Application of sulphur hexafluoride (SF₆) in power systems SF₆ gas is widely used in high-voltage equipment because of its excellent dielectric strength and arc-quenching properties. Which equipment is the most typical application?

Introduction / Context:
Sulphur hexafluoride (SF₆) is an inert, non-flammable, high-electron-affinity gas with outstanding dielectric properties. Power engineers employ it where strong insulation and effective arc extinction are required under high voltage and current interruptions.

Given Data / Assumptions:

• Consider common high-voltage apparatus.
• Focus on roles requiring gaseous insulation and arc quenching.
• Environmental aspects (GWP) aside for the physics question.

Concept / Approach:

SF₆ supports high dielectric withstand and quickly quenches arcs by electron attachment and thermal properties. Hence, it is the standard medium in gas-insulated switchgear (GIS) and high-voltage circuit breakers. Transformers typically use mineral oil or ester fluids; generators use solid and air/hydrogen cooling; electromechanical relays do not rely on a special insulating gas for contacts.

Step-by-Step Solution:

Verification / Alternative check:

Manufacturer datasheets and substation layouts routinely specify SF₆ breakers and GIS bays for compact, high-voltage installations.

Why Other Options Are Wrong:

• Transformers: usually oil-paper systems.
• Generators: air or hydrogen cooling; solid insulation.
• Relays: do not require SF₆ environments.

Common Pitfalls:

Assuming any HV equipment uses SF₆; in practice it is specific to switchgear and breakers for insulation and arc control.

Final Answer:

High-voltage circuit breakers and gas-insulated switchgear