First, the model of transformer oil
Transformer oil is divided into 10#, 25#, 45#, three models
my country's transformer oil standard is the imitation of the former Soviet Union's Gost standard (ΓΟСТ10121) and IEC296 standard in the 1960s to formulate my country's transformer oil standard GB2536. The product is divided into three grades based on the level of freezing point, which are 10#, 25 # and 45# transformer oil.

Second, the role of transformer oil
Insulation effect: Transformer oil isolates the live parts of different potentials, so as not to form a short circuit. Cooling function: Transformer oil can absorb the heat generated inside the iron core and winding, and then dissipate the heat through the circulation of the oil, thereby ensuring the safe operation of the equipment.

Arc extinguishing function: On the oil circuit breaker and the on-load voltage regulating switch of the transformer, an arc will be generated when the contacts are switched. Transformer oil can decompose a large amount of gas under the high temperature of the arc and generate a large pressure, thereby improving the arc extinguishing performance of the medium and making the arc extinguish quickly.

Third, the physical properties of transformer oil

1.Appearance color and transparency

(1) Color: The new oil is generally light yellow, and the color becomes dark red after oxidation. The color of the oil in operation quickly darkens, indicating that the oil has deteriorated.

(2) Odor: Transformer oil should have no odor, or a little kerosene smell, burnt smell - overheating when the oil is dry; sour smell - serious aging of the oil; acetylene smell - over-electricity in the oil

(3) Transparency: The new oil is transparent in the glass bottle and has blue-violet fluorescence. If the fluorescence and transparency are lost, it means that there is moisture, mechanical impurities and free carbon.

2.The flash point of oil: the mixture formed by the vapor and air generated when the oil is heated flashes when the flame is close, and the temperature is used as the flash point at this time. Flash point is a measure of the degree of evaporation of the oil, the lower the flash point of the oil, the higher its volatility. The lower the volatility, the better, or the higher the flash point, the better. The new oil standard should not be lower than 135℃.

3.Density of transformer oil: 895KG/M3

4.Moisture of transformer oil: Moisture will affect the electrical properties of transformer oil and cause the insulation performance to decline. The less moisture, the better. , the general moisture content is not more than 20mg/L.

Fourth, the chemical properties of transformer oil

1.PH value of water-soluble acid: new oil ≥ 5.4, running oil ≥ 4.2

2.Acid value: The acid value of the transformer oil refers to the value of the organic acid in the oil, and the neutralization acidity of the oil refers to the value after the oxidation test. A common measure of acidity is the mass (mg) of KOH required for neutralization, expressed in mgKOH/g. Highly acidic oils can corrode metal equipment. When there is moisture in the oil, the corrosive property is strong, and the acid value increases year by year, reflecting the deterioration of the oil.

3.New oil: mgKOH/g≯0.03

4.Running oil: mgKOH/g≯0.1

Fifth, the electrical properties of transformer oil
Dielectric strength is an important electrical characteristic index of insulating oil under high voltage electric field.

The voltage of transformer oil when the standard oil cup (electrode distance 2.5mm) breaks down is called "breakdown voltage", and the electric field strength at this time is called "dielectric strength" of insulating oil

Transformer oil breakdown voltage: take the average value of the six breakdown voltages of the standard oil cup
Impurities and moisture can reduce transformer oil insulating properties