Study on Electrically Excited Winding Vibration Frequency Response Under Various Clamping Pressures

Transformer winding vibration frequency response characteristics is the direct reflection of winding mechanical condition. Studying transformer winding vibration frequency response characteristics is very meaningful for winding modal analysis and can be utilized for winding mechanical fault diagnosis. This paper uses a single winding to perform electrically excited vibration frequency response experimentation whose platform mainly consists of a harmonic source and its control system. The electrical excitation is a constant current whose frequency sweeps from 50Hz to 500Hz. Winding axial vibration response of different discs are measured. Furthermore, in order to study the influence of various clamping pressures on winding vibration frequency response, a special device is designed to change and measure the clamping pressure on the winding. Vibration Frequency Response Function (VFRF) is used to reflect winding vibration frequency response characteristics. The result shows that winding VFRFs are similar under various amplitude of excitation current which verifies the winding structure can approximately be regarded as linear system. The variation tendency of natural frequency is difficult to abstract from the VFRF due to too many modal numbers. Winding VFRFs under various clamping pressures are different and Coefficient Correlation (CC) is brought up to evaluate the variation. CC decreases with the clamping pressure variation increasing and measure location has a large influence on the sensitivity of CC when it is used as an indicator to evaluate the change of winding pressure clamping. Studying electrically excited winding vibration frequency response under different clamping pressures is meaningful in winding looseness diagnosis.