Transformer Oil Chromatography vs Oil Spectroscopy: Comparison of Technical Routes and Applicable Scenarios
Date: May 16, 2026 02:00:00
- chromatography: The use of chromatographic columns to physically separate gas mixtures and detect the concentration of each component one by one. Mature technology, well-established standards, and simultaneous detection of more than 7 gases are the mainstream route for DGA online monitoring.
- spectroscopy: Directly analyzes the absorption intensity of a gas at a specific wavelength using optical principles (photoacoustic spectroscopy or infrared absorption spectroscopy), eliminating the need for a column and carrier gas and resulting in lower maintenance costs.
- Core differences: Chromatography has a wide coverage of gases and strong diagnostic capability; spectrometry has a simple structure and fewer consumables, but the types of gases that can be detected are limited.
- selective logic: Priority chromatography for critical main transformers in pursuit of comprehensiveness, general distribution transformers or scenarios with limited maintenance conditions may consider spectroscopy
1. How the two technology tracks work
1.1 Gas Chromatography
The gas mixture from the transformer oil is pushed into the column by a carrier gas. The inner wall of the column is coated with a special stationary phase. Different gas molecules interact with the stationary phase with different forces, resulting in a difference in the speed of movement inside the column - the lighter gases come out of the column first, and the heavier gases come out of the column more slowly. After leaving the column, the gases enter the detector sequentially, each peak corresponds to a gas, and the peak area corresponds to the gas concentration.
1.2 Photoacoustic spectroscopy
The stripped gas mixture is not separated by chromatography and is directly irradiated with modulated light of a specific wavelength. The different gas molecules are excited by absorbing the light energy of the specific wavelength, releasing heat during the radiation-free jump leading to expansion of the gas micro-regions and generating detectable acoustic signals. The concentration of each gas is detected one by one by switching filters of different wavelengths.
2. Comparisons across the board
| comparison dimension | gas chromatography | photoacoustic spectroscopy |
|---|---|---|
| Detectable gases | H₂, CO, CO₂, CH₄, C₂H₆, C₂H₄, C₂H₂, etc. more than 7 types | Usually 3 to 5 types, some models up to 7 types |
| Technology maturity | High, well-established IEC and GB standards | Medium, standards coverage is not yet complete |
| Consumables requirements | Requires carrier gas (high purity nitrogen or argon), column needs to be replaced periodically | No need for carrier gas and columns, minimal consumables |
| Maintenance complexity | Medium, carrier gas and column need to be replaced periodically | Low, virtually maintenance-free |
| Inter-gas interference | Thorough separation of columns with low inter-gas interference | Cross-talk needs to be corrected by software algorithms |
| Single test time | About 30~60 minutes | About 10~30 minutes |
| Equipment Volume | Larger, with air circuit system | Can be made more compact |
3. Analysis of applicable scenarios
3.1 Preferred Chromatography Scenarios
220kV and above main transformers - need the most comprehensive gas coverage and the most authoritative diagnostic basis, chromatography is the standard choice. Scenarios with high requirements for fault diagnosis depth - requiring multi-dimensional diagnosis such as the three-ratio method and David's triangle method, chromatography provides a more complete data base. Established substations - Chromatography has accumulated technology for a long time and has better compatibility with existing systems.
3.2 Scenarios that prioritize spectroscopic methods
Unattended stations with limited maintenance conditions - the no-carrier gas and maintenance-free features are ideal for stations that are difficult for personnel to reach frequently. Scenarios with stringent requirements on equipment size - e.g. mobile monitoring trucks, compact distribution rooms. Limited budget and only basic fault warning is required - spectrometry may be cheaper in terms of both one-time investment and long-term O&M costs.
4. Recommendations for selection decisions
4.1 If the transformer is a grid hub device and requires a high level of diagnostic depth - choose chromatography for a one-step solution.
4.2 If it is a distributed distribution transformer with limited O&M manpower - the maintenance-free nature of spectroscopy may be more valuable than detecting several more gases.
4.3 The two are not mutually exclusive. Within the same station, the main transformer color spectrum is fully covered and the distribution transformer spectrum is lightly deployed to form a high and low monitoring system.
5. Frequently Asked Questions FAQ
5.1 Q. Is spectrometry less accurate than chromatography?
A: Within their respective calibrated detection ranges, the two are close to the same level of accuracy. The difference is mainly in cross-interference - chromatography has a thorough physical separation and less interference. However, spectrometry is compensated by software algorithms and can also meet engineering accuracy requirements in most scenarios.
5.2 Q. Can spectroscopy completely replace chromatography?
A: Not yet. Chromatography still has a clear advantage in terms of gas species coverage and standardization. However, the competitiveness of spectrometry in maintenance-free scenarios is rapidly increasing, and the boundaries between the two will become more and more blurred in the future as technology advances and standards improve.
5.3 Q. Is there a significant price difference between the two units?
A: Initial purchase prices vary somewhat. However, the cost cannot be evaluated by looking only at the unit price of the equipment - the ongoing investment in consumables for chromatography (carrier gases, columns) can accrue significant O&M costs over a 5 to 10 year operating period. Spectroscopy, although the equipment price may be slightly higher, may have a better long-term total cost of ownership.
5.4 Q. Can the data from the two devices be compared with each other?
A: Absolute values of gases detected with different techniques on the same transformer may deviate. When doing trend analysis, it is recommended that the same equipment be maintained for continuous monitoring and the detection method should not be changed frequently to ensure consistency in data comparison.
5.5 Q: Are there any chromatography + spectroscopy composites available?
A: Composite technology solutions exist in the laboratory, but are still relatively rare in industrial field applications. The reason for this is that the maintenance requirements of the two technologies are so different that compounding them together increases the complexity of the system and the advantages are less obvious.
6. Summary
Chromatography is suitable for critical equipment pursuing comprehensiveness and diagnostic depth, while spectroscopy is suitable for distributed scenarios pursuing maintenance-free and simplicity. Which technology route to choose depends on the transformer's role position and O&M strategy. Not sure how to choose? It is recommended to do a needs assessment before finalizing the plan.
Disclaimer: The content of this article is for technical exchanges and reference only, and does not constitute any form of procurement commitment or contract offer. Product technical parameters, configuration programs and prices are subject to the actual signed contracts and technical agreements. The technical data and cases involved in this article are from public information and engineering practice, if updated without notice.
Need to compare online monitoring solutions for oil chromatography or oil spectroscopy? Welcome to contact Inotera for professional technical selection support. Service Hotline: 13959168359 (Wechat with number).
