IEC TR 63025:2021

Overview

IEC TR 63025:2021 - "Insulating liquids – Quantitative determination of methanol and ethanol in insulating liquids" - defines laboratory test methods for the quantitative measurement of methanol (MeOH) and ethanol (EtOH) dissolved in insulating liquids. These light alcohols are produced by degradation of cellulosic materials (paper/pulp) used in oil‑impregnated transformers and can act as ageing tracers: their in‑oil concentrations help indicate paper deterioration and transformer health. The Technical Report provides two complementary analytical routes: a more sophisticated method and a simpler, cost‑effective method.

Key topics and technical requirements

• Two test methods
  • Method A - HS‑GC‑MS: Headspace gas chromatography coupled with mass spectrometry for selective and accurate quantification.
  • Method B - HS‑GC‑FID: Headspace gas chromatography with flame ionization detection as a practical, widely available alternative.
• Sampling and sample preparation: Guidance on representative sampling, degassing of insulating liquid, vial handling and headspace vial preparation to ensure reliable results.
• Calibration and quantification: Use of internal standards, preparation of calibration solutions, and procedures for establishing response factors.
• Instrument parameters: Recommended headspace sampler, GC temperature programs, injector and carrier gas considerations, and detector settings (MS and FID).
• Performance and validation data: Statements and tables on detection limits, repeatability and reproducibility, and verification of the analytical system.
• Reporting: Required elements for the test report to ensure traceability and comparability of results.

Applications and users

IEC TR 63025:2021 is intended for:

• Transformer manufacturers and OEMs - to support design validation and ageing studies.
• Utilities and asset managers - for condition monitoring and predictive maintenance of power transformers.
• Oil testing and diagnostic laboratories - to implement standardized, validated methods for routine in‑oil analysis.
• Research institutions - studying cellulose degradation chemistry, alternative insulating fluids and ageing markers.

Practical uses include early detection of paper ageing (MeOH often rises before furanic markers), trending of alcohol concentrations for lifecycle assessment, and comparative testing across insulating liquid types.

Related standards

• The report complements other IEC standards and literature on transformer oil analysis, dissolved gas analysis (DGA), and furanic compound testing. Laboratories should consult IEC TR 63025 alongside relevant normative references and national regulations for health, safety and laboratory accreditation.

Keywords: IEC TR 63025:2021, insulating liquids, methanol, ethanol, HS‑GC‑MS, HS‑GC‑FID, transformer oil analysis, ageing tracers, quantitative determination, oil diagnostics.