Description
Transformer vibration is closely related to winding and core condition. Vibration-based transformer condition monitoring and diagnosis technique has been widely used recently, and core vibration occupies a large proportion in the total vibration of operating power transformer. Besides the fluctuant operating voltage, temperature of core silicon steel is considered as the major influential factor on core vibration characteristics. It is necessary to study the influence of temperature on transformer core vibration to improve the accuracy of vibration-based fault diagnosis. In this paper, core vibration characteristics under different temperature was studied. Core temperature was controlled by a temperature chamber. The vibration signals of different positions of core surface, including yokes, limbs and joints, were obtained by piezoelectric vibration sensors under rated excitation voltage, and fast Fourier transform was applied to extract the spectrum and feature parameters which can be used to monitor the mechanical condition. Vibration spectrum under different temperatures were plotted and analyzed. The result shows that with the rising of temperature, the total power of core vibration decreases to the minimum at 48℃ first and then increases. Temperature has a significant influence on the magnetostriction of silicon steel. Vibration amplitude of fundamental frequency increases with the increase of temperature within the working temperature range of the transformer core, and it shows a good linear relationship below 70℃ with growth rates of 0.11-0.37mm∙s^(-2)/℃, which is different from the measuring points on the core surface. The growth rate decreases and shows a saturation tendency of vibration amplitude occurs over 70℃. Temperature-vibration correction curve was proposed to correct the vibration response of transformer core under different temperature and improve the accuracy of vibration-based winding and core condition monitoring and fault diagnosis.
