TOGAS Analysis System with oil stripper device Nexis GC-2030TOGAS1 GC-2014TOGAS1

Significance of the Topic

The accurate determination of dissolved gases in transformer oil is essential for monitoring the health of power transformers. Early detection of fault gases such as H₂, O₂, N₂, CH₄, CO, CO₂, and C₂ hydrocarbons helps prevent catastrophic failures and extends equipment lifespan.

Objectives and Study Overview

This study introduces a simple yet effective technique for Total Oil-Gas Analysis System (TOGAS) using an oil stripper device and valve-switching sequence. The goal is to achieve complete separation and quantification of permanent gases, methane, carbon oxides, and C₂ hydrocarbons within a single automated run.

Methodology

The approach combines oil-stripper sampling with precise valve switching to direct sample portions through three packed columns in series:

• Group separation on Column 1 (P-N).
• Permanent gases (H₂, O₂, N₂) and methane routed to Column 2 (MS-13X) for TCD and FID (via methanizer) detection.
• Higher hydrocarbons and CO₂ eluted to Column 3 (P-Q) for FID analysis.

The entire cycle runs in 16 minutes. Valve positions change before CO₂ elution and immediately after C₂H₂ detection, preparing the system for the next injection.

Used Instrumentation

The analysis utilizes a Shimadzu TOGAS configuration:

• Gas chromatograph models Nexis GC-2030TOGAS1 and GC-2014TOGAS1
• Two multiport valves and four packed columns: P-N, MS-13X, P-Q
• Detectors: thermal conductivity detector (TCD) and flame ionization detector (FID) with methanizer
• LabSolutions GC workstation software for control and data processing

Main Results and Discussion

The system achieved baseline separation of all target gases with the following concentration ranges:

• H₂: 20 ppm to 10 %
• O₂: 500 ppm to 1 %
• N₂: 500 ppm to 10 %
• CH₄: 1 ppm to 1 %
• CO, CO₂: 2 ppm to 2 %
• C₂H₆, C₂H₄, C₂H₂: 1 ppm to 1 %

Sensitivity for trace CO and CO₂ was enhanced by converting them to CH₄ in the methanizer prior to FID detection. Typical chromatograms demonstrate sharp peaks and minimal coelution.

Benefits and Practical Applications

This TOGAS method offers:

• Fast cycle time suited for routine transformer health monitoring.
• Simultaneous quantification of permanent and hydrocarbon gases in oil.
• Low detection limits for critical fault indicators (CO, CO₂).
• Automation friendly design reducing operator intervention.

Future Trends and Potential Applications

Emerging developments may include miniaturized valves and micro-packed columns for even faster runs, integration of mass spectrometric detectors for enhanced specificity, and online coupling for real-time transformer monitoring. Data analytics and machine learning could further refine fault prediction.

Conclusion

The described oil stripper TOGAS approach provides a robust, sensitive, and efficient solution for comprehensive gas analysis in transformer oils. Its combination of valve-switching, methanization, and multi-column separation meets the demands of modern power system diagnostics.

References

• ASTM D3612B. Standard Test Method for Analysis of Gases in Electrical Insulating Oil by Gas Chromatography.
• Shimadzu Corporation. System Gas Chromatograph TOGAS Analysis System Application Note, First Edition, November 2017.