State Identification And Vibration Characteristics Of Power Transformer Winding Abstract

In recent years,with the development and construction of China’s high voltage power grid,the level of power grid has been gradually improved.Transformer,as the pivot equipment of power system operation,is of great significance to the safe and stable operation of power grid.Winding is the core component of power transformer,and its state identification level directly affects the operation and maintenance of transformer.In this paper,a model transformer SGB10-800/6/0.315 is taken as the research object in order to effectively identify the winding faults of in-service transformers.The vibration characteristics of windings are analyzed comprehensively,and the operating state of transformer is detected and identified based on vibration signal analysis.The main research contents of this paper are as follows:(1)Study on vibration characteristics of power transformer windings.The leakage magnetic field and force distribution of transformer windings are analyzed.The frequency characteristics of winding vibration signal were studied by establishing the winding axial vibration model.The influence of nonlinear characteristics of transformer insulation pad on vibration signal is studied.The finite element model was established based on the transformer entity,and the winding magnetic density and axial electric force were calculated by simulation.(2)Winding modal and harmonic response analysis.Based on the coupling theory of electromagnetic field and structure field,the electromagnetic,modal and harmonic response analysis of the vibration characteristics of transformer windings under the condition of steady state operation is carried out.The variation of natural frequency with preload is studied.The modal shapes of windings under normal and loose conditions are calculated.Establish winding typical fault model.The frequency response characteristics of windings under normal and fault conditions were compared to explore the relationship between vibration acceleration and fault types.(3)The vibration signal of transformer surface is analyzed.The common faults of manmade power transformers include winding loosening,insulating pad failure and winding deformation.It is compared with the load test under normal working conditions.The collected vibration signals are analyzed and processed to study the vibration characteristics under different working conditions.It provides a sample for winding state identification and a basis for vibration detection method of transformer winding fault.(4)Research on power transformer winding state identification algorithm.Variational Mode Decomposition(VMD)is used to extract the characteristic information of transformer winding vibration signal.Genetic algorithm is used to optimize support vector learning machine.VMD-SVM winding state identification model is built to realize accurate diagnosis of fault winding.An example is given to verify the algorithm,which shows that the method is effective for the state identification of power transformer windings.