Fault Analysis Of Transformer Winding Coil Deformation

Transformers are the "heart" of power transmission.Today,with the increasing capacity of the power grid,the operating environment of transformers is becoming more and more severe.The transformer is prone to winding deformation after being subjected to short-circuit current impact,which is one of the frequent failures of transformers.Due to the cumbersome,time-consuming and labor-intensive inspection process of the hood,it is necessary to use electrical test diagnosis technology to determine in advance whether the winding is deformed after short-circuit impact,and the degree and position of the deformation.Based on the test results,the final decision to return,overhaul or technical transformation of the transformer is made.The main research contents of this article are as follows:(1)The transformer winding and its insulation structure are analyzed in detail,and the various fault types that may occur in the transformer winding are summarized.The leakage magnetic field distribution of the transformer winding and the type and direction of the electric power received by the winding are analyzed,which lays the foundation for the analysis of the next winding deformation detection method.(2)For the low-voltage impedance method,establish the numerical relationship between the transformer short-circuit impedance value and the equivalent area of magnetic flux leakage,and derive the conclusion to determine the winding deformation by the low-voltage impedance method through the formula derivation;for the winding capacitance method,the transformer winding The five sets of data measured by the capacity method are decomposed into the sum of the capacitance between each winding and the winding to the ground,thereby obtaining a method for analyzing the winding deformation using the capacitance test data;for the frequency response analysis method,the frequency response under different types of deformation is obtained through simulation The variation characteristics of the graph,based on which,the principle of judging the winding deformation by comparing the frequency response graphs is summarized,and the abnormal graph characteristics under various interference factors are analyzed.(3)In view of the fact that the current single winding deformation diagnosis method is not perfect and reliable,this paper establishes a comprehensive evaluation system including two levels of evaluation layer and diagnosis layer,based on theextension theory and entropy weight method for multi-index information fusion to determine the winding state level;When the winding is in a severely deformed state level,it enters the fault diagnosis layer,and the low voltage impedance method and the winding capacitance method are used to establish a diagnosis model at the fault diagnosis layer to comprehensively determine the type and position of the winding deformation.(4)For a 220 k V transformer suffering from short-circuit current impact failure,the evaluation layer of this comprehensive evaluation method is used to integrate multiple information of the test results under various test methods,and it is judged that the winding is seriously deformed,and the diagnostic model is used at the fault diagnosis layer It is concluded that the medium-voltage side winding is significantly deformed and sags toward the low-voltage side winding.After the transformer was returned to the factory for hoisting,it was found that the large-area turns of the medium-voltage side winding were close to the direction of the low-voltage winding,which was consistent with the conclusion of the comprehensive evaluation method analysis,which confirmed the correctness of the comprehensive evaluation method.In this paper,the research on the transformer winding deformation diagnosis method is carried out,which is helpful to make a reasonable analysis and judgment on the transformer winding state.The comprehensive evaluation system of transformer winding deformation studied in this paper avoids the misjudgment and misjudgment caused by the conventional single test method,can reduce the failure rate of transformer to a certain extent,and improve the detection efficiency of transformer winding deformation.