Analytical prediction of transient breakdown characteristics of SF/sub 6/ gas circuit breakers

A study was conducted to estimate transient breakdown voltages (V/sub BD/s) between contacts of a puffer-type SF/sub 6/ gas circuit breaker. When contacts are opening, compressed gas is blasted between them by an insulating nozzle. The gas pressure fluctuates greatly in the contact region. The authors suggest that this pressure fluctuation causes transient V/sub BD/s. It is demonstrated that very accurate transient V/sub BD/ characteristics can be calculated by combining the gas flow and electric field analyses and breakdown probability. The numerically calculated transient V/sub BD/ characteristics agree fairly well with the transient recovery voltages during the capacitive current interruption.<
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