An Eskom-authored technical paper has underscored the critical importance of laboratory testing, diagnostics and handling protocols as utilities seek to replace sulphur hexafluoride (SF₆) with lower-emissions alternatives in high-voltage electrical equipment.
Presented during the CIGRE Southern Africa Regional Conference in Pretoria in October 2025, the paper reviews international testing methodologies used to assess a range of SF₆ substitute gases against the backdrop of growing regulatory and environmental pressure to phase down the use of SF₆. The gas has a global warming potential around 23 500 times that of CO₂ and an atmospheric lifetime exceeding 3 000 years, making it one of the most potent greenhouse gases still widely used in power systems.
Authored by Vusumuzi Sibeko of Eskom, the review examines alternatives including g³ gas mixtures (CO₂/C₄F₇N), C₄F₇N (fluoronitriles), C₅F₁₀O (fluoroketones), CF₃I, CO₂ and hydrofluoroolefins (HFOs). While many of these gases offer dramatically lower global warming potential than SF₆, the paper states their chemical behaviour under electrical stress introduces new operational and safety risks that must be carefully managed.
The review highlights laboratory techniques such as gas chromatography-mass spectrometry, Fourier-transform infrared spectroscopy, flame ionisation detection and related analytical methods as essential tools for characterising gas purity, dielectric performance and decomposition by-products. Under arcing, partial discharge or elevated temperatures, several SF₆ alternatives can break down into toxic or corrosive compounds including carbon monoxide, hydrogen cyanide, hydrofluoric acid and iodine-containing species depending on the gas chemistry.
Moisture sensitivity emerges as a key concern. According to Sibeko, fluorinated alternatives such as g³, C₄F₇N and C₅F₁₀O are particularly vulnerable to hydrolysis, which can degrade insulation performance and accelerate equipment corrosion if strict moisture limits are not maintained. This has implications for gas handling, storage, filling procedures and long-term condition monitoring in transmission and distribution assets.
Although several alternatives demonstrate dielectric strengths approaching that of SF₆, Sibeko notes that differences in thermal stability, material compatibility and by-product toxicity mean there is no direct “drop-in” replacement. Instead, utilities may need to invest in new laboratory infrastructure, standardised diagnostic methods and revised maintenance practices, and adapt certain materials and components within switchgear designs.
According to Sibeko, the findings support Eskom’s ongoing efforts to transition toward low-global warming potential insulating technologies in line with international sustainability objectives while cautioning that environmental benefits must be balanced against operational reliability and personnel safety. “Advancing SF₆ alternatives is essential for reducing the carbon footprint of high-voltage networks but robust, standardised laboratory testing is a prerequisite for their safe and reliable deployment at scale,” he says.
