Breakdown modeling of SF₆ and its environmentally friendlier alternatives in quasi uniform fields

<p dir="ltr">A retrofill solution of non-switching high-voltage SF₆ equipment using an environmentally friendlier alternative is an emerging solution different to a new-build approach where existing SF₆ equipment is decommissioned and replaced with new equipment. This work develops a streamer criterion model to enable the screening of a large number of SF₆ alternatives under representative parameters for retrofill application. Different operational parameters relevant to practical applications have been experimentally investigated under 50 Hz AC voltage waveform for absolute pressures of 1-6 bar, quasi uniform geometries with field utilization factors of 0.55-0.69 and average maximum surface roughness of 8–46.6 µm. The combined experimental and modeling validations inform that a 20% C₃F₇CN and 80% CO₂ mixture has a comparable dielectric performance as SF₆ over a wide-ranging conditions representative of gas-insulated line/busbar (GIL/GIB). Thus, this work demonstrates that a C₃F₇CN/CO₂ mixture is suitable for retrofilling the existing SF₆-designed equipment, which provides an economical and time saving approach that will expedite the transition to a more sustainable electricity grid through the complete phase-out of SF₆.</p>