抄録
We have calculated the dielectric breakdown field strength of SF6 gas between 300 K and 3000 K and combined these data with gas flow simulations and electric field strength calculations in a 300 kV Gas Circuit Breaker geometry. The hot gas exhausted after heavy current interruption is exposed to high electric field strengths which must be controlled in order to avoid dielectric breakdown at certain places in the circuit breaker. The decisive factor whether dielectric breakdown occurs or not is the dielectric breakdown field strength of the hot gas which depends on the local temperature and density. Temperature and density will be calculated by a numerical gas flow simulation and will be related to our calculated values of dielectric breakdown field strength of hot SF6 gas. By comparing these results to electric field strength calculations of the same geometry we will be able to locate the critical spots in the circuit breaker. As a result it is found that dielectric insulation seems to be assured in the Gas Circuit Breaker in question, however, non-uniform fields might disturb this conclusion.
