T
The first Sulfur hexafluoride (sf6) gas industrial developments
were in the medium voltage range. This equipment confirmed the advantages of a technique that
uses sf6 at a low-pressure level concurrently with the auto-pneumatic blast system to interrupt
the arc that was called later puffer.
High-voltage sf6 circuit breakers with self-blast interrupters have found worldwide acceptance
because their high current interrupting capability is obtained with a low operating energy
that can be provided by low-cost, spring-operated mechanisms. The low-operating energy required
reduces the stress and wear of the mechanical components and significantly improves the
overall reliability of the circuit breaker. This switching principle was first introduced in the highvoltage
area about 20 years ago, starting with the voltage level of 72.5 kV. Today this technique
is available up to 800 kV. Furthermore it is used for generator circuit breaker applications with
short circuit currents of 63 kA and above.
Service experience shows that when the sf6circuit breakers of the self-blast technology were
first designed, the expectations of the designers had been fulfilled completely with respect to
reliability and day-to-day operation.