A Study On The Nonlinear Mechanical Characteristics Of Transformer Pressboard

Accurate monitoring of transformer fault is the guarantee of stable operation of power transformer and the basis of reliable power supply in power system.Vibration analysis method based on winding vibration signal is a common transformer fault detection method.The research shows that the state of pressboard will affect the vibration of transformer winding,and understanding its mechanical characteristics is helpful for the study of vibration analysis method.At present,the research on nonlinear mechanical characteristics of pressboard mostly focuses on static test,and the change of mechanical characteristics under dynamic response has not been fully studied.Based on this,the dynamic hysteresis model fitting and parameter identification algorithm of pressboard under different vibration frequencies,preloads and vibration forces are proposed.The main contents are as follows :1 The experimental mechanical device and measurement scheme are designed to realize adjustable frequency,adjustable vibration force and adjustable preload,while ensuring the stable operation of the device and synchronous real-time measurement of strain,acceleration and stress signals.The measurement results meet the experimental requirements.2 The Bouc-Wen model based on nonlinear least squares method is established to realize the quasi-merge analysis of hysteretic loops under different vibration frequencies,preloads and vibration forces.Based on the hysteresis loop fitting results,the damping and stiffness are calculated,and the parameters of Rayleigh damping are further identified.The model can effectively fit the measured data and accurately track the state change.3 The extended Kalman filter model based on the Newmark-? method and Rayleigh damping is established to realize the equivalent stiffness identification under different vibration frequencies,preloads and vibration forces.The model can effectively identify the parameters and accurately reflect the stiffness change trend.There are significant differences in stiffness under different frequency excitations.The results show that the mechanical characteristics of the pressboard are significantly different under different vibration frequencies,preloads and vibration forces.The pressboard has better nonlinear hysteresis characteristics,stronger seismic capacity and more stable structure at 100 Hz.The pressboard is more sensitive to the change of excitation at 50 Hz,and the structure is more vulnerable to damage.