Question

Which of the following is commercially used in gas blast Circuit breakers?

• A. Hydrogen
• B. Nitrogen
• C. SF\textsubscript{6}
• D. Both hydrogen and SF\textsubscript{6}

Hint:

SF\textsubscript{6} = Industry standard gas for circuit breakers due to superior dielectric and arc-extinguishing properties.

Answer 1

The Correct Option is C

Step 1: Introduction to Gas Blast Circuit Breakers
Gas blast circuit breakers use an insulating gas to quench the arc that forms when the breaker interrupts the current. The choice of gas is crucial for effective arc extinction and insulation.
Step 2: Role and Properties of SF\textsubscript{6 (Sulfur Hexafluoride)}
SF\textsubscript{6} is a colorless, odorless, non-flammable, and non-toxic gas that has excellent insulating and arc-quenching properties. Its high dielectric strength and electronegativity make it ideal for use in high-voltage circuit breakers.
Advantages of SF\textsubscript{6:}
\item High dielectric strength (2–3 times greater than air).
\item Excellent arc quenching by electron attachment.
\item Chemically stable and non-corrosive.
\item Permits compact equipment design.
Step 3: Commercial Adoption
Because of the above benefits, SF\textsubscript{6} has become the industry standard for gas-insulated switchgear and gas blast circuit breakers, especially for voltages above 66 kV.
Conclusion:
Option (3) is correct because SF\textsubscript{6} is the only gas among the options that is widely and commercially used in modern gas blast circuit breakers.