Production Rates for Oxyfluorides SOF₂, SO₂F₂, and SOF₄ in SF₆ Corona Discharges

Area of Science:

• Electrical Engineering
• Chemical Physics
• Materials Science

Background:

• Sulfur hexafluoride (SF₆) is widely used in high-voltage equipment.
• Corona discharges in SF₆ can produce hazardous byproducts.
• Understanding byproduct formation is crucial for equipment safety and longevity.

Purpose of the Study:

• Quantify the production rates of oxyfluorides (SOF₂, SO₂F₂, SOF₄) and other species (SO₂, OCS, CO₂) from SF₆ corona discharges.
• Investigate the influence of gas pressure, discharge parameters, and trace contaminants (O₂, H₂O) on byproduct formation.
• Determine the primary factors controlling SF₆ decomposition in electrical discharges.

Main Methods:

• Experimental measurement of absolute energy and charge rates-of-production for gaseous species.
• Controlled corona discharge experiments in SF₆ with varying O₂ and H₂O concentrations.
• Gas analysis using chemical procedures to identify and quantify products.

Main Results:

• SOF₂, SO₂F₂, and SOF₄ are the dominant, long-lived gaseous byproducts.
• Oxyfluoride production is independent of O₂ and H₂O concentrations below ~1%.
• The dissociation rate of SF₆ is the rate-limiting factor for oxyfluoride production.

Conclusions:

• SF₆ decomposition in corona discharges is primarily governed by the SF₆ dissociation rate.
• Trace gas levels of O₂ and H₂O do not significantly control oxyfluoride formation at low concentrations.
• Results inform the design of chemical diagnostics for SF₆-insulated high-voltage apparatus.