Many small household appliances that people use every day have transformers. When the transformer is relatively large, the amount of heat energy it releases is quite considerable. If you do not manage to remove these heat, the temperature of the transformer will become higher and higher, and finally the transformer will be Burned. This requires transformer oil to absorb heat and prevent transformer damage. Today, with Xiao Bian together to understand the role of transformer oil, production process, how do we choose high-quality transformer oil and other related knowledge!
First, the role of transformer oil
1. Insulation
Transformer oil has much higher insulation strength than air. Immersion of insulating material in oil not only increases the dielectric strength but also protects it from moisture.
2. Heat dissipation
Transformer oil has a large specific heat and is often used as a coolant. The heat generated during the operation of the transformer causes the oil near the core and the windings to increase in thermal expansion. Convection through the upper and lower parts of the oil causes the heat to be dissipated through the radiator to ensure normal operation of the transformer.
3. Arc suppression
In the oil circuit breaker and transformer on-load pressure regulating switch, an arc is generated when the contact is switched. Due to the good thermal conductivity of the transformer oil, and under the high temperature of the arc, a large amount of gas can be contacted to generate a large pressure, thereby improving the arc extinguishing performance of the medium and enabling the arc to extinguish quickly.
Second, the production process of transformer oil
1. distillation
According to the differences in crude oil, distillation equipment and operating conditions of the refineries, some manufacturers use atmospheric distillates as the transformer oil fractions, and some manufacturers use vacuum distillates. The principle of crude oil vacuum distillation is based on the difference in the boiling point (or vapor pressure) of each fraction of the crude oil under normal pressure or reduced pressure, multiple partial vaporization and partial condensation in the atmospheric or vacuum fractionation tower, so that the vapor and liquid The mass transfer and heat transfer are fully performed so as to achieve separation from each other.
2. Solvent refining
The principle of solvent purification is that under certain conditions, solvents such as furfural, phenol, and N-methylpyrrolidone have poor ability to dissolve the desired components in the distillate oil, and some non-ideal components in the distillate oil ( Naphthenic acid, gums, asphaltenes, and sulfur, nitrogen, and oxygen compounds have good dissolving power. This solvent's selective dissolving property separates the non-ideal components of the lubricant base oil and improves the base oil. The chemical stability.
3. Acid and alkali refining
The acid-alkali refining process is an old refining process that has gradually been eliminated due to its high cost, low yield, small amount of processing, and large amounts of acid residue pollution. However, in the production of some special products, the process is still used, because the acid-base refining process can obtain more stable products than solvent refining and hydrofinishing processes. The principle of this process is to use concentrated sulfuric acid to easily react with non-ideal components in the oil (such as olefins, colloids, asphaltenes, polar aromatics, etc.) to generate acid slag, which is separated from the oil, thereby achieving the purpose of refining the base oil. .
4. Solvent dewaxing
The ketone-benzene mixture (usually butanone-toluene) is used as a solvent, and the wax can be dissolved at a low temperature without dissolving the wax. The wax is separated from the lubricating oil base oil, so that the base oil can be reduced. The purpose of pour. Since ammonia is widely used in industry today, only base oils with a pour point of -25°C can be produced.
5. Hydrogenation pre-refining
The process is to remove naphthenic acid and sulfur, nitrogen and other impurities in the raw materials under the action of a catalyst and a certain hydrogen partial pressure, and the hydrogenation conditions are relatively eased.
6. White clay supplement refining
The process is characterized by the fact that white clay has a strong porous adsorption capacity and removes trace amounts of solvents, gums, and other impurities contained in the oil after solvent refining or sulfuric acid refining, thereby improving the chemical stability and color of the base oil. White clay supplementation has better denitrification and decolorization, and is sometimes used behind the hydrogenation process to improve the quality of hydrogenated oil.
Third, how to choose a good transformer oil
High quality transformer oil should meet the following requirements
1. Viscosity should be moderate, too large will affect the convection cooling, too small will reduce the flash point.
2. The pressure oil density is as small as possible to facilitate the precipitation of moisture and impurities in the oil.
3. The flash point should be as high as possible and generally should not be lower than 136°C.
4. The freezing point should be as low as possible. The transformer oil is divided according to the freezing point. The lower the freezing point, the transformer oil can be used at a lower temperature.
5. The lower the content of impurities such as alkali, sulfur, and ash, the better so as to avoid corrosion of insulating materials, wires, fuel tanks, etc. as much as possible. For example, Shell's latest launch of Dayana, which contains almost no impurities such as sulfur, is extremely pure.
6. High oxidation resistance: Transformer oil is exposed to air during use and gradually oxidizes. In addition, exposure to high temperatures accelerates oxidation, and the oil after oxidation gradually deteriorates. Therefore, the higher the oxidation resistance of transformer oil is, the better. In contrast, synthetic oils are more stable and resistant to high temperatures.
7. Low acid value: The acid value must be low to reduce the corrosion of the conductance and metal.
The above is a brief introduction for Xiaobian. If you want to know more related information, please continue to pay attention to Qijia Consulting. More exciting consultation, please stay tuned.
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