TriboTech ApS
Expert Tribology Consultancy
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Normalise an in-oil ageing-marker reading (methanol, ethanol, 2-FAL or water) to a 20 °C reference so samples taken at different temperatures can be trended on a common basis — per CIGRE TB 779:2019, Fig 4-10. A trending aid, not a diagnostic.
Enter a concentration and a sampling temperature.
150 µg/kg at 55 °C
90 µg/kg at 60 °C
1.2 mg/kg at 45 °C
CIGRE TB 779:2019 Eq 4-3 defines the temperature-correction factor as Cf_M = [M]²⁰°C / [M]ᵀˢ, so the 20 °C-equivalent is [M]²⁰°C = Cf(T)·[M]measured. Water, methanol, 2-FAL and 2-FOL are read directly from TB 779 Table 6-1 (p.62; a mineral-oil + thermally-upgraded-paper system), linearly interpolated and used verbatim — not re-anchored to 1.0 at 20 °C. Ethanol has no Table 6-1 entry and keeps the digitised Fig 4-10 curve, so treat it as indicative and not directly comparable. Polar markers partition into oil as temperature rises, so Cf falls above 20 °C (it scales the hotter reading down). Steepness order: water > methanol > ethanol > 2-FOL > 2-FAL. Per TB 779 §6.4 the 2-FAL correction trend is not yet validated — use it for trending only (the companion DP estimator uses raw, uncorrected 2-FAL, so it is unaffected). Valid 20–100 °C. A temperature-normalisation aid only — there are no normative thresholds, so no condition is inferred; IEC TR 63025:2021 standardises the measurement method, not interpretation.