In this paper, we offer a simple, intuitive, qualitative method for analyzing in diagnosing transformer oils, which does not require expensive equipment and at the initial stage allows us to determine the degree of oil aging.
This paper presents the results of a research of transformer oil in a visual way. The high information content of the optical radiation scattered and transmitted through the oil is shown. By the color of the radiation, it is possible to determine such characteristics of the oil as acid number, dielectric loss tangent, the presence of colloidal particles, their concentration and size, as well as the presence of aromatic compounds in the oil, changes in their molecular composition and concentration. By the presence of aromatic compounds and colloidal particles, it is possible to visually state the development of thermal and discharge defects in a transformer. This diagnostic system allows to assess the condition of power transformers without shutting them down, make decisions on their further operation without the use of expensive equipment and at the initial stage to identify the changes that are significant and necessary. This is due to the high cost of the transformer, its importance in terms of the reliability of power supply to consumers, the complexity of determining damages and defects at an early stage of development.
During the operation of transformers, the insulating oil is aging, therefore, there is the deterioration of its insulating properties, which is determined by multiple physico-chemical processes. The most dangerous factor, from the point of view of preserving the operational reliability and resource of a power transformer, is the moisture content of the insulation. Most methods for determining moisture content have measurement errors. These errors are largely dependent on impurities that are contained in the oil. The modified Fisher method proposed in the article allows determining the amount of impurities in the oil and the absolute moisture content. Conducted research allows also to determine the composition of impurities, to reveal the relationship between impurities and some parameters of transformer oil.
During operation of the transformer, the oil in it undergoes profound changes usually referred to as aging. The electrical insulating properties of it deteriorate, and sediments accumulate on the active part, which makes it difficult to remove heat. Inhomogeneous solid formations can induce not only the voltage breakdown, but also impair the parameters such as viscosity and other char-acteristics of the oil, which are important for the reliable operation of the power transformers. Aromatic groups initially is present in the transformer oil composition during the operation of the oil, and because of the aging processes, the concentration of the unsaturated cyclic com-pounds increases. The aim of this work is to develop a new method for the determination of the aromatic compounds and colloidal particles. This goal is achieved using a visual inspection of the transformer oil samples in the visible range. The most significant result of the paper is the establishment of a correlation between the acid number of the transformer oil (KOH), the tan-gent of the dielectric loss angle and the type of oil image under the visible light illumination. The significance of the obtained results lies in the fact that the presented method based on the analy-sis of the scattered and transmitted radiation, makes it possible to determine the presence of the aromatic compounds and colloidal particles in the transformer oil, as well as to define their con-centration and size. This method simplifies the analysis of the transformer oil quality, and re-duces the cost of the research, which is an important factor for the electric power industry.
The service life of transformers and, as a consequence, of the electric power systems depends largely on the chemical composition and electrical insulating properties of the oil. In this regard, much attention is paid to the control of physical and chemical indicators and operational properties of transformer oils. The aim of this work is to determine the important diagnostic parameters such as the acid number and the tangent of the dielectric loss angle of the transformer oil based on the measured coordinates of the color of the transformer oil. This goal is achieved by the study of the coordinates of the transformer oils chromaticity. For this purpose, a white light source is used, which is a LED with a pumping line of 450 nm and a maximum radiation in the region of 550-560 nm, with radiation in the range from 400 to 800 nm. Sensors 1, 2, 3 allow determining the chromaticity coordinates of the measured source R, G, B (red, green, blue), due to several receivers having spectral characteristics of sensitivity in the corresponding region of the visible spectrum. The most significant result of the work was the establishment of correlations between the TM chromaticity coordinatesб their acid number and the tangent of the dielectric loss angle of TM. The significance of the results obtained was that the acid number and the tangent of the dielectric loss angle of the transformer oil could be determined by the chromaticity coordinates, and hence, by the color of the oil.
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