Transformer oil spectral monitoring principle
Date: October 25, 2025 17:51:51
What is Transformer Oil Spectroscopy Online Monitoring?
Transformer oil spectroscopy online monitoringIt is an advanced, non-contact analytical technique based on the principle of interaction between matter and light. It is fundamentally different from traditional monitoring methods based on chemical reactions or chromatographic separation. The technology accurately identifies the various substances dissolved in the oil by emitting a beam of light of a specific wavelength into a sample of transformer oil or a gas separated from the oil and analyzing the changes (e.g., absorption, scattering) that occur when the light passes through the sample.Fault Characteristic GasesThe "molecular fingerprints" of the products were quantified and their concentrations were calculated.
The core of this technology lies in the fact that each gas molecule (e.g., H₂, CH₄, C₂H₂, etc.) has its own unique spectral characteristics, just like a human fingerprint. By interpreting this spectral information, the system is able to realize the latent faults (e.g. overheating, discharge) inside the transformerReal-time online diagnosticsrespond in singingearly warningIt is a cutting-edge technology that enables transformer condition-based maintenance (CBM) and predictive maintenance (PdM).
Why spectral monitoring of transformer oil?
Dissolved gas analysis (DGA) of transformer oil is the most effective and proven means of determining the internal operating conditions of a transformer. When overheating or discharge faults occur inside the transformer, the insulating oil and insulating paper will decompose and produce a variety of characteristic gases. By analyzing the components and content of these gases, the type and severity of the fault can be accurately determined.
Limitations of traditional methods
Traditional DGAs rely heavily on laboratoryGas Chromatography (GC). Despite its high accuracy, there are obvious drawbacks:
- non-real time: Usually requires periodic sampling for inspection, with long monitoring periods (months or even a year) that do not capture rapidly developing faults.
- High maintenance costs: Online gas chromatographs are complex and require regular replacement of carrier gases (e.g., high-purity argon), calibration gases, etc.disposablesand requires professional maintenance.
- Reliability issues:: Complex mechanical components (e.g., valves, columns) present a risk of failure during long-term operation.
Spectral monitoring technology was created to overcome these drawbacks by providing a consumable-free, low-maintenance, truly real-time monitoring solution.
Core monitoring principle: "Dialogue" between light and gas
Transformer oil spectroscopy monitoring systems usually start by extracting the dissolved gases from the oil by means of a highly efficient gas separation membrane, which is then fed into an optical measurement unit. Mainstream spectral analysis techniques include the following:
1. Non-dispersive infrared spectroscopy (NDIR) and Fourier transform infrared spectroscopy (FTIR)
This is the most widely used spectroscopic technique and is particularly suitable for the detection of hydrocarbon gases and CO, CO₂. The principle is based onmolecular vibrational absorption spectroscopyThe
Working Principle
When mid-infrared light passes through a gas sample, if the frequency of the light matches the vibrational frequency of the gas molecules, the molecules absorb the light energy at that frequency, producing an apparentabsorption peak. Based onLambert-Beer LawThe intensity of absorption is proportional to the concentration of the gas.NDIRThe technology uses narrow-band filters for specific gases, which are simple and stable. WhileFTIRInstead, it can simultaneously measure a wide infrared spectral range, can analyze multiple gas components at one time, and is more resistant to cross-interference.
2. Photoacoustic Spectroscopy (PAS - Photoacoustic Spectroscopy)
This is an extremely sensitive spectroscopic technique that is particularly well suited for the trace detection of critical fault gases such as acetylene (C₂H₂).
Working Principle
The principle of PAS is very clever:
- A modulated laser beam of a specific wavelength is directed at the gas sample.
- The target gas molecules absorb light energy and increase in temperature, undergoing periodic expansion and contraction in volume.
- This periodic rise and fall creates a weak acoustic wave (pressure wave) within the confined chamber.
- A highly sensitive microphone (microphone) detects the intensity of this sound wave, which is directly proportional to the gas concentration.
