It is impossible to ensure reliability and longevity of energy systems without controlling the quality of transformer oil. Recent experience shows that approximately 30% of transformer oil, filled in power transformers, has deteriorated to the point when it becomes a risk factor. This is caused both to natural degradation of oil in operation due to thermal oxidation aging, and contamination with moisture and solid particles. The traditional array of test methods is not quite enough to ensure timely action to prevent the need to replace the oil. The most reliable method of determining the cause for oil aging and selecting the most suitable purification technology is to run a complex test using modern instruments and oil control procedures. Such complex approach to oil quality also allows revealing defects of the equipment in early stages of development.
At present, more advanced methods of oil testing are coming into use, such as highly efficient liquid and gas chromatography, automated particle counting and membrane filtration, infrared spectrometry, electric strength measurement etc.
Electric strength of transformer oil is determined primarily by its purity. Breakdown voltage is significantly affected by dispersed water and solid particles, which conduct electricity.
The adverse effects of moisture on oil operation have been studied well and wide. However, the effects of particles depending on their size, quantity and origin require further research. Such research is nearly impossible without application of modern oil contamination control systems and instruments. Solid particle content can be determined by the weight methods, which are, however, time consuming and difficult, but do not allow to determine particle size and origin. A much better solution is to use automated particle counters in combination with membrane filtration lab. This allows to control purity class, which describes the dispersed phase in the oil, as per ISO4406.