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Study on the Influence of Temperature on Transformer Core Vibration

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. In this paper, core vibration characteristics and the influence of operating temperature were studied. 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 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 approximate linear relationship below 70°C with growth rates of 0.11-0.37mm∙s^(−2)/ °C, 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°C. 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.