Transformer oil chromatography online monitoring is what?
Date: Thu, 15 May 2026 10:00:00
- Online monitoringThe system is installed directly on the transformer site, connected to the transformer body through the inlet and outlet oil pipes, and can be installed and put into operation without power failure.
- automatic samplingAutomatically extracts transformer insulating oil for degassing analysis according to a set cycle (as fast as 2 hours/times), replacing the traditional mode of taking oil samples manually and sending them for inspection.
- Multi-gas detection: Simultaneous detection of hydrogen (H₂), carbon monoxide (CO), carbon dioxide (CO₂), methane (CH₄), ethane (C₂H₆), ethylene (C₂H₄), acetylene (C₂H₂), and the seven critical fault characterization gases with a single analysis
- intelligent diagnosisBuilt-in standard diagnostic models such as Triple Ratio Method and David's Triangle Method, automatically determining whether there are fault types such as overheating and discharging inside the transformer.
- Data uploadingSupport MODBUS, IEC61850 and other standard communication protocols, monitoring data can be directly connected to the station SCADA platform or remote diagnostic center.
1. What is Dissolved Gas Analysis (DGA) in oil?
Oil-immersed transformer in the operation process, the internal insulating oil and solid insulating materials will be due to electro-thermal stress gradually aging and decomposition, resulting in a trace of gas dissolved in the oil. When the transformer internal overheating or discharge faults, the gas production rate will rise sharply, the gas component also shows characteristic changes.
The core logic of DGA technology is: by analyzing the components and content of dissolved gases in the oil, the type and severity of faults that may exist inside the transformer can be deduced. This is now internationally recognized as one of the most effective means of monitoring the condition of oil-immersed transformers, and has been incorporated into IEC 60599 and GB/T 7252 standards.
2. Workflow of online oil chromatography monitoring
The operation of the system is divided into four key segments:
2.1 Automatic oil extraction and degassing
The system extracts insulating oil from the transformer sampling valve through the circulating oil circuit and enters the vacuum degassing unit. Adopting dynamic vacuum degassing technology, the trace gas dissolved in the oil is separated out efficiently, and the degassed oil is sent back to the transformer body, the whole process is closed cycle, without loss of insulating oil.
2.2 Gas Chromatographic Separation
The gas mixture enters the chromatographic column. The column is filled with special adsorbent material, and different gas components migrate through the column at different speeds - the lighter gases flow out first, and the heavier components flow out later, thus realizing complete separation of the gas mixture.
2.3 Quantitative analysis of detectors
The separated gas components enter the high sensitivity detector sequentially, generating an electrical signal proportional to the gas concentration. The system automatically recognizes and integrates the peaks, and outputs the exact concentration of each gas in μL/L (ppm).
2.4 Troubleshooting and Early Warning
Comparing the detected data with the historical baseline value, combined with diagnostic models such as the three-ratio method and David's Triangle, it automatically identifies the type of fault - whether it is overheating in the oil, overheating in the solid insulation, or partial discharge or arc discharge. Diagnostic results are presented in the form of trend graphs and reports, and an alarm message is immediately pushed once the limit is exceeded.
3. What faults are represented by each of the seven characteristic gases?
There are significant differences in the gas components produced by different fault types, which are the basis for DGA diagnosis:
| Gas name | chemical formula (e.g. water H2O) | Corresponding fault type | Key Judgment Points |
|---|---|---|---|
| hydrogen (gas) | H₂ | Partial discharge, low energy discharge | When hydrogen in oil is abnormally high but other gases do not change significantly, focus on the risk of local discharge |
| ethyne C2H2 | C₂H₂ | Arc discharge, high energy discharge | The presence of trace amounts of acetylene requires a high degree of vigilance and usually means that there is a serious discharge fault within the transformer. |
| vinyl | C₂H₄ | Superheated oil cracking (>500°C) | Rising ethylene levels often indicate that the oil temperature has exceeded 500°C and that there is serious oil overheating. |
| methane CH4 | CH₄ | Low temperature overheating (300~500℃) | When both are present together, it usually points to a thermal failure with an oil temperature between 300℃ and 500℃. |
| ethane (C2H6) | C₂H₆ | Low temperature overheating (300~500℃) | |
| carbon monoxide CO | CO | Solid insulation overheating/deterioration | Decomposition products of solid insulating materials (insulating paper, cardboard), CO/CO₂ ratio to determine the degree of aging. |
| carbon dioxide CO2 | CO₂ | Solid insulation overheating/deterioration |
Total hydrocarbons (the total value of the above carbon-containing gases) is a comprehensive indicator reflecting the overall health status of the transformer, and the national standard has clearly defined the attention value and warning value of total hydrocarbons.
