Transformer oil chromatography online monitoring summary of frequently asked questions: from the principle to the operation and maintenance of one-stop answer

• One Stop SolutionThis article summarizes the transformer oil chromatography online monitoring from the principle of cognition, equipment selection, installation and commissioning to the daily operation and maintenance of the whole process of the most commonly asked more than 20 questions, to provide a clear and practical answer!
• on-demand access: Q&A grouped by topic - basic principles, selection and procurement, installation and acceptance, operation and maintenance, fault judgment - easy to quickly locate according to the actual needs of the
• combat-oriented: All questions and answers come from high-frequency queries in engineering practice, and the answers are practical oriented, without theory piling up!

1. Fundamentals

1.1 Q. What is on-line transformer oil chromatography monitoring?

A: It is an intelligent on-line monitoring system directly installed in the transformer site, which detects the concentration of fault characteristic gas dissolved in the insulating oil in real time through the whole process of automatic oil extraction, degassing and chromatographic analysis, and automatically diagnoses whether there is overheating or discharge fault inside the transformer.

1.2 Q. What gases are detected by oil chromatography monitoring?

A: The full-component system can detect hydrogen (H₂), carbon monoxide (CO), carbon dioxide (CO₂), methane (CH₄), ethane (C₂H₆), ethylene (C₂H₄), acetylene (C₂H₂), a total of seven kinds of fault characteristics of the gas, and some of the systems can be equipped with an optional micro water content detection.

1.3 Q. What faults does each gas represent?

A: Hydrogen corresponds to partial and low-energy discharges; acetylene is the signature product of arc discharges; ethylene represents high-temperature superheating in oil; methane and ethane represent low-temperature superheating; and carbon monoxide and carbon dioxide come from thermal decomposition and aging of solid insulating materials.

1.4 Q. What is the difference between on-line and off-line monitoring?

A: Online monitoring is installed in the field for continuous operation, with automatic sampling and testing on an hourly basis, which is suitable for daily monitoring and trend warning. Offline testing is carried out in the laboratory, with higher accuracy but longer cycle time, suitable for annual physical examination and confirmation of anomalies. The two are complementary.

2. Selective procurement category

2.1 Q. How do I select the configuration level of an online oil chromatography monitoring system?

A: The voltage level and importance of the transformer is the main basis. 220kV and above main transformers are recommended to be enhanced configuration with full components and micro-hydrogen, 110kV main transformers can be selected as standard seven-gas configuration, and distribution transformers can be selected as less-component or single-hydrogen program. The core principle is to configure according to need.

2.2 Q: What is the choice between oil chromatography and oil spectroscopy?

A: Chromatography is a mature technology with full gas coverage and strong diagnostic capability, suitable for key main transformers. Spectroscopy does not require carrier gas and chromatographic column, small maintenance, suitable for unattended sites with limited maintenance conditions. The decision is made according to the maintenance capability and diagnostic depth requirements.

2.3 Q. What should be the most important concern when selecting a supplier?

A: Focus on three core dimensions: whether it has the independent research and development capability of the core analysis unit, the number and quality of actual engineering cases in similar scenarios, and the responsiveness and guarantee capability of after-sales service. One of the three is indispensable.

2.4 Q. What are the main factors that determine the price of equipment?

A: The type of gas to be detected is the most important price variable, followed by the configuration of the communication protocol, the availability of a background diagnostic platform, and the protection requirements of the installation environment. It is recommended to get the same configuration program from multiple vendors for comparison after configuration according to needs.

3. Installation and acceptance category

3.1 Q. How long does it take to install? Will there be a power outage?

A: Standard installation is usually completed in 1~2 days, the whole process is connected through the existing sampling valve and oil return port of the transformer, without power outage. The installation includes equipment positioning, oil pipe connection, electrical wiring and communication debugging.

3.2 Q. What should be checked during acceptance?

A: Appearance and installation quality check (no leakage, wiring specification), functional acceptance (self-test passed, normal sampling, normal communication), performance acceptance (standard gas sampling comparison, repeatability verification). All three items can be passed before signing acceptance.

3.3 Q. Where should the equipment be installed?

A: As close as possible to the transformer sampling valve to shorten the length of the oil pipe. Good ventilation is required for indoor installation, and a protective cabinet is required for outdoor installation. Avoid direct sunlight, rain and strong electromagnetic interference sources.

3.4 Q. Is it normal for there to be a discrepancy between the data monitored online and the data from the offline laboratory?

A: It is normal for there to be some deviation between the two for reasons including sampling method, degassing method and detector differences. Acceptance is based on the standard gas injection results, and the oil sample comparison is used as a reference. The key is to see whether the trend is consistent.

4. Operation and maintenance category

4.1 Q: How often should carrier gas be changed?

A: Carrier gas consumption depends on the sampling frequency. A bottle of carrier gas can be used for 3 to 6 months under typical conditions of 2 tests per day. It is recommended to replace the carrier gas before the pressure drops to the minimum allowable value to avoid interruption of the monitoring continuity.

4.2 Q. How often are equipment calibrations done?

A: It is recommended that calibrations be performed at least once a year. The calibration is done by a professional using a standard gas mixture with known concentrations of each component. The frequency of calibration should be increased if the equipment operates in a harsh environment or if there are unusual fluctuations in the data.

4.3 Q. What is the appropriate length of time to set the sampling period?

A: The main transformer is recommended to be 2~4 hours, which can be shortened appropriately in the season of high faults; the general distribution transformer can be set to 12~24 hours. The system should support online modification of the period to adapt to different working conditions.

4.4 Q: How long can data storage be kept?

A: The local storage capacity of mainstream systems can save data for more than 1 year or even 10 years. Systems with remote data backup function can better protect data security. It is recommended to export data regularly for offline backup.

5. Trouble-shooting categories

5.1 Q. What happens when data anomalies are detected?

A: First rule out equipment false alarms (check sensors, communications, environmental interference), confirm that the data is real and then observe the trend - whether it is a single point of jumping or a continuous rise. If the trend is confirmed, shorten the sampling period to encrypt the monitoring, and at the same time, arrange for offline oil sampling and re-inspection, and develop an overhaul plan based on the re-inspection results.

5.2 Q. Under what circumstances is immediate decommissioning required?

A: Acetylene levels rise sharply and continue to grow, total hydrocarbons increase exponentially in a short period of time, hydrogen levels skyrocket and accompany the presence of acetylene - all of these signals imply that a serious discharge fault is occurring within the transformer, and that shutdown should be scheduled for inspection as soon as possible.

5.3 Q: How do you distinguish between single-point data anomalies and trend anomalies?

A: Single-point data anomaly is manifested as a sudden deviation of a certain detection value but back to normal in the next cycle, usually related to transient interference or sampling fluctuations. Trend anomalies are multiple consecutive data changes in the same direction and are a true signal of failure. The core value of online monitoring is the ability to provide dense trend data.

5.4 Q: What is the difference between the three-ratio method and the David's Triangle method?

A: Both are standard DGA diagnostic methods. The three-ratio method categorizes faults into different types through three pairs of gas concentration ratios, which is a simple and direct method; the David's Triangle method locates the three hydrocarbon gas ratios in triangular coordinates, which is more intuitive to show the fault area. The two methods complement each other to improve diagnostic accuracy.

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.

More technical questions about transformer oil chromatography online monitoring? Welcome to contact Inotera, a team of engineers for your one-on-one answer. Service hotline: 13959168359 (WeChat same number).