Transformer oil chromatography online monitoring system: DGA oil dissolved gas analysis technology full analysis

What is it?Transformer oil chromatography online monitoring system?

Transformer oil chromatography online monitoring system is a kind of intelligent monitoring equipment specially used for the analysis of dissolved gases in oil-immersed transformer oil. This kind of system adopts advanced gas chromatography analysis technology, which is able to detect the fault characteristic gases in transformer insulating oil in real time, and discover the potential faults inside the equipment in time.

Why is it necessary to monitor dissolved gases in oil? During the operation of a transformer, the internal insulating material will produce characteristic gases due to overheating, discharge and other faults. These gases are dissolved in the insulating oil, and by analyzing the changes in gas composition and concentration, the health status of the transformer can be accurately determined. Traditional offline testing requires power outages to take samples and send them for inspection, which is time-consuming and may miss the critical period of fault development.

DGA online monitoring system realizes the transformation from passive maintenance to active prevention. The system is capable of long-term online, regular automatic monitoring, real-time mastery of the internal operating status of the transformer and the development trend of faults, which significantly improves the operational safety of power equipment.

What gas components can be detected?

What are the seven key characteristic gases?

Oil chromatography online monitoring devices can accurately measure seven characteristic gases that reflect transformer fault information: hydrogen (H₂), carbon monoxide (CO), carbon dioxide (CO₂), methane (CH₄), ethane (C₂H₆), ethylene (C₂H₄), acetylene (C₂H₂). Each gas corresponds to a specific type of failure.

Hydrogen gas arises mainly from partial discharges and low-energy discharges. The four hydrocarbon gases methane, ethane, ethylene and acetylene reflect the degree of thermal decomposition of the insulating material, where the presence of acetylene usually means that a high-temperature fault or arc discharge has occurred. Carbon monoxide and carbon dioxide, on the other hand, originate mainly from the ageing and decomposition of solid insulating materials.

Why do you even need to monitor the microwater content?

In addition to the seven characteristic gases, the system can also add micro water monitoring according to customer needs. Moisture is an important factor affecting the insulation performance of transformers. Excessive water content in the oil reduces the insulation strength, accelerates the aging of the insulation material, and even triggers breakdown accidents.

The simultaneous monitoring of dissolved gas and microwater content enables a more comprehensive assessment of the insulation condition of the transformer. This comprehensive monitoring provides reliable data support for the development of scientific maintenance strategies.

How does the system work?

What is the principle of oil and gas separation technology?

Oil chromatography online monitoring device adopts dynamic vacuum degassing method to realize oil and gas separation. The system first fully circulates the transformer oil to ensure that the sampled oil is representative. Then take a small amount of oil samples into the oil and gas separation device, through the vacuum environment will be dissolved in the oil gas separation.

This degassing method is highly efficient and reproducible, ensuring the accuracy of each measurement. Compared with other degassing techniques, the dynamic vacuum method has little disturbance to the oil sample and does not affect the normal operation of the transformer.

What is the process of gas chromatography analysis?

The separated characteristic gases enter the column and the separation of the components is realized under the impetus of the carrier gas. Different gas molecules have different residence times in the column due to differences in physical and chemical properties, thus realizing effective separation.

When the gas passes through the high-precision sensor, it is converted into an electrical signal, which is then converted into a digital signal by A/D. These data are uploaded to the background system in real time via RS485 communication for analysis, storage and display. The whole analyzing process is fully automatic without manual intervention.

How fast is the detection cycle?

The fastest sampling and analyzing period of the system can reach 2 hours once, and the detection period can be set flexibly according to the operational requirements. For important transformers or high-load operation equipment, shorter detection intervals can be set to realize high-frequency monitoring. For stable equipment, the detection cycle can be extended appropriately to save carrier gas consumption.

This flexible detection cycle setting can meet the needs of real-time monitoring, while taking into account the operating costs. The system supports automatic monitoring at regular intervals without manual operation, truly realizing unattended operation.

What level of measurement accuracy can be achieved?

What is the detection range for each gas?

The detection ranges are 2-2000 μL/L for hydrogen, 0.5-1000 μL/L for acetylene, 0.5-1000 μL/L for methane, ethane, and ethylene, 25-5000 μL/L for carbon monoxide, and 25-15,000 μL/L for carbon dioxide.These detection ranges cover the spectrum from normal operation to severe malfunction.

With the optional micro-water monitoring function, the moisture detection range is 1-100 μL/L. These parameter ranges are in line with the requirements of the power industry standards and can meet the monitoring needs of all types of transformers.

What range of measurement error is controlled?

In the low concentration band, the measurement error limit for each gas is the absolute error or relative error of 30%, whichever is greater. For example, for hydrogen in the range of 2-20 μL/L, the error is ±2 μL/L or ±30%. In the high-concentration band, the error limit is standardized as ±30% relative error.

