Experimental study on SF6 decomposition characteristics under spark discharges

Due to its stable performance and less occupied area, SF₆ gas-insulated apparatuses are rapidly gaining ground in the high-voltage and extra-high-voltage substations. And these SF₆ gas-insulated apparatuses play a vital role in power systems. Most of insulation failures evolve from early latent insulation faults, which lead to SF₆ decomposition. Accordingly SF₆ decomposition by-products can be used to diagnose early latent insulation faults. And as a diagnosis tool, the SF₆ decomposition characteristics under the insulation faults must be clear. As an early latent insulation fault, spark discharges are common in SF₆ gas-insulated apparatuses. In this paper the SF₆ decomposition characteristics under spark discharges are studied. The concentrations of the by-products SO₂F₂, SOF₂, SO₂, CF₄ and CO₂ as well as the ratios (SOF₂+SO₂)/SO₂F₂ and CO₂/CF₄ under various breakdown voltages and gas pressures are presented. The influence of breakdown voltages and gas pressures on the formation of SF₆ decomposition by-products is also discussed.