What Is Furan Analysis?

Published 27 Aug 2026Updated 27 Aug 20266 min readIntermediateDiagnostics
Quick answer — Furan analysis measures the furanic compounds in the transformer oil that are released as the paper (cellulose) insulation degrades. The furan content is a direct indicator of the state of aging of the solid insulation, so it complements DGA — which looks at the oil — by telling you how much of the paper has degraded. Rising furans indicate accelerated paper aging or a local hot spot.
Contents
What is furan analysis and what does it tell you?

What it measures

Furans are the by-products of cellulose (paper) degradation. The most common, 2FAL (2-furfuraldehyde), is measured in the oil and its level indicates the degree of paper aging.

Why it is useful

DGA sees the gas in the oil, but furans specifically show the condition of the paper insulation — the aging/damage that is the real life-limiting factor.

Interpreting

A rising furan level (or a sudden jump) indicates accelerated aging or a hot spot; combined with DGA, oil tests and a DP sample, it helps you decide the remaining life and the next action.

References & standards

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Prolec GE (GE Vernova) · Prolec GE Waukesha · Hitachi Energy USA · Siemens Energy · Eaton · Virginia Transformer Corp

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Oil, fluids & preservation Insulation materials
Technical content is prepared from engineering references, standards frameworks, manufacturer documentation and industry sources. Contractual or compliance decisions should refer to current official standards. TransformerPath Technical Editorial.
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