Eskom has completed a multi-phase investigation into the use of methanol and ethanol as supplementary indicators of cellulose insulation degradation in power transformers, assessing whether alcohol analysis can add value alongside established condition monitoring tools such as dissolved gas analysis DGA and furan 2-FAL testing. This study was presented by Hlengiwe Nzima at CIGRE Southern Africa 2025.
Kraft paper remains the primary solid insulation material in large power transformers with its mechanical strength and remaining life closely linked to the degree of polymerisation DP. As the paper ages under thermal stress or fault conditions, it degrades and produces by-products including carbon monoxide, carbon dioxide, furans and alcohols. International studies have suggested that methanol may serve as an early stage indicator of cellulose depolymerisation while ethanol may be associated with high-temperature ageing or localised hotspots.
Eskoms study evaluated whether headspace gas chromatography with flame ionisation detection HS-GC-FID, implemented in accordance with ASTM D8086-20, could reliably detect methanol and ethanol at diagnostically useful concentrations, and whether meaningful trends could be established across its transformer fleet. Laboratory testing confirmed that the method could achieve clear separation and quantification of both alcohols down to low parts per billion levels.
