Development of The SF6 Circuit Breakers

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Development of The SF6 Circuit Breakers

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Development of The SF6 Circuit Breakers


Three types of SF6 Breakers

Two Pressure Gas Breakers

Puffer Gas Breakers

Arc Assisted / Self Blast Puffer Gas Breakers


Two Pressure Gas Breakers

First Developed in 1960s

Resembled double pressure air blast breakers

Have a sealed gas system with a gas compressor

Usually have an air compressor for the operating mechanism

SF6 gas is stored at high pressure (250 psi) in storage tanks.


Two Pressure Gas Breakers

Gas storage tanks require heaters and insulation due to the fact SF6 liquefies at a relative high temperature

Breakers may be live tank or dead tank

Breakers may gang operated or independent pole operated

Breakers require the use of a blast valve


Two Pressure Gas Breakers

Two pressure gas breakers are mechanically very complex.

Two pressure gas breakers require significant maintenance

There is high pressure gas (250psi) as well as low pressure gas (85psi)



Westinghouse SFA Two Pressure Interrupter


Operation of The SFA Interrupter


Single Pressure Gas Breakers

Also known as puffer breakers

No gas compressor required

Gas interrupter chamber contains gas at approximately 75psi

Are mechanically much simpler that two pressure breakers

Single pressure gas breakers require significant less maintenance than two pressure breakers







Two Pressure & Single Pressure Animation

Puffer Operation 2


Arc Assisted Or Self Blast Breaker

Current breaker design

Simpler and smaller with even greater interrupting ability

Uses the heat energy of the arc to create the high pressure stream of gas for arc interruption


Arc Assisted Or Self Blast Breaker

Includes a mechanical puffer piston for switching low grade faults and load currents where there is not enough heat to create the high pressure gas stream needed



The arc assisted puffer breaker or “self blast” breaker is the 3


generation of SF6 gas breakers

The self blast breaker is designed to use the heat from the arc to supply the blast pressure that extinguishes the arc during faults with higher current

This reduces the amount of operating energy needed for breaker operation. The operating mechanism now only needs to supply the energy needed to move the contacts


Advantages of Self Blast Breakers

The cost of the operating mechanism is reduced because it can be made smaller than before

The reliability is improved because there is less chance of mechanical failure from moving the bigger mechanical parts in earlier style breakers


ABB Self Blast interrupter chamber


High Fault Currents

During very high fault currents the arc will build enough pressure to close the self blast valves, preventing gas from flowing into the puffer volume. This forces the gas to flow through the nozzle and extinguish the arc


Low Grade Faults

During lower fault currents the arc will not build enough pressure to close the self blast valves and the interrupter will act like a puffer breaker


Self blast interrupter cycle for high current faults

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