Transformer Oil Insulation Failure

The liquid-insulated oil-immersed transformer was invented by American scientist Thomson in 1887. It was promoted and applied to power transformers by General Electric Company of the United States in 1892. The liquid insulation referred to here is transformer insulating oil, also known as transformer oil.

Features of oil-immersed transformers:

1. Greatly improved the electrical insulation strength, shortened the insulation distance, and reduced the volume of the equipment;

2. It greatly improves the effective heat transfer and heat dissipation effect of the transformer, increases the allowable current density in the wire, and reduces the weight of the equipment. It dissipates the heat from the running transformer body through the transformer shell and radiator, thereby improving the effective efficiency. cooling down level.

3. Due to the oil-immersed seal, the oxidation degree of some parts and components inside the transformer is reduced, and the service life is prolonged.

Dissolved gas analysis (DGA) of insulating oil is an effective method for early diagnosis of internal faults of oil-filled electrical equipment, and it has been proved by practice. For power transformers with the largest amount of oil filling in electrical equipment, DGA is naturally a very effective fault diagnosis method. The DGA technology of transformer oil is very effective in discovering the latent faults inside the transformer and its development degree, but it is difficult to find some local faults by using electrical test methods.

Chromatographic analysis of dissolved gases in oil is an important method for diagnosing transformer overheating faults. Large-scale power transformers almost use oil to insulate and dissipate heat at present. The actual measurement and research results show that using gas chromatography of dissolved gases in oil, according to the precipitation in the transformer Gas can analyze the latent faults of transformers, especially for overheating, discharge and insulation damage faults, etc., no matter where the fault occurs, it can be well reflected.

Compared with the currently used offline detection method, the biggest advantage of the dissolved gas chromatography in transformer oil is that it does not need to stop the transformer, and the developing internal fault can be identified in the early stage of the transformer failure, and the technology is not affected by the electromagnetic field. Interference detection results are repeatable and reproducible.

The use of gas chromatography to predict the latent fault of the transformer is realized by qualitative and quantitative analysis of the gas dissolved in the transformer oil. Since the electric strength, heat transfer and heat of transformer oil are much better than that of air, at present, electrical equipment at home and abroad, especially large and medium-sized power transformers and reactors, basically adopt oil-immersed structure, and transformer oil plays an important role. Dual function of insulation and heat dissipation. The internal insulation of oil-filled electrical equipment adopts oil-paper insulation structure. The oil-paper insulation structure composed of transformer oil and insulating paper has a high electric strength, which is much higher than that of any material alone. The dielectric strength and dielectric coefficient of the transformer are lower than that of fiber, and it can withstand a large field strength. The transformer oil is divided into a certain number of small oil gaps with insulating paper, which can eliminate the accumulation of fiber impurities in the oil and make it difficult to form "small oil gaps". Bridge", which can make the electric field uniform and improve the electrical strength of the insulation.

For oil-immersed transformers in operation, the transformer oil and organic insulating materials will gradually age and decompose under the action of heat and electricity, producing a small amount of various low-molecular hydrocarbons and gases such as carbon dioxide and carbon monoxide. When there is latent overheating Or when the discharge fails, the speed of these gases will be accelerated. With the development of the fault, the bubbles formed by the decomposed gas are convected and diffused in the oil, and are continuously dissolved in the oil. When the amount of gas produced is greater than the amount dissolved, some gas will enter the gas relay. Since the composition and content of the fault gas are closely related to the type and severity of the fault, regular analysis of the gas dissolved in the transformer oil can detect latent faults inside the transformer early and keep abreast of the development of the fault.

In general, transformer oil contains dissolved gases. Fresh oil contains dissolved gas, and the maximum gas content is about CO: 100μL/L, CO2: 35μL/L, H2: 15μL/L, CH2: 2.5μL/L. There is a small amount of CO and hydrocarbon gases in operation. But when the transformer has an internal fault, the content of dissolved gas in the oil is very different. The characteristic gases and the causes of the transformer internal faults are shown in the table below.

When the transformer oil is overheated, it will decompose hydrogen and methane, ethylene, propylene, etc., and when paper and some insulating materials are overheated, it will also decompose carbon monoxide and carbon dioxide. The following table lists the main gas components released under various faults.

n Indicates the main component; ¨ Indicates the secondary component

Through the above description, perhaps you already have a certain understanding of PURETECH's Transformer Oil Purifiers/Transformer Oil Filtration Machine/Transformer Oil Purifying Machine/Transformer Oil Treatment Plant/Transformer Oil Regeneration Plant. If you have determined the model, flow, power supply, configuration, etc. you need, please inform our sales team. We will prepare a quotation and detailed technical information for you as soon as possible for your further reference.

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