4. Online vs. offline monitoring: why online?
Offline oil sampling and sending for inspection is a periodic inspection, and the interval between two samples may be half a year to a year. However, in actual operation, some faults develop into accidents within days or even hours from the time they occur - the value of on-line monitoring lies in filling the time blind spot between regular inspections.
The two are positioned as complements rather than substitutes: offline testing data is more comprehensive and authoritative, suitable for annual medical check-ups; online monitoring response is more timely and intensive, suitable for daily monitoring and early warning.
5. Frequently Asked Questions FAQ
5.1 Q: How often is transformer oil chromatography online monitoring tested?
A: The sampling period can be set freely, generally 2~24 hours. For heavy load or important transformers, it is recommended to set it to 2~4 hours in order to detect abnormal trends in time. For general distribution transformers, 1~2 times per day can meet the demand.
5.2 Q. What is the measurement accuracy of on-line oil chromatography monitoring?
A: The system's detection accuracy varies for different gases. Measurement errors for core fault characterizing gases are usually within reasonable limits with good reproducibility. The focus of online monitoring is on trend changes rather than absolute values - even if there is some error, as long as the data is stable and the trend is traceable, it is sufficient to support fault warning decisions.
5.3 Q. What is the difference between oil chromatography monitoring and oil spectroscopy monitoring?
A: Both of them detect dissolved gases in oil, but the technical route is different. Chromatography adopts physical separation of chromatographic column and then detects one by one, with mature technology and perfect standard, and can detect more than 7 kinds of gases at the same time; Spectroscopy directly analyzes the absorption spectra of gases by using optical principle, which does not need to consume carrier gas, and is simpler to maintain, but the types of gases that can be detected are relatively fewer. Which one to choose depends on the specific needs of the scene.
5.4 Q. Is it complicated to install an online oil chromatography monitoring system?
A: The installation process is relatively simple. All the system needs to do is connect the transformer's inlet and outlet oil flanges, and connect the power and communication cables. Standard installation can be completed in one day and the entire process does not require a transformer outage and does not affect normal operation.
5.5 Q. What should be done when gas anomalies are monitored?
A: First rule out system false alarms and equipment anomalies to confirm that the data is real and valid. Then observe the persistence of the abnormal trend - whether it is a single point jump or a continuous rise. If the trend is confirmed, it is recommended to shorten the sampling period to encrypt the monitoring, and at the same time, arrange to manually take oil samples for offline re-inspection. Based on the results of the retest and troubleshooting recommendations, develop a targeted maintenance plan.
6. How to choose a suitable online monitoring program for oil chromatography?
The core of selection is to match the actual needs, not the higher the parameters the better:
6.1 Define the monitoring object - is it a main transformer, distribution transformer or furnace transformer? Transformers of different voltage levels have different requirements for monitoring accuracy and response speed.
6.2 Determine the functional requirements - which gas components need to be detected? Is there a need to monitor micro-water content at the same time? Do you need to integrate local alarms?
6.3 Consider the installation environment - indoor or outdoor? Is there an existing communications network? How will the power supply be taken?
It is recommended to choose suppliers with independent research and development capabilities that can provide complete diagnostic software. The factory direct supply model can avoid intermediate links, and is more guaranteed in terms of technical response and after-sales service.
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.
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