In this circuit breaker, sulphur hexaflouride ( SF6 ) gas is used as the arc quenching medium. The sf6 gas is an electro negative gas and has a strong tendency to absorb free electrons. The contacts of the breaker are opened in a high pressure flow of sf6 gas and an arc is struck between them. The conducting free electrons in the arc are rapidly captured by the gas to form relatively immobile negative ions. This loss of conducting electrons in the arc quickly builds up enough insulation strength to extinguish the arc. The sf6 circuit breakers are very effective for high power and high voltage service. Construction: Fig 15 shows the parts of a typical sf6 circuit breaker. It consists of fixed and moving contacts enclosed in a chamber called arc interruption chamber containing sf6 gas. read more

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