voltage distribution among breaks, and the nonuniform static voltage distribution is discussed by solving the equivalent capacitance parameter matrix. Subsequently, the modified Langmuir postarc current model was proposed, and the influence of the main shield on the postarc current of vacuum interrupters under a tank structure was analyzed, which demonstrated the dynamic voltage distribution mechanism of TMVCBs. Based on the voltage distribution analysis and a grading capacitor comparison, the interruption tests of a 126-kV environment-friendly TMVCBs were conducted to validate the proposed static and dynamic voltage distribution mechanisms, which also provided the guidance for the grading capacitor design of TMVCBs at ultrahigh voltage and extrahigh voltage levels.