Transformer oil due to environmental pollution and oxidation of the resin and sediment, resulting in deterioration, or in the transformer failure, will lead to changes in its appearance. It is the most basic and the most intuitionistic judgement method to judge the operation condition of transformer oil and transformer by using the external shape of oil.
Good transformer oil samples by the glass from the bottom of the transformer in a sampling valve to remove a small amount of sunshine after careful observation, transformer oil well should be clean and transparent, no precipitation, mechanical impurity, suspended matter and cotton like material, color should be pale yellow.
The oil color is brown or brown, and its acid value and water-soluble acid tend to be close to or exceed the international standard attention value. However, the chromatographic analysis has no definite regularity. Under normal circumstances, for deeper color transformer oil, it is necessary to strengthen the chemical supervision of oil testing, shortening the experimental cycle, or can not be said to be suitable for re-use. Transformer oil should be recycled so as to prevent accidents.
Oil oil dark simplified analysis, acid and water soluble acids seriously exceed the standard. In general, the color dark, may be aging oil, no fault of power transformers.
Oil oil black the simplified analysis, the flash point is often near or below the international standard requirements limit value. In chromatography analysis, the increase of hydrogen and acetylene components is also an important feature. In general, black color can be judged as possible transformer internal discharge phenomenon or discharge and overheating, transformer oil for transformer carbonization of solid medium and black, discharge can cause severe burning equipment, and even explosion. Flash point is too low, can also cause transformer fire or even explosion. The color black, and low flash point oil should be special attention.
In the simplified analysis of oil samples, the decrease of breakdown voltage and the increase of hydrogen content are two important characteristics of oil samples. In general, if the oil is cloudy and whitish, it is likely to be caused by moisture in the oil, which can be roughly diagnosed as internal moisture of the transformer oil. Here is a simple way to estimate whether the oil breakdown voltage of the distribution transformer is qualified or not, without the use of an oil dielectric strength tester.
A colorless and transparent after drying the tumbler, a small amount of oil sample is taken out from the transformer at the bottom of the sampling valve, so that the formation of oil column height of 7cm in the glass, in the light at the bottom of the cup will be close to the newspaper, from looking through the oil column, such as can see 6 words, breakdown voltage the oil sample should be more than 25kV. In the operation of 10kV distribution transformer, the breakdown voltage of insulating oil should be no less than 25kV.
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