Good transformer oil should be clean and transparent liquid, no mechanical impurities precipitate and suspended solids and cotton wool material. If it is polluted and oxidized and produces resin and sediment, the quality of transformer oil will deteriorate, and its color will gradually turn to pale red until it turns into a dark brown liquid.
Transformer oil is a mineral oil obtained through distillation and refining in natural oil. It is a mixture of liquid natural hydrocarbon that is pure, stable, small viscosity, good insulation and good cooling property after refining by acid and alkali.
Commonly known as square shed oil, light yellow transparent liquid, relative density of 0.895. The freezing point is <-45 C, the specific heat capacity is about 0.5 (cal / g * degree), which is mainly composed of three hydrocarbons, the main constituent is naphthenic hydrocarbon (about 80%), the others are aromatic hydrocarbons and alkanes. In our country, the transformer oil has paraffin base oil and naphthenic oil.
The insulation of the oil immersed transformer usually uses a grade a grade insulation material, its oil resistance temperature is 105 C. Specified in GB transformer operating conditions maximum temperature of 40 degrees, so the temperature rise value of the winding is 105-40=65 (C). Non oil circulation cooling, the top oil temperature and winding temperature about 10 DEG C, so the oil temperature is 65-10=55 (c), the top 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.
When the transformer is in trouble, it will also change the color of the oil in general. When the transformer oil is light brown, it is not suitable to use. In addition, transformer oil showed turbid emulsion, color black, dark. The oil of the transformer is cloudy and milky, indicating that the oil is contained in the oil. Color dark, show that the transformer oil insulation aging. The color black, even burnt smell, that the transformer internal fault.
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