Transformer oil, a light yellow transparent liquid, is a fraction of petroleum. It is mainly used in the transformer to ensure cooling and heat dissipation during operation. So what are the types of transformer oil? What else does the transformer do?
One, the type of transformer oil
Transformer oil is divided into 10#, 25#, 45#, three models
According to my country's transformer oil standard GB2536, the products are classified into three grades based on the freezing point, namely 10#, 25# and 45# transformer oil.
Usually 10# transformer oil is made from paraffin base oil raw material after ketone benzene dewaxing-solvent refining-clay supplement refining, when the freezing point reaches below -10 ℃, it is used as -10 # transformer oil raw material; when intermediate base or paraffin base is used After the raw material is dewaxed by ketone benzene-solvent refining-clay supplement refining, when the freezing point reaches below -25 ℃, it is used as 25# transformer oil; when naphthenic oil is used as the raw material for transformer oil, ketone benzene dewaxing is not necessary The raw material of transformer oil whose freezing point is lower than -45℃ can be directly obtained by atmospheric distillation. Therefore, 45# transformer oil can only be produced from naphthenic oil. When naphthenic oil is used to produce 25# transformer oil, the freezing point of the obtained transformer oil is usually -30℃～-45℃.
The choice of transformer oil has no direct relationship with the capacity of the transformer, but is related to the place where the transformer is used and installed.
1. The freezing point of No. 10 oil is -10 degrees, No. 25 oil is -25 degrees, and No. 45 oil is -45 degrees.
2. Generally: No. 10 is used in temperate zone, No. 25 is used in the north, and No. 45 oil is used in particularly cold areas (such as Tibet).
Second, the main function of transformer oil
Transformer oil has the following main functions:
(1) Insulation
Transformer oil has a much higher dielectric strength than air. The insulating material is immersed in oil, which not only improves the insulation 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 close to the iron core and windings to expand and rise. Through the upper and lower convection of the oil, the heat is dissipated through the radiator to ensure the normal operation of the transformer.
(3) Arc suppression
On the oil circuit breaker and the on-load voltage regulating switch of the transformer, an electric arc will be generated when the contacts are switched. Because the transformer oil has good thermal conductivity, and can separate a large amount of gas under the action of the high temperature of the arc, and generate a large pressure, the arc extinguishing performance of the medium is improved, and the arc is quickly extinguished.
The performance of transformer oil usually has the following requirements:
(1) The density should be as small as possible to facilitate precipitation of moisture and impurities in the oil.
(2) The viscosity should be moderate, too large will affect the convection heat dissipation, too small will reduce the flash point.
(3) The flash point should be as high as possible, and generally should not be lower than 135°C.
(4) The freezing point should be as low as possible.
(5) The lower the content of impurities such as acid, alkali, sulfur, and ash, the better, so as to avoid their corrosion of insulating materials, wires, fuel tanks, etc. as much as possible.
(6) The degree of oxidation should not be too high. The degree of oxidation is usually expressed by acid value, which refers to the amount of potassium hydroxide (mg) required to absorb the free acid in 1 gram of oil.
(7) Stability should not be too low. Stability is usually expressed by the sediment of the acid value test, which represents the oil's ability to resist aging.