Measurement repeatability requirements are also very strict, under the repeatability conditions, the relative standard deviation RSD of 6 test results must be ≤ 5%. This high accuracy and repeatability ensures the reliability of the monitoring data and provides an accurate basis for fault diagnosis.

What are the components of the system?

What is included in the front-end monitoring device?

The online monitoring device for gas in transformer oil is the core component of the system and is installed near the transformer. The size of the device is 650×500×1300mm, the weight is about 110kg, and it is suitable for outdoor environment by adopting the protective shell with IP55 protection class.

Key components such as oil circulation system, oil and gas separation device, gas chromatography analyzer and data acquisition module are integrated inside the device. It is connected to the transformer through a special purple copper pipe (Φ6×1), and only needs to be connected to the oil inlet pipe and the oil outlet pipe, making the installation simple and convenient.

What are the functions of the backend monitoring system?

The background monitoring and data management system is responsible for receiving, analyzing, storing and displaying data. The system can output various analysis results such as the concentration value of each gas and its concentration spectrogram, three-ratio code, David's triangle diagnostic results, and historical data trend graph.

The data storage time is ≥10 years, and long-term trend analysis can be carried out. The system supports the alarm function of each gas concentration exceeding the limit, when a parameter exceeds the preset threshold, an alarm signal will be issued immediately to remind the operation and maintenance personnel to pay attention to it.

How does the communication method enable remote monitoring?

The system supports a variety of communication methods such as RS485, RJ45, etc. The communication protocol is compatible with MODBUS, IEC61850 and other standards. This means that the monitoring device can be easily and seamlessly connected with the existing SCADA or monitoring platform of the power system to realize remote centralized management.

Adopting N:1 long-distance measurement and control communication mode, multiple monitoring devices can be connected to the same intelligent controller to realize centralized management. The monitoring data can be shared with the internal platform of the power system, which improves the utilization value of the data.

Under what environmental conditions does it work?

How wide is the temperature range?

The system is designed to detect oil temperatures ranging from 0°C to 100°C, and the ambient temperature adaptation range is -40°C to +65°C. This wide temperature range design enables the equipment to operate stably in both the harsh northern winter and the hot southern summer.

Maximum daily temperature differences of up to 25°C are important for equipment installed outdoors. The system is equipped with internal temperature compensation and control devices to ensure that the accuracy of chromatographic analysis is not affected by the ambient temperature. An optional air conditioning system is also available to provide a constant temperature environment for the equipment, depending on the project requirements.

What about other environmental adaptations?

Relative humidity adaptation range is 5%-95%, no condensation or icing inside the product. The range of atmospheric pressure is 80kPa-110kPa, suitable for different altitudes. When installed outdoors, the equipment can withstand severe meteorological conditions such as maximum wind speed of 35m/s, sunshine intensity of 0.1W/cm², and ice cover thickness of 10mm.

The IP55 protection rating means that the device is dust and water resistant to spraying and can operate reliably in outdoor environments for long periods of time. This highly environmentally adaptable design is particularly suitable for outdoor application scenarios such as substations.

For which application scenarios?

Which transformers need to be installed?

The oil chromatography online monitoring system is mainly applicable to substation main transformers and important distribution transformers. For transformers with large capacity, high voltage level and important power supply load, the installation of online monitoring system is especially necessary. Once these equipments fail, the influence range is large and the economic loss is heavy.

Transformers that operate under high loads or are frequently overloaded have high internal temperatures and fast-aging insulation materials, making continuous monitoring even more necessary. For older transformers with a long operating life, online monitoring can detect potential faults in time and extend the service life of the equipment.

What sites need this type of monitoring system the most?

Power users who need to realize condition-based overhaul and online monitoring are the main application targets. Traditional periodic maintenance methods often result in over-maintenance or under-maintenance, while condition-based maintenance can develop maintenance plans based on the actual conditions of the equipment, ensuring both safety and cost reduction.

Critical power supply locations, such as hospitals, data centers, and important industrial users, require extremely high power supply reliability. With the installation of an online monitoring system, problems can be detected at the budding stage of faults and sudden power outages can be avoided.

What role does it play in the power system?

Online monitoring system is an important part of smart grid construction. By connecting the monitoring data to the SCADA system, the digital management of power distribution equipment is realized. The dispatching center can grasp the operation status of transformers in the whole network in real time and carry out unified monitoring and coordinated dispatching.

For distributed power access, microgrid construction and other new power systems, online monitoring technology provides real-time sensing capability of equipment status, which provides a data basis for intelligent operation and optimal control of the power grid.

How is it installed and commissioned?

What is the installation process?

The system supports the installation of the transformer under energized operation without power failure. Connected with the transformer reserved interface through the flange, does not affect the original operation structure. Professional post-measurement engineering supporting inlet and outlet oil valves to ensure the reliability and sealing of the oil circuit connection.

