There are usually the following requirements for the performance of transformer oil:

（1）变压器油密度尽量小，以便于油中水分和杂质沉淀。

(1) The density of transformer oil should be as small as possible to facilitate the precipitation of moisture and impurities in the oil.

（2）粘度要适中，太大会影响对流散热，太小又会降低闪点。

(2) The viscosity should be moderate, too large will affect the convective heat dissipation, too small will reduce the flash point.

（3）闪点应尽量高，一般不应低于136℃。

(3) The flash point should be as high as possible, generally not lower than 136 ℃.
           

（4）凝固点应尽量低。

(4) The freezing point should be as low as possible.

（5）酸、碱、硫、灰分等杂质含量越低越好，以尽量避免它们对绝缘材料、导线、油箱等的腐蚀。

(5) The lower the content of impurities such as acid, alkali, sulfur and ash, the better, so as to avoid their corrosion to insulating materials, wires, oil tanks, etc.

（6）氧化程度不能太高。氧化程度通常用酸价表示，它指吸收1克油中的游离酸所需的氢氧化钾量（毫克）。

(6) The degree of oxidation should not be too high. The degree of oxidation is usually expressed as acid value, which refers to the amount of potassium hydroxide (mg) needed to absorb the free acid in 1 gram of oil.

（7）安定度不应太低，安定度通常用酸价试验的沉淀物表示，它代表油抗老化的能力。

(7) the stability should not be too low. The stability is usually expressed by acid value test precipitates. It represents the ability of oil to resist aging.