Insulating oil (also known as transformer oil), good insulating oil is clean and transparent, and the color is light yellow. Due to the influence of resins and sediments produced by contamination and oxidation, the oil quality of insulating oil deteriorates, and the color will gradually become darker. When the transformer is faulty, it will also change the color of the oil. In addition to testing the quality of insulating oil through the insulating oil dielectric strength tester, the quality of insulating oil can also be roughly distinguished by appearance.
1. Turbid and whitish oil samples: The increase of H2 gas content and the decrease of breakdown voltage are two important characteristics of turbid and whitish oil samples. Under normal circumstances, if the oil sample is cloudy and whitish, it is likely to be caused by the presence of water in the oil.
2. The color of the oil sample is brown or brown: its acid value and water-soluble acid are often close to or exceed the national standard weight value. However, its chromatographic analysis has no certain regularity. In general, for transformer oil with darker color, the chemical supervision test of the oil should be strengthened.
3. The oil color of the oil sample is dark: according to the content of its gas components and the three-ratio method, the fault type is a normal aging phenomenon, and there is no fault inside the transformer. Both the acid value and the water-soluble acid in the simplified analysis were seriously exceeded. Under normal circumstances, if the oil color is dark, it may be the aging phenomenon of the oil.
4. The oil color of the oil sample is black: the increase of its H2 and C2H2 components is an important feature. Its content can be as high as several thousand µl/l, and the transformer turns black due to carbonization.