Vibration mechanism and influence factors in power transformers

For an oil-immersed transformer core and pancake windings, the transformer vibration parameters are sought out and the vibration superposition is analyzed. The vibration monitoring system with piezoelectric vibration acceleration sensors is constructed and a series of experiments for the influence factors of the transformer vibration, such as current, power factor, unbalance factor and oil temperature, are conducted to investigate the vibration characteristics under different working conditions. It is found that the fundamental component of transformer tank under the greatest tapping is higher than that under principal tapping, transformer tank does not vibrate at linear superposition frequencies of core and windings; the fundamental component of transformer tank grows with the power factor; frequency components of 50 Hz, 150 Hz and 250 Hz appear in the vibration signals of power transformer due to the asymmetry. The experiments show that the fundamental component of the transformer vibration signal increases linearly with the oil temperature; temperature coefficient stays within 0.005-0.035 and does not depend upon the transformer capacity.