Integral Transformers State Assessment Based on Entropy and the Method of Dissolved Gas Analysis

The article discussed the problem of obtaining a reliable operational assessment of the technical condition of transformers in electrical networks and power supply systems. The problem is caused by insufficient sensitivity of mathematical methods and criteria used to assess the condition when describing the dynamics of changes in signs of defects developing in the transformer. This contributes to an increase in diagnostic errors, makes it difficult to choose and reasonably apply adequate operational impacts on equipment. The authors proposed a comprehensive solution based on a combination of methods for processing and analyzing data from diagnostic monitoring of transformers. The initial data are the protocols for the analysis of dissolved gases (DGA) in transformer oil. The solution increases the informative value of signs of developing defects and the reliability of the integrated assessment of the condition of the equipment. This is achieved by combining the entropy method and the method of statistical calculations in determining and ranking the weighting factors of the integral state function (health index) of the transformer. When forming statistical samples of concentrations of diagnostic gases, arrays of DGA data of various representativeness and affiliation are applicable. A range of options is suitable from the results of long-term off-line observations of a group of equipment of the same voltage class with similar operating conditions to a single transformer with a built-in on-line gas monitoring system. One of the advantages of the developed approach is based on the use of entropy as a measure of uncertainty in calculating the weighting factors and changes in the transformer health index over time during the considered interval of its operation. The presence of a calculated example illustrated the results of research, facilitates understanding of the key provisions of the proposed solution and demonstrates its effectiveness in achieving the goal.