1. Development of The SF6 Circuit Breakers

2. Three types of SF6 Breakers
Two Pressure Gas Breakers
Puffer Gas Breakers
Arc Assisted / Self Blast Puffer Gas Breakers

3. 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.

4. 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

5. 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)

7. Westinghouse SFA Two Pressure Interrupter

8. Operation of The SFA Interrupter

9. 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

12. Two Pressure & Single Pressure Animation
Puffer Operation 1
Puffer Operation 2

13. 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

14. 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

15. Overview
The arc assisted puffer breaker or “self blast” breaker is the 3rd 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

16. 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

17. ABB Self Blast interrupter chamber

18. 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

19. 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

20. Self blast interrupter cycle for high current faults