Transformer Oil Gas Analysis using a Stripper Column (ASTM D3612)

Significance of the Topic

Accurate detection of gases dissolved in transformer oil is vital for early fault diagnosis and prevention of catastrophic failures. The stripper column technique defined in ASTM D3612 Method C offers a reliable extraction route that complements vacuum extraction and headspace sampling by sparging carrier gas through the oil, capturing dissolved gases for GC analysis.

Objectives and Study Overview

This study evaluates the performance of a stripper column based system for dissolved gas analysis in transformer oil. It aims to demonstrate compliance with ASTM D3612, determine detection limits, assess repeatability, and illustrate full separation of key diagnostic gases using the SCION TOGA analyser.

Methodology and Instrumentation

A syringe infusion pump delivers oil samples to dual ten port valves with sample loops connected to stripper columns. Extraction is performed at 90°C for 9 minutes with a ramp to 120°C. Separated gas streams are analyzed by a GC equipped with a molsieve column (TCD channel, argon carrier) for light gases and a PoraPlot column with methaniser plus FID (helium carrier) for carbon gases. Calibration used a low concentration reference standard. Key gas low detection limits were 4.1 ppm for hydrogen, 32 ppm for oxygen, and 65 ppm for nitrogen.

Main Results and Discussion

The system achieved full separation and reliable quantification of ten diagnostic gases including H2, O2, N2, CO, CO2, CH4, C2H4, C2H6, C2H2, and C3 hydrocarbons. Repeatability testing yielded relative standard deviations below 1% for most analytes, confirming strong precision. Some peak broadening compared to direct GC analysis was noted due to stripper column interactions but remained within acceptable limits.

Benefits and Practical Applications

• High repeatability and low detection limits aligned with industry standards.
• Automated sample introduction and extraction reduce operator error.
• Comprehensive gas profiling supports condition monitoring and preventive maintenance in power transformers.

Future Trends and Potential Applications

Advances may include integration of real time on line monitoring, improved column materials for faster extraction, miniaturized analysers for field deployment, and coupling with predictive analytics platforms to enhance transformer health diagnostics.

Conclusion

The SCION TOGA analyser employing a stripper column extraction method fulfills ASTM D3612 Method C requirements, delivering robust separation, sensitive detection, and high precision. This approach offers a dependable solution for routine dissolved gas analysis in transformer oil, facilitating early fault detection and ensuring transformer reliability.