Merel GE-567

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Merel GE-567

Fully automated gas extraction unit based on Multi-cycle Mercury free Vacuum extraction method coupled by a pump and tube with Agilent GC system, according to international standards IEC 60567 and ASTM D-361.

Mercury free Toepler principle gives more extracted gases, because extraction is made in high vacuum. Transfer of gas from the pump to the GC is with very little dead volume witch could be measured and use for corrections. If the content of gas is too low to inject to GC, it could be automatically diluted with air or argon.




Dissolved Gas Analysis (DGA) is a widely used technique to estimate the condition of oil- immersed transformers. Incipient faults within the transformer may be detected by analyzing the gases which are dissolved in the transformer-oil.
DGA is a diagnostic tool for detecting and evaluating of incipient faults in oil-immersed transformers. A fault is in this context defined as a process that causes abnormal dissipation of energy within the transformer. When a fault occurs in the transformer, the insulation system will undergo chemical degradation which leads to a production of various gases that dissolves in the oil. These gases are often referred to as key gases, and their concentrations can by various interpreting methods be related to different types of fault in the transformer.


The gases that are of interest for the DGA analysis are the following:

  •  H₂ – hydrogen
  • CH₄ – methane
  • C₂H₄ – ethylene
  • C₂H₆ – ethane
  • C₂H₂ – acetylene
  • C₃H₆ – propene
  • C₃H₈ – propane
  • CO – carbon monoxide
  • CO₂ – carbon dioxide
  • O₂ – oxygen
  • N₂ – nitrogen
  • TCG – total combustible gas content (H₂, CH₄, C₂H₄, C₂H₆, C₂H₂, CO, C₃H₆, C₃H₈)



1. Sampling of transformer oil

2. Extraction of the gases from the oil

3. Analysis of the extracted gas mixture in a gas chromatography, GC.

4. Interpretation of gas data



  • The system fully complies with norm IEC 60567.
  • Sample volume 10 to 250 ml.
  • The possibility of measuring the low levels of gas under 0.5 ml / l.
  • Free-setting of extraction parameters. (Define number of strokes and duration of each).
  • “Dead volume” could be measured for diagnostic and (or) volume correction.
  • The piston pump diagnostic with injection of 10 ml of air to verify the tightness of the piston.
  • Export measurements-value in EXCEL
  • View all operating parameters, including intermediate extraction with the announcement of the final result.
  • The conversion of the normalized value of 1013.25 mbar and 20 °C
  • All phases in extractions could be done manually in steps.
  • Calibration of the scale, pressure sensor, temperature sensor and vacuum sensor is included in the SW.
  • Buchholz gas analysis.
  • Analysis of the external gas (cylinder).
  • Use and hardware software leading manufacturer in the field of measuring / control equipment (National Instruments).
  • The user interface could be translated to the local language.



Transformer Oil Gas Analyzer (TOGA) system with Multi-cycle Mercury free Vacuum extraction

Oil sample volume: 10 – 200 ml
No. of positions: 20 / 125 ml
Gas extractor
Type of transformer oils: new and used
Dual stage vacuum oil pump: Ultimate pressure 2x10³ mbar
Gas extraction cycles and times: Set in software
Vacuum measurement/range: 1 .3 x 10³ mbar – 1333 mbar
Oil sample measurement/accuracy: gravimetric / ± 0.05 ml
Gas volume measurement: precision glass burette/precision pressure sensor – temperature compensated
Gas volume measurement corrected: To standard atmosphere (1013.25 mbar / 20 °C
Pressure sensor accuracy: ± 0.05 % @ 1013 mbar / 10-40 °C
Pressure sensor and balance calibrationPerformed in software
Extracted Gas volume range: 1 ml/l – 200 ml/l
Extracted Gas volume accuracy: ±10% @1 ml/l – 20 ml/l, ± 2% @ 20 ml/l – 200ml/l
Gas transfer and analyses: Standard TGA GC instrument (loop volume 0.25 – 1.0 ml)
Power input: 115 – 240 VAC, 50 – 60 Hz
Power Input: 950 W
Dimensions (WxHxD): 440 x 1040 x 620 mm
Weight: 50 kg