Transformer oil is a kind of mineral oil obtained by distillation and refining in natural petroleum. It is a mixture of liquid natural hydrocarbons with pure stability, small viscosity, good insulation and good cooling by acid alkali refining treatment in oil. Commonly known as Fang Peng oil, light yellow transparent liquid, the relative density of 0.895. The solidification point is <-45 C, and the specific heat capacity is about 0.5 (card / gram degree) mainly composed of three hydrocarbons, the main components are naphthenic hydrocarbons (about 80%), and the others are aromatic hydrocarbons and alkanes. In China, transformer oil has paraffin base oil and naphthenic base oil. Paraffin base oil is produced in Daqing, and naphthenic base oil is produced in Karamay, Xinjiang.
A good transformer oil should be a clean and transparent liquid, and no precipitate, mechanical impurities, suspended solids and cotton like substances must be allowed. If it is polluted and oxidized and produces resins and precipitates, the oil of the transformer will deteriorate, and the color will gradually turn to light red until it becomes dark brown. When the transformer fails, it will also change the color of the oil. Generally speaking, when the transformer oil is light brown, it should not be used again. In addition, transformer oil can be characterized by turbidity, blackening and darkening. The oil of the transformer is cloudy and milky, indicating that the oil contains moisture. The color of the oil is dark, indicating that the transformer oil is aging. The oil is black and even smelly, indicating that there is a malfunction inside the transformer.
Why does DL/T572-95 "transformer operation regulation" stipulate that the upper oil temperature of oil immersed transformer should not exceed 95 C?
The insulation of the general oil immersed transformer is made of class a insulating material and its oil temperature is 105 degrees. In the GB, the maximum temperature of the transformer is 40 C, so the temperature rise limit of the winding is 105-40=65 (c). The non top oil circulation cooling, the top oil temperature and the winding oil temperature is about 10 degrees Celsius, so the top layer oil temperature rises to 65-10=55 (c), the top layer oil temperature is 55+40=95 (c). The oil temperature rise in the top layer of the strong oil cycle is generally not more than 40 degrees C.
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