Installation requires the laying of armored flame retardant fully shielded twisted pair cables (4 cores) for data communication, laying power cables to provide AC220V±15%, 50Hz±1Hz working power. According to the needs of the project, may also need to install backstage monitoring screen, air conditioning and other auxiliary equipment.

What accessories do I need to configure?

Standard system configuration includes: 1 set of transformer oil gas online monitoring device, 1 set of communication cables, 1 set of power cables, 1 set of special configuration oil pipe and inlet and outlet oil flange. According to the needs of the project can be equipped with background monitoring computer (including system monitoring software package), background monitoring screen, air conditioning, carrier gas generator.

Carrier gas is a necessary consumable for chromatographic analysis. Under the standard configuration, the carrier gas can be used ≥ 400 times/per cylinder. With the optional carrier gas generator, there is no need to change the gas cylinder regularly, which greatly reduces the running cost and maintenance workload.

What are the routine maintenance tasks?

The system is designed to be highly automated with minimal routine maintenance. The main maintenance items include checking the appearance and operation status of the equipment on a regular basis, checking whether the data is normal, and confirming whether the communication is smooth. If gas cylinders are used for gas supply, it is necessary to pay attention to the remaining amount of carrier gas and replace the cylinders in time.

Regular system self-tests and calibrations are recommended to ensure measurement accuracy. For equipment running for a long time, the maintenance of the column and sensor should be carried out according to the requirements of the maintenance manual. A complete maintenance record will help the equipment to run stably for a long time.

How to choose the right monitoring system?

How do you select a model based on your needs?

Selection begins with clarifying the type and specifications of the monitoring object. Confirm whether the transformer is oil-immersed or not, and understand the capacity, voltage level, operating environment and other basic information of the equipment. For special environments, such as high altitude, high pollution, strong corrosion and other conditions, need to be explained in advance.

Secondly, it is important to define the monitoring needs. Is there a need to monitor all seven gases? Is there a need to add micro-water monitoring? What is the required length of the detection cycle? Does it need to interface with the existing monitoring system? These requirements will affect the configuration and price of the system.

Standard configuration or customized solution?

For routine application scenarios, the standard configuration is sufficient. The standard system contains the basic monitoring device, communication cables, power cables and oil connections, enabling complete monitoring functionality.

If there are special requirements, such as centralized monitoring of multiple transformers, the need for a large screen display, the requirement for a constant temperature environment, the desire to reduce the carrier gas replacement, etc., you can choose the appropriate components. Manufacturers usually provide flexible customization services, according to the actual engineering needs to design the optimal program.

How is the return on investment assessed?

Although the online monitoring system requires some initial investment, its economic benefits are significant in terms of full life cycle costs. The system is able to detect potential faults in a timely manner, avoiding equipment damage and power outage losses due to sudden accidents. These losses often far exceed the investment in the monitoring system.

By realizing condition-based maintenance, unnecessary periodic maintenance and offline tests can be reduced, reducing operation and maintenance costs. At the same time, it improves equipment availability and extends service life. For important users, the indirect benefits brought about by the improvement of power supply reliability are even more incalculable.

Where can I get professional support?

If you have any questions about transformer oil chromatography online monitoring system, or need to know more about the product information and solutions, welcome to contact us through the online consulting system on this site. Our technical team has rich experience in power equipment monitoring, and can provide you with professional selection advice and engineering design services.

As a professional manufacturer of online transformer monitoring system, Inotera has independent R&D capability and perfect production system. We provide one-stop service from product supply, installation and commissioning to after-sales maintenance. Welcome to call 13959168359 consulting product prices and technical solutions, or add WeChat for detailed communication.

We are committed to providing genuine products guarantee, all products are in line with the power industry standards and quality certification requirements. For bulk purchase projects, we also provide on-site technical support and operation training services to ensure smooth commissioning and long-term stable operation of the system.

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The technical parameters and application information described herein are for reference only and do not constitute any product commitment or technical guarantee. The actual product specifications, performance indicators to the equipment nameplate labeling and random technical documents shall prevail. Different models, batches of products may have parameter differences, the specific configuration of the order contract shall prevail.

Users in the selection and use of the process, should be based on the actual application environment, technical requirements and industry norms, consult professional and technical personnel or contact the manufacturer to confirm the applicability of the product. For improper product selection, installation and use of non-standardized, untimely maintenance and other reasons for equipment failure or other losses, this site is not responsible.

Installation, commissioning and maintenance of the product should be carried out by appropriately qualified professionals, in strict compliance with electrical safety regulations and equipment operating instructions. The application cases, technical data and testing indexes mentioned herein are only examples and do not represent the actual results in all application scenarios.

Transformer oil chromatography analysis is a highly specialized technical work, fault diagnosis results need to be combined with equipment operation history, maintenance records and other comprehensive information to judge. Online monitoring system provides data and preliminary diagnostic results are for reference only, the specific treatment measures should be determined by professional and technical personnel in accordance with the actual situation.

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