Transformer Oil

Electrical insulating oils are used in transformer oils, transformers, oil-filled switches, capacitors, and cables, among others. However, the latter two have largely replaced oil with paste-like fillers. Since the amount of oil used in transformers and oil-filled switches is not substantial and should match transformer oil specifications, the term "electrical insulating oil" generally refers to transformer oil.

Transformer oil's composition

Transformer oil is composed of base oil and additives. The base oil of transformer oil is mostly highly refined mineral oil, with the naphthenic base oil from Xinjiang Oilfield being particularly ideal. This type of oil has low wax content, a low pour point, and excellent insulation properties. For transformer oil with high requirements, alkylbenzene, alkyl naphthalene, and silicone oil are also used as base oils. In recent years, transformer oil with a high flash point and biodegradable flame-retardant properties has emerged. To ensure insulation performance, transformer oil should contain as few additives as possible, with only a small amount of antioxidant added, and it is not recommended to use antifoaming agents to lower the pour point.

Transformer Oil Classification and Varieties

Early quality standards for transformer oil in our country were relatively simple, consisting of three grades: 10#, 25#, and 45#, each representing a freezing point of -10°C, -25°C, and -45°C, respectively. Other indicators among the grades were completely or largely identical. With the promulgation of National Standard GB2536-1990, many additional indicators were introduced, such as density and low-temperature viscosity. These included antioxidant properties, surface tension, and water content, and transformer oil meeting this standard was used for 330kV transformers. Another category is ultra-high voltage transformer oil, with the standard SH 0040-1991, intended for 500kV transformers.