Mechanical Deformation Identification of Transformer Winding under Multiple Short-Circuit Impacts Based on Vibration Deviation and Weighted Entropy
Lü Fangcheng1,2, Wang Xinyu1,2, Wang Ping1, Gao Shuguo3, Geng Jianghai1
1. Hebei Provincial Key Laboratory of Power Transmission Equipment Security Defense North China Electric Power University Baoding 071003 China; 2. State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Beijing 102206 China; 3. State Grid Hebei Electric Power Research Institute Shijiazhuang 050021 China
Abstract:The accumulative effect of transformer windings under multiple short-circuit impulse will eventually lead to sudden instability failure, so it is essential to study the mechanical deformation of windings under multiple short-circuit. Firstly, the multiple short-circuit tests under various working conditions on an 110 kV full-scale transformer were carried out, and the transient vibration acceleration signals during the short-circuit process and the steady-state values of the axial pressure of the windings before and after the multiple short-circuit were collected, the time-frequency characteristics of which were analyzed. According to the linear relationship between the vibration acceleration and the square of the current, the deviation trend between the measured value and the reference value is obtained, and the time domain characteristic of the vibration deviation is proposed. Then, combined with the winding axial vibration dynamics model, the relation between axial pressure, vibration deviation and deformation type is determined. Under HV-MV B-phase multiple short-circuit tests, the effective value of the vibration acceleration gradually produced a positive deviation. In the last test, the deviation value was 21.5 m/s2, and the corresponding axial pressure was reduced from 3.15 t to 2.77 t. Similarly, under MV-LV A-phase multiple short-circuit tests, the vibration acceleration first produced a positive deviation of 2.37 m/s2 in the second test, and then gradually decreased. In the last test, it showed a negative deviation of -3.43 m/s2, and the corresponding axial pressure decreased from 4.29 t to 4.17 t and then increased to 4.43 t. According to the positive or negative deviation of the vibration acceleration under multiple-short circuit, the axial deformation type identification of the winding can be realized. When the vibration acceleration presents a positive deviation, the axial pressure decreases. The deformation form of the winding on the short circuit side is the outwards expansion of the end shaft. When the vibration acceleration presents a negative deviation, the axial pressure increases. At this time, the deformation form of the winding on the short circuit side is the inward concave compression of the end shaft. And the frequency domain characteristics of vibration weighted spectral entropy are proposed. For the HV-MV B-phase short-circuit condition, and M-L C-phase short circuit condition, the weighted entropy increases from 3.803 to 4.1, and 3.386 to 5.295 respectively. The weighted time-frequency spectrum entropy can be used as an effective frequency domain feature to identify whether the winding deformation occurs. The above result shows that when the mechanical degradation of winding caused by accumulative effect is occurred, the vibration acceleration will deviate the reference value of the undeformed state of winding, and the weighted time-frequency spectrum entropy will increase. Finally, a winding deformation identification method based on the joint analysis of vibration deviation and weighted time-frequency spectrum entropy is proposed and verified. This combined analysis method can avoid the problem that when the axial deformation type changes or the extend of deformation is small the characteristic quantity does not change significantly. Compared with the traditional impedance method, it is able to detect the mechanical degradation of winding earlier, which is more effectively to reflect the impact of the accumulative effect. The vibration signal is easy to collect, and the normal operation of the transformer will not be disturbed during collecting the signal, so as to realize the effective and reliable monitoring of the mechanical stability of the winding.
律方成, 汪鑫宇, 王平, 高树国, 耿江海. 基于振动偏离及加权熵的多次短路冲击下变压器绕组机械形变辨识[J]. 电工技术学报, 2023, 38(11): 3022-3032.
Lü Fangcheng, Wang Xinyu, Wang Ping, Gao Shuguo, Geng Jianghai. Mechanical Deformation Identification of Transformer Winding under Multiple Short-Circuit Impacts Based on Vibration Deviation and Weighted Entropy. Transactions of China Electrotechnical Society, 2023, 38(11): 3022-3032.
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