Substation Electrician Apprenticeship Practice Exam 2025 – Your All-in-One Guide to Mastering the Exam!

An SF6 gas breaker extinguishes an electrical arc primarily by using a gas blast to cool the arc. Sulfur hexafluoride (SF6) is an insulating gas that has excellent dielectric properties, which not only provides effective insulation between electrical contacts but also plays a crucial role in arc interruption processes.

When an electrical fault occurs and an arc is formed, the SF6 gas is directed to flow rapidly around the arc. This gas blast cools the arc temperature significantly. The rapid cooling effect reduces the energy of the arc, effectively quenching it and allowing the breaker to interrupt the fault current safely. The ability of SF6 gas to absorb and dissipate heat is a fundamental characteristic that enables its effectiveness in this application.

In contrast to other processes that might involve increasing temperature or reducing voltage, the cooling effect of the gas blast is essential for quickly extinguishing the arc and preventing any potential damage to the electrical system. Thus, the use of SF6 gas underlines its importance in the operation of modern gas-insulated switchgear and circuit breakers.