Numerical Study on Decaying Arc under Free recovery Condition in CO_2/SF_6 Gas Mixture of Various Mixing Ratio

摘要

The present report describes numerical study results of arc behavior in various mixture ratio of CO_2/SF_6 gas mixture under arc decay process in a nozzle space on the assumption of local thermodynamic equilibrium condition. The CO_2/SF_6 gas mixture is considered as a candidate alternative for pure SF_6 gas in a gas circuit breaker. The present work first calculated the equilibrium compositions of the gas mixtures at 1 atm. Furthermore, their thermodynamic and transport properties were computed with the calculated equilibrium compositions and a set of collision cross sections. Using these properties, the arc temperature and gas flow fields were calculated for free recovery condition from 50 A to 0 A. Results showed that CO_2/SF_6 arc showed a faster temperature decay and a faster arc resistance rise than 100% CO_2 arc.