Research On Online Monitoring Of Transformer Winding Deformation Using SFRA Method

As an important equipment in the power system, the safe operation of the transformer is of great significance to ensure the reliability of the grid. In recent years, the number of transformer damage accidents caused by windings directly or indirectly remains large. Since the the winding deformation diagnostic tools still remain in the the offline testing phase, the online monitoring of winding deformation is meaningful to improve the safety and reliability of transformer operation.The possible kinds of distortion and the advantages and disadvantages of the offline and online detection methods are analyzed in the dissertation. And with these analysis, the frequency response analysis is chosen to be an adequate method to carry out online detecting.The lumped parameter model of power transformer is built to simulate the common axial and radial deformation. The results show that:1.With the intensification of the degree of deformation, the frequency shift and change of amplitude of resonant point became clear;2.As the frequency increase, the frequency response curve under different deformation degree become close to each other;3.Compared with partial deformation, the frequency response curve of overall deformation has the characteristics of more significant frequency shift and the decrease of amplitude variation;4. Compared with radial deformation, axial deformation has wider distribution of resonant points. Furthermore, the impact of transmission line and load to the frequency response curve is also analyzed.According to the results of the simulation, the basic parameters of detection device of SFRA method such as power requirements are determined. The feasibility of applying excitation source signal to the transformer and other factors that influence the safe operation of detection device are studied, which become the design criteria of the related parts of detecting device such as filter module and high frequency current transformer. In the design of power pulse source based on MOSFET, the power loss of the driven circuit is discussed. And signal acquisition module based on FPGA finish the data sample and communication with host computer module, whose operation system is WinCE. The whole is an integration of power pulse source, signal acquisition module and data analysis part.At last, the offline and online experiments on a380V/35000V transformer are made. And the offline results, online results with and without load are compared with each other while the deformation is designed using parallel capacitance.