Because it directly detects the sound waves generated by absorbed energy rather than weak light signal changes, its signal-to-noise ratio is extremely high, and the detection limit can reachppb (parts per billion) level, which is critical for detecting trace amounts of C₂H₂ in the early stages of a fault.
3. Raman Spectroscopy - a powerful tool for hydrogen monitoring
For symmetrical molecules like hydrogen (H₂), which have no infrared absorption, the NDIR/FTIR method is powerless. Raman spectroscopy provides the perfect solution.
Working Principle
When a strong laser hits a hydrogen molecule, most of the light is scattered elastically (with no change in frequency), but a very small fraction is scattered inelastically, and the frequency of the scattered light undergoes a small change, an amount known as theRaman shift, is the characteristic fingerprint of the hydrogen molecule. By detecting the intensity of this specific Raman scattering signal, it is possible to accurately measure thehydrogen concentrationThe
From spectra to diagnostics: interpretation and application of data
The direct output of the spectral monitoring device is a spectrogram containing information on the individual absorption peaks. A built-in intelligent algorithm interprets this spectral data in real time into concentration values (in ppm) for the various gases. However, this is only the first step. More importantly, the system automatically applies this concentration data to internationally recognized troubleshooting methods, for example:
- Duval Triangle
- Rogers Ratio Method
- Key Gas Method
Using these algorithms, the system can automatically give clear diagnostic conclusions, such as "low temperature overheating", "high energy arc discharge" or "normal equipment", and trend alarms according to the growth rate of gas concentration. The system automatically gives clear diagnostic conclusions such as "low temperature overheating", "high energy arc discharge" or "equipment normal", as well as trend alarms based on the rate of increase in gas concentration.
Advantages of spectral monitoring technology
- Real-time and Continuity: Minute-by-minute data refreshing, 24/7 non-stop monitoring, never miss any sign of fault development.
- No consumables and low maintenance: The entire measurement process is free of any chemical reaction and gas consumption, eliminating the need to replace carrier and calibration gases and significantly reducing O&M costs.
- long term stability: Long-life core optics and calibration cycles of up to several years ensure accurate and reliable long-term monitoring data.
- High sensitivity and accuracy:: PAS technology, in particular, has extremely low detection limits for critical gases, enabling true early warning of failures.
- Simultaneous multi-component analysis: Technologies such as FTIR can analyze multiple gases simultaneously in a single measurement cycle, providing a comprehensive picture of the fault.
Why choose Inotera's transformer oil spectroscopy solution?
INNOTD (Fuzhou) Sales Limited (INNOTD) Integrating the world's leading spectral analysis technology, we provide customers with a stable, accurate and intelligent online monitoring system for dissolved gases in transformer oil.
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- Advanced technology integration: Our systems are optimized for the properties of different gases with a combination ofPhotoacoustic Spectroscopy (PAS) respond in singingNon-Dispersive Infrared (NDIR) A wide range of spectroscopic techniques, including H₂, C₂H₂, and others, ensure highly accurate measurements of all nine critical fault gases including H₂, C₂H₂ and H₂.
- High precision optics and algorithms: We use long-life, high-stability optics and are equipped with self-developedIntelligent Diagnostic Algorithmand temperature and pressure compensation models to ensure that accurate diagnostic results are provided under a variety of complex operating conditions.
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- All-in-one platform integration: Our DGA monitoring device can be seamlessly integrated into Inotera's comprehensive online monitoring platform, realizing the data with partial discharge, micro-water, core grounding current and so on.Multi-information fusion analysisIt provides the most comprehensive assessment of transformer health and fault investigation.
- Reliability and long-term stabilityOur products are specially designed for the strong electromagnetic environment of substation, with excellent anti-interference ability and long-term operation stability, which is the ideal choice for replacing the traditional on-line chromatograph and realizing the less manned or unattended substation.
By choosing Inotera, you are choosing to guard your core power assets with the wisdom of light.
The content of this article is only a general technical science and does not represent the performance and specifications of any specific product of our company. For detailed product information, solutions and quotations, please be sure to contact us for...].
