Methanol and ethanol in transformer oils have been recently proposed as new markers of thermal and mechanical degradation of cellulose (the solid insulation in power transformers). In this work, we optimized and compared the performance of two headspace gas chromatographic methods based on flame ionization (HS-GC-FID) and mass spectrometry detection (HS-GC-MS) to determine methanol and ethanol in insulating mineral oil. For methanol and ethanol, the detection limits were 12 and 27 μg kg-1 (HS-GC-FID) and 1.3 and 3.1 μg kg-1 (HS-GC-MS). Repeatability was evaluated in transformer oils for both the methods at different concentration levels of analytes and RSD values were found to lie between 1.8 and 16 %. The accuracy of the methods was assessed under a proficiency test (Cigré JWG A2/D1.46). The methods were compared by a F-test and a one-sided paired t test performed on 21 transformer oils in service. Correlations of methanol and ethanol content in sampled oils against their actual time of service are provided. For each sample, the content of traditional markers (furan-2-carbaldehyde and CO2) was also measured, finding a correlation between light alcohols and CO2 content. This indicates that methanol and ethanol determination may be helpful in providing further information on the thermal degradation conditions of transformers' solid insulation. The method developed is currently routinely applied by the laboratories of Sea Marconi Technologies for the assessment of transformers' conditions.

GC Methods for the Determination of Methanol and Ethanol in Insulating Mineral Oils as Markers of Cellulose Degradation in Power Transformers

BRUZZONITI, Maria Concetta;DE CARLO, Rosa Maria;SARZANINI, Corrado;
2014

Abstract

Methanol and ethanol in transformer oils have been recently proposed as new markers of thermal and mechanical degradation of cellulose (the solid insulation in power transformers). In this work, we optimized and compared the performance of two headspace gas chromatographic methods based on flame ionization (HS-GC-FID) and mass spectrometry detection (HS-GC-MS) to determine methanol and ethanol in insulating mineral oil. For methanol and ethanol, the detection limits were 12 and 27 μg kg-1 (HS-GC-FID) and 1.3 and 3.1 μg kg-1 (HS-GC-MS). Repeatability was evaluated in transformer oils for both the methods at different concentration levels of analytes and RSD values were found to lie between 1.8 and 16 %. The accuracy of the methods was assessed under a proficiency test (Cigré JWG A2/D1.46). The methods were compared by a F-test and a one-sided paired t test performed on 21 transformer oils in service. Correlations of methanol and ethanol content in sampled oils against their actual time of service are provided. For each sample, the content of traditional markers (furan-2-carbaldehyde and CO2) was also measured, finding a correlation between light alcohols and CO2 content. This indicates that methanol and ethanol determination may be helpful in providing further information on the thermal degradation conditions of transformers' solid insulation. The method developed is currently routinely applied by the laboratories of Sea Marconi Technologies for the assessment of transformers' conditions.
77
15-16
1081
1089
Ethanol; Gas chromatography; Methanol; Oil analysis; Paper degradation
M.C. Bruzzoniti; R. Maina; R.M. De Carlo; C. Sarzanini; V. Tumiatti
File in questo prodotto:
File Dimensione Formato  
Bruzzoniti13_feb_2014 not highlighted.pdf

Accesso aperto con embargo fino al 17/03/2015

Tipo di file: POSTPRINT (VERSIONE FINALE DELL’AUTORE)
Dimensione 639.67 kB
Formato Adobe PDF
639.67 kB Adobe PDF Visualizza/Apri
Author's copy.pdf

Accesso riservato

Tipo di file: PDF EDITORIALE
Dimensione 1.02 MB
Formato Adobe PDF
1.02 MB Adobe PDF   Visualizza/Apri   Richiedi una copia

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/150145
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 32
  • ???jsp.display-item.citation.isi??? 27
social impact