Transformer Oil Dissolved Gas Analyzer Lab Equipment Digital Chromatography Tester
Dissolved gas analysis (DGA) is a method used to study the dissolved gases in transformer oil. It is also known as a DGA test. When a transformer undergoes abnormal thermal and electrical stresses, certain gases are produced due to the breakdown of the transformer oil. If the fault is major, the production of decomposed gases is significant and they are collected in a Buchholz relay. However, when the abnormal stresses are not significantly high, the gases due to the breakdown of transformer insulating oil will dissolve in the oil over time.
Therefore, monitoring only the protection relay tester is not sufficient to predict the overall internal health of an electrical power transformer. This is why it is necessary to analyze the types and quantities of different gases that are dissolved in transformer oil during service. By using DGA of transformer oil, the actual condition of the internal health of a transformer can be predicted.
It is recommended to conduct the DGA test of transformer oil routinely to gather historical information about the internal health of a transformer over its lifetime. During a DGA test, the gases in oil are extracted and analyzed to determine the quantity of gases in a specific amount of oil. By observing the percentages of different gases present in the oil, the internal condition of the transformer can be predicted.
Typically, the gases found in the oil during service are hydrogen (H2), methane (CH4), ethane (C2H6), ethylene (C2H4), acetylene (C2H3), carbon monoxide (CO), carbon dioxide (CO2), nitrogen (N2) and oxygen (O2).
The most commonly used method to determine the content of these gases in oil is by using a Vacuum Gas Extraction Apparatus and Gas Chromatographs. This apparatus extracts gases from oil by stirring it under vacuum, and the extracted gases are introduced into gas chromatographs for measurement of each component.
It is generally found that hydrogen and methane are produced in large quantities if the internal temperature of a power transformer rises up to 150oC to 300oC due to abnormal thermal stresses. If the temperature goes above 300oC, ethylene (C2H4) is produced in large quantities. At temperatures higher than 700oC, a large amount of hydrogen (H2) and ethylene (C2H4) are produced.
The presence of ethylene (C2H4) is an indication of a very high-temperature hot spot inside an electrical transformer. If during the DGA test of transformer oil, CO and CO2 are found in large quantities, it indicates the decomposition of proper insulation.
Compliance with standards
1,GB/T 17623-2017 Determination of dissolved gas components in insulating oil by gas chromatography
2,GB/T 7252-2001 Guidelines for analysis and judgment of dissolved gases in transformer oils
3,DL/T 722-2014 Guidelines for analysis and judgment of dissolved gases in transformer oils
4,DL/T 703-2015 Gas Chromatographic Method for the Determination of Gas Content in Insulating Oils
Workflow chart
Technical Parameters
| Limit of detection (µL/L) |
| Components |
Detection limit |
Components |
Detection limit |
| H2 |
2 |
C2H4 |
0.05 |
| CO |
2 |
C2H6 |
0.05 |
| CO2 |
5 |
C2H2 |
0.05 |
| CH4 |
0.05 |
|
|
| Detector technical specifications |
| Thermal Conductivity Detector (TCD) |
Hydrogen flame ionization detector (FID) |
| Semi-diffusive structure |
Programmed auto-ignition (above 130°C auto-ignition) |
| Power supply with constant current control |
Automatic ignition; stabilization time: 10 minutes |
| Sensitivity: ≥10000mV-ml/ mg (benzene) |
Detection limit: ≤3x10-12g /s (n-hexadecane/isooctane) |
| Baseline noise: ≤10uV |
Baseline noise: ≤5x10-14A |
| Baseline drift: ≤30uV/30min |
Baseline drift: ≥1x10-13A/30min |
| Linearity: ≥105 |
Linearity: >107 |
| Temperature control indicators |
| Temperature control part |
Temperature control range |
Temperature Control Precision |
| Column box |
4°C~450°C above room temperature |
±0.01°C |
| Hydrogen Flame (FID) Detector |
4°C~450°C at room temperature |
±0.01°C |
| Thermal Conductivity (TCD) Detector |
4C~450°C at room temperature
±0.01°C |
±0.01°C |
| Ni Catalyst Converter |
4°C~450°C at room temperature
±0.01°C |
±0.01°C |
| Steps of programmed temperature increase |
20 steps |
|
| Program Rise Rate |
0.1~60°C/min |
±0.01°C |
| Program Boost |
8 steps |
|
| Other Parameters |
| Power supply: 220V±10%, 50Hz |
Power: ≤1500W |
| Dimensions: 635*510*480mm |
Weight: <45kg |
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