What are the selection criteria for oil-immersed transformer oil?
Time：2025-01-4 Auther：ZTelec-www.ztelectransformer.com
Oil-immersed transformers are transformers that use insulating oil as a cooling and insulating medium. Its basic working principle is to convert AC power of one voltage level into AC power of another voltage level of the same frequency through electromagnetic induction. The core components of oil-immersed transformers include iron core, coils and insulation materials, which are usually installed in a welded steel tank filled with insulating oil.
Specifications of special oil for oil-immersed transformers
Special oil for oil-immersed transformers is generally divided into multiple specifications, such as No. 10, No. 25, No. 35, etc. And its number represents the quality and performance of the oil. The higher the specification, the better the oil quality and the more stable the performance, but the price will also increase accordingly.
When selecting oil, the specifications of the oil should be determined according to the requirements of the rated voltage, capacity and use environment of the transformer to ensure the stable and efficient operation of the transformer.
What are the selection criteria for oil-immersed transformer oil?
Freezing point: The freezing point of transformer oil is an important indicator. The freezing point of No. 25 oil is minus 25 degrees Celsius, which is suitable for use in general low temperature environments; while the freezing point of No. 45 oil is lower, reaching minus 45 degrees Celsius, which is suitable for extreme low temperature conditions.
Viscosity: Appropriate viscosity can provide good lubrication and ensure that the heat inside the motor is effectively dissipated. Transformer oil with ISO VG32 viscosity is widely recommended for its good lubrication and cooling properties.
Flash point: The flash point is the lowest temperature at which the vapor and air mixture of transformer oil can be ignited under specific conditions. The higher the flash point, the lower the volatility of the oil and the better the safety. The flash point should generally not be lower than 136℃ to ensure the safety of the oil at high temperatures.
Density: The density of transformer oil should be as small as possible to facilitate the precipitation of moisture and impurities in the oil. A smaller density helps to reduce the content of impurities in the oil and improve the purity and insulation performance of the oil.
Acid value: The acid value should be as low as possible. It should usually not exceed 0.03 mgKOH/g to reduce corrosion to the equipment.
Moisture content: The moisture content should be as low as possible and should not exceed a certain limit (such as mg/kg) to ensure the electrical performance and stability of the oil.
Breakdown voltage: The breakdown voltage is the voltage value when the transformer oil breaks down under the action of an electric field. The breakdown voltage should be higher than a certain value (such as 35kV) to ensure the electrical performance of the oil.
Stability: Stability indicates the ability of the oil to resist aging, which is usually measured by the sediment of the acid value test. The stability should not be too low.
Impurity content: The content of impurities such as acid, alkali, sulfur, and ash should be as low as possible to avoid corrosion to insulation materials, wires, oil tanks, etc.
Degree of oxidation: The degree of oxidation cannot be too high to ensure the long-term performance of the oil.
The selection criteria for oil-immersed transformer oil involve many aspects. When selecting transformer oil, these factors should be considered comprehensively and the appropriate oil type and specifications should be determined according to the design requirements and operating environment of the transformer. At the same time, attention should also be paid to regular inspection and maintenance of transformer oil to ensure its long-term stable performance and service life.
