Study on Dielectric Recovery Characteristics of High Voltage SF6Circuit Breaker

Abstract

With the rapid development of UHV and smart grid, the breaking condition of SF6 circuit breaker becomes more complicated. Along with the increasing of recovery voltage after arc extinguishing, breaking failures caused by the re-strike happened frequently. A two-temperature model about nonequilibrium SF6 arc plasma was built according to basic equations of fluid mechanics and gas equation of state, forming a numerical computing method for the whole breaking process in SF6 circuit breaker. The whole breaking process in condition of no-load and breaking 1600A capacitive current were numerical calculated to obtain dielectric breakdown voltage of SF6. The accuracy and reliability of the numerical calculation method were verified compared with the experimental results of dynamic breakdown voltage of SF6 gas between arcing contacts. The thermal dielectric recovery characteristics of SF6 circuit breaker was analyzed in the condition of breaking 1600A capacity current and short arcing time. Influences of breaking phase angels, velocity and gas pressure were discussed at the same time. The optimization operating strategy of circuit breaker was given to improve the electrical life and reliability of circuit breaker.