Research on Moisture Content Evaluation Algorithm of Transformer Oil-Paper Insulation System

Abstract

With the increase of the voltage level of the power grid, the role of the transformer in the power grid is becoming more and more important. Due to the transformer perennial outdoor operation condition, external moisture and internal insulation aging will cause the increase of moisture content in the transformer insulation pressboard. The increase in moisture content will greatly reduce the service life of the transformer. The aging degree of oil paper insulation is closely related to its moisture content. It has great significance to calculate the moisture content of the transformer. In order to use dielectric response technique for measuring the moisture content of transformer, the XY model of internal insulation and composite dielectric equivalent model are combined. Meanwhile, the basic data equation of the oil-immersed pressboard is obtained by using the frequency temperature translation method. The evaluation method of moisture content in oil-immersed pressboard based on dielectric loss factor curve can be obtained by continuous cyclic iterative calculation. In order to verify the accuracy of the moisture content assessment method in the oil-impregnated pressboard based on the equivalent model of the transformer, in this paper, a number of different proportional transformer equivalent models are designed in the laboratory. The accelerated aging test were performed at 130°C of the equivalent model of different proportions, in different aging days, the algorithm proposed in this paper and the traditional titration method were used to analyze the different ratios moisture content of transformer equivalent model. The above experiment verifies the accuracy of the proposed algorithm.