Electrical performance

Breakdown voltage: This is a key indicator for measuring the insulation strength of transformer oil. Under standard test conditions, the breakdown voltage of high-quality transformer oil is usually ≥ 40 kV (2.5mm electrode gap). A higher breakdown voltage can ensure that transformers effectively isolate electrical components in high voltage environments, preventing the occurrence of discharge and short circuit faults. For example, transformers in ultra-high voltage transmission lines have stricter requirements for breakdown voltage. Only transformer oil with a breakdown voltage that meets the standard can ensure stable power transmission.

Dielectric loss factor (tan δ): This parameter reflects the energy loss of transformer oil under alternating electric fields. Generally speaking, at 90 ℃, the dielectric loss factor of transformer oil should be ≤ 0.5%. Low dielectric loss factor means that the energy loss of the oil during operation is low, which can effectively improve the operating efficiency of the transformer, reduce heating and aging. If the dielectric loss factor is too high, it will cause the oil temperature of the transformer to rise, accelerate the aging of the oil, and reduce the service life of the equipment.

Volume resistivity: It reflects the insulation resistance characteristics of transformer oil. At 90 ℃, the volume resistivity of transformer oil is ≥ 1 × 10 ΩΩ· m. The high volume resistivity ensures that the transformer oil maintains good insulation performance during long-term operation, prevents current leakage, and ensures the safe operation of power equipment.

Chemical properties

Acid value: The acid value of new oil should be ≤ 0.03 mgKOH/g, and the oil in operation is generally controlled at ≤ 0.1 mgKOH/g. Acid value is an important indicator reflecting the degree of oxidation of oil products. The lower the acid value, the lower the degree of oxidation of the oil product and the less corrosive it is to the metal components of transformers. As the operating time of the transformer increases, the oil will gradually oxidize and the acid value will rise. Therefore, it is necessary to regularly monitor the acid value and take timely measures, such as adding antioxidants or replacing the oil.

Moisture content: Moisture poses a great threat to the insulation performance of transformer oil. The moisture content of transformer oil is usually ≤ 15 ppm (parts per million concentration) when it leaves the factory. During operation, strict sealing and drying measures must be taken to consistently control the moisture content at a low level. Excessive moisture can lower the breakdown voltage of the oil, increase the dielectric loss factor, and even cause equipment failure. For example, transformers operating in humid environments require close attention to the moisture content in the oil. By installing equipment such as dryers, the risk of moisture entering the oil can be reduced.

Sulfur content: In order to meet environmental requirements and reduce equipment corrosion, the sulfur content of transformer oil is generally ≤ 0.2% (mass fraction). Low sulfur formula transformer oil can effectively reduce the corrosive substances generated by sulfur-containing compounds during the operation of transformers, extend the service life of equipment, and also comply with environmental regulations on the emission of harmful substances.

Physical performance

Density: At 20 ℃, the density of transformer oil is generally between 0.85-0.89 g/cm ³. The appropriate density ensures stable convection and heat dissipation of the oil during the operation of the transformer, maintaining the normal operating temperature of the equipment. If the density is abnormal, it may cause local overheating, affecting the performance and lifespan of the transformer.

Tilt point: Tilt point is used to measure the low-temperature fluidity of oil products. In general, the pour point of transformer oil is ≤ -20 ℃. For transformers used in cold regions, the pour point of the transformer oil used can be as low as -30 ℃ or even lower. In low-temperature environments, only transformer oil with a sufficiently low pour point can maintain good fluidity, ensure timely heat transfer inside the transformer, and avoid equipment failure caused by oil solidification.

Flash point: The flash point reflects the volatility and safety of the oil product. The flash point of transformer oil is ≥ 140 ℃, and high-quality products can reach above 160 ℃. High flash point means that when high temperatures are generated inside the transformer due to faults, the oil is not easily evaporated and burned, greatly reducing the risk of fire and ensuring the safe operation of power equipment.